Search2024 Vol. 31, No. 1
Display Method:
2024, vol. 31, no. 1, pp.
1-17.
https://doi.org/10.1007/s12613-023-2709-3
Abstract:
The flotation separation of Cu–Fe sulfide minerals at low alkalinity can be achieved using selective depressants. In the flotation system of Cu–Fe sulfide minerals, depressants usually preferentially interact with the pyrite surface to render the mineral surface hydrophilic and hinder the adsorption of the collector. This review summarizes the advances in depressants for the flotation separation of Cu–Fe sulfide minerals at low alkalinity. These advances include use of inorganic depressants (oxidants and sulfur–oxygen compounds), natural polysaccharides (starch, dextrin, konjac glucomannan, and galactomannan), modified polymers (carboxymethyl cellulose, polyacrylamide, lignosulfonate, and tricarboxylate sodium starch), organic acids (polyglutamic acid, sodium humate, tannic acid, pyrogallic acid, salicylic acid, and lactic acid), sodium dimethyl dithiocarbamate, and diethylenetriamine. The potential application of specific inorganic and organic depressants in the flotation separation of Cu–Fe sulfide minerals at low alkalinity is reviewed. The advances in the use of organic depressants with respect to the flotation separation of Cu–Fe sulfide minerals are comprehensively detailed. Additionally, the depression performances and mechanisms of different types of organic depressants on mineral surfaces are summarized. Finally, several perspectives on depressants vis-à-vis flotation separation of Cu–Fe sulfide minerals at low alkalinity are proposed.
The flotation separation of Cu–Fe sulfide minerals at low alkalinity can be achieved using selective depressants. In the flotation system of Cu–Fe sulfide minerals, depressants usually preferentially interact with the pyrite surface to render the mineral surface hydrophilic and hinder the adsorption of the collector. This review summarizes the advances in depressants for the flotation separation of Cu–Fe sulfide minerals at low alkalinity. These advances include use of inorganic depressants (oxidants and sulfur–oxygen compounds), natural polysaccharides (starch, dextrin, konjac glucomannan, and galactomannan), modified polymers (carboxymethyl cellulose, polyacrylamide, lignosulfonate, and tricarboxylate sodium starch), organic acids (polyglutamic acid, sodium humate, tannic acid, pyrogallic acid, salicylic acid, and lactic acid), sodium dimethyl dithiocarbamate, and diethylenetriamine. The potential application of specific inorganic and organic depressants in the flotation separation of Cu–Fe sulfide minerals at low alkalinity is reviewed. The advances in the use of organic depressants with respect to the flotation separation of Cu–Fe sulfide minerals are comprehensively detailed. Additionally, the depression performances and mechanisms of different types of organic depressants on mineral surfaces are summarized. Finally, several perspectives on depressants vis-à-vis flotation separation of Cu–Fe sulfide minerals at low alkalinity are proposed.
2024, vol. 31, no. 1, pp.
18-32.
https://doi.org/10.1007/s12613-023-2740-4
Abstract:
In the long traditional process of steelmaking, excess oxygen is blown into the converter, and alloying elements are used for deoxidation. This inevitably results in excessive deoxidation of products remaining within the steel liquid, affecting the cleanliness of the steel. With the increasing requirements for steel performance, reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary. After more than a hundred years of development, the total oxygen content in steel has been reduced from approximately 100 × 10−6 to approximately 10 × 10−6, and it can be controlled below 5 × 10−6 in some steel grades. A relatively stable and mature deoxidation technology has been formed, but further reducing the oxygen content in steel is no longer significant for improving steel quality. Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process. The technology combines silicon–manganese predeoxidation, ladle furnace diffusion deoxidation, and vacuum final deoxidation. We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation. Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4 × 10−6 and 8 × 10−6, altering the type of inclusions, eliminating large particle Ds-type inclusions, improving the flowability of the steel liquid, and deriving a higher fatigue life. The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.
In the long traditional process of steelmaking, excess oxygen is blown into the converter, and alloying elements are used for deoxidation. This inevitably results in excessive deoxidation of products remaining within the steel liquid, affecting the cleanliness of the steel. With the increasing requirements for steel performance, reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary. After more than a hundred years of development, the total oxygen content in steel has been reduced from approximately 100 × 10−6 to approximately 10 × 10−6, and it can be controlled below 5 × 10−6 in some steel grades. A relatively stable and mature deoxidation technology has been formed, but further reducing the oxygen content in steel is no longer significant for improving steel quality. Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process. The technology combines silicon–manganese predeoxidation, ladle furnace diffusion deoxidation, and vacuum final deoxidation. We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation. Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4 × 10−6 and 8 × 10−6, altering the type of inclusions, eliminating large particle Ds-type inclusions, improving the flowability of the steel liquid, and deriving a higher fatigue life. The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.
2024, vol. 31, no. 1, pp.
33-47.
https://doi.org/10.1007/s12613-023-2665-y
Abstract:
Zinc-ion batteries (ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion, and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution, and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. Therefore, this work systematically introduces the research progress of zinc metal-free anodes in “rocking chair” ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides, transition metal sulfides, MXene (two dimensional transition metal carbide) composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. This paper is expected to provide a reference for the further promotion of commercial rechargeable ZIBs.
Zinc-ion batteries (ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion, and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution, and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. Therefore, this work systematically introduces the research progress of zinc metal-free anodes in “rocking chair” ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides, transition metal sulfides, MXene (two dimensional transition metal carbide) composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. This paper is expected to provide a reference for the further promotion of commercial rechargeable ZIBs.
2024, vol. 31, no. 1, pp.
48-59.
https://doi.org/10.1007/s12613-023-2712-8
Abstract:
Metal-to-insulator transitions (MITs), which are achieved in 3d-band correlated transitional metal oxides, trigger abrupt variations in electrical, optical, and/or magnetic properties beyond those of conventional semiconductors. Among such material families, iron (Fe: 3d64s2)-containing oxides pique interest owing to their widely tunable MIT properties, which are associated with the various valence states of Fe. Their potential electronic applications also show promise, given the large abundance of Fe on Earth. Representative MIT properties triggered by critical temperature (TMIT) were reported for ReFe2O4 (Fe2.5+), ReBaFe2O5 (Fe2.5+), Fe3O4 (Fe2.67+), Re1/3Sr2/3FeO3 (Fe3.67+), ReCu3Fe4O12 (Fe3.75+), and Ca1−xSrxFeO3 (Fe4+) (where Re represents rare-earth elements). The common feature of MITs of these Fe-containing oxides is that they are usually accompanied by charge ordering transitions or disproportionation associated with the valence states of Fe. Herein, we review the material family of Fe-containing MIT oxides, their MIT functionalities, and their respective mechanisms. From the perspective of potentially correlated electronic applications, the tunability of the TMIT and its resultant resistive change in Fe-containing oxides are summarized and further compared with those of other materials exhibiting MIT functionality. In particular, we highlight the abrupt MIT and wide tunability of TMIT of Fe-containing quadruple perovskites, such as ReCu3Fe4O12. However, their effective material synthesis still needs to be further explored to cater to potential applications.
Metal-to-insulator transitions (MITs), which are achieved in 3d-band correlated transitional metal oxides, trigger abrupt variations in electrical, optical, and/or magnetic properties beyond those of conventional semiconductors. Among such material families, iron (Fe: 3d64s2)-containing oxides pique interest owing to their widely tunable MIT properties, which are associated with the various valence states of Fe. Their potential electronic applications also show promise, given the large abundance of Fe on Earth. Representative MIT properties triggered by critical temperature (TMIT) were reported for ReFe2O4 (Fe2.5+), ReBaFe2O5 (Fe2.5+), Fe3O4 (Fe2.67+), Re1/3Sr2/3FeO3 (Fe3.67+), ReCu3Fe4O12 (Fe3.75+), and Ca1−xSrxFeO3 (Fe4+) (where Re represents rare-earth elements). The common feature of MITs of these Fe-containing oxides is that they are usually accompanied by charge ordering transitions or disproportionation associated with the valence states of Fe. Herein, we review the material family of Fe-containing MIT oxides, their MIT functionalities, and their respective mechanisms. From the perspective of potentially correlated electronic applications, the tunability of the TMIT and its resultant resistive change in Fe-containing oxides are summarized and further compared with those of other materials exhibiting MIT functionality. In particular, we highlight the abrupt MIT and wide tunability of TMIT of Fe-containing quadruple perovskites, such as ReCu3Fe4O12. However, their effective material synthesis still needs to be further explored to cater to potential applications.
2024, vol. 31, no. 1, pp.
60-70.
https://doi.org/10.1007/s12613-023-2700-z
Abstract:
The challenge of high temperatures in deep mining remains harmful to the health of workers and their production efficiency. The addition of phase change materials (PCMs) to filling slurry and the use of the cold storage function of these materials to reduce downhole temperatures is an effective approach to alleviate the aforementioned problem. Paraffin–CaCl2·6H2O composite PCM was prepared in the laboratory. The composition, phase change latent heat, thermal conductivity, and cemented tailing backfill (CTB) compressive strength of the new material were studied. The heat transfer characteristics and endothermic effect of the PCM were simulated using Fluent software. The results showed the following: (1) The new paraffin–CaCl2·6H2O composite PCM improved the thermal conductivity of native paraffin while avoiding the water solubility of CaCl2·6H2O. (2) The calculation formula of the thermal conductivity of CaCl2·6H2O combined with paraffin was deduced, and the reasons were explained in principle. (3) The “enthalpy–mass scale model” was applied to calculate the phase change latent heat of nonreactive composite PCMs. (4) The addition of the paraffin–CaCl2·6H2O composite PCM reduced the CTB strength but increased its heat absorption capacity. This research can give a theoretical foundation for the use of heat storage backfill in green mines.
The challenge of high temperatures in deep mining remains harmful to the health of workers and their production efficiency. The addition of phase change materials (PCMs) to filling slurry and the use of the cold storage function of these materials to reduce downhole temperatures is an effective approach to alleviate the aforementioned problem. Paraffin–CaCl2·6H2O composite PCM was prepared in the laboratory. The composition, phase change latent heat, thermal conductivity, and cemented tailing backfill (CTB) compressive strength of the new material were studied. The heat transfer characteristics and endothermic effect of the PCM were simulated using Fluent software. The results showed the following: (1) The new paraffin–CaCl2·6H2O composite PCM improved the thermal conductivity of native paraffin while avoiding the water solubility of CaCl2·6H2O. (2) The calculation formula of the thermal conductivity of CaCl2·6H2O combined with paraffin was deduced, and the reasons were explained in principle. (3) The “enthalpy–mass scale model” was applied to calculate the phase change latent heat of nonreactive composite PCMs. (4) The addition of the paraffin–CaCl2·6H2O composite PCM reduced the CTB strength but increased its heat absorption capacity. This research can give a theoretical foundation for the use of heat storage backfill in green mines.
2024, vol. 31, no. 1, pp.
71-80.
https://doi.org/10.1007/s12613-023-2718-2
Abstract:
The impact of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOl) at low temperatures was evaluated using flotation tests at various scales. The low-temperature synergistic mechanism of ADB and NaOl was explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test, and flotation reagent size measurement. The flotation tests revealed that the collector mixed with octadecyl dimethyl betaine (ODB) and NaOl in a mass ratio of 4:96 exhibited the highest collection capacity. The combined collector could increase the scheelite recovery by 3.48% at low temperatures of 8–12°C. This is particularly relevant in the Luanchuan area, which has the largest scheelite concentrate output in China. The results confirmed that ODB enhanced the collection capability of NaOl by improving the dispersion and foaming performance. Betaine can be introduced as an additive to NaOl to improve the recovery of scheelite at low temperatures.
The impact of alkyl dimethyl betaine (ADB) on the collection capacity of sodium oleate (NaOl) at low temperatures was evaluated using flotation tests at various scales. The low-temperature synergistic mechanism of ADB and NaOl was explored by infrared spectroscopy, X-ray photoelectron spectroscopy, surface tension measurement, foam performance test, and flotation reagent size measurement. The flotation tests revealed that the collector mixed with octadecyl dimethyl betaine (ODB) and NaOl in a mass ratio of 4:96 exhibited the highest collection capacity. The combined collector could increase the scheelite recovery by 3.48% at low temperatures of 8–12°C. This is particularly relevant in the Luanchuan area, which has the largest scheelite concentrate output in China. The results confirmed that ODB enhanced the collection capability of NaOl by improving the dispersion and foaming performance. Betaine can be introduced as an additive to NaOl to improve the recovery of scheelite at low temperatures.
2024, vol. 31, no. 1, pp.
81-90.
https://doi.org/10.1007/s12613-023-2688-4
Abstract:
The mechanism involved in the phase transformation process of pyrolusite (MnO2) during roasting in a reducing atmosphere was systematically elucidated in this study, with the aim of effectively using low-grade complex manganese ore resources. According to single-factor experiment results, the roasted product with a divalent manganese (Mn2+) distribution rate of 95.30% was obtained at a roasting time of 25 min, a roasting temperature of 700°C, a CO concentration of 20at%, and a total gas volume of 500 mL·min−1, in which the manganese was mainly in the form of manganosite (MnO). Scanning electron microscopy and Brunauer–Emmett–Teller theory demonstrated the microstructural evolution of the roasted product and the gradual reduction in the pyrolusite ore from the surface to the core. Thermodynamic calculations, X-ray photoelectron spectroscopy, and X-ray diffractometry analyses determined that the phase transformation of pyrolusite followed the order of MnO2→Mn2O3→Mn3O4→MnO phase by phase, and the reduction of manganese oxides in each valence state proceeded simultaneously.
The mechanism involved in the phase transformation process of pyrolusite (MnO2) during roasting in a reducing atmosphere was systematically elucidated in this study, with the aim of effectively using low-grade complex manganese ore resources. According to single-factor experiment results, the roasted product with a divalent manganese (Mn2+) distribution rate of 95.30% was obtained at a roasting time of 25 min, a roasting temperature of 700°C, a CO concentration of 20at%, and a total gas volume of 500 mL·min−1, in which the manganese was mainly in the form of manganosite (MnO). Scanning electron microscopy and Brunauer–Emmett–Teller theory demonstrated the microstructural evolution of the roasted product and the gradual reduction in the pyrolusite ore from the surface to the core. Thermodynamic calculations, X-ray photoelectron spectroscopy, and X-ray diffractometry analyses determined that the phase transformation of pyrolusite followed the order of MnO2→Mn2O3→Mn3O4→MnO phase by phase, and the reduction of manganese oxides in each valence state proceeded simultaneously.
2024, vol. 31, no. 1, pp.
91-105.
https://doi.org/10.1007/s12613-023-2727-1
Abstract:
The preparation process of sodium molybdate has the disadvantages of high energy consumption, low thermal efficiency, and high raw material requirement of molybdenum trioxide, in order to realize the green and efficient development of molybdenum concentrate resources, this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching. Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate. The effects of roasting temperature, holding time, and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na2MoO4·2H2O) were investigated. Under the optimal process conditions: roasting temperature of 700°C, holding time of 110 min, and power-to-mass ratio of 110 W/g, the molybdenum state of existence was converted from MoS2 to MoO3. The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated, the optimal leaching conditions include a solution concentration of 2.5 mol/L, a liquid-to-solid ratio of 2 mL/g, a leaching temperature of 60°C, and leaching solution termination at pH 8. The optimum conditions result in a leaching rate of sodium molybdate of 96.24%. Meanwhile, the content of sodium molybdate reaches 94.08wt% after leaching and removing impurities. Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution. This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate, which provides a new idea for the high-value utilization of molybdenum concentrate.
The preparation process of sodium molybdate has the disadvantages of high energy consumption, low thermal efficiency, and high raw material requirement of molybdenum trioxide, in order to realize the green and efficient development of molybdenum concentrate resources, this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching. Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate. The effects of roasting temperature, holding time, and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na2MoO4·2H2O) were investigated. Under the optimal process conditions: roasting temperature of 700°C, holding time of 110 min, and power-to-mass ratio of 110 W/g, the molybdenum state of existence was converted from MoS2 to MoO3. The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated, the optimal leaching conditions include a solution concentration of 2.5 mol/L, a liquid-to-solid ratio of 2 mL/g, a leaching temperature of 60°C, and leaching solution termination at pH 8. The optimum conditions result in a leaching rate of sodium molybdate of 96.24%. Meanwhile, the content of sodium molybdate reaches 94.08wt% after leaching and removing impurities. Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution. This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate, which provides a new idea for the high-value utilization of molybdenum concentrate.
2024, vol. 31, no. 1, pp.
106-117.
https://doi.org/10.1007/s12613-023-2670-1
Abstract:
The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process, which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error ±300 m3 is 96.67%; determination coefficient (R2) and root mean square error (RMSE) are 0.6984 and 150.03 m3, respectively. The oxygen blow time prediction hit ratio within the error ±0.6 min is 89.50%; R2 and RMSE are 0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.
The amount of oxygen blown into the converter is one of the key parameters for the control of the converter blowing process, which directly affects the tap-to-tap time of converter. In this study, a hybrid model based on oxygen balance mechanism (OBM) and deep neural network (DNN) was established for predicting oxygen blowing time in converter. A three-step method was utilized in the hybrid model. First, the oxygen consumption volume was predicted by the OBM model and DNN model, respectively. Second, a more accurate oxygen consumption volume was obtained by integrating the OBM model and DNN model. Finally, the converter oxygen blowing time was calculated according to the oxygen consumption volume and the oxygen supply intensity of each heat. The proposed hybrid model was verified using the actual data collected from an integrated steel plant in China, and compared with multiple linear regression model, OBM model, and neural network model including extreme learning machine, back propagation neural network, and DNN. The test results indicate that the hybrid model with a network structure of 3 hidden layer layers, 32-16-8 neurons per hidden layer, and 0.1 learning rate has the best prediction accuracy and stronger generalization ability compared with other models. The predicted hit ratio of oxygen consumption volume within the error ±300 m3 is 96.67%; determination coefficient (R2) and root mean square error (RMSE) are 0.6984 and 150.03 m3, respectively. The oxygen blow time prediction hit ratio within the error ±0.6 min is 89.50%; R2 and RMSE are 0.9486 and 0.3592 min, respectively. As a result, the proposed model can effectively predict the oxygen consumption volume and oxygen blowing time in the converter.
Research ArticleOpen Access
2024, vol. 31, no. 1, pp.
118-128.
https://doi.org/10.1007/s12613-023-2747-x
Abstract:
Multi-material laser-based powder bed fusion (PBF-LB) allows manufacturing of parts with 3-dimensional gradient and additional functionality in a single step. This research focuses on the combination of thermally-conductive CuCr1Zr with hard M300 tool steel. Two interface configurations of M300 on CuCr1Zr and CuCr1Zr on M300 were investigated. Ultra-fine grains form at the interface due to the low mutual solubility of Cu and steel. The material mixing zone size is dependent on the configurations and tunable in the range of 0.1–0.3 mm by introducing a separate set of parameters for the interface layers. Microcracks and pores mainly occur in the transition zone. Regardless of these defects, the thermal diffusivity of bimetallic parts with 50vol% of CuCr1Zr significantly increases by 70%–150% compared to pure M300. The thermal diffusivity of CuCr1Zr and the hardness of M300 steel can be enhanced simultaneously by applying the aging heat treatment.
Multi-material laser-based powder bed fusion (PBF-LB) allows manufacturing of parts with 3-dimensional gradient and additional functionality in a single step. This research focuses on the combination of thermally-conductive CuCr1Zr with hard M300 tool steel. Two interface configurations of M300 on CuCr1Zr and CuCr1Zr on M300 were investigated. Ultra-fine grains form at the interface due to the low mutual solubility of Cu and steel. The material mixing zone size is dependent on the configurations and tunable in the range of 0.1–0.3 mm by introducing a separate set of parameters for the interface layers. Microcracks and pores mainly occur in the transition zone. Regardless of these defects, the thermal diffusivity of bimetallic parts with 50vol% of CuCr1Zr significantly increases by 70%–150% compared to pure M300. The thermal diffusivity of CuCr1Zr and the hardness of M300 steel can be enhanced simultaneously by applying the aging heat treatment.
2024, vol. 31, no. 1, pp.
129-137.
https://doi.org/10.1007/s12613-023-2759-6
Abstract:
Mg−Al alloys have excellent strength and ductility but relatively low thermal conductivity due to Al addition. The accurate prediction of thermal conductivity is a prerequisite for designing Mg−Al alloys with high thermal conductivity. Thus, databases for predicting temperature- and composition-dependent thermal conductivities must be established. In this study, Mg−Al−La alloys with different contents of Al2La, Al3La, and Al11La3 phases and solid solubility of Al in the α-Mg phase were designed. The influence of the second phase(s) and Al solid solubility on thermal conductivity was investigated. Experimental results revealed a second phase transformation from Al2La to Al3La and further to Al11La3 with the increasing Al content at a constant La amount. The degree of the negative effect of the second phase(s) on thermal diffusivity followed the sequence of Al2La > Al3La > Al11La3. Compared with the second phase, an increase in the solid solubility of Al in α-Mg remarkably reduced the thermal conductivity. On the basis of the experimental data, a database of the reciprocal thermal diffusivity of the Mg−Al−La system was established by calculation of the phase diagram (CALPHAD) method. With a standard error of ±1.2 W/(m·K), the predicted results were in good agreement with the experimental data. The established database can be used to design Mg−Al alloys with high thermal conductivity and provide valuable guidance for expanding their application prospects.
Mg−Al alloys have excellent strength and ductility but relatively low thermal conductivity due to Al addition. The accurate prediction of thermal conductivity is a prerequisite for designing Mg−Al alloys with high thermal conductivity. Thus, databases for predicting temperature- and composition-dependent thermal conductivities must be established. In this study, Mg−Al−La alloys with different contents of Al2La, Al3La, and Al11La3 phases and solid solubility of Al in the α-Mg phase were designed. The influence of the second phase(s) and Al solid solubility on thermal conductivity was investigated. Experimental results revealed a second phase transformation from Al2La to Al3La and further to Al11La3 with the increasing Al content at a constant La amount. The degree of the negative effect of the second phase(s) on thermal diffusivity followed the sequence of Al2La > Al3La > Al11La3. Compared with the second phase, an increase in the solid solubility of Al in α-Mg remarkably reduced the thermal conductivity. On the basis of the experimental data, a database of the reciprocal thermal diffusivity of the Mg−Al−La system was established by calculation of the phase diagram (CALPHAD) method. With a standard error of ±1.2 W/(m·K), the predicted results were in good agreement with the experimental data. The established database can be used to design Mg−Al alloys with high thermal conductivity and provide valuable guidance for expanding their application prospects.
2024, vol. 31, no. 1, pp.
138-145.
https://doi.org/10.1007/s12613-023-2687-5
Abstract:
A high thrust-to-weight ratio poses challenges to the high-temperature performance of Ni-based superalloys. The oxidation behavior of GH4738 at extreme temperatures has been investigated by isothermal and non-isothermal experiments. As a result of the competitive diffusion of alloying elements, the oxide scale included an outermost porous oxide layer (OOL), an inner relatively dense oxide layer (IOL), and an internal oxide zone (IOZ), depending on the temperature and time. A high temperature led to the formation of large voids at the IOL/IOZ interface. At 1200°C, the continuity of the Cr-rich oxide layer in the IOL was destroyed, and thus, spallation occurred. Extension of oxidation time contributed to the size of Al-rich oxide particles with the increase in the IOZ. Based on this finding, the oxidation kinetics of GH4738 was discussed, and the corresponding oxidation behavior at 900–1100°C was predicted.
A high thrust-to-weight ratio poses challenges to the high-temperature performance of Ni-based superalloys. The oxidation behavior of GH4738 at extreme temperatures has been investigated by isothermal and non-isothermal experiments. As a result of the competitive diffusion of alloying elements, the oxide scale included an outermost porous oxide layer (OOL), an inner relatively dense oxide layer (IOL), and an internal oxide zone (IOZ), depending on the temperature and time. A high temperature led to the formation of large voids at the IOL/IOZ interface. At 1200°C, the continuity of the Cr-rich oxide layer in the IOL was destroyed, and thus, spallation occurred. Extension of oxidation time contributed to the size of Al-rich oxide particles with the increase in the IOZ. Based on this finding, the oxidation kinetics of GH4738 was discussed, and the corresponding oxidation behavior at 900–1100°C was predicted.
2024, vol. 31, no. 1, pp.
146-154.
https://doi.org/10.1007/s12613-023-2711-9
Abstract:
W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6 through a combined analysis of X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2 μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro- and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°C.
W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6 through a combined analysis of X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2 μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro- and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°C.
2024, vol. 31, no. 1, pp.
155-164.
https://doi.org/10.1007/s12613-023-2689-3
Abstract:
A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90° and was not corroded visually after 500 h of neutral salt spray test at 35°C. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.
A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90° and was not corroded visually after 500 h of neutral salt spray test at 35°C. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.
2024, vol. 31, no. 1, pp.
165-178.
https://doi.org/10.1007/s12613-023-2678-6
Abstract:
Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO2. We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO2/P-doped porous hollow g-C3N4 nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1%G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of 0.1%G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO2, PCN, and N-TiO2/PCN (TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO2 and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO2, PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4 times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1%G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1%G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.
Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO2. We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO2/P-doped porous hollow g-C3N4 nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1%G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of 0.1%G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO2, PCN, and N-TiO2/PCN (TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO2 and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO2, PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4 times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1%G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1%G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.
2024, vol. 31, no. 1, pp.
179-185.
https://doi.org/10.1007/s12613-023-2724-4
Abstract:
Cation additives can efficiently enhance the total electrochemical capabilities of zinc-ion hybrid capacitors (ZHCs). However, their energy storage mechanisms in zinc-based systems are still under debate. Herein, we modulate the electrolyte and achieve dual-ion storage by adding magnesium ions. And we assemble several Zn//activated carbon devices with different electrolyte concentrations and investigate their electrochemical reaction dynamic behaviors. The zinc-ion capacitor with Mg2+ mixed solution delivers 82 mAh·g−1 capacity at 1 A·g−1 and maintains 91% of the original capacitance after 10000 cycling. It is superior to the other assembled zinc-ion devices in single-component electrolytes. The finding demonstrates that the double-ion storage mechanism enables the superior rate performance and long cycle lifetime of ZHCs.
2024, vol. 31, no. 1, pp.
186-196.
https://doi.org/10.1007/s12613-023-2744-0
Abstract:
Solid-state impedance spectroscopy (SS-IS) was used to investigate the influence of structural modifications resulting from the addition of Nb2O5 on the dielectric properties and relaxation processes in the quaternary mixed glass former (MGF) system 35Na2O–10V2O5–(55−x)P2O5–xNb2O5 (x = 0–40, mol%). The dielectric parameters, including the dielectric strength and dielectric loss, are determined from the frequency and temperature-dependent complex permittivity data, revealing a significant dependence on the Nb2O5 content. The transition from a predominantly phosphate glass network (x < 10, region I) to a mixed niobate–phosphate glass network (10 ≤ x ≤ 20, region II) leads to an increase in the dielectric parameters, which correlates with the observed trend in the direct-current (DC) conductivity. In the predominantly niobate network (x ≥ 25, region III), the highly polarizable nature of Nb5+ ions leads to a further increase in the dielectric permittivity and dielectric strength. This is particularly evident in Nb-40 glass-ceramic, which contains Na13Nb35O94 crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz. The relaxation studies, analyzed through modulus formalism and complex impedance data, show that DC conductivity and relaxation processes are governed by the same mechanism, attributed to ionic conductivity. In contrast to glasses with a single peak in frequency dependence of imaginary part of electrical modulus, M″(ω), Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times. The high-frequency peak indicates bulk ionic conductivity, while the additional low-frequency peak is associated with the grain boundary effect, confirmed by the electrical equivalent circuit (EEC) modelling. The scaling characteristics of permittivity and conductivity spectra, along with the electrical modulus, validate time-temperature superposition and demonstrate a strong correlation with composition and modification of the glass structure upon Nb2O5 incorporation.
Solid-state impedance spectroscopy (SS-IS) was used to investigate the influence of structural modifications resulting from the addition of Nb2O5 on the dielectric properties and relaxation processes in the quaternary mixed glass former (MGF) system 35Na2O–10V2O5–(55−x)P2O5–xNb2O5 (x = 0–40, mol%). The dielectric parameters, including the dielectric strength and dielectric loss, are determined from the frequency and temperature-dependent complex permittivity data, revealing a significant dependence on the Nb2O5 content. The transition from a predominantly phosphate glass network (x < 10, region I) to a mixed niobate–phosphate glass network (10 ≤ x ≤ 20, region II) leads to an increase in the dielectric parameters, which correlates with the observed trend in the direct-current (DC) conductivity. In the predominantly niobate network (x ≥ 25, region III), the highly polarizable nature of Nb5+ ions leads to a further increase in the dielectric permittivity and dielectric strength. This is particularly evident in Nb-40 glass-ceramic, which contains Na13Nb35O94 crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz. The relaxation studies, analyzed through modulus formalism and complex impedance data, show that DC conductivity and relaxation processes are governed by the same mechanism, attributed to ionic conductivity. In contrast to glasses with a single peak in frequency dependence of imaginary part of electrical modulus, M″(ω), Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times. The high-frequency peak indicates bulk ionic conductivity, while the additional low-frequency peak is associated with the grain boundary effect, confirmed by the electrical equivalent circuit (EEC) modelling. The scaling characteristics of permittivity and conductivity spectra, along with the electrical modulus, validate time-temperature superposition and demonstrate a strong correlation with composition and modification of the glass structure upon Nb2O5 incorporation.
2024, vol. 31, no. 1, pp.
197-205.
https://doi.org/10.1007/s12613-023-2707-5
Abstract:
Scholars aim for the improved impedance matching (Z) of materials while maintaining their excellent wave absorption properties. Based on the hydrolysis characteristics of isopropyl titanate, a simple preparation process for the coating of carbonyl iron powder (CIP) with TiO2 was designed. Given the TiO2 coating, the Z of the CIP@TiO2 composite was adjusted well by decreasing the dielectric constant. Moreover, the interfacial polarization of CIP@TiO2 was enhanced. Ultimately, the electromagnetic-wave (EMW) absorption property of the CIP@TiO2 composite was improved substantially, the minimum reflection loss reached −46.07 dB, and the effective absorption bandwidth can reach 8 GHz at the composite thickness of 1.5 mm. Moreover, compared with CIP, the oxidation resistance of CIP@TiO2 showed remarkable improvement. The results revealed that the oxidation starting temperature of CIP@TiO2 was about 400°C, whereas the uncoated CIP had an oxidation starting temperature of approximately 250°C. Moreover, the largest oxidation rate temperature of CIP@TiO2 increased to around 550°C. This work opens up a novel strategy for the production of high-performance EMW absorbers via structural design.
Scholars aim for the improved impedance matching (Z) of materials while maintaining their excellent wave absorption properties. Based on the hydrolysis characteristics of isopropyl titanate, a simple preparation process for the coating of carbonyl iron powder (CIP) with TiO2 was designed. Given the TiO2 coating, the Z of the CIP@TiO2 composite was adjusted well by decreasing the dielectric constant. Moreover, the interfacial polarization of CIP@TiO2 was enhanced. Ultimately, the electromagnetic-wave (EMW) absorption property of the CIP@TiO2 composite was improved substantially, the minimum reflection loss reached −46.07 dB, and the effective absorption bandwidth can reach 8 GHz at the composite thickness of 1.5 mm. Moreover, compared with CIP, the oxidation resistance of CIP@TiO2 showed remarkable improvement. The results revealed that the oxidation starting temperature of CIP@TiO2 was about 400°C, whereas the uncoated CIP had an oxidation starting temperature of approximately 250°C. Moreover, the largest oxidation rate temperature of CIP@TiO2 increased to around 550°C. This work opens up a novel strategy for the production of high-performance EMW absorbers via structural design.
2024, vol. 31, no. 1, pp.
206-215.
https://doi.org/10.1007/s12613-023-2682-x
Abstract:
Phase change materials (PCMs) can be incorporated with low-cost minerals to synthesize composites for thermal energy storage in building applications. Stone coal (SC) after vanadium extraction treatment shows potential for secondary utilization in composite preparation. We prepared SC-based composite PCMs with SC as a matrix, stearic acid (SA) as a PCM, and expanded graphite (EG) as an additive. The combined roasting and acid leaching treatment of raw SC was conducted to understand the effect of vanadium extraction on promoting loading capacity. Results showed that the combined treatment of roasting at 900°C and leaching increased the SC loading of the composite by 6.2% by improving the specific surface area. The loading capacity and thermal conductivity of the composite obviously increased by 127% and 48.19%, respectively, due to the contribution of 3wt% EG. These data were supported by the high load of 66.69% and thermal conductivity of 0.59 W·m−1·K−1 of the designed composite. The obtained composite exhibited a phase change temperature of 52.17°C, melting latent heat of 121.5 J·g−1, and good chemical compatibility. The SC-based composite has prospects in building applications exploiting the secondary utilization of minerals.
Phase change materials (PCMs) can be incorporated with low-cost minerals to synthesize composites for thermal energy storage in building applications. Stone coal (SC) after vanadium extraction treatment shows potential for secondary utilization in composite preparation. We prepared SC-based composite PCMs with SC as a matrix, stearic acid (SA) as a PCM, and expanded graphite (EG) as an additive. The combined roasting and acid leaching treatment of raw SC was conducted to understand the effect of vanadium extraction on promoting loading capacity. Results showed that the combined treatment of roasting at 900°C and leaching increased the SC loading of the composite by 6.2% by improving the specific surface area. The loading capacity and thermal conductivity of the composite obviously increased by 127% and 48.19%, respectively, due to the contribution of 3wt% EG. These data were supported by the high load of 66.69% and thermal conductivity of 0.59 W·m−1·K−1 of the designed composite. The obtained composite exhibited a phase change temperature of 52.17°C, melting latent heat of 121.5 J·g−1, and good chemical compatibility. The SC-based composite has prospects in building applications exploiting the secondary utilization of minerals.
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