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Research Article
Preparation and characterization of ceramic materials with low thermal conductivity and high strength using high-calcium fly ash
Mana Rodchom, Panida Wimuktiwan, Kanit Soongprasit, Duangduen Atong, and Supawan Vichaphund
Available online 22 October 2021, https://doi.org/10.1007/s12613-021-2367-2
[Abstract](0) [PDF 1529KB](1)
Abstract:

In this research, high calcium-fly ash (HCFA) collected from the Mae Moh electricity generating plant in Thailand was utilized as a raw material for ceramic production. The main compositions of HCFA characterized by XRF mainly consisted of 28.55 wt% SiO2, 16.06 wt% Al2O3, 23.40 wt% CaO and 17.03 wt% Fe2O3. Due to high proportion of calcareous and ferruginous contents, HCFA was used for replacing the potash feldspar in amounts of 10-40 wt%. The influence of substituting high-calcium fly ash (0-40 wt%) and sintering temperatures (1000-1200 οC) on physical, mechanical, and thermal properties of ceramic-based materials was investigated. The results showed that the incorporation of HCFA in appropriate amounts could enhance the densification and the strength as well as reduce the thermal conductivity of ceramic samples. High proportion of calcareous and ferruginous constituents in fly ash promoted the vitrification behavior of ceramic samples. As a result, the densification was enhanced by liquid phase formation at optimum fly ash content and sintering temperature. In addition, these components also facilitated a more abundant mullite formation and consequently improved flexural strength of the ceramic samples. The optimum ceramic properties were achieved with adding fly ash content between 10-30 wt% sintered at 1150-1200 οC. At 1200 οC, the maximum flexural strength of ceramic-FA samples with adding fly ash 10-30wt% (PSW-FA(10)-(30)) was obtained in the range of 92.25-94.71 MPa when the water absorption reached almost zero (0.03%). In terms of thermal insulation materials, the increase in fly ash addition had a positively effect on the thermal conductivity, due to the higher levels of porosity created by gas evolving from the inorganic decomposition reactions inside the ceramic-FA samples. The addition of 20-40 wt% high-calcium fly ash in ceramic samples sintered at 1150 οC reduced the thermal conductivity to 14.78-49.25%, while maintaining acceptable flexural strength values (~ 45.67-87.62 MPa). Based on these promising mechanical and thermal characteristics, it is feasible to utilize this high-calcium fly ash as an alternative raw material in clay compositions for manufacturing of ceramic tiles

Research Article
The role of Al substitution on the phase evolution in synthesized Mg2Cu nanoparticles: An insight from X-ray diffraction analysis
Elham Mohseni-Sohi and Farshid Kashani Bozorg
Available online 22 October 2021, https://doi.org/10.1007/s12613-021-2368-1
[Abstract](0) [PDF 1549KB](1)
Abstract:

In this study, the effect of Mg replacement with Al on the discharge capacity of Mg2Cu powder mixture is investigated. The mixture of nanocrystalline powder is prepared via mechanical alloying (MA) technique with a high energy planetary ball mill. In addition, different moles of Al are substituted to Mg2Cu powder (0.05, 0.1, 0.15, 0.2, and 0.3). X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are used to analyze changes in structure, morphology, and grain size. The obtained powder is utilized as an anode in a nickel-metal hydride battery (Ni-MH). In the specimens with 0.05 M Al content, the orthorhombic structure of Mg2Cu is emerged after 5 hours milling. The results reveal that more than 0.2 M Al substitution leads to an appearance of MgCu2 peaks. Al substitution does not affect microstructure uniformity; however, it causes a decrease in crystalline size and lattice parameters. The SAD pattern elucidates that the electrode with the Mg1.9Al0.1Cu chemical composition and 20 hours milling has the maximum discharge capacity.

Research Article
Extraction of lithium from simulated pyrometallurgical slag of spent lithium-ion batteries by binary eutectic molten carbonates
Hui Dang, Zhidong Chang, Hualei Zhou, Sihang Ma, Min Li, and Jialing Xiang
Available online 16 October 2021, https://doi.org/10.1007/s12613-021-2366-3
[Abstract](19) [PDF 733KB](4)
Abstract:

Effectively extracting lithium from the pyrometallurgical slag of spent lithium-ion batteries at a relatively low temperature remains a great challenge. Herein, potassium carbonate/sodium carbonate (K2CO3/Na2CO3) which could form eutectic molten salts at 720°C were used as the roasting agents for extracting lithium from the pyrometallurgical slag. The lithium is successfully extracted from slag by K2CO3/Na2CO3 roasting followed by water leaching. According to the theoretical calculation results, lengths of Li-O bonds increase after adsorption of K+/Na+, resulting in easily release of Li+ from the lattice of LiAlSi2O6 after roasting with K2CO3/Na2CO3. Moreover, the TG-DSC results indicate that the eutectic phenomenon of K2CO3 and Na2CO3 is observed at 720°C and the reaction of slag and eutectic molten salts happens above 720°C. The X-ray diffraction results suggest that Li+ in slag is exchanged by K+ in K2CO3 which is accompanied by the formation of KAlSiO4, while Na2CO3 is mainly employed as a fluxing agent. The lithium extraction efficiency can reach 93.87% under the following optimal conditions: roasting temperature of 740°C, roasting time of 30 min, leaching temperature of 50°C, leaching time of 40 min and water/roasted samples mass ratio of 10:1. This work provides a new system for extracting lithium from the pyrometallurgical slag of spent lithium-ion batteries.

Research Article
Optimisation of alloy composition for highly-formable magnesium sheet
Zhuoran Zeng, Mingzhe Bian, Shiwei Xu, Weineng Tang, Chris Davies, Nick Birbilis, and Jianfeng Nie
Available online 15 October 2021, https://doi.org/10.1007/s12613-021-2365-4
[Abstract](23) [PDF 2229KB](2)
Abstract:

The effectiveness of Ca or Gd addition on ductility and formability of Mg-Zn-Zr based dilute alloys in deep drawing has not been systematically compared previously. In this study, formable Mg-Zn-Gd-Zr and Mg-Zn-Ca-Zr sheet alloys are produced by hot rolling. These sheets have similarly weakened basal texture, but the sheet of the Mg-Zn-Gd-Zr alloys has higher ductility and formability than that of Mg-Zn-Ca-Zr alloys. The combined addition of 0.2 wt.% Ca and 0.4 wt.% Gd to the Mg-1Zn-0.5Zr (wt.%) alloy leads to a Mg-1Zn-0.4Gd-0.2Ca-0.5Zr alloy that has even better ductility and its formability during deep drawing is comparable to the benchmark Al6016 sheet. An increase in Ca concentration from 0.2 wt.% to 0.5 wt.% leads to decreased sheet ductility and formability, predominantly due to grain boundary embrittlement.

Research Article
Hydration reactivity difference between dicalcium silicate and tricalcium silicate revealed from structural and Bader charge analysis
Chongchong Qi, Xinhang Xu, and Qiusong Chen
Available online 15 October 2021, https://doi.org/10.1007/s12613-021-2364-5
[Abstract](120) [PDF 1238KB](12)
Abstract:

Understanding the structural and electronic properties of calcium silicates is crucial to reveal their difference in hydration reactivity. Here we presented a comprehensive comparison of β-C2S and M3-C3S. The structural properties and Bader charge of β-C2S and M3-C3S in the unit cell, during surface reconstruction and after single water adsorption were investigated using density functional theory. We identified different types of atoms in β-C2S and M3-C3S considering the bonding characteristics and Bader charge. For β-C2S, Ca atoms were divided into two groups and O atoms into four groups. For M3-C3S, Ca atoms were divided into four groups, O atoms into four groups, and Si atoms into three groups. The valance electron distribution on the surface was more uniform than that of the unit cell, indicating some atoms became more reactive after surface relaxation. During water adsorption, electrons of β-C2S and M3-C3S were transferred from the surface to the adsorbed water molecules through position re-distribution and bond formation/breaking. And on this basis, we explored the reason why β-C2S and M3-C3S had activity differences. A type of O atom with special bond characteristics (no O-Si bonds) and high reactivity was observed in the unit cell of M3-C3S. As revealed by Bader charge analysis, the reactivity of Ca and O atoms was generally higher in M3-C3S than in β-C2S. The average valence electron number of Ca/O atoms in β-C2S was 6.437/7.550, while in M3-C3S it was 6.481/7.537. Moreover, the water molecules in M3-C3S gained more electrons at the surface compared to β-C2S. The average valence electron variation of H2O on β-C2S was 0.041 while that on M3-C3S was 0.226.

Research Article
Novel Cr3+-activated far-red emitting phosphors with β-Ca3(PO4)2-type structure for indoor plant cultivation
Fangyi Zhao, Zhen Song, and Quanlin Liu
Available online 12 October 2021, https://doi.org/10.1007/s12613-021-2363-6
[Abstract](48) [PDF 1099KB](3)
Abstract:

Cr3+-activated far-red and near-infrared phosphors have drawn much attention owing to their adjustable emission wavelengths and wide applications. Herein, we report a series of Cr3+-doped phosphors with β-Ca3(PO4)2-type structure, of which Ca9Ga(PO4)7:Cr3+ possesses the highest far-red emission intensity due to its strong absorption band of Cr3+ ion. Under the excitation of 440 nm, Ca9Ga(PO4)7:Cr3+ phosphors exhibit a broad emission band ranging from 650 to 850 nm peaking at 735 nm and superimpose two sharp lines centered at 690 and 698 nm. The optimal sample, Ca9Ga0.97(PO4)7:0.03Cr3+, has the internal quantum efficiency of 55.7%. The luminescence intensity of Ca9Ga0.97(PO4)7:0.03Cr3+ phosphor obtained at 423 K can maintain 68.5% of that at room temperature, demonstrating its outstanding luminescence thermal stability. Finally, a phosphor-conversion light-emitting diode was fabricated, indicating that Ca9Ga(PO4)7:Cr3+ phosphor has potential applications in the field of indoor plant cultivation.

Research Article
Optimize two-phase distribution of lithium-rich materials to stabilize structure and suppress voltage attenuation
Yang Yu, Jianling Li, Guimei Han, Zhe Yang, Jianjian Zhong, and Feiyu Kang
Available online 12 October 2021, https://doi.org/10.1007/s12613-021-2362-7
[Abstract](22) [PDF 1253KB](1)
Abstract:

Lithium-rich materials possess ultra-high specific capacity, but the redox of oxygen is not completely reversible, resulting in voltage attenuation and structural instability. A stepwise co-precipitation method is used for the first time in this paper to achieve the control of the two-phase distribution through controlling the distribution of transition metal elements and realize the modification of particle surface structure without the aid of heterologous ions. The results of characterization tests show that the content of LiMO2 phase inside the particles and the content of Li2MnO3 phase on the surface of the particles are successfully increased, and the surface induced formation of Li4Mn5O12 spinel phase or some disorderly ternary. The electrochemical performance of the modified sample is as follows: LR (pristine) shows specific discharge capacity of 72.7 mA h g-1 after 500 cycles at 1C, while GR (Modified sample) shows specific discharge capacity of 137.5 mA h g-1 at 1C, and the discharge mid-voltage of GR still remains above 3 V when cycling to 220 cycles at 1C (mid-voltage of LR remains above 3 V when cycling to 160 cycles at 1C). Therefore, deliberately regulating the local state of the two phases is an successful way to reinforced the material structure and inhibition the voltage attenuation.

Research Article
Self-assembled TiO2 hole blocking layers for efficient perovskite solar cells
Zhongbao Que, Liang Chu, Shuaibo Zhai, Yifei Feng, Chen Chen, Wei Liu, Ruiyuan Hu, Jing Hu, and Xing’ao Li
Available online 1 October 2021, https://doi.org/10.1007/s12613-021-2361-8
[Abstract](44) [PDF 864KB](4)
Abstract:

Self-assembled process for device functional layers is a simple, feasible and energy-saving strategy. In mesoporous PSCs, compact and scaffold TiO2 films generally function as the hole blocking and electron transporting layers, respectively. However, they are both typically generated through high-temperature annealing. Here, we deposited TiO2 compact films by a room-temperature self-assembled process, which were conducted as an effective hole blocking layer for perovskite solar cells. The thickness of TiO2 compact films can be easily controlled by the deposition time. By optimizing the TiO2 compact films (80 nm), the power conversion efficiency of mesoporous perovskite solar cells without and with hole conductor layers was up to 10.66% and 17.95%, respectively. Interestingly, an all-low-temperature planar perovskite solar cell with the self-assembled TiO2 layer achieve power conversion efficiency of 16.42%.

Research Article
Effect of heat treatment temperature on the structure and the formaldehyde removal performance of an interior wall tile
Ruqin Gao, Yingrui Huang, Enhui Wang, Xinmei Hou, Lu Pan, Guoting Li, and Bingtao Liu
Available online 30 September 2021, https://doi.org/10.1007/s12613-021-2359-2
[Abstract](36) [PDF 504KB](2)
Abstract:

A diatomite-based porous ceramic support has been prepared using solid-phase sintering and low-temperature calcination processes. Using diatomite as the main raw material, adding appropriate amount of tourmaline and sintering aids to the glaze, and combining different heat treatment temperatures of the glaze layer, tourmaline/diatomite-based interior wall tiles are prepared. The glaze layer under different heat treatment temperatures is characterized by thermogravimetric-differential thermal analysis, X-ray diffraction and scanning electron microscope. The influences of heat treatment temperature on the microscopic morphology and structure of the glaze layer are analyzed. Taking formaldehyde as the target degradation product, the effects of tourmaline/diatomite-based interior wall tiles on the removal of formaldehyde under different heat treatment temperatures of the glaze layer are investigated. The results show that with the increase of heat treatment temperature, the original pores of diatomite decreases, and the specific surface area, and the structure of tourmaline changes. The surface structure of the material is slightly damaged at 850℃, the strength is increased, and the removal effect of formaldehyde is better. In a 1 m3 environmental chamber, the formaldehyde removal rate reaches 73.6% in 300 min. When the temperature is increased to 950℃ and above, diatomite and the structure of tourmaline are destroyed, and the ability of the material to adsorb and degrade formaldehyde decreases.

Invited Review
A brief review on fabrication and application of porous materials from silicon-rich industrial solid waste
Chao Miao, Lixing Liang, Shumei Chen, Kaixuan Shang, Yi Zhang, and Jing Ouyang
Available online 30 September 2021, https://doi.org/10.1007/s12613-021-2360-9
[Abstract](56) [PDF 1482KB](12)
Abstract:

Porous materials have many promising prospects in such fields as sound insulation, heat barrier, vibration attenuation, and catalysts, due to their special porous structures. Most of the industrial solid wastes such as tailings, coal gangue, and fly ash are rich in silicon. As far as this is concerned. In this regard, the high silicon content makes it a potential raw material for the synthesis of silicon-based multi-porous materials such as zeolites, mesoporous silica, glass ceramics, geopolymer foams, etc. In this mini review, the representative silicon-rich industrial solid wastes (SRISW) are selected as the objects, which focused on the processing and application of silicon porous materials from the aspects of physical and chemical properties of SRISW. The transformation methods of preparing porous materials from silicon rich industrial solid wastes are summarized, and their research status in micro-, meso-, and macro-scale porous materials are concluded, respectively. Also the possible problems existing in the application of silicon-rich industrial solid wastes, and in the preparation of functional porous materials are analyzed, and their developing orientation is prospected. This review should provide a typical reference for the recycling and utilization of industrial solid wastes to develop some sustainable “green materials”.

Invited Review
Carbon materials: The burgeoning promise in electronics
Yuting Zheng, Junjun Wei, Jinlong Liu, Liangxian Chen, Kang An, Xiaotong Zhang, Haitao Ye, Xiaoping Ouyang, and Chengming Li
Available online 28 September 2021, https://doi.org/10.1007/s12613-021-2358-3
[Abstract](36) [PDF 1381KB](4)
Abstract:

Current electronic technology based on silicon is approaching to its physical and scientific limits. When facing the compulsory choice of finding a practicable way of potential material alternatives for next generation electronics, carbon-based devices showing numerous superiorities (e.g., fast speed, low power consumption and simple process) combining with the unique nature of versatile allotropes of carbon element are unfolding the promise of upcoming electronics revolution. Now it is the time that carbon electronics are greatly advancing with not only developed preparation but also sophisticated design. In this perspective, the representatives with various dimensions, e.g., carbon nanotubes, graphene, bulk diamond, together with extraordinary performance are reviewed. Based on these members of carbon materials family, the associated state-of-the-art devices and composite hybrid all-carbon structures are also emphasized to embody their inherent dominances in the electronics field. Advances of commercial production with improved cost-efficiency and material quality as well as devices design are ongoingly accelerating to the bright future, and it is virtually even impossible to keep up with this burgeoning situation.

Research Article
Mica stabilized polyethylene glycol composite phase change materials for thermal energy storage
Dongyao Zhang, Chuanchang Li, Niangzhi Lin, Baoshan Xie, and Jian Chen
Available online 24 September 2021, https://doi.org/10.1007/s12613-021-2357-4
[Abstract](94) [PDF 1086KB](13)
Abstract:

The mica was used as a supporting matrix for composite phase change materials (PCMs) because of its distinctive morphology and structure in this work. Mica-based composite PCMs were prepared by vacuum impregnation method using mica as supporting material and polyethylene glycol (PEG) as phase change material. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analysis confirmed that the addition of PEG had no effect on the crystal structure of mica, and no chemical reaction between PEG and mica during the vacuum impregnation process, and no new substance was formed. The maximum load of mica stabilized PEG is 46.24%, the phase change temperature of M400/PEG is 46.03°C, and the latent heat values of melting and cooling are 77.75 J g-1 and 77.73 J g-1, respectively. The thermal conductivity of M400/PEG is 2.4 times that of pure PEG. The thermal infrared images indicated that the thermal response of M400/PEG was improved compared with that of pure PEG. The leakage test confirmed that mica could stabilize PEG, and M400/PEG had great form-stabilized property. These results demonstrate that M400/PEG has potential in the field of building energy conservation.

Research Article
Influence of rare earth Ce on hot deformation behavior of as-cast Mn18Cr18N high nitrogen austenitic stainless steel
Yushuo Li, Yanwu Dong, Zhouhua Jiang, Qingfei Tang, Shuyang Du, and Zhiwen Hou
Available online 23 September 2021, https://doi.org/10.1007/s12613-021-2355-6
[Abstract](34) [PDF 2158KB](7)
Abstract:

In this paper, hot deformation behavior of Mn18Cr18N and Mn18Cr18N+Ce high nitrogen austenitic stainless steel at 1173~1473 K and 0.01~1 s-1 are investigated by thermal compression tests. Influence mechanism of Ce on the hot deformation behavior is analyzed by Ce-containing inclusions and segregation of Ce. The results show that, after adding Ce, large, angular, hard and brittle inclusions (TiN-Al2O3, TiN and Al2O3) can be modified to fine and dispersed Ce-containing inclusions (Ce-Al-O-S and TiN-Ce-Al-O-S). During the solidification, Ce-containing inclusions can be used as heterogeneous nucleation particles to refine as-cast grains. During the hot deformation, Ce-containing inclusions can pin dislocation movement and grain boundary migration, induce dynamic recrystallization (DRX) nucleation, and avoid the formation and propagation of micro cracks and gaps. In addition, During the solidification, Ce atoms will enrich at the front of solid-liquid interface, resulting in composition supercooling and refining the secondary dendrites. Similarly, during the hot deformation, Ce atoms tend to segregate at the boundaries of DRX grains, inhibiting the growth of grains. Under the synergistic effect of Ce-containing inclusions and Ce segregation, although the hot deformation resistance and hot deformation activation energy are improved, DRX is more likely to occur and the size of DRX grains is significantly refined, and the problem of hot deformation cracking can be alleviated. Finally, the microhardness of samples was measured. The results showed that, compared with as-cast samples, the microhardness of hot-deformed samples increases significantly, and with the increase of DRX degree, the microhardness decreases continuously. In addition, Ce can affect the microhardness of Mn18Cr18N steel by affecting as-cast and hot deformation microstructure.

Research Article
Enhancing formability of FeSi6.5 steel by anodic polarization
Dong Zhao, Feng Ye, Binbin Liu, Haoyang Du, Yaakov B. Unigovski, Emmanuel M. Gutman, and Roni Shneck
Available online 23 September 2021, https://doi.org/10.1007/s12613-021-2356-5
[Abstract](51) [PDF 610KB](8)
Abstract:

The effect of anodic polarization on plastic deformation behavior and formability of FeSi6.5 steel at room temperature was experimentally investigated through uniaxial tensile and drawing of wire specimen in sulfuric acid solution with current densities of 0-40 mA/cm2. The formability of the FeSi6.5 steel was significantly improved after the anodic polarization. The plastic elongation of the specimen as an anode in the electrochemical environment was 4.4-7%, but 2.7% in the air. The drawing force under the anodic polarization decreased by 12.5-26% compared to that in deionized water. The softening is mainly attributed to the relief in work hardening caused by surface atomic dissolution. The work hardening mechanism of the FeSi6.5 steel wires under anodic polarization condition was analyzed using Hollomon equation and Voce relation combined with the K-M approach. These data support the view that the surface atom dissolution facilitates dislocation slip. FeSi6.5 steel wires were obtained using electrochemical cold drawing and presented a smooth surface and good ductility without crack after five-pass drawing with a total cross-section area reduction of 88%. The drawing with the assistance of anodic polarization is a promising technology for processing hard and brittle metal materials.

Research Article
Effect of extrusion on the microstructure and mechanical properties of a low-alloyed Mg-2Zn-0.8Sr-0.2Ca matrix composite reinforced by TiC nano-particles
Zedong Wang, Kaibo Nie, Kunkun Deng, and Jungang Han
Available online 14 September 2021, https://doi.org/10.1007/s12613-021-2353-8
[Abstract](58) [PDF 701KB](12)
Abstract:

In this work, a low-alloyed Mg-2Zn-0.8Sr-0.2Ca matrix composite reinforced by TiC nano-particles is successfully prepared by semi-solid stirring under the assistance of ultrasonic and then the as-cast composite is hot extruded. The results indicate that the volume fraction of dynamical recrystallization and the recrystallized grain size have a certain decline at lower extrusion temperature or rate. The finest grain size of ~0.30 µm is obtained in the sample extruded at 200℃ and 0.1 mm/s. The as-extruded sample displays a strong basal texture intensity, and the basal texture intensity increases to 5.937 mud while the extrusion temperature increases from 200℃ to 240℃. The ultra-high mechanical properties (ultimate tensile strength of 480.2 MPa, yield strength of 462 MPa) are obtained after extrusion at 200℃ with a rate of 0.1 mm/s. Among all strengthening mechanisms for the present composite, grain refinement contributes the most to the increase in strength. A mixture of cleavage facets and dimples are observed in the fracture surfaces of three as-extruded nanocomposites, which explain a mix of brittle-ductile fracture way of the samples.

Invited Review
A review on strengthening-toughening behaviors and mechanisms of advanced structural materials by multi-field coupling treatment
Xiu Song, Lei Wang, and Yang Liu
Available online 10 September 2021, https://doi.org/10.1007/s12613-021-2350-y
[Abstract](46) [PDF 1435KB](3)
Abstract:

Applying an external field has been known to be a promising method to control the microstructure of materials, leading to their improved performance. In the present paper, the strengthening and toughening behaviors of some typical high-performance structural materials by coupling multi-physics fields, including electrostatic or electric-pulse, thermal, and stress fields, are reviewed in detail. In addition to the general observation that the plasticity of materials could be increased by multi external fields, their strengthening can also be achieved through controlling atomic diffusion or phase transformations. The paper is not limited to the strengthening and toughening mechanisms of the multi-field coupling effects on different types of structural materials, but is intended to provide a generic method to improve both the strength and ductility of the materials. Finally, future prospects about applications of multi external field have also been put forward based on the current works.

Research Article
Multicomponent transition metal phosphide for oxygen evolution
Lihua Liu, Ning Li, Jingrui Han, Kaili Yao, and Hongyan Liang
Available online 10 September 2021, https://doi.org/10.1007/s12613-021-2352-9
[Abstract](65) [PDF 1596KB](3)
Abstract:

Transition metal phosphides (TMPs) have exhibited decent performance for oxygen evolution reaction (OER), which is a kinetic bottleneck in many energy storages and conversion systems. However, most reported catalysts are composed of three or fewer metallic components, and the investigation of Multicomponent TMPs with more than four metallic components is hindered by their intrinsic complexity in rationally design the structure and fundamentally comprehension in the component-activity correlation. Here, we reported a facile strategy for combining TMPs with tunable elemental compositions (Ni, Fe, Mn, Co, Cu) on a two-dimensional titanium carbide (MXene) flake through a hydrothermal growth and subsequent phosphorization. The obtained TMPs/MXene hybrid nanostructures present homogeneously distributed elements, high electrical conductivity, and strong interfacial interaction, resulting in an accelerated reaction kinetics and long-term stability. OER performance of catalysts with different components was compared and the results show that NiFeMnCoP/MXene is the most active one with a low overpotential of 240 mV at 10 mA cm-2, a small Tafel slope of 41.43 mV dec-1, and a robust long-term electrochemical stability. The electrocatalytic mechanism investigation revealed that the enhanced OER performance of NiFeMnCoP/MXene results from a strong synergistic effect of the multi-elemental composition. Our work, therefore, provides a scalable synthesis route for multi-elemental TMPs and a valuable guideline for designing efficient MXene-supported catalysts.

Research Article
Compressive fatigue behavior and failure evolution of additive fiber-reinforced cemented tailings composites
Jiajian Li, Shuai Cao, and Erol Yilmaz
Available online 10 September 2021, https://doi.org/10.1007/s12613-021-2351-x
[Abstract](131) [PDF 2377KB](23)
Abstract:

The ordinary cemented tailings backfill (CTB) was a cement-based composite prepared from tailings, cementitious materials and water. In this study, a series of laboratory tests including uniaxial compression, digital image correlation (DIC) measurement and scanning electron microscope (SEM) characteristics of fiber-reinforced CTB (FRCTB) was conducted to obtain the uniaxial compressive strength (UCS), failure evolution and microstructural characteristics of FRCTB specimens. The results have shown that: adding fibers could increase the UCS values of the CTB by 6.90 to 32.76%. The UCS value of the FRCTB increased with the PP fiber content increased. Besides, the reinforcement effect of PP fiber on the CTB was better than that of glass fiber. Besides, the addition of fiber could increase the peak strain of the FRCTB by 0.39 to 1.45%. And the peak strain of FRCTB increased with the glass fiber content increased. The failure pattern of FRCTB was coupled with tensile and shear failure. The addition of fiber effectively inhibited the propagation of cracks, and the bridging effect of cracks by the fiber effectively improved the mechanical properties of the FRCTB. The findings in this study can provide a basis for the backfilling design and optimization of backfilling method mining.

Research Article
Effect of samarium on N2 selectivity of SmxMn0.3−xTi catalysts during selective catalytic reduction of NOx with NH3
Shengyang Zhang, Bolin Zhang, Boyu Wu, Bo Liu, and Shengen Zhang
Available online 7 September 2021, https://doi.org/10.1007/s12613-021-2348-5
[Abstract](61) [PDF 863KB](9)
Abstract:

The objective of this work is to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3. A series of SmxMn0.3–xTi catalysts (x = 0, 0.1, 0.15, 0.2, 0.3) were prepared by co-precipitation. The activity tests indicated that the Sm0.15Mn0.15Ti catalyst showed superior performances with NO conversion of 100% and N2 selectivity above 87% at 180–300°C. The characterizations showed that the doping of Sm suppressed the crystallization of TiO2 and Mn2O3 phases, and increased the specific surface area and acidity. Especially, the surface area increased from 152.2 m2·g−1 of Mn0.3Ti to 241.7 m2·g−1 of Sm0.15Mn0.15Ti. These all contributed to the catalytic activity. The XPS results indicated that the relative atomic ratios of Sm3+/Sm and Oβ/O of Sm0.15Mn0.15Ti were 76.77% and 44.11%, respectively. The existence of Sm contributed to the increase of surface absorbed oxygen (Oβ) and the decrease of the surface concentration of Mn4+, which improved the catalytic activity. In the results of H2-TPR, the presence of Sm induced higher reduction temperature and lower H2 consumption (0.3 mmol g–1) of Sm0.15Mn0.15Ti catalyst than that of Mn0.3Ti catalyst. The decrease of Mn4+ weakened the redox property of the catalysts, and increased the N2 selectivity by suppressing the formation of N2O from both NH3 oxidation and nonselective catalytic reduction reaction. The results of in situ DRIFT spectra revealed that the NH3-SCR of NO over Sm0.15Mn0.15Ti catalyst mainly followed the Eley-Rideal mechanism. The Sm doping increases surface absorbed oxygen and weakens the redox property to improve the NO conversion and N2 selectivity of Sm0.15Mn0.15Ti catalyst.

Research Article
Effect of the capsule on deformation and densification behavior of nickel-based superalloy compact during hot isostatic pressing
Lebiao Yang, Xiaona Ren, Chao Cai, Pengju Xue, M. Irfan Hussain, Yusheng Shi, and Changchun Ge
Available online 7 September 2021, https://doi.org/10.1007/s12613-021-2349-4
[Abstract](53) [PDF 1458KB](2)
Abstract:

The Shima yield criterion used in finite element analysis for nickel-based superalloy powder compact during hot isostatic pressing (HIP) was modified through uniaxial compression experiments. The influence of cylindrical capsule characteristics on FGH4096M superalloy powder compact deformation and densification behavior during HIP was investigated through simulations and experiments. Results reveals the simulation shrinkage prediction fitted well with the experimental shrinkage including a maximum shrinkage error of 1.5%. It was shown that the axial shrinkage was 1.7% bigger than radial shrinkage for a cylindrical capsule with the size of Φ50 mm × 100 mm due to the force arm difference along the axial and radial direction of the capsule. The stress deviated from the isostatic state in the capsule led to the uneven shrinkage and non-uniform densification of the powder compact. The ratio of the maximum radial displacement to axial displacement increased from 0.47 to 0.75 with the capsule thickness increased from 2 mm to 4 mm. The pressure transmission was related to the capsule thickness and the capsule material performance, and physical parameters in the HIP process.

Research Article
In-situ observation of the kinetic dissolution of Al2O3 particles in CaO-Al2O3-SiO2 slags using laser confocal scanning microscopy
Changyu Ren, Caide Huang, Lifeng Zhang, and Ying Ren
Available online 31 August 2021, https://doi.org/10.1007/s12613-021-2347-6
[Abstract](65) [PDF 677KB](14)
Abstract:

The dissolution kinetics of Al2O3 in CaO-Al2O3-SiO2 slags was studied using high-temperature confocal scanning laser microscope at 1773 to 1873 K. The results show that the controlling step during the Al2O3 dissolution was diffusion in the molten slag. It was found that dissolution curves of Al2O3 particles was hardly agreed with the traditional boundary layer diffusion model with the increase of the CaO/Al2O3 of slag. A modified diffusion equation considering slag viscosity was developed to study the dissolution mechanism of Al2O3 in slag. Diffusion coefficients of Al2O3 in slag were calculated as 2.8 ×10-10 to 4.1 ×10-10 m2/s. The dissolution rate of Al2O3 increased with higher temperature, CaO/Al2O3, and particle size. A new model was shown to be vAl2O3 = 0.16 × R01.58 × x3.52 × (T-Tmp)1.11 to predict the dissolution rate and the total dissolution time of Al2O3 inclusions with various sizes.

Research Article
Mg-intercalation engineering of MnO2 electrode for high-performance aqueous magnesium-ion batteries
Yue Zhao, Bei Wang, Minjie Shi, Shibo An, Liping Zhao, and Chao Yan
Available online 31 August 2021, https://doi.org/10.1007/s12613-021-2346-7
[Abstract](90) [PDF 1353KB](9)
Abstract:

Rechargeable aqueous magnesium-ion batteries (MIBs) show great promise for low-cost, high-safety, and high-performance energy storage applications. Although manganese dioxide (MnO2) is considered as a potential electrode material for aqueous MIBs, the low electrical conductivity and unsatisfactory cycling performance greatly hinder the practical application of MnO2 electrode. To overcome these problems, herein, a novel Mg-intercalation engineering approach for MnO2 electrode to be used in aqueous MIBs is presented, wherein the structural regulation and electrochemical performance of the Mg-intercalation MnO2 (denoted as MMO) electrode are thoroughly investigated by Density functional theory (DFT) calculations and in-situ Raman investigation. The results demonstrate that the Mg intercalation is essential to adjusting the charge/ion state and electronic band gap of MMO electrode, as well as the highly reversible phase transition of the MMO electrode during the charging–discharging process. Because of these remarkable characteristics, the MMO electrode can be capable of delivering a significant specific capacity of ~419.8 mAh g-1, while exhibiting a good cycling capability over 1000 cycles in 1 M aqueous MgCl2 electrolyte. On the basis of such MMO electrode, we have successfully developed a soft-packaging aqueous MIB with excellent electrochemical properties, revealing its huge application potential as the efficient energy storage devices.

Research Article
Effect of Co2+ substitution in B-sites of the perovskite system on the phase formation, microstructure, electrical and magnetic properties of Bi0.5(Na0.68K0.22Li0.10)0.5TiO3 ceramics
Pamornnarumol Bhupaijit, Chonnarong Kaewsai, Tawat Suriwong, Supree Pinitsoontorn, Surirat Yotthuan, Naratip Vittayakorn, and Theerachai Bongkarn
Available online 26 August 2021, https://doi.org/10.1007/s12613-021-2345-8
[Abstract](93) [PDF 1368KB](21)
Abstract:

Bi0.5(Na0.68K0.22Li0.10)0.5Ti1-xCoxO3 lead-free perovskite ceramics (BNKLT-xCo, x = 0, 0.005, 0.010, 0.015 and 0.020) were fabricated via the solid-state combustion technique. A small-amount of Co2+ ion substitution into Ti-sites led to modification of the phase formation, microstructure, electrical and magnetic properties of BNKLT ceramics. Coexisting rhombohedral and tetragonal phases were observed in all samples using the XRD technique. The Rietveld refinement revealed that the rhombohedral phase increased from 39 to 88 % when x increased from 0 to 0.020. The average grain size increased when x increased. With increasing x, more oxygen vacancies were generated, leading to asymmetry in the S-E loops. For the composition of x = 0.010, a high dielectric constant (m) of 5384 and a large strain (Smax) of 0.23 % with d33* (Smax/Emax) of 460 pm/V were achieved. The BNKLT-0Co ceramic showed diamagnetic behavior but all of the BNKLT-xCo ceramics exhibited paramagnetic behavior, measured at 50 K.

Research Article
Bioleaching and biosorption behavior of vanadium-bearing stone coal by Bacillus mucilaginosus
Yingbo Dong, Shijia Chong, and Hai Lin
Available online 21 August 2021, https://doi.org/10.1007/s12613-021-2344-9
[Abstract](352) [PDF 605KB](35)
Abstract:

The recovery of vanadium (V) from stone coal by bioleaching is a promising method. The bioleaching experiments and the biosorption experiments were carried out, aiming to explore the adsorption characteristics of Bacillus mucilaginosus (B. mucilaginosus) on the surface of vanadium-bearing stone coal, and the related mechanisms have been investigated. After bioleaching at 30°C for 28 days, the cumulative leaching rate of V reached 60.2%. The biosorption of B. mucilaginosus on stone coal was affected by many factors. When the leaching system pH=5.0, strong electrostatic attraction between bacteria and stone coal promoted biosorption. Bacteria in the logarithmic growth phase had mature and excellent biosorption properties. The initial bacterial concentration of 3.5×108 cfu/mL was conducive to adhesion, with 38.9% adsorption rate and 3.6×107 cfu/g adsorption quantity. The adsorption of B. mucilaginosus on the stone coal conformed to the Freundlich model and the pseudo-second-order kinetic model. Bacterial surface carried functional groups (-CH2, -CH3, -NH2, et al.), which were highly correlated with the adsorption behavior. In addition, biosorption changed the surface properties of stone coal, resulting in the isoelectric point (IEP) approaching the bacteria. The results of our study could provide an effective reference for the adsorption laws of bacteria on minerals.

Research Article
In situ carbon coating for enhanced chemical stability of copper nanowires
Xiaolan Tong, Hao Hu, Xingzhong Zhao, and Qidong Tai
Available online 21 August 2021, https://doi.org/10.1007/s12613-021-2343-x
[Abstract](104) [PDF 978KB](11)
Abstract:

Copper nanowires (CuNWs) are promising electrode materials, especially for being used in flexible and transparent electrodes, due to their advantages of earth-abundant, low-cost, high conductivity and flexibility. However, the poor stability of CuNWs against oxidation and chemical corrosion seriously hinders their practical applications. Herein, we propose a facile strategy to improve the chemical stability of CuNWs by in situ coating of carbon protective layer on top of them through hydrothermal carbonization method. The influential factors on the growth of carbon film including the concentration of the glucose precursor (carbon source), hydrothermal temperature and time are systematically studied. By tailoring these factors, carbon layers with thickness of 3-8 nm can be uniformly grown on CuNWs with appropriate glucose concentration around 80 mg mL-1, hydrothermal temperature of 160-170 ℃, and hydrothermal time of 1-3 h. The as-prepared carbon-coated CuNWs show excellent resistance against corrosion and oxidation and are of great potential to be used broadly in various optoelectronic devices.

Invited Review
Research progress of interface modification and thermal conduction behavior of diamond/metal composites
Ping Zhu, Pingping Wang, Puzhen Shao, Xiu Lin, Ziyang Xiu, Qiang Zhang, Equo Kobayashi, and Gaohui Wu
Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2339-6
[Abstract](62) [PDF 1152KB](12)
Abstract:

Diamond/metal composites are widely used in national defense technology and national production due to their outstanding properties of high thermal conductivity and low expansion. However, the difference of chemical properties leads to the interface incompatibility between diamond and metal, which has an important impact on the properties of the composites. Interfacial modification is an effective way to improve the interfacial bonding and reduce the interfacial thermal resistance. This paper reviews the experimental research on interface modification of diamond/metal composites and the application of material calculation simulation in diamond/metal composites. Combining computational simulation and experiment is an expected method to advance the research of diamond/metal composite interface modification.

Research Article
Effects of Li addition on microstructures and tensile properties of the extruded Mg–1Zn–xLi alloy
Jun Zhao, Bin Jiang, Qinghang Wang, Ming Yuan, Yanfu Chai, Guangsheng Huang, and Fusheng Pan
Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2340-0
[Abstract](124) [PDF 1527KB](10)
Abstract:

Li addition is verified to be an effective method to increase the room temperature ductility and formability of Mg alloys. In the present study, the microstructure, texture and tensile properties of extruded Mg–1Zn–xLi (wt%, x=0, 1, 3, 5) alloy sheets were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). It is found that Li addition resulted in the grain coarsening and the development of new transverse direction (TD)–tilting and 〈10–10〉 parallel to extrusion direction textures, which was related to the improved dynamic recrystallization and the increased prismatic slip during extrusion. The Mg–1Zn–5Li sheet showed the weakest texture, which contained both basal and TD–tilting oriented grains. No additional phase was formed with Li addition. Tensile properties showed that the yield strength of Mg–1Zn–xLi sheets gradually decreased with increasing Li content, which was mainly related to grain coarsening and texture weakening. In addition, the ductility of the Mg–1Zn–xLi sheet was remarkably enhanced by Li addition. The elongation of the Mg–1Zn–5Li sheet was 30.3% along the transverse direction, which was three times than that of Mg–1Zn sheet. Microstructural analysis implied that this significant ductility enhancement was associated with the improvement activation of prismatic and basal slips during the tensile tests. This study may provide insights into the development of high-ductility, low-density Mg–Zn–Li based alloys.

Invited Review
Controlled crystal orientation of two-dimensional Ruddlesden-Popper halide perovskite films for solar cells
Jiuyao Du, Mengqi Zhang, and Jianjun Tian
Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2341-z
[Abstract](133) [PDF 1227KB](25)
Abstract:

Metal halide perovskite solar cells have caused great attention due to their high power conversion efficiency (PCE) and cost-effective solution-processable fabrication, but suffer from poor structure stability. Two-dimensional (2D) Ruddlesden-Popper (RP) metal halide perovskites could address the above issue and possess excellent stability because of the large organic spacer cation around the halide octahedron of perovskites. However, the crystallographic orientation of 2D crystals should be perpendicular to the bottom substrates for realizing fast charge transport and collection of the solar cells.  It is still a great challenge to control the crystallographic orientation of the 2D RP perovskites prepared by the solution process. Herein, we reviewed the recent progress of the 2D RP perovskite films with the focus on the crystallographic orientation mechanism and orientation controlling methods. Furthermore, the current issues and prospects of the 2D RP perovskites in the photovoltaic field were also discussed, aiming to shed light on developing and widely applying them in the near future.

Research Article
Microstructure, mechanical properties and deformation mechanisms of an Al-Mg alloy processed by the cyclical continuous expanded extrusion and drawing approach
Ruiqing Lu, Long Zhang, Shuwei Zheng, Dingfa Fu, Jie Teng, Jianchun Chen, Guodong Zhao, Fulin Jiang, and Hui Zhang
Available online 18 August 2021, https://doi.org/10.1007/s12613-021-2342-y
[Abstract](81) [PDF 1800KB](8)
Abstract:

Al-Mg alloys are an important class of non-heat treatable alloys in which Mg solute and grain size play essential role in their mechanical properties and plastic deformation behaviors. In this work, a novel cyclical continuous expanded extrusion and drawing (CCEED) process was proposed and implemented on an Al-3Mg alloy to introduce large plastic deformation. The results showed that the continuous expanded extrusion mainly improved the ductility, while the cold drawing enhanced the strength of the alloy. With the increased processing CCEED passes, the multi-pass cross shear deformation mechanism progressively improved the homogeneity of the hardness distributions and refined grain size. The grain size of the processed Al-3Mg alloy rods was refined by continuous dynamic recrystallization. And the microstructural evolution was basically influenced by the special thermomechanical deformation conditions during the CCEED process.

Research Article
Titanium dioxide-graphene composite electrochemical sensor for detection of hexavalent chromium
Natpichan Pienutsa, Krittamet Yannawibut, Jetthana Phattharaphongmanee, Oukrit Thonganantakul, and Sira Srinives
Available online 12 August 2021, https://doi.org/10.1007/s12613-021-2338-7
[Abstract](163) [PDF 863KB](17)
Abstract:

Hexavalent chromium (Cr(VI)) compound is useful to various industries but is toxic and carcinogenic. In this research work, we fabricate an amperometric sensor for the determination of Cr(VI), using a titanium dioxide (TiO2)-reduced graphene oxide (rGO) composite as the sensing element. The composite was synthesized following sol-gel chemistry, yielding TiO2 nanoparticles of ~50 nm in size, immobilized on chemically exfoliated rGO sheets. The composite was employed in a 3-electrode electrochemical cell and operated in an amperometric mode, exhibiting good responses to the 50 to 500 ppb Cr(VI). Our best result from pH 3 Mcilvane’s buffer solution reveals the sensitivity of 9.12x10-4 ppb-1 and a detection limit of 6 ppb with no signal interference from 200 ppm Ca(II), 150 ppm Mg(II), and 50 ppb Pb(II). The excellent results of the TiO2-rGO sensor can be attributed to synergic effects between TiO2 and rGO, resulting from the presence of n-p heterojunctions and the formation of the TiO2 nanoparticles on rGO.

Invited Review
The kinetics for the hydrogen absorption and desorption processes of hydrogen storage alloys: A review
Qian Li, Xi Lin, Qun Luo, Yuan Chen, Jingfeng Wang, Bin Jiang, and Fusheng Pan
Available online 6 August 2021, https://doi.org/10.1007/s12613-021-2337-8
[Abstract](1005) [PDF 1156KB](66)
Abstract:

High hydrogen absorption and desorption rates are two of significant index parameters for the applications of hydrogen storage tanks. Analysis of the hydrogen absorption and desorption behaviours by the isothermal kinetic models is an efficient way to investigate the kinetic mechanism. Multitudinous kinetic models have been developed to describe the kinetic processes. However, these kinetic models were deduced based on some assumptions and only appropriate for the specific kinetic measurement methods and rate-controlling steps, which is sometimes confusing for application. The kinetic analysis procedures using those kinetic models, as well as the key kinetic parameters, are not clear for many researchers who do not become familiar with this field. These problems will prevent kinetic models and their analysis methods from revealing the kinetic mechanism of hydrogen storage alloys. Thus, this review mainly focuses on the summarisation of the kinetic models based on the different kinetic measurement methods and rate-controlling steps, and the introduction of the analysis procedures and the applications of kinetic models in metal hydrides.

Research Article
Effect of chromium interlayer thickness on interfacial thermal conductance across copper/diamond interface
Xiaoyan Liu, Fangyuan Sun, Luhua Wang, Zhanxun Che, Guangzhu Bai, Xitao Wang, Jinguo Wang, Moon J. Kim, and Hailong Zhang
Available online 29 July 2021, https://doi.org/10.1007/s12613-021-2336-9
[Abstract](139) [PDF 1745KB](26)
Abstract:

The thermal conductivity of diamond particles reinforced copper matrix  composite as an attractive thermal management material is significantly lowered by the non-wetting heterointerface. The paper investigates the heat transport behavior between a 200 nm Cu layer and a single-crystalline diamond substrate inserted by a chromium (Cr) interlayer having a series of thicknesses from 150 nm down to 5 nm. The purpose is to detect the impact of the modifying interlayer thickness on the interfacial thermal conductance (h) between Cu and diamond. The time-domain thermoreflectance measurements suggest that the introduction of Cr interlayer dramatically improves the h between Cu and diamond owing to the enhanced interfacial adhesion and bridged dissimilar phonon states between Cu and diamond. The h value exhibits a decreasing trend as the Cr interlayer becomes thicker because of the increase in thermal resistance of Cr interlayer. The high h values are observed for the Cr interlayer thicknesses below 21 nm since phononic transport channel dominates the thermal conduction in the ultrathin Cr layer. The findings provide a way to tune the thermal conduction across the metal/nonmetal heterogeneous interface, which plays a pivotal role in designing materials and devices for thermal management applications.

Research Article
Effect of chemical composition on the micromorphology, phase composition, and calcification roasting process of vanadium slag
Tangxia Yu, Tao Jiang, Jing Wen, Hongyan Sun, Ming Li, and Yi Peng
Available online 24 July 2021, https://doi.org/10.1007/s12613-021-2334-y
[Abstract](104) [PDF 1739KB](8)
Abstract:

The chemical composition of vanadium slag significantly affects its element distribution and phase composition, which affect the subsequent calcification roasting process and vanadium recovery. In this work, seven kinds of vanadium slags derived from different regions in China were used as the raw materials to study the effects of different components on the vanadium slag’s micromorphology, phase composition, calcification roasting, and leaching rate of major elements using SEM, XRD, and ICP-AES. The results showed that the spinel phase was wrapped with silicate phase in all vanadium slag samples. The main elements in the spinel phase were Cr, V, and Ti from the interior to the exterior. The size of spinel phase in low chromium vanadium slag was larger than other vanadium slags with higher chromium contents. The spinel phase of high-calcium and high-phosphorus vanadium slag was more dispersed. The strongest diffraction peak of vanadium spinel phase in vanadium slag migrated to a higher diffraction angle, and (Fe0.6Cr0.4)2O3 was formed after calcification roasting as the chromium content increased. A large amount of Ca2SiO4 was produced because excess Ca reacted with Si in high-calcium and high-phosphorus vanadium slag. The vanadium leaching rates reached 88% in some vanadium slags. The chromium leaching rates were less than 5% in all vanadium slags. The silicon leaching rate in high-calcium and high-phosphorus vanadium slag was much higher than other slags. The leaching rates of manganese were higher than 10%, and the leaching rate of iron and titanium were negligible.

Research Article
The effects of shape and particle size on the photocatalytic kinetics and mechanism of nano-CeO2
Zixiang Cui, Lu Zhang, Yongqiang Xue, Yanan Feng, Mengying Wang, Jiaojiao Chen, Boteng Ji, Chenyu Wang, and Yidi Xue
Available online 20 July 2021, https://doi.org/10.1007/s12613-021-2332-0
[Abstract](87) [PDF 889KB](6)
Abstract:

Nanomaterials have been widely applied to many fields because of their excellent photocatalytic performance. The performance is closely related to the catalytic kinetics, but it is not completely clear that the influencing regularities of shape and particle size on the photocatalytic kinetics of nanomaterials and the photocatalytic kinetic mechanism. In this paper, nano-CeO2 with different shapes and particle sizes were prepared, the kinetic parameters of adsorption and photocatalytic degradation were determined, and the effects of shape and particle size on the kinetics of adsorption and photocatalysis and photocatalytic mechanism were discussed. The results show that the shape and particle size have significant influences. With the decreases of diameter, the performances of adsorption and photocatalysis of nano-CeO2 are improved; and these performances of spherical nano-CeO2 are greater than those of linear nano-CeO2. The shape and particle size have no effects on the kinetic order and mechanism of the whole photocatalytic process. Then a generalized mechanism of photocatalytic kinetics of nanomaterials was proposed and the mechanism rate equation was derived. Finally, the conclusion can be drawn: the desorption of photodegradation products is the control step of photocatalytic kinetics, and the kinetic order of photocatalytic degradation reaction is 1. The mechanism is universal and all nanomaterials have the same photocatalytic kinetic mechanism and order.

Invited Review
Research progress on selective laser melting processing for nickel-based superalloy
Maohang Zhang, Baicheng Zhang, Yaojie Wen, and Xuanhui Qu
Available online 19 July 2021, https://doi.org/10.1007/s12613-021-2331-1
[Abstract](203) [PDF 2638KB](21)
Abstract:

Selective laser melting (SLM), an additive manufacturing (AM) process mostly applied in metal material field, can fabricate complex shaped metal objects with high precision. Nickel-based superalloy possesses excellent mechanical property at elevated temperature and plays an important role in aviation industry. This paper emphasizes the researches of SLM processed Inconel 718, Inconel 625, CM247LC and Hastelloy X which are typical alloys with different strengthening mechanism and operating temperature. The strengthening mechanism and phase change evolution of different Nickel-based superalloy under laser irradiation are discussed. The influence of laser parameter and heat-treatment process on mechanical properties of SLM Nickel-based superalloy are systematically introduced. Moreover, the attractive industrial applications of SLM Nickel-based superalloy and printed components are presented. At last, the development of Nickel-based superalloy materials for SLM technology is prospected.

Research Article
Preparation and oxidation characteristics of ZrC-ZrB2 composite powders with different proportions
Yu Wang, Guohua Zhang, and Kuochih Chou
Available online 13 July 2021, https://doi.org/10.1007/s12613-021-2330-2
[Abstract](103) [PDF 1203KB](12)
Abstract:

ZrC and ZrB2 are both typical ultra-high temperature ceramics, which can be used in hyperthermal environment. In this study, a method for preparing ultrafine ZrC-ZrB2 composite powder is provided, by using the raw materials of nano ZrO2, carbon black, B4C, and metallic Ca. It is worth pointing out that ZrC-ZrB2 composite powder with any proportion of ZrC to ZrB2 could be synthesized by this method. Firstly, a mixture of ZrC and C is prepared by carbothermal reduction of ZrO2. By adjusting the addition amount of B4C, ZrC is boronized by B4C to generate ZrC-ZrB2 composite powder with different compositions. Using this method, five composition powders with different molar ratios (100ZrC, 75ZrC-25ZrB2, 50ZrC-50ZrB2, 25ZrC-75ZrB2, and 100ZrB2) are prepared. When the temperature of boronization and decarburization process is 1473 K, the particle size of product is only tens of nanometres. Finally, the oxidation characteristics of different composite powders are investigated through oxidation experiments. The oxidation resistance of ZrC-ZrB2 composite powder continues to increase as the content of ZrB2 increased.

Research Article
Effects of Zr content on electrochemical performance of Ti/Sn-Ru-Co-ZrOx electrodes
Linhui Chang, Sheng Chen, Xionghui Xie, Buming Chen, Haihong Qiao, Hui Huang, Zhong-cheng Guo, Yapeng He, and Ruidong Xu
Available online 7 July 2021, https://doi.org/10.1007/s12613-021-2326-y
[Abstract](255) [PDF 891KB](36)
Abstract:

The low cell voltage during electrolytic Mn from the MnCl2 system can effectively reduce the power consumption. In this work, the Ti/ Sn-Ru-Co-Zr modified anodes were obtained by using thermal decomposition oxidation. The physical parameters of coatings were observed by SEM. Based on the electrochemical performance and SEM/XRD of the coatings, the influences of Zr on electrode performance were studied and analyzed. When the mole ratio of Sn-Ru-Co-Zr = 6:1:0.8:0.3, the cracks on the surface of coatings were the smallest, and the compactness was the best due to the excellent filling effect of ZrO2 nanoparticles. Moreover, the electrode prepared under this condition had the lowest mass transfer resistance and high chloride evolution activity in the 1M NH4Cl + 1.5M HCl system. The service life of 3102 h was achieved according to the empirical formula of accelerated-life-test of the new type anode.

Research Article
Effect of additives on iron recovery and dephosphorization by reduction roasting-magnetic separation of refractory high-phosphorus iron ore
Shichao Wu, Zhengyao Li, Tichang Sun, Jue Kou, and Xiaohui Li
Available online 7 July 2021, https://doi.org/10.1007/s12613-021-2329-8
[Abstract](314) [PDF 916KB](20)
Abstract:

The effect of CaCO3, Na2CO3 and CaF2 on the reduction roasting-magnetic separation of high-phosphorus iron ore containing phosphorus as Fe3PO7 and apatite was investigated. The result shows that Na2CO3 had the best effect on iron recovery and dephosphorization, followed by CaCO3, while CaF2 had almost no influence. The mechanism of CaCO3, Na2CO3 and CaF2 was studied by XRD and SEM-EDS. It turns out that Fe3PO7 was reduced to elemental phosphorus and formed iron phosphorus alloy with metallic iron without additives. The addition of CaCO3 reacted with Fe3PO7 to generate massive Ca3(PO4)2 and promoted the reduction of iron oxides, however, the growth of iron particles was inhibited. After adding Na2CO3, the phosphorus in Fe3PO7 was transferred to nepheline and Na2CO3 improved the reduction of iron oxides and the growth of iron particles, therefore, the recovery of iron and the separation of iron and phosphorus achieved the best. CaF2 reacted with Fe3PO7 to form fine Ca3(PO4)2 particles scattered around the iron particles, which made the separation of iron and phosphorus difficult.

Research Article
Effect of trace yttrium on the microstructure, mechanical property, and corrosion behavior of homogenized Mg-2Zn-0.1Mn-0.3Ca-xY biological magnesium alloy
Liangyu Wei, Mingfan Qi, Yuzhao Xu, Jingyuan Li, Jin Wang, Aisen Liu, and Jicheng Wang
Available online 7 July 2021, https://doi.org/10.1007/s12613-021-2327-x
[Abstract](83) [PDF 1933KB](6)
Abstract:

The effects of trace yttrium (Y) element on the microstructure, mechanical properties, and corrosion resistance of Mg-2Zn-0.3Ca-0.1Mn-xY (x=0, 0.1, 0.2, 0.3) biological magnesium alloys are investigated. Results show that grain size decreases from 310μm to 144μm when the Y content increases from 0 wt.% to 0.3 wt.%. At the same time, the volume fraction of the second phase increases from 0.4% to 6.0%, the yield strength of the alloy continues to increase, and the ultimate tensile strength and elongation decrease initially and then increase. When the Y content element increases to 0.3 wt.%, Mg3Zn6Y phase begins to precipitate in the alloy; thus, the alloy exhibits the most excellent mechanical property. At this time, its ultimate tensile strength, yield strength, and elongation are 119MPa, 69MPa, and 9.1%, respectively. In addition, when the Y content is 0.3 wt.%, the alloy shows the best corrosion resistance in the simulated body fluid (SBF). This investigation has revealed that the improvement of mechanical properties and corrosion resistance is mainly attributed to the grain refinement and the precipitated Mg3Zn6Y phase.

Invited Review
A review on the recent progress of efficient utilization of titanium-bearing blast furnace slag
Yongfeng Cai, Ningning Song, Yunfei Yang, Lingmin Sun, Peng Hu, and Jinshu Wang
Available online 30 June 2021, https://doi.org/10.1007/s12613-021-2323-1
[Abstract](141) [PDF 808KB](13)
Abstract:

Considering the valuable compositions and potential environmental hazardousness of titanium-bearing blast furnace slag (BFS), developing efficient and green approaches to utilization of BFS is highly desired for resource economization and environmental protection. In the past decades, many attempts have been adopted to efficiently reuse BFS, and significant advances in understanding the fundamental features and the development of efficient approaches have been made. In this review, we have provided a comprehensive overview of the latest progress on efficient utilization BFS, and discussed the mechanism and characteristics of various approaches, along with their application prospects. In particular, the approaches of extraction and enrichment of titanium-bearing phases from BFS are highlighted due to their high availability of titanium resources. This systemic and comprehensive review may benefit to design new and green utilization route with high efficiency and low cost.

Research Article
Oxidation resistance of PM Ti-45Al-10Nb alloy at high temperature
Xuchen Jin, Peihao Ye, Hongrui Ji, Zhuanxia Suo, Boxin Wei, Xuewen Li, and Wenbin Fang
Available online 24 June 2021, https://doi.org/10.1007/s12613-021-2320-4
[Abstract](77) [PDF 1068KB](2)
Abstract:

TiAl alloy with high Nb content, nominally Ti-45Al-10Nb, was prepared by powder metallurgy, and the oxidation resistance at 850, 900, and 950℃ was investigated. The high-temperature oxidation-resistance mechanism and oxidation dynamics were discussed following the oxide skin morphology and microstructural evolution analysis. The oxide skin structures were similar for 850 and 900℃, with TiO2+Al2O3 mixture covering TiO2 with dispersed Nb2O5. At 950℃, the oxide skin was divided into four sublayers, from the outside to the parent metal: loose TiO2+Al2O3, dense Al2O3, dense TiO2+Nb2O5, and TiO2 matrix with dispersed Nb2O5. The Nb layer suppressed the outward diffusion of Ti atoms, hindering the growth of TiO2, and simultaneously promote the formation of a continuous Al2O3 protective layer, providing the alloy with long-term high-temperature oxidation resistance.

Research Article
Utilization of DTAB as a collector for reverse flotation separation of quartz from fluorapatite
Wenbiao Liu, Wenxuan Huang, Feng Rao, Zhanglei Zhu, Yongming Zheng, and Shuming Wen
Available online 24 June 2021, https://doi.org/10.1007/s12613-021-2321-3
[Abstract](306) [PDF 481KB](10)
Abstract:

Reverse flotation desilication has been an indispensable step for obtaining high-grade fluorapatite. In this work, Dodecyl Trimethyl Ammonium Bromide (DTAB) was recommended as an efficient collector for the reverse flotation separation of quartz from fluorapatite. Its collectivity for quartz and selectivity for fluorapatite were also compared with the figures corresponding to the conventional collector dodecylamine hydrochloride (DAC) via micro-flotation experiments. The adsorption behaviors of both DTAB and DAC on minerals were systematically investigated with surface chemical analyses such as contact angle determination, zeta potential detection, and adsorption density measurement. It was revealed that compared to DAC, DTAB displayed similar and strong collectivity for quartz, while it showed a better selectivity (or worse collectivity) for fluorapatite, resulting in a high-efficiency for the separation of the two minerals. Surface chemical analyses showed that the adsorption ability of DTAB on quartz surface was as strong as DAC, while the adsorption amount of DTAB on fluorapatite surface was much lower than that of DAC, which associated to the flotation performance well. During the floatation separation of the actual ore, 8% fluorapatite with higher grade can be obtained by using DTAB in contrast to DAC. Therefore, DTAB is a promising collector to the high-efficiency purification and sustainable utilization of the valuable fluorapatite recourses.

Research Article
Influences of multiple laser shock peening impacts on microstructure and mechanical properties of Ti-6Al-4V alloy fabricated by electron beam melting
Liang Lan, Ruyi Xin, Xinyuan Jin, Shuang Gao, and Bo He
Available online 24 June 2021, https://doi.org/10.1007/s12613-021-2322-2
[Abstract](156) [PDF 1248KB](11)
Abstract:

Laser shock peening (LSP) is an attractive post-processing method to tailor surface microstructure and enhance mechanical performances of additive manufactured (AM) components. The effects of multiple LSP impacts on the microstructure and mechanical properties of Ti-6Al-4V part produced by electron beam melting (EBM), as a mature AM process, were studied in this work. Microstructure, surface topography, residual stress and tensile performance of EBM-manufactured Ti-6Al-4V specimens were systematically analyzed subjected to different LSP impacts. The distribution of porosities in EBM sample was assessed via X-ray computed tomography. The results show that EBM samples with two LSP impacts possess a lower porosity value of 0.05% compared to the value of 0.08% for untreated samples. The strength of EBM samples with two LSP impacts is remarkably raised by 12% as compared with the as-built samples. The grains of α phase is refined in near-surface layer and a dramatic increase in the depth and magnitude of compressive residual stress (CRS) is achieved in EBM sample with multiple LSP treatments. The grain refinement of α phase and CRS with larger depth are responsible for the strength enhancement of EBM samples with two LSP impacts.

Research Article
A high thermal conductivity and high strength magnesium alloy for high pressure die cast ultrathin-walled component
Jian Rong, Wenlong Xiao, Xinqing Zhao, Chaoli Ma, Haimiao Liao, Donglei He, Ming Chen, Meng Huang, and Chen Huang
Available online 18 June 2021, https://doi.org/10.1007/s12613-021-2318-y
[Abstract](156) [PDF 1361KB](10)
Abstract:

With 3C industries developing rapidly, the demand for high-thermal-conductivity magnesium alloy with high mechanical performance is increasing rapidly. However, the thermal conductivities of most common Mg foundry alloys (such as Mg-9wt.%-1wt%Zn) are still relativity low. In the present study, we developed a high-thermal-conductivity Mg-4Al-4Zn-4RE-1Ca (wt.%, AZEX4441) alloy with good mechanical properties for ultrathin-walled cellphone components via high pressure die casting (HPDC). The HPDC AZEX4441 alloy exhibited a fine homogeneous microstructure (the average grain size is 2.8 μm) with granular Al11RE3, fibrous Al2REZn2, and networked Ca6Mg2Zn3 phases distributed at the grain boundaries. The room-temperature thermal conductivity of the HPDC AZEX4441 alloy was 94.4 W/(m·K), which was much higher than 53.7 W/(m·K) of the HPDC AZ91D alloy. The Al and Zn elements of the AZEX4441 alloy were largely consumed by the formation of Al11RE3 and Al2REZn2 as well as Ca2Mg6Zn3 phases due to the addition of RE and Ca. Therefore, the lattice distortion induced by solute atoms of the AZEX4441 alloy (0.171%) was much lower than that of AZ91D alloy (0.441%), which was responsible for the high thermal conductivity of the AZEX4441 alloy. Furthermore, the AZEX4441 alloy exhibited a high yield strength (YS) of ~185 MPa, ultimate tensile strength (UTS) of ~233 MPa, and elongation of ~4.2%, indicating comparable tensile properties to AZ91D alloy. The results will contribute to developing high-performance Mg alloys with a combination of high thermal conductivity, high strength, and good castability.

Research Article
Effects of the incorporation amount of CdS and Cd(SCN2H4)2Cl2 on the performance of perovskite solar cells
Jihong Zheng, Liangxin Zhu, Zhitao Shen, Fumin Li, Lanyu Ling, Huilin Li, and Chong Chen
Available online 12 June 2021, https://doi.org/10.1007/s12613-021-2316-0
[Abstract](164) [PDF 1100KB](12)
Abstract:

An excellent organolead halide perovskite film plays an important role for good-performance perovskite solar cells (PSCs), while there are many defects at perovskite crystals, which is bad for both the photovoltaic properties and the stability of solar cells. Therefore, a strategy of incorporating a complex of CdS and Cd(SCN2H4)2Cl2 into CH3NH3PbI3 active layer is proposed to solve this problem. This study systematically analyzes the effect of different doping concentration of CdS and Cd(SCN2H4)2Cl2 on the performance and stability of PSCs. Our results find that an appropriate incorporation concentration of CdS and Cd(SCN2H4)2Cl2 doped in CH3NH3PbI3 can improve the performance of the prepared solar cells, which is mainly due to that the CdS and Cd(SCN2H4)2Cl2 can effectively passivate the defects at perovskite crystals, thereby suppressing the charge recombination in PSCs and promoting the charge extraction at TiO2/perovskite interface. Furthermore, the stability of PSCs is also significantly improved due to the reduced perovskite crystal defects and enhanced compactness of the C:C:CH3NH3PbI3 composite film. 

Research Article
Mechanism of calcium lignosulfonate in apatite and dolomite flotation system
Bo Feng, Liangzhu Zhang, Wenpu Zhang, Huihui Wang, and Zhiyong Gao
Available online 11 June 2021, https://doi.org/10.1007/s12613-021-2313-3
[Abstract](355) [PDF 571KB](19)
Abstract:

Since the physical and chemical properties of apatite and dolomite can be similar, the separation of these two minerals is difficult. Therefore, when performing this separation using the flotation method, it is necessary to search for selective depressants. An experimental research was performed on the separation behavior of apatite and dolomite using calcium lignosulfonate as a depressant, and the mechanism by which this occurs was analyzed. The results show that calcium lignosulfonate has a depressant effect on both apatite and dolomite, but the depressant effect on dolomite is stronger at the same dosage. Mechanism analysis shows that the adsorptive capacity of calcium lignosulfonate on dolomite is higher than that of apatite, which is due to the strong reaction between calcium lignosulfonate and the Ca sites on dolomite. In addition, there is a hydrogen bond between calcium lignosulfonate and dolomite, which further prevents the adsorption of sodium oleate to dolomite, thus greatly inhibiting the flotation of dolomite.

Research Article
Isothermal oxidation behavior of Nb-bearing austenitic cast steels at 950°C
Hailong Zhao, Longfei Li, and Qiang Feng
Available online 11 June 2021, https://doi.org/10.1007/s12613-021-2314-2
[Abstract](197) [PDF 1694KB](6)
Abstract:

The oxidation behaviors of three austenitic cast steels with different morphology of primary carbides at 950°C in air was investigated using SEM, EDS, XRD and FIB/TEM. It was found that their oxidation kinetics followed a logarithmic law and the oxidation rate could be significantly decreased as long as a continuous silica layer formed at the scale/substrate interface. When the local Si concentration was inadequate, the internal oxidation beneath the oxide scale occurred. The spallation of oxides during cooling could be inhibited with the formation of internal oxidation, owing to the reduced mismatch stress between the oxide scale and the substrate. The "Chinese-script" primary Nb(C,N) was superior to the dispersed primary Nb(C,N) in suppressing the oxidation penetration in the interdendritic region by supplying a high density of Cr quick-diffusion channels. In addition, the innermost and the outermost oxidation layers were both found to be enriched with Cr, while the Cr evaporation in the outermost layer was significant when the water-vapor concentration in the environment was high enough. These findings further the understanding regarding the oxidation behavior of austenitic cast steels and will promote the alloy development for exhaust components.

Research Article
Characterization and ultraviolet–visible shielding property of samariumcerium compounds containing Sm2O2S prepared by Co-precipitation method
Yanping Li, Xue Bian, Xun Jin, Peng Cen, Wenyuan Wu, and Gaofeng Fu
Available online 1 June 2021, https://doi.org/10.1007/s12613-021-2309-z
[Abstract](122) [PDF 1452KB](4)
Abstract:

Since ultraviolet (UV) light, as well as blue light, which was part of visible light, was harmful to skin, samarium-cerium compounds containing Sm2O2S were synthesized by co-precipitation method. This kind of compounds blocks not only UV light, but also blue light that is part of visible light. The minimum values of average transmittance (360–450 nm) and band gap of samarium-cerium compounds were 8.90% and 2.30 eV, respectively, which were less than 13.96% and 2.63 eV of CeO2. Elemental analysis (EA), X-ray diffraction (XRD), Fourier transformation infrared (FT-IR), and Raman spectra determined that the samples contained Ce4O7, Sm2O2S, Sm2O3, and Sm2O2SO4. The micro-structure of samples was analyzed by scanning and transmission electron microscopy (SEM, TEM). X-ray photoelectron spectrum (XPS) showed cerium had Ce3+ and Ce4+ valence states, and oxygen was divided into lattice oxygen and oxygen vacancy that was direct cause of the decrease of average transmittance and band gap.

Research Article
Kinetic analysis and modeling of maize straw hydrochar combustion using multi-Gaussian-distributed activation energy model
Chunmei Yu, Shan Ren, Guangwei Wang, Junjun Xu, Haipeng Teng, Tao Li, Chunchao Huang, and Chuan Wang
Available online 18 May 2021, https://doi.org/10.1007/s12613-021-2305-3
[Abstract](148) [PDF 694KB](11)
Abstract:

This study investigates hydrochar combustion kinetics using a multi-Gaussian-distributed activation energy model (DAEM) to expand knowledge on combustion mechanisms. The results demonstrate that the kinetic parameters calculated by the multi-Gaussian-DAEM accurately represented the experimental conversion rate curves. Overall, the feedstock combustion could be divided into four stages: the decomposition of hemicellulose, cellulose, lignin, and char combustion. The hydrochar combustion could in turn be divided into three stages: the combustion of cellulose, lignin, and char. The mean activation energy ranges obtained for the cellulose, lignin, and char of the hydrochar were 273.7–292.8, 301.6–334.5, and 355.2–365.1 kJ/mol, respectively, with standard deviations of 2.1–23.1, 9.5–27.4, and 12.1–22.9 kJ/mol, respectively. The cellulose and lignin contents first increased and then decreased with increasing hydrothermal carbonization (HTC) temperature, while the mass fraction of char gradually increased.

Research Article
Incorporation of nano/micron-SiC particles in Ni-based composite coatings towards enhanced mechanical and anti-corrosion properties
Bowei Zhang, Qiao Zhang, Zhan Zhang, Kui Xiao, Qiong Yao, Guojia Ma, Gang Sun, and Junsheng Wu
Available online 18 May 2021, https://doi.org/10.1007/s12613-021-2307-1
[Abstract](115) [PDF 943KB](6)
Abstract:

Ni-based composite coatings incorporated with nano/micron SiC particles were fabricated via electrochemical co-deposition in Watts bath, followed by the evaluation of their mechanical and anti-corrosion properties. The micrographic observations suggest that the SiC particles with various sizes can be well incorporated to the Ni substrate. X-ray diffraction (XRD) patterns indicate that SiC particles with smaller sizes could weaken the preferential growth of Ni along (2 0 0) facet. In addition, it is found that the incorporated SiC particles with medium micron sizes (8 μm and 1.5 μm) could significantly enhance the micro-hardness of the Ni composite coatings. Nevertheless, electrochemical measurements demonstrate that micron-sized SiC particles would weaken the corrosion resistance of Ni composite coatings ascribed to the structure defects induced. In contrast, the combined incorporation of nanosized (50 nm) SiC particles with medium micron (1.5 μm) ones is capable of promoting the compactness of the composite coatings, which is beneficial to the long-term corrosion resistance with negligible micro-hardness loss.

Research Article
Effect of Al2O3 content on the viscosity and structure of CaO–SiO2–Cr2O3–Al2O3 slags
Fang Yuan, Zheng Zhao, Yanling Zhang, and Tuo Wu
Available online 18 May 2021, https://doi.org/10.1007/s12613-021-2306-2
[Abstract](169) [PDF 1282KB](18)
Abstract:

The effect of Al2O3 on the viscosity and structure of CaO–SiO2–Cr2O3–Al2O3 slags is investigated to facilitate recycling of Cr in steelmaking slags. The slags exhibit good Newtonian behavior at high temperature. The viscosity of acidic slag first increases from 0.825 to 1.141 Pa·s as the Al2O3 content increases from 0 to 10wt% and then decreases to 1.071 Pa·s as the Al2O3 content increases further to 15wt%. The viscosity of basic slag first increases from 0.084 to 0.158 Pa·s as the Al2O3 content increases from 0 to 15wt% and then decreases to 0.135 Pa·s as the Al2O3 content increases further to 20wt%. Furthermore, Cr2O3-containing slag requires less Al2O3 to reach the maximum viscosity than Cr2O3-free slag; the Al2O3 contents at which the behavior changes are 10wt% and 15wt% for acidic and basic slags, respectively. The activation energy of the slags is consistent with the viscosity results. Raman spectra demonstrate that [AlO4] tetrahedra appear initially and are replaced by [AlO6] octahedra with further addition of Al2O3. The dissolved organic phosphorus content of the slag first increases and then decreases with increasing Al2O3 content, which is consistent with the viscosity and Raman results.

Research Article
Significantly improved hydrogen storage behaviors of MgH2 with Nb nanocatalyst
Farai Michael Nyahuma, Liuting Zhang, Mengchen Song, Xiong Lu, Beibei Xiao, Jiaguang Zheng, and Fuying Wu
Available online 13 May 2021, https://doi.org/10.1007/s12613-021-2303-5
[Abstract](169) [PDF 1697KB](8)
Abstract:

The study explores the excellent modification effect of Nb nanocatalyst prepared via surfactant assisted ball milling technique (SABM) on the hydrogen storage properties of MgH2. Optimal catalyst doping concentration was determined by comparing onset decomposition temperature, released hydrogen capacity and reaction rate for different MgH2+ywt% Nb (y = 0, 3, 5, 7, 9) composites. The MgH2+5wt% Nb composite started releasing hydrogen at 186.7℃ and a total of 7.0wt% hydrogen was released in the dehydrogenation process. In addition, 5wt% Nb doped MgH2 also managed to release 4.2wt% H2 within 14 minutes at 250℃ and had the ability to absorb 4.0wt% hydrogen in 30 minutes at 100℃. Cycling tests revealed that MgH2+5wt% Nb could retain 6.3 wt% H2 capacity (89.2%) after 20 cycles. Dehydrogenation and hydrogenation activation energy values were decreased from 140.51±4.74 kJ·mol-1 and 70.67±2.07 kJ·mol-1 to 90.04±2.83 kJ·mol-1 and 53.46±3.33 kJ·mol-1 after doping MgH2 with Nb, respectively. Microstructure analysis proved that homogeneously distributed NbH acted as active catalytic unit for improving the hydrogen storage performance of MgH2. These results indicate SABM can be considered as an option to develop other nanocatalysts for energy related areas.

Research Article
The wetting behavior of CaO-Al2O3-based mold flux with various BaO and MgO contents on steel substrate
Lejun Zhou, Hao Luo, Wanlin Wang, Houfa Wu, Erzhuo Gao, You Zhou, and Daoyuan Huang
Available online 8 May 2021, https://doi.org/10.1007/s12613-021-2300-8
[Abstract](180) [PDF 747KB](19)
Abstract:

The interfacial phenomena in mold have great impact on the smooth operation and the quality of the casting product. In this paper, the wetting behavior of CaO-Al2O3-based mold flux with different BaO and MgO contents was studied. The results show that the contact angle between molten flux and IF steel substrate increased from 62.4o to 74.5o with the increase of BaO content from 3wt% to 7wt%, while it decreased from 62.4o to 51.3o with the increase of MgO content from 3wt% to 7wt%. The interfacial tension also increased from 1630.3 to 1740.8 mN/m when the BaO content increased, but it reduced from 1630.3 to 1539.7 mN/m with the addition of MgO. The changes of contact angle and interfacial tension were mainly due to the fact that the bridging oxygen (O0) at the interface was broken into non-bridging oxygen (O-) and free oxygen (O2-) by MgO. However, more O- and O2- connected into O0 when BaO was added, since the charge compensation effect of BaO was so stronger that it offset the effect of providing O2−.

Research Article
Pyrolysis behaviour and combustion kinetics of waste printed circuit boards
kang Yan, Chongwei Liu, Liping Liu, Min Xiong, Zhongtang Zhang, Shuiping Zhong, Zhifeng Xu, and Jindi Huang
Available online 30 April 2021, https://doi.org/10.1007/s12613-021-2299-x
[Abstract](119) [PDF 1158KB](4)
Abstract:

The effective recycling of waste printed circuit boards (WPCBs) can conserve resources and reduce environmental pollution. This study explores the pyrolysis and combustion characteristics of WPCBs in various atmospheres through thermogravimetric and Gaussian fitting analyses. Furthermore, this study analyses the pyrolysis products and combustion processes of WPCBs through thermogravimetric–Fourier transform infrared and thermogravimetric–mass spectrometry analytical techniques. Results show that the pyrolysis and combustion processes of WPCBs do not constitute a single reaction, but rather, they constitute an overlap of multiple reactions. The pyrolysis and combustion process of WPCBs is divided into multiple reactions by Gaussian peak fitting, and the kinetic parameters of each reaction are obtained by the Coats-Redfern method. In an argon atmosphere, pyrolysis consists of the overlap of the preliminary pyrolysis of epoxy resin, pyrolysis of small organic molecules, and pyrolysis of brominated flame retardants. The reaction mechanism functions are G(α)= (1-α)-1-1, G(α) = (1-α)-1-1 and G(α)= [-(1-α)]4 (α is the conversion rate of the reaction,  G(α) is the mechanism function of the reaction). The combustion of WPCB in oxygen consists of the overlap of the epoxy resin and brominated flame retardant combustion reactions; the reaction mechanism functions are G(α)= ((1-α)-1/3-1)2 and G(α)= ((1-α)-1/3-1)2. This study provided the theoretical basis for pollution control, process optimization and reactor design of WPCBs pyrolysis.


Research Article
Effect of Al content on the reaction between Fe-10Mn-xAl (x=0.035, 0.5, 1, 2 wt%) steel and CaO-SiO2-Al2O3-MgO slag
Hui-xiang Yu, De-xin Yang, Jia-ming Zhang, Guang-yuan Qiu, and Ni Zhang
Available online 28 April 2021, https://doi.org/10.1007/s12613-021-2298-y
[Abstract](123) [PDF 612KB](20)
Abstract:

The effect of Al content (0.035, 0.5, 1 and 2 wt%) on the composition change of steel and slag, as well as inclusion transformation of high manganese steel after equilibrated with CaO-SiO2-Al2O3-MgO slag was studied by method of slag/steel reaction. The experimental results show that, as the initial content of Al increased from 0.035% to 2%, Al gradually replaced Mn to react with SiO2 in slag to avoid the loss of Mn due to the reaction, which caused both Al2O3 in slag and Si in steel to increase, while SiO2 and MnO in slag to reduce. In addition, the type of inclusions also evolved as the initial Al content increased. The evolution route of inclusions was MnO→MnO-Al2O3-MgO→MgO→MnO-CaO-Al2O3-MgO and MnO-CaO-MgO. The shape of inclusions evolved from spherical to irregular, faceted, and finally transformed to spherical. The average size of inclusions presented a trend that was increasing first and then decreasing. The transformation mechanism of inclusions was explored. As the initial content of Al increased, Mg and Ca were reduced from top slag into molten steel in sequence, which consequently caused the transformation of inclusions.

Research Article
Effect of particle micro-structure on the electrochemical properties of LiNi0.8Co0.1Mn0.1O2 cathode material
Ze-xun Tang, Hong-qi Ye, Xin Ma, and Kai Han
Available online 23 April 2021, https://doi.org/10.1007/s12613-021-2296-0
[Abstract](133) [PDF 1375KB](14)
Abstract:

Ni-rich layered material is a kind of high-capacity cathode to meet the requirement of electric vehicles. As for the typical LiNi0.8Co0.1Mn0.1O2 material, the particle formation is significant for electrochemical properties of the cathode. In this work, the structure, morphology and electrochemical performance of LiNi0.8Co0.1Mn0.1O2 secondary particles and single crystals are systematically studied. A lower Ni2+/Ni3+ ratio of 0.66 and a lower residual alkali content of 2280 ppm were achieved on the surface of single crystals. In addition, the single crystals showed a discharge capacity of 191.6 mAh/g at 0.2 C (~12 mAh/g lower than that of the secondary particles) and enhanced electrochemical stability, especially when cycled at 50 °C and in a wider electrochemical window (between 3.0 and 4.4 V vs. Li+/Li). The LiNi0.8Co0.1Mn0.1O2 secondary particles were suitable for applications requiring high specific capacity, whereas single crystals exhibited better stability, indicating that they are more suitable for use in long life requested devices.

Research Article
Simultaneously improving mechanical properties and corrosion resistance of as-cast AZ91 Mg alloy by ultrasonic surface rolling
Jing Han, Cong Wang, Yuan-ming Song, Zhi-yuan Liu, Jia-peng Sun, and Ji-yun Zhao
Available online 23 April 2021, https://doi.org/10.1007/s12613-021-2294-2
[Abstract](184) [PDF 1659KB](28)
Abstract:

Mg alloy casting parts commonly suffer from drawbacks of low surface properties, high susceptibility to corrosion, unsatisfactory absolute strength, and poor ductility, which seriously limit their wide application. Here, a surface nanocrystallization technique, i.e., ultrasonic surface rolling (USR), was applied on an as-cast AZ91 Mg alloy sheet to improve its corrosion resistance and mechanical properties. The USR produces double smooth surfaces with Ra=0.026 μm and gradient nanostructured surface layers on the sheet. Due to this special microstructure modification, the USR sheet exhibits 51% and 50% improvements in tensile yield strength and ultimate strength without visibly sacrificed ductility comparable to its untreated counterpart, as well as a 24% improvement in surface hardness. The USR sheet also shows good corrosion resistance in 3.5% NaCl aqueous solution. The corrosion current density of the USR sheet reduces by 63% after immersion for 1 h, and 25% after immersion for 24 h compared to that of the untreated counterpart. The enhanced strength and hardness are mainly related to the gradient nanostructure. The improved corrosion resistance is mainly ascribed to the decreased surface roughness, nanostructured surface, and residual compressive stress. The present results state that USR is an effective and attractive method to improve multiple properties of Mg alloy casting parts, and thus can be used as an additional and last working procedure to achieve high-performance Mg alloy casting parts.

Research Article
Quantitative micro-electrochemical study of duplex stainless steel 2205 in 3.5wt% NaCl solution
Shuang-yu Cai, Ke-ke Lu, Xin-nan Li, Lei Wen, Fei-fei Huang, and Ying Jin
Available online 20 April 2021, https://doi.org/10.1007/s12613-021-2291-5
[Abstract](237) [PDF 849KB](29)
Abstract:

Duplex stainless steels (DSSs) are suffering from various localized corrosion attacks such as pitting, selective dissolution, crevice corrosion during their service period. It is of great value to quantitatively analyze and grasp the micro-electrochemical corrosion behavior and related mechanism for DSSs on the micrometer or even smaller scales. In this work, scanning Kelvin probe force microscopy (SKPFM) and energy dispersive spectroscopy (EDS) measurements were performed to reveal the difference between the austenite phase and ferrite phase in microregion of DSS 2205. Then traditional electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests were employed for micro-electrochemical characterization of DSS 2205 with different proportion phases in Φ40 μm and Φ10 μm micro holes. Both of them can only be utilized for qualitative or semi-quantitative micro-electrochemical characterization of DSS 2205. Coulostatic perturbation method was employed for quantitative micro-electrochemical characterization of DSS 2205. What is more, the applicable conditions of coulostatic perturbation were analyzed in depth by establishing a detailed electrochemical interface circuit. A series of microregion coulostatic perturbations for DSS 2205 with different proportion phases in Φ10 μm micro holes showed that as the austenite proportion increases, the corresponding polarization resistance of microregion increases linearly.

Research Article
Recover titanium, aluminum, magnesium and separate silicon from titanium-bearing blast furnace slag by sulfuric acid curing-leaching
Long Wang, Liang Chen, Wei-zao Liu, Guo-quan Zhang, Sheng-wei Tang, Hai-rong Yue, Bin Liang, and Dong-mei Luo
Available online 20 April 2021, https://doi.org/10.1007/s12613-021-2293-3
[Abstract](155) [PDF 1339KB](14)
Abstract:

An energy-efficient route was adopted to treat titanium-bearing blast furnace slag (TBBFS) in this study. Titanium, aluminum and magnesium were simultaneously extracted and silicon was separated by sulfuric acid curing in low temperature and low concentration sulfuric acid leaching. The process parameters of sulfuric acid curing TBBFS were systematically studied. Under the optimal conditions, the recovery of titanium, aluminum and magnesium reached 85.96%, 81.17% and 93.82%, respectively. The rapid leaching model was used to limit the dissolution and polymerization of silicon, and the dissolution of silicon was only 3.18%. The mechanism of sulfuric acid curing-leaching was investigated. During the curing process, the reaction occurred rapidly and released heat massively. Under the attack of hydrogen ions, the structure of TBBFS was destroyed, silicate was depolymerized to form filterable silica, and titanium, magnesium, aluminum, and calcium ions were replaced to form sulfates and enriched on the surface of silica particles. Titanium, aluminum, and magnesium were recovered in the leaching solution, and calcium sulfate and silica were enriched in the residue after leaching. This method could effectively avoid the formation of silica sol during the leaching process and accelerate the solid-liquid separation.

Research Article
Influence of process parameters and aging treatment on the microstructure and mechanical properties of AlSi8Mg3 alloy fabricated by selective laser melting
Yao-xiang Geng, Hao Tang, Jun-hua Xu, Yu Hou, Yu-xin Wang, Zhen He, Zhi-jie Zhang, Hong-bo Ju, and Li-hua Yu
Available online 31 March 2021, https://doi.org/10.1007/s12613-021-2287-1
[Abstract](127) [PDF 1808KB](7)
Abstract:
Many studies have investigated the selective laser melting (SLM) of AlSi10Mg and AlSi7Mg alloys, but there is still a lack of researches focused on Al-Si-Mg alloys specifically tailored for SLM. In this work, a novel high Mg-content AlSi8Mg3 alloy was specifically designed for SLM. The results showed that this new alloy exhibited excellent SLM processability with the lowest porosity of 0.07%. Massive lattice distortion led to a high Vickers hardness in samples fabricated at a high laser scanning speed due to the precipitation of Mg2Si nanoparticles from the α-Al matrix induced by high-intensity intrinsic heat treatment during SLM. The maximum microhardness and compressive yield strength of the alloy reached 211±4 HV and 526±12 MPa, respectively. After aging treatment at 150 ℃, the maximum microhardness and compressive yield strength of the samples were further improved to 221±4 HV and 577±5 MPa, respectively. These values are higher than those of most known aluminum alloys fabricated by SLM. This paper provides a new idea for optimizing the mechanical properties of Al-Si-Mg alloys fabricated using SLM.
Research Article
Effects of Mg and La on the evolution of inclusions and microstructure in Ca–Ti treated steel
Lei Wang, Bo Song, Zhan-bing Yang, Xiao-kang Cui, Zhen Liu, Wen-sen Cheng, and Jing-hong Mao
Available online 26 March 2021, https://doi.org/10.1007/s12613-021-2285-3
[Abstract](154) [PDF 1481KB](11)
Abstract:
The evolution of inclusions and the formation of acicular ferrite (AF) in Ca–Ti treated steel were systematically investigated after Mg and La addition. The inclusions in molten steel were Ca–Al–O, Ca–Al–Mg–O and La–Mg–Ca–Al–O after Ca, Mg and La addition, respectively. The type of oxide inclusions in final quenched samples was the same as that in molten steel. However, unlike these in molten steel, inclusions were Ca–Al–Ti–O + MnS, Ca–Mg–Al–Ti–O + MnS and La–Ca–Mg–Al–Ti–O + MnS in Mg-free, Mg-containing and La-containing samples, respectively. The inclusions distributed dispersedly in the La-containing sample. In addition, the average size of the inclusions in the La-containing sample was the smallest while the number density of inclusions was the highest. The size of effective inclusions (nucleus of AF formation) was mainly in the range of 1  to 3 μm. And the content of ferrite side plates (FSP) decreased, while the percentage of acicular ferrite (AF) increased by 16.2% due to the increase in the number of effective inclusions in the La-containing sample in this study.
Research Article
Flotation kinetics performance of different coal size fractions with nanobubbles
Hua Han, An Liu, Cai-li Wang, Run-quan Yang, Shuai Li, and Huai-fa Wang
Available online 6 March 2021, https://doi.org/10.1007/s12613-021-2280-8
[Abstract](323) [PDF 957KB](27)
Abstract:
The flotation kinetics of different size fractions of conventional and nanobubbles (NBs) flotation were compared to investigate the effect of NBs on flotation performance of various coal particle size. Six flotation kinetics models were selected to fit the flotation data and NBs were observed on the hydrophobic surface under hydrodynamic cavitation by atomic force microscope (AFM) scanning. The flotation results indicate that the best flotation performance of size fraction at -0.125+0.074 mm can be obtained either in conventional or NBs flotation, NBs increase the combustible recovery of almost all of the size fractions, but increase the product ash content of -0.25-0.074 mm and reduce the product ash content of -0.045 mm at the same time. The first-order models can both be used to fit the flotation data in conventional and NBs flotation, the classical first-order model is the most suitable one. NBs have an obvious enhancement of flotation rate on coarse size fraction (-0.5+0.25 mm) but decrease the flotation rate of the medium size (-0.25+0.074 mm), the improvement of flotation speed on fine coal particles (-0.074 mm) is probably the reason of the better flotation performance of raw sample flotation.
Research Article
Surface nanobubbles on hydrophobic surface and its implication to flotation
Chen-wei Li, Dan-long Li, Xin Li, Ming Xu, and Hai-jun Zhang
Available online 5 March 2021, https://doi.org/10.1007/s12613-021-2279-1
[Abstract](375) [PDF 1804KB](37)
Abstract:
Nanobubbles play a potential role in the application of fine particles flotation. In this work, the identification of nanoentities was identified with contact mode atomic force microscope (AFM). Meanwhile, the influence of setpoint ratio and amplitude of cantilever and the responses of the formed surface nanobubbles to the fluctuations of pH, salt concentrations, and surfactant concentrations in the slurry, were studied respectively. Nanobubbles were found on highly oriented pyrolytic graphite (HOPG) surface as HOPG was immersed in deionized water in the ambient temperature. The coalescence of nanobubbles occurred under contact mode, which provides strong evidence supporting the gaseous nature of these nanostructures on HOPG. The measuring height of surface nanobubbles decreased with the setpoint ratio (Asetpoint/Afree). The change in concentrations of pH and MIBC shows a negligible influence on lateral size and height of the preexisting surface nanobubbles. The addition of LiCl results in a negligible change in lateral size but an obvious change in height of surface nanobubbles. The present results are expected to provide a valuable reference to understand the properties of surface nanobubbles and design nanobubbles-assisted flotation processes.
Research Article
Hot compressive deformation of eutectic Al-17at% Cu alloy on the interface of the Cu-Al composite plate produced by horizontal continuous casting
Jun Wang, Fan Zhao, Guo-liang Xie, Jia-xuan Xu, and Xin-hua Liu
Available online 3 March 2021, https://doi.org/10.1007/s12613-021-2276-4
[Abstract](202) [PDF 2138KB](14)
Abstract:
On the interface of the Cu-Al composite plate from horizontal continuous casting, the eutectic tissue layer thickness accounts for more than 90% of the total interface thickness, and the deformation in rolling forming plays an important role in the quality of the composite plate. The eutectic tissue material on the interface of the Cu-Al composite plate was prepared by changing the cooling rate of ingot solidification and the deformation in hot compression was investigated. The results show that deformation temperature is over 300 ℃, the softening effect of dynamic recrystallization of α-Al is greater than the hardening effect, and uniform plastic deformation of eutectic tissue is caused. The constitutive equation of flow stress in the eutectic tissue layer was established by Arrhenius hyperbolic-sine mathematics model, providing a reliable theoretical basis for the deformation of the Cu-Al composite plate.
Research Article
Effect of an external magnetic field on improved electroslag remelting cladding process
Zhi-wen Hou, Yan-wu Dong, Zhou-hua Jiang, Zhi-hao Hu, Li-meng Liu, and Kun-jie Tian
Available online 3 March 2021, https://doi.org/10.1007/s12613-021-2277-3
[Abstract](202) [PDF 1357KB](9)
Abstract:
Obtaining a uniform interface temperature field plays a crucial role in the interface bonding quality of bimetal compound rolls. Therefore, in this study, an improved electroslag remelting cladding (ESRC) process using external magnetic field is proposed to improve the uniformity of the interface temperature of compound rolls. The improved ESRC comprises a conventional ESRC circuit and an external coil circuit. A comprehensive 3D model, including multi-physics fields is solved to study the effect of external magnetic field on the multi-physics fields and interface temperature uniformity. The simulated results demonstrate that the non-uniform Joule heat and flow fields cause a non-uniform interface temperature in the conventional ESRC. As for the improved ESRC, the magnetic flux density (Bcoil) along the z-axis is produced by an anticlockwise current of the external coil. The rotating Lorentz force is generated from the interaction between the radial current and axial Bcoil. Therefore, the slag pool flows clockwise, which enhances circumferential effective thermal conductivity. As a result, the uniformity of the temperature field and interface temperature improve. In addition, the magnetic flux density and rotational speed of the simulated results are in good agreement with those of the experimental results, which verifies the accuracy of the improved ESRC model. Therefore, an improved ESRC is efficient for industrial production of the compound roll with a uniform interface bonding quality.
Research Article
Effect of extrusion process on microstructure and mechanical and corrosion properties of biodegradable Mg-5Zn-1.5Y magnesium alloy
Hassan Jafari, Amir Houshang Mojiri Tehrani, and Mahsa Heydari
Available online 27 February 2021, https://doi.org/10.1007/s12613-021-2275-5
[Abstract](360) [PDF 1743KB](20)
Abstract:
The effect of extrusion temperature and ratio on microstructure, hardness, compression, and corrosion behavior of Mg-5Zn-1.5Y alloy were analyzed. The microstructural observations revealed that the cast alloy consists of α-Mg grains, and Mg3Zn6Y and Mg3Zn3Y2 intermetallic compounds, mostly located on the α-Mg grain boundaries. Extruded alloy at higher temperatures showed coarser grain microstructures, whereas those extruded at higher ratios contained finer ones, although more DRXed grains with lower intermetallics were measured at both conditions. Combined conditions of the lower temperature (340°C) and higher ratio (1:11.5) provided higher compressive strengths. However, no significant hardness improvement was achieved. The extrusion process could decrease the corrosion rate of the cast alloy in simulated body fluid for over 80% due to primarily the refined microstructure. The extrusion temperature showed a more pronounced effect on corrosion resistance compared to the extrusion ratio, and the higher the extrusion temperature, the higher the corrosion resistance.
Research Article
Role of trace additions of Ca and Sn in improving the corrosion resistance of Mg-3Al-1Zn alloy
Pan-pan Wang, Hai-tao Jiang, Yu-jiao Wang, Yun Zhang, Shi-wei Tian, Ye-fei Zhang, and Zhi-ming Cao
Available online 18 February 2021, https://doi.org/10.1007/s12613-021-2268-4
[Abstract](263) [PDF 1276KB](11)
Abstract:
The limited wide applicability of commercial Mg alloys is mainly attributed to the poor corrosion resistance. Addition of alloying elements is the simplest and effective method to improve the corrosion properties. Based on the low-cost alloy composition design, the corrosion behavior of commercial Mg-3Al-Zn (AZ31) alloy bearing minor Ca or Sn element was characterized by scanning Kelvin probe force microscopy, hydrogen evolution, electrochemical measurements and corrosion morphology analysis. Results revealed that the potential difference of Al2Ca/α-Mg and Mg2Sn/α-Mg was ∼230±19 mV and ∼80±6 mV, much lower than that of Al8Mn5/α-Mg (∼430±31 mV) in AZ31 alloy, which illustrated that AZ31-0.2Sn alloy performed the best corrosion resistance, followed by AZ31-0.2Ca, while AZ31 alloy exihited the worst corrosion resistance. Moreover, Sn dissolved into matrix obviously increased the potential of α-Mg and participated in the formation of dense SnO2 film at the interface of matrix, while Ca element was enriched in the corrosion product layer, resulting in the corrosion product layer of AZ31-0.2Ca/Sn alloys more compact, stable and protective than AZ31 alloy. Therefore, AZ31 alloy bearing 0.2wt% Ca or Sn element exhibited excellent balanced properties, which is potential to be applied in commercial more comprehensively.
Research Article
Novel confinement combustion method to nanosized WC/C for efficient electrocatalytic oxygen reduction
Peng-qi Chen, Huan Wu, Yun-xiao Tai, Yu-fei Gao, Jia-yu Chen, and Ji-gui Cheng
Available online 4 February 2021, https://doi.org/10.1007/s12613-021-2265-7
[Abstract](337) [PDF 993KB](17)
Abstract:
Nanosized WC/C catalyst was synthesized via a novel ultra-rapid confinement combustion synthesis method. Result showed that the amount of activated carbon (AC) played an important role in the morphology and structure controlling of both the precursor and the final powder. Due to the confinement of the pore structure and large specific surface area of AC, the WC particles synthesized inside the pores of AC had the size of 10-20 nm. When applied to oxygen reduction performance, the half-wave potential was -0.24 V and the electron transfer number was 3.45, which meant that the main reaction process is the transfer of four electrons. The detailed electrocatalytic performance and the underlying mechanism were investigated in this work. Our study provides a novel approach for the design of new composition and structure catalysts which has a certain significance for promoting the commercialization of fuel cells.
Research Article
Effects of Nd on microstructure and mechanical properties of as-cast Mg-12Gd-2Zn-xNd-0.4Zr alloys with stacking faults
Li-xin Hong, Rong-xiang Wang, and Xiao-bo Zhang
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2264-8
[Abstract](292) [PDF 1451KB](6)
Abstract:
In order to study the effects of Nd addition on microstructure and mechanical properties of Mg-Gd-Zn-Zr alloys, the microstructure and mechanical properties of the as-cast Mg-12Gd-2Zn-xNd-0.4Zr (x = 0, 0.5, and 1 wt%) alloys were investigated by using optical microscope, scanning electron microscope, X-ray diffractometer, nano indentation tester, microhardness tester, and tensile testing machine. The results show that the microstructures mainly consist of α-Mg matrix, eutectic phase and stacking faults. The addition of Nd plays a significant role in grain refinement and uniform microstructure. The tensile yield strength and microhardness increase but the compression yield strength decreases with increasing Nd addition, leading to weakening tension-compression yield asymmetry in reverse of the Mg-12Gd-2Zn-xNd-0.4Zr alloys. The highest ultimate tensile strength (194 MPa) and ultimate compression strength (397 MPa) are obtained with 1 wt% Nd addition of the alloy.
Research Article
Blast furnace ironmaking process with super high TiO2 in the slag: Density and surface tension of the slag
Zheng-de Pang, Yu-yang Jiang, Jia-wei Ling, Xue-wei Lv, and Zhi-ming Yan
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2262-x
[Abstract](307) [PDF 886KB](26)
Abstract:
Considering high novelty and potential on ultra–high (>80%) or full V–Ti–Magnetite ore under blast furnace smelting, we are conducting a series of works on physics character of high TiO2 bearing blast furnace slag (BFS) for slag optimization. This work discussed the density and surface tension of high TiO2 bearing BFS using the Archimedean principle and the maximum bubble pressure method, respectively. The influence of TiO2 content and MgO/CaO (mass ratio) on the density and surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags were investigated. Results indicated that the density of slags decreased as increasing TiO2 content from 20 to 30 wt%, but it increased slightly as increasing MgO/CaO from 0.32 to 0.73. In view of silicate network structure, the density and the degree of polymerization (DOP) of network structure have a consistent trend. The addition of TiO2 reduces (Q3)2/(Q2) ratio, decreases DOP, which leads to the decrease of slag density. The surface tension of CaO–SiO2–TiO2–MgO–Al2O3 slags decreased dramatically as increasing TiO2 content from 20 to 30 wt%. Conversely, it increased as increasing MgO/CaO from 0.32 to 0.73. Furthermore, the iso–surface tension lines were obtained under 1723K using the Tanaka developed model in view of Butler formula. It may be useful for slag optimization of ultra–high proportion (>80%) or even full V–Ti–Magnetite ore under BF smelting.
Research Article
Experimental investigation on the intermetallic growth behavior during post deformation annealing in multilayer Ti/Al/Nb composite interfaces
Roya Jafari and Beitallah Eghbali
Available online 2 February 2021, https://doi.org/10.1007/s12613-021-2263-9
[Abstract](313) [PDF 1498KB](3)
Abstract:
In the present research, the tri-metal Ti-Al-Nb composites were processed through three procedures: hot pressing, rolling, and hot pressing, followed by subsequent rolling. The fabricated composites were then subjected to annealing at 600, 625, and 650 ºC temperatures at different times. Microstructure observation at the interfaces reveals that the increase in plastic deformation strain significantly affects TiAl3 intermetallic layers’ evolution and accelerates the layers’ growth. On the contrary, the amount of applied strain does not significantly affect the evolution of the NbAl3 intermetallic layer thickness. It was also found that Al and Ti atoms’ diffusion has occurred throughout the TiAl3 layer, but only Al atoms diffuse through the NbAl3 layer. The slow growth rate of the NbAl3 intermetallic layer is due to the lack of diffusion of Nb atoms and the high activation energy of Al atoms’ reaction with Nb atoms.
Invited Review
A review of the synthesis and application of zeolites from coal-based solid wastes
Xiao-yu Zhang, Chun-quan Li, Shui-lin Zheng, Yong-hao Di, and Zhi-ming Sun
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2256-8
[Abstract](424) [PDF 870KB](19)
Abstract:
Zeolite derived from coal-based solid wastes (coal gangue and coal fly ash) not only can cope with the environmental problems caused by coal-based solid wastes but also achieve their valuable utilization. In this paper, the physicochemical properties of coal gangue and coal fly ash were introduced. Then the mechanism and application characteristics of the pretreatment processes for zeolite synthesis from coal-based solid wastes were introduced as well. After that, the synthesis processes of coal-based solid waste zeolite and their merits and demerits were summarized in detail. Furthermore, the application characteristics of various coal-based solid waste zeolites and their common application fields were also illustrated. By the end of this review, we propose that alkaline fusion-assisted supercritical hydrothermal crystallization may be an efficient method for synthesizing coal-based solid waste zeolites. Besides, more attention should be paid to the recycling of alkaline waste liquid and the application of coal-based solid waste zeolites in the field of volatile organic compounds adsorption removal.
Research Article
Analysis of local microstructure and strengthening mechanisms in adjustable-gap bobbin tool friction stir welds of Al-Mg
Dong Wu, Wen-ya Li, Qiang Chu, Yang-fan Zou, Xi-chang Liu, and Yan-jun Gao
Available online 22 January 2021, https://doi.org/10.1007/s12613-021-2254-x
[Abstract](344) [PDF 1218KB](11)
Abstract:
The bobbin tool friction stir welding process was used to join 6 mm thick 5A06 aluminum alloy plates. Optical microscope was used to characterize the microstructure. The electron backscatter diffraction (EBSD) identified the effect of non-homogeneous microstructure on the tensile properties. It was observed that the grain size in the top of the stir zone (SZ) is smaller than that in the centre region. The lowest ratio of recrystallization and density of the geometrically-necessary dislocations (GNDs) in the SZ was found in the middle near the thermo-mechanically affected zone (TMAZ) being 22% and 1.15×10-13 m-2, respectively. The texture strength of the heat-affected zone (HAZ) is the largest, followed by that in the SZ, with the lowest being in the TMAZ. There were additional interfaces developed which contributed to the strengthening mechanism, and their effect on tensile strength was analysed. The tensile tests identified the weakest part in the joint at the interfaces, and the specific reduction value is about 93MPa.
Research Article
Effects of heat treatments on microstructures of TiAl alloys
Wen Yu, Jian-xin Zhou, Ya-jun Yin, Zhi-xin Tu, Xin Feng, Hai Nan, Jun-pin Lin, and Xian-fei Ding
Available online 16 January 2021, https://doi.org/10.1007/s12613-021-2252-z
[Abstract](444) [PDF 1841KB](21)
Abstract:
This study aims to investigate the effects of heat treatments on microstructures of γ-TiAl alloys. Two Ti-47Al-2Cr-2Nb alloy ingots were manufactured by casting method and then heat treated in two types of heat treatments. Their microstructures were studied by both optical and scanning electron microscopies. The chemical compositions of two ingots were determined. The ingot with lower Al content only obtains lamellar structures while the one higher in Al content obtains nearly lamellar and duplex structures after heat treatment within 1270°C to 1185°C. A small amount of B2 phase is found to be precipitated in both as-cast and heat-treated microstructures. They are distributed at grain boundaries when holding at a higher temperature, such as 1260°C. However, B2 phase is precipitated at grain boundaries and in colony interiors simultaneously after heat treatments happened at 1185°C. Furthermore, the effects of heat treatments on grain refinement and other microstructural parameters are discussed.
Research Article
Combining the 8-hydroxyquinoline intercalated layered double hydroxide film and sol-gel coating for active corrosion protection of the magnesium alloy
Yahya Jafari Tarzanagh, Davod Seifzadeh, and Roghaye Samadianfard
Available online 16 January 2021, https://doi.org/10.1007/s12613-021-2251-0
[Abstract](396) [PDF 1853KB](9)
Abstract:
The 8-Hydroxyquinoline (8-HQ) intercalated Layered Double Hydroxides (LDH) film as underlayer and sol-gel layer was combined for active corrosion protection of the AM60B magnesium alloy. The LDH, LDH/sol-gel, and LDH@HQ/sol-gel coatings were analyzed using the SEM, FESEM, EDX, XRD, AFM, and EIS methods. The SEM images showed that the surface was entirely coated by the LDH film composed of vertically-grown nanosheets. The same morphology was observed for the LDH/sol-gel and LDH@HQ/sol-gel coatings. Also, almost the same topography was observed for both composite coatings except that the LDH@HQ/sol-gel coating had relatively higher surface roughness. Although the LDH film had the same impedance behavior as the alloy sample in 3.5 wt. % NaCl solution, its corrosion resistance was much higher, which could be due to its barrier properties as well as to the trapping of the chloride ions. Similar to the LDH film, the corrosion resistance of the LDH/sol-gel composite diminished with increasing the exposure time. However, its values were much higher than that of the LDH film, which was mainly related to the sealing of the solution pathways. The LDH@HQ/sol-gel composite showed much better anti-corrosion properties than the LDH/sol-gel coating due to the adsorption of the 8-HQ on the damaged areas through the complexation.
Research Article
Evolution laws of microstructures and mechanical properties during heat treatments for near-α high temperature titanium alloys
Xiao-zhao Ma, Zhi-lei Xiang, Tao Li, Yi-lan Chen, Ying-ying Liu, Zi-yong Chen, and Qun Shu
Available online 6 January 2021, https://doi.org/10.1007/s12613-021-2248-8
[Abstract](346) [PDF 1799KB](6)
Abstract:
Evolution laws of microstructures, mechanical properties and fractographs after different solution temperatures were investigated through various analyses methods. With the increasing solution temperatures, contents of primary α phase decreased, and contents of transformed β structures increased. Lamellar α grains dominated the characteristics of transformed β structures, and widths of secondary α lamellas increased monotonously. For as-forged alloy, large silicides with equiaxed and rod-like morphologies, and nano-scale silicides were found. Silicides with large sizes might be (Ti, Zr, Nb)5Si3 and (Ti, Zr, Nb)6Si3. Rod-like silicides with small sizes precipitated in retained β phase, exhibiting near 45° angles with α/β grain boundaries. Retained β phases in as-heat treated alloys were incontinuous. 980STA exhibited excellent combinations of room temperature (RT) and 650℃ mechanical properties. Characteristics of fracture surfaces largely depended on the evolutions of microstructures. Meanwhile, silicides promoted the formation of mico-voids.
Research Article
Synthesis of amino functionalized diatomite by glycine and amino silane for high-efficient removal of indoor formaldehyde
Yong-hao Di, Fang Yuan, Xiao-tian Ning, Hong-wei Jia, Yang-yu Liu, Xiang-wei Zhang, Chun-quan Li, Shui-lin Zheng, and Zhi-ming Sun
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2245-3
[Abstract](455) [PDF 1105KB](20)
Abstract:
In order to remove indoor formaldehyde (HCHO) efficiently and cheaply, two kinds of novel amino functionalized diatomite (DE) modified by 3-aminopropyltriethoxysilane (APTS) and glycine (GLY) (i.e. APTS/DE and GLY/DE) were successfully synthesized by wetting chemical method. First, the optimal preparation conditions of the two kinds of amino modified diatomite were determined, and then their microstructure and morphologies were characterized and analyzed. For comparation, a series of batch HCHO adsorption experiments of the two kinds of amino modified diatomite were conducted. According to the experimental results, the pseudo-second-order kinetic model and the Langmuir isotherm model could well describe the adsorption processes, and the maximum adsorption capacity of APTS/DE and GLY/DE prepared under the optimized conditions at 20 ℃ were 5.83 and 1.14 mg·g-1, respectively. In addition, the thermodynamic parameters indicated that the adsorption process is a spontaneous and exothermic process. Overall, the abundant amine groups grafting on the surface of diatomite was derived from Schiff base reaction, which is essential for high-efficient adsorption performance toward HCHO.
Research Article
Mechanical properties of Al-15Mg2Si composites prepared under different solidification cooling rates
Elahe Safary, Reza Taghiabadi, and Mohammad Hosein Ghoncheh
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2244-4
[Abstract](453) [PDF 1571KB](17)
Abstract:
The effect of different cooling rates (2.7, 5.5, 17.1, and 57.5 °C/s) on the solidification parameters, microstructure, and mechanical properties of Al-15Mg2Si composites was studied. The results showed that, high cooling rate refined the Mg2Si particles and changed their morphology to the more compacted forms with less microcracking tendency The average radius and fraction of primary Mg2Si particles decreased from 20 µm and 13.5% to about 10 µm and 7.3%, respectively, as the cooling rate increased from 2.7 °C/s to 57.5 °C/s. Increasing the cooling rate also improved the distribution of microconstituents, decreased the size of grains, and reduced the volume fraction of micropores. The mechanical properties results revealed that augmenting the cooling rate from 2.7 °C/s to about 57.5 °C/s increased the hardness and quality index by 25% and 245%, respectively. High cooling rate also changed the fracture mechanism from brittle dominated to a high-energy ductile mode comprising of extensive dimpled zones.
Research Article
Reciprocating sliding wear properties of sintered Al-B4C composites
Mahmut Can ŞENEL, Yusuf Kanca, and Mevlüt Gürbüz
Available online 29 December 2020, https://doi.org/10.1007/s12613-020-2243-5
[Abstract](429) [PDF 1698KB](23)
Abstract:
Pure aluminum and boron carbide reinforced aluminum matrix composites with various content (1, 6, 15, 30 wt.%B4C) were fabricated using the powder metallurgy technique. The influence of boron carbide amount on the mechanical and tribological behavior of sintered Al-B4C was examined. The highest density (~2.54 g/cm3), lowest porosity (4%), maximum Vickers hardness (~75 HV), as well as, lowest weight loss (0.4 mg), and lowest specific wear rate (0.00042 mm3/Nm) under a 7 N load were obtained with Al-30B4C composites. Enhancement of 167% in hardness, a decrease of 75.8% in weight loss, and a decrease of 76.7% in specific wear rate under an applied load of 7 N were determined when compared with pure aluminum. Similarly, the SEM images of the worn surface revealed that the narrowest wear grove (0.85 mm) at a load of 7 N was detected at Al-B4C composite and the main wear mechanism was observed as an abrasive wear mechanism. According to the friction analysis, the coefficient of friction between surfaces increased with increasing boron carbide content and decreasing the applied load. In conclusion, boron carbide is an effective reinforcement material in terms of tribological and mechanical performance of Al-B4C composites.
Research Article
Mechanical properties and energy evolution of jointed rock specimens containing an opening under uniaxial loading
Peng Li, Mei-feng Cai, Pei-tao Wang, Qi-feng Guo, Sheng-jun Miao, and Fen-hua Ren
Available online 12 December 2020, https://doi.org/10.1007/s12613-020-2237-3
[Abstract](457) [PDF 866KB](5)
Abstract:
For investigating the impact of an opening and joints with different inclination angles on the mechanical response behavior, the energy evolution characteristics and distribution law of granite specimens, uniaxial loading tests were performed on the parallel jointed rock samples with an opening. The results indicate that there is a trend of first decreasing and then increasing of the strength and deformation parameters with the increase of inclination angle, reaching the minimum values when the inclination angle was 45°. The evolution curves of the elastic strain energy and dissipated energy with strain of the samples show the characteristics of step-like gradual mutation. The peak total energy, elastic strain energy, dissipated energy, and total input energy during the failure of the samples showed significant nonlinear characteristics with increasing inclination angle. The opening and joints as well as the change of the inclination angle had significant influences on the proportion of the elastic strain energy of the samples prior to the peak, resulting in the difference of the distribution law of input energy. Moreover, the energy mechanism of the sample failure was discussed, and the energy release was the internal cause of the sudden destruction of the entire rock mass.
Research Article
Interfacial bonding characteristics and mechanical properties of H68/AZ31B clad plate
Ting-ting Zhang, Wen-xian Wang, Jie Zhang, and Zhi-feng Yan
Available online 12 December 2020, https://doi.org/10.1007/s12613-020-2240-8
[Abstract](379) [PDF 2205KB](1)
Abstract:
Interfacial bonding, microstructures and mechanical properties of an explosively-welded H68/AZ31B clad plate were systematically studied. It was found that the bonding interface demonstrated a “like-wavy” structure containing three typical zones/layers: 1) diffusion layer adjacent to the H68 brass plate; 2) solidification layer of melted metals at the interface; and 3) a layer at the side of AZ31B alloy which experienced severe deformation. Mixed copper, CuZn2 and α-Mg phases were observed in the melted-solidification layer. Regular polygonal grains with twins were found at the H68 alloy side while fine equiaxed grains due to the recrystallization were found at the AZ31B alloy side near the interface. Nanoindentation results revealed the formation of brittle intermetallic CuZn2 phases at the bonding interface. The interface was bonded well through metallurgical reactions owing to the diffusion of Cu, Zn and Mg atoms across the interface and the metallurgic reaction of partially melted H68 and AZ31B alloys.
Research Article
Microstructure and mechanical properties of friction pull plug welding for 2219-T87 aluminum alloy with the tungsten inert gas weld
Zhen Shao, Lei Cui, Li-jun Yang, Peng Lu, Hui-miao Wang, Zhuan-ping Sun, and Jian-ling Song
Available online 11 November 2020, https://doi.org/10.1007/s12613-020-2222-x
[Abstract](559) [PDF 1595KB](7)
Abstract:
Friction pull plug welding (FPPW) of 2219-T87 Tungsten Inert Gas (TIG) welded joint was studied. The microstructures, precipitate evolution, mechanical properties, and fracture morphologies of the joint were analyzed and discussed. Defect-free joints were obtained by using 7,000 r/min rotational speed, 12 mm axial feeding displacement and 20–22 kN axial force. It was found that, within the welding parameters as mentioned above, metallurgical bonding between the plug and plate can be achieved by the formation of recrystallized grains. According to the different microstructural features, the FPPW joint can be divided into different regions, including such as heat-affected zone (HAZ), thermo-mechanically affected zone (TMAZ), recrystallization zone, heat-affected zone in TIG weld (TIG-HAZ), and thermo-mechanically affected zone in TIG weld (TIG-TMAZ). In TIG-TMAZ, the grains were highly deformed and elongated owing to the shear and extrusion form the plug during FPPW process. The hardness distribution showed that TIG-TMAZ was the area with the lowest strength. The main reason of softening in TMAZ was identified as the dissolution of θ' and the coarsening of θ precipitate particles. In tensile test, the FPPW joint welded with 22 kN axial force showed the highest ultimate tensile strength of 237 MPa. The location of crack and facture was found in TIG-TMAZ. The fracture morphology of the tensile sample showed good plasticity and toughness.
Research Article
Wear behavior of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite with different stabilization treatments
Sheng Liu, Qing Yuan, Yu-tong Sima, Chen-xi Liu, Fang Han, and Wen-wei Qiao
Available online 4 November 2020, https://doi.org/10.1007/s12613-020-2217-7
[Abstract](588) [PDF 2041KB](6)
Abstract:
Zn-38Al-3.5Cu-1.2Mg composite reinforced by nano SiCp was fabricated by stirring assisted ultrasonic vibration. In order to improve the abrasive resistance of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite, several stabilization treatments with distinct solid solutions and aging temperatures were designed. The results indicate that the optimal stabilization treatment for the 38Al-3.5Cu-1.2Mg/SiCp composite involves a solution treatment at 380 °C for 6 h and aging at 170 °C for 48 h. The stabilization treatment leads to the formation of dispersive and homogeneous nano SiCp. During the friction wear condition, the nano SiCp limits the microstructure evolution from the hard α(Al, Zn) phase to the soft β(Al, Zn) phase. Besides, the increased amount of nano SiCp improves the grain dimension and contributes to abrasive resistance. Furthermore, the initiation and propagation of crack produced in the friction wear process are suppressed by the stabilization treatment, thereby improving the abrasive resistance of the Zn-38Al-3.5Cu-1.2Mg/SiCp composite.
Research Article
Phase evolution and properties of glass ceramic foams prepared by bottom ash, fly ash and pickling sludge
Jun-jie Zhang, Xiao-yan Zhang, Bo Liu, Christian Ekberg, Shi-zhen Zhao, and Shen-gen Zhang
Available online 4 November 2020, https://doi.org/10.1007/s12613-020-2219-5
[Abstract](658) [PDF 1348KB](8)
Abstract:
Municipal solid waste incineration bottom ash (BA), fly ash (FA) and pickling sludge (PS), causing severe environmental pollution, were transformed into glass ceramic foams with the aid of CaCO3 as the pore-foaming agent by sintering in this paper. The effect of BA/FA ratio on the phase composition, pore morphology, pore size distribution, physical properties, glass structure unit of the samples was investigated, with results showing that with the increase of BA/FA ratio, the content of glass phase, Si-O-Si and Q3Si units decrease gradually. The glass transmission temperature of the mixture has also been reduced. These leads to the decrease of the glass viscosity, further causing bubble coalescence and uneven pore distribution. Glass ceramic foams with uniform spherical pores (average pore size of 106 μm) would be fabricated, when the content of BA, FA and PS were 35wt%, 45wt% and 20wt% respectively, contributing to the glass ceramic foams of high performance with bulk density of 1.76 g/cm3, porosity of 56.01% and compressive strength exceeding 16.23 MPa. This versatile and low-cost approach brings new insight of synergistically recycling solid wastes.
Research Article
Enhanced detection of ppb-level NO2 by uniform Pt-doped ZnSnO3 nanocubes
Yao-yu Yin, Yan-bai Shen, Si-kai Zhao, Ang Li, Rui Lu, Cong Han, Bao-yu Cui, and De-zhou Wei
Available online 21 October 2020, https://doi.org/10.1007/s12613-020-2215-9
[Abstract](839) [PDF 913KB](20)
Abstract:
ZnSnO3 nanocubes (ZSNCs) with various Pt concentrations (1at%, 2at%, and 5at%) were synthesized by the high-yield and facile one-pot hydrothermal method. The microstructures of the obtained products were characterized by XRD, FESEM, TEM, EDS and XPS. The results showed that the ZSNCs with perovskite structure are approximately 600 nm in side length, and this size was reduced to 400 nm after Pt doping. PtOx (PtO and PtO2) nanoparticle with the diameter of about 5 nm were uniformly coated on the surface of ZSNCs. NO2 sensing properties showed that 1% Pt-ZSNCs exhibited the highest response to NO2 than pure ZSNCs and Pt-ZSNCs with other Pt concentrations. The maximum response of 1 at% Pt-ZSNCs to 500 ppb NO2 was 16.0 at the optimal operating temperature of 125 °C, which was over 11 times higher than that of pure ZSNCs. The enhanced NO2 sensing mechanisms of Pt-ZSNCs were discussed in consideration of catalytic activities and chemical sensitization of Pt doping.
Research Article
Numerical simulation of flash reduction process in a drop tube reactor with variable temperature
Yi-ru Yang, Qi-peng Bao, Lei Guo, Zhe Wang, and Zhan-cheng Guo
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2210-1
[Abstract](818) [PDF 926KB](44)
Abstract:
A computational fluid dynamics (CFD) model was developed to accurately predicate the flash reduction process, which is considered to be an efficient alternative ironmaking process. Laboratory-scale experiments were conducted in drop tube reactors (DTRs) to verify the accuracy of the CFD model. The reduction degree of ore particles was selected as a critical indicator of model prediction, and the simulated and experimental results were in good agreement. The influencing factors, including the particle size (20–110 μm), peak temperature (1250–1550 °C), and reductive atmosphere (H2/CO), were also investigated. The height variation lines indicated that smaller particles (50 μm) had a longer residence time (3.6 s). CO provided a longer residence time (~1.29 s) compared with H2 (~1.09 s). However, both the experimental and analytical results show that the reduction degree of particles in CO atmosphere only reached 60%, significantly lower than that in H2 atmosphere, even at the highest temperature (1550 °C). The optimum experimental particle size and peak temperature for the preparation of high-quality reduced iron were found to be 50 μm and 1350 °C in H2 atmosphere and 40 μm and 1550 °C in CO atmosphere, respectively.
Research Article
Two refractory high-entropy alloys CrHfNbTaTi and CrHfMoTaTi: Phase, microstructure and compressive properties
Jiao-jiao Yi, Fu-yang Cao, Ming-qin Xu, Lin Yang, Lu Wang, and Long Zeng
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2214-x
[Abstract](888) [PDF 689KB](36)
Abstract:
Two new refractory high-entropy alloys, CrHfNbTaTi and CrHfMoTaTi, deriving from the well-known HfNbTaTiZr alloy by principal element substitutions, were prepared by vacuum arc-melting. Their phase components, microstructures, and compressive properties in the as-cast state were investigated intensively. The results showed that both alloys are mainly composed of a BCC and cubic laves phase. In terms of the mechanical properties, the yield strength increased remarkably from 926 MPa of HfNbTaTiZr to 1258 MPa of CrHfNbTaTi, meanwhile a promising ductility of around 24.3 % elongation was retained. The morphology and composition of the network-shape interdendritic regions were closely related to the improvement in mechanical properties deduced by elemental substitution. Whereas, dendritic surrounded by the incompact interdendritic shell at the case of the incorporation of Mo deteriorates the yield strength, and results in a typical brittle feature.
Research Article
Enhanced microstructural and mechanical properties of Stellite/WC nanocomposite on Inconel 718 deposited through vibration-assisted laser cladding
Hossein Hosseini-Tayeb and Seyed Mahdi Rafiaei
Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2211-0
[Abstract](880) [PDF 1803KB](11)
Abstract:
Stellite-21/WC nanopowders were deposited on Inconel using vibration-assisted laser cladding through different laser parameters. To study about the microstructural and mechanical behaviors, optical and scanning electron microscopes, hardness measurements, and wear characterizations were employed. The results showed that the variation of cooling rate resulted in remarkable effects on the microstructure of the as-cladded composites. Moreover, increasing the laser power from 150 W to 250 W increased the heat input and the dilutions. Also, in the higher power of the laser (i.e. 250 W), dilution was affected by two factors that were scanning rate and powder feeding rate. Through the addition of WC nanoparticles as the reinforcement, the dilution magnitude intensified while the hardness value surprisingly increased from 350 to 700 HV. The wear characterizations indicated that the composites containing 3 wt% WC nanoparticles possessed the highest wear resistance.
Research Article
Effects of mechanical vibration on physical, metallurgical and mechanical properties of cast-A308 (LM21) aluminum alloy
Siddharth Yadav, S.P. Tewari, J.K. Singh, and S.C. Ram
Available online 14 October 2020, https://doi.org/10.1007/s12613-020-2209-7
[Abstract](896) [PDF 1556KB](27)
Abstract:
The present investigation deals with the improvement in microstructure, physical, and mechanical properties of die-cast A308 alloy subjected to mechanical vibration during solidification. The different frequencies (0, 20, 30, 40, and 50 Hz) at constant amplitude (31 μm) were employed using a power amplifier as the power input device. X-ray diffractometer, optical microscopy, and scanning electron microscopy were used to examine the morphological changes in the cast samples under stationary and vibratory conditions. Metallurgical features of castings were evaluated by ImageJ analysis software. The average values of metallurgical features, i.e., primary α-Al grain size, dendrite arm spacing (DAS), avg. area of eutectic silicon, aspect ratio, and percentage porosity were reduced by 34, 59, 56, 22, and 62% respectively at 30 Hz frequency compared to stationary casting. The mechanical tests of cast samples showed that yield strength, ultimate tensile strength, elongation, and microhardness were increased by 8, 13, 17, and 16%, respectively, at 30 Hz frequency compared to stationary casting. The fractured surface of tensile specimens exhibited mixed-mode fracture behavior due to the appearance of brittle facets, cleavage facets, ductile tearing, and dimple morphologies. The presence of small dimples showed some plastic deformation occurred before fracture.
Research Article
Influence of polymer solution on the morphology and local structure of NH4ZnPO4 powders synthesized by a simple precipitation method at room temperature
Santi Phumying, Thongsuk Sichumsaeng, Pinit Kidkhunthod, Narong Chanlek, Jessada Khajonrit, Somchai Sonsupap, and Santi Maensiri
Available online 13 October 2020, https://doi.org/10.1007/s12613-020-2208-8
[Abstract](804) [PDF 1416KB](20)
Abstract:
In this work, NH4ZnPO4 powders were synthesized by a simple precipitation method at room temperature. The effect of PVP, PVA, sucrose and CTAB solution on the morphology and structure of the prepared samples was investigated. The phase composition and morphology of the prepared samples were characterized by using X-ray diffraction and scanning electron microscopy, respectively. Depending on the polymer sources, the hexagonal structure prepared by using non-surfactant of water completely changed to monoclinic structure when CTAB was added into the process. X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) was used to study the local structure and surface electronic structure of the prepared samples confirming that the oxidation states of P and Zn ions are 5+ and 2+, respectively. By using ICP-OES technique, our NH4ZnPO4 powders can be classified as a slow-release fertilizer where less than 15% of the ions was released in 24 h. This study shows that a simple precipitation method using water, PVP, PVA, sucrose and CTAB as a template can be used to synthesize NH4ZnPO4 powders. In addition, this method may be extended for the preparation of other oxide materials.
Research Article
The activity coefficient of nickel oxide in SiO2 saturated MnO-SiO2 slag and Al2O3 saturated MnO-SiO2-Al2O3 slag at 1623K
Guo-xing Ren, Song-wen Xiao, Cai-bin Liao, and Zhi-hong Liu
Available online 1 October 2020, https://doi.org/10.1007/s12613-020-2205-y
[Abstract](1262) [PDF 620KB](41)
Abstract:
As a part of the fundamental study related to the reduction smelting of both spent lithium-ion batteries and polymetallic sea nodules based on MnO-SiO2-based slags, the activity coefficient of nickel oxide in SiO2 saturated MnO-SiO2 slag and Al2O3 saturated MnO-SiO2-Al2O3 slag at 1623 K was investigated with controlled oxygen partial pressure of 10-7, 10-6, and 10-5 Pa. The results show that the solubility of nickel oxide in the slags increased with increasing the oxygen partial pressure. The nickel in both MnO-SiO2 slag and MnO-SiO2-Al2O3 slag existed as NiO under experimental conditions. The addition of Al2O3 in the MnO-SiO2 slag decreased the dissolution of Ni in the slag, and increased the activity coefficient of NiO. Furthermore, the activity coefficient of NiO, referred to solid NiO, can be calculated as: γNiO=8.58(wt% NiO in slag) + 3.18 (SiO2 saturated MnO-SiO2 slag, 1623K);γNiO=11.06(wt% NiO in slag) + 4.07 (Al2O3 saturated MnO-SiO2-Al2O3 slag, 1623K).
Research Article
Parametric study of spark plasma sintering of Al20Cr20Fe25Ni25Mn10 high entropy alloy with improved microhardness and corrosion
Andries Mthisi, Nicholus Malatji, A. Patricia I. Popoola, and L. Rudolf Kanyane
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2200-3
[Abstract](1214) [PDF 1157KB](20)
Abstract:
Multicomponent Al20Cr20Fe25Ni25Mn10 alloys were synthesized using spark plasma sintering at temperatures (800 °C, 900 °C and 1000 °C) and holding times (4, 8 and 12 minutes), with aim to develop a high entropy alloy (HEA). The characteristics of spark plasma synthesized (SPSed) alloys were experimental explored through investigation of microstructures, microhardness and corrosion using scanning electron microscope coupled with energy dispersive spectroscopy, Vickers microhardness tester and potentiodynamic polarization respectively. Also, X-ray diffractometry characterization was employed to identify the phases formed on the alloys developed. The EDS results revealed that the alloys consist of elements selected in this work irrespective of varying the sintering parameters. Also, the XRD, EDS and SEM collectively provided evidence that the fabricated alloys are characterized by globular microstructures exhibiting FCC phase formed on a basis of solid solution mechanism; this implies that SPSed alloy shows features of HEAs. The alloy produced at 1000 °C and holding time 12 minutes portrayed an optimal microhardness of 447.97 HV, however, this microhardness decreased to 329.47 HV after heat treatment. The same alloy showed outstanding corrosion resistance performance. Increase in temperature resulted in Al20Cr20Fe25Ni25Mn10 alloy with superior density, microhardness and corrosion resistance over other alloys developed at different parameters.
Research Article
Effect of cermet substrates characteristics on the microstructure and properties of TiAlN coating
Qian-bing You, Ji Xiong, Tian-en Yang, Tao Hua, Yun-liang Huo, and Jun-bo Liu
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2198-6
[Abstract](1284) [PDF 2398KB](39)
Abstract:
The composition and structure of substrate material have an important influence on the coating performances, especially the bonding strength and coating hardness,which determines whether the coating can be used. In the paper, the TiAlN coating was deposited on the TC with 0-20wt.% WC by arc ion plating. The influence of cermet substrates characteristics on the structure and properties of TiAlN coating was researched. The results show that TiAlN coating deposited on TC substrates has columnar grain structure. With the increasing of WC, the strength ratio of I(111)/I(200) of TiAlN and the adhesion gradually increases. When there is no WC in the substrate, the preferred orientation of TiAlN coating is (200). As the contents of WC go up, the preferred orientation of TiAlN coating becomes (111) and (200). The biggest difference between the adhesion strength of coating and substrate is the microstructure and composition of the substrate. Scratching results show that the adhesion of TiAlN coating gradually increases from A1 to A5 respectively 53N, 52 N, 56 N, 65 N, 58 N. The coating on the TC substrate with 15wt.% WC has the highest H/E and H3/E2, which indicating the best wear resistance. The failure mechanisms of coated tools are coating peeling, adhesive wear, and abrasive wear. As the cutting speed increases, the amount ofthe flank wear increases, and the durability decreases accordingly. Accompanied by the increasing of WC, the flank wear of coated cermet insert decreases first and then increases. 
Research Article
Effect of graphene-oxide on corrosion, mechanical and biological properties of Mg-based nanocomposite
Saeid Jabbarzare, Hamid Reza Bakhsheshi-Rad, Amir Abbas Nourbakhsh, Tahmineh Ahmadi, and Filippo Berto
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2201-2
[Abstract](1326) [PDF 2126KB](28)
Abstract:
The purpose of this paper is to investigate the role of graphene oxide (GO) on mechanical and corrosion behaviors, antibacterial performance, and cell response of Mg-Zn-Mn (MZM) composite. MZM/GO nanocomposites were made with various amounts of GO (0.5, 1.0, and 1.5 wt.%) by the semi powder metallurgy method. The GO influence on the MZM composite was analyzed by hardness, compressive and corrosion tests, and antibacterial and cytotoxicity tests. According to the experimental results, increasing the GO amount increased hardness values, compressive value, and antibacterial performance of the MZM composite, while cell viability and osteogenesis level presented reversed trends. It was shown, based on the electrochemical examination, which the corrosion behavior of the MZM alloy was significantly enhanced after encapsulation of 0.5 wt.% GO. Taken together, the antibacterial and mechanically MZM nanocomposites reinforced with GO to be used for implant applications.
Research Article
Effect of cathodic potential on stress corrosion cracking behavior of 21Cr2NiMo steel in simulated seawater
Meng-hao Liu, Zhi-yong Liu, Cui-wei Du, Xiao-qin Zhan, Chun-duo Dai, Yue Pan, and Xiao-gang Li
Available online 25 September 2020, https://doi.org/10.1007/s12613-020-2199-5
[Abstract](1184) [PDF 2930KB](5)
Abstract:
This study aims at providing systematically insights into the impact of cathodic polarization on the stress corrosion cracking (SCC) behavior of 21Cr2NiMo steel. Slow stress tensile test demonstrated that 21Cr2NiMo steel is highly sensitive to hydrogen embrittlement at strong cathodic polarization. The lowest SCC susceptibility is presented at -775 mVSCE whereas the SCC susceptibility increased remarkably below -950 mVSCE. SEM and EBSD revealed that cathodic potential decline causes a transition in fracture path from transgranular mode to intergranular mode. The intergranular mode transforms from bainite boundaries separation to prior austenitic grain boundaries separation when more cathodically polarized. Furthermore, corrosion pits promoted the nucleation of SCC cracks. In conclusion, the SCC mechanism transforms from the coexistence of hydrogen embrittlement mechanism and anodic dissolution mechanism to typical hydrogen embrittlement mechanism with applied potential decreases.
Research Article
Microstructure and tribological behavior of the nickel-coated-graphite reinforced Babbitt metal composite fabricated by selective laser melting
Xing-ke Zhao and Xu-sheng Hai
Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2195-9
[Abstract](1246) [PDF 1740KB](5)
Abstract:
For purpose of improving the properties of Babbitt alloys, Ni-coated-graphite reinforced Babbitt metal composite specimens were prepared by selective laser melting (SLM) process, and their microstructures, mechanical and tribological properties were studied using scanning electron microscope (SEM), shear test and dry-sliding wear test, respectively. The results show that most of NCGr particles distribute at boundaries of laser beads in the cross-section of the SLM composite specimens. Microcracks or microvoids form at boundaries of laser beads where NCGr particle accumulating. Both shearing strength and the friction coefficient of the SLM composite specimens decrease with increasing NCGr content. The shearing strength and the friction coefficient of the SLM composite sample with 6% NCGr decrease by around 20% and 33% compared with the NCGr-free sample. Friction mechanism changes from plastic shaping furrow to brittle cutting with increasing NCGr content. A practical Babbitt material with a lower friction coefficient and proper strength could be expected if the dispersion of the NCGr particles is controlled by choosing NCGr particles with thicker Ni layer and precisely controlling laser energy input during SLM process.
Research Article
Experimental study on flow zone distribution and mixing time in a Peirce-Smith copper converter
Hong-liang Zhao, Jing-qi Wang, Feng-qin Liu, and Hong Yong Sohn
Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2196-8
[Abstract](1251) [PDF 623KB](41)
Abstract:
Peirce-Smith copper converting involved complex multiphase flow and mixing. In this work, the flow zone distribution and the mixing time in a copper PSC were investigated in a 1:5 scaled cold model. Flow field distribution including dead, splashing and strong-loop zones were measured and a dimensionless equation was developed to correlate the effects of stirring and mixing energy with an error less than 5%. Four positions in the bath including injection, splashing, strong-loop and dead zones were selected to add the hollow salt powders tracer and measure the mixing time. The injection of the quartz flux through the tuyeres or into the backflow point of the splashing wave through a chute is recommended, instead of adding it through a crane hopper from the top of the furnace, to improve the slag-making reaction.
Research Article
The stress corrosion cracking behavior of high-strength mooring chain steel in SO2-polluted coastal atmosphere
Meng-hao Liu, Zhi-yong Liu, Cui-wei Du, Xiao-qin Zhan, Xiao-jia Yang, and Xiao-gang Li
Available online 12 September 2020, https://doi.org/10.1007/s12613-020-2192-z
[Abstract](1396) [PDF 2645KB](5)
Abstract:
21Cr2NiMo steel is widely used to stabilize offshore oil platforms, however, it suffers from stress corrosion cracking (SCC). Herein, we studied the SCC behavior of 21Cr2NiMo steel in SO2-polluted coastal atmospheres. Electrochemical tests revealed that the addition of SO2 increases the corrosion current. Rust characterization showed that the SO2 addition densities the corrosion products and promotes pitting. Furthermore, the slow strain rate tests demonstrated high susceptibility to SCC at high SO2 contents. Fracture morphologies revealed that the stress-corrosion cracks initiated at corrosion pits and the crack propagation showed transgranular and intergranular cracking modes. In conclusion, the SCC is mix-controlled by anodic dissolution and hydrogen embrittlement mechanisms.
Research Article
Synthesis, characterization and magnetic properties of KFeO2 nanoparticles prepared by a simple egg-white solution route
Thongsuk Sichumsaeng, Nutthakritta Phromviyo, Supree Pinitsoontorn, Pinit Kidkhunthod, Narong Chanlek, and Santi Maensiri
Available online 12 September 2020, https://doi.org/10.1007/s12613-020-2194-x
[Abstract](1446) [PDF 2541KB](20)
Abstract:
In this work, nanoparticles of potassium ferrite (KFeO2) were synthesized by a simple egg-white solution method upon calcination in air at different temperatures of 500, 600, and 700ºC for 2 h. The effects of calcination temperature on structural and magnetic properties of the synthesized KFeO2 nanoparticles were investigated. By varying the calcination temperature, X-ray diffraction (XRD) and transmission electron microscopy (TEM) results indicated the changes of crystallinity and morphology including particle size, respectively. Significantly, the reduction of particle size of the synthesized KFeO2 was found to have a great influence on the magnetic properties. At room temperature, the synthesized KFeO2 nanoparticles prepared at 600ºC exhibited the highest saturation magnetization (MS) of 26.24 emu•g-1. In addition, the coercivity (HC) increased from 3.51 to 16.89 kA•m-1 with increasing calcination temperature up to 700ºC. The zero-field-cooled (ZFC) results showed that the blocking temperatures (TB) of about 125 and 85 K were observed in the samples calcined at 500 and 600ºC, respectively. Therefore, this work shows that the egg-white solution method is a simple, cost effective, and environmental-friendly for the preparation of KFeO2 nanoparticles.
Research Article
Multi-objective collaborative optimization of metallurgical properties of iron carbon agglomerates using response surface methodology
Ji-wei Bao, Man-sheng Chu, Zheng-gen Liu, Dong Han, Lai-geng Cao, Jun Guo, and Zi-chuan Zhao
Available online 5 September 2020, https://doi.org/10.1007/s12613-020-2188-8
[Abstract](1357) [PDF 1301KB](22)
Abstract:
Iron carbon agglomerates (ICA) is considered to be an innovative charge to realize low carbon blast furnace (BF) ironmaking. In this study, the central composite Design (CCD) based on response surface methodology (RSM) was used to synergistically optimize the compressive strength, reactivity and post-reaction strength of ICA. The results show that the iron ore ratio has the most significant influence on compressive strength, reactivity and post-reaction strength. There are significant interactions on the compressive strength and reactivity between the iron ore ratio and carbonization temperature or the iron ore ratio and carbonization time, while the three variables do not interact with each other on the post-reaction strength. In addition, the optimal process parameters are iron ore ratio of 15.30%, carbonization temperature of 1000℃ and carbonization time of 4.27 h, and the model prediction results of compressive strength, reactivity and post-reaction strength are 4026 N, 55.03% and 38.24% respectively, which are close to the experimental results and further verifies the accuracy and reliability of the models.
Research Article
Effect of graphene addition on physico-mechanical and tribological properties of Cu-nanocomposites
Adnan I. Khdair and A. F. Ibrahim
Available online 5 September 2020, https://doi.org/10.1007/s12613-020-2183-0
[Abstract](1379) [PDF 731KB](33)
Abstract:
This paper presents experimental investigation of the mechanical and tribological properties of Cu-GNs nanocomposites. We employed electroless coating process to coat GNs with Ag particles to avoid their reaction with Cu and formation of intermetallic phases. We studied the effect of GNs content on structural, mechanical and tribological properties of the produced nanocomposites. The results showed that the coating process is an efficient technique to avoid reaction between Cu and C and the formation intermetallic phases. The addition of GNs should be done wisely since the mechanical and tribological properties improved with increasing GNs up to a certain threshold values. The optimum GNs proved is 0.5%, at which hardness, wear rate and coefficient of friction are improved by 13%, 81.9% and 49.8%, respectively, compared to Cu- nanocomposite. These improved properties are due to the reduced crystallite size, presence of GNs and homogenous distribution of constituents.
Research Article
3D graphitic carbon sphere foams as sorbents for cleaning oil spills
Sai-sai Li, Hai-jun Zhang, Long-hao Dong, Hai-peng Liu, Quan-li Jia, and Dong Xu
Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2180-3
[Abstract](1390) [PDF 737KB](13)
Abstract:
Frequent offshore oil spill accidents, industrial oily sewage and the indiscriminate disposal of urban oily sewage have caused serious impacts on human living environment and health. The traditional oil-water separation methods not only cause easily environmental secondary pollution, but also waste of limited resources. Therefore, in this work, 3D graphitic carbon sphere foams (3D-foams) possessed three-dimensional porous structure with pore size distribution of 25~200 μm, and high porosity of 62% were prepared for oil adsorption via foam-gel casting method using graphitic carbon spheres as starting materials. The resulted indicated that the water contact angle of as-prepared 3D-foams was 130°. The contents of graphitic carbon spheres (GCS) greatly influenced the hydrophobicity, water contact angle (WCA) and microstructure of the as-prepared samples. The adsorption capacities of as-prepared 3D-foams for paraffin oil, vegetable oil and vacuum pump oil were about 12~15 g/g, which were 10 times of that graphitic carbon spheres powder.
Research Article
Process-structure-property relationship for plasma sprayed iron based amorphous-crystalline composite coatings
Abhishek Pathak, Biswajyoti Mukherjee, Krishna Kant Pandey, Aminul Islam, Pavan Bijalwan, Monojit Dutta, Atanu Banerjee, and Anup Kumar Keshri
Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2171-4
[Abstract](1654) [PDF 1233KB](55)
Abstract:
The present study explores the fabrication of Fe-based amorphous coating by air plasma spraying and its dependency on the coating parameters (plasma power, primary gas flow rate, stand-off distance and powder feed rate). XRD of the coatings deposited at optimized spray parameters showed the presence of amorphous-crystalline phase. Coatings deposited at lower plasma power and moderate gas flow rate exhibited better density, hardness and wear resistance. All coatings demonstrated equally good resistance against corrosive environment (NaCl). Mechanical, wear and tribological studies indicate that a single process parameter optimization cannot provide good coating performance but instead, all process parameters are having their unique role in defining better properties to the coating by controlling the in-flight particle temperature and velocity profile followed by the cooling pattern of molten droplet before impingement on the substrate.
Research Article
Interface behavior of chalcopyrite during flotation from cyanide tailings
Xue-min Qiu, Hong-ying Yang, Guo-bao Chen, Lin-lin Tong, Zhe-nan Jin, and Qin Zhang
Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2170-5
[Abstract](1434) [PDF 1042KB](17)
Abstract:
Interface characteristics of cyanide tailings are very different compared with those of raw ore. Valuable elements could not be comprehensively recovered via flotation from cyanide tailings originating from Shandong province, China. Herein, the interface and floatability of these tailings were investigated. The chalcopyrite in the cyanide tailings investigated herein was fine with a porous surface. The floatability of 68% chalcopyrite was similar to galena in the presence of a collector. This part of chalcopyrite was compactly wrapped in a layer of fine galena particles. The recovery of chalcopyrite sharply decreased as the nonpolar oil residue in cyanide tailings was removed through alcohol extraction; however, this removal had no effect on galena. The other chalcopyrite in the flotation tailings was covered with an oxidation layer consisting of O, Fe, S, Pb, Cu, Zn, and Si.
Research Article
Carbothermic reduction of vanadium titanomagnetite with the assistance of sodium carbonate
Lu-ming Chen, Yu-lan Zhen, Guo-hua Zhang, De-sheng Chen, Li-na Wang, Hong-xin Zhao, Fan-cheng Meng, and Tao Qi
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2160-7
[Abstract](1466) [PDF 2054KB](34)
Abstract:
In the present study, the carbothermic reduction of vanadium titanomagnetite concentrates (VTC) with the assistance of Na2CO3 was carried out in argon atmosphere between 1073 K and 1473 K. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to investigate the phase transformations during the reaction process. By investigating the reaction between VTC and Na2CO3, it was concluded that molten Na2CO3 could break the structure of titanomagnetite by combining with the acidic oxides (Fe2O3, TiO2, Al2O3, and SiO2) to form the Na-rich melt, and release FeO and MgO. Therefore, Na2CO3 could accelerate the reduction rate. In addition, the addition of Na2CO3 was also beneficial for the agglomeration of iron particles and the slag-metal separation by decreasing the viscosity of slag. Thus, the Na2CO3 assisted carbothermic reduction will be a promising method to treat VTC at low temperatures.
Research Article
New insights into the flotation response of brucite and serpentine of different conditioning time: Surface dissolution behavior
Ya-feng Fu, Wan-zhong Yin, Chuan-yao Sun, Bin Yang, Jin Yao, Hong-liang Li, Chuang Li, and Hyunjung Kim
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2158-1
[Abstract](1754) [PDF 721KB](35)
Abstract:
Gangue minerals inadvertently dissolution frequently plays a detrimental role on the flotation of valuable minerals. In this paper, the effect of conditioning time on the flotation separation of brucite and serpentine was investigated. By analyzing the Mg2+ concentration, the relative content of elements, and pulp viscosity, the effect of mineral dissolution on the brucite flotation was studied. The artificial mixed mineral flotation results (with -10 μm serpentine) showed that, with the conditioning time extended from 60 s to 360 s, a large amount of Mg2+ on the mineral surface gradually dissolved into the pulp, resulting in a decrease of brucite recovery (from 83.83% to 76.79%), whereas the recovery of serpentine increased from 52.12% to 64.03%. Moreover, the SEM observation was applied to analyze the agglomeration behavior of brucite and serpentine, which clearly demonstrated the difference of adhesion behavior under various conditioning time. Finally, the total interaction energy that carried out by extended DLVO (E-DLVO) theory also supports the conclusion that the gravitational force between brucite and serpentine increases significantly with the increase of conditioning time.
Research Article
Process and kinetics of the selective extraction of cobalt from high-silicon low-grade cobalt ore by ammonia leaching
Lei Tian, Ao Gong, Xuan-gao Wu, Xiao-qiang Yu, Zhi-feng Xu, and Li-jie Chen
Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2161-6
[Abstract](1417) [PDF 1527KB](5)
Abstract:
In this study, an ammonia-based system was used to selectively leach Co from an African high-silicon low-grade Co ore. In this process, other elemental impurities were prevented from leaching; hence, the subsequent process was simple and environmentally friendly. The results revealed that the leaching ratio of Co can reach 95.61% using (NH4)2SO4 as a leaching agent under experimental conditions, which involved a (NH4)2SO4 concentration, reductant dosage, leaching temperature, reaction time, and liquid–solid ratio of 300 g/L, 0.7 g, 353 K, 4 h, and 6:1, respectively. The leaching kinetics of Co showed that the apparent activation energy of Co leaching was 72.97 kJ/mol (i.e., in the range of 40–300 kJ/mol). This indicated that the leaching of Co from the Co ore was controlled using an interfacial chemical reaction. The reaction orders of the particle size and (NH4)2SO4 concentration during leaching were 0.21 and 1.5, respectively. The leaching kinetics model of the Co developed in this study can be expressed as 1-(1-α)1/3 = 28.01 × 103×r0-1 × [(NH4)2SO4]1.5 × exp(-72970/8.314T).
Research Article
Effect of ‎2-Mercaptobenzothiazole concentration on the sour corrosion behavior of API X60 pipeline steel: Electrochemical parameters and adsorption mechanism
Masoud Sabzi, Amir Hayati Jozani, Farzad Zeidvandi, Majid Sadeghi, and Saeid Mersagh Dezfuli
Available online 30 July 2020, https://doi.org/10.1007/s12613-020-2156-3
[Abstract](1469) [PDF 1304KB](12)
Abstract:
The effect of 2-Mercaptobenzothiazole concentration on the sour corrosion behavior of API X60 pipeline steel in an environment containing H2S at 25 °C and at the presence of 0, 2.5, 5, 7.5 and 10 g/L of 2-Mercaptobenzothiazole inhibitor was investigated. In order to examine the sour corrosion behavior of API X60 pipeline steel, Open Circuit Potential (OCP), potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) tests were used. The Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) were also used to analyze corrosion products. The results of OCP and potentiodynamic polarization both showed that 2-Mercaptobenzothiazole reduces the speed of both anodic and cathodic reactions. Assessment of  the Gibbs free energy of the inhibitor showed that it has a value of more than –20 kJ.mol−1and less than –40 kJ.mol−1. Therefore, the adsorption of 2-Mercaptobenzothiazole on the surface of the API X60 pipeline steel was occurred both physically and chemically. The latter was particularly intended to be adsorbed. Also, as the Gibbs free energy of the inhibitor took a negative value, it was concluded that the adsorption of 2-Mercaptobenzothiazole on the surface of the pipeline steel occurs spontaneously. The results of the EIS indicated that with increase of 2-Mercaptobenzothiazole inhibitor concentration, the corrosion resistance of API X60 steel is increased.An analysis of the corrosion products revealed that iron sulfide compounds are formed on the surface. In sum, the results showed that the increase of the inhibitor concentration results in a decrease in the corrosion rate and an increase ininhibitory efficiency (%IE). Additionally, it was found that 2-Mercaptobenzothiazole adsorption process on the API X 60 steel surfaces in a H2S-containing environment follows the Langmuir adsorption isotherm.And the adsorption process is carried out spontaneously. 
Research Article
Insights into U(VI) adsorption behavior onto polypyrrole coated 3R-MoS2 nanosheets prepared with the molten salt electrolysis method
Yu-hui Liu, Meng Tang, Shuang Zhang, Yu-ling Lin, Ying-cai Wang, You-qun Wang, Ying Dai, Xiao-hong Cao, Zhi-bin Zhang, and Yun-hai Liu
Available online 30 July 2020, https://doi.org/10.1007/s12613-020-2154-5
[Abstract](1751) [PDF 1326KB](55)
Abstract:
To improve the separation capacity of uranium in aqueous solutions, 3R-MoS2 nanosheets were prepared with molten salt electrolysis and further modified with polypyrrole (PPy) to synthesize a hybrid nanoadsorbent (PPy/3R-MoS2). The preparation conditions of PPy/3R-MoS2 were investigated and the obtained nanosheets were characterized with SEM, HRTEM, XRD, FTIR, and XPS. The results show that PPy/3R-MoS2 exhibited enhanced adsorption capacity towards U(VI) compared to pure 3R-MoS2 and PPy; the maximum adsorption was 200.4 mg/g. The adsorption mechanism was elucidated with XPS and FTIR: 1) negatively charged PPy/3R-MoS2 nanosheets attracted UO22+ by electrostatic attraction; 2) exposed C, N, Mo, and S atoms complexed with U(VI) through coordination; 3) Mo in the complex partly reduced the adsorbed U(VI) to U(IV), which further regenerated the adsorption point and continuously adsorbed U(VI). The design of the PPy/3R-MoS2 composite with high adsorption capacity and chemical stability provides a new direction for the removal of radionuclide.
Research Article
Effect of calcination temperature on the pozzolanic activity of maize straw stem ash treated with portlandite solution
Ting-ye Qi, Hao-chen Wang, Guo-rui Feng, Yu-jiang Zhang, Jin-wen Bai, and Yan-na Han
Available online 24 July 2020, https://doi.org/10.1007/s12613-020-2148-3
[Abstract](1511) [PDF 1117KB](20)
Abstract:
The effect of calcination temperature on the pozzolanic activity of maize straw stem ash (MSSA) was evaluated. The MSSA samples calcined at temperature values of 500, 700, and 850 °C were dissolved in portlandite solution for 6 h, and the residual samples were obtained. The MSSA and MSSA residual samples were analyzed using FT-IR, XRD, SEM, and XPS to determine the vibration bonds, minerals, microstructure, and Si 2p transformation behavior. The conductivity, pH value, loss of conductivity with dissolving time of the MSSA-portlandite mixed solution were determined. The main oxide composition of MSSA were silica and potassium oxide. The dissolution of Si4+ content of MSSA at 500 °C were high compared to those of the other calcination temperatures. The conductivity and loss of conductivity of MSSA at 700 °C were high compared to those of the other calcination temperatures at a particular dissolving time due to the higher KCl content in MSSA at 700 °C. C-S-H was easily identified in MSSA samples using XRD, and small cubic and nearly spherical particles of C-S-H were found in the MSSA residual samples. In conclusion, the optimum calcination temperature of MSSA having the best pozzolanic activity is 500 °C but avoid excessive agglomeration.
Research Article
A new electrochemical process on the recovery metallic Mn from waste LiMn2O4 based Li-ion batteries in NaCl-CaCl2 melts
Jing-long Liang, Dong-bin Wang, Le Wang, Hui Li, Wei-gang Cao, and Hong-yan Yan
Available online 16 July 2020, https://doi.org/10.1007/s12613-020-2144-7
[Abstract](1597) [PDF 798KB](25)
Abstract:
A new method for the recovery of Mn is proposed via direct electrochemical reduction of LiMn2O4 from the waste lithium-ion batteries in NaCl-CaCl2 melts at 750℃. The results show the reduction process of LiMn2O4 by electrochemical methods on the coated electrode surface are in three steps, Mn(IV) → Mn(III) → Mn(II) → Mn. The products of electro-deoxidation are CaMn2O4, MnO, (MnO)x(CaO)1-x and Mn. Metal Mn appears when the electrolytic voltage increased to 2.6 V. Increasing the voltage could promote the deoxidation reaction process. With the advancement of the three-phase interline(3PI), the electric deoxygenation gradually proceeds from the outward to core. With the high voltage, the kinetic process of the reduction reaction is accelerated, and double 3PI in different stages are generated.
Research Article
Microstructure and phase elemental distribution in high-boron multi-component cast irons
Yuliia G. Chabak, K. Shimizu, Vasily G. Efremenko, Michail A. Golinskyi, Kenta Kusumoto, Vadim I. Zurnadzhy, and Alexey V. Efremenko
Available online 9 July 2020, https://doi.org/10.1007/s12613-020-2135-8
[Abstract](2457) [PDF 3538KB](11)
Abstract:
The novel cast irons of nominal chemical composition (wt.%) 0.7C-5W-5Mo-5V-10Cr-2.5Ti were fabricated with the additions of 1.6 wt.% B and 2.7 wt.% B. The aim of this work was a study of the boron’s effect on the alloys’ structural state and phase elemental distribution with respect to the formation of wear-resistant structure constituents. It was found that the alloy containing 1.6 % B was composed of three different eutectics: (a) “M2(C,B)5+ferrite” having a “Chinese Script” morphology (89.8 vol. %), (b) “M7(C,B)3+Austenite” having a “Rosette” morphology, and (c) “M3C+Austenite” having a “Ledeburite”-shaped morphology (2.7 vol. %). With a boron content of 2.7 wt.%, the bulk hardness increased from 31 HRC to 38.5 HRC. The primary carboborides M2(C,B)5 with average microhardness of 2797 HV appeared in the structure with a volume fraction of 17.6 vol.%. The volume fraction of eutectics (a) and (b, c) decreased to 71.2 vol.% and 3.9 vol. %, respectively. The matrix was “ferrite/austenite” for 1.6 wt.% B and “ferrite/pearlite” for 2.7 wt.% B. Both cast irons contained compact precipitates of carbide (Ti,M)C and carboboride (Ti,M)(C,В) with a volume fraction of 7.3-7.5 vol. %. The elemental phase distributions, discussed based on EDX-analysis and the appropriate phase formulae, are presented.
Research Article
Extraction of copper from copper bearing biotite by ultrasonic-assisted leaching
Bao-qiang Yu, Jue Kou, Chun-bao Sun, and Yi Xing
Available online 5 July 2020, https://doi.org/10.1007/s12613-020-2132-y
[Abstract](1551) [PDF 467KB](16)
Abstract:
Copper bearing biotite is a typical refractory copper mineral on the surface of Zambian copper belt. Aiming to treat this kind of copper oxide ore with a more effective method, ultrasonic-assisted acid leaching was conducted in this paper. Compared with regular acid leaching, ultrasound could reduce leaching time from 120 min to 40 min, and sulfuric acid concentration could be reduced from 0.5 mol•L-1 to 0.3 mol•L-1. Besides, leaching temperature could be reduced from 75℃ to 45℃ at same copper leaching rate of 78%. Mechanism analysis indicates that ultrasonic wave can cause delamination of copper bearing biotite and increase the specific surface area from 0.55 m2•g-1 to 1.67 m2•g-1. The results indicate that copper extraction from copper bearing biotite by ultrasonic-assisted acid leaching is more effective than regular acid leaching. This study proposes a promising method for recycling valuable metals from phyllosilicate minerals.
Research Article
Synthesis and characterization of ceria nanoparticles by complex-precipitation route
Yan-ping Li, Xue Bian, Yang Liu, Wen-yuan Wu, and Gao-feng Fu
Available online 24 June 2020, https://doi.org/10.1007/s12613-020-2126-9
[Abstract](1558) [PDF 1331KB](6)
Abstract:
Ceria (CeO2) nanoparticles have been successfully synthesized via a simple complex-precipitation route, which employs cerium chloride as cerium source and citric acid as precipitant. The elemental analysis results of carbon, hydrogen, oxygen and cerium in the precursors were calculated, and the results revealed that the precursors were composed of Ce (OH)3, [Ce(H2Cit)3] or [CeCit]. X-ray diffraction (XRD) analysis showed all ceria nanoparticles prepared to be face centered cubic structure. As n value was 0.25 and pH value was 5.5, the specific surface area of the sample reached the maximum value of 83.17 m2/g. Ceria nanoparticles were observed by scanning electron microscope (SEM). Selected electron diffraction patterns of some samples were obtained by transmission electron microscope (TEM), and the crystal plane spacing of each low-exponential crystal plane was calculated. The UV-vis transmittance curve shows that it has the ability to absorb ultraviolet light and pass through visible light. Among all samples, the minimum of the average transmittance of UVA (TUVA) is 4.42%, and the minimum of the average transmittance of UVB (TUVB) is 1.56%.
Research Article
Effects of forced aeration on community dynamics of free and attached bacteria in copper sulphide ore bioleaching
Sheng-hua Yin, Wei Chen, and I.M.S.K. Ilankoon
Available online 24 June 2020, https://doi.org/10.1007/s12613-020-2125-x
[Abstract](1554) [PDF 1535KB](18)
Abstract:
In order to obtain better bioleaching efficiency, bacterial community dynamics and copper leaching with applying forced aeration were investigated during low-grade copper sulphide bioleaching. Results illustrated appropriate aeration yielded improved bacteria concentrations and enhanced leaching efficiencies. The highest bacteria concentration and Cu2+ concentration after 14-day leaching were 7.61×107 cells•mL-1 and 704.9 mg•L-1, respectively, when aeration duration was 4 h•d-1. The attached bacteria played a significant role during bioleaching from day 1 to day 7. However, free bacteria dominated the bioleaching processes from day 8 to day 14. This is mainly caused by the formation of passivation layer through Fe3+ hydrolysis along with bioleaching, which inhibited the contact between attached bacteria and ore. Meanwhile, 16S rDNA analysis verified the effect of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidanson on bioleaching process. The results demonstrate the importance of free and attached bacteria in bioleaching.
Research Article
Hydrothermal synthesis of Zn-Mg based layered double hydroxide coating over copper for its corrosion prevention in both chloride and hydroxide media
Nikhil, Gopal Ji, and Rajiv Prakash
Available online 21 June 2020, https://doi.org/10.1007/s12613-020-2122-0
[Abstract](1706) [PDF 1066KB](18)
Abstract:
Layered double hydroxides (LDHs) can be very interesting materials in corrosion inhibition applications as LDHs stops the corrosive elements by its ability of double layer formation and locking them between its layers. In this work, Zn-Mg based LDHs are grown over copper substrate by hydrothermal method. Two types of Zn-Mg based LDHs have been prepared based on hydrothermal reaction time. Both LDHs have been characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, high resolution scanning electron microscopy, energy dispersive X-ray analysis, atomic force microscopy and X-ray diffraction patterns. The results show that LDHs are successfully grown on copper; however, they are found different in terms of thickness and structural configuration. Corrosion testing of LDHs has been executed both in 0.1 M NaCl and 0.1 M NaOH by ac impedance measurements and Tafel polarization curves. The results show that L48 gives more than 90% protection to copper, which is higher than protection provided by L24. However, it is evident that both LDH (L24 and L48) is more effective in NaCl, in terms of reduction of corrosion. This information indicates that LDH is more efficient to exchange Cl- ions than OH- ions.
Research Article
Effect of microwave pretreatment on grinding and flotation kinetics of copper complex ore
Hamed Gholami, Bahram Rezai, Ahmad Hassanzadeh, Akbar Mehdilo, and Mohammadreza Yarahmadi
Available online 24 May 2020, https://doi.org/10.1007/s12613-020-2106-0
[Abstract](2143) [PDF 692KB](48)
Abstract:
The present work initially studies the kinetics of microwave-assisted grinding and flotation in a porphyry copper deposit. The kinetics tests were carried out on the untreated and microwave irradiated samples by varying the exposure time from 15-150 sec. Optical microscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy were used for determining the mineral liberation, particle surface properties and mineralogical analyses. Results disclosed that the ore’s breakage rate constant monotonically increased by increasing the exposure time particularly for the coarsest fraction size (400 µm) owing to the creation of thermal stress fractures alongside grain boundaries. Exceeded irradiation time (>60 sec) led to the creation of oxidized and porous surfaces along with a dramatic change of particle morphologies resulting in a substantial reduction of both chalcopyrite and pyrite’s flotation rate constants and ultimate recoveries. We concluded that MW-pretreated copper ore was ground faster than untreated one but their floatabilities were somewhat similar.
Research Article
Effect of multi-pass friction stir processing and Mg addition on microstructure and tensile properties of Al-1050 alloy
Shahin Arshadi Rastabi and Masoud Mosallaee
Available online 24 April 2020, https://doi.org/10.1007/s12613-020-2074-4
[Abstract](1753) [PDF 3910KB](41)
Abstract:
The effect of multiple passes of friction stir processing (FSP) and the addition of Mg powder on different parts of the microstrcuture processed including the stir zone (SZ), the heat-affected zone (HAZ), and the thermo-mechanically affected zone (TMAZ) were investigated. The results of the microstructural observations revealed that although the grain size of the SZ decreased in both the non-composite and composite samples, the grain size increased in the TMAZ and the HAZ of the non-composit sample with increasing the numer of FSP passes. Besides, the addition of Mg powder resulted in much more significant grain refinement. Moreover, increasing the number of the FSP passes resulted in a more uniform distribution of Al-Mg intermetallic compounds in the in-situ composite sample. The results of the tensile testing showed that the four- passes FSPed non-composite sample exhibited a higher elongation percentage with a ductile fracture compared with those of the base metal and the four-pass composite sample while lattermost sample exhibited a brittle fracture and a higher tensile strength value than the base metal and the four-pass FSPed non-composite sample. The fabrication of composite samples resulted in noticeable enhancement of hardness compared with the base metal and the non-composite FSPed samples.
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Research Article
Effects of BN content on the mechanical properties of nanocrystalline 3Y-TZP/Al2O3/BN dental ceramics
Lei Zhou, Yan-fang Zhang, Pan Yi, Ying Wen, Chao-fang Dong, Li-min Meng, and Se-fei Yang
  Available online 30 June 2021, https://doi.org/10.1007/s12613-021-2324-0
[FullText HTML](110) [PDF 760KB](7) SpringerLink
Abstract:
3Y-TZP/3wt% Al2O3 powder was coated with varying amounts of BN using the urea and borate reaction sintering method, and then multiphase ceramics were prepared by hot pressing sintering. The micro-topography and the compositional analysis of synthesized ceramics were conducted through scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A mechanical tester was used to analyze the Vickers hardness, fracture toughness, and bending strength of the synthesized ceramics. The results showed that the ceramic with a BN content of 12wt% showed the best processability, but had diminished mechanical properties (such as fracture toughness and bending strength). The ceramic with a BN content of 9wt% showed better processability than those with 3wt% and 6wt% BN. However, the fracture toughness was affected by the addition of 9wt% BN, making this ceramic only usable as a base material for a three-unit fixed bridge. In contrast, the ceramics with a BN content of 3wt% or 6wt% fulfilled the criteria for use in multi-unit restoration, but their low processability made them unsuitable for milling after sintering.
Research Article
Evolution behavior of γ″ phase of IN718 superalloy in temperature/stress coupled field
Han-zhong Deng, Lei Wang, Yang Liu, Xiu Song, Fan-qiang Meng, and Shuo Huang
  Available online 18 June 2021, https://doi.org/10.1007/s12613-021-2317-z
[FullText HTML](131) [PDF 1562KB](16) SpringerLink
Abstract:
The evolution behavior of the γ″ phase of IN718 superalloy in a temperature/stress coupled field was investigated. Results showed that the coarsening rate of the γ′′ phase was significantly accelerated in the temperature/stress coupled field. Based on the detail microstructural and crystal defect analysis, it was found that the coarsening rate of the γ′′ phase with applied stress was significantly higher than that without stress. The main reasons for the increase in the coarsening rate of the γ′′ phase are as follows: the vacancy formation energy is decreased by the applied stress, which leads to an increase in the vacancy concentration; in the temperature/stress coupled field, the Nb atoms easily combine with vacancies to form complexes and diffuse with the complexes, resulting in a significant increase in the Nb atom diffusion coefficient; Nb atom diffusion is the key control factor for the coarsening of the γ′′ phase.
Research Article
Chemical vapor deposition growth behavior of graphene
Jie Wang, Tengfei Fan, Jianchen Lu, Xiaoming Cai, Lei Gao, and Jinming Cai
  Available online 9 May 2021, https://doi.org/10.1007/s12613-021-2302-6
[FullText HTML](151) [PDF 861KB](12) SpringerLink
Abstract:
The optimized growth parameters of graphene with different morphologies, such as dendrites, rectangle, and hexagon, have been obtained by low-pressure chemical vapor deposition on polycrystalline copper substrates. The evolution of fractal graphene, which grew on the polycrystalline copper substrate, has also been observed. When the equilibrium growth state of graphene is disrupted, its intrinsic hexagonal symmetry structure will change into a non-hexagonal symmetry structure. Then, we present a systematic and comprehensive study of the evolution of graphene with different morphologies grown on solid copper as a function of the volume ratio of methane to hydrogen in a controllable manner. Moreover, the phenomena of stitching snow-like graphene together and stacking graphene with different angles was also observed.
Research Article
Synthesis, characterization and radioluminescence properties of erbium-doped yttria phosphors
Fatma Unal, Faruk Kaya, and Kursat Kazmanli
  Available online 22 February 2021, https://doi.org/10.1007/s12613-021-2269-3
[FullText HTML](373) [PDF 1418KB](27) SpringerLink
Abstract:
Radioluminescence (RL) behaviour of erbium-doped yttria nanoparticles (Y2O3:Er3+ NPs) which were produced by sol–gel method was reported for future scintillator applications. NPs with dopant rates of 1at%, 5at%, 10at% and 20at% Er were produced and calcined at 800°C, and effect of increased calcination temperature (1100°C) on the RL behaviour was also reported. X-ray diffraction (XRD) results showed that all phosphors had the cubic Y2O3 bixbyite-type structure. The lattice parameters, crystallite sizes (CS), and lattice strain values were calculated by Cohen-Wagner (C-W) and Williamson-Hall (W-H) methods, respectively. Additionally, the optimum solubility value of the Er3+ dopant ion in the Y2O3 host lattice was calculated to be approximately 4at% according to Vegard’s law, which was experimentally obtained from the 5at% Er3+ ion containing solution. Both peak shifts in XRD patterns and X-ray photoelectron spectroscopy (XPS) analyses confirmed that Er3+ dopant ions were successfully incorporated into the Y2O3 host structure. High-resolution transmission electron microscopy (HRTEM) results verified the average CS values and agglomerated NPs morphologies were revealed. Scanning electron microscopy (SEM) results showed the neck formation between the particles due to increased calcination temperature. As a result of the RL measurements under a Cu Kα X-ray radiation (wavelength, λ = 0.154 nm) source with 50 kV and 10 mA beam current, it was determined that the highest RL emission belonged to 5at% Er doped sample. In the RL emission spectrum, the emission peaks were observed in the wavelength ranges of 510–575 nm (2H11/2, 4S3/24I15/2; green emission) and 645–690 nm (4F9/24I15/2; red emission). The emission peaks at 581, 583, 587, 593, 601, 611 and 632 nm wavelengths were also detected. It was found that both dopant rate and calcination temperature affected the RL emission intensity. The color shifted from red to green with increasing calcination temperature which was attributed to the increased crystallinity and reduced crystal defects.
Research Article
Graphene oxide wrapped magnetic nanoparticle composites induced by SiO2 coating with excellent regenerability
Zhong-liang Hu, Hou-quan Cui, Yan-huai Ding, Jing-ying Li, Yi-rong Zhu, and Zhao-hui Li
  Available online 26 November 2020, https://doi.org/10.1007/s12613-020-2229-3
[FullText HTML](502) [PDF 897KB](7) SpringerLink
Abstract:
Graphene oxide (GO) wrapped Fe3O4 nanoparticles (NPs) were prepared by coating the Fe3O4 NPs with a SiO2 layer, and then modifying by amino groups, which interact with the GO nanosheets to form covalent bonding. The SiO2 coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets. The effect of the amount of SiO2 on the morphology, structure, adsorption, and regenerability of the composites was studied in detail. An appropriate SiO2 layer can effectively induce the GO nanosheets to completely wrap the Fe3O4 NPs, forming a core-shell Fe3O4@SiO2@GO composite where Fe3O4@SiO2 NPs are firmly encapsulated by GO nanosheets. The optimized Fe3O4@SiO2@GO sample exhibits a high saturated adsorption capacity of 253 mg·g−1 Pb(II) cations from wastewater, and the adsorption process is well fitted by Langmuir adsorption model. Notably, the composite displays excellent regeneration, maintaining a ~90% adsorption capacity for five cycles, while other samples decrease their adsorption capacity rapidly. This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.
Research Article
Reduction of residual stress in porous Ti6Al4V by in situ double scanning during laser additive manufacturing
Yi-wa Luo, Ming-yong Wang, Ji-guo Tu, Yu Jiang, and Shu-qiang Jiao
  Available online 20 October 2020, https://doi.org/10.1007/s12613-020-2212-z
[FullText HTML](737) [PDF 1176KB](32) SpringerLink
Abstract:
Selective laser melting (SLM) technology plays an important role in the preparation of porous titanium (Ti) implants with complex structures and precise sizes. Unfortunately, the processing characteristics of this technology, which include rapid melting and solidification, lead to products with high residual stress. Herein, an in situ method was developed to restrain the residual stress and improve the mechanical strength of porous Ti alloys during laser additive manufacturing. In brief, porous Ti6Al4V was prepared by an SLM three-dimensional (3D) printer equipped with a double laser system that could rescan each layer immediately after solidification of the molten powder, thus reducing the temperature gradient and avoiding rapid melting and cooling. Results indicated that double scanning can provide stronger bonding conditions for the honeycomb structure and improve the yield strength and elastic modulus of the alloy. Rescanning with an energy density of 75% resulted in 33.5%–38.0% reductions in residual stress. The porosities of double-scanned specimens were 2%–4% lower than those of single-scanned specimens, and the differences noted increased with increasing sheet thickness. The rescanning laser power should be reduced during the preparation of porous Ti with thick cell walls to ensure dimensional accuracy.
Research Article
Microstructure and mechanical properties of reaction-bonded B4C–SiC composites
Rong-zhen Liu, Wen-wei Gu, Yu Yang, Yuan Lu, Hong-bin Tan, and Jian-feng Yang
  Available online 7 October 2020, https://doi.org/10.1007/s12613-020-2207-9
[FullText HTML](794) [PDF 3873KB](14) SpringerLink
Abstract:
Reaction-bonded B4C–SiC composites are highly promising materials for numerous advanced technological applications. However, their microstructure evolution mechanism remains unclear. Herein, B4C–SiC composites were fabricated through the Si-melt infiltration process. The influences of the sintering time and the B4C content on the mechanical properties, microstructure, and phase evolution were investigated. X-ray diffraction results showed the presence of SiC, boron silicon, boron silicon carbide, and boron carbide. Scanning electron microscopy results showed that with the increase in the boron carbide content, the Si content decreased and the unreacted B4C amount increased when the sintering temperature reached 1650°C and the sintering time reached 1 h. The unreacted B4C diminished with increasing sintering time and temperature when B4C content was lower than 35wt%. Further microstructure analysis showed a transition area between B4C and Si, with the C content marginally higher than in the Si area. This indicates that after the silicon infiltration, the diffusion mechanism was the primary sintering mechanism of the composites. As the diffusion process progressed, the hardness increased. The maximum values of the Vickers hardness, flexural strength, and fracture toughness of the reaction-bonded B4C–SiC ceramic composite with 12wt% B4C content sintered at 1600°C for 0.5 h were about HV 2400, 330 MPa, and 5.2 MPa·m0.5, respectively.
Research Article
Oxidation behavior of high Hf nickel-based superalloy in air at 900, 1000 and 1100°C
Jiu-han Xiao, Ying Xiong, Li Wang, Xiang-wei Jiang, Dong Wang, Kai-wen Li, Jia-sheng Dong, and Lang-hong Lou
  Available online 1 October 2020, https://doi.org/10.1007/s12613-020-2204-z
[FullText HTML](1367) [PDF 3483KB](21) SpringerLink
Abstract:
To investigate the oxidation behavior of a nickel-based superalloy with high hafnium content (1.34wt%), this study performed isothermal oxidation tests at 900, 1000, and 1100°C for up to 200 h. X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy were applied to study the oxidation behavior. The weight gain of the high Hf nickel-based superalloy exhibited a parabola-like curve, and no spallation of the oxide scale was observed during the oxidation tests. The alloy presented excellent oxidation resistance, and no HfO2 was observed in the oxide scale at 900°C. With the increase of the oxidation temperature to 1000°C, HfO2 particles formed in the spinel phases of the scale, and “peg-like” HfO2 was observed within and beneath the inner layer of Al2O3 after 200 h. As the oxidation temperature rose to 1100°C, “peg-like” HfO2 was observed at the early stage of the oxidation test (within 25 h). The formation mechanism of HfO2 and its impact on oxidation resistance were investigated based on the analysis of the oxidation test results at different temperatures.
Research Article
Effects of Si/Al, Na/Al, and H2O/Na2O molar ratios on formaldehyde barrier properties of inorganic aluminosilicate coatings
Shan-xia Xiong, Jian-lei Kuang, Qian-fang Zheng, Ting Xiao, Wen-xiu Liu, Qi Wang, Peng Jiang, and Wen-bin Cao
  Available online 19 September 2020, https://doi.org/10.1007/s12613-020-2197-7
[FullText HTML](1284) [PDF 7292KB](11) SpringerLink
Abstract:
Wood-based panels containing urea-formaldehyde resin result in the long-term release of formaldehyde and threaten human health. In this study, inorganic aluminosilicate coatings prepared by combining metakaolin, silica fume, NaOH, and H2O were applied to the surfaces of wood-based panels to obstruct formaldehyde release. The Si/Al, Na/Al, and H2O/Na2O molar ratios of the coatings were regulated to investigate their effects on the structure and formaldehyde-resistant barrier properties of coatings. Results showed that the cracks in the coatings gradually disappeared and the formaldehyde resistance rates of the barrier increased as the Si/Al molar ratio was increased from 1.6 to 2.2. This value also increased as the Na/Al molar ratio was increased from 0.9 to 1.2 because of the improvement of the degree of polymerization. As the H2O/Na2O molar ratio was increased from 12 to 15, the thickness of the dry film decreased gradually and led to the reduction in the formaldehyde resistance rate. When the Si/Al, Na/Al, and H2O/Na2O molar ratios were 2.2, 1.2, and 12, respectively, the inorganic aluminosilicate coating showed good performance as a formaldehyde-resistant barrier and its formaldehyde resistance rate could reach up to 83.2%.
Research Article
Fabrication of green one-part geopolymer from silica-rich vanadium tailing via thermal activation and modification
Shenxu Bao, Yongpeng Luo, and Yimin Zhang
  Available online 3 September 2020, https://doi.org/10.1007/s12613-020-2182-1
[FullText HTML](1561) [PDF 1473KB](31) SpringerLink
Abstract:
The aim of this investigation was to prepare geopolymeric precursor from vanadium tailing (VT) by thermal activation and modification. For activation, a homogeneous blend of VT and sodium hydroxide was calcinated at an elevated temperature and then modified with metakaolin to produce a geopolymeric precursor. During the thermal activation, the VT was corroded by sodium hydroxide and then sodium silicate formed on the particle surfaces. After water was added, the sodium silicate coating dissolved to release silicon species, which created an alkaline solution environment. The metakaolin then dissolved in the alkaline environment to generate aluminum species, which was followed by geopolymerization. The VT particles were connected by a gel produced during geopolymerization, which yielded a geopolymer with excellent mechanical performance. This investigation not only improves the feasibility of using geopolymer technology for large-scale and in-situ applications, but also promotes the utilization of VT and other silica-rich solid wastes.
Research Article
Separation of tungsten and molybdenum with solvent extraction using functionalized ionic liquid tricaprylmethylammonium bis(2,4,4-trimethylpentyl)phosphinate
Fei Cao, Wei Wang, De-zhou Wei, and Wen-gang Liu
  Available online 27 August 2020, https://doi.org/10.1007/s12613-020-2172-3
[FullText HTML](1473) [PDF 1027KB](15) SpringerLink
Abstract:
Functionalized ionic liquids (FILs) as extractants were employed for the separation of tungsten and molybdenum from a sulfate solution for the first time. The effects of initial pH, extractant concentration, metal concentrations in the feed were comprehensively investigated. The results showed that tricaprylmethylammonium bis(2,4,4-trimethylpentyl)phosphinate ([A336][Cyanex272]) could selectively extract W over Mo at an initial pH value of 5.5; the best separation factor βW/Mo of 25.61 was obtained for a solution with low metal concentrations (WO3: 2.49 g/L, Mo: 1.04 g/L). The [A336][Cyanex272] system performed effectively for solutions of different W/Mo molar ratios and different metal ion concentrations in the feed. The chemical reaction between [A336][Cyanex272] and W followed the ion association mechanism, which was further proved by the Fourier-transform infrared (FTIR) spectra of loaded [A336][Cyanex272] and the free extractant. The stripping experiments indicated that 95.48% W and 100.00% Mo were stripped using a 0.20 mol/L sodium hydroxide solution. Finally, the selective extractions of W and Mo from two synthetic solutions of different high metal concentrations were obtained; the separation factor βW/Mo reached 23.24 and 17.59 for the first and second solutions, respectively. The results suggest the feasibility of [A336][Cyanex272] as an extractant for the separation of tungsten and molybdenum.
Research Article
Strain hardening behavior, strain rate sensitivity and hot deformation maps of AISI 321 austenitic stainless steel
Mehdi Shaban Ghazani and Beitallah Eghbali
  Available online 10 August 2020, https://doi.org/10.1007/s12613-020-2163-4
[FullText HTML](1555) [PDF 3503KB](33) SpringerLink
Abstract:
Hot compression tests were performed on AISI 321 austenitic stainless steel in the deformation temperature range of 800–1200°C and constant strain rates of 0.001, 0.01, 0.1, and 1 s−1. Hot flow curves were used to determine the strain hardening exponent and the strain rate sensitivity exponent, and to construct the processing maps. Variations of the strain hardening exponent with strain were used to predict the microstructural evolutions during the hot deformation. Four variations were distinguished reflecting the different microstructural changes. Based on the analysis of the strain hardening exponent versus strain curves, the microstructural evolutions were dynamic recovery, single and multiple peak dynamic recrystallization, and interactions between dynamic recrystallization and precipitation. The strain rate sensitivity variations at an applied strain of 0.8 and strain rate of 0.1 s−1 were compared with the microstructural evolutions. The results demonstrate the existence of a reliable correlation between the strain rate sensitivity values and evolved microstructures. Additionally, the power dissipation map at the applied strain of 0.8 was compared with the resultant microstructures at predetermined deformation conditions. The microstructural evolutions strongly correlated to the power dissipation ratio, and dynamic recrystallization occurred completely at lower power dissipation ratios.
Research Article
Gold-leaching performance and mechanism of sodium dicyanamide
Gen-zhuang Li, Jue Kou, Yi Xing, Yang Hu, Wei Han, Zi-yuan Liu, and Chun-bao Sun
  Available online 26 July 2020, https://doi.org/10.1007/s12613-020-2153-6
[FullText HTML](1672) [PDF 3473KB](25) SpringerLink
Abstract:
In this work, sodium dicyanamide (SD) was used as a leaching reagent for gold recovery, and the effects of the SD dosage and solution pH on the gold-leaching performance were investigated. A gold recovery of 34.8% was obtained when SD was used as the sole leaching reagent at a dosage of 15 kg/t. In the presence of a certain amount of potassium ferrocyanide (PF) in the SD solution, the gold recovery was found to increase from 34.8% to 57.08%. Using the quartz crystal microbalance with dissipation (QCM-D) technique, the leaching kinetics of SD with and without PF were studied. The QCM-D results indicate that the gold-leaching rate increased from 4.03 to 39.99 ng·cm–2·min–1 when the SD concentration was increased from 0 to 0.17 mol/L, and increased from 39.99 to 272.62 ng·cm–2·min–1 when 0.1 mol/L of PF was used in combination with SD. The pregnant solution in the leaching tests was characterized by X-ray photoelectron spectroscopy and electrospray mass spectrometry, which indicated that Au and (N(CN)2) in the SD solution formed a series of metal complex ions, [AuNax(N(CN)2)x+2] (x = 1, 2, 3, or 4).
Research Article
Fine structure characterization of an explosively-welded GH3535/316H bimetallic plate interface
Jia Xiao, Ming Li, Jian-ping Liang, Li Jiang, De-jun Wang, Xiang-xi Ye, Ze-zhong Chen, Na-xiu Wang, and Zhi-jun Li
  Available online 26 June 2020, https://doi.org/10.1007/s12613-020-2128-7
[FullText HTML](1264) [PDF 10698KB](52) SpringerLink
Abstract:
An explosion-welded technology was induced to manufacture the GH3535/316H bimetallic plates to provide a more cost-effective structural material for ultrahigh temperature, molten salt thermal storage systems. The microstructure of the bonding interfaces were extensively investigated by scanning electron microscopy, energy dispersive spectrometry, and an electron probe microanalyzer. The bonding interface possessed a periodic, wavy morphology and was adorned by peninsula- or island-like transition zones. At higher magnification, a matrix recrystallization region, fine grain region, columnar grain region, equiaxed grain region, and shrinkage porosity were observed in the transition zones and surrounding area. Electron backscattered diffraction demonstrated that the strain in the recrystallization region of the GH3535 matrix and transition zone was less than the substrate. Strain concentration occurred at the interface and the solidification defects in the transition zone. The dislocation substructure in 316H near the interface was characterized by electron channeling contrast imaging. A dislocation network was formed in the grains of 316H. The microhardness decreased as the distance from the welding interface increased and the lowest hardness was inside the transition zone.
 
Microstructure evolution and mechanical properties of Mg–9Al–1Si–1SiC composites processed by multi-pass equal-channel angular pressing at various temperatures
Xiang-peng Zhang, Hong-xia Wang, Li-ping Bian, Shao-xiong Zhang, Yong-peng Zhuang, Wei-li Cheng, and Wei Liang
  Available online 21 June 2020, https://doi.org/10.1007/s12613-020-2123-z
[FullText HTML](1631) [PDF 1574KB](32) SpringerLink
Abstract:
In this study, Mg–9Al–1Si–1SiC (wt%) composites were processed by multi-pass equal-channel angular pressing (ECAP) at various temperatures, and their microstructure evolution and strengthening mechanism were explored. Results showed that the as-cast microstructure was composed of an α-Mg matrix, discontinuous Mg17Al12 phase, and Chinese script-shaped Mg2Si phase. After solution treatment, almost all of the Mg17Al12 phases were dissolved into the matrix, whereas the Mg2Si phases were not. The subsequent multi-pass ECAP at different temperatures promoted the dynamic recrystallization and uniform distribution of the Mg17Al12 precipitates when compared with the multi-pass ECAP at a constant temperature. A large number of precipitates can effectively improve the nucleation ratio of recrystallization through a particle-stimulated nucleation mechanism. In addition, the SiC nanoparticles were mainly distributed at grain boundaries, which effectively prevented dislocation movement. The excellent comprehensive mechanical properties can be attributed to grain boundary strengthening and Orowan strengthening.
 
Rapid removal of copper impurity from bismuth–copper alloy melts via super-gravity separation
Xiao-chun Wen, Lei Guo, Qi-peng Bao, and Zhan-cheng Guo
  Available online 17 June 2020, https://doi.org/10.1007/s12613-020-2118-9
[FullText HTML](1698) [PDF 2779KB](26) SpringerLink
Abstract:
A green method of super-gravity separation, which can enhance the filtration process of bismuth and copper phases, was investigated and discussed for the rapid removal of copper impurity from bismuth–copper alloy melts. After separation by the super-gravity field, the bismuth-rich liquid phases were mainly filtered from the alloy melt along the super-gravity direction, whereas most of the fine copper phases were retained in the opposite direction. With optimized conditions of separation temperature at 280°C, gravity coefficient at 450, and separation time at 200 s, the mass proportion of the separated bismuth from Bi–2wt%Cu and Bi–10wt%Cu alloys reached 96% and 85% respectively, which indicates the minimal loss of bismuth in the residual. Simultaneously, the removal ratio of impurity copper reached 88% and 98%. Furthermore, the separation process could be completed rapidly and is environmentally friendly and efficient.
Research Article
Microstructural evolution and thermal conductivity of diamond/Al composites during thermal cycling
Ping-ping Wang, Guo-qin Chen, Wen-jun Li, Hui Li, Bo-yu Ju, Murid Hussain, Wen-shu Yang, and Gao-hui Wu
  Available online 10 June 2020, https://doi.org/10.1007/s12613-020-2114-0
[FullText HTML](1973) [PDF 941KB](46) SpringerLink
Abstract:
The microstructural evolution and performance of diamond/Al composites during thermal cycling has rarely been investigated. In the present work, the thermal stability of diamond/Al composites during thermal cycling for up to 200 cycles was explored. Specifically, the thermal conductivity (λ) of the composites was measured and scanning electron microscopy of specific areas in the same samples was carried out to achieve quasi-in situ observations. The interface between the (100) plane of diamond and the Al matrix was well bonded with a zigzag morphology and abundant needle-like Al4C3 phases. By contrast, the interface between the (111) plane of diamond and the Al matrix showed weak bonding and debonded during thermal cycling. The debonding length increased rapidly over the first 100 thermal cycles and then increased slowly in the following 100 cycles. The λ of the diamond/Al composites decreased abruptly over the initial 20 cycles, increased afterward, and then decreased monotonously once more with increasing number of thermal cycles. Decreases in the λ of the Al matrix and the corresponding stress concentration at the diamond/Al interface caused by thermal mismatch, rather than interfacial debonding, may be the main factors influencing the decrease in λ of the diamond/Al composites, especially in the initial stages of thermal cycling.
 
Effect of Co substitution on the structural, dielectric, and optical properties of KBiFe2O5
K. Chandrakanta, R. Jena, P. Pal, Md.F. Abdullah, S.D. Kaushik, and A.K. Singh
  Available online 31 May 2020, https://doi.org/10.1007/s12613-020-2110-4
[FullText HTML](1707) [PDF 1142KB](27) SpringerLink
Abstract:
Cobalt (Co)-modified brownmillerite KBiFe2O5 (KBFO; [KBiFe2(1−x)Co2xO5 (x = 0, 0.05)]) polycrystalline is synthesized following the solid-state reaction route. Rietveld refinement of X-ray diffraction data confirmed the phase purity of KBFO and KBiFe1.9Co0.1O5 (KBFCO). The optical bandgap energy (Eg) of KBFO decreased from 1.59 to 1.51 eV because of Co substitution. The decrease in bandgap can be attributed to the tilting of the Fe–O tetrahedral structure of KBFCO. The observed room-temperature Raman peaks of KBFCO shifted by 3 cm−1 toward a lower wavenumber than that of KBFO. The shift in Raman active modes can be attributed to the change in the bond angles and bond lengths of the Fe–O tetrahedral structure and modification in response to oxygen deficiency in KBFO because of Co doping. Compared with that of KBFO, the frequency-dependent dielectric constant and dielectric loss of KBFCO decrease at room temperature, which is a consequence of the reduction in oxygen migration and modification in response to vibrational modes present in the sample.
Research Article
Adsorption properties of V(IV) on resin-activated carbon composite electrodes in capacitive deionization
Xiao-man Tian, Shen-xu Bao, and Yi-min Zhang
  Available online 17 May 2020, https://doi.org/10.1007/s12613-020-2100-6
[FullText HTML](1655) [PDF 1333KB](18) SpringerLink
Abstract:
Composite electrodes prepared by cation exchange resins and activated carbon (AC) were used to adsorb V(IV) in capacitive deionization (CDI). The electrode made of middle resin size (D860/AC M) had the largest specific surface area and mesoporous content than two other composite electrodes. Electrochemical analysis showed that D860/AC M presents higher specific capacitance and electrical double layer capacitor than the others, and significantly lower internal diffusion impedance. Thus, the highest adsorption capacity and rate of V(IV) are inhibited in the three electrodes. The intra-particle diffusion model fits well in the initial adsorption stage, while the liquid film diffusion model is more suitable for fitting at the later stage. The pseudo-second-order kinetic model is fit for the entire adsorption process. The adsorption of V(IV) on the composite electrode follows that of the Freundlich isotherm. Thermodynamic analysis indicates that this condition is an exothermic process with entropy reduction and the electric field force plays a dominant role in the CDI process. This work aims to improve our understanding of the ion adsorption behaviors and mechanisms on the composite electrodes in CDI.
Research Article
Shape of slab solidification end under non-uniform cooling and its influence on the central segregation with mechanical soft reduction
Jie Li, Yan-hui Sun, Hang-hang An, and Pei-yuan Ni
  Available online 9 May 2020, https://doi.org/10.1007/s12613-020-2089-x
[FullText HTML](1711) [PDF 1826KB](21) SpringerLink
Abstract:
In order to study the effect of continuous casting process parameters on the shape of slab solidification end under non-uniform cooling, a solidification model of a continuous-cast slab with non-uniform cooling condition was established with ProCAST software. The model was verified by the results of nail shooting tests and the infrared temperature measurement equipment. Four characteristic parameters were defined to evaluate the uniformity of the shape of slab solidification end. The results showed that the nonuniformity at the beginning and end of solidification, the solidification end length, and the solidification unevenness increased with the rise of casting speed. For each 10°C increase of superheat, the solidification unevenness increased by about 0.022. However, the effect of superheat on the solidification end length can be ignored. The secondary cooling strength showed minimal effect on the nonuniformity at the beginning and end of solidification. With the increase in secondary cooling intensity, the solidification end length decreased, but the solidification unevenness increased. In addition, the central segregation of the slab produced with and without the mechanical soft reduction (MSR) process was investigated. The transverse flow of molten steel with low solid fraction influenced the central segregation morphology under MSR.
Research Article
Effects of cellulose nanocrystals on the acid resistance of cementitious composites
Lin-ping Wu, Guang-ping Huang, Chao-shi Hu, and Wei Victor Liu
  Available online 9 May 2020, https://doi.org/10.1007/s12613-020-2087-z
[FullText HTML](1699) [PDF 1426KB](23) SpringerLink
Abstract:
Acid mine drainage presents an important threat to cementitious structures. This study is aimed at investigating the effect of cellulose nanocrystals (CNCs) on the acid resistance of cementitious composites. CNCs were added to mortar mixtures as additives at cement volume ratios of 0.2vol%, 0.4vol%, 1.0vol%, and 1.5vol%. After 28 d of standard curing, the samples were immersed in a sulfuric acid with a pH value of 2 for 75 d. The unconfined compressive strength (UCS) test, the density, water absorption, void volume test, and thermogravimetric analysis were carried out to investigate the properties of CNC mixtures before sulfuric acid immersion. It was found that the addition of CNC reduced the volume of permeable voids and increased the hydration degree and mechanical strength of the samples. Changes in mass and length were monitored during immersion to evaluate the acid resistance of mixtures. The mixture with 0.4vol% CNC showed a reduced mass change and length change indicating its improved acid resistance.
Research Article
Highly efficient nanocatalyst Ni1Co9@graphene for hydrolytic dehydrogenation of sodium borohydride
Juan Wang, Li-jun Yang, Xiao-chong Zhao, Pan Yang, Wei Cao, and Qing-song Huang
  Available online 9 May 2020, https://doi.org/10.1007/s12613-020-2090-4
[FullText HTML](1804) [PDF 933KB](21) SpringerLink
Abstract:
Bimetal materials derived from transition metals can be good catalysts in some reactions. When supported on graphene (GP), these catalysts feature remarkable performance in the hydrolysis of sodium borohydride. To obtain such catalysts easily and efficiently, a simple thermal reduction strategy was used in this study, and NixCo10−x series bimetal catalysts were prepared. Among all the catalysts, Ni1Co9 exhibited the best catalytic performance. The turnover frequency (TOF) related to the total number of atoms within the bimetallic nanoparticles reached 603.82 mL·mmol−1·min−1 at 303 K. Furthermore, graphene was introduced as a supporting frame. The Ni1Co9@Graphene (Ni1Co9@GP) had a large surface area and high TOF, 25534 mL·mmol−1·min−1, at 303 K. The Ni1Co9@GP exhibited efficient catalytic properties for H2 generation in alkaline solution because of its high specific surface area. Moreover, the high kinetic isotope effect observed in the kinetic studies suggests that using D2O led to the oxidative addition of an O–H bond of water in the rate-determining step.
Research Article
Fabrication and properties of silver-based composites reinforced with carbon-coated Ti3AlC2
Yong-fa Zhu, Wu-bian Tian, Dan-dan Wang, Heng Zhang, Jian-xiang Ding, Pei-gen Zhang, and Zheng-ming Sun
  Available online 12 April 2020, https://doi.org/10.1007/s12613-020-2064-6
[FullText HTML](1734) [PDF 1038KB](14) SpringerLink
Abstract:
Ti3AlC2-reinforced Ag-based composites, which are used as sliding current collectors, electrical contacts, and electrode materials, exhibit remarkable performances. However, the interfacial reactions between Ag and Ti3AlC2 significantly degrade the electrical and thermal properties of these composites. To diminish these interfacial reactions, we fabricated carbon-coated Ti3AlC2 particles (C@Ti3AlC2) as reinforcement and prepared Ag–10wt%C@Ti3AlC2 composites with carbon-layer thicknesses ranging from 50–200 nm. Compared with the uncoated Ag–Ti3AlC2 composite, Ag–C@Ti3AlC2 was found to have a better distribution of Ti3AlC2 particles. With increases in the carbon-layer thickness, the Vickers hardness value and relative density of Ag–C@Ti3AlC2 gradually decreases. With a carbon-layer thickness of 150 nm, we obtained the lowest resistivity of Ag–C@Ti3AlC2 of 29.4 135.5×10−9 Ω·m, which is half that of Ag–Ti3AlC2 (66.7 × 10−9 Ω·m). The thermal conductivity of Ag–C@Ti3AlC2 reached a maximum value of 135.5 W·m−1·K−1 with a 200-nm carbon coating (~1.8 times that of Ag–Ti3AlC2). These results indicate that the carbon-coating method is a feasible strategy for improving the performance of Ag–C@Ti3AlC2 composites.
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Editorial
Editorial for special issue on advanced materials for energy storage and conversion
Qiao-bao Zhang, Yong-chang Liu, and Xiao-bo Ji
2021, vol. 28, no. 10, pp. 1545-1548. https://doi.org/10.1007/s12613-021-2354-7
[FullText HTML](238) [PDF 515KB](17) SpringerLink
Abstract:
Invited Review
Review of silicon-based alloys for lithium-ion battery anodes
Zhi-yuan Feng, Wen-jie Peng, Zhi-xing Wang, Hua-jun Guo, Xin-hai Li, Guo-chun Yan, and Jie-xi Wang
2021, vol. 28, no. 10, pp. 1549-1564. https://doi.org/10.1007/s12613-021-2335-x
[FullText HTML](1017) [PDF 2567KB](90) SpringerLink
Abstract:
Silicon (Si) is widely considered to be the most attractive candidate anode material for use in next-generation high-energy-density lithium (Li)-ion batteries (LIBs) because it has a high theoretical gravimetric Li storage capacity, relatively low lithiation voltage, and abundant resources. Consequently, massive efforts have been exerted to improve its electrochemical performance. While some progress in this field has been achieved, a number of severe challenges, such as the element’s large volume change during cycling, low intrinsic electronic conductivity, and poor rate capacity, have yet to be solved. Methods to solve these problems have been attempted via the development of nanosized Si materials. Unfortunately, reviews summarizing the work on Si-based alloys are scarce. Herein, the recent progress related to Si-based alloy anode materials is reviewed. The problems associated with Si anodes and the corresponding strategies used to address these problems are first described. Then, the available Si-based alloys are divided into Si/Li-active and inactive systems, and the characteristics of these systems are discussed. Other special systems are also introduced. Finally, perspectives and future outlooks are provided to enable the wider application of Si-alloy anodes to commercial LIBs.
Invited Review
Practical development and challenges of garnet-structured Li7La3Zr2O12 electrolytes for all-solid-state lithium-ion batteries: A review
Zao-hong Zhang, Tao Wei, Jia-hao Lu, Qi-ming Xiong, Yue-han Ji, Zong-yuan Zhu, and Liu-ting Zhang
2021, vol. 28, no. 10, pp. 1565-1583. https://doi.org/10.1007/s12613-020-2239-1
[FullText HTML](1326) [PDF 2037KB](88) SpringerLink
Abstract:
All-solid-state Li-ion batteries (ASSLIBs) have been widely studied to achieve Li-ion batteries (LIBs) with high safety and energy density. Recent reviews and experimental papers have focused on methods that improve the ionic conductivity, stabilize the electrochemical performance, and enhance the electrolyte/electrode interfacial compatibility of several solid-state electrolytes (SSEs), including oxides, sulfides, composite and gel electrolytes, and so on. Garnet-structured Li7La3Zr2O12 (LLZO) is highly regarded an SSE with excellent application potential. However, this type of electrolyte also possesses a number of disadvantages, such as low ionic conductivity, unstable cubic phase, and poor interfacial compatibility with anodes/cathodes. The benefits of LLZO have urged many researchers to explore effective solutions to overcome its inherent limitations. Herein, we review recent developments on garnet-structured LLZO and provide comprehensive insights to guide the development of garnet-structured LLZO-type electrolytes. We not only systematically and comprehensively discuss the preparation, element doping, structure, stability, and interfacial improvement of LLZOs but also provide future perspectives for these materials. This review expands the current understanding on advanced solid garnet electrolytes and provides meaningful guidance for the commercialization of ASSLIBs.
Invited Review
Solid electrolyte–electrode interface based on buffer therapy in solid-state lithium batteries
Lei-ying Wang, Li-fan Wang, Rui Wang, Rui Xu, Chun Zhan, Woochul Yang, and Gui-cheng Liu
2021, vol. 28, no. 10, pp. 1584-1602. https://doi.org/10.1007/s12613-021-2278-2
[FullText HTML](624) [PDF 1727KB](52) SpringerLink
Abstract:
In the past few years, the all-solid lithium battery has attracted worldwide attentions, the ionic conductivity of some all-solid lithium-ion batteries has reached 10−3–10−2 S/cm, indicating that the transport of lithium ions in solid electrolytes is no longer a major problem. However, some interface issues become research hotspots. Examples of these interfacial issues include the electrochemical decomposition reaction at the electrode–electrolyte interface; the low effective contact area between the solid electrolyte and the electrode etc. In order to solve the issues, researchers have pursued many different approaches. The addition of a buffer layer between the electrode and the solid electrolyte has been at the center of this endeavor. In this review paper, we provide a systematic summarization of the problems on the electrode–solid electrolyte interface and detailed reflection on the latest works of buffer-based therapies, and the review will end with a personal perspective on the improvement of buffer-based therapies.
Research Article
Carbon dot-modified silicon nanoparticles for lithium-ion batteries