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Research Article
A new process for treating boron-bearing iron ore by flash reduction coupled with magnetic separation
Qipeng Bao, Lei Guo, Hong Sohn, Feng Liu, Yongliang Gao, and Zhancheng Guo
Available online 29 September 2023, https://doi.org/10.1007/s12613-023-2756-9
[Abstract](0) [PDF 2278KB](0)
Boron is an important industrial raw material, and its sources are often minerals with different compounds co-crystallized, making it difficult to achieve separation of different mineral phases through conventional beneficiation processes. This article proposes a new process for treating boron-bearing iron concentrate, called the flash reduction melting separation (FRMS). In this method, the concentrate was first flash-reduced at a temperature under which the particles melt and the slag and the reduced iron phases were disengaged at the particle scale. And good reduction and melting effects could be achieved above 1550℃. The B2O3 content in the separated slag could reach over 18wt%, while the B content in the iron was less than 0.03wt%. The FRMS process was tested to investigate the effects of factors such as ore particle size and temperature on the reduction and melting steps with and without pre-reducing the raw concentrate. A comprehensive analysis on the mineral phase transformation and morphology evolution in the ore particles during the FRMS process was also conducted.
Research Article
Flotation separation of scheelite from calcite using luteolin as a novel depressant
Xiaokang Li, Ying Zhang, Haiyang He, Yu Wu, Danyu Wu, and Zhenhao Guan
Available online 28 September 2023, https://doi.org/10.1007/s12613-023-2755-x
[Abstract](5) [PDF 1262KB](2)

Abstract: This paper proposes luteolin (LUT) as a novel depressant for the flotation-based separation of scheelite and calcite in a sodium oleate system. The suitability of LUT as a calcite depressant is confirmed through micro-flotation testing. At a pH of 9, with LUT concentration at 50 mg/L and sodium oleate concentration at 50 mg/L, scheelite recovery reaches 80.3%. Calcite, on the other hand, exhibits a recovery rate of 17.6%, indicating a significant difference in floatability between the two minerals. Subsequently, the surface modifications of scheelite and calcite following LUT treatment are characterized using adsorption capacity testing, Zeta potential analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The study investigates the selective depressant mechanism of LUT on calcite. Adsorption capacity testing and Zeta potential analysis demonstrate substantial absorption of LUT on the surface of calcite, thereby impeding the further adsorption of sodium oleate, while its impact on scheelite is minimal. FTIR and XPS analyses reveal the selective adsorption of LUT onto the surface of calcite, forming strong chemisorption bonds between the hydroxyl group and calcium ions present. AFM directly illustrates the distinct adsorption densities of LUT on the two mineral types. Consequently, luteolin can effectively serve as a depressant for calcite, enabling the successful separation of scheelite and calcite.

Invited Review
Structural properties of residual carbon in coal gasification fine slag and their influence on flotation separation and resource utilization: A review
Rui Han, Anning Zhou, Ningning Zhang, Kaiqiang Guo, Mengyan Cheng, Heng Chen, and Cuicui Li
Available online 28 September 2023, https://doi.org/10.1007/s12613-023-2753-z
[Abstract](3) [PDF 1263KB](2)

Coal gasification fine slag (FS) is a typical solid waste generated in the coal gasification process, and its current disposal methods of stockpiling and landfilling have caused serious soil and ecological hazards. Separation recovery and high-value utilization of residual carbon (RC) in FS is the key to realize the win-win situation of coal chemical industry in terms of economic and environmental benefits. The structural properties such as pore structure, surface functional group structure, and microcrystalline structure of RC in FS (FS-RC) not only affect the flotation recovery efficiency of FS-RC, but also form the basis for the high-value utilization of FS-RC. In this paper, the characteristics of FS-RC in terms of pore structure, surface functional groups, and microcrystalline structure are sorted out from the type of gasification process and the particle size of FS, and the reasons for the formation of its special structural properties are analyzed, and its influence on flotation separation and high-value utilization of FS-RC is summarized. Based on the pore structure characteristics of FS-RC, it is proposed that separation methods such as "ultrasonic pretreatment - pore blocking flotation" and "pore breaking - flocculation flotation" may be the key development technology to improve the FS-RC recovery in the future; based on the surface structure and microcrystalline structure of FS-RC, it is proposed that design of low-cost, low-dose collectors containing polar bond is an important breakthrough point to strengthen the flotation efficiency of FS-RC in the future. High-value utilization of FS should be based on the physicochemical structural properties of FS-RC, and should focus on the environmental impact of hazardous elements and the recyclability of chemical waste liquid to form an environmentally friendly utilization method. This review is of great theoretical significance for the comprehensive understanding of the unique structural properties of FS-RC, the breakthrough of the technological bottleneck in the efficient flotation separation of FS, as well as the expansion of the field of high value-added utilization of FS-RC.

Invited Review
Review on plastic instability of medium-Mn steels for concluding mechanisms for formation of Lüders and Portevin-Le Chatelier bands
Bin Hu, Han Sui, Qinghua Wen, Zheng Wang, Alexander Gramlich, and Haiwen Luo
Available online 28 September 2023, https://doi.org/10.1007/s12613-023-2751-1
[Abstract](41) [PDF 1486KB](6)

Plastic instability, including both the discontinuous yielding and stress serrations, has been frequently observed during the tensile deformation of medium Mn steels (MMnS) and then be intensively studied recently. Unfortunately, many research results are controversial and a universal agreement has not been made yet. Here we first summarized all the possible factors that affect the yielding and the flow stress serrations in MMnS, including the morphology and stability of austenite, the feature of phase interface, and the deformation parameters; and then tried to propose a universal mechanism to explain the conflicting experimental results. We conclude that the discontinuous yielding is attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation, while the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite. Strain induced martensitic transformation, influenced by mechanical stability of austenite grain and deformation parameters, should not be the intrinsic cause of plastic instability but it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations, and the interaction between the interstitial atoms and dislocations in austenite grains.

Invited Review
State of the art in oxide metallurgy technology for improving weldability of high-strength low alloy steel
Tingting Li and Jian Yang
Available online 28 September 2023, https://doi.org/10.1007/s12613-023-2754-y
[Abstract](2) [PDF 1779KB](1)

The mechanisms of oxide metallurgy technology include inducing IAF using micron-sized inclusions and restricting the growth of prior austenite grains (PAGs) by nano-sized particles during the welding process. The typical oxide metallurgy technologies include the HTUFF technology, JFE EWEL, KST technology, the ETISD technology, and so on. The complex deoxidation of Ti with other strong deoxidant elements such as Mg, Ca, Zr and rare earth metals (REM) can improve the HAZ toughness. The Mg addition is more effective in promoting the precipitation of TiN particles to refine the PAG size. The Ca addition can effectively improve the IAF nucleation due to the formation of Ca oxysulfide. Zr-containing inclusions are also effective in inducing IAF nucleation. REM can refine precipitates and induce IAF. Increasing C, Si, Al, Nb, Cr content will all impair the HAZ toughness. Higher C content usually increase the number of coarse carbides and decrease the potency of the IAF formation. The Si and Cr addition both lead to the formation of undesirable microstructures. The high Al content in steel is not beneficial to the IAF nucleation due to the formation of Al2O3 inclusions. Nb is soluble in TiN particles to form (Ti,Nb)(C,N) particles which have poor high-temperature stability. On the other hand, Mo, V and B can enhance the HAZ toughness. Mo-containing precipitates seem to present better thermal stability, and increasing Mo content can refine precipitates. VN or V(C, N) prefers to be effective in promoting the nucleation of IAF due the good crystallographic coherent relationship with ferrite. The segregation of B atoms at the PAG boundary and the B depleted zone around inclusion will promote the formation of IAF.

Research Article
Mechanism of microarc oxidation on AZ91D alloy induced by β-Mg17Al12 phase
Dajun Zhai, Xiaoping Li, and Jun Shen
Available online 28 September 2023, https://doi.org/10.1007/s12613-023-2752-0
[Abstract](1) [PDF 2369KB](1)

We proposed a strategy of indirectly inducing uniform microarc discharge by controlling the content and distribution of β-Mg17Al12 phase in AZ91D Mg alloy. Two kinds of nano-particles (ZrO2 or TiO2) were designed to be added into the substrate of Mg alloy by friction stir processing (FSP). Then, Mg alloy sample designed with different precipitated morphology of β-Mg17Al12 phase was treated by microarc oxidation (MAO) in Na3PO4/Na2SiO3 electrolyte. The characteristics and performance of the MAO coating was analyzed using scanning electron microscopy, energy dispersive spectrometer, X-ray diffraction, X-ray photoelectron spectroscopy, contact angle meter, and potentiodynamic polarization. It was found that the coarse α-Mg grains in extruded AZ91D Mg alloy were refined by FSP, and the β-Mg17Al12 phase with reticular structure was broken and dispersed. The nano-ZrO2 particles were pinned at the grain boundary by FSP, which refined the α-Mg grain and promoted the precipitation of β-Mg17Al12 phase in grains. It effectively inhibited the “cascade” phenomenon of microarcs, which induced the uniform distribution of discharge pores. The MAO coating on Zr-FSP sample had good wettability and corrosion resistance. However, TiO2 particles was hardly detected in the coating on Ti-FSP sample.

Research Article
Effects of conductive agent type on lithium extraction from salt lake brine of LiFePO4 electrode
Zhen Zhang, Pan Luo, Yan Zhang, Yuhan Wang, Li Liao, Bo Yu, Mingshan Wang, Junchen Chen, Bingshu Guo, and Xing Li
Available online 20 September 2023, https://doi.org/10.1007/s12613-023-2750-2
[Abstract](30) [PDF 1517KB](7)

Electrochemical lithium extraction from salt lake is an effective strategy for obtaining lithium resources with low cost. Nevertheless, the elevated magnesium (Mg) to lithium (Li) ratio in salt lake brines, along with the presence of numerous coexisting ions, gives rise to challenges such as prolonged lithium extraction periods, diminished lithium extraction efficiency, and significant environmental pollution. In this work, Lithium iron phosphate (LiFePO4) serves as the electrode material for electrochemical lithium extraction. By adjusting the type of conductive agent, optimization of the conductive network for the LiFePO4 electrode is achieved, resulting in a high lithium extraction efficiency and extended cycle life. Replacing the single conductive agent of Acetylene black (AB) or Multi-walled carbon nanotubes (MWCNTs) by the mixture conductive agent of AB/MWCNTs, the average diffusion coefficient of Li+ in the electrode increased from 2.35×10-9 cm2 s-1 to 4.21×10-9 cm2 s-1. Under the current density of 20 mA g-1, the average capacity of lithium extraction increased from 30.36 mg (Li)/g (LiFePO4) of the single conductive electrode to 35.62 mg (Li)/g (LiFePO4), and the efficiency of lithium extraction was significantly improved. Using the mixed conductive agent, the capacity retention of the electrode after 30 cycles reaches 83.0%, which is much higher than that of the single conductive electrode of 65.8%, meanwhile the mixed conductive agent of AB/MWCNTs shows a better cycling performance. Reducing the content of conductive agent or increasing the loading capacity, the mixed conductive agent electrode still shows an excellent electrochemical performance. Furthermore, a self-designed, highly efficient, continuous lithium extraction device is constructed, in which the electrode utilizing the AB/MWCNTs mixed conductive agent maintains excellent adsorption capacity and cycling performance.  This work provides a new perspective for electrochemical extraction of lithium using LiFePO4 electrode.

Research Article
Growth kinetics of titanium carbide coating by molten salt synthesis process on graphite sheet surface
Xiaoyu Shi, Chongxiao Guo, Jiaomiao Ni, Songsong Yao, Liqing Wang, Yue Liu, and Tongxiang Fan
Available online 20 September 2023, https://doi.org/10.1007/s12613-023-2749-8
[Abstract](12) [PDF 949KB](5)

The synthesis of carbide coatings on graphite substrates using molten salt synthesis (MSS), has garnered significant interest due to its cost-effective nature. This study investigates the reaction process and growth kinetics involved in MSS, shedding light on key aspects of the process. The involvement of Ti powder through liquid-phase mass transfer is revealed, where the diffusion distance and quantity of Ti powder play a crucial role in determining the reaction rate by influencing the C concentration gradient on both sides of the carbide. Furthermore, the growth kinetics of the carbide coating are predominantly governed by the diffusion behavior of C within the carbide layer, rather than the chemical reaction rate. To analyze the kinetics, the thickness of the carbide layer is measured with respect to heat treatment time and temperature, unveiling a parabolic relationship within the temperature range of 700~1300℃. The estimated activation energy for the reaction is determined to be 179, 283 J mol−1. These findings offer valuable insights into the synthesis of carbide coatings via MSS, facilitating their optimization and enhancing our understanding of their growth mechanisms and properties for various applications.

Research Article
Porous TiFe2 intermetallic compound fabricated via elemental powder reactive synthesis
Qian Zhao, Zhenli He, Yuehui He, Yue Qiu, Zhonghe Wang, and Yao Jiang
Available online 20 September 2023, https://doi.org/10.1007/s12613-023-2748-9
[Abstract](7) [PDF 1366KB](1)

Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis. Herein, porous TiFe2 intermetallics were fabricated by the reactive synthesis of elemental powders. The phase transformation and pore formation of porous TiFe2 intermetallics were investigated, and its corrosion behavior and hydrogen evolution reaction (HER) performance in alkali solution were studied. Porous TiFe2 intermetallics with porosity in the range of 34.4% - 56.4% were synthesized by the diffusion reaction of Ti and Fe elements, and the pore formation of porous TiFe2 intermetallic compound is the result of a combination of the bridging effect and the Kirkendall effect. The porous TiFe2 samples exhibit better corrosion resistance compared with porous 316L stainless steel, which is related to the formation of uniform nanosheets on the surface that hinder further corrosion, and porous TiFe2 electrode shows the overpotential of 220.6 and 295.6 mV at 10 and 100 mA cm-2, suggesting a good catalytic performance. The synthesized porous Fe-based intermetallic has a controllable pore structure as well as excellent corrosion resistance, showing its potential in the field of filtration and separation.

Research Article
Microstructure and thermal properties of dissimilar M300-CuCr1Zr alloys by multi-material laser-based powder bed fusion
Xiaoshuang Li, Dmitry Sukhomlinov, and Zaiqing Que
Available online 20 September 2023, https://doi.org/10.1007/s12613-023-2747-x
[Abstract](155) [PDF 2899KB](12)

Multi-material Laser-based Powder Bed Fusion (PBF-LB) allows manufacturing of parts with 3-dimensional gradient and additional functionality in a single step. This research focuses on the combination of thermally-conductive CuCr1Zr with hard M300 tool steel. Two interface configurations were investigated, i.e. M300 on CuCr1Zr and CuCr1Zr on M300. Ultra-fine grains form at the interface due to the low mutual solubility of Cu and steel. The material mixing zone size is dependent on the configurations and tunable in the range of 0.1–0.3 mm by introducing a separate set of parameters for the interface layers. Microcracks and pores mainly occur in the transition zone. Regardless of these defects, the thermal diffusivity of bimetallic parts with 50 vol.% of CuCr1Zr significantly increases by 70–150% compared to a pure M300 part. The thermal diffusivity of CuCr1Zr and the hardness of M300 steel can be enhanced simultaneously by applying the aging heat treatment.

Research Article
Enhancing performance of low-temperature processed CsPbI2Br all-inorganic perovskite solar cells using PEO-modified TiO2
Xu Zhao, Naitao Gao, Shengcheng Wu, Shaozhen Li, and Sujuan Wu
Available online 13 September 2023, https://doi.org/10.1007/s12613-023-2742-2
[Abstract](38) [PDF 1341KB](6)

CsPbX3-based (X = I, Br, Cl) inorganic perovskite solar cells (PSCs) prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal stability. But the high trap state density and serious charge recombination between low-temperature processed TiO2 film and inorganic perovskite layer interface seriously restrict the performance of all-inorganic PSCs. Here a thin polyethylene oxide (PEO) layer is employed to modify TiO2 film to passivate traps and promote carrier collection. The impacts of PEO layer on microstructure and photoelectric characteristics of TiO2 film and related devices are systematically studied. Characterization results suggest that PEO modification can reduce the surface roughness of TiO2 film, decrease its average surface potential and passivate trap states. At optimal conditions, the champion efficiency of CsPbI2Br PSCs with PEO-modified TiO2 (PEO-PSCs) has been improved to 11.24% from 9.03% of reference PSCs. Moreover, the hysteresis behavior and charge recombination have been suppressed in PEO-PSCs.

Research Article
Exploring the potential of olivine-containing copper-nickel slag for carbon dioxide mineralization in cementitious materials
Qianqian Wang, Zequn Yao, Lijie Guo, and Xiaodong Shen
Available online 13 September 2023, https://doi.org/10.1007/s12613-023-2743-1
[Abstract](26) [PDF 2202KB](4)

Water-quenched copper-nickel metallurgical slag, enriched with olivine minerals, exhibits promising potential for the production of CO2 mineralization cementitious materials. In this work, we synthesized copper-nickel slag-based cementitious material (CNCM) by using different chemical activation methods to enhance its hydration reactivity and CO2 mineralization capacity. Different water curing ages and carbonation conditions are explored with the examination of the mechanical properties and microstructure development of carbonated CNCM blocks. Meanwhile, thermogravimetry-differential scanning calorimetry and X-ray diffraction methods are used to evaluate the CO2 adsorption amount and carbonation products of CNCM. Results show that the 3 d water-cured CNCM exhibited the highest CO2 sequestration amount of 8.51 wt.% at 80 ℃ and 72 h while achieving a compressive strength of 39.07 MPa among the studied samples. This means that one ton of this CNCM can sequester 85.1 kg of CO2 as well with high compressive strength. The addition of citric acid does not improve the strength development but is beneficial to increase the CO2 diffusion and adsorption amount at the same carbonation condition. This work provided a possible solution for This work could be guidance for synthesizing CO2 mineralization cementitious materials with large usage of metallurgical slags containing olivine minerals.

Research Article
Solid-state impedance spectroscopy studies of dielectric properties and relaxation processes in Na2OV2O5–Nb2O5–P2O5 glass system
Sara Marijan and Luka Pavić
Available online 13 September 2023, https://doi.org/10.1007/s12613-023-2744-0
[Abstract](38) [PDF 1563KB](4)

Solid-state impedance spectroscopy is used to investigate the influence of structural modifications resulting from the addition of Nb2O5 on the dielectric properties and relaxation processes in the quaternary mixed glass former (MGF) system 35Na2O–10V2O5-(55–x)P2O5-xNb2O5 (x = 0–40 mol%). The dielectric parameters, including the dielectric strength, and dielectric loss, are determined from the frequency and temperature-dependent complex permittivity data, revealing a significant dependence on the Nb2O5 content. The transition from a predominantly phosphate glass network (x < 10, Region I) to a mixed niobate-phosphate glass network (10 ≤ x ≤ 20, Region II) leads to an increase in the dielectric parameters, which correlates with the observed trend in DC conductivity. In the predominantly niobate network (x ≥ 25, Region III), the highly polarizable nature of Nb5+ ions leads to a further increase in the dielectric permittivity and dielectric strength. This is particularly evident in Nb-40 glass-ceramic, which contains Na13Nb35O94 crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz. The relaxation studies, analyzed through modulus formalism and complex impedance data, show that DC conductivity and relaxation processes are governed by the same mechanism, attributed to ionic conductivity. In contrast to glasses with a single peak in M''(ω) due to DC conductivity, Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times. The high-frequency peak indicates bulk ionic conductivity, while the additional low-frequency peak is associated with the grain boundary, confirmed by EEC modeling. The scaling characteristics of permittivity and conductivity spectra, along with the electrical modulus, validate time-temperature superposition and demonstrate a strong correlation with composition and modification of the glass structure upon Nb2O5 incorporation.

Invited Review
Microstructure and forming mechanism of metal by ultrasonic vibration plastic forming
Qinghe Cui, Xuefeng Liu, Wenjing Wang, Shaojie Tian, Vasili Rubanik, Vasili Rubanik Jr., and Dzmitry Bahrets
Available online 13 September 2023, https://doi.org/10.1007/s12613-023-2745-z
[Abstract](17) [PDF 1434KB](5)

Compared with the traditional plastic forming technology, ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece. It has a very broad application prospect in the industrial manufacturing field. In recent years, researchers have conducted extensive research in ultrasonic vibration plastic forming of metals. A deep foundation has been laid for the development of this field. This study classified metals according to their crystal structures. The effects of ultrasonic vibration on the microstructure during plastic forming of face centered cubic (FCC), body centered cubic (BCC) and hexagonal close packed (HCP) metals and the forming mechanism of ultrasonic vibration were reviewed. The main problems and future research direction of ultrasonic vibration plastic forming of metals were pointed out.

Research Article
Investigation of the flow characteristics and hot workability of a typical low-alloy high-strength steel during multi-pass deformation
Mingjie Zhao, Lihong Jiang, Changmin Li, Liang Huang, Chaoyuan Sun, Jianjun Li, and Zhenghua Guo
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2736-0
[Abstract](25) [PDF 1710KB](5)

Heavy components of low-alloy high-strength (LAHS) steels are generally formed by multi-pass forging. It is necessary to explore the flow characteristics and hot workability of LAHS steels during the multi-pass forging process, which is beneficial to the formulation of actual processing parameters. In the study, the multi-pass hot compression experiments of a typical LAHS steel are carried out at a wide range of deformation temperatures and strain rates. It is found that the work hardening rate of the experimental material depends on deformation parameters and deformation passes. It is ascribed to the impacts of static and dynamic softening behaviors. A new model is established to describe the flow characteristics at various deformation passes. Compared to the classical Arrhenius model and modified ZA model, the newly proposed model shows higher prediction accuracy with a confidence level of 0.98565. Furthermore, the connection between power dissipation efficiency (PDE) and deformation parameters is revealed by analyzing the microstructures. The PDE cannot be utilized to reflect the efficiency of energy dissipation for microstructure evolution during the entire deformation process, but only to assess the efficiency of energy dissipation for microstructure evolution in a specific deformation parameter state. As a result, an integrated processing map is proposed to better study the hot workability of the LAHS steel, which considers the effects of instability factor (IF), PDE, and distribution and size of grains. The optimized processing parameters for the multi-pass deformation process are the deformation parameters of 1223~1318 K and 0.01~0.08 s-1. Complete dynamic recrystallization occurs within the optimized processing parameters with an average grain size of 18.36~42.3 μm. It will guide the optimization of the forging process of heavy components.

Invited Review
Development and prospects of molten steel deoxidation in steelmaking process
Zhongliang Wang and Yanping Bao
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2740-4
[Abstract](35) [PDF 1554KB](7)

In the traditional long process of steelmaking, excess oxygen is blown into the converter, and then alloying elements are used for deoxidation. This inevitably results in a large amount of deoxidation products remaining in the steel liquid, affecting the cleanliness of the steel. With the increasing requirements for steel performance, it is necessary to not only reduce the oxygen content in the steel liquid, but also ensure its high cleanliness. After more than a hundred years of development, the total oxygen content in steel has been reduced from over 100×10-6 to around 10×10-6, and it can even be controlled below 5×10-6 in some steel grades. A relatively stable and mature deoxidation technology has been formed, but further reducing the oxygen content in steel is no longer significant for improving steel quality. Our research team has developed a deoxidation technology for bearing steel based on the optimization of the entire process. It is a combination of silicon-manganese pre-deoxidation, ladle furnace diffusion deoxidation, and vacuum final deoxidation. We have successfully conducted industrial experiments on the production technology of interstitial free steel with natural decarbonization pre-deoxidation. The former can control the oxygen content in bearing steel to between 4-8×10-6, change the type of inclusions, eliminate large particle Ds-type inclusions, improve the flowability of the steel liquid, and obtain a higher fatigue life. The latter not only reduces aluminum consumption and production costs but also significantly improves the quality of cast billets.

Research Article
Diffusion and reaction mechanism of limestone and quartz in fluxed iron ore pellet roasting process
Yufeng Guo, Jinlai Zhang, Shuai Wang, Jianjun Fan, Haokun Li, Feng Chen, Kuo Liu, and Lingzhi Yang
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2739-x
[Abstract](17) [PDF 3288KB](3)

To increase the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process. In this study, the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments. Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements' diffusion and phase transformation during the roasting process. The results indicated that limestone decomposed into calcium oxide, and magnetite was oxidized to hematite at the early stage of preheating. With the increase in roasting temperature, the diffusion rate of Fe and Ca was obviously accelerated, while the diffusion rate of Si was relatively slow. The order of magnitude of interdiffusion coefficient of Fe2O3-CaO diffusion couple was 10−10 m2·s−1 at a roasting temperature of 1473 K for 9 h. Ca2Fe2O5 was the initial product in the Fe2O3-CaO-SiO2 diffusion interface, and then Ca2Fe2O5 continued to react with Fe2O3 to form CaFe2O4. With the expansion of the diffusion region, the SFC liquid phase was produced due to the melting of SiO2 into CaFe2O4, which could strengthen the consolidation of fluxed pellets. Furthermore, andradite would be formed around a small part of quartz particles, which was also conducive to the consolidation of fluxed pellets. In addition, the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.

Research Article
Selective leaching of lithium from spent lithium-ion batteries using sulfuric acid and oxalic acid
Haijun Yu, Dongxing Wang, Shuai Rao, Lijuan Duan, Cairu Shao, Xiaohui Tu, Zhiyuan Ma, Hongyang Cao, and Zhiqiang Liu
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2741-3
[Abstract](48) [PDF 1216KB](6)

Traditional hydrometallurgical methods for recovering spent lithium-ion batteries involve acid leaching to simultaneously extract all valuable metals into the leachate. This is followed by a series of separation steps such as precipitation, extraction, and stripping to separate the individual valuable metals. These processes are time-consuming and result in high lithium loss rates due to its late recovery stage. In this study, we present a process for selectively leaching lithium through the synergistic effect of sulfuric and oxalic acids. Under optimal leaching conditions (leaching time of 1.5 h, leaching temperature of 70 °C, liquid-solid ratio of 4 mL/g, sulfuric acid: oxalic acid = 1.3:1.3), the lithium leaching efficiency reached 89.6%, with good selectivity. XRD and ICP-OES analyses showed that most of the Ni, Co, and Mn in the raw material remained as oxides and oxalates in the residue. This study offers a new approach to enriching the relevant theory for the selective preferential leaching process of lithium.

Research Article
A functionalized activated carbon adsorbent prepared from waste amidoxime resin modified with H3PO4 and ZnCl2 and its excellent adsorption of Cr (VI)
Chunlin He, Yun Liu, Mingwei Qi, Zunzhang Liu, Yuezhou Wei, Toyohisa Fujita, Guifang Wang, Shaojian Ma, and Wenchao Yang
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2737-z
[Abstract](48) [PDF 2025KB](3)

With the application of resins in various fields, a large number of waste resins that are difficult to treat have been produced. The wastewater containing chromium produced by industry has seriously polluted the soil and groundwater environment, thus endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z for adsorption Cr(VI), was prepared from waste amidoxime resin. The waste amidoxime resin was firstly modified with H3PO4 and ZnCl2, and subsequently was carbonized by slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo second order kinetic model and Langmuir isotherm, which verifies that the adsorption of Cr(VI) by PPR-Z is mainly chemical adsorption and belongs to single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(VI) can reach 255.86 mg/g. The adsorbent could effectively reduce Cr(VI) to Cr(III) and reduce the toxicity of Cr(VI) during adsorption. PPR-Z exhibited selectivity for Cr(VI) in electroplating wastewater. The main adsorption mechanisms includes chemical reduction of Cr(VI) into Cr(III), electrostatic interaction and coordination interaction. Preparation of PPR-Z not only solves the problem of waste resin treatment, but also effectively controls the pollution of chromium, and realizing the concept of "treating waste with waste".

Research Article
Recovery of Li, Ni, Co, and Mn from spent lithium-ion batteries assisted by organic acids: Process optimization and leaching mechanism
Liuyi Ren, Bo Liu, Shenxu Bao, Wei Ding, Yimin Zhang, Xiaochuan Hou, Chao Lin, and Bo Chen
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2735-1
[Abstract](31) [PDF 1469KB](8)

The proper recycling of spent lithium-ion batteries (LIBs) can promote the recovery and utilization of valuable resources, while also negative environmental effects resulting from the presence of toxic and hazardous substances. In this study, a new environmentally friendly hydro-metallurgical process was proposed for leaching lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) from spent LIBs using sulfuric acid with citric acid as a reductant. The effects of the concentration of sulfuric acid, the leaching temperature, the leaching time, the solid-liquid ratio, and the reducing agent dosages on the leaching behavior of the above elements were investigated. Key parameters were optimized using response surface methodology (RSM) to maximize the recovery of metals from spent LIBs. The maximum recovery efficiencies of Li, Ni, Co, and Mn can reach 99.08%, 97.99%, 98.76%, and 97.65% under the optimized conditions (the sulfuric acid concentration was 1.16 mol/L, the citric acid dosage was 15wt%, the solid-liquid ratio was 40 g/L, and the temperature was 83°C for 120 min), respectively.  It was found that in the collaborative leaching process of sulfuric acid and citric acid, the citric acid initially provided strong reducing  CO2·-  and the transition metal ions in the high state underwent a reduction reaction to produce transition metal ions in the low state. Additionally, citric acid can act as a proton donor and chelate with lower-priced transition metal ions, thus speeding up the dissolution process.

Invited Review
Extraction and recycling technologies of critical metal of cobalt from primary and secondary resources: A comprehensive review
Yukun Huang, Pengxu Chen, Xuanzhao Shu, Biao Fu, Weijun Peng, Jiang Liu, Yijun Cao, and Xiaofeng Zhu
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2734-2
[Abstract](50) [PDF 1746KB](10)

Cobalt has excellent electrochemical, magnetic, and heat properties. As a strategic resource, it has been applied in many high-tech products. However, the rapid growth of the battery industry in recent years has resulted in a significant depletion of cobalt resources, leading to a crisis of cobalt resources supply. The paper examines cobalt ore reserve and distribution, and summarizes recent development and consumption of cobalt resources. And the principles, advantages and disadvantages, and research status of various methods are discussed comprehensively. It can be concluded that the utilization of diverse sources (Cu-Co ores, Ni-Co ores, zinc plant residues, and waste cobalt products) for producing cobalt will be enhanced to meet developmental requirements. And in recovering technology, the pyro-hydrometallurgical process employs pyrometallurgy as the pre-treatment to modify the phase structure of cobalt minerals, enhancing its recovery in the hydrometallurgical stage and facilitating high-purity cobalt production. Consequently, it represents a highly promising technology for future cobalt recovery. Lastly, based on the above conclusions, the prospects for cobalt, in terms of cobalt ores processing and sustainable cobalt recycling for which further study should be conducted in the future.

Research Article
Potassium thiocyanate additive for PEDOT:PSS layer to fabricate efficient tin-based perovskite solar cells
Xu Zhao, Shoudeng Zhong, Shuqi Wang, Shaozhen Li, and Sujuan Wu
Available online 9 September 2023, https://doi.org/10.1007/s12613-023-2738-y
[Abstract](49) [PDF 850KB](8)

Although the commercialized poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) is usually used as hole transport layer (HTL) in tin-based perovskite solar cells (TPSCs), its acidity damage the stability of TPSCs and restrict its further development. The PEDOT:PSS solution can be diluted by water to decrease acidity and reduce the cost of device fabrication, but the electrical conductivity will decrease obviously in diluted PEDOT:PSS. Herein, potassium thiocyanate (KSCN) is selected to regulate the properties of PEDOT:PSS HTL from the diluted PEDOT:PSS aqueous solution by water with a volume ratio of 1:1 to prepare efficient TPSCs. The concentrations of KSCN additive have been optimized. The effects of KSCN addition on the structure and photoelectrical properties of PEDOT:PSS HTL and TPSCs have been systematically studied. At the optimal KSCN concentration, the TPSCs based on KSCN-doped PEDOT:PSS HTL (KSCN-PSCs) demonstrate a champion power conversion efficiency (PCE) of 8.39%, while the reference TPSCs only show a champioan PCE of 6.70%. A series of characterization demonstrate that the KSCN additive increases the electrical conductivity of HTL prepared by the diluted PEDOT:PSS solution, improves the microstructure of perovskite film and inhibit carrier recombination in TPSCs, leading to the reduced hysteresis effect and enhanced PCE in KSCN-PSCs. This work gives a low-cost and practical strategy to develop a high-quality PEDOT:PSS HTL from diluted PEDOT:PSS aqueous solution for efficient TPSCs.

Invited Review
A review on the multi-scaled structures and mechanical/thermal properties of tool steels fabricated by laser powder bed fusion additive manufacturing
Huajing Zong, Nan Kang, Zehao Qin, and Mohamed El Mansori
Available online 26 August 2023, https://doi.org/10.1007/s12613-023-2731-5
[Abstract](70) [PDF 2819KB](16)

The laser powder bed fusion (LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest, especially in the mold industry. The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds. Thus, LPBF-processed tool steels have been widely studied. The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels. This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena, the microstructural characteristics, and the mechanical/thermal properties, including tensile properties, wear resistance, and thermal properties. The microstructural characteristics are presented through a multiscale perspective, ranging from densification, meso-structure, microstructure, substructure in grains, to nanoprecipitates. Finally, a summary of tool steels and their challenges and outlooks are introduced.

Research Article
Effect of Ti and Ta content on oxidation resistance of Co-Ni-based superalloys
Yuheng Zhang, Zixin Li, Yunwei Gui, Huadong Fu, and Jianxin Xie
Available online 25 August 2023, https://doi.org/10.1007/s12613-023-2733-3
[Abstract](57) [PDF 2675KB](10)

Co-Ni-based superalloys possess the capability to function at elevated temperatures and exhibit superior hot corrosion and thermal fatigue resistance. Therefore, they are expected to serve as crucial high-temperature structural materials for aero-engine and gas turbine hot-end components. In our previous work, we elucidated the influence of Ti and Ta on the high-temperature mechanical properties of the alloys. However, the intricate interplay among the elements also significantly affects the oxidation resistance of the alloys. In this paper, Co-35Ni-10Al-2W-5Cr-2Mo-1Nb-xTi-(5-x)Ta alloys (x = 1, 2, 3, 4) with varying Ti and Ta contents were designed and synthesized, and their oxidation resistance was studied from 800°C to 1000°C. After oxidation at three test conditions, 800°C for 200 h, 900°C for 200 h and 1000°C for 50 h, the main structure of the oxide layer of the alloy is spinel, Cr2O3 and Al2O3 in order from outside to inside. The oxides formed by Ta, W, and Mo are produced below the Cr2O3 layer. The findings reveal that the interaction of Ti and Ta elements imparts the highest oxidation resistance to the 3Ti2Ta alloy. Conversely, an excessive amount of Ti or Ta has an adverse effect on the oxidation resistance of the alloy. This study firstly reports the volatilization of W and Mo oxides during the oxidation process of Co-Ni-based cast superalloy with a high Al content and explains the formation mechanism of holes in the oxide layer. These results provide a basis for understanding the effect of the interaction of alloying elements on the oxidation resistance of the alloy.

Research Article
Prediction of lime utilization ratio of dephosphorization in BOF steelmaking based on online sequential extreme learning machine with forgetting mechanism
Runhao Zhang, Jian Yang, Han Sun, and Wenkui Yang
Available online 25 August 2023, https://doi.org/10.1007/s12613-023-2732-4
[Abstract](41) [PDF 1773KB](6)

The machine learning models of multiple linear regression (MLR), support vector regression (SVR), extreme learning machine (ELM), the proposed ELM model of online sequential ELM (OS-ELM) and OS-ELM with forgetting mechanism (FOS-ELM) are applied in predicting the lime utilization ratio of dephosphorization in BOF steelmaking process. Among the three basic models of MLR, SVR and ELM, ELM performs the best. OS-ELM and FOS-ELM are applied for the sequential learning and model updating. The optimal number of samples in validity term of the FOS-ELM model is determined to be 1500 with the smallest population MARE value of 0.058226. According to the variable importance analysis, the lime weight, initial P content and hot metal weight are the three most important variables for the lime utilization ratio. The lime utilization ratio will increase with the decrease of lime weight and the increases of initial P content and hot metal weight. A prediction system based on FOS-ELM is applied in the actual industrial production for one month. The hit ratios of the predicted lime utilization ratio in the error ranges of ±1%, ±3% and ±5% are 61.16%, 90.63% and 94.11%, respectively. The values of R2, MARE and RMSE are 0.8670, 0.06823 and 1.4265, respectively. The performance of the system is pretty good for the application in the actual industrial production.

Research Article
Enhanced recovery of high-purity Fe powder from iron-rich electrolytic manganese residue by slurry electrolysis
Wenxing Cao, Jiancheng Shu, Jiaming Chen , Zihan Li , Songshan Zhou, Shushu Liao , Mengjun Chen, and Yong Yang
Available online 18 August 2023, https://doi.org/10.1007/s12613-023-2729-z
[Abstract](168) [PDF 965KB](16)

Iron-rich electrolytic manganese residue (IREMR) is the industrial waste residue produced during the processing of electrolytic metal manganese, which contains amounts of Fe, Mn resources and other heavy metals. In this study, to recover high-purity Fe powder from IREMR, slurry electrolysis technique was used. The effects of the IREMR and H2SO4 mass ratio, current density, reaction temperature and electrolytic time on the leaching efficiency and current efficiency of Fe were studied. The results indicated that high-purity Fe powder can be recovered from the cathode plate and that the slurry electrolyte can be recycled. The leaching efficiency, current efficiency and the purity of Fe were 92.43%, 80.65% and 98.72%, respectively, when the mass ratio of H2SO4 and IREMR was 1:2.5, the reaction temperature was 60℃, the electric current density was 30 mA/cm2, and the reaction time was 8 h. In addition, the VSM analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m, which reached the electrical pure iron powder coercivity advanced magnetic grade (DT4A coercivity standard). The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.

Research Article
Preparation of sodium molybdate from molybdenum concentrate by microwave roasting and alkali leaching
Fengjuan Zhang, Chenhui Liu, Kannan C.Srinivasa, Yingwei Li, and Fuchang Xu
Available online 18 August 2023, https://doi.org/10.1007/s12613-023-2727-1
[Abstract](73) [PDF 2577KB](13)

A new process for the efficient recovery of molybdenum from molybdenum concentrate by microwave roasting and sodium hydroxide leaching was proposed, as an environmentally benign and economical alternative. Thermodynamic analysis indicated the feasibility of oxidative roasting of molybdenum concentrates. The effects of roasting temperature, holding time and power to mass ratio on the oxidation and leaching process on the formation of sodium molybdate (Na2MoO4-2H2O) were investigated. The optimal process conditions for oxidation roasting were found to be a roasting temperature of 700°C, a holding time of 110 min and a power to mass ratio of 110 W/g, while for leaching the optimal conditions correspond to sodium hydroxide concentration of 2.5 mol/L, a liquid to solid ratio of 2:1, a leaching temperature of 60°C and the leaching solution was terminated at pH 8. The optimum conditions result in the leaching rate of 96.24% for sodium molybdate with 94.08% content. A variety advanced characterization techniques such as XRF, XRD, SEM-EDS and FTIR were utilized to elucidate the conversion process.v

Research Article
Effect mechanism of aluminum occurrence and content on the induration characteristics of iron ore pellets
Hongyu Tian, Deqing Zhu, Jian Pan, Congcong Yang, Weiqun Huang, and Mansheng Chu
Available online 18 August 2023, https://doi.org/10.1007/s12613-023-2725-3
[Abstract](57) [PDF 1394KB](9)

With a growing depletion of high-grade iron ores, the increased aluminum content in the iron ore concentrates is unavoidable, which is detrimental to the pelletizing process. Therefore, it is essential to discover the effect mechanism of aluminum on pellet quality. In this paper, the effect of aluminum occurrence and content on the induration of both hematite and magnetite pellets was investigated by adding corresponding Al-containing additives including alumina, alumogoethite, gibbsite and kaolinite. The related mechanism was also revealed through not only systematic process mineralogy analyses combined with the thermodynamic properties of different aluminum occurrence, but also the quantitative characterization of consolidation behaviors. The results show that the alumina from different aluminum occurrence had an adverse effect on the induration characteristics of pellets, especially when the aluminum content was more than 2.0wt%. The thermal decomposition of gibbsite and kaolinite will tend to generate internal stress and fine cracks, which go against the respective formation of microcrystalline bonding and recrystallization between the Fe2O3 particles. The adverse effect on the induration characteristics of fired pellets with different aluminum occurrence can be relieved to varying degrees through the formation of slag bonds of CaO-Fe2O3-Al2O3-SiO2 polybasic eutectoid between the hematite particles. The kaolinite is more beneficial to the induration process than other three aluminum occurrence because of formation of more liquid phase which improves the consolidation of pellets. The research results can help to further understand the effect of aluminum occurrence and content in iron ore concentrates on downstream processing, and then provide a good guidance for the utilization of high-alumina iron ore concentrates in pelletizing.

Research Article
Cross-upgrading of biomass hydrothermal carbonization and pyrolysis for high quality blast furnace injection fuel production: Physicochemical characteristics and gasification kinetics analysis
Han Dang, Runsheng Xu, Jianliang Zhang, Mingyong Wang, and Jinhua Li
Available online 18 August 2023, https://doi.org/10.1007/s12613-023-2728-0
[Abstract](61) [PDF 1601KB](5)

The paper proposes a biomass cross-upgrading process that combines hydrothermal carbonization and pyrolysis to produce high-quality blast furnace injection fuel. The results demonstrate significant reductions in the volatile content of biochar, from 45.35% to 16.19%, as well as decreases in alkali metal content, ash content, and specific surface area. The optimal route for biochar production is hydrothermal carbonization-pyrolysis, resulting in biochar (P-HC) with a higher calorific value, C=C structure, and increased graphitization degree. The apparent activation energy (E) of the sample ranges from 199.1 kJ/mol to 324.8 kJ/mol, with P-HC having an E of 277.8 kJ/mol, lower than that of raw biomass, primary biochar, and anthracite. This makes P-HC more suitable for blast furnace injection fuel. Additionally, the paper proposes a path for P-HC injection in blast furnaces and calculates potential environmental benefits. P-HC offers the highest potential for carbon emission reduction, capable of reducing emissions by 96.04 kg/tHM when replacing 40% coal injection.

Research Article
Effect of TiO2 addition on the sticking of pellets based on hydrogen metallurgy shaft furnace: Behavior analysis and mechanism evolution
Jinge Feng, Jue Tang, Zichuan Zhao, Mansheng Chu, Aijun Zheng, Xiaobing Li, and Xiaoai Wang
Available online 18 August 2023, https://doi.org/10.1007/s12613-023-2730-6
[Abstract](59) [PDF 2688KB](7)

Direct reduction process based on the hydrogen metallurgy gas-based shaft furnace is a promising technology for efficiently and low-carbon smelt vanadium-titanium magnetite (VTM). However, in the direct reduction process, sticking of pellets occurs due to the aggregation of metallic iron between the contact surfaces of adjacent pellets, which will have a serious negative effect on the continuous operation. This paper presents a detailed experimental study of the effect of TiO2 on the sticking behavior of pellets during direct reduction process under different reduction conditions. The results showed that sticking index (SI) decreased linearly with increasing TiO2 addition, which stemmed from the increase of unreduced FeTiO3 during reduction, leading to decrease of the number and strength of metallic iron interconnections at the sticking interface. When the TiO2 addition was raised from 0% to 15% at 1100°C, SI increased from 0.71% to 59.91%. The connection of slag phase could be attributed to the sticking at low reduction temperature corresponding to low sticking strength. Moreover, interconnection of metallic iron became the dominant factor as reduction temperature increased, and SI increased sharply. Additionally, TiO2 had a great effect on SI at high reduction temperature compared to low reduction temperature.

Research Article
MOF-derived porous graphitic carbon with optimized plateau capacity and rate capability for high performance lithium ion capacitors
Ge Chu, Chaohui Wang, Zhewei Yang, Lin Qin, and Xin Fan
Available online 18 August 2023, https://doi.org/10.1007/s12613-023-2726-2
[Abstract](35) [PDF 922KB](4)

The development of anode materials with high rate capability and long charge-discharge plateau is the key to improve performance of lithium-ion capacitors (LICs). Herein, the porous graphitic carbon (PGC-1300) derived from a new triplyinterpenetrated cobalt metal-organic framework (Co-MOF) is prepared through the facile and robust carbonization at 1300 oC and washing by HCl solution. The as-prepared PGC-1300 features an optimized graphitization degree and porous framework, which not only contributes to high plateau capacity (105 mAh g-1 below 0.2 V at 0.05 A g-1), but also supplies more convenient pathways for ions and increases the rate capability (128.5 mAh g-1 at 3.2 A g-1). According to the kinetics analyses, it can be found that diffusion regulated surface induced capacitive process and Li-ions intercalation process are coexisted for lithium ion storage. Additionally, LIC PGC-1300//AC constructed with pre-lithiated PGC-1300 anode and activated carbon (AC) cathode exhibits an increased energy density of 102.8 Wh kg-1, a power density of 6017.1 W kg-1, together with the excellent cyclic stability (91.6% retention after 10000 cycles at 1 A g-1).

Invited Review
Formation and control on the surface defect of hypo-peritectic steel in continuous casting: A review
Quanhui Li, Peng Lan, Haijie Wang, Hongzhou Ai, Deli Chen, and Haida Wang
Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2716-4
[Abstract](94) [PDF 1468KB](18)

Hypo-peritectic steel is widely used in many industrial fields attributed to its excellent combination of high strength, high toughness, high processability, high weldability and low material cost. However, surface defects are quite liable to occur during continuous casting, including depression, longitudinal crack, deep oscillation mark, and severe level fluctuation with slag entrapment. It is still a great challenge to produce hypo-peritectic steel in high efficiency mode by continuous casting due to the limited understanding on the mechanism of peritectic solidification. This work reviews the definition and classification of hypo-peritectic steel, and introduces the formation tendency of common surface defects related to peritectic solidification. The new achievements on the mechanism of peritectic reaction and transformation have been listed. At last, the countermeasures to avoid the surface defects of hypo- peritectic steel has been summarized. It is helpful for the researcher to get some enlightening points in continuous casting of hypo-peritectic steel and develop new technique to overcome the present problems.

Research Article
Dual ion carrier storage through the addition of Mg2+ for high-energy and long-life zinc-ion hybrid capacitor
Junjie Zhang and Xiang Wu
Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2724-4
[Abstract](46) [PDF 1293KB](7)

Cation additive can efficiently enhance the total electrochemical capabilities of zinc ion hybrid capacitors (ZHCs). However, their energy storing mechanisms are still under debated in zinc-based systems. Herein, we assemble several Zn // AC devices with different concentration electrolytes and investigate their electrochemical reaction dynamic behaviors. The zinc ion capacitor with Mg2+ mixed solution provides 82 mAh g-1 capacity at 1A g-1 and maintains 91% of original capacitance after 10,000 cycling. It is superior to the other assembled zinc ion devices in single component electrolyte. It demonstrates that the double ion storage mechanism enables superior rate performance and long cycle lifetime in ZHCs.

Research Article
Cleaner production of Fe-based amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore and apatite
Hua Zhang, Tuoxiao Wang, Guoyang Zhang, Wenjie Wu, Long Zhao, Tao Liu, Shuai Mo, and Hongwei Ni
Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2722-6
[Abstract](141) [PDF 907KB](21)

The separated preparation of pre-alloys and amorphous alloys leads to severe solidification-remelting and beneficial elements removal-readdition contradictions, which greatly increases the energy consumption and emissions. In this study, a novel strategy for the direct production of FePC amorphous soft magnetic alloys via smelting reduction of high-phosphorus iron ore (HPIO) and apatite was proposed. The thermodynamic conditions and equilibriums of the carbothermal reduction reactions in HPIO were first calculated and the elements content in reduced alloys were theoretically determined. Experimentally, the phase and structure evolutions as well as the elements migration and enrichment behaviors during the smelting reduction of HPIO and Ca3(PO4)2 were then verified. The addition of Ca3(PO4)2 in HPIO contributes to the enrichment of P element in reduced alloys and the successive appearance of Fe3P, Fe2P phases. The content of P, C elements in the range of 1.52-14.63wt% and 0.62-2.47wt% can be well tailored by adding 0-50 g Ca3(PO4)2 and controlling the C/O ratio of 0.8-1.1, which is quite consistent with the calculated results. These resultant FePC alloys were then successfully prepared into amorphous ribbons and rods. Compared with the conventional production process, the energy consumption of our proposed strategy was estimated to be 680 kgce/t, which can be reduced by 30%. These results are quite vital for the comprehensive utilization of mineral resources and pave the way for the cleaner production of Fe-based amorphous soft magnetic alloys.

Research Article
Alkyl dimethyl betaine activates the low-temperature collection capacity of sodium oleate for scheelite
Xu Wang, Zhengquan Zhang, Yanfang Cui, Wei Li, Congren Yang, Hao Song, Wenqing Qin, and Fen Jiao
Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2718-2
[Abstract](48) [PDF 960KB](7)

The activation of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOL) at low temperatures was evaluated using flotation tests at different scales. The synergistic mechanism of ADB and NaOL under low temperatures was also explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test and flotation reagent size measurement. Based on the results of flotation tests, the collector mixed with octadecyl dimethyl betaine (ODB) and NaOL in a mass ratio of 4:96 revealed the most outstanding collection capacity. Under a low temperature of 8 °C–12 ℃, the combined collector could increase the scheelite recovery by 3.48% in the Luanchuan area, which has the largest scheelite concentrate output in China. The mechanism research results confirmed that ODB optimised the collection capability of NaOL by improving the dispersion and foaming performance. Betaine can be introduced as an additive of NaOL to improve the recovery of scheelite at low temperatures.

Research Article
Constructing Al@C-Sn pellet anode without passivation layer for Li-ion battery
Kangzhe Cao, Sitian Wang, Yanan He, Jiahui Ma, Ziwei Yue, and Huiqiao Liu
Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2720-8
[Abstract](55) [PDF 1151KB](8)

Aluminum (Al) is considered as a promising lithium-ion battery (LIB) anode material owing to its high theoretical capacity and appropriate lithation-delithation potential. Unluckily, its inevitable volume expansion causes the electrode structure instability, leading to poor cyclic stability. What’s worse, the natural Al2O3 layer on commercial Al pellets is always existed as a robust insulating barrier for electrons, which brings the voltage dip and results in low reversible capacity. Herein, we synthesized core-shell Al@C-Sn pellets for LIBs by a plus-minus strategy. In this proposal, the natural Al2O3 passivation layer is eliminated when annealing the pre-introduced SnCl2, meanwhile, polydopamine-derived carbon is introduced as dual functional shell to alleviate the volume swellings and liberate the fresh Al core from re-oxidization. Benefiting from the addition of C-Sn shell and the elimination of the Al2O3 passivation layer, the as-prepared Al@C-Sn pellet electrode exhibits little voltage dip and delivers a reversible capacity of 1018.7 mAh g−1 at 0.1 A g-1 and 295.0 mAh g-1 at 2.0 A g-1 (after 1000 cycles). Moreover, its diffusion-controlled capacity is muchly improved compared to those of its counterparts, confirming the well-designed nanostructure contributes to the rapid Li-ion diffusion and further enhances the lithium storage activity.

Research Article
Establishment of NaLuF4:15%Tb-based low dose X-PDT agent and its application on efficient antitumor therapy
Yi Tian, Zhiguang Fu, Xiaosheng Zhu, Chunjing Zhan, Jinwei Hu, Li Fan, Chaojun Song, Qian Yang, Mei Shi, and Yu Wang
Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2717-3
[Abstract](48) [PDF 1319KB](10)

X-ray excited photodynamic therapy (X-PDT), is the bravo answer of photodynamic therapy (PDT) for deep-seated tumors, as it employs X-ray as the irradiation source to overcome the limitation of light penetration depth. However, high X-ray irradiation dose caused organ lesions and side effects became the major barrier to X-PDT application. To address this issue, firstly, we employed a classical co-precipitation reaction to synthesize NaLuF4: 15%Tb3+(NLF) with an average particle size of 23.48 ± 0.91 nm, which was then coupled with the photosensitizer merocyanine 540 (MC540) to form the X-PDT system NLF-MC540 with high production of singlet oxygen. Secondly, the system could induce antitumor efficacy to about 24% in relative low dose X-ray irradiation range (0.1-0.3 Gy). In vivo, when NLF-MC540 irradiated by 0.1 Gy X-ray, the tumor inhibition percentage reached 89.5 ± 5.7%. Finally, we try to find the therapeutic mechanism which may exist in low dose X-PDT. A significant increase of neutrophils in serum was found on the third day after X-PDT. By immunohistochemical staining of tumor sections, we studied the Ly6G+, CD8+, and CD11c+ cells infiltrated in the tumor microenvironment. Utilizing the bilateral tumor model, we found the NLF-MC540 with 0.1 Gy X-ray irradiation could inhibit both the primary tumor and the distant tumor growth. Detected by Elisa assay, two cytokines IFN-γ and TNF-α in serum were upregulated 7 times and 6 times than negative control. Detected by Elispot assay, the number of immune cells attributable to the IFN-γ and TNF-α levels in the group of low dose X-PDT were 14 times and 6 times greater than that in the negative control group. Thus, we could conclude that our low dose X-PDT system could successfully upregulate the levels of immune cells, stimulate the secretion of cytokines (especially IFN-γ and TNF-α), activate antitumor immunity, finally inhibit colon tumor growth.

Research Article
High chromium vanadium-titanium magnetite all pellets integrated burden optimization and softening-melting behavior based on flux pellets
Bojian Chen, Tao Jiang, Jing Wen, Guangdong Yang, Tangxia Yu, Fengxiang Zhu, and Peng Hu
Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2719-1
[Abstract](52) [PDF 1935KB](10)

High chromium vanadium-titanium magnetite (HVTM) is a crucial polymetallic-associated resource to be developed. All pellets operation is one of the trends of blast furnaces to reduce CO2 emission in the future. By referencing the production data of vanadium-titanium magnetite blast furnaces, this study explored the softening-melting (S-M) behavior of high chromium vanadium-titanium magnetite and obtained the optimal integrated burden based on flux pellets. The results showed that the burden composition of 70% flux pellets and 30% acid pellets obtained best S-M properties. In comparison with single burden, the S-M characteristic temperature of this burden composition was higher, the cohesive zone shifted downward and narrowed from 307 °C to 282 °C, the maximum pressure drop (ΔPmax) decreased from 26.76 kPa to 19.01 kPa, and the Permeability index (S) dropped from 4643.5 kPa·°C to 2446.8 kPa·°C. The S-M properties of integrated burden improved apparently. During the softening process, the acid pellets played a role in withstanding the load, and the flux pellets in the integrated burden during the melting process exhibited a higher slag melting point, which increased the melting temperature. The homogeneity of the slag and the TiC produced by the over-reduction led to the deterioration of the gas permeability of single burden. The segregation of acid and flux pellets in the HVTM proportion and basicity was the main reason for the better S-M properties of the integrated burden.

Research Article
Structural and magnetic properties of micro-polycrystalline cobalt thin film fabricated by DC magnetron sputtering
Kerui Song, Zhou Li, Mei Fang, Zhu Xiao, and Qian Lei
Available online 27 July 2023, https://doi.org/10.1007/s12613-023-2715-5
[Abstract](58) [PDF 1090KB](7)

The pure cobalt (Co) thin films were fabricated by direct current magnetron sputtering, and the effects of sputtering power and pressure on the microstructure and electromagnetic properties were investigated. The results reveal that as the sputtering power increases from 15 W to 60 W, the Co thin film transitions from an amorphous to a polycrystalline state, which is accompanied by an increase in intercrystal pore width. Concurrently, resistivity decreases by 65%, coercivity escalates from 162 Oe to 292 Oe, and the in-plane magnetic anisotropy disappears as the film transitions to a polycrystalline state. As the sputtering pressure decreases from 1.6 Pa to 0.2 Pa, there is a notable increase in grain size, along with a dramatic drop in resistivity (from 377 μΩcm to 37 μΩcm) and a significant rise in coercivity (from 67 Oe to 280 Oe), which can be ascribed to the increasing defect width. Correspondingly, a quantitative model for the coercivity of Co thin films has been formulated. In the polycrystalline films sputtered under pressures of 0.2 Pa and 0.4 Pa, significant in-plane magnetic anisotropy is observed, which is primarily attributable to increased microstress.

Research Article
Effects of hot deformation behavior and processing map on 316LN-Mn austenitic stainless steel dynamic recrystallization
Shaolong Sheng, Yanxin Qiao, Ruzong Zhai, Mingyue Sun, and Bin Xu
Available online 27 July 2023, https://doi.org/10.1007/s12613-023-2714-6
[Abstract](54) [PDF 1980KB](7)

The hot deformation behaviors of 316LN-Mn austenitic stainless steel (ASS) are investigated under uniaxial isothermal compression tests at different temperatures and strain rates. Additionally, the microstructural evolutions are investigated using electron backscatter diffraction (EBSD). The flow

stress decreased with increasing temperature and decreasing strain rate. A constitutive equation is established to characterize the relationship among the deformation parameters, and the deformation activation energy is calculated to be 497.92 kJ/mol. The processing maps are constructed to describe the

appropriate processing window, and the optimum processing parameters are determined at the temperature of 1107-1160 °C and the strain rate of 0.005-0.026 s -1 . The experimental results show that the main nucleation mechanism is discontinuous dynamic recrystallization (DDRX), and continuous dynamic recrystallization (CDRX) plays the secondary place. The formation of twin boundaries also facilitates the nucleation of dynamic recrystallization (DRX).

Research Article
Effects of iron oxide on crystallization behavior and spatial distribution of spinel in stainless steel slag
Zihang Yan, Qing Zhao, Chengzhi Han, Xiaohui Mei, Chengjun Liu, and Maofa Jiang
Available online 27 July 2023, https://doi.org/10.1007/s12613-023-2713-7
[Abstract](39) [PDF 2214KB](3)

Chromium plays a vital role in stainless steel due to its ability to improve the corrosion resistance of the latter. However, the release of chromium from stainless steel slag (SSS) during SSS stockpiling causes detrimental environmental issues. To prevent chromium pollution, the effects of iron oxide on crystallization behavior and spatial distribution of spinel were investigated in this work. The results revealed that FeO was more conducive to the growth of spinels compared with Fe2O3 and Fe3O4. Spinels were found to be mainly distributed at the top and bottom of slag. The amount of spinel phase at the bottom decreased with the increasing FeO content, while that at the top increased. The average particle size of spinel in the slag with 18wt% FeO content was 12.8 µm. Meanwhile, no notable structural changes were observed with a further increase in FeO concentration. In other words, the spatial distribution of spinel changed when the content of iron oxide varied in the range of 8 to 18wt%. Finally, less spinel was found at the bottom of slag with a FeO concentration of 23wt%.

Invited Review
Metal to insulator transitions in 3d-band correlated oxides containing Fe composition
Yiping Yu, Yuchen Cui, Jiangang He, Wei Mao, and Jikun Chen
Available online 15 July 2023, https://doi.org/10.1007/s12613-023-2712-8
[Abstract](94) [PDF 593KB](15)

The metal to insulator transitions (MIT) as achieved in 3d-band correlated transitional metal oxides triggers abrupt variations in the electrical, optical and/or magnetic properties, beyond conventional semiconductors. Among such material families, the ion (Fe: 3d64s2) containing oxides are interesting owing to their widely tunable MIT properties associated with various valance states of Fe, while their potential electronic applications are also promising noticing the large abundance of Fe on earth. Representative MIT properties triggered by critical temperature (TMIT) were reported for ReFe2O4 (Fe2.5+), ReBaFe2O5 (Fe2.5+), Fe3O4 (Fe2.67+), Re1/3Sr2/3FeO3 (Fe3.67+), ReCu3Fe4O12 (Fe3.75+) and Ca1-xSrxFeO3 (Fe4+). It is also interesting to note the common feature in MITs of these Fe containing oxides that are usually accompanied by the charge ordering transitions or disproportionation associated with the valance states of Fe. Herein, we review the material family of the Fe-containing MIT oxides, their MIT functionalities and the respective mechanisms. From the perspective of potential correlated electronic applications, the tunability in the critical temperatures associated with MIT (TMIT) and its resultant resistive change are summarized for the Fe-containing oxides and further compared to other materials exhibiting the MIT functionality. In particular, we highlight the abrupt MIT and wide tunability in TMIT for the Fe-containing quadruple perovskites, such as ReCu3Fe4O12, while their more effective material synthesis is yet required to be further explored to cater for potential applications.

Research Article
Spark plasma sintering of tungsten-based WTaVCr refractory high entropy alloys for nuclear fusion applications
Yongchul Yoo, Xiang Zhang, Fei Wang, Xin Chen, Xingzhong Li, Michael Nastasi, and Bai Cui
Available online 15 July 2023, https://doi.org/10.1007/s12613-023-2711-9
[Abstract](145) [PDF 1392KB](23)

W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6 and TaVO4 through a combined analysis of X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED).  The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phase based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2 μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro- and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000 ºC.  

Research Article
Numerical investigation of sinusoidal pulsating gas intake to intensify gas-slag momentum transfer in the top-blown smelting furnace
Zhanghao Wan, Shiliang Yang, Desong Kong, Dongbo Li, Jianhang Hu, and Hua Wang
Available online 13 July 2023, https://doi.org/10.1007/s12613-023-2705-7
[Abstract](59) [PDF 2313KB](9)

The variation characteristics of bubble morphology and the thermal-physical properties of bubble boundary in the top-blown smelting furnace are explored by means of the computational fluid dynamics method. The essential aspects of the fluid phase (e.g. splashing volume, dead zone of copper slag, and gas penetration depth) are explored, together with the effect of sinusoidal pulsating gas intake on the momentum transfer performance between phases. The results illustrate that two relatively larger vortices and two smaller vortices appear in the bubble waist and below the lance, respectively. The larger ones expand and the smaller ones shrink, leading to the contraction of the bubble waist. Compared to the constant velocity condition, the splashing volume and dead zone volume of the slag under the Vg=58+10sin(2πt) condition are reduced by 24.9% and 23.5%, respectively. Gas penetration depth and slag velocity of the latter are 1.03 and 1.31 times higher than those of the former, respectively.

Research Article
Hot deformation behavior of novel high-strength Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy
Hao Chen, Yanmei Yang, Conglin Hu, Gang Zhou, Hui Shi, Genzhi Jiang, Yuanding Huang, Norbert Hort, Weidong Xie, and Guobing Wei
Available online 13 July 2023, https://doi.org/10.1007/s12613-023-2706-6
[Abstract](133) [PDF 2820KB](12)

The hot compression behavior of the as-extruded Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy was studied on a Gleeble-3500 thermal simulation machine. The experiments were conducted at temperatures ranging from 523 K to 673 K and strain rates ranging from 0.001 s–1 to 1 s–1, respectively. The results exhibited that an increase in strain rate or a decrease in deformation temperature will lead to an increase in true stress. The constitutive equation and processing maps have been obtained and analyzed. The influence of deformation temperatures and strain rates on microstructural evolution and texture were studied with the assistance of electron backscatter diffraction (EBSD). The as-extruded alloy showed a bimodal structure, consisting of deformed coarse grains and fine equiaxed recrystallization structure (about 1.57 μm). The EBSD results of deformed alloys revealed that both the recrystallization degree and the average grain size increase as the deformation temperature increases. In contrast, the dislocation density and the texture intensity decrease. The compressive texture becomes weak with the increase of deformation temperature at the strain rate of 0.01 s-1. Most grains with {0001} planes tilt away from the compression direction gradually. In addition, when the strain rate decreases both the recrystallization degree and the average grain size increase. Meanwhile, the dislocation density decreases. The texture seems not to be sensitive to the strain rate.

Research Article
Facile synthesis of composite poly-ferric-magnesium-silicate-sulfate coagulant with enhanced performance in water and wastewater
Xiangtao Huo, Rongxia Chai, Lizheng Gou, Mei Zhang, and Min Guo
Available online 13 July 2023, https://doi.org/10.1007/s12613-023-2704-8
[Abstract](42) [PDF 1386KB](2)

Coagulation process is a core technology that has been widely applied in water and wastewater treatment. In this paper, novel composite coagulants poly-ferric-magnesium-silicate-sulfate (PFMS) were synthesized by using Na2SiO3·9H2O, Fe2(SO4)3 and MgSO4 as the raw materials. The effects of aging time, Fe:Si:Mg and OH:M molar ratios (M represents the metal ions) on the coagulation performance of the as-prepared PFMS were systematically investigated to obtain optimum coagulants. The results showed that PFMS coagulant exhibited good coagulation properties in treating simulated humic acid-kaolin surface water and reactive dye wastewater. When the molar ratios were controlled at Fe:Si:Mg=2:2:1 and OH:M=0.32, the obtained PFMS presented excellent stability along with high coagulation efficiency (the removal efficiency of UV254 was 99.81%, and the residual turbidity of the surface water was 0.56 NTU at a dosage of 30 mg/L). After standing the coagulant for 120 days in the laboratory, the removal efficiency of UV254 and residual turbidity of the surface water still maintained 88.12% and 0.68 NTU, respectively, meeting the surface water treatment requirements. In addition, the coagulation performance in treating reactive dye wastewater was greatly improved by combining the advantages of magnesium and iron salts. Compared with poly-ferric-silicate-sulfate (PFS) and poly-magnesium-silicate-sulfate (PMS), PFMS coagulant played a good decolorization role within the pH range of 7-13.

Invited Review
Advances in depressants for flotation separation of Cu–Fe sulfide minerals at low alkalinity: A critical review
Qicheng Feng, Wenhang Yang, Maohan Chang, Shuming Wen, Dianwen Liu, and Guang Han
Available online 13 July 2023, https://doi.org/10.1007/s12613-023-2709-3
[Abstract](81) [PDF 1153KB](7)

The flotation separation of Cu–Fe sulfide minerals at low alkalinity can be achieved using selective depressants. In the flotation system of Cu–Fe sulfide minerals, depressants usually preferentially interact with the pyrite surface to render the mineral surface hydrophilic and hinder collector adsorption. This study summarizes advances in depressants for the flotation separation of Cu–Fe sulfide minerals at low alkalinity. These include inorganic depressants (oxidants and sulfur-oxygen compounds), natural polysaccharides (starch, dextrin, konjac glucomannan, and galactomannan), modified polymers (carboxymethyl cellulose, polyacrylamide, lignosulfonate, and tricarboxylate sodium starch), organic acids (polyglutamic acid, sodium humate, tannic acid, pyrogallic acid, salicylic acid, and lactic acid), sodium dimethyl dithiocarbamate, and diethylenetriamine. The potential application of specific inorganic and organic depressants in the flotation separation of Cu–Fe sulfide minerals with low alkalinity is reviewed. This paper comprehensively discusses advances in the use of organic depressants in the flotation separation of Cu–Fe sulfide minerals and summarizes the depression performance and mechanism of different types of organic depressants on mineral surfaces. Finally, perspectives on depressants in the flotation separation of Cu–Fe sulfide minerals at low alkalinity are proposed.

Research Article
Preparation of CIP@TiO2 composite with broadband electromagnetic wave absorption properties
Qiang Su, Hanqun Wang, Yunfei He, Dongdong Liu, Xiaoxiao Huang, and Bo Zhong
Available online 13 July 2023, https://doi.org/10.1007/s12613-023-2707-5
[Abstract](55) [PDF 806KB](5)

It is meaningful to improve the impedance matching of the material while maintaining its excellent wave absorption properties. In this paper, according to the hydrolysis characteristics of isopropyl titanate (TTIP), a simple preparation process of carbonyl iron powder (CIP) coated with TiO2 was designed. Due to the coated TiO2, the impedance matching of the CIP@TiO2 composite was well adjusted by decreasing the dielectric constant. Moreover, the interfacial polarization of CIP@TiO2 has also been enhanced. Ultimately, the electromagnetic wave (EMW) absorption property of CIP@TiO2 composite was significantly improved, the minimum reflection loss (RLmin) reach -46.07 dB, and the effective absorption bandwidth (EAB) can reach 8 GHz when the thickness is only 1.5 mm. Moreover, compared the CIP, the oxidation resistance of CIP@TiO2 was significantly improved. The results shown that the oxidation starting temperature of CIP@TiO2 is 400oC, whereas uncoated CIP has an oxidation starting temperature of about 250oC. Moreover, the largest oxidation rate temperature of CIP@TiO2 was increased to about 550oC. This work opens up a novel strategy for producing high-performance EMW absorbers with the help of structure design.

Research Article
Role of tannin pretreatment in flotation separation of magnesite and dolomite
Xiufeng Gong, Jin Yao, Jun Guo, Bin Yang, Haoran Sun, Wanzhong Yin, Yulian Wang, and Yafeng Fu
Available online 13 July 2023, https://doi.org/10.1007/s12613-023-2708-4
[Abstract](68) [PDF 382KB](3)

Flotation separation of magnesite and its calcium-containing carbonate minerals is a difficult problem. Recently, new regulators have been proposed for magnesite flotation decalcification, although traditional adjusters such as tannin, water glass, sodium carbonate and sodium hexametaphosphate are more widely used in industry. However, they are rarely used as the main regulators in research because they perform poorly in magnesite and dolomite single-mineral flotation tests. Inspired by the limonite pre-desilting method and the addition of a modifier to magnesite slurry mixing, we used a tannin pretreatment method for separating magnesite and dolomite. Microflotation experiments confirmed that the tannin pretreatment method selectively and largely reduces the flotation recovery rate of dolomite without affecting the flotation recovery rate of magnesite. Moreover, the contact angles of the tannin-pretreated magnesite and dolomite increased and decreased, respectively, in the presence of NaOL. Zeta potential and Fourier transform infrared analyses showed that the tannin pretreatment method efficiently hinders NaOL adsorption on the dolomite surface but does not affect NaOL adsorption on the magnesite surface. X-ray photoelectron spectroscopy and density functional theory calculations confirmed that tannin interacts more strongly with dolomite than with magnesite.

Research Article
Metal-organic decomposition growth of thin film metastable perovskite nickelates with kinetically improved quantum transitions
Haiyan Li, Yuzhao Wang, Fanqi Meng, Wei Mao, Xingzhong Cao, Yi Bian, Hao Zhang, Yong Jiang, Nuofu Chen, and Jikun Chen
Available online 7 July 2023, https://doi.org/10.1007/s12613-023-2703-9
[Abstract](110) [PDF 1643KB](30)

The multiple quantum transitions within d-band correlation oxides such as rare-earth nickelates (ReNiO3) triggered by critical temperatures and/or hydrogenation opened up a new paradigm for correlated electronics applications, e.g., ocean electric field sensor, bio-sensor, and neuron synapse logical devices. Nevertheless, these applications are obstructed by the present ineffectiveness in the thin film growth of the metastable ReNiO3 with flexibly adjustable rare-earth compositions and electronic structures. Herein, we demonstrate a metal-organic decompositions (MOD) approach that can effectively grow metastable ReNiO3 covering a large variety of the rare-earth composition without introducing any vacuum process. Unlike the previous chemical growths for ReNiO3 relying on strict interfacial coherency that limit the film thickness, the MOD growths using reactive isooctanoate percussors are tolerant to lattice defects and therefore achieves comparable film thickness to vacuum depositions. Further indicated by positron annihilation spectroscopy, the ReNiO3 grown by MOD exhibit large amount of lattice defects that improves their hydrogen incorporation amount and electron transfers, as demonstrated by the resonant nuclear reaction analysis and near edge X-ray absorption fine structure analysis. This effectively enlarges the magnitude in the resistance regulations in particular for ReNiO3 with lighter Re, shedding a light on the extrinsic regulation of the hydrogen induced quantum transitions for correlated oxides semiconductors kinetically via defect engineering.

Research Article
Effect of Ni content on wear behavior of Al-Si-Cu-Mg-Ni/SiCp composites
Yanyu Liu, Lina Jia, Wenbo Wang, Zuheng Jin, and Hu Zhang
Available online 4 July 2023, https://doi.org/10.1007/s12613-023-2701-y
[Abstract](72) [PDF 2119KB](13)

In recent years, it has become widely acknowledged that the addition of nickel (Ni) can enhance the mechanical properties of Al-Si alloys. However, the impact of Ni on the wear behavior of Al-Si alloys and Al matrix composites, particularly at elevated temperatures, remains an understudied area. In this study, Al-Si-Cu-Mg-Ni/20wt% SiCp composites with varying Ni contents were prepared by a semi-solid stir casting method. The effect of Ni content on the dry sliding wear behavior of the prepared composites was investigated by sliding tests at 25℃ and 350℃. The results indicated that the θ-Al2Cu phase gradually diminished and eventually disappeared as the Ni content increases from 0 to 3wt%, accompanied by the formation and increase of the δ-Al3CuNi phase and ε-Al3Ni phase in the microstructure. The hardness and ultimate tensile strength of the as-cast composites are both improved, and the wear rates of the composites are decreased from 5.29 to 1.94 at 25℃ and 20.2 to 7 mm3/(N∙m) at 350℃ with a rise in Ni content from 0 to 2wt%. The enhanced performance is due to the strengthening network structures and the presence of more Ni-containing phases in the composites. However, the wear rate of the 3Ni composite is approximately 2 times higher than that of the 2Ni composite due to the fracture and debonding of the ε-Al3Ni phase. The predominant wear mechanisms of the investigated composites are abrasive wear, delamination wear, and oxidation wear at 25℃, while delamination wear and oxidation wear are dominant during sliding at 350℃.

Research Article
Paraffin-CaCl2·6H2O dosage effects on the strength and heat transfer characteristics of cemented tailings backfill
Hai Li, Aibing Jin, Shuaijun Chen, Yiqing Zhao, and You Ju
Available online 4 July 2023, https://doi.org/10.1007/s12613-023-2700-z
[Abstract](55) [PDF 1060KB](8)

The challenge of high temperatures in deep mining has remained harmful to the health of workers and their production efficiency. Adding phase change materials to filling slurry and using the cold storage function of these phase change materials to reduce downhole temperatures was shown to be an effective approach to alleviate the aforementioned problem. Paraffin-CaCl2·6H2O composite phase change material was prepared in the laboratory. The composition, phase change latent heat, thermal conductivity, and cemented tailings backfill (CTB) compressive strength of the new material were studied. Its heat transfer characteristics and endothermic effect of the phase change material were simulated using Fluent software. The results showed the following: (1) The new paraffin-CaCl2·6H2O composite phase change material improved the thermal conductivity of the native paraffin while avoiding the disadvantageous water solubility of CaCl2·6H2O. (2) The calculation formula of the thermal conductivity of CaCl2·6H2O combined with paraffin was deduced,and the reasons were explained in principle. (3) The “enthalpy–mass scale model” was applied to calculate the latent heat of phase change of nonreactive composite phase change materials. (4) The addition of the composite phase change material Paraffin-CaCl2·6H2O reduces the CTB strength but increases its heat absorption capacity.

Research Article
Preferentially selective extraction of lithium from spent LiCoO2 cathodes by medium-temperature carbon reduction roasting
Daixiang Wei, Wei Wang, Longjin Jiang, Zhidong Chang, Hualei Zhou, Bin Dong, Dekun Gao, Minghui Zhang, and Chaofan Wu
Available online 30 June 2023, https://doi.org/10.1007/s12613-023-2698-2
[Abstract](96) [PDF 966KB](13)

Lithium recovery from spent lithium-ion batteries (LIBs) becomes increasingly important due to the skyrocketing price of lithium. Medium-temperature carbon reduction roasting was reported in this work, which aimed at preferential selective extraction of lithium from spent LiCoO2 (LCO) cathodes to overcome the incomplete recovery and loss of lithium during the recycling process. The LCO layered structure was destroyed and lithium was completely converted into water-soluble Li2CO3 under a suitable temperature to control the reduced state of the cobalt oxide. The Co metal agglomerates generated during medium-temperature carbon reduction roasting were broken by wet grinding and ultrasonic crushing to release the entrained lithium. The results showed that 99.10wt% of the whole lithium could be recovered as Li2CO3 with a purity of 99.55wt%. This study provided a new perspective on the preferentially selective extraction of lithium from spent lithium batteries.

Research Article
Preparation of high purity fluorite and nanoscale calcium carbonate from low grade fluorite
Qianqian Lu, Haisheng Han, Wenjuan Sun, Xingfei Zhang, Weiwei Wang, Bilan Zhang, Wensheng Chen, and Qin Zou
Available online 30 June 2023, https://doi.org/10.1007/s12613-023-2697-3
[Abstract](67) [PDF 1148KB](7)

Flotation separation of calcite from fluorite is a challenge on low grade fluorite flotation, which limits the recovery and purity of fluorite concentrate. This paper proposed a new acid leaching-flotation process for fluorite. This innovative process raised the fluorite's grade to 97.26% while producing nanoscale calcium carbonate from its leachate, which contained plenty of calcium ions. On the production of nanoscale calcium carbonate, the impacts of solid-liquid ratio, pH, temperature, and titration rate were examined. By modifying the process conditions and utilizing crystal conditioning agents, calcite-type calcium carbonate with a particle size of 1.823 μm and amorphous calcium carbonate with a particle size of 1.511 μm were produced. The influence of the impurity ions Mn2+, Mg2+, and Fe3+ was demonstrated to reduce the particle size of nanoscale calcium carbonate and make crystal shape easier to manage in the fluorite leach solution system when compared to calcium chloride solution. The combination of the acid leaching-flotation process and the nanoscale calcium carbonate preparation method improved the grade of fluorite while recovering calcite resources, presenting a novel idea for the effective and clean usage of low-quality fluorite resources with microfine particles embedded.

Research Article
Lattice Boltzmann simulation study of anode degradation in solid oxide fuel cell during initial aging process
Shixue Liu, Zhijing Liu, Shuxing Zhang, and Hao Wu
Available online 17 June 2023, https://doi.org/10.1007/s12613-023-2692-8
[Abstract](77) [PDF 1109KB](11)

There is a rapid performance degradation in the initial aging process of solid oxide fuel cell (SOFC), and the discussion of degradation mechanism needs quantitative analysis. The Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) technique is used to characterize and reconstruct the ceramic microstructures of SOFC anodes. The lattice Boltzmann method (LBM) simulation is performed to simulate the multi-physical and electrochemical processes in the reconstructed models. Two samples taken from industrial size cells are processed, including a reduced reference cell, and a cell with an initial aging process. Statistical parameters of the reconstructed microstructure show a significant decrease in the active triple-phase boundary (TPB) and Ni connectivity in the aged cell compared to the reference cell. The LBM simulation reveals that the activity degradation is the dominant factor compared to the microstructure degradation during the initial aging process, and the electrochemical reactions spread to the support layer in the aged cell. The microstructure degradation and activity degradation can both be attributed to the Ni migration and coarsening.

Research Article
Process metallurgy and data driven prediction and feedback of blast furnace furnace heat indicators
Quan Shi, Jue Tang, and Mansheng Chu
Available online 17 June 2023, https://doi.org/10.1007/s12613-023-2693-7
[Abstract](108) [PDF 1605KB](9)

The prediction and control of furnace heat indicator was of great significance to improve the furnace hot level and furnace condition for the complex and difficult to operate the hour-class delay blast furnace (BF) system. In this work, a prediction and feedback model of furnace heat indicator based on the fusion of data driven and BF ironmaking process was proposed. The data of raw and fuel materials, process operation, smelting state and slag and iron discharge during the whole BF process were comprehensively analyzed, a total of 171 variables, 9223 groups of data. A novel method of delay analysis of furnace heat indicator was established. and the extracted delay variables had played an important role in the modeling. Compared with the traditional machine learning algorithm, the method that combined the Genetic algorithm (GA) and Stacking was efficient to improve the performance. The hit rate for the predicting the temperature of hot metal in the error range of plus or minus 10 ℃ was 92.4%, and that for [Si] in the error range of plus or minus 0.1% was 93.3%. On the basis of the furnace heat prediction model and the expert experience, a feedback model of furnace heat operation was established to push the quantitative operation suggestions to stabilize the BF heat level, which had been highly recognized by the BF operators. Finally, this comprehensive and dynamic model had been successfully applied in the practical BF, and the BF temperature level was improved remarkably with the furnace temperature stability rate increasing from 54.88% to 84.89%, which had achieved significant economic benefits.

Invited Review
Structural survey of metal-covalent organic frameworks and covalent metal-organic frameworks
Chaozhi Xiong, Zhenwu Shao, Jianan Hong, Kexin Bi, Qingsong Huang, and Chong Liu
Available online 14 June 2023, https://doi.org/10.1007/s12613-023-2690-x
[Abstract](230) [PDF 1318KB](10)

This article provides an overview of the latest developments in metal-covalent organic framework (MCOF) and covalent metal-organic framework (CMOF) materials, whose construction entails a combination of both reversible coordination and covalent bonding adapted from metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), respectively. With an emphasis on the structures of MCOFs and CMOFs, this review surveys representative materials’ building blocks and topologies. Specifically, the frameworks are classified based on the dimensions of their components (building blocks): discrete building blocks and 1D infinite building blocks. For the first category, the materials were further divided into collections of two-dimensional (2D) networks and three-dimensional (3D) networks according to their topologies. For the second category, this article mainly covers the recently emerging MCOFs with woven structures. Finally, state-of-the-art in MCOF and CMOF chemistry has laid out promising avenues for future development.

Research Article
High corrosion and wear resistant electroless Ni-P gradient coatings on aviation aluminum alloy parts
Bo Wang, Jiawei Li, Zhihui Xie, Gengjie Wang, and Gang Yu
Available online 6 June 2023, https://doi.org/10.1007/s12613-023-2689-3
[Abstract](88) [PDF 1412KB](12)

A Ni-P alloy gradient coating consisting of multiple electroless Ni-P layers with various phosphorus content was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni-P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion, and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90° and was not corroded visually after 500 h of neutral salt spray test at 35 ℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.

Research Article
The competitive oxidation behavior of Ni-based superalloy GH4738 at extreme temperature
Hui Xu, Shufeng Yang, Enhui Wang, Yunsong Liu, Chunyu Guo, Xinmei Hou, and Yanling Zhang
Available online 6 June 2023, https://doi.org/10.1007/s12613-023-2687-5
[Abstract](109) [PDF 1356KB](18)

Higher thrust-to-weight ratio poses challenges for the high-temperature performance of Ni-based superalloys. The oxidation behavior of GH4738 at extreme temperature has been investigated by isothermal and non-isothermal experiments. Resulted from the competitive diffusion of alloying elements, the oxide scale includes the outermost porous oxide layer (OOL), the inner relatively dense oxide layer (IOL) and internal oxide zone (IOZ) depending on the temperature and time. Higher temperature leads to the formation of big voids at the IOL/IOZ interface. At 1200°C, the continuity of Cr-rich oxide layer in the IOL is destroyed and thus spallation occurs. Extending oxidation time contributes to the size of Al-rich oxide particles within the IOZ increase. Based on this, the oxidation kinetics of GH4738 is discussed and the corresponding oxidation behavior at 900-1100°C is predicted.

Research Article
Fundamental investigation on the precise regulation of pyrolusite ore phase transformation
Ruofeng Wang, Peng Gao, Shuai Yuan, Yanjun Li, Yingzhi Liu, and Cheng Huang
Available online 6 June 2023, https://doi.org/10.1007/s12613-023-2688-4
[Abstract](70) [PDF 1648KB](5)

To achieve the rational utilization of low-grade co-associated complex manganese ore resources, this paper systematically elucidated the mechanism of the phase transformation process of roasting in a reducing atmosphere with pyrolusite ore (MnO2) as the research object. According to the single-factor experiment results, the divalent manganese (Mn2+) reduction rate of the roasted product obtained as 95.30% at a roasting time of 25 min, a roasting temperature of 700°C, a CO concentration of 20at% and a total gas volume of 500 mL·min-1, in which the manganese was mainly in the form of manganosite (MnO). Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) demonstrated the microstructural evolution of the roasted products, and the reduction of pyrolusite ore was completed gradually from the surface to the core. Thermodynamic calculations, X-ray photoelectron spectroscopy(XPS), and X-ray diffractometry (XRD) elucidated that the phase transformation of pyrolusite follows MnO2→Mn2O3→Mn3O4→MnO phase by phase and that the reduction of manganese oxides in each valence state proceeds simultaneously.

Research Article
Improving the electrocatalytic activity of Fe, N co-doped biochar for polysulfides conversion by regulation of N-C and Fe-N configurations
Jingchun Sun, Jindiao Guan, Suqing Zhou, Jiewei Ouyang, Nan Zhou, Chunxia Ding, and Mei-e Zhong
Available online 31 May 2023, https://doi.org/10.1007/s12613-023-2683-9
[Abstract](70) [PDF 2292KB](7)

Conversion of agricultural residual biomass into biochar as sulfur host materials for Li-S batteries is a promising approach to alleviate green house effect and realize waste resource re-utilization. However, the low electrical conductivity and less electocatalytic sites of pristine biochar hinder its large-scale application. Herein, these challenges are addressed by constructing Fe-N co-doped biochar (Fe-NOPC) through co-pyrolysis of sesame shells and NaFeEDTA. During synthesis process, NaFeEDTA can be used as an extra carbon resource to regulate the chemical environment of N-doped, producing high content of graphitic, pyridinic, pyrrolic N, and Fe-Nx bonds. When the resulted Fe-NOPC is used as a sulfur host, the pyridinic and pyrrolic N can greatly adjust the surface electron structure of biochar for accelerating the electron/ion transport, while electropositive graphitic N can combine with sulfur-related species by electrostatic attraction. Moreover, the Fe-Nx is capable of promoting the redox reaction of LiPSs owing to the strong Li-N and S-Fe binding. Benefiting from these advantages, the resultant Fe-NOPC/S cathode with a sulfur loading of 3.8 mg cm-2 delivers an areal capacity of 4.45 mAh cm-2 under 0.1 C, and retains 3.45 mAh cm-2 at 1 C, holding enormous potential for achieving energy-dense Li-S batteries.

Research Article
Enhanced properties of stone coal-based composite phase change materials for thermal energy storage
Baoshan Xie, Huan Ma, Chuanchang Li, and Jian Chen
Available online 31 May 2023, https://doi.org/10.1007/s12613-023-2682-x
[Abstract](89) [PDF 1317KB](13)

Phase change material (PCM) can be incorporated with low-cost minerals to synthesis composite for thermal energy storage in building applications. Stone coal after vanadium extraction treatment shows potential in secondary utilization of composite preparation. This work prepared the stone coal-based composite PCM that stone coal as matrix, stearic acid as PCM, and expanded graphite as additive. To understand the effect of vanadium extraction on promotion of loading capacity and thermal conductivity, the analogous treatment of roasting and acid leaching on raw stone coal was conducted. Results show that the combined treatment of roasting at 900°C and leaching increases the loadage of stone coal in composite by 6.2% due to the improvement of specific surface area. Being contributed by 3% expanded graphite, both loading capacity and thermal conductivity of composite are obviously increased by 127% and 48.19%, respectively. Data is supported by the designed composite which has high loadage of 66.69% and thermal conductivity of 0.59 W m-1 K-1. The obtained composite exhibits phase change temperature of 52.17°C and melting latent heat of 121.5 J g-1, as well as good chemical compatibility. The stone coal-based composite has prospects in building applications by taking advantage of secondary utilization of minerals.

Research Article
Research on the effect of polar and azimuthal angle variations of coarse particles on the structure of drainage channels in the thickened bed
Cuiping Li, Gezhong Chen, Zhuen Ruan, Raimund Bürger, Yuan Gao, Hezi Hou, and Hui Wang
Available online 20 May 2023, https://doi.org/10.1007/s12613-023-2680-z
[Abstract](202) [PDF 1816KB](19)

3D reconstruction and quantitative characterization of the drainage channels and the coarse tailings particles in the bed were carried out in this study. The influence of the variations in the azimuthal angle (θ) and polar angle (φ) of the coarse particles on the drainage channel structure was analyzed, and the drainage mechanism of the bed was studied. Results show that water discharge in the bed reduces the size of pores and throat channels, increasing the slurry concentration. The throat channel structure is a key component of the drainage process. The φ and θ of the particles were changed predominantly along the length-axis direction. Changes in particle φ have a cumulative plugging effect on the drainage channel, and increase the difficulty of water discharge. The rake and rod form a shear ring in the tailings bed when with shear, and the rotation process realizes the particle θ from disorderly distribution to an orderly arrangement. The drainage channel is squeezed during the shearing process by the change in particle θ, which breaks the channel structure, encourages water discharge in the bed, and facilitates a further increase in slurry concentration. This finding is expected to offer theoretical guidance for preparing high-concentration underflow in the tailings thickening process.

Research Article
Kinetics of solid state reduction of chromite over burden
Saida Shaik, Zhiyaun Chen, Preeti Prakash Sahoo, and Chenna Rao Borra
Available online 19 May 2023, https://doi.org/10.1007/s12613-023-2681-y
[Abstract](218) [PDF 1023KB](23)

There is a rise in demand for alternative low-grade iron ores, due to the rapid depletion of high-grade natural iron ore resources and an increase in the need for steel usage in daily life. However, using low-grade iron ores is always a clinical task for industry metallurgists. Direct smelting of low-grade ores consumes a lot of energy due to the large volume of slag generation. This can be avoided by direct reduction followed by magnetic separation (to separate the high gangue or refractory and metal parts) and smelting. Chromite overburden (COB) is a mine waste generated in chromite ore processing which mainly consists of iron, chromium and nickel (<1%). In the present work, the isothermal and non-isothermal kinetics of solid-state reduction of self-reduced pellets prepared by using low-grade iron ore (COB waste) were thoroughly investigated using thermal analysis. Results show that the reduction of pellets follows a first-order autocatalytic reaction control mechanism in the temperature range 900oC to 1100oC. The autocatalytic nature of the reduction reaction is due to the presence of nickel in the COB. The apparent activation energy values obtained from the kinetics results show that the solid-state reactions between COB and carbon are the rate-determining step in iron oxide reduction.

Research Article
Effect of Zn content on microstructure, mechanical properties and thermal conductivity of extruded Mg-Zn-Ca-Mn alloys
Bei Tang, Jinlong Fu, Jingkai Feng, Xiting Zhong, Yangyang Guo, and Haili Wang
Available online 17 May 2023, https://doi.org/10.1007/s12613-023-2676-8
[Abstract](127) [PDF 1486KB](17)

Mg-Zn-Ca-Mn series alloys are developed as promising candidates of 5G communication devices with high strength and excellent thermal conductivities. In present paper, extruded Mg-xZn-0.4Ca-0.2Mn (x=2, 4, 6 wt.%) alloys were prepared and the effect of Zn content on the mechanical and physical properties were investigated. The results showed that the addition of minor Ca led to the formation of Ca2Mg6Zn3 eutectic phase at grain boundaries. A bimodal microstructure occurred in the as-extruded alloys, where elongated coarse deformed grains were embedded in refined recrystallized grains matrix. Correspondingly, both the yield strength and the ductility were significantly enhanced after extrusion due to the great grain refinement and random grain orientation of the recrystallized grains. Specially, higher yield strength and slightly reduced elongation were obtained in the alloys containing higher Zn content. Fine grain strengthening and basal texture strengthening were the main strengthening mechanisms for the as-extruded alloy. The thermal conductivity of as-extruded alloys was also improved compared with that of as-cast ones. The room temperature thermal conductivity of both as-cast and as-extruded alloys decreased with the increment of Zn content, which was due to the increased second phase fraction and solution atoms, that hindering the motion of the electrons. Mg-2Zn-0.4Ca-0.2Mn (wt.%) alloy in the as-extruded state exhibited a balanced mechanical properties and thermal properties, with ultimate tensile strength of 244.0 MPa, elongation to failure of 27.7% and thermal conductivity of 139.2 W/(m•K). The present paper may provide some scientific guidance for the preparation of lightweight materials with high ductility and high thermal conductivity materials.

Research Article
N-doped graphene quantum dots-decorated N-TiO2/P-doped porous hollow g-C3N4 nanotube composite photocatalysts for antibiotics photodegradation and H2 production
Jingshu Yuan, Yao Zhang, Xiaoyan Zhang, Junjie Zhang, and Shengen Zhang
Available online 17 May 2023, https://doi.org/10.1007/s12613-023-2678-6
[Abstract](102) [PDF 1610KB](10)

The responsiveness to UV light only (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO2. Accordingly, we combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQDs/N-TiO2/P-doped porous hollow g-C3N4 nanotube (PCN) composite photocatalysts. The optimal sample (0.1%G-TPCN) exhibits significantly enhanced photoabsorption due to the change in bandgap caused by elemental doping (P, N), improved light harvesting resulting from hollow tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of 0.1%G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO2, PCN, and N-TiO2/PCN (TPCN-1), respectively. This is attributed to the formation of Z-scheme heterojunction between N-TiO2 and PCN, excellent electron conduction ability of N-GQDs, and shorter transfer distance by porous nanotube structure. Compared to N-TiO2, PCN, and TPCN-1, H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4 times, and ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7 and 2.9 times, respectively. The optimized performance is contributed to the excellent photoresponsiveness and improved carrier separation and migration efficiency. Finally, the photocatalytic mechanism of 0.1%G-TPCN and five possible degradation pathways of CIP were proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1%G-TPCN and also suggests a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.

Research Article
Highly dispersed NiMo@rGO nanocomposite catalysts fabricated by a two-step hydrothermal method for hydrogen evolving
Duanhao Cao, Xiaofeng Ma, Yipeng Zhang, La Ta, Yakun Yang, Chao Xu, Feng Ye, and Jianguo Liu
Available online 17 May 2023, https://doi.org/10.1007/s12613-023-2677-7
[Abstract](131) [PDF 1943KB](13)

Exploring and designing a high-performance non-noble metal catalyst for hydrogen evolution reaction (HER) can be one of important factors for the large-scale application of H2 by water electrolysis. In this work, we reported novel catalysts with Ni-Mo nanoparticles decorated on reduced graphene oxide (NiMo@rGO) synthesized by a two-step hydrothermal method. The physical characterization results showed that the prepared NiMo@rGO-1 had irregular lamellar structure, and the Ni-Mo nanoparticles were uniformly dispersed on the rGO. NiMo@rGO-1 exhibited outstanding HER performance in alkaline environment, and it required only 93 and 180 mV overpotential for HER in 1.0 M KOH solution to obtain current densities of -10 and -50 mA cm−2, respectively. In addition, the stability test of NiMo@rGO-1 showed that it had a certain operating stability for 32 h. In the same condition, the performance of NiMo@rGO-1 can be comparable to that of commercial Pt/C catalysts at high current density. The synergistic effect between Ni-Mo particles and lamellate graphene can significantly promote charge transfer in electrocatalytic reactions. As a result, NiMo@rGO-1 presented the advantages of high intrinsic activity, large specific surface area, and small electrical impedance. Meanwhile, the lamellar graphene played the role of dispersion to prevent the aggregation of nanoparticles. The preparation of NiMo@rGO-1 can be used in anion exchange membrane electrolysis of water to produce hydrogen. It provides a simple preparation method for efficient and low-cost water electrolysis to produce hydrogen in the future.

Research Article
Prediction model for corrosion rate of low-alloy steels under atmospheric conditions using machine learning algorithms
Jingou Kuang and Zhilin Long
Available online 17 May 2023, https://doi.org/10.1007/s12613-023-2679-5
[Abstract](121) [PDF 1162KB](15)

We constructed a machine learning (ML) model to predict the atmospheric corrosion rate of low-alloy steels (LAS). The material properties of LAS, environmental factors, and exposure time were used as the input, while the corrosion rate was obtained as the output. A total of six ML algorithms were used to construct the proposed model. Through optimization and filtering, the eXtreme gradient boosting (XGBoost) model exhibited good corrosion rate prediction accuracy. The features of material properties were then transformed into atomic and physical features using the proposed property transformation approach, and the dominant descriptors that affected the corrosion rate were filtered using the recursive feature elimination (RFE) as well as XGBoost methods. The established ML models exhibited better prediction performance and generalization ability via property transformation descriptors. In addition, we applied the SHapley Additive exPlanations (SHAP) method to analyze the relationship between these descriptors and the corrosion rate. The results showed that the property transformation model could effectively help with analyzing the corrosion behavior, thereby significantly improving the generalization ability of corrosion rate prediction models.

Research Article
Ferric ions-triggered surface oxidation of galena for efficient chalcopyrite-galena separation
Qiancheng Zhang, Limin Zhang, Feng Jiang, Honghu Tang, Li Wang, and Wei Sun
Available online 12 May 2023, https://doi.org/10.1007/s12613-023-2674-x
[Abstract](137) [PDF 946KB](12)

Efficient separation of chalcopyrite and galena is essential for optimal resource utilization. However, finding a selective depressant that is both environmentally friendly and cost-effective remains a challenge. This study explores the use of ferric ions (Fe3+) as a selective depressant for galena through various techniques such as micro-flotation tests, Fourier Transform Infrared Spectroscopy (FT-IR) analysis, Scanning Electron Microscope (SEM) observation, X-ray Photoelectron Spectroscopy (XPS) studies, and Raman Spectra measurements. The results of the flotation tests revealed the impressive selective inhibition capabilities of Fe3+ when used alone. Surface analysis showed that Fe3+ significantly reduced the adsorption of isopropyl ethyl thionocarbamate (IPETC) on the galena surface, while having minimal impact on chalcopyrite. Further analysis using SEM, XPS, and Raman spectra revealed that Fe3+ can oxidize lead sulfide (PbS) to form compact lead sulfate (PbSO4) nanoparticles on the galena surface, effectively depressing IPETC adsorption and increasing surface hydrophilicity. These findings provide a promising solution for efficient and environmentally responsible separation of chalcopyrite and galena.

Invited Review
Functional carbon dots for corrosion protection: Recent advances and future perspectives
Li Zhao, Jinke Wang, Kai Chen, Jingzhi Yang, Xin Guo, Hongchang Qian, Lingwei Ma, and Dawei Zhang
Available online 12 May 2023, https://doi.org/10.1007/s12613-023-2675-9
[Abstract](96) [PDF 2184KB](8)

Metal corrosion can result in significant economic losses, safety issues, and environmental pollution, which has attracted great research interests. Carbon dots (CDs), a new class of zero-dimensional carbon nanomaterials, have recently been proposed for corrosion protection applications due to their excellent properties such as corrosion inhibition effect, fluorescence property, low toxicity, facile chemical modification, and cost-effectiveness. This study provides a comprehensive overview of the preparation methods, physical and chemical properties, and anti-corrosion mechanisms of functional CDs. The corrosion inhibition performance of different kinds of CDs is first introduced, followed by the discussions on application of CDs in the development of smart protective coatings with self-healing and/or self-reporting properties. The effective barrier formed by CDs in the coatings can inhibit local damage expansion and achieve the self-healing property. In addition, the diverse functional groups of CDs can interact with Fe3+ and H+ ions generated during corrosion process to change the fluorescence of CDs, so as to achieve the self-reporting property. More importantly, the challenges and future prospects for the development of CDs-based corrosion protection systems are proposed.

Research Article
A quasi-solid-state sodium-air battery fabricated by gelatinous Na-BP-DME@C anode and succinonitrile plastic crystal cathode electrolyte
Zhengang Zhao, Xiecheng Yang, Bowen Xu, Wenhui Niu, Kun Ren, Minjie Hou, Da Zhang, Yong Lei, and Feng Liang
Available online 12 May 2023, https://doi.org/10.1007/s12613-023-2673-y
[Abstract](224) [PDF 909KB](45)

Rechargeable sodium-air batteries (SABs) are one of the most promising contestants in the field of energy storage and conversion. Despite the superior electrochemical performance of aqueous SABs, ensuring a long cycle life and high safety in practical applications of SABs remains challenging owing to the use of volatile aqueous electrolyte. In the paper, a novel quasi-solid-state SAB is fabricated by utilizing sodium biphenyl solution/carbon black composite (Na-BP-DME@C) anode and 92.5wt% succinonitrile (SN) plastic crystal cathode electrolyte. The gelatinous Na-BP-DME@C anode makes good interfacial contact with Na3Zr2Si2PO12 (NASICON), and facilitates interfacial electron transfer due to the high conductivity. In addition, 92.5wt% SN plastic crystal electrolyte is substituted for aqueous electrolyte, which has excellent stability to air, and ensures good physical contact and interfacial charge transfer kinetics between the catalytic cathode and NASICON. The constructed quasi-solid-state SAB exhibits a small voltage gap of 1.2 V, excellent cycle performance (nearly 374 h at 0.1 mA cm−2), and a high discharge capacity of 4.96 mAh at 0.5 mA cm−2. This study provides a strategy for manufacturing quasi-solid-state SABs, which could greatly contribute to the development of solid-state metal-air batteries.

Research Article
Hybrid model for BOF oxygen blowing time prediction based on oxygen balance mechanism and deep neural network
Xin Shao, Qing Liu, Zicheng Xin, Jiangshan Zhang, Tao Zhou, and Shaoshuai Li
Available online 12 May 2023, https://doi.org/10.1007/s12613-023-2670-1
[Abstract](83) [PDF 1085KB](13)

The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process, which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. Firstly, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Secondly, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error ± 300 Nm3 is 96.67%; R2 and RMSE are 0.6984 and 150.03 Nm3, respectively. The oxygen blow time prediction hit ratio within the error ± 0.6 min is 89.50%; R2 and RMSE are 0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.

Research Article
Residual stress measurement and analysis of siliceous slate-containing quartz veins
Tao Wang, Weiwei Ye, Yemeng Tong, Naisheng Jiang, and Liyuan Liu
Available online 29 April 2023, https://doi.org/10.1007/s12613-023-2667-9
[Abstract](183) [PDF 1798KB](15)

Engineering geological disasters such as rockburst have always been a critical factor affecting the safety of coal mine production. The study of residual stress is considered a feasible method for explaining these geomechanical phenomena. In this study, electron back-scattered diffraction (EBSD) and optical microscopes were utilized to characterize the rock microcosm. A measuring area that met the requirements of X-ray diffraction (XRD) residual stress measurement was determined to account for the mechanism of rock residual stress. The residual stress of siliceous slate-containing quartz vein was then measured and calculated using the sin2ψ method with an X-ray diffractometer. The analysis of microscopic test results showed that there were homogeneous areas with small-sized particles within the millimeter range, meeting the requirements of XRD stress measurement statistics. Quartz was determined as the calibration mineral for the slate samples containing quartz veins. The diffraction patterns of (324) crystal planes were obtained under different ψ and φ. The deviation direction of the diffraction peaks was consistent, proving that the sample tested had residual stress. In addition, the principal residual stress within the quartz vein measured by XRD was compressive, ranging from 10 to 33 MPa. The maximum principal stress was parallel to the vein trend, while the minimum principal stress was perpendicular to the vein trend. Furthermore, the content of the low-angle boundary and twin boundary in the quartz veins was relatively high, giving the rock mass stronger resistance to deformation and making it easier to form strain concentrations, resulting in residual stress. The proposed method for measuring residual stress can serve as a reference for subsequent observation and related research of residual stress in different types of rocks.

Research Article
Hot deformation behavior and microstructure evolution of Be/2024Al composites
Yixiao Xia, Zeyang Kuang, Ping Zhu, Boyu Ju, Guoqin Chen, Ping Wu, Wenshu Yang, and Gao-hui Wu
Available online 26 April 2023, https://doi.org/10.1007/s12613-023-2662-1
[Abstract](124) [PDF 2248KB](16)
The high temperature compression tests of Be/2024Al composites with 62wt.% beryllium was conduct at 500~575ºC and strain rate of 0.003~0.1 s-1. Both strain-compensated Arrhenius model and modified Johnson-Cook model were introduced to predict the hot deformation behavior of Be/2024Al composites. The result shows that the activation energy of Be/2024Al composites was 363.364 kJ/mol. Compared with composites reinforced with traditional ceramics, Be/2024Al composites can be deformed with ultra-high content of reinforcement, which can be owed to the deformable property of beryllium particles. The average relative error of the two models shows that modified Johnson-Cook model was more suitable for low temperature condition while strain-compensated Arrhenius model was more suitable for high temperature condition. The processing map was generated and a hot extrusion experiment was conducted according to the map. A comparation of the microstructure of Be/2024Al before and after extrusion shows that the beryllium particle deformed coordinately with the matrix and elongated at the extrusion direction.
Invited Review
Recent advances and perspectives of zinc metal-free anode for zinc-ion batteries
Jiabing Miao, Yingxiao Du, Ruotong Li, Zekun Zhang, Ningning Zhao, Lei Dai, Ling Wang, and Zhangxing He
Available online 26 April 2023, https://doi.org/10.1007/s12613-023-2665-y
[Abstract](127) [PDF 1491KB](14)
With its advantages of low cost, high energy density and environmental friendliness, zinc ion batteries (ZIBs) are recognized as potential energy storage devices. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. On this basis, this work systematically introduces the research progress of zinc metal-free anodes in "rocking chair" ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides, transition metal sulfides, MXene composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. It is expected that this paper will provide a reference for the further promotion of commercial rechargeable zinc-ion batteries.
Research Article
Waste heat recovery from hot steel slag on production line: Numerical simulation, validation and industrial test
Tianhua Zhang, Longheng Xiao, Guibo Qiu, Huigang Wang, Min Guo, Xiangtao Huo, and Mei Zhang
Available online 22 April 2023, https://doi.org/10.1007/s12613-023-2660-3
[Abstract](95) [PDF 1286KB](19)

The waste heat was resumed from hot steel slag in a granular bed by the combination of numerical simulation and industrial test method. Firstly, the effective thermal conductivity of the granular bed was calculated, and then the unsteady state model was used to simulate the heat recovery from three different flow fields (O-type, S-type and Non shielding type (Non-type)). Secondly, the validation of simulation results was conducted by in-suit industrial experiments. Both of these two methods confirmed that the heat recovery efficiency of flow field order from high to low was Non-type, S-type and O-type. Finally, the heat recovery was carried out under Non-type flow field in industrial test, and the heat recovery efficiency increased from ~76%, ~78% to ~81% when the steel slag thickness decreased from 400, 300 to 200 mm, corresponding to the decrease of steel slag mass from 3.96, 2.97 to 1.98 t with a blower air volume of 14687 Nm3/h. Therefore, the research results showed that numerical simulation can not only guide the experiments of waste heat recovery, but also optimize the flow field. Most importantly, this method achieved a higher recovery rate of waste heat in industrial sense.

Research Article
Stress-assisted corrosion mechanism study of 3Ni steel based on gradient boosting decision tree machining-learning method
Xiaojia Yang, Jinghuan Jia, Qing Li, Renzheng Zhu, Jike Yang, Zhiyong Liu, Xuequn Cheng, and Xiaogang Li
Available online 22 April 2023, https://doi.org/10.1007/s12613-023-2661-2
[Abstract](98) [PDF 2780KB](10)

Traditional 3Ni weathering steel cannot fully meet the requirement of offshore engineering development, the design of novel 3Ni steel with the addition of micro-alloy element such as Mn or Nb to enhance the strength has become a trend. In this study, the stress-assisted corrosion behavior of the novel designed high strength 3Ni steel is studied by corrosion big data method. The information of the corrosion process was recorded by using galvanic corrosion current monitoring method. Gradient boosting decision tree (GBDT) machine-learning method was used to mining the corrosion mechanism and the importance of the structure factor was studied. Field exposure tests were held to verify the results calculated by GBDT method. Results depict that GBDT method can be used to effectively study the influence of structural factor on the corrosion process of 3Ni steel. Different mechanism for the addition of Mn and Cu on the stress-assisted corrosion of 3Ni steel suggest that Mn and Cu have no obvious effect on the corrosion rate of non-stressed 3Ni steel in the early stage of corrosion, when the corrosion reaches a stable state, the increase of Mn element content can increase the corrosion rate of 3Ni steel, while Cu reduces the corrosion rate of 3Ni steel. The increase of Mn element content and Cu addition could inhibit the corrosion process in the presence of stress. The corrosion law of outdoor exposure 3Ni steel is consistent with the law based on corrosion big data technology, which verifies the reliability of big data evaluation method and data prediction model selection.

Research Article
Preparation of calcium-based sorbents from Ca-Mg-Si-Al solution
Yumeng Li, Qing Zhao, Xiaohui Mei, Chengjun Liu, Henrik Saxén, and Ron Zevenhoven
Available online 19 April 2023, https://doi.org/10.1007/s12613-023-2657-y
[Abstract](136) [PDF 1055KB](10)

The iron and steel industry of China faces urgent demands for both steel slag utilization and CO2 abatement. Previous works have successfully modified the stainless steel slag for the dual goal of Cr immobilization and Ca/Mg recovery. In this paper, Ca-Mg-Si-Al solution is determined after acetic acid leaching treatment of modified stainless steel slag. The calcium-based sorbents are prepared from Ca-Mg (Si-Al) solution by co-precipitation. The effects of different contents of MgO on the morphology, structure, and CO2 chemisorption capacity of the sorbents were investigated by doping the inert component MgO, and the skeleton support effect of MgO in calcium-based sorbents was determined. The chemisorption kinetics of the sorbents was studied using the Avrami-Erofeev model. There were two processes of CO2 chemisorption, and the activation energy of the first stage (reaction control) was found to be lower than that of the second stage (diffusion control). The initial CO2 chemisorption capacity of the sorbent prepared from the Ca-Mg-rich simulated solution was 0.60 g/g after pretreatment, and the initial CO2 chemisorption capacity of the sorbent prepared from Ca-Mg-Si-Al solution was verified to be 0.4 g/g, which implies that part of the CO2 emissions from steelmaking could be captured in this way.

Research Article
Insights into the oxidation resistance mechanism and tribological behaviors of multilayered TiSiN/CrVxN hard coatings
Hongbo Ju, Moussa Athmani, Jing Luan, Abbas AL-Rjoub, Albano Cavaleiro, Talha Bin Yaqub, Abdelouahad Chala, Fabio Ferreira, and Filipe Fernandes
Available online 18 April 2023, https://doi.org/10.1007/s12613-023-2655-0
[Abstract](204) [PDF 1296KB](18)

In the last decades, vanadium alloyed coatings have been introduced as potential candidates for self-lubrication due to their perfect tribological properties. In this work, the influence of V incorporation on the wear performance and oxidation resistance of TiSiN/CrN films coatings deposited by D.C. reactive magnetron sputtering is investigated. The results show that vanadium incorporation significantly decreases the oxidation resistance of the coatings. In general, two layers are formed during the oxidation process: i) Ti(V)O2 on top followed by a protective layer, which is subdivides into two layers: Cr2O3 and Si-O. The diffusion of V controls the oxidation process of V containing coatings. Addition of vanadium improves the wear resistance of coatings, and the wear rate decreases with increasing V content in the coatings, however, the friction coefficient is independently on the chemical composition of the coatings. The wear of the V-containing coatings is driven by polishing wear.

Research Article
High throughput screening of localised and general corrosion in type 2205 duplex stainless steel at ambient temperature
Yiqi Zhou, Sultan Mahmood, and Dirk Lars Engelberg
Available online 12 April 2023, https://doi.org/10.1007/s12613-023-2651-4
[Abstract](121) [PDF 370KB](14)

Bipolar electrochemistry is used to produce a linear potential gradient across a bipolar electrode (BPE), providing direct access to the anodic and cathodic reactions under a wide range of applied potentials. The occurrence of pitting corrosion, crevice corrosion, and general corrosion on type 2205 duplex stainless steel (DSS 2205) BPE has been observed at room temperature. The critical pit depth of 10-20 μm, with a 55-75% probability of pits developing into stable pits at potential from +0.9 VOCP to +1.2 VOCP are measured. All pit nucleation sites are either within ferritic grains or at the interface between austenite and ferrite. The critical conditions for pitting and crevice corrosion are discussed, with Epit and Ecrevice decreasing from 0.87 VOCP /0.80 VOCP after 150 s of exposure to 0.84 VOCP/0.76 VOCP after 900 s of exposure. Pit growth kinetics under different applied bipolar potentials and exposure times have been obtained. The ferrite is shown to be more susceptible to general dissolution.

Research Article
Effect of ammonium sulfate on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation
Xi Zhang, Yu Wang, Jiushuai Deng, Zhongyi Bai, Hongxiang Xu, Qingfeng Meng, Da Jin, and Zhenwu Sun
Available online 12 April 2023, https://doi.org/10.1007/s12613-023-2650-5
[Abstract](109) [PDF 737KB](19)

Effectively strengthening the surface sulfidation is essential for recovering hemimorphite by froth flotation. In this work, ICP-OES measurements, Visual MINTEQ calculation, XPS analysis, ToF-SIMS analysis, and micro-flotation experiments were explored to systematically investigate the effect of ammonium sulfate ((NH4)2SO4) on the formation of zinc sulfide species on hemimorphite surface and its role in sulfidation flotation. The results showed that (NH4)2SO4 exhibited a positive influence on hemimorphite sulfidation flotation. It was ascribed to the number of zinc components in the form of Zn2+ and [Zn(NH3)i]2+ (i = 1 - 4) increased in the flotation system after hemimorphite treatment with (NH4)2SO4, which was beneficial to its interaction with sulfur species in solution, resulting in a dense and stable zinc sulfide layer was generated on the hemimorphite surface. [Zn(NH3)i]2+ participated in the sulfidation reaction of hemimorphite as a transition state. In addition, the sulfidation reaction of hemimorphite was accelerated by (NH4)2SO4. Thus, (NH4)2SO4 presents a vital role in promoting the sulfidation of hemimorphite.

Research Article
Study on anisotropy of mechanical properties of 2297-T87 Al-Li alloy thick plate
Yuji Bai, Zhixiu Wang, Bo Jiang, Mengqi Li, Cong Zhu, Xiaotong Gu, and Hai Li
Available online 12 April 2023, https://doi.org/10.1007/s12613-023-2652-3
[Abstract](98) [PDF 1921KB](10)

The tensile properties of 2297-T87 Al-Li alloy thick plate at different thickness positions and in different directions were analyzed by means of tensile test, optical microscopy (OM), X-ray diffraction, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM). The results show that the ultimate tensile strength (UTS) and yield strength (YS) of the alloy decrease first and then increase from the 1/8T position to the 1/2T position, whilst the elongation to failure (Ef) decrease gradually that the values of Ef along the rolling direction (RD) is higher than that along the transverse direction (TD) at the same thickness position. From the 1/8T position to the 3/8T position of the alloy, the UTS and YS values along the TD are higher than that along the RD. At the 1/2T position of the alloy, the values of the UTS, YS and Ef along the RD are the highest, whilst that along the normal direction (ND) are the lowest. Microstructure observations revealed that the anisotropy of tensile properties is related to grain morphology, crystal texture, second-phase-particles and Li atom segregation.

Invited Review
State of the art in applications of machine learning in steelmaking process modeling
Runhao Zhang and Jian Yang
Available online 8 April 2023, https://doi.org/10.1007/s12613-023-2646-1
[Abstract](202) [PDF 1784KB](30)

With the development of automation and informatization in the steelmaking industry, the human brain is gradually unable to cope with more and more data generated during the steelmaking process. Machine learning technology provides a new method other than production experience and metallurgical principle in dealing with the large amounts of data. The application of the machine learning in the steelmaking process has become a research hotspot in recent years. This paper provides an overview of the applications of machine learning in the steelmaking process modeling involving hot metal pretreatment, primary steelmaking, secondary refining and some other aspects The three most frequently used machine learning algorithms in steelmaking process modeling are artificial neural network, support vector machine and case-based reasoning, with the proportions of 56%, 14 % and 10%, respectively. Since the data collected in the steelmaking plants are frequently faulty, the data processing, especially the data cleaning, is crucially important to the performance of machine learning model. The detection of variable importance can be used to optimize the process parameters and guide the production. Machine learning is used in hot metal pretreatment modeling mainly for the endpoint S content prediction. The predictions of the endpoints of element compositions and the process parameters are widely investigated in the primary steelmaking. Machine learning is used in the secondary refining modeling mainly for LF (ladle furnace), RH (Ruhrstahl Heraeus), VD (vacuum degassing), AOD (argon oxygen decarburization) and VOD (vacuum oxygen decarburization) processes. For the further development of machine learning in the steelmaking process modeling, more efforts should be made in the construction of the data platform, the industrial transformation of the research achievements to the practical steelmaking process, and the improvement of the universality of the machine learning models.

Research Article
Study on residual stress with asymmetric spray quenching for aluminum alloy thick plates
Ning Fan, Zhihui Li, Yanan Li, Xiwu Li, Yong'an Zhang, and Baiqing Xiong
Available online 8 April 2023, https://doi.org/10.1007/s12613-023-2645-2
[Abstract](83) [PDF 1936KB](7)

The solution and quenching heat treatment are generally carried out in a roller hearth furnace for large-scale aluminum alloy thick plates. However, the asymmetric or uneven spray water flow rate is inevitable under industrial production conditions which leads to asymmetric residual stress distribution. In this paper, the spray quenching treatment was conducted on self-designed spray equipment and the residual stress along thickness direction was measured by layer removal method based on deflections. With the asymmetric spray quenching condition, the subsurface stress of the higher flow rate surface is lower than that of the lower flow rate surface and the difference between the two subsurface stresses increases with the increasing of difference in water flow rates. The subsurface stress underneath surface with water flow rate of 0.60 m3/h is 15.38 MPa less than the one of 0.15 m3/h. The simulated residual stress by FEM of the higher HTC surface is less than that of the lower HTC surface which is consistent with experimental results. The FE model can be used to analyze the strain and stress evolution and to predict quenched stress magnitude and distribution.

Research Article
An integrated and efficient process for borax preparation and magnetite recovery from soda-ash roasted ludwigite ore under CO−CO2−N2 atmospheres
Jinxiang You, Jing Wang, Mingjun Rao, Xin Zhang, Jun Luo, Zhiwei Peng, and Guanghui Li
Available online 7 April 2023, https://doi.org/10.1007/s12613-023-2643-4
[Abstract](109) [PDF 2543KB](24)

For the comprehensive utilization of ludwigite ore, an integrated route for the efficient boron and iron separation was proposed in this work, via soda-ash roasting under CO-CO2-N2 atmospheres followed by grind-leaching, magnetic separation and CO2 carbonation. Influences of roasting temperature, roasting time, CO/(CO+CO2) composition and Na2CO3 dosage were primarily investigated. Under the optimized conditions of the roasting temperature of 850oC, roasting time of 60 min, soda ash dosage of 20wt% and CO/(CO+CO2) of 10%, 92wt% of boron was leached during wet grinding, and 88.6wt% of iron was recovered in the magnetic concentrate with a total iron content of 61.51wt%. Raman spectra and 11B NMR results indicate that boron exists as B(OH)4- in the leachate, from which high-purity borax pentahydrate could be prepared by CO2 carbonation.

Research Article
Effect of Sr2+ on 3D gel-printed Sr3-xMgx(PO4)2 composite scaffolds for bone tissue engineering
Hongyuan Liu, Jialei Wu, Siqi Wang, Jing Duan, and Huiping Shao
Available online 30 March 2023, https://doi.org/10.1007/s12613-023-2638-1
[Abstract](93) [PDF 1410KB](10)

Porous magnesium strontium phosphate (Sr3-xMgx(PO4)2) (x=2, 2.5, 3) composite scaffolds were successfully prepared by 3D gel-printing (3DGP) method in this study. The results show that Sr0.5Mg2.5(PO4)2 scaffolds had good compressive strength, and Sr1.0Mg2.0(PO4)2 scaffolds had good degradation rate in vitro. The weight loss rate of Sr1.0Mg2.0(PO4)2 scaffolds soaked in SBF for 6 weeks was 6.96%, and pH value varied between 7.50 and 8.61, which was within the acceptable range of human body. Preliminary biological experiment shows that MC3T3-E1 cells had good adhesion and proliferation on the surface of Sr3-xMgx(PO4)2 scaffolds. Compared with pure Mg3(PO4)2 scaffolds, strontium doped scaffolds had excellent comprehensive properties, which explain that Sr3-xMgx(PO4)2 composite scaffolds can be used for bone tissue engineering.

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Research Article
Enhanced photocatalytic performance of iron oxides@HTCC fabricated from zinc extraction tailings for methylene blue degradation: Investigation of the photocatalytic mechanism
Yang Xue, Xiaoming Liu, Na Zhang, Yang Shao, and Chunbao (Charles) Xu
  Available online 10 August 2023, https://doi.org/10.1007/s12613-023-2723-5
[FullText HTML](62) [PDF 3896KB](11) SpringerLink
Photocatalytic processes are efficient methods to solve water contamination problems, especially considering dyeing wastewater disposal. However, high-efficiency photocatalysts are usually very expensive and have the risk of heavy metal pollution. Recently, an iron oxides@hydrothermal carbonation carbon (HTCC) heterogeneous catalyst was prepared by our group through co-hydrothermal treatment of carbohydrates and zinc extraction tailings of converter dust. Herein, the catalytic performance of the iron oxides@HTCC was verified by a non-biodegradable dye, methylene blue (MB), and the catalytic mechanism was deduced from theoretical simulations and spectroscopic measurements. The iron oxides@HTCC showed an excellent synergy between photocatalysis and Fenton-like reactions. Under visible-light illumination, the iron oxides@HTCC could be excited to generate electrons and holes, reacting with H2O2 to produce \begin{document}$\cdot\mathrm{O}\mathrm{H}$\end{document} radicals to oxidize and decompose organic pollutants. The removal efficiency of methylene blue over iron oxides@HTCC at 140 min was 2.86 times that of HTCC. The enhanced catalytic performance was attributed to the advantages of iron oxides modification: (1) promoting the excitation induced by photons; (2) improving the charge transfer. Furthermore, the iron oxides@HTCC showed high catalytic activity in a wide pH value range of 2.3–10.4, and the MB removal efficiency remained higher than 95% after the iron oxides@HTCC was recycled 4 times. The magnetically recyclable iron oxides@HTCC may provide a solution for the treatment of wastewater from the textile industry.
Invited Review
Recent research progress on the phase-field model of microstructural evolution during metal solidification
Kaiyang Wang, Shaojie Lv, Honghui Wu, Guilin Wu, Shuize Wang, Junheng Gao, Jiaming Zhu, Xusheng Yang, and Xinping Mao
  Available online 13 July 2023, https://doi.org/10.1007/s12613-023-2710-x
[FullText HTML](235) [PDF 8156KB](40) SpringerLink
Solidification structure is a key aspect for understanding the mechanical performance of metal alloys, wherein composition and casting parameters considerably influence solidification and determine the unique microstructure of the alloys. By following the principle of free energy minimization, the phase-field method eliminates the need for tracking the solid/liquid phase interface and has greatly accelerated the research and development efforts geared toward optimizing metal solidification microstructures. The recent progress in the application of phase-field simulation to investigate the effect of alloy composition and casting process parameters on the solidification structure of metals is summarized in this review. The effects of several typical elements and process parameters, including carbon, boron, silicon, cooling rate, pulling speed, scanning speed, anisotropy, and gravity, on the solidification structure are discussed. The present work also addresses the future prospects of phase-field simulation and aims to facilitate the widespread applications of phase-field approaches in the simulation of microstructures during solidification.
Research Article
FeCoNiCrMo high entropy alloy nanosheets catalyzed magnesium hydride for solid-state hydrogen storage
Tao Zhong, Haoyu Zhang, Mengchen Song, Yiqun Jiang, Danhong Shang, Fuying Wu, and Liuting Zhang
  Available online 6 May 2023, https://doi.org/10.1007/s12613-023-2669-7
[FullText HTML](302) [PDF 3511KB](23) SpringerLink
The catalytic effect of FeCoNiCrMo high entropy alloy nanosheets on the hydrogen storage performance of magnesium hydride (MgH2) was investigated for the first time in this paper. Experimental results demonstrated that 9wt% FeCoNiCrMo doped MgH2 started to dehydrogenate at 200°C and discharged up to 5.89wt% hydrogen within 60 min at 325°C. The fully dehydrogenated composite could absorb 3.23wt% hydrogen in 50 min at a temperature as low as 100°C. The calculated de/hydrogenation activation energy values decreased by 44.21%/55.22% compared with MgH2, respectively. Moreover, the composite’s hydrogen capacity dropped only 0.28wt% after 20 cycles, demonstrating remarkable cycling stability. The microstructure analysis verified that the five elements, Fe, Co, Ni, Cr, and Mo, remained stable in the form of high entropy alloy during the cycling process, and synergistically serving as a catalytic union to boost the de/hydrogenation reactions of MgH2. Besides, the FeCoNiCrMo nanosheets had close contact with MgH2, providing numerous non-homogeneous activation sites and diffusion channels for the rapid transfer of hydrogen, thus obtaining a superior catalytic effect.
Research Article
Intelligent method to experimentally identify the fracture mechanism of red sandstone
Zida Liu, Diyuan Li, Quanqi Zhu, Chenxi Zhang, Jinyin Ma, and Junjie Zhao
  Available online 6 May 2023, https://doi.org/10.1007/s12613-023-2668-8
[FullText HTML](178) [PDF 8382KB](24) SpringerLink
Tensile and shear fractures are significant mechanisms for rock failure. Understanding the fractures that occur in rock can reveal rock failure mechanisms. Scanning electron microscopy (SEM) has been widely used to analyze tensile and shear fractures of rock on a mesoscopic scale. To quantify tensile and shear fractures, this study proposed an innovative method composed of SEM images and deep learning techniques to identify tensile and shear fractures in red sandstone. First, direct tensile and preset angle shear tests were performed for red sandstone to produce representative tensile and shear fracture surfaces, which were then observed by SEM. Second, these obtained SEM images were applied to develop deep learning models (AlexNet, VGG13, and SqueezeNet). Model evaluation showed that VGG13 was the best model, with a testing accuracy of 0.985. Third, the features of tensile and shear fractures of red sandstone learned by VGG13 were analyzed by the integrated gradient algorithm. VGG13 was then implemented to identify the distribution and proportion of tensile and shear fractures on the failure surfaces of rock fragments caused by uniaxial compression and Brazilian splitting tests. Results demonstrated the model feasibility and suggested that the proposed method can reveal rock failure mechanisms.
Research Article
Phase-field simulation of lack-of-fusion defect and grain growth during laser powder bed fusion of Inconel 718
Miaomiao Chen, Renhai Shi, Zhuangzhuang Liu, Yinghui Li, Qiang Du, Yuhong Zhao, and Jianxin Xie
  Available online 26 April 2023, https://doi.org/10.1007/s12613-023-2664-z
[FullText HTML](234) [PDF 4108KB](31) SpringerLink
The anisotropy of the structure and properties caused by the strong epitaxial growth of grains during laser powder bed fusion (L-PBF) significantly affects the mechanical performance of Inconel 718 alloy components such as turbine disks. The defects (lack-of-fusion, LoF) in components processed via L-PBF are detrimental to the strength of the alloy. The purpose of this study is to investigate the effect of laser scanning parameters on the epitaxial grain growth and LoF formation in order to obtain the parameter space in which the microstructure is refined and LoF defect is suppressed. The temperature field of the molten pool and the epitaxial grain growth are simulated using a multiscale model combining the finite element method with the phase-field method. The LoF model is proposed to predict the formation of LoF defects resulting from insufficient melting during L-PBF. Defect mitigation and grain-structure control during L-PBF can be realized simultaneously in the model. The simulation shows the input laser energy density for the as-deposited structure with fine grains and without LoF defects varied from 55.0–62.5 J·mm–3 when the interlayer rotation angle was 0o–90o. The optimized process parameters (laser power of 280 W, scanning speed of 1160 mm·s–1, and rotation angle of 67o) were computationally screened. In these conditions, the average grain size was 7.0 μm, and the ultimate tensile strength and yield strength at room temperature were (1111 ± 3) MPa and (820 ± 7) MPa, respectively, which is 8.8% and 10.5% higher than those of reported. The results indicating the proposed multiscale computational approach for predicting grain growth and LoF defects could allow simultaneous grain-structure control and defect mitigation during L-PBF.
Research Article
Separation of galena and chalcopyrite using the difference in their surface acid corrosion characteristics
Haiyun Xie, Jialing Chen, Pei Zhang, Likun Gao, Dianwen Liu, and Luzheng Chen
  Available online 18 April 2023, https://doi.org/10.1007/s12613-023-2654-1
[FullText HTML](125) [PDF 2956KB](15) SpringerLink
Galena (PbS) and chalcopyrite (CuFeS2) are sulfide minerals that exhibit good floatability characteristics. Thus, efficiently separating them via common flotation is challenging. Herein, a new method of surface sulfuric acid corrosion in conjunction with flotation separation was proposed, and the efficient separation of galena and chalcopyrite was successfully realized. Contact angle test results showed a substantial decrease in surface contact angle and a selective inhibition of surface floatability for corroded galena. Meanwhile, the contact angle and floatability of corroded chalcopyrite remained almost unaffected. Scanning electron microscope results confirmed that sulfuric acid corrosion led to the formation of a dense oxide layer on the galena surface, whereas the chalcopyrite surface remained unaltered. X-ray photoelectron spectroscopy results showed that the chemical state of S2− on the surface of corroded galena was oxidized to \begin{document}$ \;{\mathrm{S}\mathrm{O}}_{4}^{2-} $\end{document}. A layer of hydrophilic PbSO4 was formed on the surface, leading to a sharp decrease in galena floatability. Meanwhile, new hydrophobic CuS2, CuS, and Cu1−xFe1−yS2−z species exhibiting good floatability were generated on the chalcopyrite surface. Finally, theoretical analysis results were further verified by corrosion–flotation separation experiments. The galena–chalcopyrite mixture was completely separated via flotation separation under appropriate corrosion acidity, corrosion temperature, and corrosion time. A novel approach has been outlined in this study, providing potential applications in the efficient separation of refractory copper–lead sulfide ore.
Research Article
Technical factors affecting the performance of anion exchange membrane water electrolyzer
Xun Zhang, Yakang Li, Wei Zhao, Jiaxin Guo, Pengfei Yin, and Tao Ling
  Available online 8 April 2023, https://doi.org/10.1007/s12613-023-2648-z
[FullText HTML](344) [PDF 3602KB](61) SpringerLink
Anion exchange membrane (AEM) electrolysis is a promising membrane-based green hydrogen production technology. However, AEM electrolysis still remains in its infancy, and the performance of AEM electrolyzers is far behind that of well-developed alkaline and proton exchange membrane electrolyzers. Therefore, breaking through the technical barriers of AEM electrolyzers is critical. On the basis of the analysis of the electrochemical performance tested in a single cell, electrochemical impedance spectroscopy, and the number of active sites, we evaluated the main technical factors that affect AEM electrolyzers. These factors included catalyst layer manufacturing (e.g., catalyst, carbon black, and anionic ionomer) loadings, membrane electrode assembly, and testing conditions (e.g., the KOH concentration in the electrolyte, electrolyte feeding mode, and operating temperature). The underlying mechanisms of the effects of these factors on AEM electrolyzer performance were also revealed. The irreversible voltage loss in the AEM electrolyzer was concluded to be mainly associated with the kinetics of the electrode reaction and the transport of electrons, ions, and gas-phase products involved in electrolysis. Based on the study results, the performance and stability of AEM electrolyzers were significantly improved.
Invited Review
Hydrometallurgical detoxification and recycling of electric arc furnace dust
Yang Xue, Xiaoming Liu, Chunbao (Charles) Xu, and Yonghui Han
  Available online 30 March 2023, https://doi.org/10.1007/s12613-023-2637-2
[FullText HTML](139) [PDF 4006KB](20) SpringerLink
Electric arc furnace dust (EAFD) is a hazardous waste but can also be a potential secondary resource for valuable metals, such as Zn and Fe. Given the increased awareness of carbon emission reduction, energy conservation, and environmental protection, hydrometallurgical technologies for the detoxification and resource use of EAFD have been developing rapidly. This work summarizes the generation mechanisms, compositions, and characteristics of EAFD and presents a critical review of various hydrometallurgical treatment methods for EAFD, e.g., acid leaching, alkaline leaching, salt leaching, and pretreatment–enhanced leaching methods. Simultaneously, the phase transformation mechanisms of zinc-containing components in acid and alkali solutions and pretreatment processes are expounded. Finally, two novel combined methods, i.e., oxygen pressure sulfuric acid leaching combined with composite catalyst preparation, and synergistic roasting of EAFD and municipal solid waste incineration fly ash combined with alkaline leaching, are proposed, which can provide future development directions to completely recycling EAFD by recovering valuable metals and using zinc residue.
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Editorial for special issue on renewable energy conversion, utilization and storage
Qipeng Lu, Zhihong Du, Jie Wang, Wenbin Cao, and Hailei Zhao
2023, vol. 30, no. 10, pp. 1855-1858. https://doi.org/10.1007/s12613-023-2746-y
[FullText HTML](21) [PDF 697KB](0) SpringerLink
Research Article
Realizing high-performance Na3V2(PO4)2O2F cathode for sodium-ion batteries via Nb-doping
Jie Wang, Yifeng Yuan, Xianhui Rao, Min’an Yang, Doudou Wang, Ailing Zhang, Yan Chen, Zhaolin Li, and Hailei Zhao
2023, vol. 30, no. 10, pp. 1859-1867. https://doi.org/10.1007/s12613-023-2666-x
[FullText HTML](206) [PDF 3981KB](13) SpringerLink
Na3V2(PO4)2O2F (NVPOF) has received considerable interest as a promising cathode material for sodium-ion batteries because of its high working voltage and good structural/thermal stability. However, the sluggish electrode reaction resulting from its low intrinsic electronic conductivity significantly restricts its electrochemical performance and thus its practical application. Herein, Nb-doped Na3V2−xNbx(PO4)2O2F/graphene (rGO) composites (x = 0, 0.05, 0.1) were prepared using a solvothermal method followed by calcination. Compared to the un-doped NVPOF/rGO, doping V-site with high-valence Nb element (Nb5+) (Na3V1.95Nb0.05(PO4)2O2F/rGO (NVN05POF/rGO)) can result in the generated V4+/V3+ mixed-valence, ensuring the lower bandgap and thus the increased intrinsic electronic conductivity. Besides, the expanded lattice space favors the Na+ migration. With the structure feature where NVN05POF particles are attached to the rGO sheets, the electrode reaction kinetics is further accelerated owing to the well-constructed electron conductive network. As a consequence, the as-prepared NVN05POF/rGO sample exhibits a high specific capacity of ~72 mAh·g−1 at 10C (capacity retention of 65.2% (vs. 0.5C)) and excellent long-term cycling stability with the capacity fading rate of ~0.099% per cycle in 500 cycles at 5C.
Research Article
Uniform nanoplating of metallic magnesium film on titanium dioxide nanotubes as a skeleton for reversible Na metal anode
Jinshan Wang, Feng Li, Si Zhao, Lituo Zheng, Yiyin Huang, and Zhensheng Hong
2023, vol. 30, no. 10, pp. 1868-1877. https://doi.org/10.1007/s12613-023-2685-7
[FullText HTML](128) [PDF 22306KB](13) SpringerLink
To meet the low-cost concept advocated by the sodium metal anode, this paper reports the use of a pulsed electrodeposition technology with ionic liquids as electrolytes to achieve uniform nanoplating of metallic magnesium films at around 20 nm on spaced titanium dioxide (TiO2) nanotubes (STNA-Mg). First, the sodiophilic magnesium metal coating can effectively reduce the nucleation overpotential of sodium metal. Moreover, three-dimensional STNA can limit the volume expansion during sodium metal plating and stripping to achieve the ultrastable deposition and stripping of sodium metals with a high Coulombic efficiency of up to 99.5% and a small voltage polarization of 5 mV in symmetric Na||Na batteries. In addition, the comparative study of sodium metal deposition behavior of STNA-Mg and STNA-Cu prepared by the same route further confirmed the advantage of magnesium metal to guide sodium metal growth. Finally, the prepared STNA-Mg–Na metal anode and commercial sodium vanadium phosphate cathode were assembled into a full cell, delivering a discharge capacity of 110.2 mAh·g−1 with a retention rate of 95.6% after 110 cycles at 1C rate.
Research Article
Efficient utilization of glass fiber separator for low-cost sodium-ion batteries
Xiaohang Ma, Zhijie Chen, Tianwen Zhang, Xueqian Zhang, Yuan Ma, Yanqing Guo, Yiyong Wei, Mengyuan Ge, Zhiguo Hou, and Zhenfa Zi
2023, vol. 30, no. 10, pp. 1878-1886. https://doi.org/10.1007/s12613-023-2691-9
[FullText HTML](139) [PDF 3947KB](21) SpringerLink
The separator is a key component of sodium-ion battery, which greatly affects the electrochemical performances and safety characteristics of the battery. Conventional glass fiber separator cannot meet the requirements of large-scale application because of high cost and poor mechanical properties. Herein, the novel composite separators are prepared by a simple slurry sieving process using glass fiber separator scraps and ordinary qualitative filter paper as raw materials. As the composite mass ratio is 1:1, the composite separator has excellent comprehensive properties, including tensile strength of 15.8 MPa, porosity of 74.3%, ionic conductivity of 1.57 × 10−3 S·cm−1 and thermal stability at 210°C. The assembled sodium-ion battery shows superior cycling performance (capacity retention of 94.1% after 500 cycles at 1C) and rate capacity (retention rate of 87.3% at 10C), and it maintains fine interface stability. The above results provide some new ideas for the separator design of high-performance and low-cost sodium-ion batteries.
Research Article
Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol–gel and electrospinning methods: Effect of Na-excess content
Thongsuk Sichumsaeng, Atchara Chinnakorn, Ornuma Kalawa, Jintara Padchasri, Pinit Kidkhunthod, and Santi Maensiri
2023, vol. 30, no. 10, pp. 1887-1896. https://doi.org/10.1007/s12613-023-2702-x
[FullText HTML](101) [PDF 10442KB](17) SpringerLink
The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide (NNMO) prepared by sol–gel and electrospinning methods is investigated in this paper. X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss, while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content. Compared with the sol–gel method, the secondary phase of NiO is more suppressed by using the electrospinning method, which is further confirmed by field emission scanning electron microscope images. N2 adsorption–desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents. The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are +2 and +4, respectively. For the electrochemical properties, superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%. The highest specific capacitance is 36.07 F·g−1 at 0.1 A·g−1 in the NNMO electrode prepared by using the sol–gel method. By contrast, the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100% after charge–discharge measurements for 300 cycles. Therefore, controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.
Research Article
A gel polymer electrolyte with IL@UiO-66-NH2 as fillers for high-performance all-solid-state lithium metal batteries
Tao Wei, Qi Zhang, Sijia Wang, Mengting Wang, Ye Liu, Cheng Sun, Yanyan Zhou, Qing Huang, Xiangyun Qiu, and Fang Tian
2023, vol. 30, no. 10, pp. 1897-1905. https://doi.org/10.1007/s12613-023-2639-0
[FullText HTML](550) [PDF 3371KB](40) SpringerLink
All solid-state electrolytes have the advantages of good mechanical and thermal properties for safer energy storage, but their energy density has been limited by low ionic conductivity and large interfacial resistance caused by the poor Li+ transport kinetics due to the solid–solid contacts between the electrodes and the solid-state electrolytes. Herein, a novel gel polymer electrolyte (UPP-5) composed of ionic liquid incorporated metal-organic frameworks nanoparticles (IL@MOFs) is designed, it exhibits satisfying electrochemical performances, consisting of an excellent electrochemical stability window (5.5 V) and an improved Li+ transference number of 0.52. Moreover, the Li/UPP-5/LiFePO4 full cells present an ultra-stable cycling performance at 0.2C for over 100 cycles almost without any decay in capacities. This study might provide new insight to create an effective Li+ conductive network for the development of all-solid-state lithium-ion batteries.
Research Article
Mechanically mixing copper and silver into self-supporting electrocatalyst for hydrogen evolution
Xinzhuo Hu, Zhe Liu, Yi Feng, Yongfeng Zhang, Zhe Li, Zhennan Chen, Jing Mao, Jing Yang, Hui Liu, Pengfei Yin, Lei Cui, and Xiwen Du
2023, vol. 30, no. 10, pp. 1906-1913. https://doi.org/10.1007/s12613-023-2695-5
[FullText HTML](146) [PDF 3302KB](16) SpringerLink
Commercial hydrogen production involves the development of efficient hydrogen evolution reaction catalysts. Herein, we adopted a friction stir processing (FSP) technique to mix immiscible metals homogenously and obtain a self-supporting copper–silver (CuAg) catalyst. The gust of Ag atoms with larger atomic sizes caused a tensile strain in the Cu matrix. Meanwhile, the chemical-potential difference induced electron transfer from Cu to Ag, and the two factors jointly led to the upshift of Cu d-band and improved the catalytic activity. Consequently, the CuAg electrode exhibited a high turnover frequency (12 times that of pure Cu), a low overpotential at high current density (superior to platinum foil), and high durability (1.57% decay over 180 h). Our work demonstrates that FSP is a powerful method for preparing self-supporting catalysts of immiscible alloys with high catalytic performance.
Research Article
Metal-organic framework derived NiFe2O4/FeNi3@C composite for efficient electrocatalytic oxygen evolution reaction
Fangna Dai, Zhifei Wang, Huakai Xu, Chuanhai Jiang, Yuguo Ouyang, Chunyu Lu, Yuan Jing, Shiwei Yao, and Xiaofei Wei
2023, vol. 30, no. 10, pp. 1914-1921. https://doi.org/10.1007/s12613-023-2721-7
[FullText HTML](156) [PDF 2431KB](25) SpringerLink
Reducing the cost and improving the electrocatalytic activity are the key to developing high efficiency electrocatalysts for oxygen evolution reaction (OER). Here, bimetallic NiFe-based metal-organic framework (MOF) was prepared by solvothermal method, and then used as precursor to prepare NiFe-based MOF-derived materials by pyrolysis. The effects of different metal ratios and pyrolysis temperatures on the sample structure and OER electrocatalytic performance were investigated and compared. The experimental results showed that when the metal molar ratio was Fe : Ni = 1:5 and the pyrolysis temperature was 450°C, the sample (FeNi5-MOF-450) exhibits a composite structure of NiFe2O4/FeNi3/C and owns the superior electrocatalytic activity in OER. When the current density is 100 mA·cm−2, the overpotential of the sample was 377 mV with Tafel slope of 56.2 mV·dec−1, which indicates that FeNi5-MOF-450 exhibits superior electrocatalytic performance than the commercial RuO2. Moreover, the long-term stability of FeNi5-MOF-450 further promotes its development in OER. This work demonstrated that the regulatory methods such as component optimization can effectively improve the OER catalytic performance of NiFe-based MOF-derived materials.
Research Article
Corrosion engineering on AlCoCrFeNi high-entropy alloys toward highly efficient electrocatalysts for the oxygen evolution of alkaline seawater
Zhibin Chen, Kang Huang, Bowei Zhang, Jiuyang Xia, Junsheng Wu, Zequn Zhang, and Yizhong Huang
2023, vol. 30, no. 10, pp. 1922-1932. https://doi.org/10.1007/s12613-023-2624-7
[FullText HTML](202) [PDF 1763KB](24) SpringerLink
Seawater splitting is a prospective approach to yield renewable and sustainable hydrogen energy. Complex preparation processes and poor repeatability are currently considered to be an insuperable impediment to the promotion of the large-scale production and application of electrocatalysts. Avoiding the use of intricate instruments, corrosion engineering is an intriguing strategy to reduce the cost and presents considerable potential for electrodes with catalytic performance. An anode comprising quinary AlCoCrFeNi layered double hydroxides uniformly decorated on an AlCoCrFeNi high-entropy alloy is proposed in this paper via a one-step corrosion engineering method, which directly serves as a remarkably active catalyst for boosting the oxygen evolution reaction (OER) in alkaline seawater. Notably, the best-performing catalyst exhibited oxygen evolution reaction activity with overpotential values of 272.3 and 332 mV to achieve the current densities of 10 and 100 mA·cm−2, respectively. The failure mechanism of the obtained catalyst was identified for advancing the development of multicomponent catalysts.
Invited Review
Recent advances and influencing parameters in developing electrode materials for symmetrical solid oxide fuel cells
Wan Nor Anasuhah Wan Yusoff, Nurul Akidah Baharuddin, Mahendra Rao Somalu, Andanastuti Muchtar, Nigel P. Brandon, and Huiqing Fan
2023, vol. 30, no. 10, pp. 1933-1956. https://doi.org/10.1007/s12613-023-2694-6
[FullText HTML](255) [PDF 2039KB](17) SpringerLink
This article delivers a robust overview of potential electrode materials for use in symmetrical solid oxide fuel cells (S-SOFCs), a relatively new SOFC technology. To this end, this article provides a comprehensive review of recent advances and progress in electrode materials for S-SOFC, discussing both the selection of materials and the challenges that come with making that choice. This article discussed the relevant factors involved in developing electrodes with nano/microstructure. Nanocomposites, e.g., non-cobalt and lithiated materials, are only a few of the electrode types now being researched. Furthermore, the phase structure and microstructure of the produced materials are heavily influenced by the synthesis procedure. Insights into the possibilities and difficulties of the material are discussed. To achieve the desired microstructural features, this article focuses on a synthesis technique that is either the most recent or a better iteration of an existing process. The portion of this analysis that addresses the risks associated with manufacturing and the challenges posed by materials when fabricating S-SOFCs is the most critical. This article also provides important and useful recommendations for the strategic design of electrode materials researchers.
Research Article
High-performance triboelectric nanogenerator based on ZrB2/polydimethylsiloxane for metal corrosion protection
Xiucai Wang, Naijian Hu, Jia Yang, Jianwen Chen, Xinmei Yu, Wenbo Zhu, Chaochao Zhao, Ting Wang, and Min Chen
2023, vol. 30, no. 10, pp. 1957-1964. https://doi.org/10.1007/s12613-023-2626-5
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Metal corrosion causes billions of dollars of economic losses yearly. As a smart and new energy-harvesting device, triboelectric nanogenerators (TENGs) can convert almost all mechanical energy into electricity, which leads to great prospects in metal corrosion prevention and cathodic protection. In this work, flexible TENGs were designed to use the energy harvested by flexible polydimethylsiloxane (PDMS) films with ZrB2 nanoparticles and effectively improve the dielectric constant by incorporating ZrB2. The open-circuit voltage and short-circuit current were 264 V and 22.9 µA, respectively, and the power density of the TENGs reached 6 W·m−2. Furthermore, a self-powered anti-corrosion system was designed by the rectifier circuit integrated with TENGs, and the open-circuit potential (OCP) and Tafel curves showed that the system had an excellent anti-corrosion effect on carbon steel. Thus, the system has broad application prospects in fields such as metal cultural relics, ocean engineering, and industry.
Research Article
Propylamine hydrobromide passivated tin-based perovskites to efficient solar cells
Xiaomeng Li, Pengcheng Jia, Fanwen Meng, Xingyu Zhang, Yang Tang, Bo Song, Chang Gao, Liang Qin, Feng Teng, and Yanbing Hou
2023, vol. 30, no. 10, pp. 1965-1972. https://doi.org/10.1007/s12613-023-2604-y
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The development of tin-based devices with low toxicity is critical for the commercial viability of perovskite solar cells. However, because tin halide is a stronger Lewis acid, its crystallization rate is extremely fast, resulting in the formation of numerous defects that affect the device performance of tin-based perovskite solar cells. Herein, propylamine hydrobromide (PABr) was added to the perovskite precursor solution as an additive to passivate defects and fabricate more uniform and dense perovskite films. Because propylamine cations are too large to enter the perovskite lattices, they only exist at the grain boundary to passivate surface defects and promote crystal growth in a preferred orientation. The PABr additive raises the average short-circuit current density from 19.45 to 25.47 mA·cm−2 by reducing carrier recombination induced by defects. Furthermore, the device’s long-term illumination stability is improved after optimization, and the hysteresis effect is negligible. The addition of PABr results in a power conversion efficiency of 9.35%.
Research Article
Enhanced energy-absorbing and sound-absorbing capability of functionally graded and helicoidal lattice structures with triply periodic minimal surfaces
Miao Zhao, Zhendong Li, Jun Wei Chua, Chong Heng Lim, and Xinwei Li
2023, vol. 30, no. 10, pp. 1973-1985. https://doi.org/10.1007/s12613-023-2684-8
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Lattice structures have drawn much attention in engineering applications due to their lightweight and multi-functional properties. In this work, a mathematical design approach for functionally graded (FG) and helicoidal lattice structures with triply periodic minimal surfaces is proposed. Four types of lattice structures including uniform, helicoidal, FG, and combined FG and helicoidal are fabricated by the additive manufacturing technology. The deformation behaviors, mechanical properties, energy absorption, and acoustic properties of lattice samples are thoroughly investigated. The load-bearing capability of helicoidal lattice samples is gradually improved in the plateau stage, leading to the plateau stress and total energy absorption improved by over 26.9% and 21.2% compared to the uniform sample, respectively. This phenomenon was attributed to the helicoidal design reduces the gap in unit cells and enhances fracture resistance. For acoustic properties, the design of helicoidal reduces the resonance frequency and improves the peak of absorption coefficient, while the FG design mainly influences the peak of absorption coefficient. Across broad range of frequency from 1000 to 6300 Hz, the maximum value of absorption coefficient is improved by 18.6%–30%, and the number of points higher than 0.6 increased by 55.2%–61.7% by combining the FG and helicoidal designs. This study provides a novel strategy to simultaneously improve energy absorption and sound absorption properties by controlling the internal architecture of lattice structures.
Invited Review
Crystalline framework nanosheets as platforms for functional materials
Yun Fan, Cheng Chen, Siyao Zhang, Suoying Zhang, Fengwei Huo, and Weina Zhang
2023, vol. 30, no. 10, pp. 1986-2005. https://doi.org/10.1007/s12613-023-2696-4
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The integration of organic and inorganic materials has been widely used in various applications to generate novel functional nanomaterials characterized by unique properties. Functional crystalline framework nanosheets and their synergistic effects have been studied recently for possessing the advantages of functional species as well as crystalline framework nanosheets. Hence, we have focused on the preparation methods and applications of functional crystalline framework nanosheets in this review. We introduced crystalline framework nanosheets and discussed the importance of integrating functional species with nanosheets to form functional crystalline framework nanosheets. Then, two aspects of the preparation methods of functional crystalline framework nanosheets were reviewed: in situ synthesis and post-synthesis modification. Subsequently, we discussed the properties of the crystalline framework nanosheets combined with various functional species and summarized their applications in catalysis, sensing, separation, and energy storage. Finally, we have shared our insights on the challenges of functional crystalline framework nanosheets, hoping to contribute to the knowledge base for optimizing the preparation methods, expanding categories, improving stability, and exploring potential applications.
Research Article
Theoretical study on the morphology of cobalt nanoparticles modulated by alkali metal promoters
Xiaobin Geng, Hui Yang, Wenping Guo, Xiaotong Liu, Tao Yang, and Jinjia Liu
2023, vol. 30, no. 10, pp. 2006-2013. https://doi.org/10.1007/s12613-023-2634-5
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Cobalt nanoparticles (NPs) catalysts are extensively used in heterogeneous catalytic reactions, and the addition of alkali metal promoters is a common method to modulate the catalytic performance because the catalyst’s surface structures and morphologies are sensitive to the addition of promoters. However, the underlying modulation trend remains unclear. Herein, the adsorption of alkali metal promoters (Na and K) on the surfaces of face-centered-cubic (FCC) and hexagonal-closest packed (HCP) polymorphous cobalt was systematically investigated using density functional theory. Furthermore, the effect of alkali promoters on surface energies and nanoparticle morphologies was revealed on the basis of Wulff theory. For FCC-Co, the exposed area of the (111) facet in the nanoparticle increases with the adsorption coverage of alkali metal oxide. Meanwhile, the (311), (110), and (100) facets would disappear under the higher adsorption coverage of alkali metals. For HCP-Co, the Wulff morphology is dominated by the (0001) and (\begin{document}$ 10\bar{1}1 $\end{document}) facets and is independent of the alkali metal adsorption coverage. This work provides insights into morphology modulation by alkali metal promoters for the rational design and synthesis of cobalt-based nanomaterials with desired facets and morphologies.
Research Article
Speeding up the prediction of C–O cleavage through bond valence and charge on iron carbides
Yurong He, Kuan Lu, Jinjia Liu, Xinhua Gao, Xiaotong Liu, Yongwang Li, Chunfang Huo, James P. Lewis, Xiaodong Wen, and Ning Li
2023, vol. 30, no. 10, pp. 2014-2024. https://doi.org/10.1007/s12613-023-2612-y
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The activation of CO on iron-based materials is a key elementary reaction for many chemical processes. We investigate CO adsorption and dissociation on a series of Fe, Fe3C, Fe5C2, and Fe2C catalysts through density functional theory calculations. We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites. The activation of CO is dependent on the local coordination of the molecule to the surface and on the bulk phase of the underlying catalyst. The bulk properties and the different local bonding environments lead to varying interactions between the adsorbed CO and the surface and thus yielding different activation levels of the C–O bond. We also examine the prediction of CO adsorption on different types of Fe-based catalysts by machine learning through linear regression models. We combine the features originating from surfaces and bulk phases to enhance the prediction of the activation energies and perform eight different linear regressions utilizing the feature engineering of polynomial representations. Among them, a ridge linear regression model with 2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.
Research Article
Introducing oxygen vacancies in TiO2 lattice through trivalent iron to enhance the photocatalytic removal of indoor NO
Peng Sun, Sumei Han, Jinhua Liu, Jingjing Zhang, Shuo Yang, Faguo Wang, Wenxiu Liu, Shu Yin, Zhanwu Ning, and Wenbin Cao
2023, vol. 30, no. 10, pp. 2025-2035. https://doi.org/10.1007/s12613-023-2611-z
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The synthesis of oxygen vacancies (OVs)-modified TiO2 under mild conditions is attractive. In this work, OVs were easily introduced in TiO2 lattice during the hydrothermal doping process of trivalent iron ions. Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO2 (Fe–TiO2). The OVs formation energy in Fe–TiO2 (1.12 eV) was only 23.6% of that in TiO2 (4.74 eV), explaining why Fe3+ doping could introduce OVs in the TiO2 lattice. The calculation results also indicated that impurity states introduced by Fe3+ and OVs enhanced the light absorption activity of TiO2. Additionally, charge carrier transport was investigated through the carrier lifetime and relative mass. The carrier lifetime of Fe–TiO2 (4.00, 4.10, and 3.34 ns for 1at%, 2at%, and 3at% doping contents, respectively) was longer than that of undoped TiO2 (3.22 ns), indicating that Fe3+ and OVs could promote charge carrier separation, which can be attributed to the larger relative effective mass of electrons and holes. Herein, Fe–TiO2 has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.
Research Article
Synthesis of crystal-phase and color tunable mixed anion co-doped titanium oxides and their controllable photocatalytic activity
Jingdi Cao, Takuya Hhasegawa, Yusuke Asakura, Akira Yamakata, Peng Sun, Wenbin Cao, and Shu Yin
2023, vol. 30, no. 10, pp. 2036-2043. https://doi.org/10.1007/s12613-022-2573-6
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B and N mixed anions co-doped titania with various crystal phases such as anatase, brookite, and rutile were successfully synthesized by a hydrothermal synthesis followed by heat treatment in an ammonia gas atmosphere at 550–650°C (denoted as BN-Ana_x, BN-Bro_x, and BN-Rut_x, x is the treatment temperature). The colors of as-prepared BN-Ana, BN-Bro, and BN-Rut are red, yellow-green, and cyan-green, respectively. The color changing mechanism of titania was related to their various band gap structure and the existence of B–N bonding. The nitridation temperature exhibits effective color changing compared to that of nitridation time. The different phases of the mixed anion co-doped titania possess different photocatalytic deNOx activity. The BN-Ana and BN-Rut show poor photocatalytic deNOx activity, while the BN-Bro shows excellent photocatalytic deNOx activity, better than that of standard titania photocatalyst Degussa P25. The colorful titania with low-photocatalytic activity is heavy metal elements free, indicating their possible applications as nontoxic color pigments or novel cosmetic raw materials.
Research Article
Synergically enhanced piezocatalysis performance of eco-friendly (K0.52Na0.48)NbO3 through ferroelectric polarization and defects
Min Zhou, Laijun Liang, Dingze Lu, Xiaomei Lu, Zheng Wang, Fengzhen Huang, Pengfei Cheng, Dongdong Liu, Mengqi Tian, Qiuping Wang, and Yunjie Zhang
2023, vol. 30, no. 10, pp. 2044-2054. https://doi.org/10.1007/s12613-023-2671-0
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Piezocatalysis has attracted unprecedented research interest as a newly emerging catalysis technology. However, the inherent insulating property of ferroelectric materials ultimately leads to the poor vibration–electricity conversion ability. Herein, this work reports the (K0.52Na0.48)NbO3 ferroelectric ceramics (KNNFCx), for which the FeCo modification strategy is proposed. The substitution of the moderate amount of FeCo (x = 0.015) at Nb site not only optimizes ferroelectricity but also produces beneficial defects, notably increasing Rhodamine B water purification efficiency to 95%. The pinning effect of monovalent oxygen vacancies on ferroelectric domains is responsible for the excellent ferroelectric polarization of KNNFC0.015 through the generation of an internal field to promote charge carriers separation and reduce nonradiative recombination. Importantly, the accompanying electron carriers can easily move to the material surface and participate in redox reactions because they have low activation energy. Therefore, ferroelectric polarization and defects play synergetic roles in enhancing piezocatalytic performance.