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Research Article
Study on hydraulic turbine system identification and predictive control based on GASA-BPNN
Xiao-ping Jiang, Zi-ting Wang, Hong Zhu, and Wen-shuai Wang
Available online 13 April 2021, https://doi.org/10.1007/s12613-021-2290-6
[Abstract](41) [PDF 1492KB](15)
Abstract:
Based on the characteristics of nonlinearity, multi-case and multi-disturbance, it is difficult to establish an accurate parameter model on the hydraulic turbine system which is limited by the degree of fitting between parametric model and actual model, and the design of control algorithm has a certain degree of limitation. Aiming at the modeling and control problems of hydraulic turbine system, this paper proposes hydraulic turbine system identification and predictive control based on Genetic Algorithm-Simulate Anneal and Back Propagation Neural Network (GASA-BPNN),the output value predicted by GASA-BPNN model is fed back to the nonlinear optimizer to output the control quantity. The results show that the output speed of the traditional control system increases greatly and the speed of regulation is slow, while the speed of GASA-BPNN predictive control system increases little and the regulation speed is obviously faster than that of the traditional control system. Compared with the output response of the traditional control of the hydraulic turbine governing system, the neural network predictive controller used in this paper has better effect and stronger robustness, solves the problem of poor generalization ability and identification accuracy of the turbine system under variable conditions, and achieves better control effect.
Research Article
Anion-immobilized solid composite electrolytes based on metal-organic frameworks and superacid ZrO2 fillers for high-performance all solid-state lithium metal batteries
Tao Wei, Zao-hong Zhang, Qi Zhang, Jia-hao Lu, Qi-ming Xiong, Feng-yue Wang, Xin-ping Zhou, Wen-jia Zhao, and Xiang-yun Qiu
Available online 13 April 2021, https://doi.org/10.1007/s12613-021-2289-z
[Abstract](33) [PDF 1452KB](9)
Abstract:
Anion-immobilized solid composite electrolytes (SCEs) are important to restrain the propagation of lithium dendrites for all solid-state lithium metal batteries (ASSLMBs). Herein, a novel SCEs based on metal-organic frameworks (MOFs, UiO-66-NH2) and superacid ZrO2 (S-ZrO2) fillers are proposed, and the samples were characterized by XRD, SEM, EDS, TGA and some other electrochemical measurements. The -NH2 groups of UiO-66-NH2 combines with F atoms of PVDF-HFP chains by hydrogen bonds, leading to a high electrochemical stability window of 5 V. Owing to the incorporation of UiO-66-NH2 and S-ZrO2 in PVDF-HFP polymer, the open metal sites of MOFs and acid surfaces of S-ZrO2 can immobilize anions by strong Lewis acid-base interaction, which enhances the effect of immobilization anions, achieving a high Li-ion transference number (t(+)) of 0.72, and acquiring a high ionic conductivity of 1.05×10-4 S cm-1 at 60℃. The symmetrical Li/Li cells with the anion-immobilized SCEs may steadily operate for over 600 h at 0.05 mA cm-2 without the short-circuit occurring. Besides, the solid composite Li/LiFePO4 (LFP) cell with the anion-immobilized SCEs shows a superior discharge specific capacity of 158 mAh g-1 at 0.2 C. The results illustrate that the anion-immobilized SCEs are one of the most promising choices to optimize the performances of ASSLMBs.
Research Article
Influence of process parameters and aging treatment on the microstructure and mechanical properties of AlSi8Mg3 alloy fabricated by selective laser melting
Yao-xiang Geng, Hao Tang, Jun-hua Xu, Yu Hou, Yu-xin Wang, Zhen He, Zhi-jie Zhang, Hong-bo Ju, and Li-hua Yu
Available online 31 March 2021, https://doi.org/10.1007/s12613-021-2287-1
[Abstract](41) [PDF 1808KB](7)
Abstract:
Many studies have investigated the selective laser melting (SLM) of AlSi10Mg and AlSi7Mg alloys, but there is still a lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM. In this work, a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM. The results showed that this new alloy exhibited excellent SLM processability with the lowest porosity of 0.07%. Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser scanning speed due to the precipitation of Mg2Si nanoparticles from the α-Al matrix induced by high-intensity intrinsic heat treatment during SLM. The maximum microhardness and compressive yield strength of the alloy reached 211±4 HV and 526±12 MPa, respectively. After aging treatment at 150 ℃, the maximum microhardness and compressive yield strength of the samples were further improved to 221±4 HV and 577±5 MPa, respectively. These values are higher than those of most known aluminum alloys fabricated by SLM. This paper provides a new idea for optimizing the mechanical properties of Al-Si-Mg alloys fabricated using SLM.
Research Article
Ultrafine nano-scale Cu2Sb alloy confined in three-dimension porous carbon as anode for sodium-ion and potassium-ion batteries
Dan Wang, Qun Ma, Kang-hui Tian, Chan-qin Duan, Zhi-yuan Wang, and Yan-guo Liu
Available online 27 March 2021, https://doi.org/10.1007/s12613-021-2286-2
[Abstract](97) [PDF 1210KB](7)
Abstract:
Ultrafine nano-scale Cu2Sb alloy confined in three-dimension porous carbon is synthesized through NaCl template-assisted vacuum freeze-drying followed by high temperature sintering process and is evaluated as anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). It exerts excellent cycling durability (the capacity can be maintained at 328.3 mAh g-1 after 100 cycles for SIBs and 260 mAh g-1 for PIBs) and rate capability (199 mAh g−1 at 5 A g−1 for SIBs and 148 mAh g−1 at 5 A g−1 for PIBs) due to smooth electron transport path and fast Na/K ion diffusion rate as well as restricted volume changes owning to the synergistic effect of three-dimensional porous carbon networks and ultrafine bimetallic nanoalloy. This study provides an ingenious design route and simple preparation method towards exploring high-property electrode for K-ion and Na-ion batteries, and it also opens up broad application prospects in other electrochemical applications.
Research Article
Effects of Mg and La on the evolution of inclusions and microstructure in Ca–Ti treated steel
Lei Wang, Bo Song, Zhan-bing Yang, Xiao-kang Cui, Zhen Liu, Wen-sen Cheng, and Jing-hong Mao
Available online 26 March 2021, https://doi.org/10.1007/s12613-021-2285-3
[Abstract](30) [PDF 1481KB](8)
Abstract:
The evolution of inclusions and the formation of acicular ferrite (AF) in Ca–Ti treated steel were systematically investigated after Mg and La addition. The inclusions in molten steel were Ca–Al–O, Ca–Al–Mg–O and La–Mg–Ca–Al–O after Ca, Mg and La addition, respectively. The type of oxide inclusions in final quenched samples was the same as that in molten steel. However, unlike these in molten steel, inclusions were Ca–Al–Ti–O + MnS, Ca–Mg–Al–Ti–O + MnS and La–Ca–Mg–Al–Ti–O + MnS in Mg-free, Mg-containing and La-containing samples, respectively. The inclusions distributed dispersedly in the La-containing sample. In addition, the average size of the inclusions in the La-containing sample was the smallest while the number density of inclusions was the highest. The size of effective inclusions (nucleus of AF formation) was mainly in the range of 1  to 3 μm. And the content of ferrite side plates (FSP) decreased, while the percentage of acicular ferrite (AF) increased by 16.2% due to the increase in the number of effective inclusions in the La-containing sample in this study.
Research Article
Application of visualization and simulation in steel metallurgy industry process
Te Xu, Guang Song, Yang Yang, Pei-xin Ge, and Li-xin Tang
Available online 24 March 2021, https://doi.org/10.1007/s12613-021-2283-5
[Abstract](38) [PDF 1092KB](4)
Abstract:
Steel production involves the transfer and transformation of material and energy at different levels, structures and scales, and the interaction between material and energy. And this process incurs lots of informations in material and energy dimension. Conserning the black-box feature of iron and steel production process, process visualization play an important role with the continuous development of virtual reality technology. It will be inevitably beneficial to parameter correction, technical support decision-making, personnel training and other aspects of steel metallurgy industry. This paper analyses the technological characteristics of the whole process of iron and steel-metallurgical industry whose final products are coils or sheets. First of all, the visualization technology route based on virtual reality is built. Based on the characteristics of virtual reality technology, the visual simulation model for the process scheduling of the iron and steel enterprise raw materials field, slab and hot rolling process is built. Next, the visualization simulation platform of the iron and steel-metallurgy plantwide process which includes ironmaking, steelmaking, hot rolling and cold rolling is developed. Finally, the visualization simulation platform for future application and development prospect are presented.
Research Article
A multi-energy synergistic optimization in steelmaking process based on energy hub concept
Shuai Liu, Sheng Xie, and Qi Zhang
Available online 23 March 2021, https://doi.org/10.1007/s12613-021-2281-7
[Abstract](34) [PDF 1335KB](5)
Abstract:
The production process of iron and steel is accompanied by a large amount of energy production and consumption. Optimal scheduling and utilization of these energy within energy systems are crucial to realize a reduction in the cost, energy use and CO2 emissions. However, it is difficult to model and schedule energy within steel works because different types of energy and devices are involved. Energy hub (EH), as a universal modeling frame, is widely used in multi-energy systems (MES) to improve its efficiency, flexibility, and reliability. This paper proposed an efficient multi-layer model based on the EH concept, which is designed to systematically model the energy system and schedule energy within steelworks to meet the energy demand. Besides, to emulate to the actual working conditions of the energy devices, the method of fitting the curve is used to describe the efficiency of the energy devices. Moreover, to evaluate the applicability of the proposed model, a case study is conducted to minimize both the economic operation cost and CO2 emissions. The optimal results demonstrated that the model is suitable for energy systems within steel works; further, the economic operation cost decreased by 3.41%, and the CO2 emissions decreased by approximately 3.67%.
Research Article
Flotation kinetics performance of different coal size fractions with nanobubbles
Hua Han, An Liu, Cai-li Wang, Run-quan Yang, Shuai Li, and Huai-fa Wang
Available online 6 March 2021, https://doi.org/10.1007/s12613-021-2280-8
[Abstract](141) [PDF 957KB](21)
Abstract:
The flotation kinetics of different size fractions of conventional and nanobubbles (NBs) flotation were compared to investigate the effect of NBs on flotation performance of various coal particle size. Six flotation kinetics models were selected to fit the flotation data and NBs were observed on the hydrophobic surface under hydrodynamic cavitation by atomic force microscope (AFM) scanning. The flotation results indicate that the best flotation performance of size fraction at -0.125+0.074 mm can be obtained either in conventional or NBs flotation, NBs increase the combustible recovery of almost all of the size fractions, but increase the product ash content of -0.25-0.074 mm and reduce the product ash content of -0.045 mm at the same time. The first-order models can both be used to fit the flotation data in conventional and NBs flotation, the classical first-order model is the most suitable one. NBs have an obvious enhancement of flotation rate on coarse size fraction (-0.5+0.25 mm) but decrease the flotation rate of the medium size (-0.25+0.074 mm), the improvement of flotation speed on fine coal particles (-0.074 mm) is probably the reason of the better flotation performance of raw sample flotation.
Research Article
Surface nanobubbles on hydrophobic surface and its implication to flotation
Chen-wei Li, Dan-long Li, Xin Li, Ming Xu, and Hai-jun Zhang
Available online 5 March 2021, https://doi.org/10.1007/s12613-021-2279-1
[Abstract](168) [PDF 1804KB](15)
Abstract:
Nanobubbles play a potential role in the application of fine particles flotation. In this work, the identification of nanoentities was identified with contact mode atomic force microscope (AFM). Meanwhile, the influence of setpoint ratio and amplitude of cantilever and the responses of the formed surface nanobubbles to the fluctuations of pH, salt concentrations, and surfactant concentrations in the slurry, were studied respectively. Nanobubbles were found on highly oriented pyrolytic graphite (HOPG) surface as HOPG was immersed in deionized water in the ambient temperature. The coalescence of nanobubbles occurred under contact mode, which provides strong evidence supporting the gaseous nature of these nanostructures on HOPG. The measuring height of surface nanobubbles decreased with the setpoint ratio (Asetpoint/Afree). The change in concentrations of pH and MIBC shows a negligible influence on lateral size and height of the preexisting surface nanobubbles. The addition of LiCl results in a negligible change in lateral size but an obvious change in height of surface nanobubbles. The present results are expected to provide a valuable reference to understand the properties of surface nanobubbles and design nanobubbles-assisted flotation processes.
Invited Review
Solid electrolyte-electrode interface based on buffer therapy in solid-state lithium batteries
Lei-ying Wang, Li-fan Wang, Rui Wang, Rui Xu, Chun Zhan, Woochul Yang, and Gui-cheng Liu
Available online 4 March 2021, https://doi.org/10.1007/s12613-021-2278-2
[Abstract](169) [PDF 1365KB](9)
Abstract:
In the past few years, the all-solid lithium battery has attracted worldwide attentions, the ionic conductivity of some all-solid lithium-ion batteries has reached 10-3~10-2 S/cm, indicating that the transport of lithium ions in solid electrolytes is no longer a major problem. However, some interface issues become research hotspots. Examples of these interfacial issues include the electrochemical decomposition reaction at the electrode-electrolyte interface; the low effective contact area between the solid electrolyte and the electrode etc. In order to solve the issues, researchers have pursued many different approaches. The addition of a buffer layer between the electrode and the solid electrolyte has been at the center of this endeavor. In this review paper, we provide a systematic summarization of the problems on the electrode-solid electrolyte interface and detailed reflection on the latest works of buffer-based therapies, and the review will end with a personal perspective on the improvement of buffer-based therapies.
Research Article
Hot compressive deformation of eutectic Al-17at% Cu alloy on the interface of the Cu-Al composite plate produced by horizontal continuous casting
Jun Wang, Fan Zhao, Guo-liang Xie, Jia-xuan Xu, and Xin-hua Liu
Available online 3 March 2021, https://doi.org/10.1007/s12613-021-2276-4
[Abstract](105) [PDF 2138KB](9)
Abstract:
On the interface of the Cu-Al composite plate from horizontal continuous casting, the eutectic tissue layer thickness accounts for more than 90% of the total interface thickness, and the deformation in rolling forming plays an important role in the quality of the composite plate. The eutectic tissue material on the interface of the Cu-Al composite plate was prepared by changing the cooling rate of ingot solidification and the deformation in hot compression was investigated. The results show that deformation temperature is over 300 ℃, the softening effect of dynamic recrystallization of α-Al is greater than the hardening effect, and uniform plastic deformation of eutectic tissue is caused. The constitutive equation of flow stress in the eutectic tissue layer was established by Arrhenius hyperbolic-sine mathematics model, providing a reliable theoretical basis for the deformation of the Cu-Al composite plate.
Research Article
Effect of an external magnetic field on improved electroslag remelting cladding process
Zhi-wen Hou, Yan-wu Dong, Zhou-hua Jiang, Zhi-hao Hu, Li-meng Liu, and Kun-jie Tian
Available online 3 March 2021, https://doi.org/10.1007/s12613-021-2277-3
[Abstract](102) [PDF 1357KB](8)
Abstract:
Obtaining a uniform interface temperature field plays a crucial role in the interface bonding quality of bimetal compound rolls. Therefore, in this study, an improved electroslag remelting cladding (ESRC) process using external magnetic field is proposed to improve the uniformity of the interface temperature of compound rolls. The improved ESRC comprises a conventional ESRC circuit and an external coil circuit. A comprehensive 3D model, including multi-physics fields is solved to study the effect of external magnetic field on the multi-physics fields and interface temperature uniformity. The simulated results demonstrate that the non-uniform Joule heat and flow fields cause a non-uniform interface temperature in the conventional ESRC. As for the improved ESRC, the magnetic flux density (Bcoil) along the z-axis is produced by an anticlockwise current of the external coil. The rotating Lorentz force is generated from the interaction between the radial current and axial Bcoil. Therefore, the slag pool flows clockwise, which enhances circumferential effective thermal conductivity. As a result, the uniformity of the temperature field and interface temperature improve. In addition, the magnetic flux density and rotational speed of the simulated results are in good agreement with those of the experimental results, which verifies the accuracy of the improved ESRC model. Therefore, an improved ESRC is efficient for industrial production of the compound roll with a uniform interface bonding quality.
Research Article
MnO2/carbon nanocomposite based on silkworm excrement for high-performance supercapacitors
Pian Zhang, Yun-hao Wu, Hao-ran Sun, Jia-qi Zhao, Zhi-ming Cheng, and Xiao-hong Kang
Available online 27 February 2021, https://doi.org/10.1007/s12613-021-2272-8
[Abstract](172) [PDF 1354KB](13)
Abstract:
MnO2/biomass carbon nanocomposite was synthesized by a facile hydrothermal reaction. Silkworm excrement acted as a carbon precursor, which was activated by ZnCl2 and FeCl3 combining chemical agents under Ar atmosphere. The thin and flower-like MnO2 nanowires were in situ anchored on the surface of biomass carbon, in which biomass carbon not only offered the high conductivity and good structural stability but also relieved the large volume expansion during the charge/discharge process. The obtained MnO2/biomass carbon nanocomposite electrode exhibited a high specific capacitance (238 F g-1 at 0.5 A g-1) and a superior cycling stability with only 7% degradation after 2000 cycles. The good electrochemical performance is accredited to the high specific surface area, multi-level hierarchical structure, and good conductivity. This study proposes a promising method to make use of biological waste and broadens MnO2 based electrode materials application for next-generation energy storage and conversion devices.
Research Article
Experimental and numerical study on immobilization and leaching characteristics of fluoride from phosphogypsum based cemented paste backfill
Qiu-song Chen, Shi-yuan Sun, Yi-kai Liu, Chong-chong Qi, Hui-bo Zhou, and Qin-li Zhang
Available online 27 February 2021, https://doi.org/10.1007/s12613-021-2274-6
[Abstract](575) [PDF 1732KB](41)
Abstract:
Phosphogypsum (PG) is the typical by-product of phosphoric acid and phosphate fertilizers by acid digestion. The application of cemented paste backfill was feasibly investigated for the remediation of PG. The present study evaluated the fluorine immobilization mechanisms and attempted to construct a related thermodynamic and geochemical modeling to describe the stabilization performance. Physico-chemical and mineralogical analyses were performed on PG and hardened PCPB. The correlated macro and microstructural properties were obtained from analyzing the combination of unconfined compressive strength and SEM-EDS imaging. Acid/base dependent leaching tests were performed to ascertain the fluoride leachability. Additionally, GEMS and Phreeqc were applied in this study as tools to characterize the PCPB hydration and deduce its geochemical characteristics. The results proved that multiple factors are involved in fluorine stabilization, among which the C-S-H gel was found to be associated with retention. Besides, the concentration of acid/base highlights in regulating the leaching behavior. Although the quantitative comparison with the experimental data shows further modification should be introduced into the simulation before being used as a predictive implement to determine PG management options, the modeling enabled the identification of the impurity phases controlling the stability and leachability.
Invited Review
Operation optimization of the steel manufacturing process: A brief review
Zhao-jun Xu, Zhong Zheng, and Xiao-qiang Gao
Available online 27 February 2021, https://doi.org/10.1007/s12613-021-2273-7
[Abstract](129) [PDF 497KB](12)
Abstract:
Under the realistic background of excess production capacity, product structure imbalance and high material and energy consumption in steel enterprises, the implementation of operation optimization for steel manufacturing process is essential for reducing production cost, increasing production efficiency or energy efficiency and improving production management. In this paper, the operation optimization problem of the steel manufacturing process was analyzed, which needed to go through a complex production organization from customers’ orders to workshop production. The existing research on the operation optimization techniques were reviewed, including the process simulation, the production planning, the production scheduling, the interface scheduling and the scheduling of auxiliary equipment. The literature review reveals that, although much research has been devoted to optimizing the operation of steel production, these techniques are usually independent and unsystematic. Therefore, future works related to the operation optimization of the steel manufacturing process were finally summarized, which were based on the multi-technology fusion and the multi-discipline crossover.
Research Article
Effect of extrusion process on microstructure and mechanical and corrosion properties of biodegradable Mg-5Zn-1.5Y magnesium alloy
Hassan Jafari, Amir Houshang Mojiri Tehrani, and Mahsa Heydari
Available online 27 February 2021, https://doi.org/10.1007/s12613-021-2275-5
[Abstract](159) [PDF 1743KB](12)
Abstract:
The effect of extrusion temperature and ratio on microstructure, hardness, compression, and corrosion behavior of Mg-5Zn-1.5Y alloy were analyzed. The microstructural observations revealed that the cast alloy consists of α-Mg grains, and Mg3Zn6Y and Mg3Zn3Y2 intermetallic compounds, mostly located on the α-Mg grain boundaries. Extruded alloy at higher temperatures showed coarser grain microstructures, whereas those extruded at higher ratios contained finer ones, although more DRXed grains with lower intermetallics were measured at both conditions. Combined conditions of the lower temperature (340°C) and higher ratio (1:11.5) provided higher compressive strengths. However, no significant hardness improvement was achieved. The extrusion process could decrease the corrosion rate of the cast alloy in simulated body fluid for over 80% due to primarily the refined microstructure. The extrusion temperature showed a more pronounced effect on corrosion resistance compared to the extrusion ratio, and the higher the extrusion temperature, the higher the corrosion resistance.
Research Article
Enhanced electrochemical performance of Si/C electrode through surface modification using SrF2 particle
Jun Yang, Yuan-hua Lin, Bing-shu Guo, Ming-shan Wang, Jun-chen Chen, Zhi-yuan Ma, Yun Huang, and Xing Li
Available online 25 February 2021, https://doi.org/10.1007/s12613-021-2270-x
[Abstract](162) [PDF 1226KB](9)
Abstract:
The silicon-based materials have a high theoretical specific capacity and is one of the best anode for the next generation of advanced lithium-ion batteries (LIBs). However, it is difficult for the silicon-based anode to form a stable solid-state interphase (SEI) during Li alloy/de-alloy process due to the large volume change (up to 300%) between silicon and Li4.4Si, which seriously limits the cycle life of the LIBs. Herein, we use strontium fluoride (SrF2) particle to coat the silicon-carbon (Si/C) electrode (SrF2@Si/C) to help forming a stable and high mechanical strength SEI by spontaneously embedding the SrF2 particle into SEI. Meanwhile the SEI can inhibit the volume expansion of the silicon-carbon anode during the cycle. The electrochemical test results show that the cycle performance and the ionic conductivity of the SrF2@Si/C anode has been significantly improved. The X-ray photoelectron spectroscopy (XPS) analysis reveals that there are fewer electrolyte decomposition products formed on the surface of the SrF2@Si/C anode. This study provides a facile approach to overcome the problems of Si/C electrode during the electrochemical cycling, which will be beneficial to the industrial application of silicon-based anode materials.
Research Article
Synthesis, characterization and radioluminescence properties of erbium-doped yttria phosphors
Fatma Unal, Faruk Kaya, and Kursat Kazmanli
Available online 22 February 2021, https://doi.org/10.1007/s12613-021-2269-3
[Abstract](213) [PDF 650KB](18)
Abstract:
In this paper, radioluminescence (RL) behaviour of erbium-doped yttria nanoparticles (Y2O3:Er3+ NPs) which were produced by sol-gel method is reported for future scintillator applications. NPs with dopant rate of 1, 5, 10 and 20 at. % Er were produced and calcined at 800°C, effects of increased calcination temperature on the RL behaviour (1100°C) was also reported. X-ray Diffraction (XRD) results showed that all phosphors had the cubic Y2O3 bixbyite-type structure. The lattice parameters, crystallite sizes and lattice strain values were calculated by Cohen-Wagner (C-W) and Williamson-Hall (W-H) methods, respectively. Additionally, the optimum solubility value of the Er3+ dopant ion in the Y2O3 host lattice was calculated according to Vegard’s law to be approximately 4 at. %, which was experimentally obtained from the 5 at. % Er3+ ion containing solution. Both peak shifts in XRD patterns and X-Ray Photoelectron Spectroscopy (XPS) analyses confirmed that Er3+ dopant ions were successfully incorporated into the Y2O3 host structure. High-Resolution Transmission Electron Microscopy (HRTEM) results verified the average CS values and agglomerated NPs morphologies were revealed. Scanning Electron Microscopy (SEM) results showed the neck formation between the particles due to increased calcination temperature. As a result of the RL measurements under a Cu Kα X-ray radiation (λ=0.154 nm) source with 50 kV and 10 mA beam current, it was determined that the highest RL emission belongs to 5 at. % Er doped sample. In the RL emission spectrum, the emission peaks were observed in the wavelength range of 510-575 nm (2H11/2, 4S3/2-4I15/2, green emission) and 645-690 nm (4F9/2-4I15/2, red emission). The emission peaks at 581, 583, 587, 593, 601, 611 and 632 nm wavelengths were also detected. It was found that both dopant rate and calcination temperature affected the RL emission intensity. The colour shifted from red to green with increasing calcination temperature which was attributed to the increased crystallinity and reduced crystal defects.
Invited Review
Mechanism and monitoring and early warning technology of rock burst in coal mine
Xue-qiu He, Chao Zhou, Da-zhao Song, Zhen-lei Li, An-ye Cao, Shen-quan He, and Majid Khan
Available online 18 February 2021, https://doi.org/10.1007/s12613-021-2267-5
[Abstract](264) [PDF 2015KB](21)
Abstract:
Based on a massive amount of published literature and the long-term practice of our research group in the field of prevention and control of the rock burst, the research progresses, and shortcomings in understanding the phenomenon of the rock burst have been comprehensively studied. The study was conducted to focus on the occurring mechanism, monitoring and early warning technology. The results show that the prevention and control of the rock burst have made significant progress. However, with the increasing mining depth, several unresolved concerns remain challenging. From the analysis of in-depth research, it is inferred that the rock burst related disasters include three main problems: The induced factors are complicated, and the mechanism is still unclear. The accuracy of monitoring equipment and the multi-source stereo monitoring technology is insufficient. The monitoring and warning standards of the rock burst need to be further clarified and improved. Combined with the Internet of Things(IoT), cloud computing and big data, etc., the study trend of the rock burst can be expected. Furthermore, the mechanism of multi-phase and multi-field coupling induced by the rock burst in large scale needs further exploration. The multi-system and multi-parameter integrated monitoring and early warning system and remote monitoring cloud platform for rock burst should be researched and developed. The high-reliability sensing technology equipment and perfect monitoring and early warning standards are considered as the direction of development for the rock burst in the future. This research will help experts and technicians to adopt effective measures for controlling the rock burst disasters.
Research Article
Role of trace additions of Ca and Sn in improving the corrosion resistance of Mg-3Al-1Zn alloy
Pan-pan Wang, Hai-tao Jiang, Yu-jiao Wang, Yun Zhang, Shi-wei Tian, Ye-fei Zhang, and Zhi-ming Cao
Available online 18 February 2021, https://doi.org/10.1007/s12613-021-2268-4
[Abstract](144) [PDF 1276KB](7)
Abstract:
The limited wide applicability of commercial Mg alloys is mainly attributed to the poor corrosion resistance. Addition of alloying elements is the simplest and effective method to improve the corrosion properties. Based on the low-cost alloy composition design, the corrosion behavior of commercial Mg-3Al-Zn (AZ31) alloy bearing minor Ca or Sn element was characterized by scanning Kelvin probe force microscopy, hydrogen evolution, electrochemical measurements and corrosion morphology analysis. Results revealed that the potential difference of Al2Ca/α-Mg and Mg2Sn/α-Mg was ∼230±19 mV and ∼80±6 mV, much lower than that of Al8Mn5/α-Mg (∼430±31 mV) in AZ31 alloy, which illustrated that AZ31-0.2Sn alloy performed the best corrosion resistance, followed by AZ31-0.2Ca, while AZ31 alloy exihited the worst corrosion resistance. Moreover, Sn dissolved into matrix obviously increased the potential of α-Mg and participated in the formation of dense SnO2 film at the interface of matrix, while Ca element was enriched in the corrosion product layer, resulting in the corrosion product layer of AZ31-0.2Ca/Sn alloys more compact, stable and protective than AZ31 alloy. Therefore, AZ31 alloy bearing 0.2wt% Ca or Sn element exhibited excellent balanced properties, which is potential to be applied in commercial more comprehensively.
Research Article
A chain-like compound of Si@CNTs nanostructure and MOF-derived porous carbon as anode for Li-ion batteries
Ying-jun Qiao, Huan Zhang, Yu-xin Hu, Wan-peng Li, Wen-jing Liu, Hui-ming Shang, Mei-zhen Qu, Gong-chang Peng, and Zheng-wei Xie
Available online 6 February 2021, https://doi.org/10.1007/s12613-021-2266-6
[Abstract](173) [PDF 1589KB](12)
Abstract:
Silicon anodes are considered to have great prospects, but many of their defects still need to be improved. To prepare hybrid materials based on porous carbon is one of the effective ways to alleviate the adverse impact resulting from the volume change and the inferior electronic conductivity of silicon electrode. Herein, a chain-like carbon cluster structure is prepared, in which MOF-derived porous carbon acts as a shell structure to integrally encapsulate Si nanoparticles, and CNTs play a role in connecting carbon shells. Based on the exclusive structure, the carbon shell can cushion the volume expansion more effectively and CNTs can improve overall stability and conductivity. The resulted composite reveals excellent rate capacity and enhanced cycling stability, which in particular achieve a capacity of 732 mAh g-1 at 2 A g-1 and shows a reservation rate of 72.3% after cycling 100 times at 1 A g-1.
Research Article
Novel confinement combustion method to nanosized WC/C for efficient electrocatalytic oxygen reduction
Peng-qi Chen, Huan Wu, Yun-xiao Tai, Yu-fei Gao, Jia-yu Chen, and Ji-gui Cheng
Available online 4 February 2021, https://doi.org/10.1007/s12613-021-2265-7
[Abstract](192) [PDF 993KB](9)
Abstract:
Nanosized WC/C catalyst was synthesized via a novel ultra-rapid confinement combustion synthesis method. Result showed that the amount of activated carbon (AC) played an important role in the morphology and structure controlling of both the precursor and the final powder. Due to the confinement of the pore structure and large specific surface area of AC, the WC particles synthesized inside the pores of AC had the size of 10-20 nm. When applied to oxygen reduction performance, the half-wave potential was -0.24 V and the electron transfer number was 3.45, which meant that the main reaction process is the transfer of four electrons. The detailed electrocatalytic performance and the underlying mechanism were investigated in this work. Our study provides a novel approach for the design of new composition and structure catalysts which has a certain significance for promoting the commercialization of fuel cells.
Research Article
The modulation of discharge plateau of benzoquinone for sodium-ion batteries
Feng-hua Chen, Yi-wen Wu, Huan-hong Zhang, Zhan-tu Long, Xiao-xin Lin, Ming-zhe Chen, Qing Chen, Yi-fan Luo, Shu-Lei Chou, and Rong-hua Zeng
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2261-y
[Abstract](294) [PDF 1246KB](18)
Abstract:
P-Benzoquinone (BQ) is a promising candidate for next generation sodium ion batteries (SIBs) owing to its high theoretical specific capacity, good reaction reversibility and high resource availability. However, BQ face many challenges in practical application, such as low discharge plateau (~2.7 V) as cathode material or high discharge plateau as anode material compared with inorganic materials for SIBs, and high solubility in organic electrolytes, resulting in low power density and energy density. Here, tetrahydroxybenzoquinone tetrasodium salt (Na4C6O6) is synthesized through a simple neutralization reaction at low temperature. The four -ONa electron donating groups introduced on structure of BQ lower greatly the discharge plateau from ~2.70 V to ~1.26 V with the decrease value of over 1.4 V, which can make BQ change from cathode to anode material for SIBs. At the same time, the addition of four -ONa hydrophilic groups inhibit effectively the dissolution of BQ in the organic electrolyte a certain extent. As a result, Na4C6O6 as anode displays a moderate discharge capacity and cycling performance at an average work voltage of ~1.26 V versus Na/Na+. When evaluated as a Na-ion full cell (NIFC), a Na3V2(PO4)3 || Na4C6O6 NIFC reveals a moderate discharge capacity and an average discharge plateau of ~1.4 V. This research offers a new molecular structure design strategy to reduce the discharge plateau and restrain the dissolution of organic electrode materials simultaneously.
Research Article
Superior sodium and lithium storage in strongly coupled amorphous Sb2S3 spheres and carbon nanotubes
Qiong Jiang, Wen-qi Zhang, Jia-chang Zhao, Pin-hua Rao, and Jian-feng Mao
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2259-5
[Abstract](219) [PDF 1363KB](9)
Abstract:
A facile one-step strategy involving the reaction of antimony chloride with thioacetamide at room temperature is successfully developed for the synthesis of strongly coupled amorphous Sb2S3 spheres and carbon nanotubes (CNTs). Benefitting from the unique amorphous structure and its strongly coupled effect with the conductive network of CNTs, this hybrid electrode (Sb2S3@CNTs) exhibits remarkable sodium and lithium storage properties with high capacity, good cyclability and prominent rate capability. For sodium storage, a high capacity of 814 mAh·g-1 at 50 mA·g-1 is delivered by the electrode, and a capacity of 732 mAh·g-1 can still be obtained after 110 cycles. Even up to 2000 mA·g-1, a specific capacity of 584 mAh·g-1 can be achieved. For lithium storage, the electrode exhibits a high capacity of 1136 and 704 mAh·g-1 at 0.05 and 2 A·g-1, respectively. And the cell holds a capacity of 1104 mAh·g-1 under 50 mA·g-1 over 110 cycles. The simple preparation approach, and remarkable electrochemical properties make the Sb2S3@CNTs electrode a promising anode for both sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs).
Research Article
Effects of Nd on microstructure and mechanical properties of as-cast Mg-12Gd-2Zn-xNd-0.4Zr alloys with stacking faults
Li-xin Hong, Rong-xiang Wang, and Xiao-bo Zhang
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2264-8
[Abstract](170) [PDF 1451KB](4)
Abstract:
In order to study the effects of Nd addition on microstructure and mechanical properties of Mg-Gd-Zn-Zr alloys, the microstructure and mechanical properties of the as-cast Mg-12Gd-2Zn-xNd-0.4Zr (x = 0, 0.5, and 1 wt%) alloys were investigated by using optical microscope, scanning electron microscope, X-ray diffractometer, nano indentation tester, microhardness tester, and tensile testing machine. The results show that the microstructures mainly consist of α-Mg matrix, eutectic phase and stacking faults. The addition of Nd plays a significant role in grain refinement and uniform microstructure. The tensile yield strength and microhardness increase but the compression yield strength decreases with increasing Nd addition, leading to weakening tension-compression yield asymmetry in reverse of the Mg-12Gd-2Zn-xNd-0.4Zr alloys. The highest ultimate tensile strength (194 MPa) and ultimate compression strength (397 MPa) are obtained with 1 wt% Nd addition of the alloy.
Research Article
Blast furnace ironmaking process with super high TiO2 in the slag: Density and surface tension of the slag
Zheng-de Pang, Yu-yang Jiang, Jia-wei Ling, Xue-wei Lv, and Zhi-ming Yan
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2262-x
[Abstract](199) [PDF 886KB](15)
Abstract:
Considering high novelty and potential on ultra–high (>80%) or full V–Ti–Magnetite ore under blast furnace smelting, we are conducting a series of works on physics character of high TiO2 bearing blast furnace slag (BFS) for slag optimization. This work discussed the density and surface tension of high TiO2 bearing BFS using the Archimedean principle and the maximum bubble pressure method, respectively. The influence of TiO2 content and MgO/CaO (mass ratio) on the density and surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags were investigated. Results indicated that the density of slags decreased as increasing TiO2 content from 20 to 30 wt%, but it increased slightly as increasing MgO/CaO from 0.32 to 0.73. In view of silicate network structure, the density and the degree of polymerization (DOP) of network structure have a consistent trend. The addition of TiO2 reduces (Q3)2/(Q2) ratio, decreases DOP, which leads to the decrease of slag density. The surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags decreased dramatically as increasing TiO2 content from 20 to 30 wt%. Conversely, it increased as increasing MgO/CaO from 0.32 to 0.73. Furthermore, the iso–surface tension lines were obtained under 1723K using the Tanaka developed model in view of Butler formula. It may be useful for slag optimization of ultra–high proportion (>80%) or even full V–Ti–Magnetite ore under BF smelting.
Research Article
Experimental investigation on the intermetallic growth behavior during post deformation annealing in multilayer Ti/Al/Nb composite interfaces
Roya Jafari and Beitallah Eghbali
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2263-9
[Abstract](192) [PDF 1498KB](3)
Abstract:
In the present research, the tri-metal Ti-Al-Nb composites were processed through three procedures: hot pressing, rolling, and hot pressing, followed by subsequent rolling. The fabricated composites were then subjected to annealing at 600, 625, and 650 ºC temperatures at different times. Microstructure observation at the interfaces reveals that the increase in plastic deformation strain significantly affects TiAl3 intermetallic layers’ evolution and accelerates the layers’ growth. On the contrary, the amount of applied strain does not significantly affect the evolution of the NbAl3 intermetallic layer thickness. It was also found that Al and Ti atoms’ diffusion has occurred throughout the TiAl3 layer, but only Al atoms diffuse through the NbAl3 layer. The slow growth rate of the NbAl3 intermetallic layer is due to the lack of diffusion of Nb atoms and the high activation energy of Al atoms’ reaction with Nb atoms.
Research Article
Discharge properties of Mg-Sn-Y alloys as anodes for Mg-air batteries
Hua-bao Yang, Liang Wu, Bin Jiang, Bin Lei, Ming Yuan, Hong-mei Xie, Andrej Atrens, Jiang-feng Song, Guang-sheng Huang, and Fu-sheng Pan
Available online 26 January 2021, https://doi.org/10.1007/s12613-021-2258-6
[Abstract](297) [PDF 1766KB](9)
Abstract:
Mg-Sn-Y alloys with different Sn contents (wt%) were assessed as anode candidates for Mg-air batteries. The relationship between microstructure (including the second phase, grain size, and texture) and discharge properties of the Mg-Sn-Y alloys was examined using microstructure observation, electrochemical measurements, and galvanostatic discharge tests. The Mg-0.7Sn-1.4Y alloy had a high steady discharge voltage of 1.5225 V and a high anodic efficiency of 46.6% at 2.5 mA·cm-2. These good properties were related to its microstructure: small grain size of 3.8 μm, uniform distribution of small second phase particles of 0.6 μm, and a high content (vol%) of (11-20)/(10-10) orientated grains. The Scanning Kelvin Probe Force Microscopy (SKPFM) indicated that the Sn3Y5 and MgSnY phases were effective cathodes causing micro-galvanic corrosion which promoted the dissolution of Mg matrix during the discharge process.
Research Article
Preparation of CaO-containing carbon pellets from coking coal and calcium oxide: Effects of temperature, pore distribution and carbon structure on compressive strength in pyrolysis furnace
Xiao-min You, Xue-feng She, Jing-song Wang, Qing-guo Xue, and Ze-yi Jiang
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2255-9
[Abstract](271) [PDF 1169KB](2)
Abstract:
CaO-containing carbon pellets (CCCP) were successfully prepared from well-mixed coking coal (CC) and calcium oxide (CaO) and roasted at different pyrolysis temperatures. The effects of temperature, pore distribution and carbon structure on compressive strength of CCCP was investigated in pyrolysis furnace (350–750 °C). The results showed that as the roasting temperature increased, the compressive strength also increased and furthermore, structural defects and imperfections in the carbon crystallites were gradually eliminated to form more organized char structures, thus forming high-ordered CC. Notably, the CCCP preheated at 750 °C exhibited the highest compressive strength. A positive relationship between the compressive strength and pore-size homogeneity was established. A linear relationship between the compressive strength of the CCCP and the carbon layer spacing of CC was observed. Additionally, a four-stage caking mechanism was developed.
Invited Review
A review of the synthesis and application of zeolites from coal-based solid wastes
Xiao-yu Zhang, Chun-quan Li, Shui-lin Zheng, Yong-hao Di, and Zhi-ming Sun
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2256-8
[Abstract](286) [PDF 870KB](13)
Abstract:
Zeolite derived from coal-based solid wastes (coal gangue and coal fly ash) not only can cope with the environmental problems caused by coal-based solid wastes but also achieve their valuable utilization. In this paper, the physicochemical properties of coal gangue and coal fly ash were introduced. Then the mechanism and application characteristics of the pretreatment processes for zeolite synthesis from coal-based solid wastes were introduced as well. After that, the synthesis processes of coal-based solid waste zeolite and their merits and demerits were summarized in detail. Furthermore, the application characteristics of various coal-based solid waste zeolites and their common application fields were also illustrated. By the end of this review, we propose that alkaline fusion-assisted supercritical hydrothermal crystallization may be an efficient method for synthesizing coal-based solid waste zeolites. Besides, more attention should be paid to the recycling of alkaline waste liquid and the application of coal-based solid waste zeolites in the field of volatile organic compounds adsorption removal.
Research Article
Analysis of local microstructure and strengthening mechanisms in adjustable-gap bobbin tool friction stir welds of Al-Mg
Dong Wu, Wen-ya Li, Qiang Chu, Yang-fan Zou, Xi-chang Liu, and Yan-jun Gao
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2254-x
[Abstract](265) [PDF 1218KB](9)
Abstract:
The bobbin tool friction stir welding process was used to join 6 mm thick 5A06 aluminum alloy plates. Optical microscope was used to characterize the microstructure. The electron backscatter diffraction (EBSD) identified the effect of non-homogeneous microstructure on the tensile properties. It was observed that the grain size in the top of the stir zone (SZ) is smaller than that in the centre region. The lowest ratio of recrystallization and density of the geometrically-necessary dislocations (GNDs) in the SZ was found in the middle near the thermo-mechanically affected zone (TMAZ) being 22% and 1.15×10-13 m-2, respectively. The texture strength of the heat-affected zone (HAZ) is the largest, followed by that in the SZ, with the lowest being in the TMAZ. There were additional interfaces developed which contributed to the strengthening mechanism, and their effect on tensile strength was analysed. The tensile tests identified the weakest part in the joint at the interfaces, and the specific reduction value is about 93MPa.
Invited Review
Study on influencing factors and mechanism of high-temperature oxidation of high-entropy alloy:A review
Ya Wei, Yu Fu, Zhi-min Pan, Yi-chong Ma, Hong-xu Cheng, Qian-cheng Zhao, Hong Luo, and Xiao-gang Li
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2257-7
[Abstract](294) [PDF 1489KB](9)
Abstract:
Abstract: High-temperature oxidation is a common failure behavior in high-temperature environment, which is widely existed in aircraft engines and aerospace thrusters, and the development of anti-high-temperature oxidation materials has always been the unremitting pursuit of human beings. Ni-based alloy is a common high-temperature material, but the cost is too high. The emergence of high-entropy alloy may make people have more choices for high-temperature oxidation. High-entropy alloy shows good performance in the process of high-temperature oxidation because of its special structure and properties. In this paper, the achievements of high-temperature oxidation in recent years are reviewed. The environment on high-temperature oxidation, temperature, phase structure, alloy elements and preparation methods of high-entropy alloys are summarized. Besides, the reason why high-entropy alloy has good anti-oxidation ability at high-temperature is illuminated. Finally, combined with the current research results, the material selection and application prospect of high-temperature oxidation are put forward.Key words: High-entropy alloy; High-temperature oxidation; Influencing factors; Oxidation mechanism
Research Article
Effects of heat treatments on microstructures of TiAl alloys
Wen Yu, Jian-xin Zhou, Ya-jun Yin, Zhi-xin Tu, Xin Feng, Hai Nan, Jun-pin Lin, and Xian-fei Ding
Available online 16 January 2021, https://doi.org/10.1007/s12613-021-2252-z
[Abstract](325) [PDF 1841KB](17)
Abstract:
This study aims to investigate the effects of heat treatments on microstructures of γ-TiAl alloys. Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat treated in two types of heat treatments. Their microstructures were studied by both optical and scanning electron microscopies. The chemical compositions of two ingots were determined. The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within 1270°C to 1185°C. A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures. They are distributed at grain boundaries when holding at a higher temperature, such as 1260°C. However, B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185°C. Furthermore, the effects of heat treatments on grain refinement and other microstructural parameters are discussed.
Research Article
Combining the 8-hydroxyquinoline intercalated layered double hydroxide film and sol-gel coating for active corrosion protection of the magnesium alloy
Yahya Jafari Tarzanagh, Davod Seifzadeh, and Roghaye Samadianfard
Available online 16 January 2021, https://doi.org/10.1007/s12613-021-2251-0
[Abstract](266) [PDF 1853KB](6)
Abstract:
The 8-Hydroxyquinoline (8-HQ) intercalated Layered Double Hydroxides (LDH) film as underlayer and sol-gel layer was combined for active corrosion protection of the AM60B magnesium alloy. The LDH, LDH/sol-gel, and LDH@HQ/sol-gel coatings were analyzed using the SEM, FESEM, EDX, XRD, AFM, and EIS methods. The SEM images showed that the surface was entirely coated by the LDH film composed of vertically-grown nanosheets. The same morphology was observed for the LDH/sol-gel and LDH@HQ/sol-gel coatings. Also, almost the same topography was observed for both composite coatings except that the LDH@HQ/sol-gel coating had relatively higher surface roughness. Although the LDH film had the same impedance behavior as the alloy sample in 3.5 wt. % NaCl solution, its corrosion resistance was much higher, which could be due to its barrier properties as well as to the trapping of the chloride ions. Similar to the LDH film, the corrosion resistance of the LDH/sol-gel composite diminished with increasing the exposure time. However, its values were much higher than that of the LDH film, which was mainly related to the sealing of the solution pathways. The LDH@HQ/sol-gel composite showed much better anti-corrosion properties than the LDH/sol-gel coating due to the adsorption of the 8-HQ on the damaged areas through the complexation.
Research Article
Three-dimensional antimony sulfide anode with carbon nanotube interphase modified for lithium-ion batteries
Qi Wang, Yue-yong Du, Yan-qing Lai, Fang-yang Liu, Liang-xing Jiang, and Ming Jia
Available online 13 January 2021, https://doi.org/10.1007/s12613-021-2249-7
[Abstract](358) [PDF 841KB](13)
Abstract:
Antimony sulfide (Sb2S3) is a promising anode for lithium-ion batteries due to its high capacity and vast reserves. However, the low electronic conductivity and severe volume change during cycling hinder its commercialization. Herein our work, a 3D Sb2S3 thin film anode was fabricated via a simple vapor transport deposition system by using natural stibnite as raw material and stainless steel fiber-foil (SSF) as 3D current collector, and a carbon nanotube interphase was introduced onto the film surface (3D Sb2S3@CNT) by a simple dropping-heating process to promote the electrochemical performances. This 3D structure can greatly improve the initial coulombic efficiency to a record of 86.6% and high reversible rate capacity of 760.8 mAh g-1 at 10C. With CNT interphase modified, the Sb2S3 anode cycled extremely stable with high capacity retention of 94.7% after 160 cycles. This work sheds light on the economical preparation and performance optimization of Sb2S3-based anodes.
Research Article
Evolution laws of microstructures and mechanical properties during heat treatments for near-α high temperature titanium alloys
Xiao-zhao Ma, Zhi-lei Xiang, Tao Li, Yi-lan Chen, Ying-ying Liu, Zi-yong Chen, and Qun Shu
Available online 6 January 2021, https://doi.org/10.1007/s12613-021-2248-8
[Abstract](284) [PDF 1799KB](6)
Abstract:
Evolution laws of microstructures, mechanical properties and fractographs after different solution temperatures were investigated through various analyses methods. With the increasing solution temperatures, contents of primary α phase decreased, and contents of transformed β structures increased. Lamellar α grains dominated the characteristics of transformed β structures, and widths of secondary α lamellas increased monotonously. For as-forged alloy, large silicides with equiaxed and rod-like morphologies, and nano-scale silicides were found. Silicides with large sizes might be (Ti, Zr, Nb)5Si3 and (Ti, Zr, Nb)6Si3. Rod-like silicides with small sizes precipitated in retained β phase, exhibiting near 45° angles with α/β grain boundaries. Retained β phases in as-heat treated alloys were incontinuous. 980STA exhibited excellent combinations of room temperature (RT) and 650℃ mechanical properties. Characteristics of fracture surfaces largely depended on the evolutions of microstructures. Meanwhile, silicides promoted the formation of mico-voids.
Research Article
Considerations of the green intelligent steel processes and narrow window stability control technology on steel quality
Lu Lin and Jia-qing Zeng
Available online 1 January 2021, https://doi.org/10.1007/s12613-020-2246-2
[Abstract](262) [PDF 761KB](2)
Abstract:
In order to promote the intelligent transformation and upgrading of the steel industry, intelligent technology features of the steel industrial are discussed in this paper, which are based on the present situation and existing problems of the steel industry. Based on the research situation abroad and domestic, Function analysis, reasonable positioning and process optimization approach of each process of steel making segment are expounded in this paper, at the same time the present situation of molten steel quality and implementation path under narrow window control are analysed, The idea of stability narrow window control technology of steel quality controlled by multi–factors including composition, temperature, time, cleanliness, consumption (raw material) is proposed, and it provides important guidance for the development of green and intelligent steel manufacturing process in the future.
Research Article
Carbon dots modified silicon nanoparticle for lithium ion batteries
Qiao-kun Du, Qing-xia Wu, Hong-xun Wang, Xiang-juan Meng, Ze-kai Ji, Shu Zhao, Wei-wei Zhu, Chuang Liu, Min Ling, and Cheng-du Liang
Available online 1 January 2021, https://doi.org/10.1007/s12613-020-2247-1
[Abstract](444) [PDF 1112KB](26)
Abstract:
A new idea is proposed to enhance the interaction between the silicon (Si) particles and binders by using carbon dots (CDs) to functionalize Si particles. Firstly, CDs rich in polar groups were synthesized by a simple hydrothermal method. Then, CDs were loaded on the surface of Si particles by impregnation method to obtain the functionalized Si particles (Si/CDs). Fourier transform infrared reflection (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and High-resolution transmission electron microscope (HRTEM) were used to study the phases and microstructures of Si/CDs. Si/CDs were used as the active material of anode for electrochemical performance experiments. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and constant current charge and discharge experiment were used to study the electrochemical performance of Si/CDs electrodes. The electrodes prepared by Si/CDs have good mechanical structure stability and electrochemical performance. After 150 cycles at 0.2 C, the capacity retention rate of Si/CDs electrode is 64.0%, which is twice as much as the pure Si electrode at the same test conditions.
Research Article
Synthesis of amino functionalized diatomite by glycine and amino silane for high-efficient removal of indoor formaldehyde
Yong-hao Di, Fang Yuan, Xiao-tian Ning, Hong-wei Jia, Yang-yu Liu, Xiang-wei Zhang, Chun-quan Li, Shui-lin Zheng, and Zhi-ming Sun
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2245-3
[Abstract](293) [PDF 1105KB](17)
Abstract:
In order to remove indoor formaldehyde (HCHO) efficiently and cheaply, two kinds of novel amino functionalized diatomite (DE) modified by 3-aminopropyltriethoxysilane (APTS) and glycine (GLY) (i.e. APTS/DE and GLY/DE) were successfully synthesized by wetting chemical method. First, the optimal preparation conditions of the two kinds of amino modified diatomite were determined, and then their microstructure and morphologies were characterized and analyzed. For comparation, a series of batch HCHO adsorption experiments of the two kinds of amino modified diatomite were conducted. According to the experimental results, the pseudo-second-order kinetic model and the Langmuir isotherm model could well describe the adsorption processes, and the maximum adsorption capacity of APTS/DE and GLY/DE prepared under the optimized conditions at 20 ℃ were 5.83 and 1.14 mg·g-1, respectively. In addition, the thermodynamic parameters indicated that the adsorption process is a spontaneous and exothermic process. Overall, the abundant amine groups grafting on the surface of diatomite was derived from Schiff base reaction, which is essential for high-efficient adsorption performance toward HCHO.
Research Article
Mechanical properties of Al-15Mg2Si composites prepared under different solidification cooling rates
Elahe Safary, Reza Taghiabadi, and Mohammad Hosein Ghoncheh
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2244-4
[Abstract](327) [PDF 1571KB](16)
Abstract:
The effect of different cooling rates (2.7, 5.5, 17.1, and 57.5 °C/s) on the solidification parameters, microstructure, and mechanical properties of Al-15Mg2Si composites was studied. The results showed that, high cooling rate refined the Mg2Si particles and changed their morphology to the more compacted forms with less microcracking tendency The average radius and fraction of primary Mg2Si particles decreased from 20 µm and 13.5% to about 10 µm and 7.3%, respectively, as the cooling rate increased from 2.7 °C/s to 57.5 °C/s. Increasing the cooling rate also improved the distribution of microconstituents, decreased the size of grains, and reduced the volume fraction of micropores. The mechanical properties results revealed that augmenting the cooling rate from 2.7 °C/s to about 57.5 °C/s increased the hardness and quality index by 25% and 245%, respectively. High cooling rate also changed the fracture mechanism from brittle dominated to a high-energy ductile mode comprising of extensive dimpled zones.
Research Article
Reciprocating sliding wear properties of sintered Al-B4C composites
Mahmut Can ŞENEL, Yusuf Kanca, and Mevlüt Gürbüz
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2243-5
[Abstract](283) [PDF 1698KB](19)
Abstract:
Pure aluminum and boron carbide reinforced aluminum matrix composites with various content (1, 6, 15, 30 wt.%B4C) were fabricated using the powder metallurgy technique. The influence of boron carbide amount on the mechanical and tribological behavior of sintered Al-B4C was examined. The highest density (~2.54 g/cm3), lowest porosity (4%), maximum Vickers hardness (~75 HV), as well as, lowest weight loss (0.4 mg), and lowest specific wear rate (0.00042 mm3/Nm) under a 7 N load were obtained with Al-30B4C composites. Enhancement of 167% in hardness, a decrease of 75.8% in weight loss, and a decrease of 76.7% in specific wear rate under an applied load of 7 N were determined when compared with pure aluminum. Similarly, the SEM images of the worn surface revealed that the narrowest wear grove (0.85 mm) at a load of 7 N was detected at Al-B4C composite and the main wear mechanism was observed as an abrasive wear mechanism. According to the friction analysis, the coefficient of friction between surfaces increased with increasing boron carbide content and decreasing the applied load. In conclusion, boron carbide is an effective reinforcement material in terms of tribological and mechanical performance of Al-B4C composites.
Invited Review
The effect of microstructure on corrosion behavior of ultra-high strength martensite steel-A literature review
Li Wang, Chao-fang Dong, Cheng Man, Ya-bo Hu, Qiang Yu, and Xiao-gang Li
Available online 19 December 2020, https://doi.org/10.1007/s12613-020-2242-6
[Abstract](392) [PDF 1899KB](25)
Abstract:
The ultra-high strength martensite steels are widely used in aerospace, ocean engineering, etc., due to their high strength, good ductility and acceptable corrosion resistance. This paper provides a review for the influence of microstructure on corrosion behavior of ultra-high strength martensite steels. Pitting is the most common corrosion type of ultra-high strength stainless steels, which always occurs at weak area of passive film such as inclusions, carbide/intermetallic interfaces. Meanwhile, the chromium carbide precipitations in the martensitic lath/prior austenite boundaries always result in intergranular corrosion. The precipitation, dislocation and grain/lath boundary are also used as crack nucleation and hydrogen traps, leading to hydrogen embrittlement and stress corrosion cracking for ultra-high strength martensite steels. Yet, the retained/reversed austenite has beneficial effects on the corrosion resistance and could reduce the sensitivity of stress corrosion cracking for ultra-high strength martensite steels. Finally, the corrosion mechanisms of additive manufacturing ultra-high strength steels and the ideas for designing new ultra-high strength martensite steel are explored.
Invited Review
Review on electrochemical degradation of phenolic compounds
You Xue, Xi Hu, Qian Sun, Hong-yang Wang, Hai-long Wang, and Xin-mei Hou
Available online 16 December 2020, https://doi.org/10.1007/s12613-020-2241-7
[Abstract](355) [PDF 1343KB](4)
Abstract:
Phenolic compounds are widely present in domestic sewage and industrial sewage and have serious environmental hazards. The electrochemical oxidation (EO) is demonstrated to be one of the most promising methods for the degradation of sewage due to its advantages of high efficiency, environmental compatibility, and safety. In this work, we present an in-depth overview of the mechanism and the factors affecting the degradation of phenolic compounds by EO. In particular, the effects of treating phenolic compounds with different anode materials are discussed in detail. It is found that the non-active anode shows higher degradation efficiency, less intermediate accumulation, and lower energy consumption than the active anode. EO combined other treatment methods (biological, photo, Fenton, etc.) present some advantages, such as low energy consumption and high degradation rate. Meanwhile, the remaining drawbacks of the electrochemical oxidation process as the phenolic compound treatment system have been discussed. Furthermore, to improve the feasibility of the practical application of EO technology, some future research directions are put forward.
Research Article
Superior corrosion resistance dependent laser energy density in (CoCrFeNi)95Nb5 high entropy alloy coating fabricated by laser cladding
Wen-rui Wang, Wu Qi, Xiao-li Zhang, Xiao Yang, Lu Xie, Dong-yue Li, and Yong-hua Xiang
Available online 12 December 2020, https://doi.org/10.1007/s12613-020-2238-2
[Abstract](383) [PDF 1426KB](13)
Abstract:
The (CoCrFeNi)95Nb5 high entropy alloy (HEA) coatings were successfully fabricated on the substrate of Q235 steel by laser cladding technology. These (CoCrFeNi)95Nb5 HEA coatings possess excellent properties, especially its corrosion resistance is obviously better than that of some typical bulk HEA and common engineering alloys. In order to obtain appropriate laser cladding preparation process parameters, the effects of laser energy density on the microstructure, microhardness and corrosion resistance of (CoCrFeNi)95Nb5 HEA coating were emphatically studied. As the laser energy density increases, the precipitation of Laves phase in (CoCrFeNi)95Nb5 HEA coating gradually decreases, and the diffusion of Fe element in the substrate intensifies, which affects the integrity of the (CoCrFeNi)95Nb5 HEA, resulting in the microhardness of (CoCrFeNi)95Nb5 HEA coatings decreasing. Moreover, the relative content of Cr2O3, Cr(OH)3, and Nb2O5 in the surface passive film of the coating decreases with the increasing of energy density, making the corrosion resistance decrease. This study demonstrates the controllability of high-performance HEA coating with laser cladding technology, which has certain guiding significance for laser cladding preparation of other CoCrFeNi-system HEA coatings.
Research Article
Mechanical properties and energy evolution of jointed rock specimens containing an opening under uniaxial loading
Peng Li, Mei-feng Cai, Pei-tao Wang, Qi-feng Guo, Sheng-jun Miao, and Fen-hua Ren
Available online 12 December 2020, https://doi.org/10.1007/s12613-020-2237-3
[Abstract](329) [PDF 866KB](5)
Abstract:
For investigating the impact of an opening and joints with different inclination angles on the mechanical response behavior, the energy evolution characteristics and distribution law of granite specimens, uniaxial loading tests were performed on the parallel jointed rock samples with an opening. The results indicate that there is a trend of first decreasing and then increasing of the strength and deformation parameters with the increase of inclination angle, reaching the minimum values when the inclination angle was 45°. The evolution curves of the elastic strain energy and dissipated energy with strain of the samples show the characteristics of step-like gradual mutation. The peak total energy, elastic strain energy, dissipated energy, and total input energy during the failure of the samples showed significant nonlinear characteristics with increasing inclination angle. The opening and joints as well as the change of the inclination angle had significant influences on the proportion of the elastic strain energy of the samples prior to the peak, resulting in the difference of the distribution law of input energy. Moreover, the energy mechanism of the sample failure was discussed, and the energy release was the internal cause of the sudden destruction of the entire rock mass.
Invited Review
Practical development and challenges of garnet-structured Li7La3Zr2O12 electrolytes for all solid-state lithium-ion battery—A review
Zao-hong Zhang, Tao Wei, Jia-hao Lu, Qi-ming Xiong, Yue-han Ji, Zong-yuan Zhu, and Liu-ting Zhang
Available online 12 December 2020, https://doi.org/10.1007/s12613-020-2239-1
[Abstract](747) [PDF 1371KB](45)
Abstract:
In order to achieve higher safety and higher energy density lithium-ion batteries, all solid-state lithium-ion batteries (ASSLIBs) have been widely studied. Recently, some review and experimental papers have focused on how to improve the ionic conductivity, stabilize the electrochemical performance and enhance the interface compatibility between the electrodes and the solid-state electrolytes (SSEs), including oxides, sulfides, composite electrolytes, gel electrolytes and so on. Among these SSEs, the garnet-structured Li7La3Zr2O12 (LLZO) is regarded as one of the most expected candidates for SSEs. However, numbers of challenges also exist for garnet-structured LLZO-based electrolytes, such as low ionic conductivity, indefinite cubic phase, poor interfacial compatibility with anodes/cathodes and so on, which urges us to explore effective solutions. Herein, we will review recent developments on garnet-structured LLZO and provide comprehensive insights to guide the development of garnet-structured LLZO electrolytes in this work. We will not only systematically and comprehensively discuss the following content, including preparation, element doping, the structure, stability, polymer-ceramic composite electrolytes (PCCEs) and interface improvement of LLZO, but also give a forward-looking perspective. We hope that it would provide meaningful guidance for the advanced solid garnet-electrolytes, and we think that the commercialization of ASSLIBs will be achieved in the near future.
Research Article
Interfacial bonding characteristics and mechanical properties of H68/AZ31B clad plate
Ting-ting Zhang, Wen-xian Wang, Jie Zhang, and Zhi-feng Yan
Available online 12 December 2020, https://doi.org/10.1007/s12613-020-2240-8
[Abstract](298) [PDF 2205KB](1)
Abstract:
Interfacial bonding, microstructures and mechanical properties of an explosively-welded H68/AZ31B clad plate were systematically studied. It was found that the bonding interface demonstrated a “like-wavy” structure containing three typical zones/layers: 1) diffusion layer adjacent to the H68 brass plate; 2) solidification layer of melted metals at the interface; and 3) a layer at the side of AZ31B alloy which experienced severe deformation. Mixed copper, CuZn2 and α-Mg phases were observed in the melted-solidification layer. Regular polygonal grains with twins were found at the H68 alloy side while fine equiaxed grains due to the recrystallization were found at the AZ31B alloy side near the interface. Nanoindentation results revealed the formation of brittle intermetallic CuZn2 phases at the bonding interface. The interface was bonded well through metallurgical reactions owing to the diffusion of Cu, Zn and Mg atoms across the interface and the metallurgic reaction of partially melted H68 and AZ31B alloys.
Research Article
Development of an improved CBR model for predicting steel temperature in LF refining
Fei Yuan, An-jun Xu, and Mao-qiang Gu
Available online 8 December 2020, https://doi.org/10.1007/s12613-020-2234-6
[Abstract](327) [PDF 628KB](6)
Abstract:
In the prediction of end-point molten steel temperature of LF, the influence of some factors is nonlinear. The prediction accuracy will be affected by directly inputting these nonlinear factors into the data-driven model. To solve this problem, an improved case-based reasoning model (CBR_HTC) was established through the nonlinear processing of these factors by calculating the heat transfer of the ladle with software Ansys. The results show that CBR_HTC model improves the prediction accuracy of end-point molten steel temperature by 5.33% and 7.00% compared to original CBR model, and 6.66% and 5.33% compared to BPNN model in the range of [-3,3] and [-7,7]. The MAE and RMSE values of CBR_HTC model are also lower. It is verified that the prediction accuracy of the data-driven model can be improved by coupling the mechanism model with the data-driven model.
Research Article
Tuning Li3PO4 modification on the electrochemical performance of nickel rich LiNi0.6Co0.2Mn0.2O2
Zhi-kun Zhao, Hui-lin Xie, Zi-yue Wen, Ling Liu, Bo-rong Wu, Shi Chen, Dao-bin Mu, and Chao-xiang Xie
Available online 28 November 2020, https://doi.org/10.1007/s12613-020-2232-8
[Abstract](375) [PDF 1840KB](9)
Abstract:
The surface deterioration occurs more and more easily in nickel-rich cathode material with the increase of nickel content. In order to prevent deterioration of active cathode materials and improve the electrochemical performance of nickel-rich cathode material simultaneously, the surface of nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode material is decorated with stable structure and conductive Li3PO4 by a facile method. The LiNi0.6Co0.2Mn0.2O2-1%wt.%, 2%wt.%, 3%wt.% Li3PO4 samples deliver high capacity retention of more than 85% after 100 cycles at 1C under high voltage of 4.5 V. The effect of different coating amount (0-5%wt.%) for LiNi0.6Co0.2Mn0.2O2 cathode is analyzed detailed and the better amount was 2wt.%. Detailed analysis of structure of the samples during the charge-discharge process is performed by in situ X-ray diffraction. It is indicated that the modification for LiNi0.6Co0.2Mn0.2O2 cathode could protect the well layered structure under the high voltages. In consequence, the electrochemical performance of modified samples is improved a lot.
Research Article
The effect of surface microstructure of arsenopyrite on the attaching behavior of Sulfobacillus thermosulfidooxidans in the presence of additional dissolved As(III)
Zhen Xue, Zhen-yuan Nie, Hong-chang Liu, Wei-bo Ling, Qian Pan, Jin-lan Xia, Lei Zheng, Chen-yan Ma, and Yi-dong Zhao
Available online 28 November 2020, https://doi.org/10.1007/s12613-020-2231-9
[Abstract](386) [PDF 1122KB](9)
Abstract:
The understanding of the bacterial adsorption and the evolution of biofilms on different surface structures of arsenopyrite is of great significance to clarify the mechanism of microbe-mineral interfacial interaction and the production of acidic mine drainage in the environment. In this study, the attachment of Sulfobacillus thermosulfidooxidans cells and biofilm formation on arsenopyrite with different surface structures in the presence of additional dissolved As(Ⅲ) were studied. The arsenopyrite slices with specific surface were obtained by electrochemical corrosion at 0.26 V. The scanning electronic microscopy-energy dispersion spectra (SEM-EDS) analyses indicated that the surface of arsenopyrite deficient in sulfur and iron obtained by electrochemical treatment wasn’t favorable for the initial adsorption of bacteria, and the addition of As(Ⅲ) inhibited the adsorption of microbial cells. The epifluorescence microscopy (EFM) results showed that the number of cells attaching on the arsenopyrite surface increased with time, however, when As(Ⅲ) was added, biofilm formation was delayed significantly.
Invited Review
Review and prospect of bioleaching in the Chinese mining industry
Sheng-hua Yin, Wei Chen, Xing-le Fan, Jia-ming Liu, and Li-bo Wu
Available online 28 November 2020, https://doi.org/10.1007/s12613-020-2233-7
[Abstract](448) [PDF 855KB](9)
Abstract:
As the second largest economy with a rapid economic growth, China has a huge demand for metals and energies. Production and consumption of several metals in China including copper, gold and rare earth elements (REEs) take the first place in the world in recent years. Bioleaching, an approach for low grade and refractory ores has been applied in industrial production, which makes great contributions to the development of Chinese mining industry. The exploration and application of bioleaching in China is reviewed in this study. Production and consumption of several metals in the past decade in China are introduced. Technological processes and main bioleaching operations in China, such as Zijinshan Copper Mine and Mianhuakeng Uranium Mine are presented. Current challenges of bioleaching operations in China are also introduced. Prospects including efficiency improvement and environmental protection are proposed as well according to current situation in the Chinese bioleaching industry.
Research Article
Quantitative evaluation of multi-process collaborative operation in steelmaking-continuous casting section
Jian-ping Yan, Qing Liu, Wei-da Guo, and Jun-guo Zhang
Available online 26 November 2020, https://doi.org/10.1007/s12613-020-2227-5
[Abstract](400) [PDF 1092KB](17)
Abstract:
The quantitative evaluation of multi-process collaborative operation is of great significance for the improvement of production planning and scheduling in steelmaking-continuous casting section (SCCS). Meanwhile, this evaluation is indeed difficult since it relies on an in-depth understanding of the operating mechanism of SCCS, and few existing methods can be used to conduct the evaluation due to lacking of full-scale consideration on multi-factor related to production operation. In this study, three quantitative models were developed, and evaluated the multi-process collaborative operation level through the laminar flow operation degree, the process matching degree and the scheduling strategy available degree, respectively. By using the evaluation models for the laminar flow operation and process matching levels, the production status of two steelmaking plants of A and B was investigated based on actual production data. The results indicate the average laminar flow operation (process matching) degrees of SCCS are 0.638 (0.610) and 1.000 (0.759) for Plants A and B in the period from April to July 2019. Then, a scheduling strategy based on the optimization of furnace-caster coordinating mode was suggested for Plant A. Simulation experiments showed its higher availability than the greedy-based and manual ones. After applying it, the average process matching degree of SCCS of Plant A increases by 4.6% in the period from September to November 2019. Its multi-process collaborative operation level has been improved with less adjustments and interrupts in casting.
Invited Review
Recovery and separation of rare earth elements by molten salt electrolysis
Tai-qi Yin, Yun Xue, Yong-de Yan, Zhen-chao Ma, Fu-qiu Ma, Mi-lin Zhang, Gui-ling Wang, and Min Qiu
Available online 26 November 2020, https://doi.org/10.1007/s12613-020-2228-4
[Abstract](478) [PDF 860KB](11)
Abstract:
With the increasing demand of rare earth metals on functional materials, recovery of rare earth elements (REEs) from secondary resources has become an imperative issue for the transition to a green economy. Molten salt electrolysis route has the advantages of low water consumption and low hazardous wastes during the REEs recovery process. In this review, we systematically summarize the separation and electroextraction of REEs on various reactive electrodes in different molten salts. The review also highlights the relationship between the formed alloy phases and the electrodeposition parameters including the applied potential, current and ion concentration. Moreover, we evaluate the feasibility of LiF–NaF–KF (FLiNaK) electrolyte on the basis of thermodynamics for alternative research to recover REEs. Problems related to REEs separation/recovery and the choice of electrolyte are discussed in detail to realize the low-energy and high current efficiency of practical applications.
Research Article
Graphene oxide wrapped magnetic nanoparticles composites induced by SiO2 coating with excellent regenerability
Zhong-liang Hu, Hou-quan Cui, Yan-huai Ding, Jing-ying Li, Yi-rong Zhu, and Zhao-hui Li
Available online 26 November 2020, https://doi.org/10.1007/s12613-020-2229-3
[Abstract](381) [PDF 824KB](2)
Abstract:
Graphene oxide (GO) wrapped Fe3O4 nanoparticles were prepared by coating the Fe3O4 nanoparticles (NPs) with SiO2 layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO2 coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. Effect of the amount of SiO2 on the morphology, structure, adsorption and regenerability of the composites was studied in detail. Results suggest that an appropriate SiO2 layer can effectively induce the GO nanosheets to completely wrap the Fe3O4 NPs, forming a core-shell Fe3O4@SiO2@GO composites where Fe3O4@SiO2 NPs were firmly encapsulated by GO nanosheets. As an adsorbent to remove Pb(II) cations from waste water, the optimized Fe3O4@SiO2@GO sample exhibits a high saturated adsorption capacity of 253 mg•g-1, and the adsorption process is well fitted by Langmuir adsorption model. Notably, it displays an excellent regeneration, maintaining ~90% adsorption capacity for 5 cycles, while other samples decrease their adsorption capacity rapidly. This work could provide a theoretical guidance to improve the regeneration of the GO based adsorbents.
Invited Review
Powder metallurgy of high-entropy alloys and related composites: A short review
Bo-ren Ke, Yu-chen Sun, Yong Zhang, Wen-rui Wang, Wei-min Wang, Pei-yan Ma, Wei Ji, and Zheng-yi Fu
Available online 11 November 2020, https://doi.org/10.1007/s12613-020-2221-y
[Abstract](745) [PDF 990KB](20)
Abstract:
High-entropy alloys (HEAs) have attracted more and more attentions because of the unique properties including high strength, hardness and chemical stability, good wear resistance and so on. Powder metallurgy is one of the most important methods to fabricate HEAs materials. This paper introduced the synthesis of HEAs powders and the consolidation of HEAs bulks. The phase transformation, microstructure evolution and mechanical properties of HEAs obtained by powder metallurgy were summarized. In addition, the HEAs-related materials such as Ceramic-HEAs cermets and HEAs-based composites fabricated by powder metallurgy were also included.
Research Article
Microstructure and mechanical properties of friction pull plug welding for 2219-T87 aluminum alloy with the tungsten inert gas weld
Zhen Shao, Lei Cui, Li-jun Yang, Peng Lu, Hui-miao Wang, Zhuan-ping Sun, and Jian-ling Song
Available online 11 November 2020, https://doi.org/10.1007/s12613-020-2222-x
[Abstract](475) [PDF 1595KB](4)
Abstract:
Friction pull plug welding (FPPW) of 2219-T87 Tungsten Inert Gas (TIG) welded joint was studied. The microstructures, precipitate evolution, mechanical properties, and fracture morphologies of the joint were analyzed and discussed. Defect-free joints were obtained by using 7,000 r/min rotational speed, 12 mm axial feeding displacement and 20–22 kN axial force. It was found that, within the welding parameters as mentioned above, metallurgical bonding between the plug and plate can be achieved by the formation of recrystallized grains. According to the different microstructural features, the FPPW joint can be divided into different regions, including such as heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), recrystallization zone, heat-affected zone in TIG weld (TIG-HAZ), and thermo-mechanically affected zone in TIG weld (TIG-TMAZ). In TIG-TMAZ, the grains were highly deformed and elongated owing to the shear and extrusion form the plug during FPPW process. The hardness distribution showed that TIG-TMAZ was the area with the lowest strength. The main reason of softening in TMAZ was identified as the dissolution of θ' and the coarsening of θ precipitate particles. In tensile test, the FPPW joint welded with 22 kN axial force showed the highest ultimate tensile strength of 237 MPa. The location of crack and facture was found in TIG-TMAZ. The fracture morphology of the tensile sample showed good plasticity and toughness.
Invited Review
Study of metallurgical process engineering
Rui-yu Yin
Available online 8 November 2020, https://doi.org/10.1007/s12613-020-2220-z
[Abstract](627) [PDF 2199KB](17)
Abstract:
After nearly one hundred years of exploration, recent metallurgy (metallurgical science and engineering) has gradually formed a framework system constructed by the integration of three levels of knowledge, namely 1) micro-metallurgy at the atomic/molecular level; 2) process metallurgy at the procedure/device level; 3) macro-dynamic metallurgy at the full process/process group level.For the development of macro-dynamic metallurgy, it must get rid of the concept of "isolated system" and establish the concepts of "flow", "process network", and "operating program" to study the "structure-function-efficiency" in the macro-dynamic operation of metallurgical manufacturing processes. It means that taking "flow" as the ontology and observing dynamic change by "flow" to solve the green and intelligent proposition of metallurgical enterprises.Metallurgical process engineering is the overall integrated metallurgy, top-level designed metallurgy, macro-dynamic operated metallurgy, engineering science level metallurgy.Metallurgical process engineering is a cross-level, comprehensive and integrated study of the macro and dynamic operation of manufacturing processes. It studies the physical nature and constitutive characteristics of the dynamic operation of steel manufacturing process, as well as the analysis-optimization of set of procedure functions, coordination-optimization of set of procedures’ relations, reconstruction-optimization of set of procedures in the manufacturing process. It establishes rules for the macro-operation of the manufacturing process, as well as the dynamic and precise objectives of engineering design and production operation.
Research Article
Wear behavior of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite with different stabilization treatments
Sheng Liu, Qing Yuan, Yu-tong Sima, Chen-xi Liu, Fang Han, and Wen-wei Qiao
Available online 4 November 2020, https://doi.org/10.1007/s12613-020-2217-7
[Abstract](478) [PDF 2041KB](4)
Abstract:
Zn-38Al-3.5Cu-1.2Mg composite reinforced by nano SiCp was fabricated by stirring assisted ultrasonic vibration. In order to improve the abrasive resistance of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite, several stabilization treatments with distinct solid solutions and aging temperatures were designed. The results indicate that the optimal stabilization treatment for the 38Al-3.5Cu-1.2Mg/SiCp composite involves a solution treatment at 380 °C for 6 h and aging at 170 °C for 48 h. The stabilization treatment leads to the formation of dispersive and homogeneous nano SiCp. During the friction wear condition, the nano SiCp limits the microstructure evolution from the hard α(Al, Zn) phase to the soft β(Al, Zn) phase. Besides, the increased amount of nano SiCp improves the grain dimension and contributes to abrasive resistance. Furthermore, the initiation and propagation of crack produced in the friction wear process are suppressed by the stabilization treatment, thereby improving the abrasive resistance of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite.
Research Article
Phase evolution and properties of glass ceramic foams prepared by bottom ash, fly ash and pickling sludge
Jun-jie Zhang, Xiao-yan Zhang, Bo Liu, Christian Ekberg, Shi-zhen Zhao, and Shen-gen Zhang
Available online 4 November 2020, https://doi.org/10.1007/s12613-020-2219-5
[Abstract](530) [PDF 1348KB](4)
Abstract:
Municipal solid waste incineration bottom ash (BA), fly ash (FA) and pickling sludge (PS), causing severe environmental pollution, were transformed into glass ceramic foams with the aid of CaCO3 as the pore-foaming agent by sintering in this paper. The effect of BA/FA ratio on the phase composition, pore morphology, pore size distribution, physical properties, glass structure unit of the samples was investigated, with results showing that with the increase of BA/FA ratio, the content of glass phase, Si-O-Si and Q3Si units decrease gradually. The glass transmission temperature of the mixture has also been reduced. These leads to the decrease of the glass viscosity, further causing bubble coalescence and uneven pore distribution. Glass ceramic foams with uniform spherical pores (average pore size of 106 μm) would be fabricated, when the content of BA, FA and PS were 35wt%, 45wt% and 20wt% respectively, contributing to the glass ceramic foams of high performance with bulk density of 1.76 g/cm3, porosity of 56.01% and compressive strength exceeding 16.23 MPa. This versatile and low-cost approach brings new insight of synergistically recycling solid wastes.
Research Article
Enhanced detection of ppb-level NO2 by uniform Pt-doped ZnSnO3 nanocubes
Yao-yu Yin, Yan-bai Shen, Si-kai Zhao, Ang Li, Rui Lu, Cong Han, Bao-yu Cui, and De-zhou Wei
Available online 21 October 2020, https://doi.org/10.1007/s12613-020-2215-9
[Abstract](714) [PDF 913KB](16)
Abstract:
ZnSnO3 nanocubes (ZSNCs) with various Pt concentrations (1at%, 2at%, and 5at%) were synthesized by the high-yield and facile one-pot hydrothermal method. The microstructures of the obtained products were characterized by XRD, FESEM, TEM, EDS and XPS. The results showed that the ZSNCs with perovskite structure are approximately 600 nm in side length, and this size was reduced to 400 nm after Pt doping. PtOx (PtO and PtO2) nanoparticle with the diameter of about 5 nm were uniformly coated on the surface of ZSNCs. NO2 sensing properties showed that 1% Pt-ZSNCs exhibited the highest response to NO2 than pure ZSNCs and Pt-ZSNCs with other Pt concentrations. The maximum response of 1 at% Pt-ZSNCs to 500 ppb NO2 was 16.0 at the optimal operating temperature of 125 °C, which was over 11 times higher than that of pure ZSNCs. The enhanced NO2 sensing mechanisms of Pt-ZSNCs were discussed in consideration of catalytic activities and chemical sensitization of Pt doping.
Research Article
Numerical simulation of flash reduction process in a drop tube reactor with variable temperature
Yi-ru Yang, Qi-peng Bao, Lei Guo, Zhe Wang, and Zhan-cheng Guo
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2210-1
[Abstract](685) [PDF 926KB](34)
Abstract:
A computational fluid dynamics (CFD) model was developed to accurately predicate the flash reduction process, which is considered to be an efficient alternative ironmaking process. Laboratory-scale experiments were conducted in drop tube reactors (DTRs) to verify the accuracy of the CFD model. The reduction degree of ore particles was selected as a critical indicator of model prediction, and the simulated and experimental results were in good agreement. The influencing factors, including the particle size (20–110 μm), peak temperature (1250–1550 °C), and reductive atmosphere (H2/CO), were also investigated. The height variation lines indicated that smaller particles (50 μm) had a longer residence time (3.6 s). CO provided a longer residence time (~1.29 s) compared with H2 (~1.09 s). However, both the experimental and analytical results show that the reduction degree of particles in CO atmosphere only reached 60%, significantly lower than that in H2 atmosphere, even at the highest temperature (1550 °C). The optimum experimental particle size and peak temperature for the preparation of high-quality reduced iron were found to be 50 μm and 1350 °C in H2 atmosphere and 40 μm and 1550 °C in CO atmosphere, respectively.
Research Article
Two refractory high-entropy alloys CrHfNbTaTi and CrHfMoTaTi: Phase, microstructure and compressive properties
Jiao-jiao Yi, Fu-yang Cao, Ming-qin Xu, Lin Yang, Lu Wang, and Long Zeng
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2214-x
[Abstract](703) [PDF 689KB](25)
Abstract:
Two new refractory high-entropy alloys, CrHfNbTaTi and CrHfMoTaTi, deriving from the well-known HfNbTaTiZr alloy by principal element substitutions, were prepared by vacuum arc-melting. Their phase components, microstructures, and compressive properties in the as-cast state were investigated intensively. The results showed that both alloys are mainly composed of a BCC and cubic laves phase. In terms of the mechanical properties, the yield strength increased remarkably from 926 MPa of HfNbTaTiZr to 1258 MPa of CrHfNbTaTi, meanwhile a promising ductility of around 24.3 % elongation was retained. The morphology and composition of the network-shape interdendritic regions were closely related to the improvement in mechanical properties deduced by elemental substitution. Whereas, dendritic surrounded by the incompact interdendritic shell at the case of the incorporation of Mo deteriorates the yield strength, and results in a typical brittle feature.
Research Article
Enhanced microstructural and mechanical properties of Stellite/WC nanocomposite on Inconel 718 deposited through vibration-assisted laser cladding
Hossein Hosseini-Tayeb and Seyed Mahdi Rafiaei
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2211-0
[Abstract](707) [PDF 1803KB](10)
Abstract:
Stellite-21/WC nanopowders were deposited on Inconel using vibration-assisted laser cladding through different laser parameters. To study about the microstructural and mechanical behaviors, optical and scanning electron microscopes, hardness measurements, and wear characterizations were employed. The results showed that the variation of cooling rate resulted in remarkable effects on the microstructure of the as-cladded composites. Moreover, increasing the laser power from 150 W to 250 W increased the heat input and the dilutions. Also, in the higher power of the laser (i.e. 250 W), dilution was affected by two factors that were scanning rate and powder feeding rate. Through the addition of WC nanoparticles as the reinforcement, the dilution magnitude intensified while the hardness value surprisingly increased from 350 to 700 HV. The wear characterizations indicated that the composites containing 3 wt% WC nanoparticles possessed the highest wear resistance.
Research Article
Special variation of infiltration-growth processed bulk YBCO fabricated using new liquid source: Ba3Cu5O8 (1:1.3) and YbBa2Cu3Oy
Miryala Sushma and Masato Murakami
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2213-y
[Abstract](856) [PDF 785KB](31)
Abstract:

The utilization of novel materials, high Tsuperconductors in particular, is essential in order to pursue the United Nations Sustainable Goals as well as the increasing worldwide demand for clean and carbon-free electric power technologies. Superconducting magnets have proven to be beneficial in several real-life applications such as transportation, energy production, MRI, drug delivery system etc. To achieve high performance, it is crucial to develop uniform large-grain infiltration-growth processed bulk YBa2Cu3Oy (Y-123) super-magnets. In this paper, we are reporting the magnetic and microstructural properties of large-grain top-seeded infiltration growth processed Y-123 pellet of 20 mm in diameter and 6 mm in height, produced utilizing the liquid Yb-123+Ba3Cu5O8 as liquid source. All samples cut at the top of the bulk have a sharp superconducting transition (~ 1 K wide) with the onset Taround 90 K. On the other hand, in the samples cut from the bottom surface, the onset Tvalues slightly decreased to values between 88 K and 90 K, still with a sharp superconducting transition. The top and bottom samples exhibited the highest remnant value of Jc at 77KH//c-axis of 50 kA/cm2 and 55 kA/cm2, respectively. The remnant Jc and irreversibility field values significantly fluctuated, being quite low in some bottom samples. Scanning electron microscopy (SEM) identified nanometer-size Y-211 secondary phase particles dispersed in the Y-123 matrix. The energy dispersive spectroscopy (EDS) clarified that the decreased critical temperature (Tc) and critical current density (Jc) for the bottom samples were due to liquid phase dispersion within Y-123 phase. 

Research Article
Effects of mechanical vibration on physical, metallurgical and mechanical properties of cast-A308 (LM21) aluminum alloy
Siddharth Yadav, S.P. Tewari, J.K. Singh, and S.C. Ram
Available online 14 October 2020, https://doi.org/10.1007/s12613-020-2209-7
[Abstract](769) [PDF 1556KB](14)
Abstract:
The present investigation deals with the improvement in microstructure, physical, and mechanical properties of die-cast A308 alloy subjected to mechanical vibration during solidification. The different frequencies (0, 20, 30, 40, and 50 Hz) at constant amplitude (31 μm) were employed using a power amplifier as the power input device. X-ray diffractometer, optical microscopy, and scanning electron microscopy were used to examine the morphological changes in the cast samples under stationary and vibratory conditions. Metallurgical features of castings were evaluated by ImageJ analysis software. The average values of metallurgical features, i.e., primary α-Al grain size, dendrite arm spacing (DAS), avg. area of eutectic silicon, aspect ratio, and percentage porosity were reduced by 34, 59, 56, 22, and 62% respectively at 30 Hz frequency compared to stationary casting. The mechanical tests of cast samples showed that yield strength, ultimate tensile strength, elongation, and microhardness were increased by 8, 13, 17, and 16%, respectively, at 30 Hz frequency compared to stationary casting. The fractured surface of tensile specimens exhibited mixed-mode fracture behavior due to the appearance of brittle facets, cleavage facets, ductile tearing, and dimple morphologies. The presence of small dimples showed some plastic deformation occurred before fracture.
Research Article
Influence of polymer solution on the morphology and local structure of NH4ZnPO4 powders synthesized by a simple precipitation method at room temperature
Santi Phumying, Thongsuk Sichumsaeng, Pinit Kidkhunthod, Narong Chanlek, Jessada Khajonrit, Somchai Sonsupap, and Santi Maensiri
Available online 13 October 2020, https://doi.org/10.1007/s12613-020-2208-8
[Abstract](630) [PDF 1416KB](12)
Abstract:
In this work, NH4ZnPO4 powders were synthesized by a simple precipitation method at room temperature. The effect of PVP, PVA, sucrose and CTAB solution on the morphology and structure of the prepared samples was investigated. The phase composition and morphology of the prepared samples were characterized by using X-ray diffraction and scanning electron microscopy, respectively. Depending on the polymer sources, the hexagonal structure prepared by using non-surfactant of water completely changed to monoclinic structure when CTAB was added into the process. X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) was used to study the local structure and surface electronic structure of the prepared samples confirming that the oxidation states of P and Zn ions are 5+ and 2+, respectively. By using ICP-OES technique, our NH4ZnPO4 powders can be classified as a slow-release fertilizer where less than 15% of the ions was released in 24 h. This study shows that a simple precipitation method using water, PVP, PVA, sucrose and CTAB as a template can be used to synthesize NH4ZnPO4 powders. In addition, this method may be extended for the preparation of other oxide materials.
Research Article
Microstructure analysis and mechanical properties of reaction-bonded B4C-SiC composites
Rong-zhen Liu, Wen-wei Gu, Yu Yang, Yuan Lu, Hong-bin Tan, and Jian-feng Yang
Available online 7 October 2020, https://doi.org/10.1007/s12613-020-2207-9
[Abstract](660) [PDF 1038KB](11)
Abstract:
Reaction-bonded B4C-SiC composites are highly promising materials for many advanced technological applications. However, their microstructure evolution mechanism remains unclear. Herein, B4C-SiC composites were fabricated by the Si melt infiltration process. The influence of sintering time and B4C content on the mechanical properties, microstructure, and phase evolution were investigated. X-ray diffraction results showed the presence of SiC, boron silicon, boron silicon carbide, and boron carbide. Scanning electron microscopy results showed that with the increasing of boron carbide addition, the amount of Si content decreased and the amount of unreacted B4C increased. Unreacted B4C diminished with increasing sintering time and temperature. The further microstructure analysis showed a transition area between B4C and Si, with a C concentration marginally higher in the transition area than in the Si area. It indicates that after the silicon infiltration,diffusion mechanism is the primary sintering mechanism of the composites. As the diffusion process progresses, the hardness increases. The maximum values of the Vickers hardness, flexural strength, and fracture toughness of the reaction bonded B4C/SiC ceramic composite with 12wt% B4C content sintered at 1600℃ for 0.5 h are 2600 HV, 330 MPa, and 5.2 MPa·m0.5, respectively.
Research Article

Oxidation behavior of a high Hf nickel-based superalloy in air at 900, 1000 and 1100°C


Jiu-han Xiao, Dong Wang, Li Wang, Xiang-wei Jiang, Kai-wen Li, Jia-sheng Dong, and Lang-hong Lou
Available online 1 October 2020, https://doi.org/10.1007/s12613-020-2204-z
[Abstract](1235) [PDF 1256KB](18)
Abstract:
In order to investigate the oxidation behavior of a nickel-based superalloy containing high hafnium content (1.34 wt%), isothermal oxidation tests were performed at 900, 1000 and 1100°C for up to 200 h. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) were applied to study the oxidation behavior. Weight gain of the experimental superalloy exhibits a parabola-like curve and no spallation of the oxide scale was observed in the oxidation tests. The alloy presents excellent oxidation resistance and no HfO2 is observed in the oxide scale at 900°C. Elevating the oxidation temperature up to 1000°C, HfO2 particles form in the spinel phases of the scale, and “pegs” HfO2 is observed within and beneath the inner layer of Al2O3 after 200 hours. As the oxidation temperature elevated to 1100°C, “pegs” HfO2 is observed at the early stage of oxidation test (within 25 hours). Formation mechanism of HfO2 and the impact on oxidation resistance are investigated based on the analysis of oxidation tests results at different temperatures.
Research Article
The activity coefficient of nickel oxide in SiO2 saturated MnO-SiO2 slag and Al2O3 saturated MnO-SiO2-Al2O3 slag at 1623K
Guo-xing Ren, Song-wen Xiao, Cai-bin Liao, and Zhi-hong Liu
Available online 1 October 2020, https://doi.org/10.1007/s12613-020-2205-y
[Abstract](1127) [PDF 620KB](33)
Abstract:
As a part of the fundamental study related to the reduction smelting of both spent lithium-ion batteries and polymetallic sea nodules based on MnO-SiO2-based slags, the activity coefficient of nickel oxide in SiO2 saturated MnO-SiO2 slag and Al2O3 saturated MnO-SiO2-Al2O3 slag at 1623 K was investigated with controlled oxygen partial pressure of 10-7, 10-6, and 10-5 Pa. The results show that the solubility of nickel oxide in the slags increased with increasing the oxygen partial pressure. The nickel in both MnO-SiO2 slag and MnO-SiO2-Al2O3 slag existed as NiO under experimental conditions. The addition of Al2O3 in the MnO-SiO2 slag decreased the dissolution of Ni in the slag, and increased the activity coefficient of NiO. Furthermore, the activity coefficient of NiO, referred to solid NiO, can be calculated as: γNiO=8.58(wt% NiO in slag) + 3.18 (SiO2 saturated MnO-SiO2 slag, 1623K);γNiO=11.06(wt% NiO in slag) + 4.07 (Al2O3 saturated MnO-SiO2-Al2O3 slag, 1623K).
Research Article
Parametric study of spark plasma sintering of Al20Cr20Fe25Ni25Mn10 high entropy alloy with improved microhardness and corrosion
Andries Mthisi, Nicholus Malatji, A. Patricia I. Popoola, and L. Rudolf Kanyane
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2200-3
[Abstract](1085) [PDF 1157KB](20)
Abstract:
Multicomponent Al20Cr20Fe25Ni25Mn10 alloys were synthesized using spark plasma sintering at temperatures (800 °C, 900 °C and 1000 °C) and holding times (4, 8 and 12 minutes), with aim to develop a high entropy alloy (HEA). The characteristics of spark plasma synthesized (SPSed) alloys were experimental explored through investigation of microstructures, microhardness and corrosion using scanning electron microscope coupled with energy dispersive spectroscopy, Vickers microhardness tester and potentiodynamic polarization respectively. Also, X-ray diffractometry characterization was employed to identify the phases formed on the alloys developed. The EDS results revealed that the alloys consist of elements selected in this work irrespective of varying the sintering parameters. Also, the XRD, EDS and SEM collectively provided evidence that the fabricated alloys are characterized by globular microstructures exhibiting FCC phase formed on a basis of solid solution mechanism; this implies that SPSed alloy shows features of HEAs. The alloy produced at 1000 °C and holding time 12 minutes portrayed an optimal microhardness of 447.97 HV, however, this microhardness decreased to 329.47 HV after heat treatment. The same alloy showed outstanding corrosion resistance performance. Increase in temperature resulted in Al20Cr20Fe25Ni25Mn10 alloy with superior density, microhardness and corrosion resistance over other alloys developed at different parameters.
Research Article
Effect of cermet substrates characteristics on the microstructure and properties of TiAlN coating
Qian-bing You, Ji Xiong, Tian-en Yang, Tao Hua, Yun-liang Huo, and Jun-bo Liu
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2198-6
[Abstract](1091) [PDF 2398KB](30)
Abstract:
The composition and structure of substrate material have an important influence on the coating performances, especially the bonding strength and coating hardness,which determines whether the coating can be used. In the paper, the TiAlN coating was deposited on the TC with 0-20wt.% WC by arc ion plating. The influence of cermet substrates characteristics on the structure and properties of TiAlN coating was researched. The results show that TiAlN coating deposited on TC substrates has columnar grain structure. With the increasing of WC, the strength ratio of I(111)/I(200) of TiAlN and the adhesion gradually increases. When there is no WC in the substrate, the preferred orientation of TiAlN coating is (200). As the contents of WC go up, the preferred orientation of TiAlN coating becomes (111) and (200). The biggest difference between the adhesion strength of coating and substrate is the microstructure and composition of the substrate. Scratching results show that the adhesion of TiAlN coating gradually increases from A1 to A5 respectively 53N, 52 N, 56 N, 65 N, 58 N. The coating on the TC substrate with 15wt.% WC has the highest H/E and H3/E2, which indicating the best wear resistance. The failure mechanisms of coated tools are coating peeling, adhesive wear, and abrasive wear. As the cutting speed increases, the amount ofthe flank wear increases, and the durability decreases accordingly. Accompanied by the increasing of WC, the flank wear of coated cermet insert decreases first and then increases. 
Research Article
Effect of graphene-oxide on corrosion, mechanical and biological properties of Mg-based nanocomposite
Saeid Jabbarzare, Hamid Reza Bakhsheshi-Rad, Amir Abbas Nourbakhsh, Tahmineh Ahmadi, and Filippo Berto
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2201-2
[Abstract](1171) [PDF 2126KB](25)
Abstract:
The purpose of this paper is to investigate the role of graphene oxide (GO) on mechanical and corrosion behaviors, antibacterial performance, and cell response of Mg-Zn-Mn (MZM) composite. MZM/GO nanocomposites were made with various amounts of GO (0.5, 1.0, and 1.5 wt.%) by the semi powder metallurgy method. The GO influence on the MZM composite was analyzed by hardness, compressive and corrosion tests, and antibacterial and cytotoxicity tests. According to the experimental results, increasing the GO amount increased hardness values, compressive value, and antibacterial performance of the MZM composite, while cell viability and osteogenesis level presented reversed trends. It was shown, based on the electrochemical examination, which the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation of 0.5 wt.% GO. Taken together, the antibacterial and mechanically MZM nanocomposites reinforced with GO to be used for implant applications.
Research Article
Effect of cathodic potential on stress corrosion cracking behavior of 21Cr2NiMo steel in simulated seawater
Meng-hao Liu, Zhi-yong Liu, Cui-wei Du, Xiao-qin Zhan, Chun-duo Dai, Yue Pan, and Xiao-gang Li
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2199-5
[Abstract](1093) [PDF 2930KB](3)
Abstract:
This study aims at providing systematically insights into the impact of cathodic polarization on the stress corrosion cracking (SCC) behavior of 21Cr2NiMo steel. Slow stress tensile test demonstrated that 21Cr2NiMo steel is highly sensitive to hydrogen embrittlement at strong cathodic polarization. The lowest SCC susceptibility is presented at -775 mVSCE whereas the SCC susceptibility increased remarkably below -950 mVSCE. SEM and EBSD revealed that cathodic potential decline causes a transition in fracture path from transgranular mode to intergranular mode. The intergranular mode transforms from bainite boundaries separation to prior austenitic grain boundaries separation when more cathodically polarized. Furthermore, corrosion pits promoted the nucleation of SCC cracks. In conclusion, the SCC mechanism transforms from the coexistence of hydrogen embrittlement mechanism and anodic dissolution mechanism to typical hydrogen embrittlement mechanism with applied potential decreases.
Research Article
Microstructure and tribological behavior of the nickel-coated-graphite reinforced Babbitt metal composite fabricated by selective laser melting
Xing-ke Zhao and Xu-sheng Hai
Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2195-9
[Abstract](1154) [PDF 1740KB](4)
Abstract:
For purpose of improving the properties of Babbitt alloys, Ni-coated-graphite reinforced Babbitt metal composite specimens were prepared by selective laser melting (SLM) process, and their microstructures, mechanical and tribological properties were studied using scanning electron microscope (SEM), shear test and dry-sliding wear test, respectively. The results show that most of NCGr particles distribute at boundaries of laser beads in the cross-section of the SLM composite specimens. Microcracks or microvoids form at boundaries of laser beads where NCGr particle accumulating. Both shearing strength and the friction coefficient of the SLM composite specimens decrease with increasing NCGr content. The shearing strength and the friction coefficient of the SLM composite sample with 6% NCGr decrease by around 20% and 33% compared with the NCGr-free sample. Friction mechanism changes from plastic shaping furrow to brittle cutting with increasing NCGr content. A practical Babbitt material with a lower friction coefficient and proper strength could be expected if the dispersion of the NCGr particles is controlled by choosing NCGr particles with thicker Ni layer and precisely controlling laser energy input during SLM process.
Research Article
Experimental study on flow zone distribution and mixing time in a Peirce-Smith copper converter
Hong-liang Zhao, Jing-qi Wang, Feng-qin Liu, and Hong Yong Sohn
Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2196-8
[Abstract](1136) [PDF 623KB](39)
Abstract:
Peirce-Smith copper converting involved complex multiphase flow and mixing. In this work, the flow zone distribution and the mixing time in a copper PSC were investigated in a 1:5 scaled cold model. Flow field distribution including dead, splashing and strong-loop zones were measured and a dimensionless equation was developed to correlate the effects of stirring and mixing energy with an error less than 5%. Four positions in the bath including injection, splashing, strong-loop and dead zones were selected to add the hollow salt powders tracer and measure the mixing time. The injection of the quartz flux through the tuyeres or into the backflow point of the splashing wave through a chute is recommended, instead of adding it through a crane hopper from the top of the furnace, to improve the slag-making reaction.
Research Article
Effects of Si/Al, Na/Al, and H2O/Na2O molar ratios on formaldehyde barrier properties of inorganic aluminosilicate coatings
Shan-xia Xiong, Jian-lei Kuang, Qian-fang Zheng, Ting Xiao, Wen-xiu Liu, Qi Wang, Peng Jiang, and Wen-bin Cao
Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2197-7
[Abstract](1100) [PDF 927KB](4)
Abstract:
Wood-based panels containing urea-formaldehyde resin result in the long-term release of formaldehyde and threaten human health. To obstruct formaldehyde release, inorganic aluminosilicate coatings prepared by combining metakaolin, silica fume, NaOH and H2O, were applied to the surfaces of wood-based panels. The Si/Al, Na/Al, and H2O/Na2O molar ratios of the coatings were regulated to investigate their effects on the structure and formaldehyde-resistant barrier properties of coatings. The results showed that as the Si/Al molar ratio increased from 1.6 to 2.2, the cracks present in the coatings gradually disappeared and the formaldehyde-resistance rates of the barrier increased. This value also increased as the Na/Al molar ratio increased from 0.9 to 1.2 due to the improvement of the degree of polymerization. As the H2O/Na2O molar ratio increased from 12 to 15, the thickness of the dry film decreased gradually and led to the reduction in the formaldehyde-resistance rate. When the Si/Al, Na/Al and H2O/Na2O molar ratio were 2.2, 1.2, and 12 respectively, the inorganic aluminosilicate coating showed the good performance as a formaldehyde-resistant barrier and its formaldehyde-resistance rate could reach up to 83.2%.
Invited Review
Iron and steel metallurgy—Ongoing challenges
Dieter Senk
Available online 12 September 2020, https://doi.org/10.1007/s12613-020-2191-0
[Abstract](1328) [PDF 1427KB](44)
Abstract:
Iron and steel making lasts for several thousand years and is based on changing technologies. The driving forces for those changes are economical or disposability of raw material and energy sources. In this paper three challenges for the newly development in iron and steel metallurgy are highlighted: Continuous casting strand size increase, solidification behaviour of new steel grades, and suppression of CO2-emission during iron making. Examples underline the recent process of technological changes. 40 years of Sino German university cooperation in metallurgy are part of those technological development.
Research Article
The stress corrosion cracking behavior of high-strength mooring chain steel in SO2-polluted coastal atmosphere
Meng-hao Liu, Zhi-yong Liu, Cui-wei Du, Xiao-qin Zhan, Xiao-jia Yang, and Xiao-gang Li
Available online 12 September 2020, https://doi.org/10.1007/s12613-020-2192-z
[Abstract](1259) [PDF 2645KB](3)
Abstract:
21Cr2NiMo steel is widely used to stabilize offshore oil platforms, however, it suffers from stress corrosion cracking (SCC). Herein, we studied the SCC behavior of 21Cr2NiMo steel in SO2-polluted coastal atmospheres. Electrochemical tests revealed that the addition of SO2 increases the corrosion current. Rust characterization showed that the SO2 addition densities the corrosion products and promotes pitting. Furthermore, the slow strain rate tests demonstrated high susceptibility to SCC at high SO2 contents. Fracture morphologies revealed that the stress-corrosion cracks initiated at corrosion pits and the crack propagation showed transgranular and intergranular cracking modes. In conclusion, the SCC is mix-controlled by anodic dissolution and hydrogen embrittlement mechanisms.
Research Article
Synthesis, characterization and magnetic properties of KFeO2 nanoparticles prepared by a simple egg-white solution route
Thongsuk Sichumsaeng, Nutthakritta Phromviyo, Supree Pinitsoontorn, Pinit Kidkhunthod, Narong Chanlek, and Santi Maensiri
Available online 12 September 2020, https://doi.org/10.1007/s12613-020-2194-x
[Abstract](1236) [PDF 2541KB](10)
Abstract:
In this work, nanoparticles of potassium ferrite (KFeO2) were synthesized by a simple egg-white solution method upon calcination in air at different temperatures of 500, 600, and 700ºC for 2 h. The effects of calcination temperature on structural and magnetic properties of the synthesized KFeO2 nanoparticles were investigated. By varying the calcination temperature, X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated the changes of crystallinity and morphology including particle size, respectively. Significantly, the reduction of particle size of the synthesized KFeO2 was found to have a great influence on the magnetic properties. At room temperature, the synthesized KFeO2 nanoparticles prepared at 600ºC exhibited the highest saturation magnetization (MS) of 26.24 emu•g-1. In addition, the coercivity (HC) increased from 3.51 to 16.89 kA•m-1 with increasing calcination temperature up to 700ºC. The zero-field-cooled (ZFC) results showed that the blocking temperatures (TB) of about 125 and 85 K were observed in the samples calcined at 500 and 600ºC, respectively. Therefore, this work shows that the egg-white solution method is a simple, cost effective, and environmental-friendly for the preparation of KFeO2 nanoparticles.
Research Article
Kinetically controlled synthesis of atomically precise silver nanocluster for catalytic reduction of 4-nitrophenol
Xian-hu Liu, Fei-hong Wang, Cong-ying Shao, Gang-feng Du, and Bing-qing Yao
Available online 5 September 2020, https://doi.org/10.1007/s12613-020-2186-x
[Abstract](1325) [PDF 1082KB](30)
Abstract:
It is challenging to synthesize atom-precise silver nanoclusters (NCs), which is essential for the development of NCs. In this study, we report the synthesis of atom-precise silver NCs in high purity by a kinetically controlled strategy. The silver NCs were prepared using a mild reducing agent via a one-pot method. The as-prepared silver NCs were confirmed to be Ag49(D-pen)24 (D-pen: D-penicillamine) based on the discussion of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and thermogravimetry (TG) characterizations. Interface structures of the silver NCs were illustrated by both 1H-NMR and FTIR spectroscopy. The silver NCs were supported on the active carbon (AC) to form the Ag NCs/AC which displayed excellent activity for the catalytic reduction of 4-nitrophenol with the kinetic reaction rate constant k of 0.21 min−1, outperforming several catalysts reported previously. Besides, the catalytic activity of Ag NCs/AC kept almost constant after six times of recycle, suggesting its good stability.
Research Article
Multi-objective collaborative optimization of metallurgical properties of iron carbon agglomerates using response surface methodology
Ji-wei Bao, Man-sheng Chu, Zheng-gen Liu, Dong Han, Lai-geng Cao, Jun Guo, and Zi-chuan Zhao
Available online 5 September 2020, https://doi.org/10.1007/s12613-020-2188-8
[Abstract](1248) [PDF 1301KB](18)
Abstract:
Iron carbon agglomerates (ICA) is considered to be an innovative charge to realize low carbon blast furnace (BF) ironmaking. In this study, the central composite Design (CCD) based on response surface methodology (RSM) was used to synergistically optimize the compressive strength, reactivity and post-reaction strength of ICA. The results show that the iron ore ratio has the most significant influence on compressive strength, reactivity and post-reaction strength. There are significant interactions on the compressive strength and reactivity between the iron ore ratio and carbonization temperature or the iron ore ratio and carbonization time, while the three variables do not interact with each other on the post-reaction strength. In addition, the optimal process parameters are iron ore ratio of 15.30%, carbonization temperature of 1000℃ and carbonization time of 4.27 h, and the model prediction results of compressive strength, reactivity and post-reaction strength are 4026 N, 55.03% and 38.24% respectively, which are close to the experimental results and further verifies the accuracy and reliability of the models.
Research Article
Effect of graphene addition on physico-mechanical and tribological properties of Cu-nanocomposites
Adnan I. Khdair and A. F. Ibrahim
Available online 5 September 2020, https://doi.org/10.1007/s12613-020-2183-0
[Abstract](1270) [PDF 731KB](29)
Abstract:
This paper presents experimental investigation of the mechanical and tribological properties of Cu-GNs nanocomposites. We employed electroless coating process to coat GNs with Ag particles to avoid their reaction with Cu and formation of intermetallic phases. We studied the effect of GNs content on structural, mechanical and tribological properties of the produced nanocomposites. The results showed that the coating process is an efficient technique to avoid reaction between Cu and C and the formation intermetallic phases. The addition of GNs should be done wisely since the mechanical and tribological properties improved with increasing GNs up to a certain threshold values. The optimum GNs proved is 0.5%, at which hardness, wear rate and coefficient of friction are improved by 13%, 81.9% and 49.8%, respectively, compared to Cu- nanocomposite. These improved properties are due to the reduced crystallite size, presence of GNs and homogenous distribution of constituents.
Research Article
Effect of Al2O3 on the viscosity of CaO-SiO2-Al2O3-MgO-Cr2O3 slags
Chen-yang Xu, Cui Wang, Ren-ze Xu, Jian-liang Zhang, and Ke-xin Jiao
Available online 5 September 2020, https://doi.org/10.1007/s12613-020-2187-9
[Abstract](1318) [PDF 565KB](16)
Abstract:
The effect of Al2O3 on the viscosity of the CaO-SiO2-Al2O3-8wt% MgO-1wt% Cr2O3 (CaO/SiO2=1.0, Al2O3=17-29wt%) slags was investigated in the present work. The results indicated that the viscosity of the slag increased gradually with the increasing of Al2O3 content within the range of 17 to 29wt%, due to the role of Al2O3 acting as a network former in polymerizing the aluminosilicate structure of the slag. The apparent activation energy of the slags increased from 180.85 to 210.23 kJ/mol with increasing the Al2O3 content from 17 to 29wt%, which was consistent with the variation of the critical temperature. It was indicated that the polymerization degree of the present slag was increased with the addition of Al2O3. The Iida’s model was applied to the prediction of the slag viscosity due to the existence of Cr2O3, and it was found that the calculated viscosity values fitted well with the measured ones when both of the temperature and Al2O3 content were at relatively low level in the present study.
Research Article
Fabrication of green one-part geopolymer from silica-rich vanadium tailing via thermal activation and modification
Shen-xu Bao, Yong-peng Luo, and Yi-min Zhang
Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2182-1
[Abstract](1416) [PDF 1405KB](24)
Abstract:
The aim of this investigation is to prepare geopolymeric precursor using vanadium tailing (VT) by thermal activation and modification. The homogeneous blend of VT and sodium hydroxide is calcinated at elevated temperature for activation and then was modified with metakaolin to assemble geopolymeric precursor. During the thermal activation, the VT is corroded by sodium hydroxide, and then forms sodium silicate on the particles surface. After water is added, the sodium silicate coating is dissolved to release silicon species and create alkaline solution environment, and then the metakaolin dissolved in the alkaline environment to provide aluminum species, followed by geopolymerization. Meanwhile, the VT particles are connected together by gel produced from geopolymerization, resulted in geopolymer with excellent mechanical performance. This investigation not only improves the feasibility of geopolymer technology in large-scale and in-situ applications, but also benefits the utilization of VT and other silica-rich solid wastes.
Research Article
Research on fractal and microscopic quantitative characterization of unclassified tailings flocs
Di Zheng, Wei-dong Song, Yu-ye Tan, Shuai Cao, Zi-long Yang, and Li-juan Sun
Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2181-2
[Abstract](1356) [PDF 1588KB](26)
Abstract:
In this paper, a series of laboratory investigations are carried out to explore the effect of flocculant type on the spatial morphology and microstructural characteristics of flocs in the flocculation and settling of tailings. Four types of flocculants (ZYZ, JYC-2, ZYD and JYC-1) are considered in this study. The fractal characteristics and internal structure of tailings flocs with different flocculant types and settlement heights are analyzed through scanning electron microscopy (SEM) and X-ray microtomography (μCT) scanning experiments based on fractal theory. Results show that unclassified tailings flocs are irregular clusters with fractal characteristics, and the flocculation effect of flocculants has the following trend: ZYZ > JYC-2 > ZYD > JYC-1. The size and the average gray value of tailings flocs decrease as the settlement height decreases. The average gray values at the top and bottom are 144 and 103, respectively. The settlement height remarkably affects the pore distribution pattern, as revealed in the constructed three-dimensional pore model of tailings flocs. The upper part of the flocs has good penetration, while the bottom part is mostly dispersed pores. The number of pores increases exponentially as the settlement height increases, whereas their size initially increases and then decreases as settlement height increases.
Research Article
3D graphitic carbon sphere foams as sorbents for cleaning oil spills
Sai-sai Li, Hai-jun Zhang, Long-hao Dong, Hai-peng Liu, Quan-li Jia, and Dong Xu
Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2180-3
[Abstract](1290) [PDF 737KB](8)
Abstract:
Frequent offshore oil spill accidents, industrial oily sewage and the indiscriminate disposal of urban oily sewage have caused serious impacts on human living environment and health. The traditional oil-water separation methods not only cause easily environmental secondary pollution, but also waste of limited resources. Therefore, in this work, 3D graphitic carbon sphere foams (3D-foams) possessed three-dimensional porous structure with pore size distribution of 25~200 μm, and high porosity of 62% were prepared for oil adsorption via foam-gel casting method using graphitic carbon spheres as starting materials. The resulted indicated that the water contact angle of as-prepared 3D-foams was 130°. The contents of graphitic carbon spheres (GCS) greatly influenced the hydrophobicity, water contact angle (WCA) and microstructure of the as-prepared samples. The adsorption capacities of as-prepared 3D-foams for paraffin oil, vegetable oil and vacuum pump oil were about 12~15 g/g, which were 10 times of that graphitic carbon spheres powder.
Research Article
Process-structure-property relationship for plasma sprayed iron based amorphous-crystalline composite coatings
Abhishek Pathak, Biswajyoti Mukherjee, Krishna Kant Pandey, Aminul Islam, Pavan Bijalwan, Monojit Dutta, Atanu Banerjee, and Anup Kumar Keshri
Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2171-4
[Abstract](1480) [PDF 1233KB](43)
Abstract:
The present study explores the fabrication of Fe-based amorphous coating by air plasma spraying and its dependency on the coating parameters (plasma power, primary gas flow rate, stand-off distance and powder feed rate). XRD of the coatings deposited at optimized spray parameters showed the presence of amorphous-crystalline phase. Coatings deposited at lower plasma power and moderate gas flow rate exhibited better density, hardness and wear resistance. All coatings demonstrated equally good resistance against corrosive environment (NaCl). Mechanical, wear and tribological studies indicate that a single process parameter optimization cannot provide good coating performance but instead, all process parameters are having their unique role in defining better properties to the coating by controlling the in-flight particle temperature and velocity profile followed by the cooling pattern of molten droplet before impingement on the substrate.
Research Article
Separation of tungsten and molybdenum with solvent extraction using functionalized ionic liquid tricaprylmethylammonium bis(2,4,4-trimethylpentyl) phosphinate
Fei Cao, Wei Wang, De-zhou Wei, and Wen-gang Liu
Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2172-3
[Abstract](1240) [PDF 474KB](7)
Abstract:
Functionalized ionic liquids (FILs) as extractants were employed for the separation of tungsten and molybdenum from a sulfate solution for the first time. The effects of initial pH, extractant concentration, metal concentrations in the feed, etc., were investigated in detail. The results showed that tricaprylmethylammonium bis(2,4,4-trimethylpentyl)phosphinate ([A336][Cyanex272]) could selectively extract W over Mo at an initial pH of 5.5, and the best separation factor βW/Mo of 25.61 was obtained for a solution with low metal concentrations (WO3: 2.49 g/L, Mo: 1.04 g/L). The [A336][Cyanex272] system works well for solutions of different W/Mo molar ratios and different concentrations of metal ions in the feed. The chemical reaction between [A336][Cyanex272] and W followed the ion association mechanism, which was further proven by the FTIR spectra of loaded [A336][Cyanex272] and free extractant. The stripping experiments indicated that 95.48% W and 100.00% Mo were stripped by a 0.20 mol/L sodium hydroxide solution. Finally, selective extraction of W from Mo was obtained for two synthetic solutions of different high metal concentrations, and the separation factor βW/Mo reached 23.24 and 17.59, respectively. The results suggested the feasibility of [A336][Cyanex272] as an extractant for the separation of tungsten and molybdenum.
Research Article
Tunable fabrication of single-crystalline CsPbI3 nanobelt and its application as photodetectors
Tao Yang, Ya-peng Zheng, Kuo-Chih Chou, and Xin-mei Hou
Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2173-2
[Abstract](1128) [PDF 866KB](13)
Abstract:
Recently, lead halide perovskites have received much attention and be a candidate material for various optoelectronic field for their high performance as light absorbers. Here we report the growth of CsPbI3 nanoblet via a solution process. The single-crystalline CsPbI3 nanobelt have a high yield with uniform in morphology by controlling the PbI2 amount. The single-crystalline CsPbI3 nanobelt possess a mean width, length and thickness of 100 nm, 5 µm and 20 nm respectively. Based on this, the photodetectors (PDs) based on individual CsPbI3 nanobelt were constructed and have a good performance with an external quantum efficiency and responsivity of 2.39×105 % and 770 A·W-1, respectively. More importantly, the PDs show a high detectivity up to 3.12×1012 Jones, which is on par with that of Si PDs. It exhibits as a promising candidate applied in various optoelectronic nanodevices.
Research Article
Interface behavior of chalcopyrite during flotation from cyanide tailings
Xue-min Qiu, Hong-ying Yang, Guo-bao Chen, Lin-lin Tong, Zhe-nan Jin, and Qin Zhang
Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2170-5
[Abstract](1300) [PDF 1042KB](14)
Abstract:
Interface characteristics of cyanide tailings are very different compared with those of raw ore. Valuable elements could not be comprehensively recovered via flotation from cyanide tailings originating from Shandong province, China. Herein, the interface and floatability of these tailings were investigated. The chalcopyrite in the cyanide tailings investigated herein was fine with a porous surface. The floatability of 68% chalcopyrite was similar to galena in the presence of a collector. This part of chalcopyrite was compactly wrapped in a layer of fine galena particles. The recovery of chalcopyrite sharply decreased as the nonpolar oil residue in cyanide tailings was removed through alcohol extraction; however, this removal had no effect on galena. The other chalcopyrite in the flotation tailings was covered with an oxidation layer consisting of O, Fe, S, Pb, Cu, Zn, and Si.
Research Article
Prediction of Charpy V-notch impact energy of low carbon steel by using shallow neural network and deep learning
Si-wei Wu, Jian Yang, and Guang-ming Cao
Available online 14 August 2020, https://doi.org/10.1007/s12613-020-2168-z
[Abstract](1322) [PDF 1731KB](23)
Abstract:
In the present work, the impact energy prediction model of low carbon steel was investigated based on the industrial data. A three layer neural network, extreme learning machine and deep neural network were compared with different activation functions, structure parameters and training functions. To determine the optimal hyper-parameters of deep neural network, Bayesian optimization was applied. The model with best performance was applied to investigate importance degree of process parameter variables on impact energy of low carbon steel. The results show that deep neural network obtains better prediction results than that of shallow neural network due to the multiple hidden layers improving the learning ability of the model. Among all the models, the Bayesian optimization deep neural network achieves the highest correlation coefficient of 0.9536, lowest mean absolute relative error of 0.0843 and lowest root mean square error of 17.34 J for predicting the impact energy of low carbon steel. Among all the variables, the main factors affecting the impact energy of low carbon steel with final thickness of 7.5 mm are the thickness of the original slab, the thickness of intermediate slab and rough rolling exit temperature on the specific hot rolling production line.
Research Article
Carbothermic reduction of vanadium titanomagnetite with the assistance of sodium carbonate
Lu-ming Chen, Yu-lan Zhen, Guo-hua Zhang, De-sheng Chen, Li-na Wang, Hong-xin Zhao, Fan-cheng Meng, and Tao Qi
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2160-7
[Abstract](1301) [PDF 2054KB](21)
Abstract:
In the present study, the carbothermic reduction of vanadium titanomagnetite concentrates (VTC) with the assistance of Na2CO3 was carried out in argon atmosphere between 1073 K and 1473 K. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to investigate the phase transformations during the reaction process. By investigating the reaction between VTC and Na2CO3, it was concluded that molten Na2CO3 could break the structure of titanomagnetite by combining with the acidic oxides (Fe2O3, TiO2, Al2O3, and SiO2) to form the Na-rich melt, and release FeO and MgO. Therefore, Na2CO3 could accelerate the reduction rate. In addition, the addition of Na2CO3 was also beneficial for the agglomeration of iron particles and the slag-metal separation by decreasing the viscosity of slag. Thus, the Na2CO3 assisted carbothermic reduction will be a promising method to treat VTC at low temperatures.
Research Article
Investigation on the strain hardening behavior, strain rate sensitivity and hot deformation maps of AISI 321 austenitic stainless steel
Mehdi Shaban Ghazani and Beitallah Eghbali
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2163-4
[Abstract](1285) [PDF 1138KB](9)
Abstract:
In the present research, the hot compression tests were performed on AISI 321 austenitic stainless steel in the deformation temperature range of 800-1200˚C and constant strain rates of 0.001, 0.01, 0.1, and 1 s-1. The hot flow curves were utilized for determination of the strain hardening exponent, strain rate sensitivity exponent and construction of the processing maps. Variation of the strain hardening exponent with strain was used for prediction of the microstructural evolutions during hot deformation. Four types of variations were distinguished which reflect the occurrence of dynamic recovery, single and multiple peak dynamic recrystallization and the interaction between dynamic recrystallization and precipitation. Also, the strain rate sensitivity variations at the applied strain of 0.8 and strain rate of 0.1 s-1 was compared with microstructural evolutions and the results demonstrated the existence of reliable connection between this parameter and evolved microstructures. Furthermore, the power dissipation map at the applied strain of 0.8 was compared with the resultant microstructures at some predetermined deformation conditions. It was concluded that the microstructural evolutions is shifted from complete to partial dynamic recrystallization and dynamic recovery with increasing the power dissipation ratio.
Research Article
New insights into the flotation response of brucite and serpentine of different conditioning time: Surface dissolution behavior
Ya-feng Fu, Wan-zhong Yin, Chuan-yao Sun, Bin Yang, Jin Yao, Hong-liang Li, Chuang Li, and Hyunjung Kim
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2158-1
[Abstract](1557) [PDF 721KB](28)
Abstract:
Gangue minerals inadvertently dissolution frequently plays a detrimental role on the flotation of valuable minerals. In this paper, the effect of conditioning time on the flotation separation of brucite and serpentine was investigated. By analyzing the Mg2+ concentration, the relative content of elements, and pulp viscosity, the effect of mineral dissolution on the brucite flotation was studied. The artificial mixed mineral flotation results (with -10 μm serpentine) showed that, with the conditioning time extended from 60 s to 360 s, a large amount of Mg2+ on the mineral surface gradually dissolved into the pulp, resulting in a decrease of brucite recovery (from 83.83% to 76.79%), whereas the recovery of serpentine increased from 52.12% to 64.03%. Moreover, the SEM observation was applied to analyze the agglomeration behavior of brucite and serpentine, which clearly demonstrated the difference of adhesion behavior under various conditioning time. Finally, the total interaction energy that carried out by extended DLVO (E-DLVO) theory also supports the conclusion that the gravitational force between brucite and serpentine increases significantly with the increase of conditioning time.
Research Article
Process and kinetics of the selective extraction of cobalt from high-silicon low-grade cobalt ore by ammonia leaching
Lei Tian, Ao Gong, Xuan-gao Wu, Xiao-qiang Yu, Zhi-feng Xu, and Li-jie Chen
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2161-6
[Abstract](1323) [PDF 1527KB](5)
Abstract:
In this study, an ammonia-based system was used to selectively leach Co from an African high-silicon low-grade Co ore. In this process, other elemental impurities were prevented from leaching; hence, the subsequent process was simple and environmentally friendly. The results revealed that the leaching ratio of Co can reach 95.61% using (NH4)2SO4 as a leaching agent under experimental conditions, which involved a (NH4)2SO4 concentration, reductant dosage, leaching temperature, reaction time, and liquid–solid ratio of 300 g/L, 0.7 g, 353 K, 4 h, and 6:1, respectively. The leaching kinetics of Co showed that the apparent activation energy of Co leaching was 72.97 kJ/mol (i.e., in the range of 40–300 kJ/mol). This indicated that the leaching of Co from the Co ore was controlled using an interfacial chemical reaction. The reaction orders of the particle size and (NH4)2SO4 concentration during leaching were 0.21 and 1.5, respectively. The leaching kinetics model of the Co developed in this study can be expressed as 1-(1-α)1/3 = 28.01 × 103×r0-1 × [(NH4)2SO4]1.5 × exp(-72970/8.314T).
Research Article
Effect of ‎2-Mercaptobenzothiazole concentration on the sour corrosion behavior of API X60 pipeline steel: Electrochemical parameters and adsorption mechanism
Masoud Sabzi, Amir Hayati Jozani, Farzad Zeidvandi, Majid Sadeghi, and Saeid Mersagh Dezfuli
Available online 30 July 2020, https://doi.org/10.1007/s12613-020-2156-3
[Abstract](1342) [PDF 1304KB](11)
Abstract:
The effect of 2-Mercaptobenzothiazole concentration on the sour corrosion behavior of API X60 pipeline steel in an environment containing H2S at 25 °C and at the presence of 0, 2.5, 5, 7.5 and 10 g/L of 2-Mercaptobenzothiazole inhibitor was investigated. In order to examine the sour corrosion behavior of API X60 pipeline steel, Open Circuit Potential (OCP), potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) tests were used. The Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) were also used to analyze corrosion products. The results of OCP and potentiodynamic polarization both showed that 2-Mercaptobenzothiazole reduces the speed of both anodic and cathodic reactions. Assessment of  the Gibbs free energy of the inhibitor showed that it has a value of more than –20 kJ.mol−1and less than –40 kJ.mol−1. Therefore, the adsorption of 2-Mercaptobenzothiazole on the surface of the API X60 pipeline steel was occurred both physically and chemically. The latter was particularly intended to be adsorbed. Also, as the Gibbs free energy of the inhibitor took a negative value, it was concluded that the adsorption of 2-Mercaptobenzothiazole on the surface of the pipeline steel occurs spontaneously. The results of the EIS indicated that with increase of 2-Mercaptobenzothiazole inhibitor concentration, the corrosion resistance of API X60 steel is increased.An analysis of the corrosion products revealed that iron sulfide compounds are formed on the surface. In sum, the results showed that the increase of the inhibitor concentration results in a decrease in the corrosion rate and an increase ininhibitory efficiency (%IE). Additionally, it was found that 2-Mercaptobenzothiazole adsorption process on the API X 60 steel surfaces in a H2S-containing environment follows the Langmuir adsorption isotherm.And the adsorption process is carried out spontaneously. 
Research Article
Insights into U(VI) adsorption behavior onto polypyrrole coated 3R-MoS2 nanosheets prepared with the molten salt electrolysis method
Yu-hui Liu, Meng Tang, Shuang Zhang, Yu-ling Lin, Ying-cai Wang, You-qun Wang, Ying Dai, Xiao-hong Cao, Zhi-bin Zhang, and Yun-hai Liu
Available online 30 July 2020, https://doi.org/10.1007/s12613-020-2154-5
[Abstract](1568) [PDF 1326KB](43)
Abstract:
To improve the separation capacity of uranium in aqueous solutions, 3R-MoS2 nanosheets were prepared with molten salt electrolysis and further modified with polypyrrole (PPy) to synthesize a hybrid nanoadsorbent (PPy/3R-MoS2). The preparation conditions of PPy/3R-MoS2 were investigated and the obtained nanosheets were characterized with SEM, HRTEM, XRD, FTIR, and XPS. The results show that PPy/3R-MoS2 exhibited enhanced adsorption capacity towards U(VI) compared to pure 3R-MoS2 and PPy; the maximum adsorption was 200.4 mg/g. The adsorption mechanism was elucidated with XPS and FTIR: 1) negatively charged PPy/3R-MoS2 nanosheets attracted UO22+ by electrostatic attraction; 2) exposed C, N, Mo, and S atoms complexed with U(VI) through coordination; 3) Mo in the complex partly reduced the adsorbed U(VI) to U(IV), which further regenerated the adsorption point and continuously adsorbed U(VI). The design of the PPy/3R-MoS2 composite with high adsorption capacity and chemical stability provides a new direction for the removal of radionuclide.
Research Article
Effect of calcination temperature on the pozzolanic activity of maize straw stem ash treated with portlandite solution
Ting-ye Qi, Hao-chen Wang, Guo-rui Feng, Yu-jiang Zhang, Jin-wen Bai, and Yan-na Han
Available online 24 July 2020, https://doi.org/10.1007/s12613-020-2148-3
[Abstract](1371) [PDF 1117KB](8)
Abstract:
The effect of calcination temperature on the pozzolanic activity of maize straw stem ash (MSSA) was evaluated. The MSSA samples calcined at temperature values of 500, 700, and 850 °C were dissolved in portlandite solution for 6 h, and the residual samples were obtained. The MSSA and MSSA residual samples were analyzed using FT-IR, XRD, SEM, and XPS to determine the vibration bonds, minerals, microstructure, and Si 2p transformation behavior. The conductivity, pH value, loss of conductivity with dissolving time of the MSSA-portlandite mixed solution were determined. The main oxide composition of MSSA were silica and potassium oxide. The dissolution of Si4+ content of MSSA at 500 °C were high compared to those of the other calcination temperatures. The conductivity and loss of conductivity of MSSA at 700 °C were high compared to those of the other calcination temperatures at a particular dissolving time due to the higher KCl content in MSSA at 700 °C. C-S-H was easily identified in MSSA samples using XRD, and small cubic and nearly spherical particles of C-S-H were found in the MSSA residual samples. In conclusion, the optimum calcination temperature of MSSA having the best pozzolanic activity is 500 °C but avoid excessive agglomeration.
Research Article
The influence of gamma irradiation on the electrical, thermal, and electrochemical properties of reduced graphene oxide
M.M. Atta, H.A. Ashry, G.M. Nasr, and H.A.Abd EI-Rehim
Available online 17 July 2020, https://doi.org/10.1007/s12613-020-2146-5
[Abstract](1440) [PDF 1014KB](15)
Abstract:
In this paper, the properties of γ-ray reduced graphene oxide (GRGOs) samples are compared to hydrazine reduced graphene oxide (HRGO) sample. Characterization techniques FTIR, XRD, Raman spectra, Brunauer-Emmett-Teller (BET) surface area analysis, TGA, electrometer, and cyclicvoltemety were used for the verification of the reduction process, structural changes & defects, and measure the thermal, electrical, and electrochemical properties of samples. It was concluded that γ- Irradiation distorts the structure of GRGOs with massive defects owing to the greater formation of new smaller sp2 - hybridized domains compared to HRGO. The thermal stability of GRGOs was higher than HRGO indicating the more efficient removal of thermally-labile oxygen species by γ-ray. Furthermore, RRGOs showed a pseudocapacitive behavior compared to the electrical double layer behavior of HRGO. The most interesting obtained results are the enhanced specific capacitance of GRGOs to nearly three times in comparison to HRGO which indicates the preference for radiation reduction method in energy storage applications.
Research Article
A new electrochemical process on the recovery metallic Mn from waste LiMn2O4 based Li-ion batteries in NaCl-CaCl2 melts
Jing-long Liang, Dong-bin Wang, Le Wang, Hui Li, Wei-gang Cao, and Hong-yan Yan
Available online 16 July 2020, https://doi.org/10.1007/s12613-020-2144-7
[Abstract](1447) [PDF 798KB](20)
Abstract:
A new method for the recovery of Mn is proposed via direct electrochemical reduction of LiMn2O4 from the waste lithium-ion batteries in NaCl-CaCl2 melts at 750℃. The results show the reduction process of LiMn2O4 by electrochemical methods on the coated electrode surface are in three steps, Mn(IV) → Mn(III) → Mn(II) → Mn. The products of electro-deoxidation are CaMn2O4, MnO, (MnO)x(CaO)1-x and Mn. Metal Mn appears when the electrolytic voltage increased to 2.6 V. Increasing the voltage could promote the deoxidation reaction process. With the advancement of the three-phase interline(3PI), the electric deoxygenation gradually proceeds from the outward to core. With the high voltage, the kinetic process of the reduction reaction is accelerated, and double 3PI in different stages are generated.
Research Article
Microstructure and phase elemental distribution in high-boron multi-component cast irons
Yuliia G. Chabak, K. Shimizu, Vasily G. Efremenko, Michail A. Golinskyi, Kenta Kusumoto, Vadim I. Zurnadzhy, and Alexey V. Efremenko
Available online 9 July 2020, https://doi.org/10.1007/s12613-020-2135-8
[Abstract](1904) [PDF 3538KB](8)
Abstract:
The novel cast irons of nominal chemical composition (wt.%) 0.7C-5W-5Mo-5V-10Cr-2.5Ti were fabricated with the additions of 1.6 wt.% B and 2.7 wt.% B. The aim of this work was a study of the boron’s effect on the alloys’ structural state and phase elemental distribution with respect to the formation of wear-resistant structure constituents. It was found that the alloy containing 1.6 % B was composed of three different eutectics: (a) “M2(C,B)5+ferrite” having a “Chinese Script” morphology (89.8 vol. %), (b) “M7(C,B)3+Austenite” having a “Rosette” morphology, and (c) “M3C+Austenite” having a “Ledeburite”-shaped morphology (2.7 vol. %). With a boron content of 2.7 wt.%, the bulk hardness increased from 31 HRC to 38.5 HRC. The primary carboborides M2(C,B)5 with average microhardness of 2797 HV appeared in the structure with a volume fraction of 17.6 vol.%. The volume fraction of eutectics (a) and (b, c) decreased to 71.2 vol.% and 3.9 vol. %, respectively. The matrix was “ferrite/austenite” for 1.6 wt.% B and “ferrite/pearlite” for 2.7 wt.% B. Both cast irons contained compact precipitates of carbide (Ti,M)C and carboboride (Ti,M)(C,В) with a volume fraction of 7.3-7.5 vol. %. The elemental phase distributions, discussed based on EDX-analysis and the appropriate phase formulae, are presented.
Research Article
Solid state reaction of CaO-V2O5 mixture: A fundamental study for the vanadium extraction process
Jun-yi Xiang, Xin Wang, Gui-shang Pei, Qing-yun Huang, and Xue-wei Lv
Available online 9 July 2020, https://doi.org/10.1007/s12613-020-2136-7
[Abstract](1529) [PDF 745KB](16)
Abstract:
The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO-V2O5, which is the predominant binary mixture involved in the vanadium recovery process. Thermal analysis, X-ray diffraction, scanning electron microscope and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples. The extent of the solid reaction was derived using the preliminary quantitative phase analysis of the X-ray diffractograms. The results indicate that the solid reaction of CaO-V2O5 mixture is significantly influenced by the reaction temperature and CaO/V2O5 mole ratio. The transformation of calcium vanadates goes through a step-by-step reaction of CaO-V2O5, CaO-CaV2O6, and CaO-Ca2V2O7 depending on the CaO/V2O5 mole ratio. The kinetic data of the solid reaction of CaO-V2O5 (1:1) mixture was found to follow second order reaction model. The activation energy (Eα) and the pre-exponential factor (A) were determined to be 145.38 kJ/mol, and 3.67×108 min-1, respectively.
Research Article
Recovery and regeneration of LiFePO4 from spent lithium ion batteries via a novel pretreating process
Cheng Yang, Jia-liang Zhang, Qian-kun Jing, Yu-bo Liu, Yong-qiang Chen, and Cheng-yan Wang
Available online 9 July 2020, https://doi.org/10.1007/s12613-020-2137-6
[Abstract](1584) [PDF 1311KB](34)
Abstract:
Recently, the recycling of spent LiFePO4 batteries has received extensive attention due to their environmental impact and economic benefit. In the pretreating process of spent LiFePO4 batteries, the separation of the active materials and the current collectors determines the difficulty of recovery process and the quality of product. In this work, a facile and efficient pretreating process is first proposed. After only freezing the electrode pieces and immersing it in boiling water, LiFePO4 materials have been basically peeled from Al foil. Then, after roasting in an inert atmosphere and sieving, all of the cathode and anode active materials were separated from Al and Cu foils easily and efficiently. The active materials were subjected to acid leaching and the leaching solution further prepared FePO4 and Li2CO3. Finally, the battery-grade FePO4·and Li2CO3 were used to re-synthesize LiFePO4/C via the carbon thermal reduction method. Re-synthesized LiFePO4/C cathode exhibits good electrochemical performance, which satisfies the requirement for middle-end LiFePO4 batteries. The whole process is found to be environmental and have great potential for industrial-scale recycling of spent lithium-ion batteries.
Research Article
Extraction of copper from copper bearing biotite by ultrasonic-assisted leaching
Bao-qiang Yu, Jue Kou, Chun-bao Sun, and Yi Xing
Available online 5 July 2020, https://doi.org/10.1007/s12613-020-2132-y
[Abstract](1420) [PDF 467KB](14)
Abstract:
Copper bearing biotite is a typical refractory copper mineral on the surface of Zambian copper belt. Aiming to treat this kind of copper oxide ore with a more effective method, ultrasonic-assisted acid leaching was conducted in this paper. Compared with regular acid leaching, ultrasound could reduce leaching time from 120 min to 40 min, and sulfuric acid concentration could be reduced from 0.5 mol•L-1 to 0.3 mol•L-1. Besides, leaching temperature could be reduced from 75℃ to 45℃ at same copper leaching rate of 78%. Mechanism analysis indicates that ultrasonic wave can cause delamination of copper bearing biotite and increase the specific surface area from 0.55 m2•g-1 to 1.67 m2•g-1. The results indicate that copper extraction from copper bearing biotite by ultrasonic-assisted acid leaching is more effective than regular acid leaching. This study proposes a promising method for recycling valuable metals from phyllosilicate minerals.
Research Article
Fine Structure Characterization of Explosively Welded GH3535/316H Bimetallic Plate Interface
Jia Xiao, Ming Li, Li Jiang, De-jun Wang, Xiang-Xi Ye, Jian-ping Liang, Ze-zhong Chen, Na-xiu Wang, and Zhi-jun Li
Available online 26 June 2020, https://doi.org/10.1007/s12613-020-2128-7
[Abstract](1152) [PDF 2033KB](17)
Abstract:
To provide one more cost-effective structural materials for the ultra-high temperature molten salt thermal storage systems, the explosion-welded technology was induced to manufacture the GH3535/316H bimetallic plates in the present work. The microstructures of the bonding interfaces have been extensively investigated by scanning electron microscope, energy dispersive spectrometer, and electron probe micro-analyzer. It was discovered that the bonding interfaces possess the periodic wavy morphology and are adorned by peninsula- or island-like transition zones. At higher magnification, matrix recrystallization region, fine grain region, columnar grain region, equiaxed grain region, and shrinkage porosity can be observed in the transition zones and the surrounding area. The analysis of electron backscattered diffraction demonstrated that the strain in the recrystallization region of the GH3535 matrix and transition zone is lower than the substrate. Strain concentration occurred at the interface and the solidification defects in the transition zone. The dislocation substructure in 316H near the interface was characterized by the electron channeling contrast imaging. The results showed that a lot of dislocations network was formed in the grains of 316H. Microhardness tests showed that the micro-hardness decreased as the distance from the welding interface increased, and the lowest hardness value was inside the transition zone.
Research Article
Synthesis and characterization of ceria nanoparticles by complex-precipitation route
Yan-ping Li, Xue Bian, Yang Liu, Wen-yuan Wu, and Gao-feng Fu
Available online 24 June 2020, https://doi.org/10.1007/s12613-020-2126-9
[Abstract](1467) [PDF 1331KB](5)
Abstract:
Ceria (CeO2) nanoparticles have been successfully synthesized via a simple complex-precipitation route, which employs cerium chloride as cerium source and citric acid as precipitant. The elemental analysis results of carbon, hydrogen, oxygen and cerium in the precursors were calculated, and the results revealed that the precursors were composed of Ce (OH)3, [Ce(H2Cit)3] or [CeCit]. X-ray diffraction (XRD) analysis showed all ceria nanoparticles prepared to be face centered cubic structure. As n value was 0.25 and pH value was 5.5, the specific surface area of the sample reached the maximum value of 83.17 m2/g. Ceria nanoparticles were observed by scanning electron microscope (SEM). Selected electron diffraction patterns of some samples were obtained by transmission electron microscope (TEM), and the crystal plane spacing of each low-exponential crystal plane was calculated. The UV-vis transmittance curve shows that it has the ability to absorb ultraviolet light and pass through visible light. Among all samples, the minimum of the average transmittance of UVA (TUVA) is 4.42%, and the minimum of the average transmittance of UVB (TUVB) is 1.56%.
Research Article
Electrochemically functionalized graphene as an anti-corrosion reinforcement in Cu matrix composite thin films
Akhya kumar Behera, Amlan Das, Sanjeev Das, and Archana Mallik
Available online 24 June 2020, https://doi.org/10.1007/s12613-020-2124-y
[Abstract](1598) [PDF 1414KB](20)
Abstract:
In this article, Cu-Gr composite thin films are prepared by electrodeposition route using in-house synthesized graphene sheets. Graphene sheets are synthesized by the electrochemical exfoliation route using 1M HClO4 acid as electrolyte. Graphene sheets have been confirmed by XRD, FTIR, FESEM and TEM microscopy. The (002) plane of graphene sheets are observed at 2θ of 25.66⁰. The (002) plane confirms the crystal structure of carbon peaks. The stretching vibration of C=C bond at a wavelength of 1577 cm-1 and other functional groups of carboxyl and epoxide groups have been observed from FTIR. TEM microscopy confirms the transparent structure of graphene sheets. The prepared graphene sheets were used as reinforcement in concentration of 0.1 g/L and 0.3 g/L with a copper matrix to synthesize Cu-Gr composite. The prepared composite thin films have been characterized by XRD, SEM and EDS for morphological and analytical study. The presence of graphene sheets in Cu-Gr composite was confirmed by EDS analysis. The prepared Cu-Gr nanocomposite thin film shows higher corrosion resistance as compared to pure copper thin films in 3.5% NaCl as confirmed by Tafel plots. EIS also compliments the above results, which shows that 0.3 g/L composite film has highest film resistance.
Research Article
Effects of forced aeration on community dynamics of free and attached bacteria in copper sulphide ore bioleaching
Sheng-hua Yin, Wei Chen, and I.M.S.K. Ilankoon
Available online 24 June 2020, https://doi.org/10.1007/s12613-020-2125-x
[Abstract](1432) [PDF 1535KB](17)
Abstract:
In order to obtain better bioleaching efficiency, bacterial community dynamics and copper leaching with applying forced aeration were investigated during low-grade copper sulphide bioleaching. Results illustrated appropriate aeration yielded improved bacteria concentrations and enhanced leaching efficiencies. The highest bacteria concentration and Cu2+ concentration after 14-day leaching were 7.61×107 cells•mL-1 and 704.9 mg•L-1, respectively, when aeration duration was 4 h•d-1. The attached bacteria played a significant role during bioleaching from day 1 to day 7. However, free bacteria dominated the bioleaching processes from day 8 to day 14. This is mainly caused by the formation of passivation layer through Fe3+ hydrolysis along with bioleaching, which inhibited the contact between attached bacteria and ore. Meanwhile, 16S rDNA analysis verified the effect of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidanson on bioleaching process. The results demonstrate the importance of free and attached bacteria in bioleaching.
Research Article
Microstructure evolution and mechanical properties of Mg-9Al-1Si-1SiC composites processed by multi-pass equal-channel angular pressing at various temperatures
Xiang-peng Zhang, Hong-xia Wang, Li-ping Bian, Shao-xiong Zhang, Yong-peng Zhuang, Wei-li Cheng, and Wei Liang
Available online 21 June 2020, https://doi.org/10.1007/s12613-020-2123-z
[Abstract](1476) [PDF 1275KB](18)
Abstract:
In this study, Mg-9Al-1Si-1SiC (wt%) composites were processed by multi-pass equal-channel angular pressing (ECAP) at various temperatures, and the microstructure evolution and strengthening mechanism were explored. The results indicate that the as-cast microstructure was composed of an α-Mg matrix, discontinuous Mg17Al12 phase, and Chinese script-shaped Mg2Si phase. After solution treatment, almost all of the Mg17Al12 phases are dissolved into the matrix, while the Mg2Si phases are not. The subsequent multi-pass ECAP at different temperatures results in more complete dynamic recrystallization and uniform distribution of Mg17Al12 precipitates when compared with the multi-pass ECAP at a constant temperature. A large number of precipitates can effectively improve the nucleation ratio of recrystallization through a particle-stimulated nucleation mechanism. In addition, the nano-scale SiC particles are mainly distributed at grain boundaries, which can effectively prevent dislocation movement. The excellent comprehensive mechanical properties are mainly attributed to grain boundary strengthening and Orowan strengthening.
Research Article
Hydrothermal synthesis of Zn-Mg based layered double hydroxide coating over copper for its corrosion prevention in both chloride and hydroxide media
Nikhil, Gopal Ji, and Rajiv Prakash
Available online 21 June 2020, https://doi.org/10.1007/s12613-020-2122-0
[Abstract](1563) [PDF 1066KB](13)
Abstract:
Layered double hydroxides (LDHs) can be very interesting materials in corrosion inhibition applications as LDHs stops the corrosive elements by its ability of double layer formation and locking them between its layers. In this work, Zn-Mg based LDHs are grown over copper substrate by hydrothermal method. Two types of Zn-Mg based LDHs have been prepared based on hydrothermal reaction time. Both LDHs have been characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, high resolution scanning electron microscopy, energy dispersive X-ray analysis, atomic force microscopy and X-ray diffraction patterns. The results show that LDHs are successfully grown on copper; however, they are found different in terms of thickness and structural configuration. Corrosion testing of LDHs has been executed both in 0.1 M NaCl and 0.1 M NaOH by ac impedance measurements and Tafel polarization curves. The results show that L48 gives more than 90% protection to copper, which is higher than protection provided by L24. However, it is evident that both LDH (L24 and L48) is more effective in NaCl, in terms of reduction of corrosion. This information indicates that LDH is more efficient to exchange Cl- ions than OH- ions.
Research Article
Rapid Removal of the Copper Impurity from Bismuth-Copper Alloy Melts via Super-Gravity Separation
Xiao-chun Wen, Lei Guo, Qi-peng Bao, and Zhan-cheng Guo
Available online 17 June 2020, https://doi.org/10.1007/s12613-020-2118-9
[Abstract](1572) [PDF 1673KB](19)
Abstract:
To rapidly remove the copper impurity from bismuth-copper alloy melts, a green method of super-gravity separation was investigated, which has the characteristics of enhancing the filtration process of bismuth and copper phases. In this study, the influence of super-gravity on the removal of copper impurity from bismuth-copper alloy melts was discussed. After super-gravity separation, the liquid bismuth-rich phases were mainly filtered into the lower crucible, while most of the fine copper phases were remained in the opposite direction. With optimized conditions of T = 280℃, G = 450, and t = 200 s, the purity of the filtered bismuth phase exceeded 99.7wt%, and the mass proportion of the separated bismuth of Bi-2wt%Cu and Bi-10wt%Cu alloys reached 96.27wt% and 85.71wt% respectively, which indicated the little loss of bismuth in the residual. Simultaneously, the removal rate of copper impurity went to 88.0% and 97.8%, respectively. Furthermore, the separation process could be completed rapidly, environmentally friendly and efficiently.
Research Article
Hydrometallurgical recycling of valuable metals from spent lithium-ion batteries by reductive leaching with stannous chloride
Liu-ye Sun, Bo-rui Liu, Tong Wu, Guan-ge Wang, Qing Huang, Yue-feng Su, and Wu Feng
Available online 10 June 2020, https://doi.org/10.1007/s12613-020-2115-z
[Abstract](1527) [PDF 713KB](13)
Abstract:
A reductant counts for much in the hydrometallurgical recycling of valuable metals from spent lithium-ion batteries (LIBs). There is limited information about SnCl2 as a reductant with organic acid (maleic acid) to recover value metals from spent LiCoO2 material. The leaching efficiencies were 98.67% and 97.59% for Li and Co with 1 mol L-1 of maleic acid and 0.3 mol L-1 of SnCl2 at 60°C and 40 min. And the kinetics and thermodynamics of the leaching process were inquired in the article to study the mechanism of leaching process clearly. According to the comparison of H2O2 on the leaching efficiency, optimal leaching parameters and the activation energy, it is feasible to replace H2O2 with SnCl2 as a leaching reducer in the leaching process. In addition, when SnCl2 is used in the acid-leaching process, Sn residue in leachate may has a positive effect on the re-synthesis of nickel-rich cathode materials. Therefore, the present study can provide a new direction for reductants selection for the hydrometallurgical recovery of valuable metals from spent LIBs
Research Article
Microstructure evolution and thermal conductivity of the diamond/Al composite during thermal cycling
Ping-ping Wang, Guo-qin Chen, Wen-jun Li, Hui Li, Bo-yu Ju, Murid Hussain, Wen-shu Yang, and Gao-hui Wu
Available online 10 June 2020, https://doi.org/10.1007/s12613-020-2114-0
[Abstract](1776) [PDF 864KB](25)
Abstract:
The microstructure evolution and performance of Diamond/Al composites during thermal cycling, which is important for their wide application, has been rarely investigated. In the present work, the thermal stability of Diamond/Al composite during thermal cycling up to 200 cycles has been explored: thermal conductivity of the composites was measured, and SEM observation of the marked-out area of the same sample was carried out to achieve quasi-in-situ observation. The interface between (100) plane of diamond and Al matrix was well bonded with zigzag morphology and extensive needle-like Al4C3 phases. However, the interfacial bonding between (111) plane of diamond and Al matrix was rather weak, which was debonded during thermal cycling. The debonding length was initially increased rapidly within the initial 100 cycles, which was then increased slowly in the following 100 cycles. The thermal conductivity of the Diamond/Al composite was primarily decreased very abruptly within initial 20 cycles, increased afterward, and then further decreased monotonously with the increase of thermal cycles. The decreased thermal conductivity of the Al matrix and corresponding thermal stress concentration at the interface caused by the thermal mismatch stress is suggested as the main factor especially in the initial period rather than the interfacial debonding.
Research Article
Characterization of MCrAlY/nano-Al2O3 nanocomposite powder produced by high-energy mechanical-milling as feedstock for HVOF spraying deposition
Farzin Ghadami, A. Sabour Rouh Aghdam, and Soheil Ghadami
Available online 3 June 2020, https://doi.org/10.1007/s12613-020-2113-1
[Abstract](1599) [PDF 2466KB](30)
Abstract:
In this study, Al2O3 nanoparticles, as well as MCrAlY/nano-Al2O3 nanocomposite powder were produced using a high-energy ball-milling process. In addition, the MCrAlY/nano-Al2O3 coating was deposited by selecting an optimum nanocomposite powder as feedstock using high-velocity oxy-fuel (HVOF) thermal spraying technique. The morphological and microstructural examinations of Al2O3 nanoparticles, as well as the commercial MCrAlY and MCrAlY/nano-Al2O3 nanocomposite powders, were investigated using X-ray diffraction (XRD) analysis, field emission scanning electron microscope (FESEM) equipped with electron dispersed spectroscopy (EDS) analysis and transmission electron microscope (TEM). The structural investigations and Williamson-Hall results demonstrated that the ball-milled Al2O3 powder after 48 h has the smallest crystallite size and the highest amount of lattice strain compared to all other as-received and ball-milled Al2O3 owing to its optimal nanocrystalline structure. Besides, in the case of developing MCrAlY/nano-Al2O3 nanocomposite powder, with increasing mechanical-milling duration, the particle size of the nanocomposite powders was decreased.
Research Article
Effect of Co substitution on the structural, dielectric and optical properties of KBiFe2O5
K. Chandrakanta, Rasmita Jena, Pikesh Pal, Md. Faruck Abdullah, Somdatta D. Kaushik, and Anil K. Singh
Available online 31 May 2020, https://doi.org/10.1007/s12613-020-2110-4
[Abstract](1475) [PDF 1117KB](17)
Abstract:
Cobalt modified brownmillerite KBiFe2O5 [KBiFe2(1-x)Co2xO5 (x= 0, 0.05)] polycrystalline is synthesized following solid-state reaction route. Rietveld refinement of X-ray diffraction (XRD) data reveals the phase purity of KBiFe2O5 (KBFO) and KBiFe1.9Co0.1O5 (KBFCO). The optical band gap energy (Eg) of KBFO is observed to be decrease from 1.59 eV to 1.51 eV by Co substitution. The decrease in band gap attributes to the tilting in the Fe-O tetrahedral structure of KBFCO. The observed room temperature Raman peaks of KBFCO are shifted by 3 cm-1 towards lower wavenumber in comparison with KBFO Raman peaks. The shifting of Raman active modes can be attributed to the change in the bond angles and bond lengths of Fe-O tetrahedral and modification in oxygen deficiency in KBFO due to Co doping. The frequency-dependent dielectric constant and loss of KBFCO also decrease with respect to KBFO at room temperature, which is a consequence of the reduction in oxygen migration and modification in vibrational modes present in the sample.
Research Article
Kinetics and mechanism of oxidation for nickel-containing pyrrhotite tailings
Alexander M. Klyushnikov, Rosa I. Gulyaeva, Evgeniy N. Selivanov, and Sergey M. Pikalov
Available online 27 May 2020, https://doi.org/10.1007/s12613-020-2109-x
[Abstract](1825) [PDF 796KB](17)
Abstract:
Abstract: X-ray powder diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry, differential scanning calorimetry and mass spectrometry have been used to study the products of nickel-containing pyrrhotite tailings oxidation by the oxygen in the air. The kinetic triplets of oxidation, such as activation energy (Ea), pre-exponential factor (A) and reaction model (f(α)) being a function of the conversion degree (α), were adjusted by the regression analysis. In case of a two-stage process representation, the first step proceeds under autocatalysis control and ends at α = 0.42. The kinetic triplet of the first step can be presented as Ea = 262.2 kJ/mol, lgA = 14.53 s-1, f(α) = (1 – α)4.11(1 + 1.51·10–4α). For the second step, the process is controlled by the two-dimensional diffusion of the reactants in the layer of oxidation products. The kinetic triplet of the second step: Еa = 215.0 kJ/mol, lgA = 10.28 s-1, f(α) = (–ln(1 – α))–1. The obtained empirical formulae for the rate of pyrrhotite tailings oxidation reliably describe the macro-mechanism of the process and can be used to design automatization systems for roasting these materials.
Research Article
Effect of microwave pretreatment on grinding and flotation kinetics of copper complex ore
Hamed Gholami, Bahram Rezai, Ahmad Hassanzadeh, Akbar Mehdilo, and Mohammadreza Yarahmadi
Available online 24 May 2020, https://doi.org/10.1007/s12613-020-2106-0
[Abstract](1882) [PDF 692KB](41)
Abstract:
The present work initially studies the kinetics of microwave-assisted grinding and flotation in a porphyry copper deposit. The kinetics tests were carried out on the untreated and microwave irradiated samples by varying the exposure time from 15-150 sec. Optical microscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy were used for determining the mineral liberation, particle surface properties and mineralogical analyses. Results disclosed that the ore’s breakage rate constant monotonically increased by increasing the exposure time particularly for the coarsest fraction size (400 µm) owing to the creation of thermal stress fractures alongside grain boundaries. Exceeded irradiation time (>60 sec) led to the creation of oxidized and porous surfaces along with a dramatic change of particle morphologies resulting in a substantial reduction of both chalcopyrite and pyrite’s flotation rate constants and ultimate recoveries. We concluded that MW-pretreated copper ore was ground faster than untreated one but their floatabilities were somewhat similar.
Research Article
Microemulsion leaching of vanadium from sodium roasted vanadium slag by fusion of leaching and extraction processes
Yun Guo, Hong-yi Li, Yi-heng Yuan, Jie Huang, Jiang Diao, Gang Li, and Bing Xie
Available online 24 May 2020, https://doi.org/10.1007/s12613-020-2105-1
[Abstract](1568) [PDF 669KB](21)
Abstract:
In this work, the fusion of leaching and purification steps is realized by directly using microemulsion as the leaching agent. The DEHPA/n-heptane/NaOH microemulsion system has been established to directly leach vanadates from sodium roasted vanadium slag. The effect of leaching arguments on the leaching efficiency is investigated, including the molar ratio of H2O/NaDEHP (W), the DEHPA concentration of, solid/liquid ratio, stirring time, and leaching temperature. In optimal situations, the vanadium leaching efficiency could attain 79.57%. Both the XRD characterization of the leaching residue and the Raman spectrum of the microemulsion before and after leaching demonstrate the successful entrance of vanadates from sodium roasted vanadium slag into the microemulsion. The proposed method has realized the leaching and purification of vanadates in one step, which significantly reduces the production cost and environmental pollution. It affords new ways of thinking about the greener recovery of valuable metals from solid resources.
Research Article
Reduction of NOx emission based on optimizing the proportions of mill scale and coke breeze during sintering process
Zhi-gang Que, Xian-bin Ai, and Sheng-li Wu
Available online 21 May 2020, https://doi.org/10.1007/s12613-020-2103-3
[Abstract](1541) [PDF 551KB](17)
Abstract:
How to cost-effectively reduce NOx emission of iron ore sintering process is a new challenge for iron and steel industry at present. The effects of proportion of mill scale and coke breeze on the NOx emission, strength of sinter and sinter indexes were studied by combustion tests and sinter pot tests. Results showed that the fuel-N’s conversion rate decreased with increasing of the proportions of mill scale. Because NO was reduced to N2 by Fe3O4, FeO and Fe in mill scale. The strength of sinter reached a highest value at 8.0 wt% mill scale due to the formation of low melting point minerals. Meanwhile, the fuel-N’s conversion rate slightly increased and total NOx emission significantly decreased with the proportions of coke breeze increased. Because CO formation and contents of N element in sintered mixture decreased. However, the strength of sinter was also decreased since the decreasing of the melting minerals. In addition, results of sinter pot tests indicated that NOx emission obviousely decreased and sinter indexes have good performances when the proportions of mill scale and coke breeze were 8.0 wt% and 3.70 wt% in sintered mixture.
Research Article
Adsorption properties of V(IV) on the resin-activated carbon composite electrodes in capacitive deionization
Xiao-man Tian, Shen-xu Bao, and Yi-min Zhang
Available online 17 May 2020, https://doi.org/10.1007/s12613-020-2100-6
[Abstract](1559) [PDF 928KB](18)
Abstract:
The composite electrodes prepared by cation exchange resins and activated carbon (AC) were used to adsorb V(IV) in capacitive deionization (CDI). The electrode made of middle resin size (D860/AC M) has the largest specific surface area and mesoporous content than other two composite electrodes. Electrochemical analysis showed that D860/AC M presents higher specific capacitance and electrical double layer capacitor, and significantly lower internal diffusion impedance, thus it exhibits the highest adsorption capacity and rate for V(IV) among three electrodes. The intra-particle diffusion model fits well the initial adsorption stage, while the liquid film diffusion model is more suitable for the fitting at the later stage. The pseudo-second-order kinetic model is fit for the entire adsorption process. The adsorption of V(IV) on the composite electrode follows the Freundlich isotherm, and thermodynamic analysis indicates that this is an exothermic process with entropy reduction and the electric field force plays a dominant role in the CDI process. This work is conducive to peep at the ions adsorption behaviors and mechanisms on the composite electrodes in CDI.
Research Article
Fabrication and characterization of GNPs and CNTs reinforced Al7075 matrix composites through stir casting process
Siavash Imanian Ghazanlou and Beitallah Eghbali
Available online 17 May 2020, https://doi.org/10.1007/s12613-020-2101-5
[Abstract](1637) [PDF 3216KB](19)
Abstract:
In the present research, effect of graphene nanoplates (GNPs) and carbon nanotubes (CNTs) addition into the Al7075 matrix through the stir casting method on the microstructure and mechanical properties of fabricated composites was investigated. XRD results represented that by addition of reinforcements into Al7075, the dominant crystal orientation changed from a weak (002) to a strong (111). By increasing of reinforcements, the fraction of porosity increased and among the two mentioned reinforcements, addition of GNPs in to the Al7075 matrix led to create a higher fraction of porosity. Addition of reinforcements into Al7075 matrix owing to agglomeration of reinforcements and formation of porosities did not change the experimental Yield strength (YS) considerably. Theoretical calculations to determine the contributions of strengthening mechanisms in the enhancement of YS revealed that by addition of reinforcements, the grain size of matrix did not decrease, so Hall-Petch was not activated. By addition of self-lubricant GNPs and CNTs into the matrix, the wear rate values decreased and the lowest friction coefficient and the highest wear resistance belonged to Al7075/0.53 wt. % CNTs. In Al7075/GNPs, the dominant mechanisms were adhesion and delamination and a little abrasive occurred.
Research Article
Solid particle erosion studies on thermally deposited alumina–titania coatings over aluminium alloy
Chellaganesh Durai, M. Adam Khan, J. T. Winowlin Jappes, Nouby M. Ghazaly, and P. Madindwa Mashinini
Available online 17 May 2020, https://doi.org/10.1007/s12613-020-2099-8
[Abstract](1621) [PDF 1175KB](15)
Abstract:
Thermal barrier coatings are widely used for surface modifications. Surface modifications are performed to enhance the surface properties of the material and protect the same from surface degradation such as erosion and corrosion. To increase the wear resistance, the ceramic based coatings are highly recommended in the industrial sector. In this paper, alumina-titania ceramic powder is deposited on the aluminium alloy using atmospheric plasma spray (APS) technique. Experimental investigations are performed to study the material behavior and its erosion rate. Solid particle erosion studies are performed by varying particle velocity and particle flow rate. The angle impingement and stand-of-distance are maintained constant for comparison. The behavior of base metal has clinging effect and the mass change found negative at a maximum particle flow rate of 4g/min. At the same process condition coated sample has lost his life and reached a maximum erosion rate of 0.052 (Δg/g). From the solid particle erosion studies, it has been confirmed that the behavior of as cast aluminium alloy has severe surface damage with erodent reinforcement when compared to coated samples. The influence of particle velocity and the particle flow rate were analyzed. The influence of input process parameter was also identified.
Research Article
Insights into mineralogical characteristics of typical copper sulfide tailings using automated mineral liberation analysis: A case study from the Chambishi copper mine
Xiao-liang Zhang, Jue Kou, Chun-bao Sun, Rui-yang Zhang, Min Su, and Shuo-fu Li
Available online 13 May 2020, https://doi.org/10.1007/s12613-020-2093-1
[Abstract](1579) [PDF 1114KB](13)
Abstract:
As ore grades constantly decline, more copper tailings that still contain a considerable amount of unrecovered copper are expected to be produced as a byproduct of froth flotation. This research reveals the occurrence mechanism of copper minerals in a typical copper sulfide tailing using quantitative mineral liberation analysis (MLA) integrated with scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). The results show that copper minerals are highly disseminated within coarse gangue particles, and more than 90% of them are accumulated in the size fractions less than 106 μm. The predominant copper-bearing mineral is chalcopyrite, which is closely intergrown with orthoclase and muscovite rather than quartz. The flotation tailing sample still contains 3.28wt% liberated chalcopyrite and 3.13wt% liberated bornite because of their extremely fine granularity. The SEM-EDS analysis further demonstrate that copper minerals mainly occurred as fine dispersed and fully enclosed structures in gangue minerals. The information obtained from this research could offer useful references for recovering residual copper from flotation tailings.
Research Article
Preparation and photocatalytic property of Fe2O3/ZnO composite with superhydrophobicity
Muntadher I. Rahmah, Raad S. Sabry, and Wisam J. Aziz
Available online 13 May 2020, https://doi.org/10.1007/s12613-020-2096-y
[Abstract](1775) [PDF 1414KB](20)
Abstract:
A facile approach was developed to construct Fe2O3-modified ZnO micro/nanostructures with excellent superhydrophobicity and photocatalytic activity. The impacts of stearic acid (SA) and Fe2O3-modified on the morphology, water contact angle (WCA) and photocatalytic degradation were investigated. The superhydrophobic results showed increased of WCA from 144 ± 2° to 154 ± 2° when SA weight increase from 5 mg to 20 mg due to formation of hierarchical or rough structure. Furthermore, Fe2O3-modified ZnO micro/nanostructures surface before and after treatment with SA (20 mg) chosen to evaluate the photocatalytic of Methylene blue (MB) dye by supporting visible-light. The results showed degradation of MB after 80 min of irradiation with photodegradation efficiency 91.5% for superhydrophobic state and 92% for the hydrophilic state. This improvement in photocatalytic activity at both states may be attributable to an increase of surface area and improve charge carriers separation.
Research Article
Effect of chromium on microstructure and the hot ductility of Nb microalloyed steel
Yang Liu, Yan-hui Sun, and Hao-tian Wu
Available online 13 May 2020, https://doi.org/10.1007/s12613-020-2092-2
[Abstract](1566) [PDF 2114KB](20)
Abstract:
The effects of chromium on γ-austenite to α-ferrite phase transformation in Nb Microalloyed steel was observed using ultra high-temperature confocal laser scanning microscopy. It is indicated that the starting temperature of the γ→α phase transformation decreases with increasing the Cr content. The hot ductility of Nb microalloyed steel is improved by adding 0.12wt% Cr. Chromium atoms inhibit the diffusion of carbon atoms, which leads to the reduction of grain boundary ferrite thickness. The proportion of high angle grain boundaries is increased by adding chromium. In particular, the proportion is up to 48.7% when the Cr content is 0.12wt%.The high angle grain boundaries hinder the crack propagation and improve the ductility of Nb microalloyed steel.
Research Article
Effects of cellulose nanocrystals on improving the acid resistance of cementitious composites in mining
Lin-ping Wu, Guang-ping Huang, Chao-shi Hu, and Wei Victor Liu
Available online 9 May 2020, https://doi.org/10.1007/s12613-020-2087-z
[Abstract](1543) [PDF 825KB](19)
Abstract:
Acid mine drainage has been an important threat to cementitious structures. To improve the acid resistance of cementitious composites used under acid mine drainage attack, this study is aimed at investigating the effect of cellulose nanocrystals (CNCs) on the acid resistance of cementitious composites. CNCs were added to the mortar mixtures as additives at cement volume ratios of 0.2%, 0.4%, 1% and 1.5%. After 28 days of standard curing, the samples were immersed in sulfuric acid with a pH of 2 for 75 days. The unconfined compressive strength (UCS) test, density, absorption and voids test and thermo-gravimetric analysis (TGA) were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion. It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength. Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures. The mixture with 0.4% CNC showed improved acid resistance due to the reduced mass change and length change after brushing.
Research Article
Highly Efficient Nanocatalyst Ni1Co9@graphene in Dehydrogen Process from Sodium Borohydride Hydrolysis
Juan Wang, Li-jun Yang, Xiao-chong Zhao, Pan Yang, Wei Cao, and Qing-song Huang
Available online 9 May 2020, https://doi.org/10.1007/s12613-020-2090-4
[Abstract](1612) [PDF 920KB](11)
Abstract:
Bimetal materials derived from transition metals can be good catalysts in some reactions. When supporting on graphene (GP), those catalysts have a remarkable performance in hydrolysis of sodium borohydride. To obtain such catalysts easily and efficiently, herein, a simple thermal reduction strategy has been used to prepare NixCo10-x series bimetal catalysts. Among all of these catalysts, Ni1Co9 is the best catalysts in catalytic performance. The turnover frequency (TOF) related to the total atoms number within the bimetallic nanoparticles reaches 603.82 mLH2·mmolbimetal-1·min-1 at 303 K. Furthermore, graphene is introduced as supporting frame. In additon, Ni1Co9@Graphene (Ni1Co9@GP) makes a large surface area and high TOF, 25534 mLH2·mmolbimetal-1·min-1 at 303 K. The Ni1Co9@GP exhibits efficiently catalytic properties for H2 generation in an alkaline solution because of their high specific surface area. Kinetic studies a high kinetic isotope effect disclosed using D2O lead to the suggestion of an oxidative addition of a O-H bond of water in the rate-determining step.
Research Article
Investigation of dielectric relaxations and conduction mechanism in Aurivillius ceramic Bi5Ti3FeO15
Rasmita Jena, K. Chandrakanta, Pikesh Pal, Md. Faruck Abdullah, S. D. Kaushik, and A. K. Singh
Available online 9 May 2020, https://doi.org/10.1007/s12613-020-2091-3
[Abstract](1633) [PDF 977KB](17)
Abstract:
Aurivillius Bi5Ti3FeO15 (BTFO) ceramic is synthesized by the generic solid-state reaction route. The room temperature X-ray diffraction (XRD) study confirms that the compound is having single-phase without any impurity. Surface morphology of the prepared sample ensures that the presence of microstructural grains with size around 0.2 to 2 µm is observed. Dielectric properties of sample are investigated as a function of frequency of about 100 Hz to 1 MHz at various temperatures (303 K ≤ T ≤ 773 K). The Nyquist plots of impedance data exhibit a semi-circular arc in high temperature region, which is explained by the equivalent electrical circuit (R1C1) (R2QC2). Our results indicate that resistance as well as capacitance of grain boundary is more prominent over the grains. Analysis of ac conductivity data is done by using Jonscher universal power law (σacdc+Aωn) which confirms that the conduction process is dominated by the hopping mechanism. The activation energies calculated for relaxation and conduction processes are very close to each other (0.32 eV to 0.53 eV) by which we conclude that the same type of charge carriers are involved in both the processes.
Research Article
Study on the shape of slab solidification end and its influence on the central-line segregation
Jie Li, Yan-hui Sun, Hang-hang An, and Pei-yuan Ni
Available online 9 May 2020, https://doi.org/10.1007/s12613-020-2089-x
[Abstract](1595) [PDF 1059KB](19)
Abstract:
A solidification model of a continuous casting slab with non-uniform cooling condition was established with the ProCAST software. The model was verified by the results of the nail shooting tests and the infrared temperature measurement equipment. It was found that the final solidification position was 220 to 440 mm away from the edge of the slab width for 200 mm × 2300 mm section based on the simulation results. In addition, four characteristic parameters were defined to evaluate the uniformity of the shape of slab solidification end. Then the effects of casting speed, superheat and secondary cooling strength on these four parameters were discussed. Moreover, the central-line segregation of slab produced with and without the soft reduction process were investigated. The results show that, the transverse flow of molten steel with low solid fraction had an important effect on the central-line segregation morphology under the soft reduction.
Research Article
Response of agglomeration and leaching behavior of copper oxides to chemical binders
Sheng-hua Yin, Lei-ming Wang, Xun Chen, and Ai-xiang Wu
Available online 24 April 2020, https://doi.org/10.1007/s12613-020-2081-5
[Abstract](1789) [PDF 1224KB](46)
Abstract:
The chemical binder is one of critical factors that affecting ore agglomeration behavior and leaching efficiency. In this study, the effect of types of binders and mass fraction of H2SO4 solution on curing, soaking and leaching behavior of agglomerations were conducted. The results showed that the Portland cement (3CaO·SiO2, 2CaO·SiO2, 3CaO·Al2O3) was the optional binder to obtain well-shape, stable structure of agglomeration. A higher extraction rate was reached using Portland cement instead of sodium silicate, gypsum and acid-proof cement. The excessive geometric mean size is not conducive to well-shaped agglomerations and desirable porosity. Relied on Computed Tomography (CT) and MATALB, the porosity of 2-D CT images in L1~L3 increased at least 4.5 % after acid leaching. Ore agglomerations started to be heavily destroyed and even disintegrate if sulfuric acid solution was higher than 30 g/L, it was caused by undesirable accumulation of reaction products and residuals.
Research Article
Effect of multi-pass friction stir processing and Mg addition on microstructure and tensile properties of Al-1050 alloy
Shahin Arshadi Rastabi and Masoud Mosallaee
Available online 24 April 2020, https://doi.org/10.1007/s12613-020-2074-4
[Abstract](1592) [PDF 3910KB](29)
Abstract:
The effect of multiple passes of friction stir processing (FSP) and the addition of Mg powder on different parts of the microstrcuture processed including the stir zone (SZ), the heat-affected zone (HAZ), and the thermo-mechanically affected zone (TMAZ) were investigated. The results of the microstructural observations revealed that although the grain size of the SZ decreased in both the non-composite and composite samples, the grain size increased in the TMAZ and the HAZ of the non-composit sample with increasing the numer of FSP passes. Besides, the addition of Mg powder resulted in much more significant grain refinement. Moreover, increasing the number of the FSP passes resulted in a more uniform distribution of Al-Mg intermetallic compounds in the in-situ composite sample. The results of the tensile testing showed that the four- passes FSPed non-composite sample exhibited a higher elongation percentage with a ductile fracture compared with those of the base metal and the four-pass composite sample while lattermost sample exhibited a brittle fracture and a higher tensile strength value than the base metal and the four-pass FSPed non-composite sample. The fabrication of composite samples resulted in noticeable enhancement of hardness compared with the base metal and the non-composite FSPed samples.
Research Article
Effect of TiB2 and Al3Ti on Microstructure, Mechanical Properties and Fracture Behaviour of Near Eutectic Al-12.6Si Alloy
Surajit Basak, Prosanta Biswas, Surajit Patra, Himadri Roy, and Manas Kumar Mondal
Available online 16 April 2020, https://doi.org/10.1007/s12613-020-2070-8
[Abstract](1283) [PDF 3373KB](33)
Abstract:
Near eutectic 12.6SiAl alloy has been developed with 0 wt%, 2 wt. %, 4 wt.% and 6 wt.% Al-5Ti-1B master alloy. Microstructural morphology, hardness, tensile strength, elongation and fracture behaviour of the alloys have been studied. The unmodified 12.6SiAl alloy has an irregular needle and platy eutectic silicon (ESi) and coarse polygonal primary silicon (PSi) particles in the matrix-like α-Al phase. The PSi, ESi and α-Al morphology and volume fraction have been changed due to the addition of Al-5Ti-1B master alloy. As an effect of microstructure modification, hardness, UTS and % elongation improved. Nano-sized in-situ Al3Ti particles and ex-situ TiB2 particles are the cause of microstructural modification. The fracture images of the developed alloys exhibit a ductile and brittle mode of fracture at the same time. The Al-5Ti-1B modified alloys have a more ductile mode of fracture and dimples compared to the unmodified one.
Research Article
Semi-solid billet prepared by the direct semi-solid isothermal treatment of cold-rolled ZL104 aluminum alloy
Yong-fei Wang, Yi Guo, Sheng-dun Zhao, and Xiao-guang Fan
Available online 16 April 2020, https://doi.org/10.1007/s12613-020-2067-3
[Abstract](1778) [PDF 1833KB](19)
Abstract:
The direct semi-solid isothermal treatment (DSSIT) process is proposed to process the cold-rolled ZL104 aluminum alloy to manufacture the semi-solid billet. The influence of two process parameters (i.e. maintained temperature and duration time) on the microstructure and hardness of the semi-solid billet (ZL104 aluminum alloy) were experimentally examined. Results revealed that the average size of grains enlarged and the shape factor was improved with an elevation in the maintained temperature. The shape factor increased with the increase in the duration time while the average grain size enlarged when the duration time was prolonged from 5 to 20 min at 570 °C. The hardness of the studied aluminum alloy decreased due to the increase in the average size of grains with raising of either the maintained temperature or the duration time. The optimal maintained temperature was obtained as 570 °C while the duration time was found as 5 min for preparing the semi-solid ZL104 aluminum alloy. Under the optimal process parameters, the average size of the grain, the shape factor, and the hardness were obtained as 35.88 µm, 0.81 and 55.24 MPa, respectively. The coarsening rate constant in the Lifshitz-Slyozov-Wagner relationship at 570 °C was found at 1357.2 μm3/s.
Research Article
Fabrication and properties of silver-based composites reinforced with carbon-coated Ti3AlC2
Yong-fa Zhu, Wu-bian Tian, Dan-dan Wang, Heng Zhang, Jian-xiang Ding, Pei-gen Zhang, and Zheng-ming Sun
Available online 12 April 2020, https://doi.org/10.1007/s12613-020-2064-6
[Abstract](1630) [PDF 1558KB](9)
Abstract:
Ti3AlC2 reinforced Ag-based composites are used as sliding current collectors, electrical contacts and electrode materials, which shows remarkable performance. However, the interfacial reactions between Ag and Ti3AlC2 significantly deteriorate the electrical and thermal properties of the composite. To alleviate the interfacial reactions, carbon-coated Ti3AlC2 particles (C@Ti3AlC2) were fabricated as reinforcement. Ag-10wt.% C@Ti3AlC2 composites with carbon layer thickness of 50-200 nm were prepared. Compared with the uncoated Ag-Ti3AlC2 composite, Ag-C@Ti3AlC2 exhibits a better distribution of Ti3AlC2 particles. With the increase of carbon layer thickness, the Vickers hardness and relative density of Ag-C@Ti3AlC2 decline gradually. The lowest resistivity of Ag-C@Ti3AlC2 reaches 29.4×10-9 Ω·m with the carbon layer thickness of 150 nm, half of the Ag-Ti3AlC2 (66.7×10-9 Ω·m). The thermal conductivity of Ag-C@Ti3AlC2 reaches a maximum value of 135.5 W·m-1·K-1 with a 200-nm carbon coating (~1.8 times over that of the Ag-Ti3AlC2). These results indicate that carbon coating method is a feasible strategy to improve the performance of Ag-C@Ti3AlC2 composites.
Research Article
Effect of organic binders in the activation and properties of indurated magnetite pellets
Cui Wang, Chen-yang Xu, Zheng-jian Liu, Yao-zu Wang, Li-ming Ma, and Rong-rong Wang
Available online 3 April 2020, https://doi.org/10.1007/s12613-020-2055-7
[Abstract](1753) [PDF 1766KB](18)
Abstract:
In the ironmaking process, adding organic binder replaces a portion of bentonite is a potential solution to improve the performance of the pellets. The interaction between the original bentonite (OB) and the organic binder was investigated. The results illustrate that the micro-morphology of the organic composite bentonite (OCB) became porous and the infrared difference spectrum was a curve. Additionally, the residual burning rates of OB and organic binder were measured, which were 82.72% and 2.30%, respectively. Finally, the influence of OCB on the properties of pellets were studied. The compressive strength of OCB-added green pellets (14.7 N/pellet) was better than that of OB-added pellets (10.3 N/pellet), and the range of melting temperature (173℃) was narrower than that of OB-added pellets (198℃). The compressive strength of OCB-added pellets increased from 2156 N/pellet to 3156 N/pellet with the roasting temperature increased from 1200℃ to 1250℃.
Research Article
Competitive precipitation behavior of hybrid reinforcements in copper matrix composites fabricated by powder metallurgy
Tao Lan, Yi-hui Jiang, Xiao-jun Zhang, Fei Cao, and Shu-hua Liang
Available online 29 March 2020, https://doi.org/10.1007/s12613-020-2052-x
[Abstract](1249) [PDF 1063KB](12)
Abstract:
Copper matrix composites reinforced by in situ-formed hybrid TiB whiskers and TiB2 particles were fabricated by powder metallurgy. Microstructure observations showed that there was a competitive precipitation behavior between TiBw and TiB2p, where the relative contents of the two reinforcements varied with sintering temperature. Based on thermodynamic and kinetic assessments, the precipitation mechanisms of the hybrid reinforcements were discussed, and the formation of both TiB whiskers and TiB2 particles from the local melting zone was thermodynamically favored. The precipitation kinetics were mainly controlled by a solid-state diffusion of B atoms. By forming a compact compound layer, in situ reactions were divided into two stages, where Zener growth and Dybkov growth prevailed, respectively. Accordingly, the competitive precipitation behavior was attributed to the transition of the growth model during the reaction process.
Research Article
Interface microstructure and formation mechanism of ultrasonic spot welding for Al-Ti dissimilar metals
Li Zhou, Shan Liu, Jie Min, Zhi-Wei Qin, Wen-Xiong He, Xiao-Guo Song, Hong-Bo Xu, and Ji-Cai Feng
Available online 20 March 2020, https://doi.org/10.1007/s12613-020-2043-y
[Abstract](1730) [PDF 1002KB](12)
Abstract:
The AA6061 Al and commercial pure Ti were welded by ultrasonic spot welding (USW). The focus of this investigation is the interface microstructure and joint formation. The Al-Ti USW joints were welded at the welding energy of 1100 J~ 3200 J. The joint appearance and interface microstructure were observed mainly by Optical microscope (OM) and field emission scanning electron microscope (SEM) The results indicated that good joint only can be achieved with proper welding energy of 2150 J. No significant intermetallic compound (IMC) was found under all conditions. The high energy barriers of Al-Ti and difficulties in diffusion were the main reasons for the absence of IMC according to kinetic analysis. The heat input is crucial for the material plastic flow and bonding area which plays an important role in the joint formation.
Research Article
Oxidation pathway and kinetics of titania slag powders during cooling process in air
Wen-chao He, Cheng-yi Ding, Xue-wei Lv, and Zhi-ming Yan
Available online 20 February 2020, https://doi.org/10.1007/s12613-020-2019-y
[Abstract](1677) [PDF 1923KB](22)
Abstract:
The oxidation pathway and kinetics of titania slag powders in air were analyzed through differential scanning calorimetry (DSC) and thermogravimetry (TG). The oxidation pathway of titania slag powders in air is divided into three stages according to three exothermic peaks and three corresponding mass gain stages displayed in the non-isothermal DSC and TG curves respectively. The isothermal oxidation kinetics of high titania slag powders with different sizes were analyzed through ln-ln analysis method. The entire isothermal oxidation process includes the following two stages. The kinetic mechanism of first stage is described as f(α)=1.77(1-α)[-ln(1-α)]((1.77-1)/1.77),f(α)=1.97(1-a)[-ln(1-a)]((1.97-1)/1.97), and f(α)=1.18(1-α)[-ln(1-α)]((1.18-1)/1.18); whereas the kinetic mechanism of second stage for all samples can be described as[1-(1-α)(1/3)]2=kt. The activation energies of titania slag powders with different sizes (d1 < 0.075 mm, 0.125 < d2 < 0.150 mm, and 0.425 < d3 < 0.600 mm) at different reaction degrees are calculated. Under the current experimental conditions, the rate-controlling step at the first oxidation stage of all samples is a chemical reaction. The rate-controlling steps at the second oxidation stage are the chemical reaction and internal diffusion (d1<0.075 mm) and the internal diffusion (0.125 < d2 < 0.150 mm and 0.425 < d3 < 0.600 mm).
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Research Article
Hydrogen effect on the mechanical behaviour and microstructural features of a Fe–Mn–C twinning induced plasticity steel
Xiaofei Guo, Stefan Zaefferer, Fady Archie, and Wolfgang Bleck
  Available online 23 March 2021, https://doi.org/10.1007/s12613-021-2284-4
[FullText HTML](35) [PDF 21314KB](4) SpringerLink
Abstract:
The influences of hydrogen on the mechanical properties and the fracture behaviour of Fe–22Mn–0.6C twinning induced plasticity steel have been investigated by slow strain rate tests and fractographic analysis. The steel showed high susceptibility to hydrogen embrittlement, which led to 62.9% and 74.2% reduction in engineering strain with 3.1 and 14.4 ppm diffusive hydrogen, respectively. The fracture surfaces revealed a transition from ductile to brittle dominated fracture modes with the rising hydrogen contents. The underlying deformation and fracture mechanisms were further exploited by examining the hydrogen effects on the dislocation substructure, stacking fault probability, and twinning behaviour in pre-strained slow strain rate test specimens and notched tensile specimens using coupled electron channelling contrast imaging and electron backscatter diffraction techniques. The results reveal that the addition of hydrogen promotes planar dislocation structures, earlier nucleation of stacking faults, and deformation twinning within those grains which have tensile axis orientations close to <111>//rolling direction and <112>//rolling direction. The developed twin lamellae result in strain localization and micro-voids at grain boundaries and eventually lead to grain boundary decohesion.
Research Article
Multiphase-field simulation of austenite reversion in medium-Mn steels
Yan Ma, Rui Zheng, Ziyuan Gao, Ulrich Krupp, Haiwen Luo, Wenwen Song, and Wolfgang Bleck
  Available online 23 March 2021, https://doi.org/10.1007/s12613-021-2282-6
[FullText HTML](67) [PDF 1083KB](10) SpringerLink
Abstract:
Medium-Mn steels have attracted immense attention for automotive applications owing to their outstanding combination of high strength and superior ductility. This steel class is generally characterized by an ultrafine-grained duplex microstructure consisting of ferrite and a large amount of austenite. Such a unique microstructure is processed by intercritical annealing, where austenite reversion occurs in a fine martensitic matrix. In the present study, austenite reversion in a medium-Mn alloy was simulated by the multiphase-field approach using the commercial software MICRESS® coupled with the thermodynamic database TCFE8 and the kinetic database MOBFE2. In particular, a faceted anisotropy model was incorporated to replicate the lamellar morphology of reversed austenite. The simulated microstructural morphology and phase transformation kinetics (indicated by the amount of phase) concurred well with experimental observations by scanning electron microscopy and in situ synchrotron high-energy X-ray diffraction, respectively.
Research Article
Influence of sample preparation on nanoindentation results of twinning-induced plasticity steel
Jia-Li Zhang and Stefan Zaefferer
  Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2260-z
[FullText HTML](197) [PDF 1139KB](5) SpringerLink
Abstract:
Nanoindentation is an attractive characterization technique, as it not only measures the local properties of a material but also facilitates understanding of deformation mechanisms at submicron scales. However, because of the complex stress–strain field and the small scale of the deformation under the nanoindenter, the results can be easily influenced by artifacts induced during sample preparation. In this work, a systematic study was conducted to better understand the influence of sample preparation methods on the nanoindentation results of ductile metals. All experiments were conducted on a steel (Fe–22Mn–0.65C, wt%) with twinning-induced plasticity (TWIP), which was selected for its large grain size and sensitivity to different surface preparation methods. By grouping the results obtained from each nanoindent, chemical polishing was found to be the best sample preparation method with respect to the resulting mechanical properties of the material. In contrast, the presence of a deformation layer left by mechanical polishing and surface damage induced by focused ion beam (FIB) scanning were confirmed by the dislocation-nucleation-induced pop-in events of nanoindentation.
Research Article
Ultrahigh cycle fatigue fracture mechanism of high-quality bearing steel obtained through different deoxidation methods
Wei Xiao, Yan-ping Bao, Chao Gu, Min Wang, Yu Liu, Yong-sheng Huang, and Guang-tao Sun
  Available online 19 January 2021, https://doi.org/10.1007/s12613-021-2253-y
[FullText HTML](2082) [PDF 3075KB](8) SpringerLink
Abstract:
The mechanism of oxide inclusions in fatigue crack initiation in the very-high cycle fatigue (VHCF) regime was clarified by subjecting bearing steels deoxidized by Al (Al-deoxidized steel) and Si (Si-deoxidized steel) to ultrasonic tension–compression fatigue tests (stress ratio, R = −1) and analyzing the characteristics of the detected inclusions. Results show that the main types of inclusions in Si- and Al-deoxidized steels are silicate and calcium aluminate, respectively. The content of calcium aluminate inclusions larger than 15 μm in Si-deoxidized steel is lower than that in Al-deoxidized steel, and the difference observed may be attributed to different inclusion generation processes during melting. Despite differences in their cleanliness and total oxygen contents, the Si- and Al-deoxidized steels show similar VHCF lives. The factors causing fatigue failure in these steels reveal distinct differences. Calcium aluminate inclusions are responsible for the cracks in Al-deoxidized steel. By comparison, most fatigue cracks in Si-deoxidized steel are triggered by the inhomogeneity of a steel matrix, which indicates that the damage mechanisms of the steel matrix can be a critical issue for this type of steel. A minor portion of the cracks in Si-deoxidized steel could be attributed to different types of inclusions. The mechanisms of fatigue fracture caused by calcium aluminate and silicate inclusions were further analyzed. Calcium aluminate inclusions first separate from the steel matrix and then trigger crack generation. Silicate inclusions and the steel matrix are closely combined in a fatigue process; thus, these inclusions have mild effects on the fatigue life of bearing steels. Si/Mn deoxidation is an effective method to produce high-quality bearing steel with a long fatigue life and good liquid steel fluidity.
Research Article
Stress-state dependence of dynamic strain aging: Thermal hardening and blue brittleness
Wenqi Liu and Junhe Lian
  Available online 13 January 2021, https://doi.org/10.1007/s12613-021-2250-1
[FullText HTML](295) [PDF 1324KB](11) SpringerLink
Abstract:
This study aims to discover the stress-state dependence of the dynamic strain aging (DSA) effect on the deformation and fracture behavior of high-strength dual-phase (DP) steel at different deformation temperatures (25–400°C) and reveal the damage mechanisms under these various configurations. To achieve different stress states, predesigned specimens with different geometric features were used. Scanning electron microscopy was applied to analyze the fracture modes (e.g., dimple or shear mode) and underlying damage mechanism of the investigated material. DSA is present in this DP steel, showing the Portevin–Le Chatelier (PLC) effect with serrated flow behavior, thermal hardening, and blue brittleness phenomena. Results show that the stress state contributes distinctly to the DSA effect in terms of the magnitude of thermal hardening and the pattern of blue brittleness. Either low stress triaxiality or Lode angle parameter promotes DSA-induced blue brittleness. Accordingly, the damage mechanisms also show dependence on the stress states in conjunction with the DSA effect.
Research Article
Determining role of heterogeneous microstructure in lowering yield ratio and enhancing impact toughness in high-strength low-alloy steel
Yi-shuang Yu, Bin Hu, Min-liang Gao, Zhen-jia Xie, Xue-quan Rong, Gang Han, Hui Guo, and Cheng-jia Shang
  Available online 8 December 2020, https://doi.org/10.1007/s12613-020-2235-5
[FullText HTML](463) [PDF 1357KB](25) SpringerLink
Abstract:
Here we present a novel approach of intercritical heat treatment for microstructure tailoring, in which intercritical annealing is introduced between conventional quenching and tempering. This induced a heterogeneous microstructure consisting of soft intercritical ferrite and hard tempered martensite, resulting in a low yield ratio (YR) and high impact toughness in a high-strength low-alloy steel. The initial yielding and subsequent work hardening behavior of the steel during tensile deformation were modified by the presence of soft intercritical ferrite after intercritical annealing, in comparison to the steel with full martensitic microstructure. The increase in YR was related to the reduction in hardness difference between the soft and hard phases due to the precipitation of nano-carbides and the recovery of dislocations during tempering. The excellent low-temperature toughness was ascribed not only to the decrease in probability of microcrack initiation for the reduction of hardness difference between two phases, but also to the increase in resistance of microcrack propagation caused by the high density of high angle grain boundaries.
Research Article
Effect of weld microstructure on brittle fracture initiation in the thermally-aged boiling water reactor pressure vessel head weld metal
Noora Hytönen, Zai-qing Que, Pentti Arffman, Jari Lydman, Pekka Nevasmaa, Ulla Ehrnstén, and Pål Efsing
  Available online 26 November 2020, https://doi.org/10.1007/s12613-020-2226-6
[FullText HTML](438) [PDF 1625KB](13) SpringerLink
Abstract:
Effects of the weld microstructure and inclusions on brittle fracture initiation are investigated in a thermally aged ferritic high-nickel weld of a reactor pressure vessel head from a decommissioned nuclear power plant. As-welded and reheated regions mainly consist of acicular and polygonal ferrite, respectively. Fractographic examination of Charpy V-notch impact toughness specimens reveals large inclusions (0.5–2.5 μm) at the brittle fracture primary initiation sites. High impact energies were measured for the specimens in which brittle fracture was initiated from a small inclusion or an inclusion away from the V-notch. The density, geometry, and chemical composition of the primary initiation inclusions were investigated. A brittle fracture crack initiates as a microcrack either within the multiphase oxide inclusions or from the debonded interfaces between the uncracked inclusions and weld metal matrix. Primary fracture sites can be determined in all the specimens tested in the lower part of the transition curve at and below the 41-J reference impact toughness energy but not above the mentioned value because of the changes in the fracture mechanism and resulting changes in the fracture appearance.
Research Article
In-depth analysis of the fatigue mechanism induced by inclusions for high-strength bearing steels
Chao Gu, Wen-qi Liu, Jun-he Lian, and Yan-ping Bao
  Available online 17 November 2020, https://doi.org/10.1007/s12613-020-2223-9
[FullText HTML](424) [PDF 2278KB](20) SpringerLink
Abstract:
A numerical study of stress distribution and fatigue behavior in terms of the effect of voids adjacent to inclusions was conducted with finite element modeling simulations under different assumptions. Fatigue mechanisms were also analyzed accordingly. The results showed that the effects of inclusions on fatigue life will distinctly decrease if the mechanical properties are close to those of the steel matrix. For the inclusions, which are tightly bonded with the steel matrix, when the Young’s modulus is larger than that of the steel matrix, the stress will concentrate inside the inclusion; otherwise, the stress will concentrate in the steel matrix. If voids exist on the interface between inclusions and the steel matrix, their effects on the fatigue process differ with their positions relative to the inclusions. The void on one side of an inclusion perpendicular to the fatigue loading direction will aggravate the effect of inclusions on fatigue behavior and lead to a sharp stress concentration. The void on the top of inclusion along the fatigue loading direction will accelerate the debonding between the inclusion and steel matrix.
Research Article
Reduction of residual stress in porous Ti6Al4V by in situ double scanning during laser additive manufacturing
Yi-wa Luo, Ming-yong Wang, Ji-guo Tu, Yu Jiang, and Shu-qiang Jiao
  Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2212-z
[FullText HTML](562) [PDF 1176KB](27) SpringerLink
Abstract:
Selective laser melting (SLM) technology plays an important role in the preparation of porous titanium (Ti) implants with complex structures and precise sizes. Unfortunately, the processing characteristics of this technology, which include rapid melting and solidification, lead to products with high residual stress. Herein, an in situ method was developed to restrain the residual stress and improve the mechanical strength of porous Ti alloys during laser additive manufacturing. In brief, porous Ti6Al4V was prepared by an SLM three-dimensional (3D) printer equipped with a double laser system that could rescan each layer immediately after solidification of the molten powder, thus reducing the temperature gradient and avoiding rapid melting and cooling. Results indicated that double scanning can provide stronger bonding conditions for the honeycomb structure and improve the yield strength and elastic modulus of the alloy. Rescanning with an energy density of 75% resulted in 33.5%–38.0% reductions in residual stress. The porosities of double-scanned specimens were 2%–4% lower than those of single-scanned specimens, and the differences noted increased with increasing sheet thickness. The rescanning laser power should be reduced during the preparation of porous Ti with thick cell walls to ensure dimensional accuracy.
Invited Review
Medium-Mn steels for hot forming application in the automotive industry
Shuo-shuo Li and Hai-wen Luo
  Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2179-9
[FullText HTML](1322) [PDF 1328KB](26) SpringerLink
Abstract:
Advanced high-strength steels have been widely used to improve the crashworthiness and lightweight of vehicles. Different from the popular cold stamping, hot forming of boron-alloyed manganese steels, such as 22MnB5, could produce ultra-high-strength steel parts without springback and with accurate control of dimensions. Moreover, hot-formed medium-Mn steels could have many advantages, including better mechanical properties and lower production cost, over hot-formed 22MnB5. This paper reviews the hot forming process in the automotive industry, hot-formed steel grades, and medium-Mn steel grades and their application in hot forming in depth. In particular, the adaptabilities of medium-Mn steels and the presently popular 22MnB5 into hot forming were compared thoroughly. Future research should focus on the technological issues encountered in hot forming of medium-Mn steels to promote their commercialization.
Research Article
Influence of gas-diffusion-layer current collector on electrochemical performance of Ni(OH)2 nanostructures
Thongsuk Sichumsaeng, Nutthakritta Phromviyo, and Santi Maensiri
  Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2174-1
[FullText HTML](1155) [PDF 1291KB](16) SpringerLink
Abstract:
We report the electrochemical performance of Ni(OH)2 on a gas diffusion layer (GDL). The Ni(OH)2 working electrode was successfully prepared via a simple method, and its electrochemical performance in 1 M NaOH electrolyte was investigated. The electrochemical results showed that the Ni(OH)2/GDL provided the maximum specific capacitance value (418.11 F·g−1) at 1 A·g−1. Furthermore, the Ni(OH)2 electrode delivered a high specific energy of 17.25 Wh·kg−1 at a specific power of 272.5 W·kg−1 and retained about 81% of the capacitance after 1000 cycles of galvanostatic charge–discharge (GCD) measurements. The results of scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed the occurrence of sodium deposition after long-time cycling, which caused the reduction in the specific capacitance. This study results suggest that the light-weight GDL, which can help overcome the problem of the oxide layer on metal–foam substrates, is a promising current collector to be used with Ni-based electroactive materials for energy storage applications.
Research Article
New insights into the properties of high-manganese steel
Wolfgang Bleck
  Available online 14 August 2020, https://doi.org/10.1007/s12613-020-2166-1
[FullText HTML](968) [PDF 1606KB](28) SpringerLink
Abstract:
In the Collaborative Research Centre 761’s “Steel ab initio - quantum mechanics guided design of new Fe based materials,” scientists and engineers from RWTH Aachen University and the Max Planck Institute for Iron Research conducted research on mechanism-controlled material development with a particular focus on high-manganese alloyed steels. From 2007 to 2019, a total of 55 partial projects and four transfer projects with industrial participation (some running until 2021) have studied material and process design as well as material characterization. The basic idea of the Collaborative Research Centre was to develop a new methodological approach to the design of structural materials. This paper focuses on selected results with respect to the mechanical properties of high-manganese steels, their underlying physical phenomena, and the specific characterization and modeling tools used for this new class of materials. These steels have microstructures that require characterization by the use of modern methods at the nm-scale. Along the process routes, the generation of segregations must be taken into account. Finally, the mechanical properties show a characteristic temperature dependence and peculiarities in their fracture behavior. The mechanical properties and especially bake hardening are affected by short-range ordering phenomena. The strain hardening can be adjusted in a never-before-possible range, which makes these steels attractive for demanding sheet-steel applications.
Research Article
Gold-leaching performance and mechanism of sodium dicyanamide
Gen-zhuang Li, Jue Kou, Yi Xing, Yang Hu, Wei Han, Zi-yuan Liu, and Chun-bao Sun
  Available online 26 July 2020, https://doi.org/10.1007/s12613-020-2153-6
[FullText HTML](1488) [PDF 3473KB](18) SpringerLink
Abstract:
In this work, sodium dicyanamide (SD) was used as a leaching reagent for gold recovery, and the effects of the SD dosage and solution pH on the gold-leaching performance were investigated. A gold recovery of 34.8% was obtained when SD was used as the sole leaching reagent at a dosage of 15 kg/t. In the presence of a certain amount of potassium ferrocyanide (PF) in the SD solution, the gold recovery was found to increase from 34.8% to 57.08%. Using the quartz crystal microbalance with dissipation (QCM-D) technique, the leaching kinetics of SD with and without PF were studied. The QCM-D results indicate that the gold-leaching rate increased from 4.03 to 39.99 ng·cm–2·min–1 when the SD concentration was increased from 0 to 0.17 mol/L, and increased from 39.99 to 272.62 ng·cm–2·min–1 when 0.1 mol/L of PF was used in combination with SD. The pregnant solution in the leaching tests was characterized by X-ray photoelectron spectroscopy and electrospray mass spectrometry, which indicated that Au and (N(CN)2) in the SD solution formed a series of metal complex ions, [AuNax(N(CN)2)x+2] (x = 1, 2, 3, or 4).
Research Article
Recovery of gold from refractory gold ores: Effect of pyrite on the stability of the thiourea leaching system
Hong Qin, Xue-yi Guo, Qing-hua Tian, and Lei Zhang
  Available online 12 July 2020, https://doi.org/10.1007/s12613-020-2142-9
[FullText HTML](1668) [PDF 988KB](29) SpringerLink
Abstract:
The extraction of gold from refractory gold ores (RGOs) without side reactions is an extremely promising endeavor. However, most RGOs contain large amounts of sulfide, such as pyrite. Thus, investigation of the influence of sulfide on the gold leaching process is important to maximize the utilization of RGOs. In this work, the effects of pyrite on the stability of the thiourea system were systematically investigated under different conditions. Results showed that the decomposition rate of thiourea was accelerated sharply in the presence of pyrite. The effect of pyrite on gold recovery in thiourea leaching systems was then confirmed via a series of experiments. The decomposition efficiency of thiourea decreased by 40% and the recovery efficiency of gold increased by 56% after the removal of sulfide by roasting. Under optimal conditions, the efficiency of the gold recovery system increased to 83.69% and only 57.92% of thiourea decomposition was observed. The high consumption of thiourea by the leaching system may be attributed to not only adsorption by mineral particles but also catalytic decomposition by some impurities in the ores, such as pyrite and soluble ferric oxide.
Research Article
Improvement of the microstructural features and mechanical properties of advanced high-strength steel DP590 welds
Arian Ghandi, Morteza Shamanian, Mohamad Reza Salmani, and Jalal Kangazian
  Available online 17 June 2020, https://doi.org/10.1007/s12613-020-2117-x
[FullText HTML](1196) [PDF 20682KB](37) SpringerLink
Abstract:
The effects of the welding current mode in resistance spot welding on the microstructure and mechanical properties of advanced high-strength steel dual-phase 590 (DP590) sheets were investigated. Results showed that a rough martensitic structure was formed in the weld zone of the sample welded via the single-pulsed mode, whereas the microstructure in the heat-affected zone consisted of a very rough martensitic microstructure and rough ferrite. However, using the secondary pulse mode led to the formation of tempered martensite in the weld zone. The maximum load and the energy absorption to failure of the samples with the secondary pulsed cycle were higher than those of the samples with the single-pulsed mode. Tensile shear results indicated that the secondary pulsed mode could significantly change the mode of failure upon shear tension testing. Therefore, the obtained results suggest that the use of secondary pulsed mode can improve the microstructural feature and mechanical properties of advanced high-strength steel DP590 welds.
Research Article
Sliding wear behaviour of Fe/316L/430–Ti(C,N) composites prepared via spark plasma sintering and subsequent heat treatment
Dao-ying Chen, Ying Liu, Ren-quan Wang, and Jin-wen Ye
  Available online 27 May 2020, https://doi.org/10.1007/s12613-020-2108-y
[FullText HTML](1618) [PDF 1364KB](36) SpringerLink
Abstract:
A series of novel steel–Ti(C,N) composites was fabricated by spark plasma sintering (SPS) and subsequent heat treatment. The hardness, indentation fracture resistance, and wear behaviour of the steel–Ti(C,N) composites were compared with those of the unreinforced samples, and their potentials were assessed by comparison with traditional cermet/hardmetal systems. The results showed that with the addition of 20wt% Ti(C,N), the wear rates of the newly examined composites reduced by a factor of about 2 to 4 and were comparable to those of cermets and hardmetals. The martensitic transformation of the steel matrix and the formation of in situ carbides induced by heat treatment enhanced the wear resistance. Although the presence of excessive in situ carbides improved the hardness, the low indentation fracture resistance (IFR) value resulted in brittle fracture, which in turn resulted in poor wear property. Moreover, the operative wear mechanisms were investigated. This study provides a practical and cost-effective approach to prepare steel–Ti(C,N) composites as potential wear-resistant materials.
Research Article
Bonding of compound casted Ti/Al bimetal by heat treatment
M. Fadaeinia and Ramin Raiszadeh
  Available online 27 May 2020, https://doi.org/10.1007/s12613-020-2107-z
[FullText HTML](1655) [PDF 1421KB](14) SpringerLink
Abstract:
The formation mechanism of the bonding between compound cast Al/Ti bimetal during a heat treatment regime was investigated. Commercially pure Al was cast and melt on a Ti bar in a steel tube, followed by heat treatment on the compound cast Ti/Al bimetal for different periods of time once the Al melt was solidified. No bonding was observed between the two metals after the initial casting, which can be attributed to the presence of oxide films on the liquid Al and solid Ti alloys and the trapped atmosphere between them. The effect of these layers in preventing the formation of bonding was eliminated after heat treating the cast part at ~973 K (~700°C) for at least 15 min, and the metals started to bond with each other. A detailed description of this bonding mechanism is presented in this paper.
Research Article
Micromorphology and safety properties of meager and meager-lean coal for blast furnace injection
Long-zhe Jin and Xiao-meng Niu
  Available online 21 May 2020, https://doi.org/10.1007/s12613-020-2104-2
[FullText HTML](1620) [PDF 779KB](9) SpringerLink
Abstract:
Four types of meager and meager-lean coal and one type of high-quality anthracite were selected based on the safety requirements for blast furnace coal injection and domestic coal quality to conduct microstructure and component analyses. The analyses of the organic and inorganic macerals and the chemical compositions of the selected coal samples indicate that the four types of meager and meager-lean coal have low volatilization, low ash content, and low sulfur content; these qualities are suitable for blast furnace injection. Grindability test was conducted on the four types of meager and meager-lean coal and the anthracite mixed coal samples. Results indicate that the mixture of meager and meager-lean coal and anthracite is beneficial to improve the grindability of pulverized coal. The explosive tests reveal that the selected coal samples are non-explosive or weakly explosive. When the proportion of meager and meager-lean coal is less than 40wt%, the mixed coal powder would not explode during the blowing process. The minimum ignition temperature test determines that the minimum ignition temperatures of the four types of meager and meager-lean coal and anthracite are 326, 313, 310, 315, and 393°C, respectively. This study provides a guiding research idea for the safety of meager and meager-lean coal used in blast furnace injection.
Research Article
Effects of CeO2 pre-calcined at different temperatures on the performance of Pt/CeO2–C electrocatalyst for methanol oxidation reaction
Guo-qing Li, Pu-kang Wen, Chen-qiang Gao, Tian-yi Zhang, Jun-yang Hu, Yu-hao Zhang, Shi-you Guan, Qing-feng Li, and Bing Li
  Available online 24 April 2020, https://doi.org/10.1007/s12613-020-2076-2
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Abstract:
Pt/CeO2–C catalysts with CeO2 pre-calcined at 300–600°C were synthesized by combining hydrothermal calcination and wet impregnation. The effects of the pre-calcined CeO2 on the performance of Pt/CeO2–C catalysts in methanol oxidation were investigated. The Pt/CeO2–C catalysts with pre-calcined CeO2 at 300–600°C showed an average particle size of 2.6–2.9 nm and exhibited better methanol electro-oxidation catalytic activity than the commercial Pt/C catalyst. In specific, the Pt/CeO2–C catalysts with pre-calcined CeO2 at 400°C displayed the highest electrochemical surface area value of 68.14 m2·g−1 and If/Ib ratio (the ratio of the forward scanning peak current density (If) and the backward scanning peak current density (Ib)) of 1.26, which are considerably larger than those (53.23 m2·g−1 and 0.79, respectively) of the commercial Pt/C catalyst, implying greatly enhanced CO tolerance.
Research Article
Comparative characterization of iridium loading on catalyst assessment under different conditions
Zahra Amirsardari, Akram Dourani, Mohamad Ali Amirifar, and Nooredin Ghadiri Massoom
  Available online 3 April 2020