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Research Article
In situ kinetics and flocs conformation studies of kaolinite flocculated by Chi-g-CPAM
Ruijing Xu, Wenjie Zou, Bo Rao, Wei Zhao, Ting Wang, and  Zhijun Zhang
, Available online 2 July 2022, https://doi.org/10.1007/s12613-022-2522-4
Abstract:

This study presents a comparative study of the flocculation behavior of kaolinite induced by chitosan-graft-poly(acrylamide-dimethyl diallyl ammonium chloride) (Chi-g-CPAM) and a commercial cationic polyacrylamide (CPAM). The floculation behaviour was characterised in terms of both flocculation kinetics and the corresponding morphology changes during flocculation. Both Chi-g-CPAM and CPAM were grafted from silica wafers by means of atom transfer radical polymerization (ATRP). The quartz crystal microbalance with dissipation (QCM-D) tests were conducted. The equilibrium time flocculated by Chi-g-CPAM was found to be 0.46 times as high as that of CPAM, together with a larger total mass of kaolinite layer. The flocculation behaviour by Chi-g-CPAM can be well captured by a pseudo-first-order model. In contrast, the presence of CPAM leads to a more complex kinetics. A relatively larger fitting slope (0.4663) was obtained at the initial stage but drops to 0.2026 after 800 min, indicating a densification process caused by CPAM. The flocculation kinetics of CPAM can be captured by the Elovich model for the inital stage but the combination of pseudo-first-order and pseudo-second-order models for the latter stages, which can be attributed to the long chain of CPAM. With a dosage of 75 g/t, the settling test with Chi-g-CPAM exhibits the same turbidity in the supernatant but a smaller layer thickness of the settlement compared with that of CPAM. The study enables a better understanding of the flocculation behavior and contributes to the development of efficient flocculants in mineral processing and tailings treatment.  

Research Article
In/C hexagonal nanorods derived from In-MOF and graphene nanosheets composites with high-performance electromagnetic wave absorption
Rao Zhang, Congpu Mu, Bochong Wang, Jianyong Xiang, Kun Zhai, Tianyu Xue, and  Fusheng Wen
, Available online 17 June 2022, https://doi.org/10.1007/s12613-022-2520-6
Abstract:

In recent years, electromagnetic (EM) wave absorption has been extensively investigated for solving EM radiation and pollution. The metal-organic frameworks (MOFs) have attached attention due to its low density and unique structure, which can meet the requirements of lightweight, strong reflection loss (RL) and wide absorption bandwidth of EM wave absorption materials. In this manuscript, indium metal nanoparticles/porous carbon (In/C) nanorods composites are prepared via the pyrolysis of nanorods-like In-MOFs at low temperature of 450 oC. Meatal indium nanoparticles are evenly attached and embedded on porous carbon. Low electrical conductivity of In/C nanorods is unfavorable to EM wave absorption performance, which is due to the low temperature carbonization. Thus, graphene nanosheets (Gr) with high electrical conductivity are introduced to adjust the EM parameters of In/C nanorods for enhancing EM wave absorption. The minimum RL of In/C-Gr-4 composites is up to -43.7 dB under a thin thickness of 1.30 mm. In addition, when thickness of In/C-Gr composites is further reduced to 1.14 mm, the minimum RL of -39.3 dB for EM wave of 16.1 GHz and effective absorption bandwidth of 3.7 GHz (from 14.3 to 18.0 GHz) are achieved at high frequency range, too. This work indicates that In/C-Gr composites as EM wave absorption materials have strong RL, thin thickness and lightweight.

Research Article
Isothermal kinetic analysis on reduction of solid/liquid wustite by hydrogen
Jianliang Zhang, Yang Li, Zhengjian Liu, Tengfei Wang, Yaozu Wang, Kejiang Li, Guilin Wang, Tao Xu, and  Yong Zhang
, Available online 8 June 2022, https://doi.org/10.1007/s12613-022-2518-0
Abstract:

In this paper, iso-thermal thermogravimetric analysis was used to study the reduction process of solid/liquid wustite by hydrogen. Results show that wustite in both states can be reduced entirely at all temperatures. The thermal and kinetic conditions for the hydrogen reduction of molten phases are better than when the reactants and products are in the solid state, with a higher reaction rate. The hydrogen reduction of different wustite phases fits the mampel power model: f(α)=2α1/2 well, and this model is independent of the phase state. The average apparent activation energy of the reduction process calculated by the iso-conversional method is 5.85 kJ·mol-1 and 104.74 kJ·mol-1, when both reactants and products are in the solid state and the molten state, respectively. These values generally agree with that calculated by the model fitting method.

Research Article
Fabrication and characterization of environmental resistance and flexible microwave absorber sheet based on a composite filler with waste fly ash as the core filled silicone rubber
Qiuying Li, Yiheng Lu, and  Zhuoyan Shao
, Available online 31 May 2022, https://doi.org/10.1007/s12613-022-2517-1
Abstract:

In this study, a new type of composite filler was designed by a modified sol-gel method using solid waste fly ash, Fe(NO3)3∙9H2O and Ni(NO3)2∙6H2O as raw materials. The composite filler was a spherical core-shell structure composed of fly ash as the core and NiFe2O4 as the shell. Further, the composite filler was added into the silicone rubber to fabricate the high temperature vulcanized microwave absorption materials. XRD, FTIR, XPS and SEM confirmed NiFe2O4 was successfully coated on the surface of fly ash and formed a uniform and continuous coating layer. As expected, silicone rubber filled with the composite filler had a minimum reflection loss of -23.8 dB at 17.5 GHz with a thickness of 1.8 mm, while the effective absorption bandwidth was as high as 12 GHz. The addition of the composite filler greatly enhanced the microwave absorption properties of the system, which were resulted from multiple losses mechanism: interface polarization losses, magnetic losses and multiple reflection losses. Also, silicone rubber filled with the composite filler exhibited excellent thermal stability, high flexibility, environmental resistance, and hydrophobicity compared with silicone rubber. Therefore, this work not only responds to the green chemistry to achieve efficient fly ash recovery, but also devises a new strategy to prepare microwave absorption materials with strong potential for military and civilian applications.

Research Article
Effect of Cu addition on the microstructure and tribological performance of Ni60 directional structure coating
Xiaotian Yang, Xinhua Wang, Jun Zhou, Hengli Wei, Rong Zeng, and  Wensheng Li
, Available online 28 May 2022, https://doi.org/10.1007/s12613-022-2516-2
Abstract:

The Ni60/15wt.%Cu coating with directional structure was prepared by composite technology of flame spraying, induction remelting and forced cooling, and the effect of Cu on the microstructure, phase, hardness and wear performance of Ni60 coatings was investigated. The results show that the addition of Cu makes the microstructure of Ni60 directional structure coating more compact, and Cu is mainly enriched within the crystal grain, resulting in the formation of Cu3.8Ni as bonding phase. Compared with Ni60 coating with directional structure, the Ni60/Cu coating with directional structure shows lower hardness, lower friction coefficient and lower wear rate, which indicate that the element Cu can enhance the antifriction performance of Ni60 directional structure coating effectively.

Research Article
Texture evolution and mechanical anisotropy of an ultrafine/nano-grained pure copper tube processed via hydrostatic tube cyclic expansion extrusion (HTCEE)
Seyed Moien Faregh, Ghader Faraji, Mahmoud Mousavi Mashhadi, and  Mohammad Eftekhari
, Available online 17 May 2022, https://doi.org/10.1007/s12613-022-2514-4
Abstract:

Texture evolution and mechanical anisotropic behavior of an ultrafine-grained (UFG) pure copper tube processed by recently introduced method of hydrostatic tube cyclic expansion extrusion (HTCEE) was investigated. For the UFG tube, different deformation behavior and a significant anisotropy in tensile properties were recorded along the longitudinal and peripheral directions. The HTCEE process increased the yield strength and the ultimate strength in the axial direction by 3.6 and 1.67 times, respectively. Also, this process increased the yield strength and the ultimate strength in the peripheral direction by 1.15 and 1.12 times, respectively. The ratio of ultimate tensile strength in the peripheral direction to that in the axial direction, as a criteria for mechanical anisotropy, are 1.7 and 1.16 for the as-annealed coarse-grained and the HTCEE processed UFG tube, respectively. So, the results are indicative of a reducing effect of the HTCEE process on the mechanical anisotropy. Also, after HTCEE process, a low loss of ductility was observed in both directions, which is another advantage of HTCEE process. Hardness measurements revealed slight increment of hardness values in peripheral direction, which is in agreement with the trend of tensile tests. Texture analysis was conducted in order to determine the oriental distribution of the grains. The obtained {111} pole figures demonstrate the texture evolution, and reaffirm the anisotropy observed in mechanical properties. SEM micrographs showed that different modes of fracture occurred after tensile testing in the two orthogonal directions.

Research Article
Corrosion behavior of single- and poly-crystalline dual-phase TiAl-Ti3Al alloy in NaCl solution
Dongpeng Wang, Guang Chen, Anding Wang, Yuxin Wang, Yanxin Qiao, Zhenguang Liu, Zhixiang Qi, and  Chain Tsuan Liu
, Available online 11 May 2022, https://doi.org/10.1007/s12613-022-2513-5
Abstract:

To clarify the correlation of single-crystalline structure with corrosion performance in high-strength TiAl alloys, electrochemical and surface characterization was performed by comparing Ti-45Al-8Nb dual-phase single crystals with their polycrystalline counterparts in NaCl solution. Polarization curves show a lower corrosion rate and a higher pitting potential of ~280 mV for the dual-phase single crystals. Electrochemical impedance spectroscopy and potentiostatic polarization plots revealed a higher impedance of the charge transfer through the compact passive film. Surface composition analysis indicated a compact film with more content of Nb, as twice as that in the film on the polycrystals. Our results reflect that the dual-phase Ti-45Al-8Nb single crystals possess a higher corrosion resistance in NaCl solution, compared with their polycrystalline counterpart, arising from a more homogeneous microstructure and composition distribution.

Research Article
Kinetic mechanism analysis of iron ore powder reaction with hydrogen-carbon monoxide
Xudong Mao, Pritesh Garg, Xiaojun Hu, Yuan Li, Samik Nag, Saurabh Kundu, and  Jianliang Zhang
, Available online 4 May 2022, https://doi.org/10.1007/s12613-022-2512-6
Abstract:

The powder of iron ore was isothermally reduced at 1023 K-1373 K with hydrogen-carbon monoxide gas mixture (from 0%H2-100%CO to 100%H2-0%CO). Results indicate that the whole reduction process could be divided into two parts that proceed in series. The first part represents a double-step reduction reaction (Fe2O3→ Fe3O4→FeO), for which the kinetic condition is more feasible compared to the second part representing a single-step reduction reaction (FeO→Fe). The influence of hydrogen partial pressure on reduction rate gradually increases as the reaction proceeds. The average reduction rate of hematite ore with pure hydrogen is about 3 times and 4 times higher than that with pure carbon monoxide at 1173 K and 1373 K, respectively. Besides, the logarithm of the average rate is linear to the composition of the gas mixture. Hydrogen can prominently promote the carbon deposition reaction at 1023 K, which improves up to about 30%. The apparent activation energy of the reduction stage increases from about 35 to 45.4 kJ/mol with the increase of hydrogen content from 20% to 100%, which reveals the probable rate controlling step at this stage is combined gas diffusion and interfacial chemical reaction.

Research Article
The effects of highly dispersed Ni nano-particles on the hydrogen storage performance of MgH2
Nuo Xu, Zirui Yuan, Zhihong Ma, Xinli Guo, Yunfeng Zhu, Yongjin Zou, and  Yao Zhang
, Available online 29 April 2022, https://doi.org/10.1007/s12613-022-2510-8
Abstract:

MgH2 with a large hydrogen capacity has been regarded as a promising hydrogen storage material. However, it still suffers from high thermal stability and sluggish kinetics. In this paper, highly dispersed nano-Ni has been successfully prepared by the polyol reduction method with an average size of 2.14 nm, which significantly improved the de/rehydrogenation properties of MgH2. The MgH2-10wt.% nano-Ni sample starts releasing H2 at 497 K and roughly 6.2wt.% H2 has been completely liberated at 598 K. The rehydrogenation kinetics of the sample are also greatly improved and the adsorption capacity reaches 5.3wt.% H2 in 1000 s at 482 K and under 3 MPa hydrogen pressure. Moreover, the activation energies of de/rehydrogenation of the MgH2-10wt.% nano-Ni sample are reduced to 88 ± 2 kJ mol−1 and 87 ± 1 kJ mol−1, respectively. In addition, the thermal stability of the MgH2-10wt.% nano-Ni system is reduced by 5.5 kJ (mol H2)−1 from that of pristine MgH2. It means that nano-Ni significantly improves both the thermodynamic and kinetic performances of the de/re-hydrogenation of MgH2, serving as a bi-functional additive of both reagent and catalyst.

Research Article
Non-stoichiometry – A bonus for plasma processing of nickel
Kali Charan Sabat
, Available online 29 April 2022, https://doi.org/10.1007/s12613-022-2507-3
Abstract:

Thermodynamics and kinetics are potential pathways for the extraction of metals and alloys. Due to the thermodynamic and kinetic benefits provided by cold hydrogen plasma (CHP), several metals and alloys could be extracted from their oxides/ores inside a microwave oven, utilizing less power than the residential microwave oven. CHP creates excited species, which reduce the thermodynamic and kinetic barriers to reduction, thereby enabling easier reduction of metal oxides and ores. The present work reports the additional thermodynamic and kinetic benefits afforded by the non-stoichiometry of nickel oxide (Ni1-xO) due to excess oxygen. The Gibbs standard free energy (∆Go) of reduction of Ni1-xO is significantly reduced due to excess oxygen. The distribution of excess oxygen is not uniform, with the surface containing more than the bulk. Due to the surplus oxygen, the decrease in ∆Go is more pronounced at the surface. This excess oxygen at the surface also kicks off the reduction process right away, promoting kinetics. Because of the favorable thermodynamics and kinetics conditions caused by the excess oxygen, a 7.5 x 10-6 kg pellet could be reduced in 1200 seconds using 600 W microwave power and a hydrogen flow rate of 1.166 x 10-6 m3 s-1. The non-stoichiometry associated with Ni1-xO is a bonus in the plasma processing of nickel.

Research Article
Fluidization behavior and reduction kinetics of pre-oxidized magnetite-based iron ore in a hydrogen-induced fluidized bed
Heng Zheng, Oday Daghagheleh, Thomas Wolfinger, Bernd Taferner, Johannes Schenk, and  Runsheng Xu
, Available online 29 April 2022, https://doi.org/10.1007/s12613-022-2511-7
Abstract:

The influence of different pre-oxidation temperature and pre-oxidation degree on the reduction and fluidization behaviors of magnetite-based iron ore was investigated in a hydrogen-induced fluidized bed. The raw magnetite-based iron ore was pre-oxidized at 800 and 1000 °C for a certain time to reach a partly oxidation and deeply oxidation state. The structure and morphology of the reduced particles were analyzed via optical microscope and scanning electron microscopy (SEM). The reaction kinetic mechanism was determined based on the double-logarithm analysis. The results indicate that the materials with higher oxidation temperature and wider particle size range showed better fluidization behaviors. While lower oxidation temperature was more beneficial for the reduction rate, especially in the later reduction stage. The pre-oxidation degree shows no obvious influence on the fluidization and reduction behaviors. The reduction progress can be divided into three stages. The reduction mechanism was discussed combing the surface morphology and phase structure.

Research Article
Achieving a high-strength dissimilar joint of T91 heat-resistant steel to 316L stainless steel via friction stir welding
Zhiwei Wang, Min Zhang, Cong Li, Fenglei Niu, Hao Zhang, Peng Xue, Dingrui Ni, Bolv Xiao, and  Zongyi Ma
, Available online 29 April 2022, https://doi.org/10.1007/s12613-022-2508-2
Abstract:

The reliable welding of T91 heat-resistant steel to 316L stainless steel is a considerable issue for ensuring the safety in service of ultra-supercritical power generation unit and nuclear fusion reactor, but the high-quality dissimilar joint of these two steels was difficult to be obtained by traditional fusion welding methods. Here we improved the structure-property synergy in a dissimilar joint of T91 steel to 316L steel via friction stir welding. A defect-free joint with a large bonding interface was produced using a small-sized tool under a relatively high welding speed. The bonding interface was involved in a mixing zone with both mechanical mixing and metallurgical bonding. No obvious material softening was detected in the joint except a negligible hardness decline of only ~10 HV in the heat-affected zone of the T91 steel side due to the formation of ferrite phase. The welded joint exhibited an excellent ultimate tensile strength as high as that of the 316L parent metal and a greatly enhanced yield strength on account of the dependable bonding and material renovation in the weld zone. This work recommends a promising technique for producing high-strength weldments of dissimilar nuclear steels.

Research Article
Efficient microwave absorption achieved through in situ construction of core-shell CoFe2O4@mesoporous carbon hollow spheres
Lianggui Ren, Yiqun Wang, Xin Zhang, Qinchuan He, and  Guanglei Wu
, Available online 29 April 2022, https://doi.org/10.1007/s12613-022-2509-1
Abstract:

Utilizing of cobalt ferrite (CoFe2O4) with good chemical stability and magnetic loss ability to prepare composites with a special structure can effectively improve the material's absorbing performance. Herein, introducing CoFe2O4 magnetic particles into the hollow mesoporous carbon material through an unsophisticated in-situ preparation method, the author of the research has synthesized the CoFe2O4@ mesoporous carbon hollow spheres (MCHS) with core-shell structure. The content of MCHS and cobalt ferrite CoFe2O4 and the size of the pores can be changed to coordinate the magnetic loss and dielectric loss. In light of previous researches of the same author, the minimum reflection loss (RLmin) of CoFe2O4@MCHS composites occurs as -29.7 dB when the microwave frequency is modulated to 5.8 GHz. Besides, the effective absorption bandwidth (EAB) emerges as 3.7 GHz, with the thickness being 2.5 mm and the filling rate being 30%. The good electromagnetic wave (EMW) absorption performance is generated by the special core-shell structure and exceptional impedance matching. The results show that tweaking the ratio of MCHS and CoFe2O4, the impedance match absorbing properties of CoFe2O4@MCHS composites are altered. Corresponding absorption mechanism has been discussed within the paper. This method provides a feasible solution to prepare core-shell structure microwave absorbents and is much promising for practical use.

Research Article
Activation mechanism of ammonium oxalate with pyrite in the lime system and its response to flotation separation pyrite from arsenopyrite
Runpeng Liao, Shuming Wen, Qicheng Feng, Jiushuai Deng, and  Hao Lai
, Available online 22 April 2022, https://doi.org/10.1007/s12613-022-2505-5
Abstract:

The activation properties of ammonium oxalate on the flotation of pyrite and arsenopyrite in the lime system were studied in this work. Single mineral flotation tests showed that the ammonium oxalate strongly activated pyrite in high alkalinity and high Ca2+ system, whereas arsenopyrite was almost unaffected. In mineral mixtures tests, the recovery difference between pyrite and arsenopyrite after adding ammonium oxalate is more than 85%. After ammonium oxalate and ethyl xanthate treatment, the hydrophobicity of pyrite increased significantly, and the contact angle increased from 66.62° to 75.15° and then to 81.21°. After ammonium oxalate treatment, the amount of ethyl xanthate adsorption on the pyrite surface significantly increased and was much greater than that on the arsenopyrite surface. Zeta potential measurements showed that after activation by ammonium oxalate, there was a shift in the zeta potential of pyrite to more negative values by adding xanthate. X-ray photoelectron spectroscopy test showed that after ammonium oxalate treatment, the O 1s content on the surface of pyrite decreased from 44.03% to 26.18%, and the S 2p content increased from 14.01% to 27.26%, which confirmed that the ammonium oxalate-treated pyrite surface was more hydrophobic than the untreated surface. Therefore, ammonium oxalate may be used as a selective activator of pyrite in the lime system, which achieves an efficient flotation separation of S–As sulfide ores under high alkalinity and high Ca2+ concentration conditions.

Research Article
Experimental study on thermal and mechanical properties of tailings-based cemented paste backfill with CaCl2·6H2O/expanded vermiculite shape stabilized phase change materials
Xiaoyan Zhang, Tianrun Cao, Lang Liu, Baoyun Bu, Yaping Ke, and  Qiangqiang Du
, Available online 19 April 2022, https://doi.org/10.1007/s12613-022-2503-7
Abstract:

CaCl2·6H2O/expanded vermiculite shaped stabilized phase change materials (CEV) was prepared by atmospheric impregnation method. Using gold mine tailings as aggregate of cemented paste backfill (CPB) material, the CPB with CEV added was prepared, and the specific heat capacity, thermal conductivity and uniaxial compressive strength (UCS) of CPB with different cement-tailing ratios and CEV addition ratios were tested, the influence of the above variables on the thermal and mechanical properties of CPB was analyzed. The results show that the maximum encapsulation capacity of expanded vermiculite for CaCl2·6H2O is about 60%, and the melting and solidification enthalpy of CEV can reach 98.87 J/g and 97.56 J/g respectively. For the CPB without CEV, the specific heat capacity, thermal conductivity and UCS decrease with the decrease of cement-tailing ratio. For the CPB with CEV added, with the increase of CEV addition ratio, the specific heat capacity increases significantly, and its sensible heat storage capacity and latent heat storage capacity can be increased by at least 10.74% and 218.97% respectively after adding 12% CEV. However, the addition of CEV leads to the increase of pores, and its thermal conductivity and the UCS both decrease with the increase of CEV addition. When cement-tailing ratio is 1:8 and 6%, 9%, 12% of CEV are added, the 28-days UCS of CPB is less than 1 MPa. Considering the heat storage capacity and cost price of backfill, the recommended proportion scheme of CPB material presents cement-tailing ratio of 1:6 and added 12% CEV, and the most recommended heat storage/release temperature cycle range of CPB with added CEV is from 20 ℃ to 40 ℃. Therefore, this paper can provide theoretical support for the utilization of heat storage backfill in green mines

Research Article
Simultaneously removal of P and B from Si by Sr and Zr co-addition during Al-Si low-temperature solvent refining
Chen Chen, Jingwei Li, Qiuxia Zuo, Boyuan Ban, and  Jian Chen
, Available online 19 April 2022, https://doi.org/10.1007/s12613-022-2504-6
Abstract:

To remove the key impurity elements, P and B from primary Si simultaneously, Sr and Zr co-addition to Al-Si alloy systems during solvent refining has been investigated. With the Sr and Zr co-addition, Sr reacts with Al, Si, P in the melt to form a P-containing Al2Si2Sr phase and Zr reacts with B to form a ZrB2 phase. In the Al-Si-Sr-Zr system, high removal fractions of P and B in the primary Si between 84.8%-98.4% and 90.7%-96.7% respectively are achieved at the same time. The best removal effect is obtained in the sample with the addition of Sr-32000+Zr-3000 ppmw, and the removal fractions of P and B in the purified Si reach 98.4% and 96.1%. Compared with the Sr/Zr single-addition, the removal effects of Sr and Zr co-addition on P and B do not show a significant downward trend, indicating that the nucleation and growth of the B/P-containing impurity phases are mutually independent. Finally, an evolution model is proposed to describe the nucleation and the growth stages of Sr/Zr-containing compound phases, which reveals the interaction between the impurity phases and the primary Si.

Research Article
Eco-friendly physical blowing agent mass loss of bio-based polyurethane rigid foam materials
Haozhen Wang, Lin Lin, and  Yingshu Liu
, Available online 17 April 2022, https://doi.org/10.1007/s12613-022-2502-8
Abstract:

Through systematical experiment design, the physical blowing agent (PBA) mass loss of bio-based polyurethane rigid foam (PURF) in the foaming process was measured and calculated in this study, and different eco-friendly PBA mass loss was measured quantitatively for the first time. The core of the proposed method is to add water to replace the difference, and has a high fault tolerance rate for different foaming forms of foams. The method was proved to be stable and reliable through the standard deviations σ1 and σ2 of R1 (ratio of the PBA mass loss to the materials total mass except the PBA) and R2 (ratio of the PBA mass loss to the PBA mass in the materials total mass) in parallel experiments. It can be used to measure and calculate the actual PBA mass loss in the foaming process of both bio-based and petroleum-based PURF. The results show that the PBA mass loss in PURF with different PBA systems is controlled by its initial mass concentration ω, additionally R2 of the same PBA with different initial mass concentration ω is basically a fixed value. The main way for PBA to dissipate into the air is evaporation/escape along the upper surface of foam. This study further reveals the mechanism of PBA mass loss: the evaporation/escape of PBA along the upper surface of foam is a typical diffusion behavior. Its spread power comes from the PBA within the interface layer of the chemical potential and its chemical potential difference in the outside air. For a certain PURF system, R1 has a linear relationship with its PBA initial mass concentration ω, which can be expressed by the functional relationship Ri=ai ωi, where ai is a variable related to PBA's own attributes.

Research Article
Cobalt-based multicomponent nanoparticles supported on N-doped graphene as advanced cathodic catalyst for zinc-air batteries
Shanjing Liu, Xiaohan Wan, Yue Sun, Shiqi Li, Xingmei Guo, Ming Li, Rui Yin, Qinghong Kong, Jing Kong, and  Junhao Zhang
, Available online 15 April 2022, https://doi.org/10.1007/s12613-022-2498-0
Abstract:

To improve the efficiency of cathodic oxygen reduction reaction (ORR) in zinc-air batteries (ZABs), an adsorption-complexation-calcination method is proposed to generate cobalt-based multicomponent nanoparticles comprising Co, Co3O4 and CoN, as well as numerous N heteroatoms, on graphene nanosheets (Co/Co3O4/CoN/NG). The Co/Co3O4/CoN nanoparticles with the size of less than 50 nm are homogeneously dispersed on N-doped graphene (NG) substrate, which greatly improve the catalytic behaviors for ORR. The results exhibit that the half-wave potential is high to 0.80 V vs. RHE and the limiting current density is 4.60 mA cm-2, which verge on those of commercially available platinum/carbon (Pt/C) catalysts. Investigating as cathodic catalyst for ZABs, the battery shows large specific capacity and open circuit voltage of 843.0 mAh gZn-1 and 1.41 V, respectively. The excellent performance is attributed to the efficient two-dimensional structure with high accessible surface area and the numerous multiple active sites provided by highly scattered Co/Co3O4/CoN particles and doped nitrogen on the carbon matrix.

Research Article
Investigation on microstructure and microhardness of aluminium alloy with underwater and in-air wire-feed laser deposition
Ning Guo, Qi Cheng, Yunlong Fu, Yang Gao, Hao Chen, Shuai Zhang, Xin Zhang, and  Jinlong He
, Available online 15 April 2022, https://doi.org/10.1007/s12613-022-2500-x
Abstract:

This study carried out the underwater and in-air wire-feed laser deposition of an aluminium alloy with a thin-walled tubular structure. For both the underwater and in-air deposition layers, both were well-formed and incomplete fusion, cracks, or other defects did not exist. Compared with the single-track deposition layer in air, the oxidation degree of the underwater single-track deposition layer was slightly higher. In both the underwater and in-air deposition layers, columnar dendrites nucleated close to the fusion line and grew along the direction of the maximum cooling rate in the fusion region (FR), while equiaxed grains formed in the deposited region (DR). As the environment changed from air to water, the width of DR and height of FR decreased, but the deposition angle and height of DR increased. The grain size and ratio of the high-angle boundaries also decreased due to the large cooling rate and low peak temperature in the water environment.However, the existence of a water environment benefitted the reduction of magnesium element burning loss in the DR. The microhardness values of the underwater deposition layer were much larger than those of the in-air layer, owing to the fine grains and high magnesium content.

Research Article
Insight to the enhanced microwave absorption of porous N-doped carbon driven by ZIF-8: Competition between graphitization and porosity
You Zhou, Hongpeng Wang, Dan Wang, Xianfeng Yang, Hongna Xing, Juan Feng, Yan Zong, Xiuhong Zhu, Xinghua Li, and  Xinliang Zheng
, Available online 15 April 2022, https://doi.org/10.1007/s12613-022-2499-z
Abstract:

Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents. Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently required. Herein, utilizing the low boiling point of Zn, porous N-doped carbon was fabricated by carbonization of ZIF-8 (Zn) at different temperature, and the microwave absorption performance was investigated. The porous N-doped carbon inherits the high porosity of ZIF-8 precursor. By increasing the carbonization temperature, the contents of Zn and N elements are decreased; the graphitization degree is improved; however, the specific surface area and porosity are increased first and then decreased. When the carbonization temperature is 1000°C, the porous N-doped carbon behaves enhanced microwave absorption. With an ultrathin thickness of 1.29 mm, the ideal RL reaches -50.57 dB at 17.0 GHz and the effective absorption bandwidth is 4.17 GHz. The mechanism of boosted microwave absorption is ascribed to the competition of graphitization and porosity as well as N dopants, resulting in high dielectric loss capacity and good impedance matching.  The porous structure can prolong the pathways and raise the contact opportunity between microwaves and porous carbon, causing multiple scattering, interface polarization and improved impedance matching. Besides, the N dopants can induce electron polarization and defect polarization. These results give a new insight to construct lightweight carbon-based microwave absorbents by regulating the graphitization and porosity.

Research Article
Toughness enhancement of single-crystal diamond by the homoepitaxial growth of periodic nitrogen-doped nano-multilayers
Yun Zhao, Juping Tu, Liangxian Chen, Junjun Wei, Jinlong Liu, and  Chengming Li
, Available online 15 April 2022, https://doi.org/10.1007/s12613-022-2497-1
Abstract:

Periodic nitrogen-doped homoepitaxial nano-multilayers are grown by microwave plasma chemical vapor deposition. The residual time of gases (such as CH4 and N2) in the chamber is determined by optical emission spectroscopy to determine the nano-multilayer growth process, and thin, nanoscale nitrogen-doped layers are obtained. The highest toughness of 18.2 MPa m1/2 under a Young’s modulus of 1000 GPa is obtained when the single-layer thickness of periodic nitrogen-doped nano-multilayers is about 96 nm. Compared with that of a high-pressure high-temperature seed substrate, the fracture toughness of periodic nitrogen-doped nano-multilayers is greater than twice that of the seed substrate. Alternating tensile and compressive stresses are derived from periodic nitrogen doping; hence, the fracture toughness is significantly improved. Single-crystal diamond with a high toughness demonstrates wide application prospects for high-pressure anvils and single-point diamond cutting tools.

Research Article
In-situ growth of NiCo bimetal anchored on porous straw-derived biochar composites for the boosted microwave absorption properties
Yuanyuan Zhou, Zhongyi Bai, Xiangyang Yang, Wei Liu, Bingbing Fan, Zhikai Yan, and  Xiaoqin Guo
, Available online 15 April 2022, https://doi.org/10.1007/s12613-022-2496-2
Abstract:

As people's protection awareness about electromagnetic pollution is gradually increasing, the demand for absorbing materials with renewability and environmental friendliness has attracted widespread attention. In this paper, the straw-derived biochar combined with NiCo alloys composites were successfully fabricated in the process of high temperature carbonization and subsequent hydrothermal reaction. The electromagnetic parameters of porous biocarbon/NiCo composites can be effectively tuned by the NiCo contents. The porous biocarbon/NiCo composites present the improved absorbing performance due to the synergy effect of magnetic-dielectric characteristics. An exceptional reflection loss (RL) is -27.0 dB at 2.2 mm thickness and an effective absorption bandwidth can reach 4.42 GHz (11.71-16.13 GHz). These results demonstrate that the porous biocarbon/NiCo composite could be used as a new generation absorbing material because of low density, light weight, excellent conductivity, and strong absorption characteristics.

Research Article
Direct reduction swelling behavior of pellets in gas-based shaft furnaces based on typical atmospheres for hydrogen metallurgy
Zichuan Zhao, Jue Tang, Mansheng Chu, Jinge Feng, Feng Li, and  Zhenggen Liu
, Available online 8 April 2022, https://doi.org/10.1007/s12613-022-2494-4
Abstract:

Hydrogen-based shaft furnace process was gaining more and more attention due to its low carbon emission, and the reduction behavior significantly affects its operation. In this work, the effects of reduction degree, temperature, and atmosphere on the swelling behavior had been studied thoroughly under typical hydrogen metallurgy conditions. The results showed that the pellets swelled rapidly in the early reduction stage, then reached a maximum reduction swelling index (RSI) at approximately 40% reduction degree. The crystalline transformation of the iron oxides during the reduction process was the main reason of pellets swelling. The RSI increased significantly with increasing temperature in the range of 850°C-1050°C, the maximum RSI increased from 6.66% to 25.0% in the gas composition of 100% H2. With the temperature increased, the pellets suffered more thermal stress resulting in an increase of the volume. The maximum RSI decreased from 14.77% to 10.92% with the proportion of H2 in the atmosphere increased from 55% to 100% at the temperature of 950°C. The metallic iron tended to precipitate in a lamellar structure rather than whiskers. Consequently, the inside of the pellets became regular, so the RSI decreased. Overall, controlling a reasonable temperature and increasing the H2 proportion was an effective way to decrease the RSI of pellets.

Research Article
Achieving oxidation protection effect for strips hot rolling via Al2O3 nanofluid lubrication
Jianlin Sun, Boyuan Huang, Jiaqi He, Erchao Meng, and  Qianhao Chang
, Available online 7 April 2022, https://doi.org/10.1007/s12613-022-2493-5
Abstract:

It was discovered the application of Al2O3 nanofluid as lubricant for steel hot rolling could synchronously achieve oxidation protection of strips surface. The underlying mechanism was investigated through hot rolling tests and molecular dynamics (MD) simulations. The employment of Al2O3 nanoparticles contributed to significant enhancement in the lubrication performance of lubricant. The rolled strip exhibited the best surface topography that the roughness reached lowest with the sparsest surface defects. Besides, the oxide scale generated on steel surface was also thinner, and the ratio of Fe2O3 among various iron oxides became lower. It was revealed the above oxidation protection effect of Al2O3 nanofluid was attributed to the deposition of nanoparticles on metal surface during hot rolling. A protective layer in the thickness of about 193 nm was formed to prevent the direct contact between steel matrix and atmosphere, which was mainly composed of Al2O3 and sintered organic molecules. MD simulations confirmed the diffusion of O2 and H2O could be blocked by the Al2O3 layer through physical absorption and penetration barrier effect.

Research Article
Separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts with monothio-Cyanex272 and trioctylamine
Junlian Wang, Lu Liu, Wen Xu, Hui Liu, Guodong Xu, Kun Huang, Fengshan Yu, and  Guoyong Huang
, Available online 7 April 2022, https://doi.org/10.1007/s12613-022-2492-6
Abstract:

The objective of this work is to directly separate Pd, Pt and Rh from highly acidic (6~8 mol/L HCl) leach liquor of spent automobile catalysts with commercial extractants monothio-Cyanex 272 and trioctylamine (TOA). The effect of various parameters such as the acidity, extractant concentration, phase ratio A/O and diluents on the Pd and Pt extraction were investigated. The stripping behaviors of Pd and Pt were also studied. We also separated Pd and Pt from highly acidic simulated leach liquor of spent automobile catalysts with monothio-Cyanex 272 and TOA. The results show that monothio-Cyanex 272 shows strong extractability and specific selectivity for Pd, and only one single stage is needed to recover more than 99.9% of Pd, leaving behind all the Pt, Rh and base metals of Fe, Mg, Ce, Ni, Cu and Co in the raffinate. The loaded Pd is efficiently stripped by acidic thiourea solutions. TOA shows strong extractability for Pt and Fe at acidity of 6 mol/L HCl. More than 99.9% of the Pt and all of the Fe are extracted into the organic phase after two stages of countercurrent extraction. Diluted HCl easily scrubs the loaded base metals (Fe, Cu and Co). The loaded Pt is efficiently stripped by 1.0 mol/L thiourea and 0.05~0.1 mol/L NaOH solutions. Monothio-Cyanex 272 and TOA can realize the separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts.

Research Article
Enhanced microwave absorption property of silver decorated biomass ordered porous carbon composite materials with frequency selective surface incorporation
Yi Liu, Jingnan Qin, Linlin Lu, Jie Xu, and  Xiaolei Su
, Available online 3 April 2022, https://doi.org/10.1007/s12613-022-2491-7
Abstract:

Porous carbon (PC) is a promising electromagnetic (EM) wave absorbing material thanks to its light weight, large specific surface area as well as good dissipating capacity. To further improve its microwave absorbing performance, silver coated porous carbon (Ag@PC) is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork. Phase compositions, morphological structure and microwave absorption capability of the Ag@PC has been explored. Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork, which accelerates graphitization process of the amorphous carbon. The Ag@PC composite without adding Polyvinyl Pyrrolidone (PVP) exhibits higher dielectric constant and better EM wave dissipating capability. This is because the larger particles of Ag give rise to higher electric conductivity. After combing with frequency selective surface (FSS), the EM wave absorbing performance is further improved and the frequency region below -10 dB is located in 8.20-11.75 GHz, and the minimal reflection loss value is -22.5 dB. This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.

Research Article
Effects of ZnO, FeO, and Fe2O3 on the spinel formation, microstructure and physicochemical properties of augite-based glass ceramics
Shuai Zhang, Yanling Zhang, and  Shaowen Wu
, Available online 2 April 2022, https://doi.org/10.1007/s12613-022-2489-1
Abstract:

Augite-based glass ceramics were synthesised using ZnO, FeO, and Fe2O3 as additives, and the formation of spinel, matrix structure, crystallisation thermodynamics and physicochemical properties were investigated. The results showed that oxides result in numerous preliminary spinels in the glass matrix. FeO, ZnO and Fe2O3 influence the formation of spinel, while FeO simplifies the glass network. FeO and ZnO promote bulk crystallisation of the parent glass. After adding oxides, the grains of augite phase were refined, and the relative quantities of augite crystal planes were also influenced. All samples displayed good mechanical properties and chemical stability. The 2wt% ZnO-doping sample displayed the maximum flexural strength (170.3 MPa). Chromium leaching amount values of all the samples were less than the national standard (1.5 mg/L), confirming the safety of the materials. In conclusion, an appropriate amount of zinc-containing raw material is beneficial for the preparation of augite-based glass ceramics.

Research Article
Innovative preparation of Co@CuFe2O4 composite via ball-milling assisted chemical precipitation and annealing for glorious electromagnetic-wave absorption
Xing Feng, Pengfei Yin, Limin Zhang, Xiyuan Sun, Jian Wang, Liang Zhao, Changfang Lu, Zhihua Gao, and  Yongxin Zhang
, Available online 31 March 2022, https://doi.org/10.1007/s12613-022-2488-2
Abstract:

To deal with the growing electromagnetic hazards, herein a Co@CuFe2O4 absorbing agent with excellent impedance matching at thin thickness was obtained via innovative route of ball-milling assisted chemical precipitation and annealing. The as-prepared composite possesses excellent interface polarization ability due to sufficient contact between CuFe2O4 NPs and flat Co, and this compressed Co lamella could also provide sufficient eddy current loss. Moreover, the dipole polarization, electron hopping /conduction and structural scattering contribute to its broadband microwave absorption as well. Thus, the minimum microwave reflection loss achieves -35.56 dB at 12.93 GHz for 1.8 mm thickness, and the broadest efficient absorption bandwidth can reach 6.74 GHz for thinner thickness of 1.72 mm. The preparation method reported here can be referenced as a new-type route to manufacture electromagnetic absorbers with outstanding performance.

Research Article
Mineralogical characteristics, metallurgical properties and phase structure evolution of Ca-rich hematite sintering
Lele Niu, Zhengjian Liu, Jianliang Zhang , Dawei Lan, Sida Li, Zhen Li, and  Yaozu Wang
, Available online 29 March 2022, https://doi.org/10.1007/s12613-022-2484-6
Abstract:

The experimental study in this paper was carried out to clarify the mineralogical properties of the newly found calcium-rich iron ore and its behavior in the sintering process. Chemical analysis, laser diffraction, scanning electron microscopy, XRD-Rietveld method,and micro-sintering were used to analyze the mineralogical properties and sintering pot tests were used to study the sintering behavior of calcium-rich iron ore. In addition, a grey correlation mathematical model was used to calculate and compare the comprehensive sintering index under different calcium-rich iron ore ratios. The results and findings demonstrate that the Ca-rich iron ore has coarse grain size and strong self-fusing characteristics with Ca element in the form of calcite (CaCO3) and the liquid phase produced by the self-fusing of calcium-rich iron ore is well crystallized. Its application with a 20% ratio in sintering improves sinter productivity, reduces fuel consumption, enhances reduction index, and improves gas permeability in blast furnace by 0.45 t/(m2·h), 6.11 kg/t, 6.17% and 65.39 kPa·℃ respectively. Ca-rich iron ore sintering can improve the calorific value of sintering flue gas than magnetite sintering, which is conducive to recovering heat for secondary use. As the ratio of Ca-rich iron ore increases, sinter agglomeration shifts from localized liquid-phase bonding to a combination of localized liquid-phase bonding and iron oxide crystal connection. Based on an examination of the greater weight value of productivity with grey relational analysis, Ca-rich iron ore is beneficial for the comprehensive index of sintering in the range of 0-20% ratios. Therefore, it may be used in sintering with magnetite concentrates as the major ore species.

Research Article
Effect of FeO concentration in sinter iron ore on reduction behavior in a hydrogen-enriched blast furnace
Ko-ichiro Ohno, Takayuki Maeda, Kazuya Kunitomo, and  Masashi Hara
, Available online 24 March 2022, https://doi.org/10.1007/s12613-022-2480-x
Abstract:

Japan started the national project "COURSE 50" for CO2 reduction in the 2000s. This project aimed to establish novel technologies to reduce CO2 emissions with partially utilization of hydrogen in blast furnace-based ironmaking by 30% by around 2030 and use it for practical applications by 2050. The idea is that instead of coke, hydrogen is used as the reducing agent, leading to lower fossil fuel consumption in the process. It has been reported that the reduction behavior of hematite, magnetite, calcium ferrite, and slag in the sinter is different, and it is also considerably influenced by the sinter morphology. This study aimed to investigate the reduction behavior of sinters in hydrogen enriched blast furnace with different mineral morphologies in CO-CO2-H2 mixed gas. As an experimental sample, two sinter samples with significantly different hematite and magnetite ratios were prepared to compare their reduction behaviors. The reduction of wustite to iron was carried out at 1000 °C, 900 °C, and 800 °C in a CO-CO2-H2 atmosphere for the mineral morphology-controlled sinter, and the following findings were obtained. The reduction rate of smaller amount of FeO led to faster increase of the reduction rate curve at the initial stage of reduction. Macro-observations of reduced samples showed that the reaction proceeded from the outer periphery of the sample toward the inside, and a reaction interface was observed where reduced iron and wustite coexisted. Micro-observations revealed three layers, namely, wustite single phase in the center zone of the sample, iron single phase in the outer periphery zone of the sample, and iron oxide-derived wustite FeO and iron, or calcium ferrite-derived wustite 'FeO' and iron in the reaction interface zone. A two-interface unreacted core model was successfully applied for the kinetic analysis of the reduction reaction, and obtained temperature dependent expressions of the chemical reaction coefficients from each mineral phases.

Research Article
Construction of BiVO4/BiOCl@C Z-scheme heterojunction for enhanced photoelectrochemical performance
Jiaxin Li, Hao Yuan, Wenjie Zhang, Ruijie Zhu, and  Zhengbo Jiao
, Available online 23 March 2022, https://doi.org/10.1007/s12613-022-2481-9
Abstract:

A Z-scheme heterostructure of Mo, W co-doped BiVO4 (Mo, W: BVO/BiOCl@C) was fabricated by a simple solid solution drying and calcination (SSDC) method. The heterostructure is characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), etc. Under visible light irradiation, Mo, W: BVO/BiOCl@C heterostructure exhibits excellent photoelectrochemical capability compared with other as-prepared samples. The photocurrent density and the incident photon-to-electron conversion efficiency (IPCE) is about 5.4 and 9.0 times higher than that of pure BiVO4, respectively. The enhancement of the photoelectrochemical performance can be attributed to the construct of Z-scheme system, which is deduced from the radical trapping experiments. The Mo, W: BVO/BiOCl@C Z-scheme heterojunction enhances the visible-light absorption and reduces the recombination rate of charge carriers. This work provides an effective strategy to construct Z-scheme photoelectrodes for the application of PEC water splitting.

Research Article
Industrial application prospect and key issues of pure hydrogen reduction process
Lei Wang, Peimin Guo, Lingbing Kong, and  Pei Zhao
, Available online 23 March 2022, https://doi.org/10.1007/s12613-022-2478-4
Abstract:

In order to promote the development of pure hydrogen reduction process, the industrial application prospect and key issues in basic theory and application are discussed by the methods of theoretical analysis and calculation. Through the discussion of thermodynamics and kinetics of pure hydrogen reduction reaction, it can be concluded that the reduction reaction of iron oxide by pure hydrogen is an endothermic reaction, and the reaction rate of hydrogen reduction is significantly faster than that of carbon reduction. To explore the feasibility in the industrial applications of pure hydrogen reduction, hydrogen reduction reactor and process are designed with refer to the industrialized hydrogen-rich reduction process, and the methods of appropriately increasing the reduction temperature, pressure and the temperature of iron ore into the furnace are put forward, which will accelerate the reaction rate and promote the reduction of iron oxide. The key technical parameters in engineering application, such as hydrogen consumption, volume of circulating gas and heat balance, are discussed by theoretical calculation, and the optimized parameter values are proposed. The process parameters, cost, advantages and disadvantages of various current hydrogen production methods are compared, and hydrogen production by natural gas reforming has a good development prospect. Hydrogen production from electrolytic water is a research hotspot at present, but it does not have the conditions for large-scale industrial application and still needs to be further developed. Through the discussion of corrosion mechanism of high temperature and high-pressure hydrogen on heat-resistant steel materials and the corrosion mechanism of H2S in hydrogen on steel, the technical ideas of developing new metal temperature resistant materials, metal coating materials and controlling gas composition are put forward, which provides guidance for the selection of heater and reactor materials. Finally, the key factors affecting smooth operation of hydrogen reduction process in engineering application are analyzed, which provides a reference for the industrial application of pure hydrogen reduction process.

Research Article
Template-free synthesis of core-shell Fe3O4@MoS2@ mesoporous TiO2 magnetic photocatalyst for wastewater treatment
Jingshu Yuan, Yao Zhang, Xiaoyan Zhang, Liang Zhao, Hanlin Shen, and  Shengen Zhang
, Available online 19 March 2022, https://doi.org/10.1007/s12613-022-2473-9
Abstract:

TiO2 is the dominant and most widely researched photocatalyst for environmental remediation, however, the drawbacks such as only responding to UV light (<5% of sunlight), low charge separation efficiency, and difficulties in recycling have severely hindered its practical application. Herein, we synthesized magnetically separable Fe3O4@MoS2@ mesoporous TiO2 (FMmT) photocatalysts via a simple, green, and template-free solvothermal method combined with ultrasonic hydrolysis. It is found that FMmT possesses a high specific surface area (55.09 m2·g–1), enhanced visible-light responsiveness (~521 nm), and remarkable photogenerated charge separation efficiency. In addition, the photocatalytic degradation efficiency of FMmT for methylene blue (MB), rhodamine B (RhB), tetracycline (TC) was 99.4%, 98.5%, and 89.3% within 300 min, respectively. And the corresponding degradation rates are 4.5, 4.3, and 3.1 times higher than pure TiO2 separately. Owing to the high saturation magnetization (43.1 emu·g–1), FMmT can achieve effective recycling with an applied magnetic field. The improved photocatalytic activity is closely related to the effective transport of photogenerated electrons by the active interlayer MoS2 and the electron-hole separation caused by the MoS2@TiO2 heterojunction. Meanwhile, the excellent light-harvesting ability and abundant reactive sites of the mesoporous TiO2 shell further boost the photocatalytic efficiency of FMmT. This work provides a new approach and some experimental basis for the design and performance improvement of magnetic photocatalysts by innovatively incorporating MoS2 as the active interlayer and integrating it with a mesoporous shell.

Research Article
Decarbonisation options of the iron and steel making industry based on a 3-dimensional analysis
Xin Lu, Weijian Tian, Hui Li, Xinjian Li, Kui Quan, and  Hao Bai
, Available online 19 March 2022, https://doi.org/10.1007/s12613-022-2475-7
Abstract:

Decarbonisation is a critical issue to peak CO2 emissions of energy-intensity industries, such as iron and steel making sector. The decarbonisation options of China`s iron and steel making sector were discussed based on a systematic 3-dimensional low-carbon analysis, from aspects of resource utilization (Y), energy utilization (Q), and energy cleanliness (PGEF), on all the related processes, including the current Blast Furnace-Basic Oxygen Furnace integrated process and the specific sub-processes, as well as the Electric Arc Furnace (EAF) process, typical Direct Reduction (DR) process, and Smelting Reduction (SR) process. The study indicates that the 3-dimensional aspects, particularly the energy structure, should be comprehensively considered to quantitatively evaluate the decarbonisation roadmap based on novel technologies or processes. Particularly, promoting the scrap utilization (improvement of Y) and the substitution of the carbon-based energy (improvement of PGEF) is found critical. In terms of process scale, promoting the scrap-based EAF or DR-EAF process development is highly encouraged, owing to their lower PGEF. Emphatically, the 3-dimensional method is expected to extend to other processes or industries, such as cement production and thermal electricity generation industry.

Research Article
Ultralight pyrolytic carbon foam reinforced with amorphous carbon nanotubes for broadband electromagnetic absorption
Luo Kong, Sihan Luo, Shuyu Zhang, Guiqin Zhang, and  Yi Liang
, Available online 19 March 2022, https://doi.org/10.1007/s12613-022-2476-6
Abstract:

For the electromagnetic wave absorbing materials, the extreme value of absorption at a specific frequency is constantly breaking through, but enhancing the absorption properties in the entire band is still a challenge. In this work, a three-dimensional porous pyrolytic carbon (PyC) foam matrix is obtained by template method. Then amorphous carbon nanotubes (CNTs) are in-situ grown on the surface to get ultralight CNTs/PyC foam. The amorphous CNTs are able to distribute uniformly and can be controlled by the catalytic growth time. The interface polarization and conduction loss of the composites can be enhanced by in-situ grown CNTs. When electromagnetic wave enter the internal holes of the material, electromagnetic energy can be completely attenuating under the combined action of polarization, conductivity loss mechanism, and multiple reflections. The density of the ultralight CNTs/PyC foam is merely 22.0 mg·cm-3, and reflection coefficient is lower than -13.3 dB in the whole X-band (8.2~12.4 GHz), which is better than the conventional standard of effective absorption bandwidth (≤-10 dB). The results provide ideas for researching ultralight and strong electromagnetic wave absorbing materials in X-band.

Research Article
Developing new Mg-2RE-0.8Mn-0.6Ca-0.5Zn alloys with high strength and ductility via high-speed extrusion
Jinshu Xie, Zhi Zhang, Shujuan Liu, Jinghuai Zhang, Jun Wang, Yuying He, Liwei Lu, Yunlei Jiao, and  Ruizhi Wu
, Available online 11 March 2022, https://doi.org/10.1007/s12613-022-2472-x
Abstract:

Two new low-alloyed Mg-2RE-0.8Mn-0.6Ca-0.5Zn (wt%, RE=Sm or Y) alloys are developed, which can be produced on an industrial scale via relatively high-speed extrusion. These two alloys are not only comparable to commercial AZ31 alloy in extrudability, but also have superior mechanical properties, especially in terms of yield strength (YS). The excellent extrudability is related to less coarse second-phase particles and high initial melting point of the two as-cast alloys. The high strength-ductility mainly comes from the formation of fine grains, nano-spaced submicron/nano precipitates, and weak texture. Moreover, it is worth noting that the YS of the two alloys can maintain above 160 MPa at elevated temperature of 250°C, significantly higher than that of AZ31 alloy (YS: 45 MPa). The Zn/Ca solute segregation at grain boundaries, the improved heat resistance of matrix due to addition of RE and the high melting points of strengthening particles (Mn, MgZn2, and Mg-Zn-RE/Mg-Zn-RE-Ca) are mainly responsible for the excellent high-temperature strength.

Research Article
Evaluation of VSK separation in the classification of two mineralogically different iron ore fines
Deepak Nayak, Tonmoy Kundu, Nilima Dash, Shiva Kumar I. Angadi, S.K. Chaurasiya, G.E. Sreedhar, T.V.S. Subrahmanyam, and  Swagat S. Rath
, Available online 10 March 2022, https://doi.org/10.1007/s12613-022-2471-y
Abstract:

With gradually diminishing Fe grade in tandem with the ever-increasing demand for high-grade iron ores, iron ore industries are now focusing on the beneficiation of low-grade iron ore fines, mainly considered waste. Besides, the scarcity of water at many of the mines' sites and the new water conservation policies of the governments have necessitated research on suitable dry beneficiation routes. In this context, an effort has been made to evaluate the efficacy of a dry classification unit, such as the VSK separator, in upgrading the iron values of two low-grade Indian iron ore fines, named Sample 1 and Sample 2. The mineralogical studies, involving Scanning Electron Microscopy and X-ray Diffraction, suggest that Sample 1 is a low-grade blue dust sample (51.2 % Fe) containing hematite and quartz as the major minerals, while Sample 2 (53.3% Fe) shows the presence of goethite in addition to hematite and quartz. The experiments, carried out using Box-Benkhen statistical design, indicate that blower speed, followed by feed rate, is the most influencing operating parameter in obtaining a good product in the VSK separator.  At optimum levels of the operating factors, a fines product with~55% Fe at a yield of ~40% can be obtained from Sample 1, while Sample 2 can be upgraded to ~56% Fe at a yield of ~85%. The results suggest that the VSK separator can be employed as an efficient intermediate unit operation in a processing circuit to upgrade the iron contents of iron ore fines.

Research Article
Corrosion resistance and electrical conductivity of V/Ce conversion coating on magnesium alloy AZ31B
Jinxiao Yang, Xudong Wang, Yiren Cai, and  Xiuyu Yang
, Available online 8 March 2022, https://doi.org/10.1007/s12613-022-2463-y
Abstract:

A conversion coating with both corrosion resistance and electrical conductivity on magnesium alloy AZ31B was prepared by V/Ce conversion solution containing transition metal salt and formed compact coating with hemispherical particles. The application of potentiostatic polarization test and electrochemical impedance spectroscopy (EIS) is for the evaluation of the corrosion resistance of coatings. Compared with AZ31B magnesium alloy, the corrosion current density of the conversion coating is decreased by two orders of magnitude. The total impedance of the V/Ce conversion coating rose to 1.6 × 103 Ω·cm2 in contrast with 2.2 × 102 Ω·cm2 of the bare AZ31B. In addition, the electrical conductivity of the coating was assessed by conductivity meter and Mott-Schottky measurement. The results reveal a high dependence of the conductivity of the coating and the semiconducting properties of the coating compositions.

Research Article
The influence of deformation on the corrosion behavior of LZ91 alloy
Xueqin Liu, Xuejian Wang, Enyu Guo, Zongning Chen, Huijun Kang, and  Tongmin Wang
, Available online 8 March 2022, https://doi.org/10.1007/s12613-022-2466-8
Abstract:

The effect of rolling and forging process on the microstructure and corrosion behavior of LZ91 alloy is investigated by means of electron probe micro-analyzer (EPMA), immersion test and electrochemical test. The results show that the area fraction of β-Li phase is unchanged, while the grain size of β-Li phase decreases after forging. The as-rolled LZ91 after forging (FR-LZ91) alloy exhibits the highest area fraction of β-Li phase, and the grains of the alloy are elongated. The corrosion resistance of the as-forged LZ91 alloy is increased due to grain refinement that prevents further corrosion in the immersion test. The FR-LZ91 alloy shows the highest resistance of corrosion film and charge transfer resistance values among the experimental alloys, because of the production of a protective film caused by the high area fraction of the β-Li phase. Keywords: Magnesium lithium alloy; Deformation; Electrochemical test; Corrosion behavior

Research Article
A novel insight on the mechanism of efficient leaching of vanadium from vanadium shale induced by microwave-generated hot spots
Sheng Li, Yimin Zhang, Yizhong Yuan, and  Pengcheng Hu
, Available online 4 March 2022, https://doi.org/10.1007/s12613-022-2459-7
Abstract:

Microwave heating can rapidly and uniformly rise the temperature and accelerate the reaction rate. In this paper, microwave heating was used to improve the acid leaching and the mechanism was investigated via microscopic morphology analysis and numerical simulation by COMSOL Multiphysics software. Effects of microwave power, leaching temperature, CaF2 dosage, H2SO4 concentration and leaching time on vanadium leaching recovery were investigated. A vanadium leaching recovery of 80.66% was obtained at a microwave power of 550 W, leaching temperature of 95°C, CaF2 dosage of 5wt.%, H2SO4 concentration of 20vol% and leaching time of 2.5 h. Compared with conventional leaching technology, vanadium leaching recovery increased by 6.18% and the leaching time shortened by 79.17%. More obvious pulverization of shale particles and delamination of mica minerals happened in the microwave-assisted leaching process. Numerical simulation results show that the temperature of vanadium shales increased with the electric field (E-field) intensity. The distribution of E-field and temperature among vanadium shales particles was relatively uniform, except for the higher content at the contact position of particles. The analysis results of scale-up experiments and leaching experiments indicated high-temperature hot spots in the process of microwave-assisted leaching, and the local high temperature destroyed the mineral structure and accelerated the reaction rate.

Research Article
The microstructure refinement and second phase particle regulation of Mo–Y2O3 alloys by minor TiC additive
Weiqiang Hu, Fengming Gong, Shaocun Liu, Jing Tan, Songhua Chen, Hui Wang, and  Zongqing Ma
, Available online 4 March 2022, https://doi.org/10.1007/s12613-022-2462-z
Abstract:

The oxide dispersion strengthened Mo alloys (ODS-Mo) prepared by traditional ball milling and subsequent sintering technique generally possess comparatively coarse Mo grains and large oxide particles at Mo grain boundaries (GBs), which obviously suppress the corresponding strengthening effect of oxide addition. In this work, the Y2O3 and TiC particles were simultaneously doped into Mo alloys using ball-milling and subsequent low temperature sintering. Accompanied by TiC addition, the Mo-Y2O3 grains are sharply refined from 3.12 μm to 1.36 μm. In particular, Y2O3 and TiC can form smaller Y-Ti-O-C quaternary phase particles (~ 230 nm) at Mo GBs compared to single Y2O3 particles (~ 420 nm), so as to these new formed Y-Ti-O-C particles can more effectively pin and hinder GBs movement. In addition to Y-Ti-O-C particles at GBs, Y2O3, TiOx and TiCx nanoparticles (< 100 nm) also exist within Mo grains, which significantly different from traditional ODS-Mo. The appearance of TiOx phase indicates that some active Ti within TiC can adsorb oxygen impurities of Mo matrix to form new strengthening phase, thus strengthening and purifying Mo matrix. Furthermore, the relative density of pure Mo, Mo-Y2O3 and Mo-Y2O3-TiC alloys possesses similar values (97.4~98.0%). More importantly, the Mo-Y2O3-TiC alloys possess higher hardness (425 HV0.2) compared to Mo-Y2O3 alloys (370 HV0.2). Our work could provide a relevant strategy for the preparation of ultrafine Mo alloys by facile ball-milling.

Research Article
Synergistically coupling of graphene quantum dots with Zn-intercalated MnO2 cathode for high-performance aqueous Zn-ion batteries
Hangtian Zhu, Cong Chen, Minjie Shi, Jintian Jiang, Liping Zhao, and  Chao Yan
, Available online 23 February 2022, https://doi.org/10.1007/s12613-022-2441-4
Abstract:

Cost effective, safe and highly performing energy storage devices require rechargeable batteries and among various options, aqueous zinc-ion batteries (ZIBs) have shown high promise in this regard. As a cathode material for the aqueous ZIBs, manganese dioxide (MnO2) has been found to be promising but certain drawbacks of this cathode material are slow charge-transfer capability and poor cycling performance. Herein, a novel design of graphene quantum dots (GQDs) integrated with Zn-intercalated MnO2 nanosheets is put forward to construct a 3D nanoflower-like GQDs@ZnxMnO2 composite cathode for aqueous ZIBs. The synergistically coupling of GQDs modification with Zn intercalation provides abundant active sites and conductive medium to facilitate the ion/electron transmission, as well as ensure the GQDs@ZnxMnO2 composite cathode with enhanced charge-transfer capability and high electrochemical reversibility, which are elucidated by experiment results and in-situ Raman investigation. These impressive properties endow the GQDs@ZnxMnO2 composite cathode with superior aqueous Zn2+ storage capacity (~403.6 mAh g-1), excellent electrochemical kinetics and good structural stability. For actual applications, the fabricated aqueous ZIBs can deliver a substantial energy density (226.8 Wh kg-1), a remarkable power density (650 W kg-1), and long-term cycle performance, further stimulating their potential application as the efficient electrochemical storage devices for various energy-related fields.

Research Article
Hydrogen-based direct reduction of iron oxide at 700°C: Heterogeneity at pellet- and microstructure-scales
Yan Ma, Isnaldi R. Souza Filho, Xue Zhang, Supriya Nandy, Pere Barriobero-Vila, Guillermo Requena, Dirk Vogel, Michael Rohwerder, Dirk Ponge, Hauke Springer, and  Dierk Raabe
, Available online 17 February 2022, https://doi.org/10.1007/s12613-022-2440-5
Abstract:

Steel production causes a third of all industrial CO2 emissions due to the use of carbon-based substances as reductants for iron ores, making it a key driver of global warming. Therefore, research efforts aim at replacing these reductants by sustainably produced hydrogen. Hydrogen-based direct reduction (HyDR) is an attractive processing technology, as DR furnaces are routinely operated in the steel industry, yet with CH4 or CO as reductants. Hydrogen diffuses much faster through shaft furnace pellet agglomerates than carbon-based reductants, but the net reduction kinetics in the HyDR is still too sluggish for high-quantity steel production and the hydrogen consumption exceeds the stoichiometrically required amount substantially. Thus, the present study focuses on a better understanding of the influence of spatial gradients, morphology, and internal microstructures of ore pellets on reduction efficiency and metallization during HyDR. For this purpose, commercial DR pellets were investigated using synchrotron high-energy X-ray diffraction and electron microscopy in conjunction with electron backscatter diffraction as well as chemical probing. Revealing the interplay of the different phases with internal interfaces, free surfaces, and associated nucleation and growth mechanisms provides the basis for developing tailored ore pellets that are better suited for fast and efficient HyDR.

Research Article
Synthesis of CA6/AlON composite with enhanced slag resistance
Yunsong Liu, Enhui Wang, Linchao Xu, Tao Yang, Zhijun He, Tongxiang Liang, and  Xinmei Hou
, Available online 12 February 2022, https://doi.org/10.1007/s12613-022-2435-2
Abstract:

Aiming to improve the slag resistance of calcium hexaaluminate (CA6), different amounts of AlON has been introduced in CA6 materials using two approaches, i.e. one-step and two-steps methods. One-step method is a direct one to sinter the mixtures combining Al2O3, CaCO3 and Al in flowing nitrogen, in which AlON clusters are always formed owing to the bad wettability of Al by Al2O3, leading to rather high porosity of CA6/AlON composite. In two-steps method, CA6 and AlON are prepared separately, and then mixed and sintered in flowing nitrogen. Compared with the sample prepared by one-step method, both CA6 and AlON in composite by two-steps method are more uniformly distributed, and the optimized amount of AlON addition is determined to be 10 wt%. The slag corrosion and penetration test shows that CA6/AlON composite using two-steps method exhibit superior slag corrosion protection. Based on this, the promoted effects of AlON on the slag penetration and corrosion resistance are also discussed.

Research Article
Comprehensive utilization of complex rubidium ore resources: Mineral dissociation and selective leaching of rubidium and potassium
Quankuang Zhang, Baozhong Ma, Chengyan Wang, Yongqiang Chen, and  Wenjuan Zhang
, Available online 12 February 2022, https://doi.org/10.1007/s12613-022-2436-1
Abstract:

Currently, the process of extracting rubidium from ores has attracted a great deal of attention due to the increasing application of rubidium in high-technology field. A novel process for the comprehensive utilization of rubidium ore resources is proposed in this paper. The process consists mainly of mineral dissociation, selective leaching, and desilication. The results showed that the stable silicon-oxygen tetrahedral structure of the rubidium ore was completely disrupted by thermal activation and the mineral was completely dissociated, which was conducive to subsequent selective leaching. Under the optimal conditions, extractions of 98.67% Rb and 96.23% K were obtained for leaching the rubidium ore. Moreover, the addition of a certain amount of activated Al(OH)3 during leaching can effectively inhibit the leaching of silicon. In the meantime, the leach residue was sodalite, which was successfully synthesized to zeolite A by hydrothermal conversion. The proposed process provided a feasible strategy for the green extraction of rubidium and the sustainable utilization of various resources.

Research Article
Microstructure and toughness of thick-gauge pipeline steel joint via double-sided friction stir welding combined with preheating
Guangming Xie, Ruihai Duan, Yuqian Wang, Zongʼan Luo, and  Guodong Wang
, Available online 9 February 2022, https://doi.org/10.1007/s12613-022-2434-3
Abstract:

Fusion welding easily causes microstructural coarsening in the heat-affected zone (HAZ) of a thick-gauge pipeline steel joint. This is most significant in the inter-critically coarse-grained HAZ (ICCGHAZ), which considerably deteriorates the toughness of the joint. In the present work, 11-mm thick pipeline steel was joined by preheating and double-sided friction stir welding (FSW). A comparative study on the microstructure and toughness in the ICCGHAZs for FSW and gas metal arc welding (GMAW) was performed. The toughness in the ICCGHAZ for FSW was improved significantly than that in the ICCGHAZ for GMAW. Generally, the nugget zone (NZ) has a coarse microstructure in the FSW steel joint formed at the highest peak temperature. However, in the current study, the microstructure in the one-pass NZ was remarkably refined owing to the static recrystallization of ferrite. An excellent toughness was achieved in the NZ of the pipeline steel joint that employed FSW.

Research Article
Combustion performance of pulverized coal and corresponding kinetics study after adding the additives: Fe2O3 and CaO
Qiangjian Gao, Guopeng Zhang, Haiyan Zheng, Xin Jiang, and  Fengman Shen
, Available online 30 January 2022, https://doi.org/10.1007/s12613-022-2432-5
Abstract:

Combustion performance of pulverized coal (PC) in blast furnace (BF) process is regarded as a criteria parameter to assess proper pulverized coal injection dosage. In this paper, effects of two kinds of additives, Fe2O3 and CaO, on PC combustion were studied using the thermo-gravimetric method. The results demonstrate that both the Fe2O3 and CaO can promote combustion performance index of PC including ignition index (Ci), burnout index (Db) as well as comprehensive combustibility index (Sn). The Sn increases from 1.37×10-6 [%2/(min2·°C3)] to 2.16×10-6 [%2/(min2·°C3)] as the Fe2O3 proportions increase from 0wt% to 5.0wt%. Additionally, the combustion kinetics of PC was clarified using the Coats-Redfern method. The results show that the activation energy (E) of PC combustion decreases after adding the above additives. For instance, the E decreases from 56.54 kJ/mol to 35.75 kJ/mol when the Fe2O3 proportions increase from 0wt% to 5.0wt%, which supports the improved combustion performance. Moreover, it is uneconomic to utilize pure Fe2O3 and CaO in production. Based on economy analysis, we selected the iron-bearing dust (IBD) which contains much Fe2O3 and CaO component to investigate, and got the same effects. Therefore, the IBD is potential option for catalytic PC combustion in BF process.

Research Article
Gasification of iron-coke and co-gasification behavior of iron-coke and coke under simulated hydrogen-rich blast furnace condition
Kai Zhu, Zhuming Chen, Shuixin Ye, Shuhua Geng, Yuwen Zhang, and  Xionggang Lu
, Available online 29 January 2022, https://doi.org/10.1007/s12613-022-2429-0
Abstract:

The gasification of iron-coke and the co-gasification behavior of iron-coke and coke in a hydrogen-rich environment were studied. The results indicate that the initial gasification temperature of iron-coke decreased with the increasing content of iron ore powder in the CO2 and H2O(g) atmosphere. In the atmosphere of 40% H2O + 60% CO2, the coke reactivity index (CRI) of iron-coke with the addition of 3% iron ore powder reached 58.7% and its coke strength after reaction (CSR) reached 56.5%. Due to the catalytic action of iron, the reaction capacity of iron-coke was greater than that of coke. As the iron-coke was preferentially gasified, the CRI of the coke was reduced and its CSR was increased when the iron-coke and the coke are co-gasified. The results show that the skeleton action of the coke can be protected by iron-coke.

Research Article
Relationship between elements migration of α-AlFeMnSi phase and micro-galvanic corrosion sensitivity of Al-Zn-Mg alloy
Min Ao, Yucheng Ji, Pan Yi, Ni Li, Li Wang, Kui Xiao, and  Chaofang Dong
, Available online 26 January 2022, https://doi.org/10.1007/s12613-022-2428-1
Abstract:

First principles calculations and scanning Kelvin probe force microscopy (SKPFM) were used to investigate the effect of elements migration of α-AlFeMnSi phase on micro-galvanic corrosion behavior of Al-Zn-Mg alloy. The simulation results showed that the average work function difference between the α-AlFeMnSi phase and Al matrix decreased from 0.232 eV to 0.065 eV due to the synchronous migration of element Fe-Mn-Si. Specifically, as the element Fe-Si migration during the extrusion process, the average Volta potential difference detected by SKPFM between the α-AlFeMnSi phase and Al matrix dropped down to 432.383 mV from 648.370 mV. Thus, the elements migration reduced the micro-galvanic corrosion sensitivity of Al-Zn-Mg alloy. To reach the calculated low micro-galvanic tendency between α-AlFeMnSi phase and Al matrix, the diffusion of Mn should be promoted during extruding process.

Research Article
Fe-based amorphous coating prepared by HVOF and its corrosion behavior in static lead-bismuth eutectic alloy
Xiangyang Peng, Yuhai Tang, Xiangbin Ding, Zhichao Lu, Shuo Hou, Jianming Zhou, Shuyin Han, Zhaoping Lu, Guangyao Lu, and  Yuan Wu
, Available online 18 January 2022, https://doi.org/10.1007/s12613-022-2420-9
Abstract:

To enhance the corrosion resistance of the T91 stainless steel in liquid Lead-Bismuth eutectic (LBE), the Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2 amorphous coating was deposited on T91 steel substrate by the high-velocity oxygen fuel (HVOF) spray technique. And the corrosion behavior of both the T91 steel and coating exposed to oxygen-saturated LBE at 400℃ for 500 h was investigated. It was found that the T91 substrate was severely corroded and covered by homogeneously distributed dual-layer oxide scale forms on the interface contacted to LBE, consisting of outer magnetite layer and inner Fe-Cr spinel layer. While the amorphous coating with a high glass transition temperature (Tg = 550℃) and crystallization temperature (Tx = 600℃) exhibits dramatically enhanced thermal stability and corrosion resistance. No visible LBE penetration was observed although a small amount of Fe3O4, Cr2O3, and PbO were found on the coating surface. Additionally, the amorphicity and interface bonding of the coating layer remained basically unchanged after the LBE corrosion. The results confirm that the Fe-based amorphous coating can act as a stable barrier layer in liquid LBE and have great application potential for long-term service in LBE-cooled fast reactors.

Research Article
Electrochemically triggered decoupled transport behaviors in intercalated graphite: From energy storage to enhanced electromagnetic applications
Ya Chen, Kailun Zhang, Na Li, Wei Guan, Zhiyuan Li, Haosen Chen, Shuqiang Jiao, and  Weili Song
, Available online 12 January 2022, https://doi.org/10.1007/s12613-022-2416-5
Abstract:

Bulk graphitic papers, e.g. pyrolytic graphite (PG) with highly aligned graphene layers, present anisotropic electrical and thermal transport behavior, which is attractive in electronics, electrocatalysts and energy storage. Such pristine PG is meeting the limit of electrical conductivity (~2.5 × 104 S cm-1), although efforts have been made for achieving high-purity sp2 hybridized carbon. For manipulating the electrical conductivity of PG, a facile and efficient electrochemical strategy is demonstrated to enhance electrical transport ability via reversible intercalation/de-intercalation of AlCl— 4 into the graphitic interlayers. With the stage evolution at different voltages, variable electrical and thermal transport behaviors could be achieved via controlling AlCl— 4 concentrations in the PG because of substantial variation in the electronic density of states. Such evolution leads to decoupled electrical and thermal transport (i.e. opposite variation trend) in the in-plane and out-of-plane directions, and the in-plane electrical conductivity of the pristine PG (1.25 ×104 S cm-1) could be massively promoted to 4.09 ×104 S cm-1 (AlCl— 4 intercalated PG), beyond the pristine bulk graphitic papers used for the electrical transport and electromagnetic shielding. The fundamental mechanism of decoupled transport feature and electrochemical strategy here could be extended into other anisotropic conductive bulks for achieving unusual behaviors.

Research Article
Growth kinetics and mechanism of microarc oxidation coating on Ti6Al4V alloy in phosphate/silicate electrolyte
Dajun Zhai, Tao Qiu, Jun Shen, and  Keqin Feng
, Available online 11 January 2022, https://doi.org/10.1007/s12613-022-2413-8
Abstract:

Microarc oxidation (MAO) is an effective surface treatment method for Ti alloys to allow their application in extreme environments. Here, binary electrolytes consisting of different amounts of sodium phosphate and sodium silicate were designed for MAO. The surface morphology, composition, and properties of MAO coatings on Ti6Al4V alloy treated in 0.1 mol/L electrolyte were investigated to reveal the effect of PO43- and SiO42- on the growth kinetics of the MAO coatings, using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and potentiodynamic polarization. The results showed that PO43- is beneficial for generating microarcs and forming pores within the coating, resulting in a thick but porous coating. SiO42- facilitates the blocking of pores in the outer deposition layer and impedes the generation of microarcs, resulting in a thin dense coating. The thickness, density, phases content, and polarization resistance of the MAO coatings are primarily affected by the intensity of microarcs for low SiO42- contents, and the number of microarcs when the SiO42- content is sufficiently high. The thickness of MAO coatings obtained in P/Si electrolytes shows a piecewise linear increase with increasing process time during the three stages of microarc discharge. SiO42- is beneficial to the density increase of the coating formed in the previous stage of microarcs discharge, but slow down the growth of the coating formed in the next stage.

Research Article
Microstructure and properties evolution of in-situ fibre-reinforced Ag-Cu-Ni-Ce alloy during deformation and heat treatment
Xingqun He, Huadong Fu, and  Jianxin Xie
, Available online 7 January 2022, https://doi.org/10.1007/s12613-022-2412-9
Abstract:

Silver-based alloys are significant light-load electrical contact materials (ECMs). The trade-off between mechanical properties and electrical conductivity is always an important issue for the development of silver-based ECMs. In this paper, we proposed an idea for the regulation of the mechanical properties and the electrical conductivity of Ag-11.40Cu-0.66Ni-0.05Ce (wt%) alloy using in-situ composite fibre-reinforcement. The alloy was processed using rolling, heat treatment and heavy drawing, the strength and electrical conductivity were tested at different deformation stages, and the microstructures during deformation were observed using Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM) and Electron Backscatter Diffraction (EBSD). The results show that the method proposed in this paper can achieve the preparation of in-situ composite fibre-reinforced Ag-Cu-Ni-Ce alloys. After the heavy deformation drawing, the room temperature Vickers hardness of the as-cast alloy increased from 81.6 HV to 169.3 HV, and the electrical conductivity improved from 74.3 %IACS to 78.6 %IACS. As the deformation increases, the alloy strength displays two different strengthening mechanisms, and the electrical conductivity has three stages of change. This research provides a new idea for the comprehensive performance control of high-performance silver-based ECMs.

Research Article
Predicting alloying element yield in a ladle furnace using PCA-DNN model
Zicheng Xin, Jiangshan Zhang, Yu Jin, Jin Zheng, and  Qing Liu
, Available online 31 December 2021, https://doi.org/10.1007/s12613-021-2409-9
Abstract:

The composition control of molten steel is one of the main functions in LF refining process. In this study, a feasible model was established to predict the alloying element yield using principal component analysis (PCA) and deep neural network (DNN). The PCA was used to eliminate collinearity and reduce the dimension of the input variables, and then the data processed by PCA were used to establish the DNN model. The prediction hit ratio for the Si element yield in the error ranges of [-1, 1], [-3, 3], and [-5, 5] were 54.0%, 93.8%, and 98.8%, respectively, while, those of Mn element yield in the error ranges of [-1, 1], [-2, 2], and [-3, 3] were 77.0%, 96.3%, and 99.5%, respectively, in the PCA-DNN model. The results demonstrated that the PCA-DNN model performed better than the known models, such as the reference heat method, the multiple linear regression (MLR), the modified back propagation (BP), and DNN model. Meanwhile, the accurate prediction of alloying element yield can greatly contribute to realize a “narrow window” control of composition in molten steel. The construction of prediction model for element yield can also provide a reference for the development of alloying control model in LF intelligent refining in the modern iron and steel industry.

Research Article
Microstructure and texture evolution of the non-oriented silicon steel during punching
Xiang Fang, Wei Wang, François Brisset, Anne-Laure Helbert, and  Thierry Baudin
, Available online 28 December 2021, https://doi.org/10.1007/s12613-021-2404-1
Abstract:

The iron core of motors is mainly manufactured using a punching process from rolled non-oriented silicon steel, and this leads to deformation and texture evolution at cutting edge. According to this, circular samples of a non-oriented silicon steel were prepared by punching with blunt punch tools. In this work, two positions along the RD and TD directions at the cutting edge were analyzed. The main mechanisms of deformation for both positions are dislocation slip and formation of shear bands. These two mechanisms lead to similar texture evolutions for both positions. The dislocation slip leads to the formation of the {221}〈uvw〉 component in the unbending area (200 µm away from cutting edge) and in the intermediate continuum bent area. In addition, the evolution of the texture from the {111} γ fiber to the {110} fiber was observed at the extremity of the cutting edge with formation of shear bands.

Research Article
Effects of process parameters on the growth behavior and granule size distribution of iron ore mixtures in a novel high-shear granulator
Yang You, Jiabao Guo, Gang Li, Zhuang Zheng, Yong Li, and  Xuewei Lv
, Available online 28 December 2021, https://doi.org/10.1007/s12613-021-2407-y
Abstract:

This work proposes a novel horizontal high-shear granulator for iron ore granulation before sintering process. The granulation behavior such as growth process and structure of granules were firstly analyzed, followed by the effects of operation conditions such as water content, initial particle size distribution and the concentrate ratio. The results show that the granule size increased significantly with increasing the granulation time, and the structure of granule can be divided into three types: non-nuclei, single-nuclei and multi-nuclei. Water promotes the coalescence and growth of particles, and a better granulation performance was obtained at the water content of 8.8wt% under the current raw material conditions. Increasing the nuclei particle ratio led to an increase in average size of granules and permeability of the granules bed, but a decrease in growth index. Besides, with increasing of concentrate ratio, granulation performance such as granule size, bed permeability and uniformity became worse.

Research Article
Rheological and physicomechanical properties of rod milling sand-based cemented paste backfill modified by sulfonated naphthalene formaldehyde condensate
Qinli Zhang, Hao Wu, Yan Feng, Daolin Wang, Huaibin Su, and  Xiaoshuang Li
, Available online 25 December 2021, https://doi.org/10.1007/s12613-021-2397-9
Abstract:

Rod milling sand (RMS) – a coarse sand aggregate – was recycled for cemented paste backfill (CPB) for the underground mined area at the Jinchuan nickel deposit, named rod milling sand-based cemented paste backfill (RCPB). The adverse effects of coarse particles on the transportation of CPB slurry through pipelines to underground stopes resulting in weakening of the stability of the backfill system are well known. Therefore, sulfonated naphthalene formaldehyde condensate (SNF) was used in this study for the performance improvement of RCPB. The synergistic effect of solid content, lime-sand ratio, and SNF dosage on the workability and strength properties, including slump, yield stress, bleeding rate, uniaxial compressive strength (UCS), as well as mechanism analysis of RCPB, have been explored. The results indicate that the effect of SNF on RCPB performance is related to the SNF dosage, lime-sand ratio, and solid content. The slump of fresh RCPB with 0.1wt%–0.5wt% SNF increased by 2.6%–26.2%, whereas the yield stress reduced by 4.1%–50.3%, indicating better workability and improved cohesiveness of the mix. The bleeding rate of fresh RCPB decreased first and then rose with the increase of SNF dosage, and the peak decrease was 67.67%. UCS of RCPB first increased and then decreased with the increase of SNF dosage. At the optimal SNF addition ratio of 0.3wt%, the UCS of RCPB curing for 7, 14 and, 28 days ages increased by 31.5%, 28.4%, and 29.5%, respectively. The beneficial effects of SNF in enhancing the early strength of RCPB have been corroborated. However, the later strength increases at a slower rate. The research findings of this study may guide the design and preparation of RCPB with adequate performance for practical applications.

Research Article
Flocculated unclassified tailings settling efficiency improvement by particle collision optimization in the feedwell
Huazhe Jiao, Weilin Chen, Aixiang Wu, Yang Yu, Zhuen Ruan, Rick Honaker, Xinming Chen, and  Jianxin Yu
, Available online 25 December 2021, https://doi.org/10.1007/s12613-021-2402-3
Abstract:

Efficient thickening of tailings is a prerequisite for the metal mine tailings backfill and surface disposal operation. The effective collision of ultrafine tailings particles in suspension with flocculant molecules is essential for flocs aggregates formation and settling. Unreasonable feeding speed and flocculant adding method will lead to the failure of effective dispersion of flocculant and high particle content in thickener overflow. In this work, the effects of turbulence intensity and flocculant adding method on floc size, strength and movement characteristics are analysed. Aiming to solve the turbidity increased problem, a pilot-scale continuous thickening test was carried out. Taking a single particle and multiple flocs of full tailings as the research object, the particle iterative settlement model and the Diffusion Limited Aggregation (DLA) model of flocs were established respectively. The influence of turbulence intensity on collision effect is studied by tracking and simulating particle trajectory. The results show that in the process of single particle settlement, chaos appears in the iterative process owing to particle adhesion which caused by micro action. When the turbulence intensity is 25.99%, the maximum particle size of tailings floc is 6.21mm and the maximum sedimentation rate is 5.284 cm/s. The tailings floc presents a multi-scale structure of particle-force chain system when hindered settling, and the interweaving of strong and weak force chains constitutes the topological structure of particles. The results were applied to a thicker in plant, the flocculant addition mode and feed rate were optimized, and the flocs settling speed and overflow clarity were improved.

Research Article
Premature failure induced by non-equilibrium grain-boundary tantalum segregation in air-plasma sprayed ZrO2-YO1.5-TaO2.5 thermal barrier coatings
Yao Yao, Di Wu, Xiaofeng Zhao, and  Fan Yang
, Available online 9 December 2021, https://doi.org/10.1007/s12613-021-2394-z
Abstract:

ZrO2-YO1.5-TaO2.5 (ZYTO) is a promising top coat material for thermal barrier coatings (TBCs). The bulk properties of ZYTO have been reported by several studies, but its performances as TBCs are less-well understood. Here we prepare ZYTO TBCs by air plasma spraying (APS) and investigate their thermal cycling performances at 1150 ºC. Despite of the good bulk properties, APS ZYTO TBCs present an extremely short thermal fatigue life. This is attributed to the non-equilibrium grain-boundary segregation of TaO2.5 induced by limited solubility and rapid quenching during APS process, resulting in a tetragonal (t) to cubic (c) and metastable-tetragonal (tm) phase transformation in ZYTO TBCs. The volume shrinkage (~0.74%) associated with the phase transformation generates many cracks at the c/tm phase boundaries after deposition. On the other hand, formation of cubic phase with massive grain-boundary Ta segregation induces a large intergranular embrittlement and a weak bonding strength (~5.3 MPa), resulting in the premature failure of the ZYTO TBCs.

Research Article
Tension-compression asymmetry and corresponding deformation mechanism in ZA21 magnesium bars with bimodal structure
Yujiao Wang, Yun Zhang, and  Haitao Jiang
, Available online 3 December 2021, https://doi.org/10.1007/s12613-021-2388-x
Abstract:

We investigated the asymmetric tension-compression (T-C) behavior of ZA21 bars with bimodal and uniform structures through axial tension and compression tests. The results show that the yield strengths of bars having bimodal structure are 206.42 and 140.28 MPa under tension and compression, respectively, which are higher than that of bars having uniform structure, that is, tensile and compressive yield strength of 183.71 and 102.86 MPa, respectively. Prismatic slip and extension twinning under tension and basal slip and extension twinning under compression dominate the yield behavior and induce the T-C asymmetry. However, due to the basal slip activated in fine grains under tension and the inhibition of extension twinning by fine grains under compression, the bimodal structure possesses a lower T-C asymmetry (0.68) compared to the uniform structure (0.56). Multiple extension twins occur during deformation, and the selection of twin variants depends on the Schmid factor of the six variants activated by parent grains. Furthermore, the strengthening effect of the bimodal structure depends on the grain size and the ratio of coarse and fine grains.

Research Article
Effect of N2 partial pressure on comprehensive properties of antibacterial TiN/Cu nanocomposite coating
Hui Liu, Yanhui Zhao, Chuanshi Sui, Yi Li, Muhammad Ali Siddiqui, Susu Li, Tong Li, Shuyuan Zhang, Hai Wang, Tao Jin, Ling Ren, Ke Yang, and  Ning Zhang
, Available online 26 November 2021, https://doi.org/10.1007/s12613-021-2387-y
Abstract:

Foreign body reactions to the wear debris and corrosion products from the implants, and bacterial infections are the main factors leading to the implant failures. In order to resolve these problems, the antibacterial TiN/Cu nanocomposite coatings with various N2 partial pressures were deposited on 304 stainless steels using an arc ion plating (AIP) system, named TiN/Cu-xPa (x=0.5, 1.0, 1.5). The results of X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy showed that the N2 partial pressures determined the Cu contents, surface defects, and crystallite sizes of TiN/Cu nanocomposite coatings, which further influenced the comprehensive abilities. And the hardness and wear resistances of TiN/Cu coatings were enhanced with increase of the crystallite sizes. Under the co-actions of surface defects, crystallite sizes and Cu content, TiN/Cu-1.0Pa and TiN/Cu-1.5Pa coatings possessed excellent corrosion resistance. Besides, the biological tests proved that all the TiN/Cu coatings showed no cytotoxicity with strong antibacterial ability. Among them, TiN/Cu-1.5Pa coating significantly promoted the cell proliferation, which is expected to be a novel antibacterial, corrosion-resistant and wear-resistant coating on the surfaces of medical implants.

Research Article
Phosphorus reduction behavior of high phosphate iron ore during hydrogen-rich sintering
Yanbiao Chen, Wenguo Liu, and  Haibin Zuo
, Available online 25 November 2021, https://doi.org/10.1007/s12613-021-2385-0
Abstract:

High-phosphorus iron ore resource is recognized as refractory iron ore because of its high phosphorus content and complex ore phase structure. Therefore, it is of great theoretical and practical significance to develop innovative technology to realize the efficient utilization of high-phosphorus iron ore resources. According to this, a method of phosphorus gasification removal in hydrogen-rich sintering process was proposed. In this paper, the reduction mechanism of phosphorus in hydrogen-rich sintering was studied, as well as the reduction kinetics of apatite based on the non-isothermal kinetic method. The results show that improving the reduction time from 20min to 60min, the dephosphorization rate increases from 10.93% to 29.51%. Companied with the reduction of apatite, the metal iron accumulates, part of the reduced phosphorus gas is absorbed by metal iron to form stable iron-phosphorus compounds, resulting in a great reduction of dephosphorization rate. The reduction of apatite is mainly concentrated in the sinter zone and burning zone, and the reduced phosphorus gas moves downward along with flue gas under suction pressure and is condensed and adsorbed partly by the sintering bed when passing through the drying zone and green mix zoon, as a result, the dephosphorization rate is greatly reduced. Based on the Ozawa formula of iso-conversion rate, the reduction activation energy of apatite is 80.42 kJ/mol. The mechanism function of apatite reduction is determined by differential method (Freeman-Carroll method) and integral method (Coats-Redfern method). The differential form of the equation is f(a)= 2(1-a)1/2, and the integral form is G(a)= 1-(1-a)1/2.

Research Article
Efficiency enhancement of Cs0.1(CH3NH3)0.9PbI3 perovskite solar cell by surface passivation using iso-butyl ammonium iodide
Wakul Bumrugsan, Kritsada Hongsith, Vasan Yarangsi, Pisith Kumnorkeaw, Sukrit Sucharitakul, Surachet Phaduangdhitidhada, and  Supab Choopun
, Available online 19 November 2021, https://doi.org/10.1007/s12613-021-2382-3
Abstract:

Efficiency enhancement of Cs0.1(CH3NH3)0.9PbI3 solar cell devices was performed by using iso-butyl ammonium iodide (IBA) passivated on Cs0.1(CH3NH3)0.9PbI3 films. The n-i-p structure of perovskite solar cell devices was fabricated with the structure of FTO/SnO2/Cs0.1(CH3NH3)0.9PbI3 and IBA/Spiro-OMeTAD/Ag. The effect of different weights of IBA passivated on Cs-doped PSCs was systematically investigated and compared with non-passivated devices. It was found that the 5mg IBA-passivated devices exhibited a high PCE of 15.4% higher than 12.6% of non-IBA-passivated devices. The improvement of photovoltaic parameters of the 5 mg IBA-passivated devices can be clearly observed compared to the Cs-doped device. The better performance of the IBA-passivated device can be confirmed by the reduction of PbI2  phase in the crystal structure, lower charge recombination rate, lower charge transfer resistance, and improved contact angle of perovskite films. Therefore, IBA passivation on Cs0.1(CH3NH3)0.9PbI3 is a promising technique to improve the efficiency of Cs-doped perovskite solar cells.

Research Article
Comparative study on the atmospheric corrosion behavior of Nb- and Sb-added weathering steels exposed to the South China Sea
Wei Wu, Lili Zhu, Peilin Chai, Niyun Liu, Longfei Song, Zhiyong Liu, and  Xiaogang Li
, Available online 19 November 2021, https://doi.org/10.1007/s12613-021-2383-2
Abstract:

The atmospheric corrosion behavior of new-type weathering steels (WSs) was comparatively studied, and the effects of Nb and Sb during corrosion were clarified in detail through field exposure and characterization. The results showed that the addition of Nb and Sb played positive roles in corrosion resistance, but there was a clear difference between these two elements. Nb addition slightly improved the rust property of conventional WS but could not inhibit the electrochemical process. In contrast, Sb addition significantly improved the corrosion resistance from the aspects of electrochemistry and rust layer. Specifically, 0.05% Sb optimized the rust structure, accelerated the formation of a high proportion of dense and protective α-FeOOH, repelled the invasion of Cl-, and retarded localized acidification at the bottom of the pit.

Research Article
Effect of titanium content on the refinement of coarse columnar austenite grains during solidification of peritectic steel
Jiazhi An, Zhaozhen Cai, and  Miaoyong Zhu
, Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2375-2
Abstract:

The effect of titanium content on the refinement of austenite grain size in as-cast peritectic carbon steel was investigated by fast directional solidification experiments that simulate the solidification and growth of surface and subsurface austenite in continuously cast slabs. Transmission electron microscope(TEM) and scanning electron microscope(SEM) were used to analyze the size and distribution of Ti(C, N) precipitates during solidification. Based on these results, the pinning pressure of Ti(C, N) precipitates on the growth of coarse columnar grains (CCGs) was studied. The results show that the austenite microstructure of as-cast peritectic carbon steel is mainly composed of regions of CCGs and fine columnar grains (FCGs). Increasing the content of titanium reduces the region and the short axis of the CCGs. When the content of titanium is 0.09 wt%, there is no CCG region. Dispersed microscale particles will firstly form in the liquid, which will decrease the transition temperature from FCGs to CCGs. The chain-like nanoscale Ti(C, N) will precipitate with the decrease of the transition temperature. Furthermore, calculations shows that the refinement of the CCGs is caused by the pinning effect of Ti(C, N) precipitates.

Research Article
Phase equilibria studies of the titanomagnetite and ilmenite smelting slags
Jinfa Liao and  Baojun Zhao
, Available online 9 November 2021, https://doi.org/10.1007/s12613-021-2376-1
Abstract:

Phase equilibrium information of the slag plays an important role in pyrometallurgical processes to obtain optimum fluxing conditions and operating temperatures. Smelting reduction of titanomagnetite and ilmenite ores in iron blast furnace can form Ti(CN) particles causing increased viscosities of slag and hot-metal. HIsmelt has been developed in recent years for ironmaking which does not need coke and sinter. Formation of Ti(CN) in the HIsmelt process is avoided because the oxygen partial pressure in the process is higher than that in the blast furnace. Smelting of TiO2-containing ores in HIsmelt process results in Al2O3–MgO–SiO2–CaO–TiO2 slag. Phase equilibria in this slag system have been investigated using equilibration, quenching and electron probe microanalysis (EPMA) technique. The experimental results are presented in two pseudo-binary sections, which represent the process of HIsmelt to treat 100% titanomagnetite ore and 100% titanomagnetite + 50% ilmenite respectively. The primary phases observed in the composition range investigated include pseudo-brookite M3O5 (MgO·2TiO2–Al2O3·TiO2), spinel (MgO·Al2O3), perovskite CaTiO3 and rutile TiO2. The results show that the liquidus temperatures decrease in the TiO2 and M3O5 primary phase fields with increasing CaO concentration and increase in the spinel and CaTiO3 primary phase fields with increasing CaO concentration. Calculation of solid-phase fractions from the experimental data has been demonstrated. Effect of the basicity on liquidus temperatures of the slag has been discussed. It seems that smelting of titanomagnetite plus ilmenite ores has significant advantages to obtain low-sulphur hot-metal and high-TiO2 slag. Experimentally determined liquidus temperatures are compared with the FactSage predictions to evaluate the existing thermodynamic databases.

Research Article
Effects of microstructure characteristics on the tensile properties and fracture toughness of TA15 alloy fabricated by hot isostatic pressing
Langping Zhu, Yu Pan, Yanjun Liu, Zhiyu Sun, Xiangning Wang, Hai Nan, Muhammad Arif Mughal, and  Xin Lu
, Available online 4 November 2021, https://doi.org/10.1007/s12613-021-2371-6
Abstract:

Powder hot isostatic pressing (HIP) is an effective method to achieve near-net-shape manufacturing of high-quality complex thin-walled titanium alloy parts, and it has received extensive attention in recent years. However, there are few reports about the microstructure characteristics on the strengthening and toughening mechanisms of powder HIPed titanium alloys. Therefore, TA15 powder was prepared into alloy by HIP approach, which are used to explore the microstructure characteristics at different HIP temperatures, and the corresponding tensile properties and fracture toughness. Results show that the fabricated alloy has a "basket-like structure" when the HIP temperature below 950°C, consisting of lath clusters and surrounding small equiaxed grains belts. When the HIP temperature is higher than 950°C, the microstructure gradually transformed into the Widmanstatten structure, accompanied by a significant increase in grain size. The tensile strength and elongation are reduced from 948 MPa and 17.3% for the 910°C specimen to 861 MPa and 10% for the 970°C specimen. The corresponding tensile fracture mode changed from transcrystalline plastic fracture to mixed fracture including intercrystalline cleavage. The fracture toughness of the specimens increased from 82.64 MPa√m for the 910°C specimen to 140.18 MPa√m for the 970°C specimen. Specimens below 950°C tend to form holes due to the prior particle boundaries (PPBs), which is not conducive to toughening. Specimens above 950°C have high fracture toughness due to the crack deflection, crack branching and shear plastic deformation of the Widmanstatten structure. This study provides a valid reference for the development of powder HIPed titanium alloy.

Research Article
Bullet-like vanadium-based MOFs as a highly active catalyst for promoting the hydrogen storage property in MgH2
Zhiyu Lu, Jiahuan He, Mengchen Song, Yan Zhang, Fuying Wu, Jiaguang Zheng, Liuting Zhang, and  Lixin Chen
, Available online 4 November 2021, https://doi.org/10.1007/s12613-021-2372-5
Abstract:

The practical application of magnesium hydride (MgH2) was seriously limited by its high desorption temperature and slow desorption kinetics. In this study, a bullet-like catalyst based on vanadium related MOFs (MOFs-V) was successfully synthesized and doped with MgH2 by ball milling to improve its hydrogen storage performance. Microstructure analysis demonstrated that the as-synthesized MOFs was consisted of V2O3 with a bullet-like structure. After adding 7wt% MOFs-V, the initial desorption temperature of MgH2 was reduced from 340.0°C to 190.6°C. Besides, the MgH2+7wt% MOFs-V composite released 6.4wt% H2 within 5 min at 300°C. Hydrogen uptake was started at 60°C under 32 bar hydrogen pressure for the 7wt% MOFs-V containing sample. The desorption and absorption apparent activity energy of the MgH2+7wt% MOFs-V composite was calculated to be 99.6±12.6 kJ mol-1 and 32.8±3.9 kJ mol-1, much lower than154.5±16.3 kJ mol-1 and 81.1±2.4 kJ mol-1 for the as-prepared MgH2. The MgH2+7wt% MOFs-V composite exhibited superior cyclic property. During the 20 cycles isothermal dehydrogenation and hydrogenation experiments, the hydrogen storage capacity stayed almost unchanged. X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS) measurements confirmed the presence of metallic vanadium in the MgH2+ 7wt% MOFs-V composite, which served as catalytic unit to markedly improve the hydrogen storage properties of Mg/MgH2 system.

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:

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:

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
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:

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
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:

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.

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:

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:

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:

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.

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:

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:

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:

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
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:

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
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:

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:

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:

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.

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:

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 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:

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.

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:

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
Characterization and ultraviolet–visible shielding property of samarium–cerium 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:
Since ultraviolet (UV) light, as well as blue light, which is part of visible light, is 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. The minimum values of average transmittance (360–450 nm) and band gap of samarium–cerium compounds were 8.90% and 2.76 eV, respectively, which were less than 13.96% and 3.01 eV of CeO2. Elemental analysis (EA), X-ray diffraction (XRD), Fourier transformation infrared (FTIR), and Raman spectra determined that the samples contained Ce4O7, Sm2O2S, Sm2O3, and Sm2O2SO4. The microstructure of samples was analyzed by scanning and transmission electron microscopies (SEM and TEM). X-ray photoelectron spectrum (XPS) showed that cerium had Ce3+ and Ce4+ valence states, and oxygen was divided into lattice oxygen and oxygen vacancy, which was the direct cause of the decrease of average transmittance and band gap.
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:

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
Recovery of titanium, aluminum, magnesium and separate silicon from titanium-bearing blast furnace slag by sulfuric acid curing–leaching
Long Wang, Liang Chen, Weizao Liu, Guoquan Zhang, Shengwei Tang, Hairong Yue, Bin Liang, and  Dongmei Luo
, Available online 20 April 2021, https://doi.org/10.1007/s12613-021-2293-3
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 low temperature sulfuric acid curing 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
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:

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.

Erratum
Erratum to: Surface nanobubbles on the hydrophobic surface and their implication to flotation
Chenwei Li, Danlong Li, Xin Li, Ming Xu, and  Haijun Zhang
, Available online 23 June 2022, https://doi.org/10.1007/s12613-022-2521-5
Abstract:
Review
Recent advances of nanoconfinement in Mg related hydrogen storage materials: A minor review
Jingjing Zhang, Bing Zhang, Xiubo Xie, Cui Ni, Chuanxin Hou, Xueqin Sun, Xiaoyang Yang, Yuping Zhang, Hideo Kimura, and  Wei Du
, Available online 17 June 2022, https://doi.org/10.1007/s12613-022-2519-z
Abstract:

Hydrogen is regarded as an ideal clean energy because of its high calorific value and easy accessibility characteristics. However, storing hydrogen in a compact, inexpensive, and safe way is a main restriction for booming the hydrogen energy. Magnesium-based hydrogen storage material is considered as a promising solid hydrogen storage material with the advantages of large hydrogen storage capacity (7.6wt%), good performance and low cost. However, it is still needed to overcome the obstacles of high thermodynamic stability and slow kinetic. In this paper, we review the recent advances of nanoconfinement in Mg related hydrogen storage materials by loading Mg particles to different supporting materials, including carbons, metal-organic frameworks and other materials. Perspectives are also provided for designing high performances of Mg materials using nanoconfinement.

Invited Review
A review of intelligent ore sorting technology and equipment development
Xianping Luo, Kunzhong He, Yan Zhang, Pengyu He, and  Yongbing Zhang
, Available online 23 March 2022, https://doi.org/10.1007/s12613-022-2477-5
Abstract:

Under the background of increasingly scarce ore worldwide and increasingly fierce market competition, developing the mining industry should be strongly restricted. Intelligent sorting equipment can not only improve ore use and improve the economic benefits of enterprises but also increase the ore grade and lessen the grinding cost and tailings production. However, long-term research on intelligent sorting equipment found that the causes affecting sorting efficiency mainly include ore information identification technology, equipment sorting actuator, and information processing algorithm. The accuracy and high speed of these causes is the guarantee for separation efficiency of intelligent ore sorting equipment. In recent years, some achievements have been made in developing intelligent sorting equipment. On the basis of the different characteristic information about minerals, some sorters to ensure the accuracy of equipment sorting and improve the efficiency of sorting have been developed. These sorters include color sorter, X-ray transmission sorter, dual-energy X-ray transmission sorter, X-ray fluorescence sorter, and near-infrared sorter. With the continuous advancement of mining automation, online element rapid analysis technology will become the unavoidable trend of developing intelligent sorting equipment. Laser induced breakdown spectroscopy, transient γ neutron activation analysis, online Fourier transform infrared spectroscopy, and nuclear magnetic resonance techniques will make further progress in the development of ore sorting equipment. Improving information processing algorithms, such as the peak area, principal component analysis, artificial neural network, partial least squares, and Monte Carlo library least squares methods, will also bring intelligent sorting equipment to a new level. With the continuous application of more efficient, convenient, and precise technical methods, the development of intelligent sorters will further promote the reform of the mining industry.

Invited Review
Hematite reduction by hydrogen plasma: Where are we now?
Kali Charan Sabat
, Available online 8 March 2022, https://doi.org/10.1007/s12613-022-2467-7
Abstract:

Currently, iron is extracted from ores such as hematite by carbothermic reduction. The extraction process includes several unit steps/processes that require large-scale equipments and significant financial investments. Additionally, the extraction process produces substantial amount of toxic carbon dioxide (CO2). Alternative to carbothermic reduction is the reduction by hydrogen plasma (HP). HP mainly composed of excited species that facilitate the hematite reduction by providing the thermodynamic and kinetic advantages, even at low temperatures. In addition to these advantages, hematite reduction by HP produces water, which is environmentally beneficial. This report reviews the theory and practice of hematite reduction by HP. Also, the present state of the art in solid-state and liquid-state hematite reduction by HP has been examined. The in-flight hematite reduction by HP has been identified as a potentially promising alternative to the carbothermic reduction. However, the in-flight reduction is still plagued with problems such as excessively high temperatures in thermal HP and considerable vacuum costs in non-thermal HP. These problems can be overcome by using non-thermal atmospheric HP that deviates significantly from local thermodynamic equilibrium.

Invited Review
Review on coal-based reduction and magnetic separation for refractory iron-bearing resources
Qiang Zhang, Yongsheng Sun, Yuexin Han, Yanjun Li, and  Peng Gao
, Available online 30 December 2021, https://doi.org/10.1007/s12613-021-2408-x
Abstract:

The application of coal-based reduction in the efficient iron recovery from refractory iron-bearing resources is comprehensively reviewed. Currently, the development and beneficiation of refractory iron-bearing resources has attracted increasing attention. However, the effect of iron recovery by traditional beneficiation methods is unacceptable. The coal-based reduction and magnetic separation is proposed, which adopts coal as the reductant to reduce the iron oxides to metallic iron below the melting temperature. The metallic iron particles aggregate and grow, and the particle size continuously increases to be suitable for magnetic separation. The optimization and application of coal-based reduction have been abundantly researched. A detailed literature study on coal-based reduction is performed from the perspectives of thermodynamics, reduction kinetics, growth of metallic iron particles, additives, and application. The coal-based reduction industrial equipment can be developed based on the existing pyrometallurgical equipment rotary hearth furnace and rotary kiln, which is introduced briefly. However, the coal-based reduction is characterized by high carbon dioxide emissions, high energy consumption and high pollution. The development and application of coal-based reduction is expectedly hindered in the future. Technological innovation aiming at decreasing carbon dioxide emissions is a new trend of green and sustainable development of the steel industry. At present, substituting the coal with hydrogen for the iron oxides reduction is promising.

Invited Review
Mechanical, expansion and rheological properties of circulating fluidized bed fly ash based ecological cement: A critical review
Wei Zhang, Xiaoming Liu, and  Zengqi Zhang
, Available online 25 December 2021, https://doi.org/10.1007/s12613-021-2403-2
Abstract:

Circulating fluidized bed fly ash (CFBFA) is a solid waste of circulating fluidized bed (CFB) boilers in power plants, and the storage of CFBFA is becoming an increasingly environmental problem. Various methods have been developed to improve the performance of CFBFA based ecological cement (CEC). In this work, the physicochemical properties of CFBFA were introduced, and the recent research progress on the mechanical, expansion and rheological properties of CEC were extensively reviewed. The active silica-alumina component and SO3 inside CFBFA were beneficial to the development of CEC strength. In addition, the expansion rate of CEC was significantly increased by the f-CaO in CFBFA. The rheological properties of CEC are controlled by regulating CFBFA particle size. The challenge for f-CaO in CFBFA to compensate for cement volume shrinkage is proposed. Moreover, the environmental conservation, durability, and economy of CEC should be valued in the future research.

Invited Review
Reagent types and action mechanisms in flotation of ilmenite: A review
Jiaozhong Cai, Jiushuai Deng, Liang Wang, Mingzhen Hu, Hongxiang Xu, Xiao'an Hou, Bozeng Wu, and  Shimei Li
, Available online 16 November 2021, https://doi.org/10.1007/s12613-021-2380-5
Abstract:

Ilmenite is an essential mineral for the extraction of titanium. Conventional physical separation methods have difficulty recovering fine ilmenite, and dressing plants have begun applying flotation to recover ilmenite. The interaction of reagent groups with Ti and Fe sites on the ilmenite surface dramatically influences the ilmenite flotation. Nevertheless, the investigation on Fe sites has received more attention because the activity of Ti is lower than that of Fe. For the activators on ilmenite flotation, most are metal ions but typically lead ions. Metal ions of activators promote the flotation of ilmenite by increasing the active sites on the ilmenite surface. Combined reagents have a better selective separation of ilmenite than a single reagents due to its synergistic effect. Combining the lead ion (Pb2+) and the benzyl hydroxamic acid (BHA) into a Pb–BHA complex has a marked effect on ilmenite flotation, which puts forward a new idea of developing combined reagents for ilmenite flotation. This review considers reagent types and action mechanisms in flotation of ilmenite. Besides, based on the analysis of the previous work, a brief future outlook of reagent types and action mechanisms in flotation of ilmenite was also proposed in the study.

Research article
Significantly improved hydrogen storage behaviors in 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:
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 MgH2ywt%Nb (y = 0, 3, 5, 7, 9) composites. The MgH2–5wt%Nb composite started releasing hydrogen at 186.7°C 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 min at 250°C and had the ability to absorb 4.0wt% hydrogen in 30 min at 100°C. Cycling tests revealed that MgH2–5wt%Nb could retain 6.3wt% H2 storage capacity (89.2%) after 20 cycles. Dehydrogenation and hydrogenation activation energy values were decreased from 140.51±4.74 and 70.67±2.07 kJ·mol−1 to 90.04±2.83 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.