In Press
In Press articles are edited and published online ahead of issue. When the final article is assigned to volumes/issues, the Article in Press version will be removed and the final version will appear in the associated published volumes/issues.
- • Uncorrected proofs: articles that have been copy edited and formatted, but have not been finalized yet. They still need to be proof-read and corrected by the author(s) and the text could still change before final publication.
- • Corrected proofs: articles that contain the authors' corrections. Final citation details, e.g. volume and/or issue number, publication year and page numbers, still need to be added and the text might change before final publication.
There are two types in Press articles:
Display Method:
, Available online 27 February 2024,
https://doi.org/10.1007/s12613-024-2864-1
Abstract:
This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances. Firstly, the experimental apparatus, methods, and theories related to the disturbance dynamics of deep, high-stress rock are reviewed, followed by the introduction of scholars’ research on deep rock deformation and failure from an energy perspective. Subsequently, with a backdrop of high-stress phenomena in deep hard rock, such as rock bursts and core disking, we delves into the current state of research on rock microstructure analysis and residual stresses from the perspective of studying the energy storage mechanisms in rocks. Thereafter, the current state of research on the mechanical response and the energy dissipation of highly stressed rock formations is briefly retrospected. Finally, the insufficient aspects in the current research on the disturbance and failure mechanisms in deep highly stressed rock formations are summarized, and prospects for future research are provided. This work provides new avenues for the research on the mechanical response and damage-fracture mechanisms of rocks under high-stress conditions.
This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances. Firstly, the experimental apparatus, methods, and theories related to the disturbance dynamics of deep, high-stress rock are reviewed, followed by the introduction of scholars’ research on deep rock deformation and failure from an energy perspective. Subsequently, with a backdrop of high-stress phenomena in deep hard rock, such as rock bursts and core disking, we delves into the current state of research on rock microstructure analysis and residual stresses from the perspective of studying the energy storage mechanisms in rocks. Thereafter, the current state of research on the mechanical response and the energy dissipation of highly stressed rock formations is briefly retrospected. Finally, the insufficient aspects in the current research on the disturbance and failure mechanisms in deep highly stressed rock formations are summarized, and prospects for future research are provided. This work provides new avenues for the research on the mechanical response and damage-fracture mechanisms of rocks under high-stress conditions.
, Available online 3 November 2023,
https://doi.org/10.1007/s12613-023-2774-7
Abstract:
The practical engineering applications of powder metallurgy (PM) Ti alloys produced through cold compaction and pressureless sintering are impeded by poor sintering densification, embrittlement caused by excessive O impurities, and severe sintering deformation resulting from the use of heterogeneous powder mixtures. This review presents a summary of our previous work on addressing the above challenges. Initially, we proposed a novel strategy using reaction-induced liquid phases to enhance sintering densification. Near-complete density (relative density exceeding 99%) was achieved by applying the above strategy and newly developed sintering aids. By focusing on the O-induced embrittlement issue, we determined the onset dissolution temperature of oxide films in the Ti matrix. On the basis of this finding, we established a design criterion for effective O scavengers that require reaction with oxide films before their dissolution. Consequently, a ductile PM Ti alloy was successfully obtained by introducing 0.3wt% NdB6 as the O scavenger. Lastly, a powder-coating strategy was adopted to address the sintering deformation issue. The ultrafine size and shell-like distribution characteristics of coating particles ensured rapid dissolution and homogeneity in the Ti matrix, thereby facilitating linear shrinkage during sintering. As a result, geometrically complex Ti alloy parts with high dimensional accuracy were fabricated by using the coated powder. Our fundamental findings and related technical achievements enabled the development of an integrated production technology for the high-performance and accurate shaping of low-cost PM Ti alloys. Additionally, the primary engineering applications and progress in the industrialization practice of our developed technology are introduced in this review.
The practical engineering applications of powder metallurgy (PM) Ti alloys produced through cold compaction and pressureless sintering are impeded by poor sintering densification, embrittlement caused by excessive O impurities, and severe sintering deformation resulting from the use of heterogeneous powder mixtures. This review presents a summary of our previous work on addressing the above challenges. Initially, we proposed a novel strategy using reaction-induced liquid phases to enhance sintering densification. Near-complete density (relative density exceeding 99%) was achieved by applying the above strategy and newly developed sintering aids. By focusing on the O-induced embrittlement issue, we determined the onset dissolution temperature of oxide films in the Ti matrix. On the basis of this finding, we established a design criterion for effective O scavengers that require reaction with oxide films before their dissolution. Consequently, a ductile PM Ti alloy was successfully obtained by introducing 0.3wt% NdB6 as the O scavenger. Lastly, a powder-coating strategy was adopted to address the sintering deformation issue. The ultrafine size and shell-like distribution characteristics of coating particles ensured rapid dissolution and homogeneity in the Ti matrix, thereby facilitating linear shrinkage during sintering. As a result, geometrically complex Ti alloy parts with high dimensional accuracy were fabricated by using the coated powder. Our fundamental findings and related technical achievements enabled the development of an integrated production technology for the high-performance and accurate shaping of low-cost PM Ti alloys. Additionally, the primary engineering applications and progress in the industrialization practice of our developed technology are introduced in this review.
, Available online 3 November 2023,
https://doi.org/10.1007/s12613-023-2771-x
Abstract:
Solid oxide fuel cells (SOFCs) have attracted a great deal of interest because they have the highest efficiency without using any noble metal as catalysts among all the fuel cell technologies. However, traditional SOFCs suffer from having a higher volume, current leakage, complex connections, and difficulty in gas sealing. To solve these problems, Rolls-Royce has fabricated a simple design by stacking cells in series on an insulating porous support, resulting in the tubular segmented-in-series solid oxide fuel cells (SIS-SOFCs), which achieved higher output voltage. This work systematically reviews recent advances in the structures, preparation methods, performances, and stability of tubular SIS-SOFCs in experimental and numerical studies. Finally, the challenges and future development of tubular SIS-SOFCs are also discussed. The findings of this work can help guide the direction and inspire innovation of future development in this field.
Solid oxide fuel cells (SOFCs) have attracted a great deal of interest because they have the highest efficiency without using any noble metal as catalysts among all the fuel cell technologies. However, traditional SOFCs suffer from having a higher volume, current leakage, complex connections, and difficulty in gas sealing. To solve these problems, Rolls-Royce has fabricated a simple design by stacking cells in series on an insulating porous support, resulting in the tubular segmented-in-series solid oxide fuel cells (SIS-SOFCs), which achieved higher output voltage. This work systematically reviews recent advances in the structures, preparation methods, performances, and stability of tubular SIS-SOFCs in experimental and numerical studies. Finally, the challenges and future development of tubular SIS-SOFCs are also discussed. The findings of this work can help guide the direction and inspire innovation of future development in this field.
, Available online 28 September 2023,
https://doi.org/10.1007/s12613-023-2751-1
Abstract:
Plastic instability, including both the discontinuous yielding and stress serrations, has been frequently observed during the tensile deformation of medium-Mn steels (MMnS) and has been intensively studied in recent years. Unfortunately, research results are controversial, and no consensus has been achieved regarding the topic. Here, we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS, including the morphology and stability of austenite, the feature of the phase interface, and the deformation parameters. Then, we propose a universal mechanism to explain the conflicting experimental results. We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation. Meanwhile, the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite. Strain-induced martensitic transformation, influenced by the mechanical stability of austenite grain and deformation parameters, should not be the intrinsic cause of plastic instability. However, it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations, as well as the interaction between the interstitial atoms and dislocations in austenite grains.
Plastic instability, including both the discontinuous yielding and stress serrations, has been frequently observed during the tensile deformation of medium-Mn steels (MMnS) and has been intensively studied in recent years. Unfortunately, research results are controversial, and no consensus has been achieved regarding the topic. Here, we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS, including the morphology and stability of austenite, the feature of the phase interface, and the deformation parameters. Then, we propose a universal mechanism to explain the conflicting experimental results. We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation. Meanwhile, the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite. Strain-induced martensitic transformation, influenced by the mechanical stability of austenite grain and deformation parameters, should not be the intrinsic cause of plastic instability. However, it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations, as well as the interaction between the interstitial atoms and dislocations in austenite grains.
, Available online 9 September 2023,
https://doi.org/10.1007/s12613-023-2734-2
Abstract:
Cobalt has excellent electrochemical, magnetic, and heat properties. As a strategic resource, it has been applied in many high-tech products. However, the recent rapid growth of the battery industry has substantially depleted cobalt resources, leading to a crisis of cobalt resource supply. The paper examines cobalt ore reserves and distribution, and the recent development and consumption of cobalt resources are summarized as well. In addition, the principles, advantages and disadvantages, and research status of various methods are discussed comprehensively. It can be concluded that the use of diverse sources (Cu–Co ores, Ni–Co ores, zinc plant residues, and waste cobalt products) for cobalt production should be enhanced to meet developmental requirements. Furthermore, in recovery technology, the pyro-hydrometallurgical process employs pyrometallurgy as the pretreatment to modify the phase structure of cobalt minerals, enhancing its recovery in the hydrometallurgical stage and facilitating high-purity cobalt production. Consequently, it represents a promising technology for future cobalt recovery. Lastly, based on the above conclusions, the prospects for cobalt are assessed regarding cobalt ore processing and sustainable cobalt recycling, for which further study should be conducted.
Cobalt has excellent electrochemical, magnetic, and heat properties. As a strategic resource, it has been applied in many high-tech products. However, the recent rapid growth of the battery industry has substantially depleted cobalt resources, leading to a crisis of cobalt resource supply. The paper examines cobalt ore reserves and distribution, and the recent development and consumption of cobalt resources are summarized as well. In addition, the principles, advantages and disadvantages, and research status of various methods are discussed comprehensively. It can be concluded that the use of diverse sources (Cu–Co ores, Ni–Co ores, zinc plant residues, and waste cobalt products) for cobalt production should be enhanced to meet developmental requirements. Furthermore, in recovery technology, the pyro-hydrometallurgical process employs pyrometallurgy as the pretreatment to modify the phase structure of cobalt minerals, enhancing its recovery in the hydrometallurgical stage and facilitating high-purity cobalt production. Consequently, it represents a promising technology for future cobalt recovery. Lastly, based on the above conclusions, the prospects for cobalt are assessed regarding cobalt ore processing and sustainable cobalt recycling, for which further study should be conducted.
, Available online 27 February 2024,
https://doi.org/10.1007/s12613-024-2865-0
Abstract:
AlSi10Mg porous protective structure often produces different damage forms under compressive loading, and these damage modes affect its protective function. In order to well meet the service requirements, there is an urgent need to comprehensively understand the mechanical behavior and response mechanism of AlSi10Mg porous structures under compressive loading. In this paper, AlSi10Mg porous structures with three kinds of volume fractions are designed and optimized to meet the requirements of high-impact, strong-energy absorption, and lightweight characteristics. The mechanical behaviors of AlSi10Mg porous structures, including the stress–strain relationship, structural bearing state, deformation and damage modes, and energy absorption characteristics, were obtained through experimental studies at different loading rates. The damage pattern of the damage section indicates that AlSi10Mg porous structures have both ductile and brittle mechanical properties. Numerical simulation studies show that the AlSi10Mg porous structure undergoes shear damage due to relative misalignment along the diagonal cross-section, and the damage location is almost at 45° to the load direction, which is the most direct cause of its structural damage, revealing the damage mechanism of AlSi10Mg porous structures under the compressive load. The normalized energy absorption model constructed in the paper well interprets the energy absorption state of AlSi10Mg porous structures and gives the sensitive location of the structures, and the results of this paper provide important references for peers in structural design and optimization.
AlSi10Mg porous protective structure often produces different damage forms under compressive loading, and these damage modes affect its protective function. In order to well meet the service requirements, there is an urgent need to comprehensively understand the mechanical behavior and response mechanism of AlSi10Mg porous structures under compressive loading. In this paper, AlSi10Mg porous structures with three kinds of volume fractions are designed and optimized to meet the requirements of high-impact, strong-energy absorption, and lightweight characteristics. The mechanical behaviors of AlSi10Mg porous structures, including the stress–strain relationship, structural bearing state, deformation and damage modes, and energy absorption characteristics, were obtained through experimental studies at different loading rates. The damage pattern of the damage section indicates that AlSi10Mg porous structures have both ductile and brittle mechanical properties. Numerical simulation studies show that the AlSi10Mg porous structure undergoes shear damage due to relative misalignment along the diagonal cross-section, and the damage location is almost at 45° to the load direction, which is the most direct cause of its structural damage, revealing the damage mechanism of AlSi10Mg porous structures under the compressive load. The normalized energy absorption model constructed in the paper well interprets the energy absorption state of AlSi10Mg porous structures and gives the sensitive location of the structures, and the results of this paper provide important references for peers in structural design and optimization.
, Available online 27 December 2023,
https://doi.org/10.1007/s12613-023-2813-4
Abstract:
Comparative experiments and theoretical analysis of the surface chemistry changes of goethite (GT) and goethite containing Ni (GTN) in the lattice in the presence of salicylhydroxamic acid (SA) were performed. It was revealed that in the presence of 100 g·t−1 of SA, the flotation recovery of GTN and GT increased with increasing pH, achieving a maximum recovery of 98.9% for both minerals at pH 8.3 and decreasing beyond that pH, with GTN having a slightly higher recovery than GT, except at pH 8.3. This was further confirmed by the higher complexation energies of GTN∙∙∙SA (−883.87 kJ·mol−1) compared with GT···SA (−604.23 kJ·mol−1) resulting from covalent, closed-shell, and conventional hydrogen bonding. The higher adsorption of SA onto GTN relative to GT was due to the formation of a π-hole in GTN, thereby promoting a higher interaction of the collector with the mineral. Thus, the presence of Ni in the GT lattice improves and decreases the adsorption and desorption of SA onto and from the mineral, respectively, compared with those onto and from GT.
Comparative experiments and theoretical analysis of the surface chemistry changes of goethite (GT) and goethite containing Ni (GTN) in the lattice in the presence of salicylhydroxamic acid (SA) were performed. It was revealed that in the presence of 100 g·t−1 of SA, the flotation recovery of GTN and GT increased with increasing pH, achieving a maximum recovery of 98.9% for both minerals at pH 8.3 and decreasing beyond that pH, with GTN having a slightly higher recovery than GT, except at pH 8.3. This was further confirmed by the higher complexation energies of GTN∙∙∙SA (−883.87 kJ·mol−1) compared with GT···SA (−604.23 kJ·mol−1) resulting from covalent, closed-shell, and conventional hydrogen bonding. The higher adsorption of SA onto GTN relative to GT was due to the formation of a π-hole in GTN, thereby promoting a higher interaction of the collector with the mineral. Thus, the presence of Ni in the GT lattice improves and decreases the adsorption and desorption of SA onto and from the mineral, respectively, compared with those onto and from GT.
, Available online 15 December 2023,
https://doi.org/10.1007/s12613-023-2810-7
Abstract:
Incorporating a selenium (Se) positive electrode into aluminum (Al)-ion batteries is an effective strategy for improving the overall battery performance. However, the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products. In this work, we aim to harness the advantages of Se while reducing its limitations by preparing a core–shell mesoporous carbon hollow sphere with a titanium nitride (C@TiN) host to load 63.9wt% Se as the positive electrode material for Al–Se batteries. Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN, the obtained core–shell mesoporous carbon hollow spheres coated with Se (Se@C@TiN) display superior utilization of the active material and remarkable cycling stability. As a result, Al–Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g−1 at a current density of 1000 mA·g−1 while maintaining a discharge specific capacity of 86.0 mAh·g−1 over 200 cycles. This improved cycling performance is ascribed to the high electrical conductivity of the core–shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.
Incorporating a selenium (Se) positive electrode into aluminum (Al)-ion batteries is an effective strategy for improving the overall battery performance. However, the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products. In this work, we aim to harness the advantages of Se while reducing its limitations by preparing a core–shell mesoporous carbon hollow sphere with a titanium nitride (C@TiN) host to load 63.9wt% Se as the positive electrode material for Al–Se batteries. Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN, the obtained core–shell mesoporous carbon hollow spheres coated with Se (Se@C@TiN) display superior utilization of the active material and remarkable cycling stability. As a result, Al–Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g−1 at a current density of 1000 mA·g−1 while maintaining a discharge specific capacity of 86.0 mAh·g−1 over 200 cycles. This improved cycling performance is ascribed to the high electrical conductivity of the core–shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.
, Available online 8 December 2023,
https://doi.org/10.107/s12613-023-2808-1
Abstract:
Lithography is a pivotal micro/nanomanufacturing technique, facilitating performance enhancements in an extensive array of devices, encompassing sensors, transistors, and photovoltaic devices. The key to creating highly precise, multiscale-distributed patterned structures is the precise control of the lithography process. Herein, high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography. By optimizing these parameters, ZnO nanorod arrays with line/hole arrangements are successfully prepared. Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure, enlarged surface area, and improved light capture ability, which achieve highly efficient energy conversion in perovskite solar cells. The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.
Lithography is a pivotal micro/nanomanufacturing technique, facilitating performance enhancements in an extensive array of devices, encompassing sensors, transistors, and photovoltaic devices. The key to creating highly precise, multiscale-distributed patterned structures is the precise control of the lithography process. Herein, high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography. By optimizing these parameters, ZnO nanorod arrays with line/hole arrangements are successfully prepared. Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure, enlarged surface area, and improved light capture ability, which achieve highly efficient energy conversion in perovskite solar cells. The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.
, Available online 8 December 2023,
https://doi.org/10.1007/s12613-023-2806-3
Abstract:
Polypropylene (PP) fiber-reinforced cement-based tailings backfill (FRCTB) is a green compound material with superior crack resistance and has good prospects for application in underground mining. However, FRCTB exhibits susceptibility to dynamic events, such as impact ground pressure and blast vibrations. This paper investigates the energy and crack distribution behavior of FRCTB under dynamic impact, considering the height/diameter (H/D) effect. Split Hopkinson pressure bar, industrial computed tomography scan, and scanning electron microscopy (SEM) experiments were carried out on six types of FRCTB. Laboratory outcomes confirmed fiber aggregation at the bottom of specimens. When H/D was less than 0.8, the proportion of PP fibers distributed along the θ angle direction of 80°–90° increased. For the total energy, all samples presented similar energy absorption, reflectance, and transmittance. However, a rise in H/D may cause a rise in the energy absorption rate of FRCTB during the peak phase. A positive correlation existed between the average strain rate and absorbed energy per unit volume. The increase in H/D resulted in a decreased crack volume fraction of FRCTB. When the H/D was greater than or equal to 0.7, the maximum crack volume fraction of FRCTB was observed close to the incidence plane. Radial cracks were present only in the FRCTB with an H/D ratio of 0.5. Samples with H/D ratios of 0.5 and 0.6 showed similar distributions of weakly and heavily damaged areas. PP fibers can limit the emergence and expansion of cracks by influencing their path. SEM observations revealed considerable differences in the bonding strengths between fibers and the FRCTB. Fibers that adhered particularly well to the substrate were attracted together with the hydration products adhering to surfaces. These results show that FRCTB is promising as a sustainable and green backfill for determining the design properties of mining with backfill.
Polypropylene (PP) fiber-reinforced cement-based tailings backfill (FRCTB) is a green compound material with superior crack resistance and has good prospects for application in underground mining. However, FRCTB exhibits susceptibility to dynamic events, such as impact ground pressure and blast vibrations. This paper investigates the energy and crack distribution behavior of FRCTB under dynamic impact, considering the height/diameter (H/D) effect. Split Hopkinson pressure bar, industrial computed tomography scan, and scanning electron microscopy (SEM) experiments were carried out on six types of FRCTB. Laboratory outcomes confirmed fiber aggregation at the bottom of specimens. When H/D was less than 0.8, the proportion of PP fibers distributed along the θ angle direction of 80°–90° increased. For the total energy, all samples presented similar energy absorption, reflectance, and transmittance. However, a rise in H/D may cause a rise in the energy absorption rate of FRCTB during the peak phase. A positive correlation existed between the average strain rate and absorbed energy per unit volume. The increase in H/D resulted in a decreased crack volume fraction of FRCTB. When the H/D was greater than or equal to 0.7, the maximum crack volume fraction of FRCTB was observed close to the incidence plane. Radial cracks were present only in the FRCTB with an H/D ratio of 0.5. Samples with H/D ratios of 0.5 and 0.6 showed similar distributions of weakly and heavily damaged areas. PP fibers can limit the emergence and expansion of cracks by influencing their path. SEM observations revealed considerable differences in the bonding strengths between fibers and the FRCTB. Fibers that adhered particularly well to the substrate were attracted together with the hydration products adhering to surfaces. These results show that FRCTB is promising as a sustainable and green backfill for determining the design properties of mining with backfill.
, Available online 1 December 2023,
https://doi.org/10.1007/s12613-023-2801-8
Abstract:
This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hot-roll bonding (HRB) based on friction stir welding. The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum, and the tensile specimens fractured at the matrix after exceeding 1 Pa. Non-equilibrium grain boundaries were formed at the hot-rolled interface, and a large amount of Mg2Si particles were linearly precipitated along the interfacial grain boundaries (IGBs). During subsequent heat treatment, Mg2Si particles dissolved back into the matrix, and Al2O3 film remaining at the interface eventually evolved into MgO. In addition, the local IGBs underwent staged elimination during HRB, which facilitated the interface healing due to the fusion of grains at the interface. This process was achieved by the dissociation, emission, and annihilation of dislocations on the IGBs.
This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hot-roll bonding (HRB) based on friction stir welding. The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum, and the tensile specimens fractured at the matrix after exceeding 1 Pa. Non-equilibrium grain boundaries were formed at the hot-rolled interface, and a large amount of Mg2Si particles were linearly precipitated along the interfacial grain boundaries (IGBs). During subsequent heat treatment, Mg2Si particles dissolved back into the matrix, and Al2O3 film remaining at the interface eventually evolved into MgO. In addition, the local IGBs underwent staged elimination during HRB, which facilitated the interface healing due to the fusion of grains at the interface. This process was achieved by the dissociation, emission, and annihilation of dislocations on the IGBs.
, Available online 21 November 2023,
https://doi.org/10.1007/s12613-023-2789-0
Abstract:
The monomolecular surface layer of acceptor doped CeO2 may become neutral and metallic or charged and semiconducting. This is revealed in the theoretical analysis of the oxygen pressure dependence of the surface defects concentration in acceptor doped ceria with two different dopant types and operated under different oxygen pressures. Recently published experimental data for highly reduced Sm0.2Ce0.8O1.9–x (SDC) containing a fixed valence dopant Sm3+ are very different from those published for Pr0.1Ce0.9O2–x (PCO) with the variable valence dopant Pr4+/Pr3+ being reduced under milder conditions. The theoretical analysis of these experimental results fits very well the experimental results of SDC and PCO. It leads to the following predictions: the highly reduced surface of SDC is metallic and neutral, the metallic surface electron density of state is gs = 0.9 × 1038 J–1·m–2 (1.4 × 1015 eV–1·cm–2), the electron effective mass is meff,s = 3.3me, and the phase diagram of the reduced surface has the α (fcc) structure as in the bulk. In PCO a double layer is predicted to be formed between the surface and the bulk with the surface being negatively charged and semiconducting. The surface of PCO maintains high Pr3+ defect concentration as well as relative high oxygen vacancy concentration at oxygen pressures higher than in the bulk. The reasons for the difference between a metallic and semiconducting surface layer of acceptor doped CeO2 are reviewed, as well as the key theoretical considerations applied in coping with this problem. For that we make use of the experimental data and theoretical analysis available for acceptor doped ceria.
The monomolecular surface layer of acceptor doped CeO2 may become neutral and metallic or charged and semiconducting. This is revealed in the theoretical analysis of the oxygen pressure dependence of the surface defects concentration in acceptor doped ceria with two different dopant types and operated under different oxygen pressures. Recently published experimental data for highly reduced Sm0.2Ce0.8O1.9–x (SDC) containing a fixed valence dopant Sm3+ are very different from those published for Pr0.1Ce0.9O2–x (PCO) with the variable valence dopant Pr4+/Pr3+ being reduced under milder conditions. The theoretical analysis of these experimental results fits very well the experimental results of SDC and PCO. It leads to the following predictions: the highly reduced surface of SDC is metallic and neutral, the metallic surface electron density of state is gs = 0.9 × 1038 J–1·m–2 (1.4 × 1015 eV–1·cm–2), the electron effective mass is meff,s = 3.3me, and the phase diagram of the reduced surface has the α (fcc) structure as in the bulk. In PCO a double layer is predicted to be formed between the surface and the bulk with the surface being negatively charged and semiconducting. The surface of PCO maintains high Pr3+ defect concentration as well as relative high oxygen vacancy concentration at oxygen pressures higher than in the bulk. The reasons for the difference between a metallic and semiconducting surface layer of acceptor doped CeO2 are reviewed, as well as the key theoretical considerations applied in coping with this problem. For that we make use of the experimental data and theoretical analysis available for acceptor doped ceria.
, Available online 10 November 2023,
https://doi.org/10.1007/s12613-023-2780-9
Abstract:
Controlling the content of athermal martensite and retained austenite is important to improving the mechanical properties of high-strength steels, but a mechanism for the accurate description of martensitic transformation during the cooling process must be addressed. At present, frequently used semi-empirical kinetics models suffer from huge errors at the beginning of transformation, and most of them fail to exhibit the sigmoidal shape characteristic of transformation curves. To describe the martensitic transformation process accurately, based on the Magee model, we introduced the changes in the nucleation activation energy of martensite with temperature, which led to the varying nucleation rates of this model during martensitic transformation. According to the calculation results, the relative error of the modified model for the martensitic transformation kinetics curves of Fe–C–X (X = Ni, Cr, Mn, Si) alloys reached 9.5% compared with those measured via the thermal expansion method. The relative error was approximately reduced by two-thirds compared with that of the Magee model. The incorporation of nucleation activation energy into the kinetics model contributes to the improvement of its precision.
Controlling the content of athermal martensite and retained austenite is important to improving the mechanical properties of high-strength steels, but a mechanism for the accurate description of martensitic transformation during the cooling process must be addressed. At present, frequently used semi-empirical kinetics models suffer from huge errors at the beginning of transformation, and most of them fail to exhibit the sigmoidal shape characteristic of transformation curves. To describe the martensitic transformation process accurately, based on the Magee model, we introduced the changes in the nucleation activation energy of martensite with temperature, which led to the varying nucleation rates of this model during martensitic transformation. According to the calculation results, the relative error of the modified model for the martensitic transformation kinetics curves of Fe–C–X (X = Ni, Cr, Mn, Si) alloys reached 9.5% compared with those measured via the thermal expansion method. The relative error was approximately reduced by two-thirds compared with that of the Magee model. The incorporation of nucleation activation energy into the kinetics model contributes to the improvement of its precision.
, Available online 3 November 2023,
https://doi.org/10.1007/s12613-023-2772-9
Abstract:
Additive friction stir deposition (AFSD) is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years. In this work, the microstructural evolution and mechanical performance of the Al–Mg–Si alloy plate repaired by the preheating-assisted AFSD process were investigated. To evaluate the tool rotation speed and substrate preheating for repair quality, the AFSD technique was used to additively repair 5 mm depth blind holes on 6061 aluminum alloy substrates. The results showed that preheat-assisted AFSD repair significantly improved joint bonding and joint strength compared to the control non-preheat substrate condition. Moreover, increasing rotation speed was also beneficial to improve the metallurgical bonding of the interface and avoid volume defects. Under preheating conditions, the UTS and elongation were positively correlated with rotation speed. Under the process parameters of preheated substrate and tool rotation speed of 1000 r/min, defect-free specimens could be obtained accompanied by tensile fracture occurring in the substrate rather than the repaired zone. The UTS and elongation reached the maximum values of 164.2 MPa and 13.4%, which are equivalent to 99.4% and 140% of the heated substrate, respectively.
Additive friction stir deposition (AFSD) is a novel structural repair and manufacturing technology has become a research hotspot at home and abroad in the past five years. In this work, the microstructural evolution and mechanical performance of the Al–Mg–Si alloy plate repaired by the preheating-assisted AFSD process were investigated. To evaluate the tool rotation speed and substrate preheating for repair quality, the AFSD technique was used to additively repair 5 mm depth blind holes on 6061 aluminum alloy substrates. The results showed that preheat-assisted AFSD repair significantly improved joint bonding and joint strength compared to the control non-preheat substrate condition. Moreover, increasing rotation speed was also beneficial to improve the metallurgical bonding of the interface and avoid volume defects. Under preheating conditions, the UTS and elongation were positively correlated with rotation speed. Under the process parameters of preheated substrate and tool rotation speed of 1000 r/min, defect-free specimens could be obtained accompanied by tensile fracture occurring in the substrate rather than the repaired zone. The UTS and elongation reached the maximum values of 164.2 MPa and 13.4%, which are equivalent to 99.4% and 140% of the heated substrate, respectively.
, Available online 3 November 2023,
https://doi.org/10.1007/s12613-023-2775-6
Abstract:
Mg–6Zn–2X(Fe/Cu/Ni) alloys are prepared through semi-continuous casting, with the aim of identifying a degradable magnesium (Mg) alloy suitable for use in fracturing balls. A comparative analysis is conducted to assess the impacts of adding Cu and Ni, which result in finer grains and the formation of galvanic corrosion sites. Scanner electronic microscopy examination revealed that precipitated phases concentrated at grain boundaries, forming a semi-continuous network structure that facilitated corrosion penetration in Mg–6Zn–2Cu and Mg–6Zn–2Ni alloys. Pitting corrosion was observed in Mg–6Zn–2Fe, while galvanic corrosion was identified as the primary mechanism in Mg–6Zn–2Cu and Mg–6Zn–2Ni alloys. Among the tests, the Mg–6Zn–2Ni alloy exhibited the highest corrosion rate (approximately 932.9 mm/a) due to its significant potential difference. Mechanical testing showed that Mg–6Zn–2Ni alloy possessed suitable ultimate compressive strength, making it a potential candidate material for degradable fracturing balls, effectively addressing the challenges of balancing strength and degradation rate in fracturing applications.
Mg–6Zn–2X(Fe/Cu/Ni) alloys are prepared through semi-continuous casting, with the aim of identifying a degradable magnesium (Mg) alloy suitable for use in fracturing balls. A comparative analysis is conducted to assess the impacts of adding Cu and Ni, which result in finer grains and the formation of galvanic corrosion sites. Scanner electronic microscopy examination revealed that precipitated phases concentrated at grain boundaries, forming a semi-continuous network structure that facilitated corrosion penetration in Mg–6Zn–2Cu and Mg–6Zn–2Ni alloys. Pitting corrosion was observed in Mg–6Zn–2Fe, while galvanic corrosion was identified as the primary mechanism in Mg–6Zn–2Cu and Mg–6Zn–2Ni alloys. Among the tests, the Mg–6Zn–2Ni alloy exhibited the highest corrosion rate (approximately 932.9 mm/a) due to its significant potential difference. Mechanical testing showed that Mg–6Zn–2Ni alloy possessed suitable ultimate compressive strength, making it a potential candidate material for degradable fracturing balls, effectively addressing the challenges of balancing strength and degradation rate in fracturing applications.
, Available online 3 November 2023,
https://doi.org/10.1007/s12613-023-2770-y
Abstract:
CO2 electrochemical reduction (CO2ER) is an important research area for carbon neutralization. However, available catalysts for CO2 reduction are still characterized by limited stability and activity. Recently, metallic bismuth (Bi) has emerged as a promising catalyst for CO2ER. Herein, we report the solid cathode electroreduction of commercial micronized Bi2O3 as a straightforward approach for the preparation of nanostructured Bi. At −1.1 V versus reversible hydrogen electrode in a KHCO3 aqueous electrolyte, the resulting nanostructure Bi delivers a formate current density of ~40 mA cm−2 with a current efficiency of ~86%, and the formate selectivity reaches 97.6% at −0.78 V. Using nanosized Bi2O3 as the precursor can further reduce the primary particle sizes of the resulting Bi, leading to a significantly increased formate selectivity at relatively low overpotentials. The high catalytic activity of nanostructured Bi is attributable to the ultrafine and interconnected Bi nanoparticles in the nanoporous structure, which exposes abundant active sites for CO2 electrocatalytic reduction.
CO2 electrochemical reduction (CO2ER) is an important research area for carbon neutralization. However, available catalysts for CO2 reduction are still characterized by limited stability and activity. Recently, metallic bismuth (Bi) has emerged as a promising catalyst for CO2ER. Herein, we report the solid cathode electroreduction of commercial micronized Bi2O3 as a straightforward approach for the preparation of nanostructured Bi. At −1.1 V versus reversible hydrogen electrode in a KHCO3 aqueous electrolyte, the resulting nanostructure Bi delivers a formate current density of ~40 mA cm−2 with a current efficiency of ~86%, and the formate selectivity reaches 97.6% at −0.78 V. Using nanosized Bi2O3 as the precursor can further reduce the primary particle sizes of the resulting Bi, leading to a significantly increased formate selectivity at relatively low overpotentials. The high catalytic activity of nanostructured Bi is attributable to the ultrafine and interconnected Bi nanoparticles in the nanoporous structure, which exposes abundant active sites for CO2 electrocatalytic reduction.
, Available online 24 October 2023,
https://doi.org/10.1007/s12613-023-2767-6
Abstract:
The martensitic transformation temperature is the basis for the application of shape memory alloys (SMAs), and the ability to quickly and accurately predict the transformation temperature of SMAs has very important practical significance. In this work, machine learning (ML) methods were utilized to accelerate the search for shape memory alloys with targeted properties (phase transition temperature). A group of component data was selected to design shape memory alloys using reverse design method from numerous unexplored data. Component modeling and feature modeling were used to predict the phase transition temperature of the shape memory alloys. The experimental results of the shape memory alloys were obtained to verify the effectiveness of the support vector regression (SVR) model. The results show that the machine learning model can obtain target materials more efficiently and pertinently, and realize the accurate and rapid design of shape memory alloys with specific target phase transition temperature. On this basis, the relationship between phase transition temperature and material descriptors is analyzed, and it is proved that the key factors affecting the phase transition temperature of shape memory alloys are based on the strength of the bond energy between atoms. This work provides new ideas for the controllable design and performance optimization of Cu-based shape memory alloys.
The martensitic transformation temperature is the basis for the application of shape memory alloys (SMAs), and the ability to quickly and accurately predict the transformation temperature of SMAs has very important practical significance. In this work, machine learning (ML) methods were utilized to accelerate the search for shape memory alloys with targeted properties (phase transition temperature). A group of component data was selected to design shape memory alloys using reverse design method from numerous unexplored data. Component modeling and feature modeling were used to predict the phase transition temperature of the shape memory alloys. The experimental results of the shape memory alloys were obtained to verify the effectiveness of the support vector regression (SVR) model. The results show that the machine learning model can obtain target materials more efficiently and pertinently, and realize the accurate and rapid design of shape memory alloys with specific target phase transition temperature. On this basis, the relationship between phase transition temperature and material descriptors is analyzed, and it is proved that the key factors affecting the phase transition temperature of shape memory alloys are based on the strength of the bond energy between atoms. This work provides new ideas for the controllable design and performance optimization of Cu-based shape memory alloys.
, Available online 24 October 2023,
https://doi.org/10.1007/s12613-023-2765-8
Abstract:
To study the effects of the initiation position on the damage and fracture characteristics of linear-charge blasting, blasting model experiments were conducted in this study using computed tomography scanning and three-dimensional reconstruction methods. The fractal damage theory was used to quantify the crack distribution and damage degree of sandstone specimens after blasting. The results showed that regardless of an inverse or top initiation, due to compression deformation and sliding frictional resistance, the plugging medium of the borehole is effective. The energy of the explosive gas near the top of the borehole is consumed. This affects the effective crushing of rocks near the top of the borehole, where the extent of damage to Sections I and II is less than that of Sections III and IV. In addition, the analysis revealed that under conditions of top initiation, the reflected tensile damage of the rock at the free face of the top of the borehole and the compression deformation of the plug and friction consume more blasting energy, resulting in lower blasting energy efficiency for top initiation. As a result, the overall damage degree of the specimens in the top-initiation group was significantly smaller than that in the inverse-initiation group. Under conditions of inverse initiation, the blasting energy efficiency is greater, causing the specimen to experience greater damage. Therefore, in the engineering practice of rock tunnel cut blasting, to utilize blasting energy effectively and enhance the effects of rock fragmentation, using the inverse-initiation method is recommended. In addition, in three-dimensional (3D) rock blasting, the bottom of the borehole has obvious end effects under the conditions of inverse initiation, and the crack distribution at the bottom of the borehole is trumpet-shaped. The occurrence of an end effect in the 3D linear-charge blasting model experiment is related to the initiation position and the blocking condition.
To study the effects of the initiation position on the damage and fracture characteristics of linear-charge blasting, blasting model experiments were conducted in this study using computed tomography scanning and three-dimensional reconstruction methods. The fractal damage theory was used to quantify the crack distribution and damage degree of sandstone specimens after blasting. The results showed that regardless of an inverse or top initiation, due to compression deformation and sliding frictional resistance, the plugging medium of the borehole is effective. The energy of the explosive gas near the top of the borehole is consumed. This affects the effective crushing of rocks near the top of the borehole, where the extent of damage to Sections I and II is less than that of Sections III and IV. In addition, the analysis revealed that under conditions of top initiation, the reflected tensile damage of the rock at the free face of the top of the borehole and the compression deformation of the plug and friction consume more blasting energy, resulting in lower blasting energy efficiency for top initiation. As a result, the overall damage degree of the specimens in the top-initiation group was significantly smaller than that in the inverse-initiation group. Under conditions of inverse initiation, the blasting energy efficiency is greater, causing the specimen to experience greater damage. Therefore, in the engineering practice of rock tunnel cut blasting, to utilize blasting energy effectively and enhance the effects of rock fragmentation, using the inverse-initiation method is recommended. In addition, in three-dimensional (3D) rock blasting, the bottom of the borehole has obvious end effects under the conditions of inverse initiation, and the crack distribution at the bottom of the borehole is trumpet-shaped. The occurrence of an end effect in the 3D linear-charge blasting model experiment is related to the initiation position and the blocking condition.
, Available online 24 October 2023,
https://doi.org/10.1007/s12613-023-2768-5
Abstract:
Electromagnetic wave (EMW)-absorbing materials have considerable capacity in the military field and the prevention of EMW radiation from harming human health. However, obtaining lightweight, high-performance, and broadband EMW-absorbing material remains an overwhelming challenge. Creating dielectric/magnetic composites with customized structures is a strategy with great promise for the development of high-performance EMW-absorbing materials. Using layered double hydroxides as the precursors of bimetallic alloys and combining them with porous biomass-derived carbon materials is a potential way for constructing multi-interface heterostructures as efficient EMW-absorbing materials because they have synergistic losses, low costs, abundant resources, and light weights. Here, FeNi alloy nanosheet array/Lycopodium spore-derived carbon (FeNi/LSC) was prepared through a simple hydrothermal and carbonization method. FeNi/LSC presents ideal EMW-absorbing performance by benefiting from the FeNi alloy nanosheet array, sponge-like structure, capability for impedance matching, and improved dielectric/magnetic losses. As expected, FeNi/LSC exhibited the minimum reflection loss of −58.3 dB at 1.5 mm with 20wt% filler content and a widely effective absorption bandwidth of 4.92 GHz. FeNi/LSC composites with effective EMW-absorbing performance provide new insights into the customization of biomass-derived composites as high-performance and lightweight broadband EMW-absorbing materials.
Electromagnetic wave (EMW)-absorbing materials have considerable capacity in the military field and the prevention of EMW radiation from harming human health. However, obtaining lightweight, high-performance, and broadband EMW-absorbing material remains an overwhelming challenge. Creating dielectric/magnetic composites with customized structures is a strategy with great promise for the development of high-performance EMW-absorbing materials. Using layered double hydroxides as the precursors of bimetallic alloys and combining them with porous biomass-derived carbon materials is a potential way for constructing multi-interface heterostructures as efficient EMW-absorbing materials because they have synergistic losses, low costs, abundant resources, and light weights. Here, FeNi alloy nanosheet array/Lycopodium spore-derived carbon (FeNi/LSC) was prepared through a simple hydrothermal and carbonization method. FeNi/LSC presents ideal EMW-absorbing performance by benefiting from the FeNi alloy nanosheet array, sponge-like structure, capability for impedance matching, and improved dielectric/magnetic losses. As expected, FeNi/LSC exhibited the minimum reflection loss of −58.3 dB at 1.5 mm with 20wt% filler content and a widely effective absorption bandwidth of 4.92 GHz. FeNi/LSC composites with effective EMW-absorbing performance provide new insights into the customization of biomass-derived composites as high-performance and lightweight broadband EMW-absorbing materials.
, Available online 12 October 2023,
https://doi.org/10.1007/s12613-023-2760-0
Abstract:
The infamous type IV failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants. In this work, the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling, i.e., normalizing, cold rolling, and tempering (NCT), which was developed to improve the creep strength of the FGHAZ in G115 steel weldments. The NCT treatment effectively promoted the dissolution of preformed M23C6 particles and relieved the boundary segregation of C and Cr during welding thermal cycling, which accelerated the dispersed reprecipitation of M23C6 particles within the fresh reaustenitized grains during post-weld heat treatment. In addition, the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations. As a result, the interacting actions between precipitates, dislocations, and boundaries during creep were reinforced considerably. Following this strategy, the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%, which can further push the application of G115 steel in USC power plants.
The infamous type IV failure within the fine-grained heat-affected zone (FGHAZ) in G115 steel weldments seriously threatens the safe operation of ultra-supercritical (USC) power plants. In this work, the traditional thermo-mechanical treatment was modified via the replacement of hot-rolling with cold rolling, i.e., normalizing, cold rolling, and tempering (NCT), which was developed to improve the creep strength of the FGHAZ in G115 steel weldments. The NCT treatment effectively promoted the dissolution of preformed M23C6 particles and relieved the boundary segregation of C and Cr during welding thermal cycling, which accelerated the dispersed reprecipitation of M23C6 particles within the fresh reaustenitized grains during post-weld heat treatment. In addition, the precipitation of Cu-rich phases and MX particles was promoted evidently due to the deformation-induced dislocations. As a result, the interacting actions between precipitates, dislocations, and boundaries during creep were reinforced considerably. Following this strategy, the creep rupture life of the FGHAZ in G115 steel weldments can be prolonged by 18.6%, which can further push the application of G115 steel in USC power plants.
, Available online 12 October 2023,
https://doi.org/10.1007/s12613-023-2762-y
Abstract:
The Ti–5Al–2Sn–4Zr–4Mo–2Cr–1Fe (β-CEZ) alloy is considered as a potential structural material in the aviation industry due to its outstanding strength and corrosion resistance. Electrochemical machining (ECM) is an efficient and low-cost technology for manufacturing the β-CEZ alloy. In ECM, the machining parameter selection and tool design are based on the electrochemical dissolution behavior of the materials. In this study, the electrochemical dissolution behaviors of the β-CEZ and Ti–6Al–4V (TC4) alloys in NaNO3 solution are discussed. The open circuit potential (OCP), Tafel polarization, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and current efficiency curves of the β-CEZ and TC4 alloys are analyzed. The results show that, compared to the TC4 alloy, the passivation film structure is denser and the charge transfer resistance in the dissolution process is greater for the β-CEZ alloy. Moreover, the dissolved surface morphology of the two titanium-based alloys under different current densities are analyzed. Under low current densities, the β-CEZ alloy surface comprises dissolution pits and dissolved products, while the TC4 alloy surface comprises a porous honeycomb structure. Under high current densities, the surface waviness of both the alloys improves and the TC4 alloy surface is flatter and smoother than the β-CEZ alloy surface. Finally, the electrochemical dissolution models of β-CEZ and TC4 alloys are proposed.
The Ti–5Al–2Sn–4Zr–4Mo–2Cr–1Fe (β-CEZ) alloy is considered as a potential structural material in the aviation industry due to its outstanding strength and corrosion resistance. Electrochemical machining (ECM) is an efficient and low-cost technology for manufacturing the β-CEZ alloy. In ECM, the machining parameter selection and tool design are based on the electrochemical dissolution behavior of the materials. In this study, the electrochemical dissolution behaviors of the β-CEZ and Ti–6Al–4V (TC4) alloys in NaNO3 solution are discussed. The open circuit potential (OCP), Tafel polarization, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and current efficiency curves of the β-CEZ and TC4 alloys are analyzed. The results show that, compared to the TC4 alloy, the passivation film structure is denser and the charge transfer resistance in the dissolution process is greater for the β-CEZ alloy. Moreover, the dissolved surface morphology of the two titanium-based alloys under different current densities are analyzed. Under low current densities, the β-CEZ alloy surface comprises dissolution pits and dissolved products, while the TC4 alloy surface comprises a porous honeycomb structure. Under high current densities, the surface waviness of both the alloys improves and the TC4 alloy surface is flatter and smoother than the β-CEZ alloy surface. Finally, the electrochemical dissolution models of β-CEZ and TC4 alloys are proposed.
, Available online 12 October 2023,
https://doi.org/10.1007/s12613-023-2758-7
Abstract:
The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming (PHF) process directly determines the quality of the formed components. The microstructure stability of the pre-hardened sheets was investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and small angle X-ray scattering (SAXS), while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability tests. The results indicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging (NA). The deviations of ultimate tensile strength (UTS), yield strength (YS), and sheet formability (Erichsen value) are all less than 2%. Also, after different NA time (from 48 h to 1 month) is applied to alloys before pre-hardening treatment, the pre-hardened alloys possess stable microstructure and mechanical properties as well. Interestingly, with the extension of NA time before pre-hardening treatment from 48 h to 1 month, the contribution of NA to the pre-hardening treatment is limited. Only a yield strength increment of 20 MPa is achieved, with no loss in elongation. The limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston (GP) zones at the early stage of pre-hardening treatment, and the formation of θ'' phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.
The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming (PHF) process directly determines the quality of the formed components. The microstructure stability of the pre-hardened sheets was investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and small angle X-ray scattering (SAXS), while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability tests. The results indicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging (NA). The deviations of ultimate tensile strength (UTS), yield strength (YS), and sheet formability (Erichsen value) are all less than 2%. Also, after different NA time (from 48 h to 1 month) is applied to alloys before pre-hardening treatment, the pre-hardened alloys possess stable microstructure and mechanical properties as well. Interestingly, with the extension of NA time before pre-hardening treatment from 48 h to 1 month, the contribution of NA to the pre-hardening treatment is limited. Only a yield strength increment of 20 MPa is achieved, with no loss in elongation. The limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston (GP) zones at the early stage of pre-hardening treatment, and the formation of θ'' phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.
, Available online 12 October 2023,
https://doi.org/10.1007/s12613-023-2757-8
Abstract:
Te treatment is an effective method for modifying sulfide inclusions, and MnTe precipitation has an important effect on thermal brittleness and steel corrosion resistance. In most actual industrial applications of Te treatment, MnTe precipitation is unexpected. The critical precipitation behavior of MnTe inclusions was investigated through scanning electron microscopy, transmission electron microscopy, machine learning, and first-principles calculation. MnTe preferentially precipitated at the container mouth for sphere-like sulfides and at the interface between MnS grain boundaries and steel matrix for rod-like sulfides. The MnS/MnTe interface was semicoherent. A composition transition zone with a rock-salt structure exhibiting periodic changes existed to maintain the semicoherent interface. The critical precipitation behavior of MnTe inclusions in resulfurized steels involved three stages at varying temperatures. First, Mn(S,Te) precipitated during solidification. Second, MnTe with a rock-salt structure precipitated from Mn(S,Te). Third, MnTe with a hexagonal NiAs structure transformed from the rock-salt structure. The solubility of Te in MnS decreased with decreasing temperature. The critical precipitation behavior of MnTe inclusions in resulfurized steels was related to the MnS precipitation temperature. With the increase in MnS precipitation temperature, the critical Te/S weight ratio decreased. In consideration of the cost-effectiveness of Te addition for industrial production, the Te content in resulfurized steels should be controlled in accordance with MnS precipitation temperature and S content.
Te treatment is an effective method for modifying sulfide inclusions, and MnTe precipitation has an important effect on thermal brittleness and steel corrosion resistance. In most actual industrial applications of Te treatment, MnTe precipitation is unexpected. The critical precipitation behavior of MnTe inclusions was investigated through scanning electron microscopy, transmission electron microscopy, machine learning, and first-principles calculation. MnTe preferentially precipitated at the container mouth for sphere-like sulfides and at the interface between MnS grain boundaries and steel matrix for rod-like sulfides. The MnS/MnTe interface was semicoherent. A composition transition zone with a rock-salt structure exhibiting periodic changes existed to maintain the semicoherent interface. The critical precipitation behavior of MnTe inclusions in resulfurized steels involved three stages at varying temperatures. First, Mn(S,Te) precipitated during solidification. Second, MnTe with a rock-salt structure precipitated from Mn(S,Te). Third, MnTe with a hexagonal NiAs structure transformed from the rock-salt structure. The solubility of Te in MnS decreased with decreasing temperature. The critical precipitation behavior of MnTe inclusions in resulfurized steels was related to the MnS precipitation temperature. With the increase in MnS precipitation temperature, the critical Te/S weight ratio decreased. In consideration of the cost-effectiveness of Te addition for industrial production, the Te content in resulfurized steels should be controlled in accordance with MnS precipitation temperature and S content.
, Available online 29 September 2023,
https://doi.org/10.1007/s12613-023-2756-9
Abstract:
Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize, which makes it difficult to separate the mineral phases through conventional beneficiation. This study proposed a new treatment called flash reduction–melting separation (FRMS) for boron-bearing iron concentrates. In this method, the concentrates were first flash-reduced at the temperature under which the particles melt, and the slag and the reduced iron phases disengaged at the particle scale. Good reduction and melting effects were achieved above 1550°C. The B2O3 content in the separated slag was over 18wt%, and the B content in the iron was less than 0.03wt%. The proposed FRMS method was tested to investigate the effects of factors such as ore particle size and temperature on the reduction and melting steps with and without pre-reducing the raw concentrate. The mineral phase transformation and morphology evolution in the ore particles during FRMS were also comprehensively analyzed.
Boron is an important industrial raw material often sourced from minerals containing different compounds that cocrystallize, which makes it difficult to separate the mineral phases through conventional beneficiation. This study proposed a new treatment called flash reduction–melting separation (FRMS) for boron-bearing iron concentrates. In this method, the concentrates were first flash-reduced at the temperature under which the particles melt, and the slag and the reduced iron phases disengaged at the particle scale. Good reduction and melting effects were achieved above 1550°C. The B2O3 content in the separated slag was over 18wt%, and the B content in the iron was less than 0.03wt%. The proposed FRMS method was tested to investigate the effects of factors such as ore particle size and temperature on the reduction and melting steps with and without pre-reducing the raw concentrate. The mineral phase transformation and morphology evolution in the ore particles during FRMS were also comprehensively analyzed.
, Available online 28 September 2023,
https://doi.org/10.1007/s12613-023-2752-0
Abstract:
This work proposed a strategy of indirectly inducing uniform microarc discharge by controlling the content and distribution of β-Mg17Al12 phase in AZ91D Mg alloy. Two kinds of nano-particles (ZrO2 and TiO2) were designed to be added into the substrate of Mg alloy by friction stir processing (FSP). Then, Mg alloy sample designed with different precipitated morphology of β-Mg17Al12 phase was treated by microarc oxidation (MAO) in Na3PO4/Na2SiO3 electrolyte. The characteristics and performance of the MAO coating was analyzed using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle meter, and potentiodynamic polarization. It was found that the coarse α-Mg grains in extruded AZ91D Mg alloy were refined by FSP, and the β-Mg17Al12 phase with reticular structure was broken and dispersed. The nano-ZrO2 particles were pinned at the grain boundary by FSP, which refined the α-Mg grain and promoted the precipitation of β-Mg17Al12 phase in grains. It effectively inhibited the “cascade” phenomenon of microarcs, which induced the uniform distribution of discharge pores. The MAO coating on Zr-FSP sample had good wettability and corrosion resistance. However, TiO2 particles were hardly detected in the coating on Ti-FSP sample.
This work proposed a strategy of indirectly inducing uniform microarc discharge by controlling the content and distribution of β-Mg17Al12 phase in AZ91D Mg alloy. Two kinds of nano-particles (ZrO2 and TiO2) were designed to be added into the substrate of Mg alloy by friction stir processing (FSP). Then, Mg alloy sample designed with different precipitated morphology of β-Mg17Al12 phase was treated by microarc oxidation (MAO) in Na3PO4/Na2SiO3 electrolyte. The characteristics and performance of the MAO coating was analyzed using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle meter, and potentiodynamic polarization. It was found that the coarse α-Mg grains in extruded AZ91D Mg alloy were refined by FSP, and the β-Mg17Al12 phase with reticular structure was broken and dispersed. The nano-ZrO2 particles were pinned at the grain boundary by FSP, which refined the α-Mg grain and promoted the precipitation of β-Mg17Al12 phase in grains. It effectively inhibited the “cascade” phenomenon of microarcs, which induced the uniform distribution of discharge pores. The MAO coating on Zr-FSP sample had good wettability and corrosion resistance. However, TiO2 particles were hardly detected in the coating on Ti-FSP sample.
, Available online 28 September 2023,
https://doi.org/10.1007/s12613-023-2755-x
Abstract:
This paper proposes luteolin (LUT) as a novel depressant for the flotation-based separation of scheelite and calcite in a sodium oleate (NaOL) system. The suitability of LUT as a calcite depressant is confirmed through micro-flotation testing. At pH = 9, with LUT concentration of 50 mg·L–1 and NaOL concentration of 50 mg·L–1, scheelite recovery reaches 80.3%. Calcite, on the other hand, exhibits a recovery rate of 17.6%, indicating a significant difference in floatability between the two minerals. Subsequently, the surface modifications of scheelite and calcite following LUT treatment are characterized using adsorption capacity testing, Zeta potential analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The study investigates the selective depressant mechanism of LUT on calcite. Adsorption capacity testing and Zeta potential analysis demonstrate substantial absorption of LUT on the surface of calcite, impeding the further adsorption of sodium oleate, while its impact on scheelite is minimal. FT-IR and XPS analyses reveal the selective adsorption of LUT onto the surface of calcite, forming strong chemisorption bonds between the hydroxyl group and calcium ions present. AFM directly illustrates the distinct adsorption densities of LUT on the two mineral types. Consequently, LUT can effectively serve as a depressant for calcite, enabling the successful separation of scheelite and calcite.
This paper proposes luteolin (LUT) as a novel depressant for the flotation-based separation of scheelite and calcite in a sodium oleate (NaOL) system. The suitability of LUT as a calcite depressant is confirmed through micro-flotation testing. At pH = 9, with LUT concentration of 50 mg·L–1 and NaOL concentration of 50 mg·L–1, scheelite recovery reaches 80.3%. Calcite, on the other hand, exhibits a recovery rate of 17.6%, indicating a significant difference in floatability between the two minerals. Subsequently, the surface modifications of scheelite and calcite following LUT treatment are characterized using adsorption capacity testing, Zeta potential analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The study investigates the selective depressant mechanism of LUT on calcite. Adsorption capacity testing and Zeta potential analysis demonstrate substantial absorption of LUT on the surface of calcite, impeding the further adsorption of sodium oleate, while its impact on scheelite is minimal. FT-IR and XPS analyses reveal the selective adsorption of LUT onto the surface of calcite, forming strong chemisorption bonds between the hydroxyl group and calcium ions present. AFM directly illustrates the distinct adsorption densities of LUT on the two mineral types. Consequently, LUT can effectively serve as a depressant for calcite, enabling the successful separation of scheelite and calcite.
, Available online 20 September 2023,
https://doi.org/10.1007/s12613-023-2748-9
Abstract:
Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis. Herein, porous TiFe2 intermetallics were fabricated by the reactive synthesis of elemental powders. The phase transformation and pore formation of porous TiFe2 intermetallics were investigated, and its corrosion behavior and hydrogen evolution reaction (HER) performance in alkali solution were studied. Porous TiFe2 intermetallics with porosity in the range of 34.4%–56.4% were synthesized by the diffusion reaction of Ti and Fe elements, and the pore formation of porous TiFe2 intermetallic compound is the result of a combination of the bridging effect and the Kirkendall effect. The porous TiFe2 samples exhibit better corrosion resistance compared with porous 316L stainless steel, which is related to the formation of uniform nanosheets on the surface that hinder further corrosion, and porous TiFe2 electrode shows the overpotential of 220.6 and 295.6 mV at 10 and 100 mA·cm−2, suggesting a good catalytic performance. The synthesized porous Fe-based intermetallic has a controllable pore structure as well as excellent corrosion resistance, showing its potential in the field of filtration and separation.
Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis. Herein, porous TiFe2 intermetallics were fabricated by the reactive synthesis of elemental powders. The phase transformation and pore formation of porous TiFe2 intermetallics were investigated, and its corrosion behavior and hydrogen evolution reaction (HER) performance in alkali solution were studied. Porous TiFe2 intermetallics with porosity in the range of 34.4%–56.4% were synthesized by the diffusion reaction of Ti and Fe elements, and the pore formation of porous TiFe2 intermetallic compound is the result of a combination of the bridging effect and the Kirkendall effect. The porous TiFe2 samples exhibit better corrosion resistance compared with porous 316L stainless steel, which is related to the formation of uniform nanosheets on the surface that hinder further corrosion, and porous TiFe2 electrode shows the overpotential of 220.6 and 295.6 mV at 10 and 100 mA·cm−2, suggesting a good catalytic performance. The synthesized porous Fe-based intermetallic has a controllable pore structure as well as excellent corrosion resistance, showing its potential in the field of filtration and separation.
, Available online 20 September 2023,
https://doi.org/10.1007/s12613-023-2750-2
Abstract:
Electrochemical lithium extraction from salt lakes is an effective strategy for obtaining lithium at a low cost. Nevertheless, the elevated Mg:Li ratio and the presence of numerous coexisting ions in salt lake brines give rise to challenges, such as prolonged lithium extraction periods, diminished lithium extraction efficiency, and considerable environmental pollution. In this work, LiFePO4 (LFP) served as the electrode material for electrochemical lithium extraction. The conductive network in the LFP electrode was optimized by adjusting the type of conductive agent. This approach resulted in high lithium extraction efficiency and extended cycle life. When the single conductive agent of acetylene black (AB) or multiwalled carbon nanotubes (MWCNTs) was replaced with the mixed conductive agent of AB/MWCNTs, the average diffusion coefficient of Li+ in the electrode increased from 2.35 × 10−9 or 1.77 × 10−9 to 4.21 × 10−9 cm2·s−1. At the current density of 20 mA·g−1, the average lithium extraction capacity per gram of LFP electrode increased from 30.36 mg with the single conductive agent (AB) to 35.62 mg with the mixed conductive agent (AB/MWCNTs). When the mixed conductive agent was used, the capacity retention of the electrode after 30 cycles reached 82.9%, which was considerably higher than the capacity retention of 65.8% obtained when the single AB was utilized. Meanwhile, the electrode with mixed conductive agent of AB/MWCNTs provided good cycling performance. When the conductive agent content decreased or the loading capacity increased, the electrode containing the mixed conductive agent continued to show excellent electrochemical performance. Furthermore, a self-designed, highly efficient, continuous lithium extraction device was constructed. The electrode utilizing the AB/MWCNT mixed conductive agent maintained excellent adsorption capacity and cycling performance in this device. This work provides a new perspective for the electrochemical extraction of lithium using LFP electrodes.
Electrochemical lithium extraction from salt lakes is an effective strategy for obtaining lithium at a low cost. Nevertheless, the elevated Mg:Li ratio and the presence of numerous coexisting ions in salt lake brines give rise to challenges, such as prolonged lithium extraction periods, diminished lithium extraction efficiency, and considerable environmental pollution. In this work, LiFePO4 (LFP) served as the electrode material for electrochemical lithium extraction. The conductive network in the LFP electrode was optimized by adjusting the type of conductive agent. This approach resulted in high lithium extraction efficiency and extended cycle life. When the single conductive agent of acetylene black (AB) or multiwalled carbon nanotubes (MWCNTs) was replaced with the mixed conductive agent of AB/MWCNTs, the average diffusion coefficient of Li+ in the electrode increased from 2.35 × 10−9 or 1.77 × 10−9 to 4.21 × 10−9 cm2·s−1. At the current density of 20 mA·g−1, the average lithium extraction capacity per gram of LFP electrode increased from 30.36 mg with the single conductive agent (AB) to 35.62 mg with the mixed conductive agent (AB/MWCNTs). When the mixed conductive agent was used, the capacity retention of the electrode after 30 cycles reached 82.9%, which was considerably higher than the capacity retention of 65.8% obtained when the single AB was utilized. Meanwhile, the electrode with mixed conductive agent of AB/MWCNTs provided good cycling performance. When the conductive agent content decreased or the loading capacity increased, the electrode containing the mixed conductive agent continued to show excellent electrochemical performance. Furthermore, a self-designed, highly efficient, continuous lithium extraction device was constructed. The electrode utilizing the AB/MWCNT mixed conductive agent maintained excellent adsorption capacity and cycling performance in this device. This work provides a new perspective for the electrochemical extraction of lithium using LFP electrodes.
, Available online 13 September 2023,
https://doi.org/10.1007/s12613-023-2743-1
Abstract:
Water-quenched copper-nickel metallurgical slag enriched with olivine minerals exhibits promising potential for the production of CO2-mineralized cementitious materials. In this work, copper-nickel slag-based cementitious material (CNCM) was synthesized by using different chemical activation methods to enhance its hydration reactivity and CO2 mineralization capacity. Different water curing ages and carbonation conditions were explored related to their carbonation and mechanical properties development. Meanwhile, thermogravimetry differential scanning calorimetry and X-ray diffraction methods were applied to evaluate the CO2 adsorption amount and carbonation products of CNCM. Microstructure development of carbonated CNCM blocks was examined by backscattered electron imaging (BSE) with energy-dispersive X-ray spectrometry. Results showed that among the studied samples, the CNCM sample that was subjected to water curing for 3 d exhibited the highest CO2 sequestration amount of 8.51wt% at 80°C and 72 h while presenting the compressive strength of 39.07 MPa. This result indicated that 1 t of this CNCM can sequester 85.1 kg of CO2 and exhibit high compressive strength. Although the addition of citric acid did not improve strength development, it was beneficial to increase the CO2 diffusion and adsorption amount under the same carbonation conditions from BSE results. This work provides guidance for synthesizing CO2-mineralized cementitious materials using large amounts of metallurgical slags containing olivine minerals.
Water-quenched copper-nickel metallurgical slag enriched with olivine minerals exhibits promising potential for the production of CO2-mineralized cementitious materials. In this work, copper-nickel slag-based cementitious material (CNCM) was synthesized by using different chemical activation methods to enhance its hydration reactivity and CO2 mineralization capacity. Different water curing ages and carbonation conditions were explored related to their carbonation and mechanical properties development. Meanwhile, thermogravimetry differential scanning calorimetry and X-ray diffraction methods were applied to evaluate the CO2 adsorption amount and carbonation products of CNCM. Microstructure development of carbonated CNCM blocks was examined by backscattered electron imaging (BSE) with energy-dispersive X-ray spectrometry. Results showed that among the studied samples, the CNCM sample that was subjected to water curing for 3 d exhibited the highest CO2 sequestration amount of 8.51wt% at 80°C and 72 h while presenting the compressive strength of 39.07 MPa. This result indicated that 1 t of this CNCM can sequester 85.1 kg of CO2 and exhibit high compressive strength. Although the addition of citric acid did not improve strength development, it was beneficial to increase the CO2 diffusion and adsorption amount under the same carbonation conditions from BSE results. This work provides guidance for synthesizing CO2-mineralized cementitious materials using large amounts of metallurgical slags containing olivine minerals.
, Available online 13 September 2023,
https://doi.org/10.1007/s12613-023-2742-2
Abstract:
CsPbX3-based (X = I, Br, Cl) inorganic perovskite solar cells (PSCs) prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal stability. However, the high trap state density and serious charge recombination between low-temperature processed TiO2 film and inorganic perovskite layer interface seriously restrict the performance of all-inorganic PSCs. Here a thin polyethylene oxide (PEO) layer is employed to modify TiO2 film to passivate traps and promote carrier collection. The impacts of PEO layer on microstructure and photoelectric characteristics of TiO2 film and related devices are systematically studied. Characterization results suggest that PEO modification can reduce the surface roughness of TiO2 film, decrease its average surface potential, and passivate trap states. At optimal conditions, the champion efficiency of CsPbI2Br PSCs with PEO-modified TiO2 (PEO-PSCs) has been improved to 11.24% from 9.03% of reference PSCs. Moreover, the hysteresis behavior and charge recombination have been suppressed in PEO-PSCs.
CsPbX3-based (X = I, Br, Cl) inorganic perovskite solar cells (PSCs) prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal stability. However, the high trap state density and serious charge recombination between low-temperature processed TiO2 film and inorganic perovskite layer interface seriously restrict the performance of all-inorganic PSCs. Here a thin polyethylene oxide (PEO) layer is employed to modify TiO2 film to passivate traps and promote carrier collection. The impacts of PEO layer on microstructure and photoelectric characteristics of TiO2 film and related devices are systematically studied. Characterization results suggest that PEO modification can reduce the surface roughness of TiO2 film, decrease its average surface potential, and passivate trap states. At optimal conditions, the champion efficiency of CsPbI2Br PSCs with PEO-modified TiO2 (PEO-PSCs) has been improved to 11.24% from 9.03% of reference PSCs. Moreover, the hysteresis behavior and charge recombination have been suppressed in PEO-PSCs.
, Available online 9 September 2023,
https://doi.org/10.1007/s12613-023-2739-x
Abstract:
The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process. In this study, the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments. Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’ diffusion and phase transformation during the roasting process. The results indicated that limestone decomposed into calcium oxide, and magnetite was oxidized to hematite at the early stage of preheating. With the increase in roasting temperature, the diffusion rate of Fe and Ca was obviously accelerated, while the diffusion rate of Si was relatively slow. The order of magnitude of interdiffusion coefficient of Fe2O3–CaO diffusion couple was 10−10 m2·s−1 at a roasting temperature of 1200°C for 9 h. Ca2Fe2O5 was the initial product in the Fe2O3–CaO–SiO2 diffusion interface, and then Ca2Fe2O5 continued to react with Fe2O3 to form CaFe2O4. With the expansion of the diffusion region, the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO2 into CaFe2O4, which can strengthen the consolidation of fluxed pellets. Furthermore, andradite would be formed around a small part of quartz particles, which is also conducive to the consolidation of fluxed pellets. In addition, the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.
The increase to the proportion of fluxed pellets in the blast furnace burden is a useful way to reduce the carbon emissions in the ironmaking process. In this study, the interaction between calcium carbonate and iron ore powder and the mineralization mechanism of fluxed iron ore pellet in the roasting process were investigated through diffusion couple experiments. Scanning electron microscopy with energy dispersive spectroscopy was used to study the elements’ diffusion and phase transformation during the roasting process. The results indicated that limestone decomposed into calcium oxide, and magnetite was oxidized to hematite at the early stage of preheating. With the increase in roasting temperature, the diffusion rate of Fe and Ca was obviously accelerated, while the diffusion rate of Si was relatively slow. The order of magnitude of interdiffusion coefficient of Fe2O3–CaO diffusion couple was 10−10 m2·s−1 at a roasting temperature of 1200°C for 9 h. Ca2Fe2O5 was the initial product in the Fe2O3–CaO–SiO2 diffusion interface, and then Ca2Fe2O5 continued to react with Fe2O3 to form CaFe2O4. With the expansion of the diffusion region, the sillico-ferrite of calcium liquid phase was produced due to the melting of SiO2 into CaFe2O4, which can strengthen the consolidation of fluxed pellets. Furthermore, andradite would be formed around a small part of quartz particles, which is also conducive to the consolidation of fluxed pellets. In addition, the principle diagram of limestone and quartz diffusion reaction in the process of fluxed pellet roasting was discussed.
, Available online 9 September 2023,
https://doi.org/10.1007/s12613-023-2741-3
Abstract:
Traditional hydrometallurgical methods for recovering spent lithium-ion batteries (LIBs) involve acid leaching to simultaneously extract all valuable metals into the leachate. These methods usually are followed by a series of separation steps such as precipitation, extraction, and stripping to separate the individual valuable metals. In this study, we present a process for selectively leaching lithium through the synergistic effect of sulfuric and oxalic acids. Under optimal leaching conditions (leaching time of 1.5 h, leaching temperature of 70°C, liquid–solid ratio of 4 mL/g, oxalic acid ratio of 1.3, and sulfuric acid ratio of 1.3), the lithium leaching efficiency reached 89.6%, and the leaching efficiencies of Ni, Co, and Mn were 12.8%, 6.5%, and 21.7%. X-ray diffraction (XRD) and inductively coupled plasma optical emission spectrometer (ICP-OES) analyses showed that most of the Ni, Co, and Mn in the raw material remained as solid residue oxides and oxalates. This study offers a new approach to enriching the relevant theory for selectively recovering lithium from spent LIBs.
Traditional hydrometallurgical methods for recovering spent lithium-ion batteries (LIBs) involve acid leaching to simultaneously extract all valuable metals into the leachate. These methods usually are followed by a series of separation steps such as precipitation, extraction, and stripping to separate the individual valuable metals. In this study, we present a process for selectively leaching lithium through the synergistic effect of sulfuric and oxalic acids. Under optimal leaching conditions (leaching time of 1.5 h, leaching temperature of 70°C, liquid–solid ratio of 4 mL/g, oxalic acid ratio of 1.3, and sulfuric acid ratio of 1.3), the lithium leaching efficiency reached 89.6%, and the leaching efficiencies of Ni, Co, and Mn were 12.8%, 6.5%, and 21.7%. X-ray diffraction (XRD) and inductively coupled plasma optical emission spectrometer (ICP-OES) analyses showed that most of the Ni, Co, and Mn in the raw material remained as solid residue oxides and oxalates. This study offers a new approach to enriching the relevant theory for selectively recovering lithium from spent LIBs.
, Available online 9 September 2023,
https://doi.org/10.1007/s12613-023-2735-1
Abstract:
The proper recycling of spent lithium-ion batteries (LIBs) can promote the recovery and utilization of valuable resources, while also negative environmental effects resulting from the presence of toxic and hazardous substances. In this study, a new environmentally friendly hydro-metallurgical process was proposed for leaching lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) from spent LIBs using sulfuric acid with citric acid as a reductant. The effects of the concentration of sulfuric acid, the leaching temperature, the leaching time, the solid–liquid ratio, and the reducing agent dosage on the leaching behavior of the above elements were investigated. Key parameters were optimized using response surface methodology (RSM) to maximize the recovery of metals from spent LIBs. The maximum recovery efficiencies of Li, Ni, Co, and Mn can reach 99.08%, 98.76%, 98.33%, and 97.63%. under the optimized conditions (the sulfuric acid concentration was 1.16 mol/L, the citric acid dosage was 15wt%, the solid–liquid ratio was 40 g/L, and the temperature was 83°C for 120 min), respectively. It was found that in the collaborative leaching process of sulfuric acid and citric acid, the citric acid initially provided strong reducing\begin{document}$ {\text{CO}}_{\text{2}}^{\text{·}-} $\end{document} , and the transition metal ions in the high state underwent a reduction reaction to produce transition metal ions in the low state. Additionally, citric acid can also act as a proton donor and chelate with lower-priced transition metal ions, thus speeding up the dissolution process.
The proper recycling of spent lithium-ion batteries (LIBs) can promote the recovery and utilization of valuable resources, while also negative environmental effects resulting from the presence of toxic and hazardous substances. In this study, a new environmentally friendly hydro-metallurgical process was proposed for leaching lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) from spent LIBs using sulfuric acid with citric acid as a reductant. The effects of the concentration of sulfuric acid, the leaching temperature, the leaching time, the solid–liquid ratio, and the reducing agent dosage on the leaching behavior of the above elements were investigated. Key parameters were optimized using response surface methodology (RSM) to maximize the recovery of metals from spent LIBs. The maximum recovery efficiencies of Li, Ni, Co, and Mn can reach 99.08%, 98.76%, 98.33%, and 97.63%. under the optimized conditions (the sulfuric acid concentration was 1.16 mol/L, the citric acid dosage was 15wt%, the solid–liquid ratio was 40 g/L, and the temperature was 83°C for 120 min), respectively. It was found that in the collaborative leaching process of sulfuric acid and citric acid, the citric acid initially provided strong reducing
, Available online 9 September 2023,
https://doi.org/10.1007/s12613-023-2737-z
Abstract:
With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(VI) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(VI). The waste amidoxime resin was first modified with H3PO4 and ZnCl2, and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(VI) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(VI) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(VI) to Cr(III) and decrease the toxicity of Cr(VI) during adsorption. PPR-Z exhibited Cr(VI) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(VI) adsorption are the chemical reduction of Cr(VI) into Cr(III) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(VI) pollution and realizes the concept of “treating waste with waste.”
With the application of resins in various fields, numerous waste resins that are difficult to treat have been produced. The industrial wastewater containing Cr(VI) has severely polluted soil and groundwater environments, thereby endangering human health. Therefore, in this paper, a novel functionalized mesoporous adsorbent PPR-Z was synthesized from waste amidoxime resin for adsorbing Cr(VI). The waste amidoxime resin was first modified with H3PO4 and ZnCl2, and subsequently, it was carbonized through slow thermal decomposition. The static adsorption of PPR-Z conforms to the pseudo-second-order kinetic model and Langmuir isotherm, indicating that the Cr(VI) adsorption by PPR-Z is mostly chemical adsorption and exhibits single-layer adsorption. The saturated adsorption capacity of the adsorbent for Cr(VI) could reach 255.86 mg/g. The adsorbent could effectively reduce Cr(VI) to Cr(III) and decrease the toxicity of Cr(VI) during adsorption. PPR-Z exhibited Cr(VI) selectivity in electroplating wastewater. The main mechanisms involved in the Cr(VI) adsorption are the chemical reduction of Cr(VI) into Cr(III) and electrostatic and coordination interactions. Preparation of PPR-Z not only solves the problem of waste resin treatment but also effectively controls Cr(VI) pollution and realizes the concept of “treating waste with waste.”
, Available online 25 August 2023,
https://doi.org/10.1007/s12613-023-2732-4
Abstract:
The machine learning models of multiple linear regression (MLR), support vector regression (SVR), and extreme learning machine (ELM) and the proposed ELM models of online sequential ELM (OS-ELM) and OS-ELM with forgetting mechanism (FOS-ELM) are applied in the prediction of the lime utilization ratio of dephosphorization in the basic oxygen furnace steelmaking process. The ELM model exhibites the best performance compared with the models of MLR and SVR. OS-ELM and FOS-ELM are applied for sequential learning and model updating. The optimal number of samples in validity term of the FOS-ELM model is determined to be 1500, with the smallest population mean absolute relative error (MARE) value of 0.058226 for the population. The variable importance analysis reveals lime weight, initial P content, and hot metal weight as the most important variables for the lime utilization ratio. The lime utilization ratio increases with the decrease in lime weight and the increases in the initial P content and hot metal weight. A prediction system based on FOS-ELM is applied in actual industrial production for one month. The hit ratios of the predicted lime utilization ratio in the error ranges of ±1%, ±3%, and ±5% are 61.16%, 90.63%, and 94.11%, respectively. The coefficient of determination, MARE, and root mean square error are 0.8670, 0.06823, and 1.4265, respectively. The system exhibits desirable performance for applications in actual industrial production.
The machine learning models of multiple linear regression (MLR), support vector regression (SVR), and extreme learning machine (ELM) and the proposed ELM models of online sequential ELM (OS-ELM) and OS-ELM with forgetting mechanism (FOS-ELM) are applied in the prediction of the lime utilization ratio of dephosphorization in the basic oxygen furnace steelmaking process. The ELM model exhibites the best performance compared with the models of MLR and SVR. OS-ELM and FOS-ELM are applied for sequential learning and model updating. The optimal number of samples in validity term of the FOS-ELM model is determined to be 1500, with the smallest population mean absolute relative error (MARE) value of 0.058226 for the population. The variable importance analysis reveals lime weight, initial P content, and hot metal weight as the most important variables for the lime utilization ratio. The lime utilization ratio increases with the decrease in lime weight and the increases in the initial P content and hot metal weight. A prediction system based on FOS-ELM is applied in actual industrial production for one month. The hit ratios of the predicted lime utilization ratio in the error ranges of ±1%, ±3%, and ±5% are 61.16%, 90.63%, and 94.11%, respectively. The coefficient of determination, MARE, and root mean square error are 0.8670, 0.06823, and 1.4265, respectively. The system exhibits desirable performance for applications in actual industrial production.
, Available online 18 August 2023,
https://doi.org/10.1007/s12613-023-2729-z
Abstract:
Iron-rich electrolytic manganese residue (IREMR) is an industrial waste produced during the processing of electrolytic metal manganese, and it contains certain amounts of Fe and Mn resources and other heavy metals. In this study, the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR. The effects of IREMR and H2SO4 mass ratio, current density, reaction temperature, and electrolytic time on the leaching and current efficiencies of Fe were studied. According to the results, high-purity Fe powder can be recovered from the cathode plate, and the slurry electrolyte can be recycled. The leaching efficiency, current efficiency, and purity of Fe reached 92.58%, 80.65%, and 98.72wt%, respectively, at a 1:2.5 mass ratio of H2SO4 and IREMR, reaction temperature of 60°C, electric current density of 30 mA/cm2, and reaction time of 8 h. In addition, vibrating sample magnetometer (VSM) analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m, which reached the advanced magnetic grade of electrical pure-iron powder (DT4A coercivity standard). The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.
Iron-rich electrolytic manganese residue (IREMR) is an industrial waste produced during the processing of electrolytic metal manganese, and it contains certain amounts of Fe and Mn resources and other heavy metals. In this study, the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR. The effects of IREMR and H2SO4 mass ratio, current density, reaction temperature, and electrolytic time on the leaching and current efficiencies of Fe were studied. According to the results, high-purity Fe powder can be recovered from the cathode plate, and the slurry electrolyte can be recycled. The leaching efficiency, current efficiency, and purity of Fe reached 92.58%, 80.65%, and 98.72wt%, respectively, at a 1:2.5 mass ratio of H2SO4 and IREMR, reaction temperature of 60°C, electric current density of 30 mA/cm2, and reaction time of 8 h. In addition, vibrating sample magnetometer (VSM) analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m, which reached the advanced magnetic grade of electrical pure-iron powder (DT4A coercivity standard). The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.
, Available online 10 August 2023,
https://doi.org/10.1007/s12613-023-2720-8
Abstract:
Al is considered as a promising lithium-ion battery (LIBs) anode materials owing to its high theoretical capacity and appropriate lithation/de-lithation potential. Unfortunately, its inevitable volume expansion causes the electrode structure instability, leading to poor cyclic stability. What’s worse, the natural Al2O3 layer on commercial Al pellets is always existed as a robust insulating barrier for electrons, which brings the voltage dip and results in low reversible capacity. Herein, this work synthesized core–shell Al@C–Sn pellets for LIBs by a plus-minus strategy. In this proposal, the natural Al2O3 passivation layer is eliminated when annealing the pre-introduced SnCl2, meanwhile, polydopamine-derived carbon is introduced as dual functional shell to liberate the fresh Al core from re-oxidization and alleviate the volume swellings. Benefiting from the addition of C–Sn shell and the elimination of the Al2O3 passivation layer, the as-prepared Al@C–Sn pellet electrode exhibits little voltage dip and delivers a reversible capacity of 1018.7 mAh·g–1 at 0.1 A·g–1 and 295.0 mAh·g–1 at 2.0 A·g–1 (after 1000 cycles), respectively. Moreover, its diffusion-controlled capacity is muchly improved compared to those of its counterparts, confirming the well-designed nanostructure contributes to the rapid Li-ion diffusion and further enhances the lithium storage activity.
Al is considered as a promising lithium-ion battery (LIBs) anode materials owing to its high theoretical capacity and appropriate lithation/de-lithation potential. Unfortunately, its inevitable volume expansion causes the electrode structure instability, leading to poor cyclic stability. What’s worse, the natural Al2O3 layer on commercial Al pellets is always existed as a robust insulating barrier for electrons, which brings the voltage dip and results in low reversible capacity. Herein, this work synthesized core–shell Al@C–Sn pellets for LIBs by a plus-minus strategy. In this proposal, the natural Al2O3 passivation layer is eliminated when annealing the pre-introduced SnCl2, meanwhile, polydopamine-derived carbon is introduced as dual functional shell to liberate the fresh Al core from re-oxidization and alleviate the volume swellings. Benefiting from the addition of C–Sn shell and the elimination of the Al2O3 passivation layer, the as-prepared Al@C–Sn pellet electrode exhibits little voltage dip and delivers a reversible capacity of 1018.7 mAh·g–1 at 0.1 A·g–1 and 295.0 mAh·g–1 at 2.0 A·g–1 (after 1000 cycles), respectively. Moreover, its diffusion-controlled capacity is muchly improved compared to those of its counterparts, confirming the well-designed nanostructure contributes to the rapid Li-ion diffusion and further enhances the lithium storage activity.
, Available online 10 August 2023,
https://doi.org/10.1007/s12613-023-2717-3
Abstract:
X-ray excited photodynamic therapy (X-PDT) is the bravo answer of photodynamic therapy (PDT) for deep-seated tumors, as it employs X-ray as the irradiation source to overcome the limitation of light penetration depth. However, high X-ray irradiation dose caused organ lesions and side effects became the major barrier to X-PDT application. To address this issue, this work employed a classical co-precipitation reaction to synthesize NaLuF4:15%Tb3+ (NLF) with an average particle size of (23.48 ± 0.91) nm, which was then coupled with the photosensitizer merocyanine 540 (MC540) to form the X-PDT system NLF-MC540 with high production of singlet oxygen. The system could induce antitumor efficacy to about 24% in relative low dose X-ray irradiation range (0.1–0.3 Gy). In vivo, when NLF-MC540 irradiated by 0.1 Gy X-ray, the tumor inhibition percentage reached 89.5% ± 5.7%. The therapeutic mechanism of low dose X-PDT was found. A significant increase of neutrophils in serum was found on the third day after X-PDT. By immunohistochemical staining of tumor sections, the Ly6G+, CD8+, and CD11c+ cells infiltrated in the tumor microenvironment were studied. Utilizing the bilateral tumor model, the NLF-MC540 with 0.1 Gy X-ray irradiation could inhibit both the primary tumor and the distant tumor growth. Detected by enzyme linked immunosorbent assay (ElISA), two cytokines IFN-γ and TNF-α in serum were upregulated 7 times and 6 times than negative control, respectively. Detected by enzyme linked immune spot assay (ElISPOT), the number of immune cells attributable to the IFN-γ and TNF-α levels in the group of low dose X-PDT were 14 times and 6 times greater than that in the negative control group, respectively. Thus, it conclude that low dose X-PDT system could successfully upregulate the levels of immune cells, stimulate the secretion of cytokines (especially IFN-γ and TNF-α), activate antitumor immunity, and finally inhibit colon tumor growth.
X-ray excited photodynamic therapy (X-PDT) is the bravo answer of photodynamic therapy (PDT) for deep-seated tumors, as it employs X-ray as the irradiation source to overcome the limitation of light penetration depth. However, high X-ray irradiation dose caused organ lesions and side effects became the major barrier to X-PDT application. To address this issue, this work employed a classical co-precipitation reaction to synthesize NaLuF4:15%Tb3+ (NLF) with an average particle size of (23.48 ± 0.91) nm, which was then coupled with the photosensitizer merocyanine 540 (MC540) to form the X-PDT system NLF-MC540 with high production of singlet oxygen. The system could induce antitumor efficacy to about 24% in relative low dose X-ray irradiation range (0.1–0.3 Gy). In vivo, when NLF-MC540 irradiated by 0.1 Gy X-ray, the tumor inhibition percentage reached 89.5% ± 5.7%. The therapeutic mechanism of low dose X-PDT was found. A significant increase of neutrophils in serum was found on the third day after X-PDT. By immunohistochemical staining of tumor sections, the Ly6G+, CD8+, and CD11c+ cells infiltrated in the tumor microenvironment were studied. Utilizing the bilateral tumor model, the NLF-MC540 with 0.1 Gy X-ray irradiation could inhibit both the primary tumor and the distant tumor growth. Detected by enzyme linked immunosorbent assay (ElISA), two cytokines IFN-γ and TNF-α in serum were upregulated 7 times and 6 times than negative control, respectively. Detected by enzyme linked immune spot assay (ElISPOT), the number of immune cells attributable to the IFN-γ and TNF-α levels in the group of low dose X-PDT were 14 times and 6 times greater than that in the negative control group, respectively. Thus, it conclude that low dose X-PDT system could successfully upregulate the levels of immune cells, stimulate the secretion of cytokines (especially IFN-γ and TNF-α), activate antitumor immunity, and finally inhibit colon tumor growth.
, Available online 10 August 2023,
https://doi.org/10.1007/s12613-023-2719-1
Abstract:
High-chromium vanadium–titanium magnetite (HVTM) is a crucial polymetallic-associated resource to be developed. The all-pellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future. By referencing the production data of vanadium–titanium magnetite blast furnaces, this study explored the softening–melting behavior of high-chromium vanadium–titanium magnetite and obtained the optimal integrated burden based on flux pellets. The results show that the burden with a composition of 70wt% flux pellets and 30wt% acid pellets exhibits the best softening–melting properties. In comparison to that of the single burden, the softening–melting characteristic temperature of this burden composition was higher. The melting interval first increased from 307 to 362°C and then decreased to 282°C. The maximum pressure drop (ΔPmax) decreased from 26.76 to 19.01 kPa. The permeability index (S) dropped from 4643.5 to 2446.8 kPa·°C. The softening–melting properties of the integrated burden were apparently improved. The acid pellets played a role in withstanding load during the softening process. The flux pellets in the integrated burden exhibited a higher slag melting point, which increased the melting temperature during the melting process. The slag homogeneity and the TiC produced by over-reduction led to the gas permeability deterioration of the single burden. The segregation of the flux and acid pellets in the HVTM proportion and basicity mainly led to the better softening–melting properties of the integrated burden.
High-chromium vanadium–titanium magnetite (HVTM) is a crucial polymetallic-associated resource to be developed. The all-pellet operation is a blast furnace trend that aims to reduce carbon dioxide emissions in the future. By referencing the production data of vanadium–titanium magnetite blast furnaces, this study explored the softening–melting behavior of high-chromium vanadium–titanium magnetite and obtained the optimal integrated burden based on flux pellets. The results show that the burden with a composition of 70wt% flux pellets and 30wt% acid pellets exhibits the best softening–melting properties. In comparison to that of the single burden, the softening–melting characteristic temperature of this burden composition was higher. The melting interval first increased from 307 to 362°C and then decreased to 282°C. The maximum pressure drop (ΔPmax) decreased from 26.76 to 19.01 kPa. The permeability index (S) dropped from 4643.5 to 2446.8 kPa·°C. The softening–melting properties of the integrated burden were apparently improved. The acid pellets played a role in withstanding load during the softening process. The flux pellets in the integrated burden exhibited a higher slag melting point, which increased the melting temperature during the melting process. The slag homogeneity and the TiC produced by over-reduction led to the gas permeability deterioration of the single burden. The segregation of the flux and acid pellets in the HVTM proportion and basicity mainly led to the better softening–melting properties of the integrated burden.
, Available online 13 July 2023,
https://doi.org/10.1007/s12613-023-2704-8
Abstract:
The coagulation process is a widely applied technology in water and wastewater treatment. Novel composite polyferric magnesium–silicate–sulfate (PFMS) coagulants were synthesized using Na2SiO3·9H2O, Fe2(SO4)3, and MgSO4 as raw materials in this paper. The effects of aging time, Fe:Si:Mg, and OH:M molar ratios (M represents the metal ions) on the coagulation performance of the as-prepared PFMS were systematically investigated to obtain optimum coagulants. The results showed that PFMS coagulant exhibited good coagulation properties in the treatment of simulated humic acid–kaolin surface water and reactive dye wastewater. When the molar ratios were controlled at Fe:Si:Mg = 2:2:1 and OH:M = 0.32, the obtained PFMS presented excellent stability and a high coagulation efficiency. The removal efficiency of ultraviolet UV254 was 99.81%, and the residual turbidity of the surface water reached 0.56 NTU at a dosage of 30 mg·L–1. After standing the coagulant for 120 d in the laboratory, the removal efficiency of UV254 and residual turbidity of the surface water were 88.12% and 0.68 NTU, respectively, which accord with the surface water treatment requirements. In addition, the coagulation performance in the treatment of reactive dye wastewater was greatly improved by combining the advantages of magnesium and iron salts. Compared with polyferric silicate–sulfate (PFS) and polymagnesium silicate–sulfate (PMS), the PFMS coagulant played a better decolorization role within the pH range of 7–13.
The coagulation process is a widely applied technology in water and wastewater treatment. Novel composite polyferric magnesium–silicate–sulfate (PFMS) coagulants were synthesized using Na2SiO3·9H2O, Fe2(SO4)3, and MgSO4 as raw materials in this paper. The effects of aging time, Fe:Si:Mg, and OH:M molar ratios (M represents the metal ions) on the coagulation performance of the as-prepared PFMS were systematically investigated to obtain optimum coagulants. The results showed that PFMS coagulant exhibited good coagulation properties in the treatment of simulated humic acid–kaolin surface water and reactive dye wastewater. When the molar ratios were controlled at Fe:Si:Mg = 2:2:1 and OH:M = 0.32, the obtained PFMS presented excellent stability and a high coagulation efficiency. The removal efficiency of ultraviolet UV254 was 99.81%, and the residual turbidity of the surface water reached 0.56 NTU at a dosage of 30 mg·L–1. After standing the coagulant for 120 d in the laboratory, the removal efficiency of UV254 and residual turbidity of the surface water were 88.12% and 0.68 NTU, respectively, which accord with the surface water treatment requirements. In addition, the coagulation performance in the treatment of reactive dye wastewater was greatly improved by combining the advantages of magnesium and iron salts. Compared with polyferric silicate–sulfate (PFS) and polymagnesium silicate–sulfate (PMS), the PFMS coagulant played a better decolorization role within the pH range of 7–13.
, Available online 13 July 2023,
https://doi.org/10.1007/s12613-023-2708-4
Abstract:
Flotation separation of magnesite and its calcium-containing carbonate minerals is a difficult problem. Recently, new regulators have been proposed for magnesite flotation decalcification, although traditional adjusters such as tannin, water glass, sodium carbonate, and sodium hexametaphosphate are more widely used in industry. However, they are rarely used as the main regulators in research because they perform poorly in magnesite and dolomite single-mineral flotation tests. Inspired by the limonite pre-desilting method and the addition of a modifier to magnesite slurry mixing, we used a tannin pretreatment method for separating magnesite and dolomite. Microflotation experiments confirmed that the tannin pretreatment method selectively and largely reduces the flotation recovery rate of dolomite without affecting the flotation recovery rate of magnesite. Moreover, the contact angles of the tannin-pretreated magnesite and dolomite increased and decreased, respectively, in the presence of NaOl. Zeta potential and Fourier transform infrared analyses showed that the tannin pretreatment method efficiently hinders NaOl adsorption on the dolomite surface but does not affect NaOl adsorption on the magnesite surface. X-ray photoelectron spectroscopy and density functional theory calculations confirmed that tannin interacts more strongly with dolomite than with magnesite.
Flotation separation of magnesite and its calcium-containing carbonate minerals is a difficult problem. Recently, new regulators have been proposed for magnesite flotation decalcification, although traditional adjusters such as tannin, water glass, sodium carbonate, and sodium hexametaphosphate are more widely used in industry. However, they are rarely used as the main regulators in research because they perform poorly in magnesite and dolomite single-mineral flotation tests. Inspired by the limonite pre-desilting method and the addition of a modifier to magnesite slurry mixing, we used a tannin pretreatment method for separating magnesite and dolomite. Microflotation experiments confirmed that the tannin pretreatment method selectively and largely reduces the flotation recovery rate of dolomite without affecting the flotation recovery rate of magnesite. Moreover, the contact angles of the tannin-pretreated magnesite and dolomite increased and decreased, respectively, in the presence of NaOl. Zeta potential and Fourier transform infrared analyses showed that the tannin pretreatment method efficiently hinders NaOl adsorption on the dolomite surface but does not affect NaOl adsorption on the magnesite surface. X-ray photoelectron spectroscopy and density functional theory calculations confirmed that tannin interacts more strongly with dolomite than with magnesite.
, Available online 30 June 2023,
https://doi.org/10.1007/s12613-023-2697-3
Abstract:
Flotation separation of calcite from fluorite is a challenge on low-grade fluorite flotation that limits the recovery and purity of fluorite concentrate. A new acid leaching–flotation process for fluorite is proposed in this work. This innovative process raised the fluorite’s grade to 97.26% while producing nanoscale calcium carbonate from its leachate, which contained plenty of calcium ions. On the production of nanoscale calcium carbonate, the impacts of concentration, temperature, and titration rate were examined. By modifying the process conditions and utilizing crystal conditioning agents, calcite-type and amorphous calcium carbonates with corresponding particle sizes of 1.823 and 1.511 μm were produced. The influence of the impurity ions Mn2+, Mg2+, and Fe3+ was demonstrated to reduce the particle size of nanoscale calcium carbonate and make crystal shape easier to manage in the fluorite leach solution system compared with the calcium chloride solution. The combination of the acid leaching–flotation process and the nanoscale calcium carbonate preparation method improved the grade of fluorite while recovering calcite resources, thus presenting a novel idea for the effective and clean usage of low-quality fluorite resources with embedded microfine particles.
Flotation separation of calcite from fluorite is a challenge on low-grade fluorite flotation that limits the recovery and purity of fluorite concentrate. A new acid leaching–flotation process for fluorite is proposed in this work. This innovative process raised the fluorite’s grade to 97.26% while producing nanoscale calcium carbonate from its leachate, which contained plenty of calcium ions. On the production of nanoscale calcium carbonate, the impacts of concentration, temperature, and titration rate were examined. By modifying the process conditions and utilizing crystal conditioning agents, calcite-type and amorphous calcium carbonates with corresponding particle sizes of 1.823 and 1.511 μm were produced. The influence of the impurity ions Mn2+, Mg2+, and Fe3+ was demonstrated to reduce the particle size of nanoscale calcium carbonate and make crystal shape easier to manage in the fluorite leach solution system compared with the calcium chloride solution. The combination of the acid leaching–flotation process and the nanoscale calcium carbonate preparation method improved the grade of fluorite while recovering calcite resources, thus presenting a novel idea for the effective and clean usage of low-quality fluorite resources with embedded microfine particles.
, Available online 3 January 2024,
https://doi.org/10.1007/s12613-024-2822-y
Abstract:
Structural instability in underground engineering, especially in coal–rock structures, poses significant safety risks. Thus, the development of an accurate monitoring method for the health of coal–rock bodies is crucial. The focus of this work is on understanding energy evolution patterns in coal–rock bodies under complex conditions by using shear, splitting, and uniaxial compression tests. We examine the changes in energy parameters during various loading stages and the effects of various failure modes, resulting in an innovative energy dissipation-based health evaluation technique for coal. Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading, indicated by fluctuations in elastic energy and dissipation energy density. For tensile failure, the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress. On the other hand, shear failure is described by “high accumulation and low dissipation” in energy trends. Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization, and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples. A novel mathematical and statistical approach is developed, establishing a dissipation energy anomaly index, W, which categorizes the structural health of coal into different danger levels. This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments, contributing to the development of structural health monitoring technology.
Structural instability in underground engineering, especially in coal–rock structures, poses significant safety risks. Thus, the development of an accurate monitoring method for the health of coal–rock bodies is crucial. The focus of this work is on understanding energy evolution patterns in coal–rock bodies under complex conditions by using shear, splitting, and uniaxial compression tests. We examine the changes in energy parameters during various loading stages and the effects of various failure modes, resulting in an innovative energy dissipation-based health evaluation technique for coal. Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading, indicated by fluctuations in elastic energy and dissipation energy density. For tensile failure, the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress. On the other hand, shear failure is described by “high accumulation and low dissipation” in energy trends. Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization, and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples. A novel mathematical and statistical approach is developed, establishing a dissipation energy anomaly index, W, which categorizes the structural health of coal into different danger levels. This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments, contributing to the development of structural health monitoring technology.
, Available online 29 December 2023,
https://doi.org/10.1007/s12613-023-2821-4
Abstract:
This study introduces a coupled electromagnetic–thermal–mechanical model to reveal the mechanisms of microcracking and mineral melting of polymineralic rocks under microwave radiation. Experimental tests validate the rationality of the proposed model. Embedding microscopic mineral sections into the granite model for simulation shows that uneven temperature gradients create distinct molten, porous, and nonmolten zones on the fracture surface. Moreover, the varying thermal expansion coefficients and Young’s moduli among the minerals induce significant thermal stress at the mineral boundaries. Quartz and biotite with higher thermal expansion coefficients are subjected to compression, whereas plagioclase with smaller coefficients experiences tensile stress. In the molten zone, quartz undergoes transgranular cracking due to the α–β phase transition. The local high temperatures also induce melting phase transitions in biotite and feldspar. This numerical study provides new insights into the distribution of thermal stress and mineral phase changes in rocks under microwave irradiation.
This study introduces a coupled electromagnetic–thermal–mechanical model to reveal the mechanisms of microcracking and mineral melting of polymineralic rocks under microwave radiation. Experimental tests validate the rationality of the proposed model. Embedding microscopic mineral sections into the granite model for simulation shows that uneven temperature gradients create distinct molten, porous, and nonmolten zones on the fracture surface. Moreover, the varying thermal expansion coefficients and Young’s moduli among the minerals induce significant thermal stress at the mineral boundaries. Quartz and biotite with higher thermal expansion coefficients are subjected to compression, whereas plagioclase with smaller coefficients experiences tensile stress. In the molten zone, quartz undergoes transgranular cracking due to the α–β phase transition. The local high temperatures also induce melting phase transitions in biotite and feldspar. This numerical study provides new insights into the distribution of thermal stress and mineral phase changes in rocks under microwave irradiation.
, Available online 15 December 2023,
https://doi.org/10.1007/s12613-023-2812-5
Abstract:
The basal texture of traditional magnesium alloy AZ31 is easy to form and exhibits poor plasticity at room temperature. To address these problems, a multi-micro-alloyed high-plasticity Mg–1.8Zn–0.8Gd–0.1Ca–0.2Mn (wt%) alloy was developed using the unique role of rare earth and Ca solute atoms. In addition, the influence of the annealing process on the grain size, second phase, texture, and mechanical properties of the warm-rolled sheet at room temperature was analyzed with the goal of developing high-plasticity magnesium alloy sheets and obtaining optimal thermal-mechanical treatment parameters. The results show that the annealing temperature has a significant effect on the microstructure and properties due to the low alloying content: there are small amounts of larger-sized block and long string phases along the rolling direction, as well as several spherical and rodlike particle phases inside the grains. With increasing annealing temperature, the grain size decreases and then increases, and the morphology, number, and size of the second phase also change correspondingly. The particle phase within the grains vanishes at 450°C, and the grain size increases sharply. In the full recrystallization stage at 300–350°C, the optimum strength–plasticity comprehensive mechanical properties are presented, with yield strengths of 182.1 and 176.9 MPa, tensile strengths of 271.1 and 275.8 MPa in the RD and TD, and elongation values of 27.4% and 32.3%, respectively. Moreover, there are still some larger-sized phases in the alloy that influence its mechanical properties, which offers room for improvement.
The basal texture of traditional magnesium alloy AZ31 is easy to form and exhibits poor plasticity at room temperature. To address these problems, a multi-micro-alloyed high-plasticity Mg–1.8Zn–0.8Gd–0.1Ca–0.2Mn (wt%) alloy was developed using the unique role of rare earth and Ca solute atoms. In addition, the influence of the annealing process on the grain size, second phase, texture, and mechanical properties of the warm-rolled sheet at room temperature was analyzed with the goal of developing high-plasticity magnesium alloy sheets and obtaining optimal thermal-mechanical treatment parameters. The results show that the annealing temperature has a significant effect on the microstructure and properties due to the low alloying content: there are small amounts of larger-sized block and long string phases along the rolling direction, as well as several spherical and rodlike particle phases inside the grains. With increasing annealing temperature, the grain size decreases and then increases, and the morphology, number, and size of the second phase also change correspondingly. The particle phase within the grains vanishes at 450°C, and the grain size increases sharply. In the full recrystallization stage at 300–350°C, the optimum strength–plasticity comprehensive mechanical properties are presented, with yield strengths of 182.1 and 176.9 MPa, tensile strengths of 271.1 and 275.8 MPa in the RD and TD, and elongation values of 27.4% and 32.3%, respectively. Moreover, there are still some larger-sized phases in the alloy that influence its mechanical properties, which offers room for improvement.