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2024, vol. 31, no. 11, pp.
2327-2344.
https://doi.org/10.1007/s12613-024-2891-y
Abstract:
For the rational manipulation of the production quality of high-temperature metallurgical engineering, there are many challenges in understanding the processes involved because of the black box chemical/electrochemical reactors. To overcome this issue, various in-situ characterization methods have been recently developed to analyze the interactions between the composition, microstructure, and solid–liquid interface of high-temperature electrochemical electrodes and molten salts. In this review, recent progress of in-situ high-temperature characterization techniques is discussed to summarize the advances in understanding the processes in metallurgical engineering. In-situ high-temperature technologies and analytical methods mainly include synchrotron X-ray diffraction (s-XRD), laser scanning confocal microscopy, and X-ray computed microtomography (X-ray µ-CT), which are important platforms for analyzing the structure and morphology of the electrodes to reveal the complexity and variability of their interfaces. In addition, laser-induced breakdown spectroscopy, high-temperature Raman spectroscopy, and ultraviolet–visible absorption spectroscopy provide microscale characterizations of the composition and structure of molten salts. More importantly, the combination of X-ray µ-CT and s-XRD techniques enables the investigation of the chemical reaction mechanisms at the two-phase interface. Therefore, these in-situ methods are essential for analyzing the chemical/electrochemical kinetics of high-temperature reaction processes and establishing the theoretical principles for the efficient and stable operation of chemical/electrochemical metallurgical processes.
For the rational manipulation of the production quality of high-temperature metallurgical engineering, there are many challenges in understanding the processes involved because of the black box chemical/electrochemical reactors. To overcome this issue, various in-situ characterization methods have been recently developed to analyze the interactions between the composition, microstructure, and solid–liquid interface of high-temperature electrochemical electrodes and molten salts. In this review, recent progress of in-situ high-temperature characterization techniques is discussed to summarize the advances in understanding the processes in metallurgical engineering. In-situ high-temperature technologies and analytical methods mainly include synchrotron X-ray diffraction (s-XRD), laser scanning confocal microscopy, and X-ray computed microtomography (X-ray µ-CT), which are important platforms for analyzing the structure and morphology of the electrodes to reveal the complexity and variability of their interfaces. In addition, laser-induced breakdown spectroscopy, high-temperature Raman spectroscopy, and ultraviolet–visible absorption spectroscopy provide microscale characterizations of the composition and structure of molten salts. More importantly, the combination of X-ray µ-CT and s-XRD techniques enables the investigation of the chemical reaction mechanisms at the two-phase interface. Therefore, these in-situ methods are essential for analyzing the chemical/electrochemical kinetics of high-temperature reaction processes and establishing the theoretical principles for the efficient and stable operation of chemical/electrochemical metallurgical processes.
ReviewOpen Access
2024, vol. 31, no. 11, pp.
2345-2367.
https://doi.org/10.1007/s12613-024-2948-y
Abstract:
Undoubtedly, the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery (LIB) technology. The achieved improvements in the energy density, cyclability, charging speed, reduced costs, as well as safety and stability, already contribute to the wider adoption of LIBs, which extends nowadays beyond mobile electronics, power tools, and electric vehicles, to the new range of applications, including grid storage solutions. With numerous published papers and broad reviews already available on the subject of Ni-rich oxides, this review focuses more on the most recent progress and new ideas presented in the literature references. The covered topics include doping and composition optimization, advanced coating, concentration gradient and single crystal materials, as well as innovations concerning new electrolytes and their modification, with the application of Ni-rich cathodes in solid-state batteries also discussed. Related cathode materials are briefly mentioned, with the high-entropy approach and zero-strain concept presented as well. A critical overview of the still unresolved issues is given, with perspectives on the further directions of studies and the expected gains provided.
Undoubtedly, the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery (LIB) technology. The achieved improvements in the energy density, cyclability, charging speed, reduced costs, as well as safety and stability, already contribute to the wider adoption of LIBs, which extends nowadays beyond mobile electronics, power tools, and electric vehicles, to the new range of applications, including grid storage solutions. With numerous published papers and broad reviews already available on the subject of Ni-rich oxides, this review focuses more on the most recent progress and new ideas presented in the literature references. The covered topics include doping and composition optimization, advanced coating, concentration gradient and single crystal materials, as well as innovations concerning new electrolytes and their modification, with the application of Ni-rich cathodes in solid-state batteries also discussed. Related cathode materials are briefly mentioned, with the high-entropy approach and zero-strain concept presented as well. A critical overview of the still unresolved issues is given, with perspectives on the further directions of studies and the expected gains provided.
2024, vol. 31, no. 11, pp.
2368-2389.
https://doi.org/10.1007/s12613-024-2924-6
Abstract:
The photocatalytic activity of catalysts depends on the energy-harvesting ability and the separation or transport of photogenerated carriers. The light absorption capacity of graphitic carbon nitride (g-C3N4)-based composites can be enhanced by adjusting the surface plasmon resonance (SPR) of noble metal nanoparticles (e.g., Cu, Au, and Pd) in the entire visible region. Adjustments can be carried out by varying the nanocomponents of the materials. The SPR of noble metals can enhance the local electromagnetic field and improve interband transition, and resonant energy transfer occurs from plasmonic dipoles to electron–hole pairs via near-field electromagnetic interactions. Thus, noble metals have emerged as relevant nanocomponents for g-C3N4 used in CO2 photoreduction and water splitting. Herein, recent key advances in noble metals (either in single atom, cluster, or nanoparticle forms) and composite photocatalysts based on inorganic or organic nanocomponent-incorporated g-C3N4 nanosheets are systematically discussed, including the applications of these photocatalysts, which exhibit improved photoinduced charge mobility in CO2 photoconversion and H2 production. Issues related to the different types of multi-nanocomponent heterostructures (involving Schottky junctions, Z-/S-scheme heterostructures, noble metals, and additional semiconductor nanocomponents) and the adjustment of dimensionality of heterostructures (by incorporating noble metal nanoplates on g-C3N4 forming 2D/2D heterostructures) are explored. The current prospects and possible challenges of g-C3N4 composite photocatalysts incorporated with noble metals (e.g., Au, Pt, Pd, and Cu), particularly in water splitting, CO2 reduction, pollution degradation, and chemical conversion applications, are summarized.
The photocatalytic activity of catalysts depends on the energy-harvesting ability and the separation or transport of photogenerated carriers. The light absorption capacity of graphitic carbon nitride (g-C3N4)-based composites can be enhanced by adjusting the surface plasmon resonance (SPR) of noble metal nanoparticles (e.g., Cu, Au, and Pd) in the entire visible region. Adjustments can be carried out by varying the nanocomponents of the materials. The SPR of noble metals can enhance the local electromagnetic field and improve interband transition, and resonant energy transfer occurs from plasmonic dipoles to electron–hole pairs via near-field electromagnetic interactions. Thus, noble metals have emerged as relevant nanocomponents for g-C3N4 used in CO2 photoreduction and water splitting. Herein, recent key advances in noble metals (either in single atom, cluster, or nanoparticle forms) and composite photocatalysts based on inorganic or organic nanocomponent-incorporated g-C3N4 nanosheets are systematically discussed, including the applications of these photocatalysts, which exhibit improved photoinduced charge mobility in CO2 photoconversion and H2 production. Issues related to the different types of multi-nanocomponent heterostructures (involving Schottky junctions, Z-/S-scheme heterostructures, noble metals, and additional semiconductor nanocomponents) and the adjustment of dimensionality of heterostructures (by incorporating noble metal nanoplates on g-C3N4 forming 2D/2D heterostructures) are explored. The current prospects and possible challenges of g-C3N4 composite photocatalysts incorporated with noble metals (e.g., Au, Pt, Pd, and Cu), particularly in water splitting, CO2 reduction, pollution degradation, and chemical conversion applications, are summarized.
2024, vol. 31, no. 11, pp.
2390-2403.
https://doi.org/10.1007/s12613-024-2985-6
Abstract:
Cemented tailings backfill (CTB) not only boosts mining safety and cuts surface environmental pollution but also recovers ores previously retained as pillars, thereby improving resource utilization. The use of alternative reinforcing products, such as steel fiber (SF), has continuously strengthened CTB into SFCTB. This approach prevents strength decreases over time and reinforces its long-term durability, especially when mining ore in adjacent underground stopes. In this study, various microstructure and strength tests were performed on SFCTB, considering steel fiber ratio and electromagnetic induction strength effects. Lab findings show that combining steel fibers and their distribution dominantly influences the improvement of the fill’s strength. Fill’s strength rises by fiber insertion and has an evident correlation with fiber insertion and magnetic induction strength. When magnetic induction strength is 3 × 10−4 T, peak uniaxial compressive stress reaches 5.73 MPa for a fiber ratio of 2.0vol%. The cracks’ expansion mainly started from the specimen’s upper part, which steadily expanded downward by increasing the load until damage occurred. The doping of steel fiber and its directional distribution delayed crack development. When the doping of steel fiber was 2.0vol%, SFCTBs showed excellent ductility characteristics. The energy required for fills to reach destruction increases when steel-fiber insertion and magnetic induction strength increase. This study provides notional references for steel fibers as underground filling additives to enhance the fill’s durability in the course of mining operations.
Cemented tailings backfill (CTB) not only boosts mining safety and cuts surface environmental pollution but also recovers ores previously retained as pillars, thereby improving resource utilization. The use of alternative reinforcing products, such as steel fiber (SF), has continuously strengthened CTB into SFCTB. This approach prevents strength decreases over time and reinforces its long-term durability, especially when mining ore in adjacent underground stopes. In this study, various microstructure and strength tests were performed on SFCTB, considering steel fiber ratio and electromagnetic induction strength effects. Lab findings show that combining steel fibers and their distribution dominantly influences the improvement of the fill’s strength. Fill’s strength rises by fiber insertion and has an evident correlation with fiber insertion and magnetic induction strength. When magnetic induction strength is 3 × 10−4 T, peak uniaxial compressive stress reaches 5.73 MPa for a fiber ratio of 2.0vol%. The cracks’ expansion mainly started from the specimen’s upper part, which steadily expanded downward by increasing the load until damage occurred. The doping of steel fiber and its directional distribution delayed crack development. When the doping of steel fiber was 2.0vol%, SFCTBs showed excellent ductility characteristics. The energy required for fills to reach destruction increases when steel-fiber insertion and magnetic induction strength increase. This study provides notional references for steel fibers as underground filling additives to enhance the fill’s durability in the course of mining operations.
2024, vol. 31, no. 11, pp.
2404-2416.
https://doi.org/10.1007/s12613-024-2885-9
Abstract:
Using aeolian sand (AS) for goaf backfilling allows coordination of green mining and AS control. Cemented AS backfill (CASB) exhibits brittle fracture. Polypropylene (PP) fibers are good toughening materials. When the toughening effect of fibers is analyzed, their influence on the slurry conveying performance should also be considered. Additionally, cement affects the interactions among the hydration products, fibers, and aggregates. In this study, the effects of cement content (8wt%, 9wt%, and 10wt%) and PP fiber length (6, 9, and 12 mm) and dosage (0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, and 0.25wt%) on fluidity and mechanical properties of the fiber-toughened CASB (FCASB) were analyzed. The results indicated that with increases in the three aforementioned factors, the slump flow decreased, while the rheological parameters increased. Uniaxial compressive strength (UCS) increased with the increase of cement content and fiber length, and with an increase in fiber dosage, it first increased and then decreased. The strain increased with the increase of fiber dosage and length. The effect of PP fibers became more pronounced with the increase of cement content. Digital image correlation (DIC) test results showed that the addition of fibers can restrain the peeling of blocks and the expansion of fissure, and reduce the stress concentration of the FCASB. Scanning electron microscopy (SEM) test indicated that the functional mechanisms of fibers mainly involved the interactions of fibers with the hydration products and matrix and the spatial distribution of fibers. On the basis of single-factor analysis, the response surface method (RSM) was used to analyze the effects of the three aforementioned factors and their interaction terms on the UCS. The influence surface of the two-factor interaction terms and the three-dimensional scatter plot of the three-factor coupling were established. In conclusion, the response law of the FCASB properties under the effects of cement and PP fibers were obtained, which provides theoretical and engineering guidance for FCASB filling.
Using aeolian sand (AS) for goaf backfilling allows coordination of green mining and AS control. Cemented AS backfill (CASB) exhibits brittle fracture. Polypropylene (PP) fibers are good toughening materials. When the toughening effect of fibers is analyzed, their influence on the slurry conveying performance should also be considered. Additionally, cement affects the interactions among the hydration products, fibers, and aggregates. In this study, the effects of cement content (8wt%, 9wt%, and 10wt%) and PP fiber length (6, 9, and 12 mm) and dosage (0.05wt%, 0.1wt%, 0.15wt%, 0.2wt%, and 0.25wt%) on fluidity and mechanical properties of the fiber-toughened CASB (FCASB) were analyzed. The results indicated that with increases in the three aforementioned factors, the slump flow decreased, while the rheological parameters increased. Uniaxial compressive strength (UCS) increased with the increase of cement content and fiber length, and with an increase in fiber dosage, it first increased and then decreased. The strain increased with the increase of fiber dosage and length. The effect of PP fibers became more pronounced with the increase of cement content. Digital image correlation (DIC) test results showed that the addition of fibers can restrain the peeling of blocks and the expansion of fissure, and reduce the stress concentration of the FCASB. Scanning electron microscopy (SEM) test indicated that the functional mechanisms of fibers mainly involved the interactions of fibers with the hydration products and matrix and the spatial distribution of fibers. On the basis of single-factor analysis, the response surface method (RSM) was used to analyze the effects of the three aforementioned factors and their interaction terms on the UCS. The influence surface of the two-factor interaction terms and the three-dimensional scatter plot of the three-factor coupling were established. In conclusion, the response law of the FCASB properties under the effects of cement and PP fibers were obtained, which provides theoretical and engineering guidance for FCASB filling.
2024, vol. 31, no. 11, pp.
2417-2434.
https://doi.org/10.1007/s12613-024-2893-9
Abstract:
This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading. Cubic layered samples with dimensions of 100 mm × 100 mm × 100 mm were casted using rock-like materials, with anisotropic angle (α) and joint roughness coefficient (JRC) ranging from 15° to 75° and 2–20, respectively. The direct shear tests were conducted under the application of initial normal stress (σn) ranging from 1–4 MPa. The test results indicate significant differences in mechanical properties, acoustic emission (AE) responses, maximum principal strain fields, and ultimate failure modes of layered samples under different test conditions. The peak stress increases with the increasing α and achieves a maximum value at α = 60° or 75°. As σn increases, the peak stress shows an increasing trend, with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting. As JRC increases from 2–4 to 18–20, the cohesion increases by 86.32% when α = 15°, while the cohesion decreases by 27.93% when α = 75°. The differences in roughness characteristics of shear failure surface induced by α result in anisotropic post-peak AE responses, which is characterized by active AE signals when α is small and quiet AE signals for a large α. For a given JRC = 6–8 and σn = 1 MPa, as α increases, the accumulative AE counts increase by 224.31% (α increased from 15° to 60°), and then decrease by 14.68% (α increased from 60° to 75°). The shear failure surface is formed along the weak interlayer when α = 15° and penetrates the layered matrix when α = 60°. When α = 15°, as σn increases, the adjacent weak interlayer induces a change in the direction of tensile cracks propagation, resulting in a stepped pattern of cracks distribution. The increase in JRC intensifies roughness characteristics of shear failure surface for a small α, however, it is not pronounced for a large α. The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.
This study aims to investigate mechanical properties and failure mechanisms of layered rock with rough joint surfaces under direct shear loading. Cubic layered samples with dimensions of 100 mm × 100 mm × 100 mm were casted using rock-like materials, with anisotropic angle (α) and joint roughness coefficient (JRC) ranging from 15° to 75° and 2–20, respectively. The direct shear tests were conducted under the application of initial normal stress (σn) ranging from 1–4 MPa. The test results indicate significant differences in mechanical properties, acoustic emission (AE) responses, maximum principal strain fields, and ultimate failure modes of layered samples under different test conditions. The peak stress increases with the increasing α and achieves a maximum value at α = 60° or 75°. As σn increases, the peak stress shows an increasing trend, with correlation coefficients R² ranging from 0.918 to 0.995 for the linear least squares fitting. As JRC increases from 2–4 to 18–20, the cohesion increases by 86.32% when α = 15°, while the cohesion decreases by 27.93% when α = 75°. The differences in roughness characteristics of shear failure surface induced by α result in anisotropic post-peak AE responses, which is characterized by active AE signals when α is small and quiet AE signals for a large α. For a given JRC = 6–8 and σn = 1 MPa, as α increases, the accumulative AE counts increase by 224.31% (α increased from 15° to 60°), and then decrease by 14.68% (α increased from 60° to 75°). The shear failure surface is formed along the weak interlayer when α = 15° and penetrates the layered matrix when α = 60°. When α = 15°, as σn increases, the adjacent weak interlayer induces a change in the direction of tensile cracks propagation, resulting in a stepped pattern of cracks distribution. The increase in JRC intensifies roughness characteristics of shear failure surface for a small α, however, it is not pronounced for a large α. The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the layered rocks subjected to shear loads.
2024, vol. 31, no. 11, pp.
2435-2444.
https://doi.org/10.1007/s12613-024-2951-3
Abstract:
Flotation is the most common method to obtain concentrate through the selective adsorption of collectors on target minerals to make them hydrophobic and floatable. In the hydrometallurgy of concentrate, collectors adsorbed on concentrate can damage ion-exchange resin and increase the chemical oxygen demand (COD) value of wastewater. In this work, we proposed a new scheme, i.e., desorbing the collectors from concentrate in ore dressing plant and reusing them in flotation flowsheet. Lead nitrate and benzohydroxamic acid (Pb-BHA) complex is a common collector in scheelite flotation. In this study, different physical (stirring or ultrasonic waves) and chemical (strong acid or alkali environment) methods for facilitating the desorption of Pb-BHA collector from scheelite concentrate were explored. Single-mineral desorption tests showed that under the condition of pulp pH 13 and ultrasonic treatment for 15 min, the highest desorption rates of Pb and BHA from the scheelite concentrate were 90.48% and 63.75%, respectively. Run-of-mine ore flotation tests revealed that the reuse of desorbed Pb and BHA reduced the collector dosage by 30% for BHA and 25% for Pb. The strong alkali environment broke the chemical bonds between Pb and BHA. The cavitation effect of ultrasonic waves effectively reduced the interaction intensity between Pb-BHA collector and scheelite surfaces. This method combining ultrasonic waves and strong alkali environment can effectively desorb the collectors from concentrate and provide “clean” scheelite concentrate for metallurgic plants; the reuse of desorbed collector in flotation flowsheet can reduce reagent cost for ore dressing plants.
Flotation is the most common method to obtain concentrate through the selective adsorption of collectors on target minerals to make them hydrophobic and floatable. In the hydrometallurgy of concentrate, collectors adsorbed on concentrate can damage ion-exchange resin and increase the chemical oxygen demand (COD) value of wastewater. In this work, we proposed a new scheme, i.e., desorbing the collectors from concentrate in ore dressing plant and reusing them in flotation flowsheet. Lead nitrate and benzohydroxamic acid (Pb-BHA) complex is a common collector in scheelite flotation. In this study, different physical (stirring or ultrasonic waves) and chemical (strong acid or alkali environment) methods for facilitating the desorption of Pb-BHA collector from scheelite concentrate were explored. Single-mineral desorption tests showed that under the condition of pulp pH 13 and ultrasonic treatment for 15 min, the highest desorption rates of Pb and BHA from the scheelite concentrate were 90.48% and 63.75%, respectively. Run-of-mine ore flotation tests revealed that the reuse of desorbed Pb and BHA reduced the collector dosage by 30% for BHA and 25% for Pb. The strong alkali environment broke the chemical bonds between Pb and BHA. The cavitation effect of ultrasonic waves effectively reduced the interaction intensity between Pb-BHA collector and scheelite surfaces. This method combining ultrasonic waves and strong alkali environment can effectively desorb the collectors from concentrate and provide “clean” scheelite concentrate for metallurgic plants; the reuse of desorbed collector in flotation flowsheet can reduce reagent cost for ore dressing plants.
2024, vol. 31, no. 11, pp.
2445-2457.
https://doi.org/10.1007/s12613-023-2819-y
Abstract:
Pyrolusite comprises the foremost manganese oxides and is a major source of manganese production. An innovative hydrogen-based mineral phase transformation technology to pyrolusite was proposed, where a 96.44% distribution rate of divalent manganese (Mn2+) was observed at an optimal roasting temperature of 650°C, a roasting time of 25 min, and an H2 concentration of 20vol%; under these conditions. The manganese predominantly existed in the form of manganosite. This study investigated the generation mechanism of manganosite based on the reduction kinetics, phase transformation, and structural evolution of pyrolusite and revealed that high temperature improved the distribution rate, and the optimal kinetic model for the reaction was the random nucleation and growth model (reaction order, n = 3/2) with an activation energy (Ea) of 24.119 kJ·mol−1. Throughout the mineral phase transformation, manganese oxide from the outer layer of particles moves inward to the core. In addition, pyrolusite follows the reduction sequence of MnO2 → Mn2O3 → Mn3O4 → MnO, and the reduction of manganese oxides in each valence state simultaneously proceeds. These findings provide significant insight into the efficient and clean utilization of pyrolusite.
Pyrolusite comprises the foremost manganese oxides and is a major source of manganese production. An innovative hydrogen-based mineral phase transformation technology to pyrolusite was proposed, where a 96.44% distribution rate of divalent manganese (Mn2+) was observed at an optimal roasting temperature of 650°C, a roasting time of 25 min, and an H2 concentration of 20vol%; under these conditions. The manganese predominantly existed in the form of manganosite. This study investigated the generation mechanism of manganosite based on the reduction kinetics, phase transformation, and structural evolution of pyrolusite and revealed that high temperature improved the distribution rate, and the optimal kinetic model for the reaction was the random nucleation and growth model (reaction order, n = 3/2) with an activation energy (Ea) of 24.119 kJ·mol−1. Throughout the mineral phase transformation, manganese oxide from the outer layer of particles moves inward to the core. In addition, pyrolusite follows the reduction sequence of MnO2 → Mn2O3 → Mn3O4 → MnO, and the reduction of manganese oxides in each valence state simultaneously proceeds. These findings provide significant insight into the efficient and clean utilization of pyrolusite.
2024, vol. 31, no. 11, pp.
2458-2465.
https://doi.org/10.1007/s12613-024-2904-x
Abstract:
The direct reduction process is an important development direction of low-carbon ironmaking and efficient comprehensive utilization of poly-metallic iron ore, such as titanomagnetite. However, the defluidization of reduced iron particles with a high metallization degree at a high temperature will seriously affect the operation of fluidized bed reduction. Coupling the pre-oxidation enhancing reduction and the particle surface modification of titanomagnetite, the behavior and mechanism of pre-oxidation improvement on fluidization in the fluidized bed reduction of titanomagnetite are systematically studied in this paper. Pre-oxidation treatment of titanomagnetite can significantly lower the critical stable reduction fluidization gas velocity to 0.17 m/s, which is reduced by 56% compared to that of titanomagnetite reduction without pre-oxidation, while achieving a metallization degree of >90%, Corresponding to the different reduction fluidization behaviors, three pre-oxidation operation regions have been divided, taking oxidation degrees of 26% and 86% as the boundaries. Focusing on the particle surface morphology evolution in the pre-oxidation–reduction process, the relationship between the surface morphology of pre-oxidized ore and the reduced iron with fluidization properties is built. The improving method of pre-oxidation on the reduction fluidization provides a novel approach to prevent defluidization by particle surface modification, especially for the fluidized bed reduction of poly-metallic iron ore.
The direct reduction process is an important development direction of low-carbon ironmaking and efficient comprehensive utilization of poly-metallic iron ore, such as titanomagnetite. However, the defluidization of reduced iron particles with a high metallization degree at a high temperature will seriously affect the operation of fluidized bed reduction. Coupling the pre-oxidation enhancing reduction and the particle surface modification of titanomagnetite, the behavior and mechanism of pre-oxidation improvement on fluidization in the fluidized bed reduction of titanomagnetite are systematically studied in this paper. Pre-oxidation treatment of titanomagnetite can significantly lower the critical stable reduction fluidization gas velocity to 0.17 m/s, which is reduced by 56% compared to that of titanomagnetite reduction without pre-oxidation, while achieving a metallization degree of >90%, Corresponding to the different reduction fluidization behaviors, three pre-oxidation operation regions have been divided, taking oxidation degrees of 26% and 86% as the boundaries. Focusing on the particle surface morphology evolution in the pre-oxidation–reduction process, the relationship between the surface morphology of pre-oxidized ore and the reduced iron with fluidization properties is built. The improving method of pre-oxidation on the reduction fluidization provides a novel approach to prevent defluidization by particle surface modification, especially for the fluidized bed reduction of poly-metallic iron ore.
2024, vol. 31, no. 11, pp.
2466-2475.
https://doi.org/10.1007/s12613-024-2866-z
Abstract:
Graphitized spent carbon cathode (SCC) is a hazardous solid waste generated in the aluminum electrolysis process. In this study, a flotation–acid leaching process is proposed for the purification of graphitized SCC, and the use of the purified SCC as an anode material for lithium-ion batteries is explored. The flotation and acid leaching processes were separately optimized through one-way experiments. The maximum SCC carbon content (93wt%) was achieved at a 90% proportion of −200-mesh flotation particle size, a slurry concentration of 10wt%, a rotation speed of 1600 r/min, and an inflatable capacity of 0.2 m3/h (referred to as FSCC). In the subsequent acid leaching process, the SCC carbon content reached 99.58wt% at a leaching concentration of 5 mol/L, a leaching time of 100 min, a leaching temperature of 85°C, and an HCl/FSCC volume ratio of 5:1. The purified graphitized SCC (referred to as FSCC-CL) was utilized as an anode material, and it exhibited an initial capacity of 348.2 mAh/g at 0.1 C and a reversible capacity of 347.8 mAh/g after 100 cycles. Moreover, compared with commercial graphite, FSCC-CL exhibited better reversibility and cycle stability. Thus, purified SCC is an important candidate for anode material, and the flotation–acid leaching purification method is suitable for the resourceful recycling of SCC.
Graphitized spent carbon cathode (SCC) is a hazardous solid waste generated in the aluminum electrolysis process. In this study, a flotation–acid leaching process is proposed for the purification of graphitized SCC, and the use of the purified SCC as an anode material for lithium-ion batteries is explored. The flotation and acid leaching processes were separately optimized through one-way experiments. The maximum SCC carbon content (93wt%) was achieved at a 90% proportion of −200-mesh flotation particle size, a slurry concentration of 10wt%, a rotation speed of 1600 r/min, and an inflatable capacity of 0.2 m3/h (referred to as FSCC). In the subsequent acid leaching process, the SCC carbon content reached 99.58wt% at a leaching concentration of 5 mol/L, a leaching time of 100 min, a leaching temperature of 85°C, and an HCl/FSCC volume ratio of 5:1. The purified graphitized SCC (referred to as FSCC-CL) was utilized as an anode material, and it exhibited an initial capacity of 348.2 mAh/g at 0.1 C and a reversible capacity of 347.8 mAh/g after 100 cycles. Moreover, compared with commercial graphite, FSCC-CL exhibited better reversibility and cycle stability. Thus, purified SCC is an important candidate for anode material, and the flotation–acid leaching purification method is suitable for the resourceful recycling of SCC.
2024, vol. 31, no. 11, pp.
2476-2487.
https://doi.org/10.1007/s12613-024-2947-z
Abstract:
Laser powder bed fusion (LPBF) is a widely recognized additive manufacturing technology that can fabricate complex components rapidly through layer-by-layer formation. However, there is a paucity of research on the effect of laser scanning speed on the cellular microstructure and mechanical properties of martensitic stainless steel. This study systematically investigated the influence of laser scanning speed on the cellular microstructure and mechanical properties of a developed Fe11Cr8Ni5Co3Mo martensitic stainless steel produced by LPBF. The results show that increasing the laser scanning speed from 400 to 1000 mm/s does not lead to a noticeable change in the phase fraction, but it reduces the average size of the cellular microstructure from 0.60 to 0.35 μm. The scanning speeds of 400 and 1000 mm/s both had adverse effects on performances of sample, resulting in inadequate fusion and keyhole defects respectively. The optimal scanning speed for fabricating samples was determined to be 800 mm/s, which obtained the highest room temperature tensile strength and elongation, with the ultimate tensile strength measured at (1088.3 ± 2.0) MPa and the elongation of (16.76 ± 0.10)%. Furthermore, the mechanism of the evolution of surface morphology, defects, and energy input were clarified, and the relationship between cellular microstructure size and mechanical properties was also established.
Laser powder bed fusion (LPBF) is a widely recognized additive manufacturing technology that can fabricate complex components rapidly through layer-by-layer formation. However, there is a paucity of research on the effect of laser scanning speed on the cellular microstructure and mechanical properties of martensitic stainless steel. This study systematically investigated the influence of laser scanning speed on the cellular microstructure and mechanical properties of a developed Fe11Cr8Ni5Co3Mo martensitic stainless steel produced by LPBF. The results show that increasing the laser scanning speed from 400 to 1000 mm/s does not lead to a noticeable change in the phase fraction, but it reduces the average size of the cellular microstructure from 0.60 to 0.35 μm. The scanning speeds of 400 and 1000 mm/s both had adverse effects on performances of sample, resulting in inadequate fusion and keyhole defects respectively. The optimal scanning speed for fabricating samples was determined to be 800 mm/s, which obtained the highest room temperature tensile strength and elongation, with the ultimate tensile strength measured at (1088.3 ± 2.0) MPa and the elongation of (16.76 ± 0.10)%. Furthermore, the mechanism of the evolution of surface morphology, defects, and energy input were clarified, and the relationship between cellular microstructure size and mechanical properties was also established.
2024, vol. 31, no. 11, pp.
2488-2497.
https://doi.org/10.1007/s12613-024-2932-6
Abstract:
To enhance the microbiologically influenced corrosion (MIC) resistance of FeCoNiCrMn high entropy alloy (HEAs), a series of FexCu(1−x)CoNiCrMn (x = 1, 0.75, 0.5, and 0.25) HEAs were prepared. Microstructural characteristics, corrosion behavior (morphology observation and electrochemical properties), and antimicrobial performance of FexCu(1−x)CoNiCrMn HEAs were evaluated in a medium inoculated with typical corrosive microorganism Pseudomonas aeruginosa. The aim was to identify copper-containing FeCoNiCrMn HEAs that balance corrosion resistance and antimicrobial properties. Results revealed that all FexCu(1−x)CoNiCrMn (x = 1, 0.75, 0.5, and 0.25) HEAs exhibited an FCC (face centered cubic) phase, with significant grain refinement observed in Fe0.75Cu0.25CoNiCrMn HEA. Electrochemical tests indicated that Fe0.75Cu0.25CoNiCrMn HEA demonstrated lower corrosion current density (icorr) and pitting potential (Epit) compared to other FexCu(1−x)CoNiCrMn HEAs in P. aeruginosa-inoculated medium, exhibiting superior resistance to MIC. Anti-microbial tests showed that after 14 d of immersion, Fe0.75Cu0.25CoNiCrMn achieved an antibacterial rate of 89.5%, effectively inhibiting the adhesion and biofilm formation of P. aeruginosa, thereby achieving resistance to MIC.
To enhance the microbiologically influenced corrosion (MIC) resistance of FeCoNiCrMn high entropy alloy (HEAs), a series of FexCu(1−x)CoNiCrMn (x = 1, 0.75, 0.5, and 0.25) HEAs were prepared. Microstructural characteristics, corrosion behavior (morphology observation and electrochemical properties), and antimicrobial performance of FexCu(1−x)CoNiCrMn HEAs were evaluated in a medium inoculated with typical corrosive microorganism Pseudomonas aeruginosa. The aim was to identify copper-containing FeCoNiCrMn HEAs that balance corrosion resistance and antimicrobial properties. Results revealed that all FexCu(1−x)CoNiCrMn (x = 1, 0.75, 0.5, and 0.25) HEAs exhibited an FCC (face centered cubic) phase, with significant grain refinement observed in Fe0.75Cu0.25CoNiCrMn HEA. Electrochemical tests indicated that Fe0.75Cu0.25CoNiCrMn HEA demonstrated lower corrosion current density (icorr) and pitting potential (Epit) compared to other FexCu(1−x)CoNiCrMn HEAs in P. aeruginosa-inoculated medium, exhibiting superior resistance to MIC. Anti-microbial tests showed that after 14 d of immersion, Fe0.75Cu0.25CoNiCrMn achieved an antibacterial rate of 89.5%, effectively inhibiting the adhesion and biofilm formation of P. aeruginosa, thereby achieving resistance to MIC.
2024, vol. 31, no. 11, pp.
2498-2507.
https://doi.org/10.1007/s12613-024-2847-2
Abstract:
During aircraft, ship, and automobile manufacturing, lap structures are frequently produced among Al alloy skins, wall panels, and stiffeners. The occurrence of welding defects severely decreases mechanical properties during friction stir lap welding (FSLW). This study focuses on investigating the effects of rotation rate, multipass welding, and cooling methods on lap defect formation, microstructural evolution, and mechanical properties. Hook defects were eliminated by decreasing welding speed, applying two-pass FLSW with a small welding tool, and introducing additional water cooling, thus leading to a remarkable increase in effective sheet thickness and lap width. This above strategy yielded defect-free joints with an ultrafine-grained microstructure and increased tensile shear force from 298 to 551 N/mm. The fracture behavior of FSLW joints was systematically studied, and a fracture factor of lap joints was proposed to predict their fracture mode. By reducing the rotation rate, using two-pass welding, and employing additional water cooling strategies, an enlarged, strengthened, and defect-free lap zone with refined ultrafine grains was achieved with a quality comparable to that of lap welds based on 7xxx Al alloys. Importantly, this study provides a valuable FSLW method for eliminating hook defects and improving joint performance.
During aircraft, ship, and automobile manufacturing, lap structures are frequently produced among Al alloy skins, wall panels, and stiffeners. The occurrence of welding defects severely decreases mechanical properties during friction stir lap welding (FSLW). This study focuses on investigating the effects of rotation rate, multipass welding, and cooling methods on lap defect formation, microstructural evolution, and mechanical properties. Hook defects were eliminated by decreasing welding speed, applying two-pass FLSW with a small welding tool, and introducing additional water cooling, thus leading to a remarkable increase in effective sheet thickness and lap width. This above strategy yielded defect-free joints with an ultrafine-grained microstructure and increased tensile shear force from 298 to 551 N/mm. The fracture behavior of FSLW joints was systematically studied, and a fracture factor of lap joints was proposed to predict their fracture mode. By reducing the rotation rate, using two-pass welding, and employing additional water cooling strategies, an enlarged, strengthened, and defect-free lap zone with refined ultrafine grains was achieved with a quality comparable to that of lap welds based on 7xxx Al alloys. Importantly, this study provides a valuable FSLW method for eliminating hook defects and improving joint performance.
2024, vol. 31, no. 11, pp.
2508-2517.
https://doi.org/10.1007/s12613-024-2972-y
Abstract:
Facing the complex variable high-temperature environment, electromagnetic wave (EMW) absorbing materials maintaining high stability and satisfying absorbing properties is essential. This study focused on the synthesis and EMW absorbing performance evaluation of TiN/Fe2N/C composite materials, which were prepared using electrostatic spinning followed by a high-temperature nitridation process. The TiN/Fe2N/C fibers constructed a well-developed conductive network that generates considerable conduction loss. The heterogeneous interfaces between different components generated a significant level of interfacial polarization. Thanks to the synergistic effect of stable dielectric loss and optimized impedance matching, the TiN/Fe2N/C composite materials demonstrated excellent and stable absorption performance across a wide temperature range (293–453 K). Moreover, TiN/Fe2N/C-15 achieved a minimum reflection loss (RL) of −48.01 dB and an effective absorption bandwidth (EAB) of 3.64 GHz at 2.1 mm and 373 K. This work provides new insights into the development of high-efficiency and stabile EMW absorbing materials under complex variable high-temperature conditions.
Facing the complex variable high-temperature environment, electromagnetic wave (EMW) absorbing materials maintaining high stability and satisfying absorbing properties is essential. This study focused on the synthesis and EMW absorbing performance evaluation of TiN/Fe2N/C composite materials, which were prepared using electrostatic spinning followed by a high-temperature nitridation process. The TiN/Fe2N/C fibers constructed a well-developed conductive network that generates considerable conduction loss. The heterogeneous interfaces between different components generated a significant level of interfacial polarization. Thanks to the synergistic effect of stable dielectric loss and optimized impedance matching, the TiN/Fe2N/C composite materials demonstrated excellent and stable absorption performance across a wide temperature range (293–453 K). Moreover, TiN/Fe2N/C-15 achieved a minimum reflection loss (RL) of −48.01 dB and an effective absorption bandwidth (EAB) of 3.64 GHz at 2.1 mm and 373 K. This work provides new insights into the development of high-efficiency and stabile EMW absorbing materials under complex variable high-temperature conditions.
2024, vol. 31, no. 11, pp.
2518-2527.
https://doi.org/10.1007/s12613-024-2839-2
Abstract:
Although biopolymers have been widely utilized as triboelectric materials for the construction of self-powered sensing systems, the annihilation of triboelectric charges at high temperatures restricts the output signals and sensitivity of the assembled sensors. Herein, a novel chitosan/montmorillonite/lignin (CML) composite film was designed and employed as a tribopositive layer in the assembly of a self-powered sensing system for use under hot conditions (25–70°C). The dense contact surface resulting from the strong intermolecular interaction between biopolymers and nanofillers restrained the volatilization of induced electrons. The optimized CML-TENG delivered the highest open-circuit voltage (Voc) of 262 V and maximum instantaneous output power of 429 mW/m2. Pristine CH-TENG retained only 39% of its initial Voc at 70°C, whereas the optimized CM5L3-TENG retained 66% of its initial Voc. Our work provides a new strategy for suppressing the annihilation of triboelectric charges at high temperatures, thus boosting the development of self-powered sensing devices for application under hot conditions.
Although biopolymers have been widely utilized as triboelectric materials for the construction of self-powered sensing systems, the annihilation of triboelectric charges at high temperatures restricts the output signals and sensitivity of the assembled sensors. Herein, a novel chitosan/montmorillonite/lignin (CML) composite film was designed and employed as a tribopositive layer in the assembly of a self-powered sensing system for use under hot conditions (25–70°C). The dense contact surface resulting from the strong intermolecular interaction between biopolymers and nanofillers restrained the volatilization of induced electrons. The optimized CML-TENG delivered the highest open-circuit voltage (Voc) of 262 V and maximum instantaneous output power of 429 mW/m2. Pristine CH-TENG retained only 39% of its initial Voc at 70°C, whereas the optimized CM5L3-TENG retained 66% of its initial Voc. Our work provides a new strategy for suppressing the annihilation of triboelectric charges at high temperatures, thus boosting the development of self-powered sensing devices for application under hot conditions.
2024, vol. 31, no. 11, pp.
2528-2534.
https://doi.org/10.1007/s12613-024-2952-2
Abstract:
Hexagonal MnMX-based (M = Co or Ni, X = Si or Ge) alloys exhibit giant reversible barocaloric effects. However, giant volume expansion would result in the as-cast MnMX ingots fragmenting into powders, and inevitably bring the deterioration of mechanical properties and formability. Grain fragmentation can bring degradation of structural transformation entropy change during cyclic application and removal of pressure. In this paper, giant reversible barocaloric effects with high thermal cycle stability can be achieved in the epoxy bonded (MnCoGe)0.96(CuCoSn)0.04 composite. Giant reversible isothermal entropy change of 43.0 J∙kg−1∙K−1 and adiabatic temperature change from barocaloric effects (∆TBCE) of 15.6 K can be obtained within a wide temperature span of 30 K at 360 MPa, which is mainly attributed to the integration of the change in the transition temperature driven by pressure of −101 K∙GPa−1 and suitable thermal hysteresis of 11.1 K. Further, the variation of reversible ∆TBCE against the applied hydrostatic pressure reaches up to 43 K∙GPa−1, which is at the highest level among the other reported giant barocaloric compounds. More importantly, after 60 thermal cycles, the composite does not break and the calorimetric curves coincide well, demonstrating good thermal cycle stability.
Hexagonal MnMX-based (M = Co or Ni, X = Si or Ge) alloys exhibit giant reversible barocaloric effects. However, giant volume expansion would result in the as-cast MnMX ingots fragmenting into powders, and inevitably bring the deterioration of mechanical properties and formability. Grain fragmentation can bring degradation of structural transformation entropy change during cyclic application and removal of pressure. In this paper, giant reversible barocaloric effects with high thermal cycle stability can be achieved in the epoxy bonded (MnCoGe)0.96(CuCoSn)0.04 composite. Giant reversible isothermal entropy change of 43.0 J∙kg−1∙K−1 and adiabatic temperature change from barocaloric effects (∆TBCE) of 15.6 K can be obtained within a wide temperature span of 30 K at 360 MPa, which is mainly attributed to the integration of the change in the transition temperature driven by pressure of −101 K∙GPa−1 and suitable thermal hysteresis of 11.1 K. Further, the variation of reversible ∆TBCE against the applied hydrostatic pressure reaches up to 43 K∙GPa−1, which is at the highest level among the other reported giant barocaloric compounds. More importantly, after 60 thermal cycles, the composite does not break and the calorimetric curves coincide well, demonstrating good thermal cycle stability.
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