Based on crystallographic theory, there are 63 kinds of polytypes of 13H long-period stacking order (LPSO) structure, 126 kinds of polytypes of 14H LPSO structure, 120 kinds of polytypes of 39R LPSO structure, and 2...Based on crystallographic theory, there are 63 kinds of polytypes of 13H long-period stacking order (LPSO) structure, 126 kinds of polytypes of 14H LPSO structure, 120 kinds of polytypes of 39R LPSO structure, and 223 kinds of polytypes of 42R LPSO structure in a hexagonal close-packed (HCP) system, and their stacking sequences and space groups have been derived in detail. The result provides a theoretical explanation for the various polytypes of the LPSO structure.展开更多
A thermodynamic model Mg x(Xs,Mg)6(Xl,Mg)8(Xs and Xl are elements smaller and larger than Mg)for long-period stacking ordered phases(LPSOs)was proposed based on two key factors:the Xs 6 Xl 8-type L12 clusters and the ...A thermodynamic model Mg x(Xs,Mg)6(Xl,Mg)8(Xs and Xl are elements smaller and larger than Mg)for long-period stacking ordered phases(LPSOs)was proposed based on two key factors:the Xs 6 Xl 8-type L12 clusters and the variation of chemical compositions.In general,all available LPSOs can be described with this model.As a representative system,Mg-Y-Zn with three LPSOs was investigated using the CALPHAD(calculation of phase diagram)approach aided with first-principles calculations.Two new three-phase equilibria were predicted and were validated by key experiments.The model-based descriptions will be the basis for the research and development of magnesium alloys.展开更多
With the rapid development of indium tin oxide(ITO)in the electronic display industry,choosing which raw powders to prepare high-quality ITO targets has always been a controversial topic.In the work,in order to clearl...With the rapid development of indium tin oxide(ITO)in the electronic display industry,choosing which raw powders to prepare high-quality ITO targets has always been a controversial topic.In the work,in order to clearly understand the effect of the raw powders on the microstructure and properties of ITO targets and thin films,tin-doped indium oxide(dITO)and In_(2)O_3-SnO_(2)mixed(mITO)powders were chosen to prepare ITO targets for depositing the films and a comparative study on their microstructure and properties was conducted.It is found that,(1)dITO targets possess a higher solid solubility of tin in indium oxide and more uniform elemental distribution,while there are a higher density,a finer grain size and a higher mass ratio of In_(2)O_3 to SnO_(2)for the mITO targets;(2)dITO films with more coarser columnar grains and a rougher surface prefer to grow along the[100]direction in an Ar atmosphere;(3)the conductive property of ITO films only depends on the doping amount of tin and is independent of the raw powders and the preparation process of the target source;(4)dITO films possess the superior optical property and narrower optical band gap;(5)the etching property of mITO films is superior to that of dITO films due to the lower solid solubility of tin in indium oxide.展开更多
Simple synthesis of multifunctional electrocatalysts with plentiful active sites from earth-abundant materials is especially fascinating. Here, N-doped defective carbon with trace Co(1.5 wt%) was prepared via a scalab...Simple synthesis of multifunctional electrocatalysts with plentiful active sites from earth-abundant materials is especially fascinating. Here, N-doped defective carbon with trace Co(1.5 wt%) was prepared via a scalable one pot solid pyrolysis process. The sample exhibits efficient bifunctional OER/ORR activity in alkaline, mainly ascribed to the unique micro-mesoporous structure(1–3 nm), high population of graphitic-N doping(up to 49.0%), abundant defects and the encapsulated Co nanoparticles with graphitized carbon. The according rechargeable liquid Zn-air batteries showed excellent performance(maximum power density of 154.0 mW cm^(-2); energy density of 773 Wh kg^(-1) at 5 mA cm^(-2) and charging-discharging cycling stability over 100 cycles). As a proof-of-concept, the flexible, rechargeable all-solid-state Zn-air batteries were constructed, and displayed a maximum power density as high as 45.9 mW cm^(-2), among the top level of those reported previously.展开更多
Determining atomistic structures of grain boundaries (GBs) is essential to understand structure--property interplay in oxides.Here,different GB superstructures in CuO nanosheets,including (111) and (114) twinning boun...Determining atomistic structures of grain boundaries (GBs) is essential to understand structure--property interplay in oxides.Here,different GB superstructures in CuO nanosheets,including (111) and (114) twinning boundaries (TBs) and (002)/(223) GB,are investigated.Unlike the lower-energy stoichiometric (111) TB,both experimental and first-principles investigations reveal a severe segregation of Cu and O vacancies and a nonstoichiometric property at (114) TB,which may facilitate ionic transportation and provide space for elemental segregation.More importantly,the calculated electronic structures have shown the increased conductivity as well as the unanticipated magnetism in both (114) TB and (002)/(223) GB.These findings could contribute to the race towards the property-directing structural design by GB engineering.展开更多
High-strength Al-Cu-Mg-Ag-Sm alloy was fabricated and subjected to single-stage aging and pre-aging(two-stage aging). Effect of pre-aging on micros tructure and mechanical properties of the alloy was investigated. It ...High-strength Al-Cu-Mg-Ag-Sm alloy was fabricated and subjected to single-stage aging and pre-aging(two-stage aging). Effect of pre-aging on micros tructure and mechanical properties of the alloy was investigated. It is found that the alloy is mainly composed of α-Al, Al_2Cu, Al_2CuMg and AlCu_4Sm. The number of plate-like Ω Al_2Cu precipitates is comparable to that of rod-like S Al_2 CuMg precipitates in the single-stage aged alloy, whereas, in the two-stage aged alloy, it is much higher than that of S precipitates. Q precipitates have a smaller plate thickness and distribute more uniformly in the two-stage aged alloy than in the single-stage aged alloy.Ultimate tensile strength(UTS) and yield strength of the two-stage aged alloy are 12% higher than those of the single-stage aged one, indicating a better aging hardening caused by the two-stage aging. The increased tensile properties mainly come from both stronger precipitation strengthening caused by more Ω precipitates in the twostage aged alloy and stronger solution strengthening from Mg atoms. The fracture surfaces consist of both dimple zones composed of microscale dimples and platform zones composed of nanoscale dimples. The total area of dimple zones for single-stage aged alloy is much higher than that for two-stage aged alloy, which can be attributed to different numbers of Ω precipitates in the two alloys.展开更多
Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application.Na3V2(PO4)3 is an attractive cathode material with excellent e...Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application.Na3V2(PO4)3 is an attractive cathode material with excellent electrochemical stability and fast ion diffusion coefficient within the 3D NASICON structure.Nevertheless,the practical application of Na3V2(PO4)3 is seriously hindered by its intrinsically poor electronic conductivity.Herein,solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na3V2(PO4)3 cathode material,delivering cnhanced clectrochemical performances.N-Doped carbon layer coating servfes as a highly conducting pathway,and creates numerous extrinsic defects and active sites,which can facilitate the storage and diffusion of Na^+.Morcover,the N-doped carbon layer can provide a stable framework to accommodate the agglomeration of the electrode upon electrode cycling.N-Doped carbon coated Na3V2(PO4)3(NC-NVP)exhibits excellent long cycling life and superior rate performances than bare Na3V2(PO4)3 without carbon coating.NC-NVP delivers a stable capacity of 95.9mA·h/g after 500 cycles at 1C rate,which corresponds to high capacity retention(94.6%)with respect to the initial capacity(101.4mA·h/g).Over 91.3% of the initial capacity is retained after 500 cycles at 5C,and the capacity can reach 85mA·h/g at 30C rate.展开更多
碱性水电解(AWE)作为一种具有工业应用前景的绿色制氢方法,能够用来改善能源短缺和环境污染问题.然而,由于电极材料昂贵且效率低下,这种方法生产氢气的效率比较低.本文采用块状AlCoCrFeNi高熵合金作为碱性电解水的有效电极.研究发现通...碱性水电解(AWE)作为一种具有工业应用前景的绿色制氢方法,能够用来改善能源短缺和环境污染问题.然而,由于电极材料昂贵且效率低下,这种方法生产氢气的效率比较低.本文采用块状AlCoCrFeNi高熵合金作为碱性电解水的有效电极.研究发现通过快速阳极氧化(5 min)处理的高熵合金可以同时对析氢和析氧反应(HER和OER)具有超高的催化活性,只需要880和845 m V的过电位就可以达到-500 mA cm-2(HER)和500 mA cm-2(OER)的电流密度.特别地,该催化剂只需要3.00 V就可以达到500 mA cm-2的全解水电流密度,并且在此电流密度下表现出超过100小时的出色稳定性.我们的研究表明,阳极氧化的块体AlCoCrFeNi高熵合金作为高效催化剂在工业水电解制氢中具有广阔的应用前景,有望用于缓解环境问题和能源危机.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51371130,51171130,and 51271134)the Fundamental Research Funds for the Central Universities,Chinathe Open Research Fund of Science and Technology on High Strength Structural Materials Laboratory,Central South University,China
文摘Based on crystallographic theory, there are 63 kinds of polytypes of 13H long-period stacking order (LPSO) structure, 126 kinds of polytypes of 14H LPSO structure, 120 kinds of polytypes of 39R LPSO structure, and 223 kinds of polytypes of 42R LPSO structure in a hexagonal close-packed (HCP) system, and their stacking sequences and space groups have been derived in detail. The result provides a theoretical explanation for the various polytypes of the LPSO structure.
基金Project(6142907200301) supported by the National Defense Pre-Research Foundation of ChinaProject supported by the Key Laboratory for Lightweight High Strength Structural Materials,Central South University,China。
基金This work was supported by the National Key Research and Development Plan(No.2016YFB0701202).K.Chang ac-knowledges the CAS Pioneer Hundred Talents Program.Pro-fessor Zi-Kui Liu is greatly acknowledged for the discussion about the general thermodynamic model for LPSOs.
文摘A thermodynamic model Mg x(Xs,Mg)6(Xl,Mg)8(Xs and Xl are elements smaller and larger than Mg)for long-period stacking ordered phases(LPSOs)was proposed based on two key factors:the Xs 6 Xl 8-type L12 clusters and the variation of chemical compositions.In general,all available LPSOs can be described with this model.As a representative system,Mg-Y-Zn with three LPSOs was investigated using the CALPHAD(calculation of phase diagram)approach aided with first-principles calculations.Two new three-phase equilibria were predicted and were validated by key experiments.The model-based descriptions will be the basis for the research and development of magnesium alloys.
基金financially supported by the National Key R&D Program of China(No.2017YFB0305401)the National Natural Science Foundation of China(Nos.51874369 and 51871249)the Huxiang Young Talents Plan(No.2018RS3007)。
文摘With the rapid development of indium tin oxide(ITO)in the electronic display industry,choosing which raw powders to prepare high-quality ITO targets has always been a controversial topic.In the work,in order to clearly understand the effect of the raw powders on the microstructure and properties of ITO targets and thin films,tin-doped indium oxide(dITO)and In_(2)O_3-SnO_(2)mixed(mITO)powders were chosen to prepare ITO targets for depositing the films and a comparative study on their microstructure and properties was conducted.It is found that,(1)dITO targets possess a higher solid solubility of tin in indium oxide and more uniform elemental distribution,while there are a higher density,a finer grain size and a higher mass ratio of In_(2)O_3 to SnO_(2)for the mITO targets;(2)dITO films with more coarser columnar grains and a rougher surface prefer to grow along the[100]direction in an Ar atmosphere;(3)the conductive property of ITO films only depends on the doping amount of tin and is independent of the raw powders and the preparation process of the target source;(4)dITO films possess the superior optical property and narrower optical band gap;(5)the etching property of mITO films is superior to that of dITO films due to the lower solid solubility of tin in indium oxide.
基金support from the Research Project of National University of Defense Technology(ZK16-03-32)National University Student Innovation Programthe support form Research Foundation of Education Bureau of Hunan Province(16K102)
文摘Simple synthesis of multifunctional electrocatalysts with plentiful active sites from earth-abundant materials is especially fascinating. Here, N-doped defective carbon with trace Co(1.5 wt%) was prepared via a scalable one pot solid pyrolysis process. The sample exhibits efficient bifunctional OER/ORR activity in alkaline, mainly ascribed to the unique micro-mesoporous structure(1–3 nm), high population of graphitic-N doping(up to 49.0%), abundant defects and the encapsulated Co nanoparticles with graphitized carbon. The according rechargeable liquid Zn-air batteries showed excellent performance(maximum power density of 154.0 mW cm^(-2); energy density of 773 Wh kg^(-1) at 5 mA cm^(-2) and charging-discharging cycling stability over 100 cycles). As a proof-of-concept, the flexible, rechargeable all-solid-state Zn-air batteries were constructed, and displayed a maximum power density as high as 45.9 mW cm^(-2), among the top level of those reported previously.
基金the National Natural Science Foundation of China (Nos.51671148,51271134,J1210061,11674251,51501132, and 51601132)the Hubei Provincial Natural Science Foundation of China (Nos.2016CFB446 and 2016CFB155)+4 种基金the Fundamental Research Funds for the Central Universitiesthe CERS-1-26 (CERSChina Equipment and Education Resources System)the China Postdoctoral Science Foundation (No.2014T70734)the Open Research Fund of Science and Technology on High Strength Structural Materials Laboratory (Central South University)the Suzhou Science and Technology project (No.SYG201619).
文摘Determining atomistic structures of grain boundaries (GBs) is essential to understand structure--property interplay in oxides.Here,different GB superstructures in CuO nanosheets,including (111) and (114) twinning boundaries (TBs) and (002)/(223) GB,are investigated.Unlike the lower-energy stoichiometric (111) TB,both experimental and first-principles investigations reveal a severe segregation of Cu and O vacancies and a nonstoichiometric property at (114) TB,which may facilitate ionic transportation and provide space for elemental segregation.More importantly,the calculated electronic structures have shown the increased conductivity as well as the unanticipated magnetism in both (114) TB and (002)/(223) GB.These findings could contribute to the race towards the property-directing structural design by GB engineering.
基金financially supported by the National Natural Science Foundation of China (No. 51171108)the Open Research Fund of Science and Technology on High Strength Structural Materials Laboratory, Central South University, China
文摘High-strength Al-Cu-Mg-Ag-Sm alloy was fabricated and subjected to single-stage aging and pre-aging(two-stage aging). Effect of pre-aging on micros tructure and mechanical properties of the alloy was investigated. It is found that the alloy is mainly composed of α-Al, Al_2Cu, Al_2CuMg and AlCu_4Sm. The number of plate-like Ω Al_2Cu precipitates is comparable to that of rod-like S Al_2 CuMg precipitates in the single-stage aged alloy, whereas, in the two-stage aged alloy, it is much higher than that of S precipitates. Q precipitates have a smaller plate thickness and distribute more uniformly in the two-stage aged alloy than in the single-stage aged alloy.Ultimate tensile strength(UTS) and yield strength of the two-stage aged alloy are 12% higher than those of the single-stage aged one, indicating a better aging hardening caused by the two-stage aging. The increased tensile properties mainly come from both stronger precipitation strengthening caused by more Ω precipitates in the twostage aged alloy and stronger solution strengthening from Mg atoms. The fracture surfaces consist of both dimple zones composed of microscale dimples and platform zones composed of nanoscale dimples. The total area of dimple zones for single-stage aged alloy is much higher than that for two-stage aged alloy, which can be attributed to different numbers of Ω precipitates in the two alloys.
基金the National Key Research and Development Program of China(Nos.2017YFB0102000,2018YFB0104200)the Central South University Postdoctoral Foundation,China(No.140050018)+3 种基金the National Natural Science Foundation of China(Nos.51904342,51622406,and 21673298)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(CAST)(No.2017QNRC001)the Innovation Mover Program of Central South University,China(Nos.2018CX005,2017CX004)the Hunan Provincial Natural Science Foundation,China(No.2018JJ3633)。
文摘Cathodes with high cycling stability and rate capability are required for ambient temperature sodium ion batteries in renewable energy storage application.Na3V2(PO4)3 is an attractive cathode material with excellent electrochemical stability and fast ion diffusion coefficient within the 3D NASICON structure.Nevertheless,the practical application of Na3V2(PO4)3 is seriously hindered by its intrinsically poor electronic conductivity.Herein,solvent evaporation method is presented to obtain the nitrogen-doped carbon coated Na3V2(PO4)3 cathode material,delivering cnhanced clectrochemical performances.N-Doped carbon layer coating servfes as a highly conducting pathway,and creates numerous extrinsic defects and active sites,which can facilitate the storage and diffusion of Na^+.Morcover,the N-doped carbon layer can provide a stable framework to accommodate the agglomeration of the electrode upon electrode cycling.N-Doped carbon coated Na3V2(PO4)3(NC-NVP)exhibits excellent long cycling life and superior rate performances than bare Na3V2(PO4)3 without carbon coating.NC-NVP delivers a stable capacity of 95.9mA·h/g after 500 cycles at 1C rate,which corresponds to high capacity retention(94.6%)with respect to the initial capacity(101.4mA·h/g).Over 91.3% of the initial capacity is retained after 500 cycles at 5C,and the capacity can reach 85mA·h/g at 30C rate.
基金supported by the Multi-Year Research Grants(MYRG2020-00207-IAPME)from the University of Macaothe Science and Technology Development Fund from Macao SAR(FDCT)(0125/2018/A3,0081/2019/AMJ,0033/2019/AMJ,0102/2019/A2,and 0154/2019/A3)+1 种基金the Nature Science Foundation of Shandong Province(ZR2020ZD04)Hunan Science Fund for Distinguished Young Scholars(2020JJ2046).
文摘碱性水电解(AWE)作为一种具有工业应用前景的绿色制氢方法,能够用来改善能源短缺和环境污染问题.然而,由于电极材料昂贵且效率低下,这种方法生产氢气的效率比较低.本文采用块状AlCoCrFeNi高熵合金作为碱性电解水的有效电极.研究发现通过快速阳极氧化(5 min)处理的高熵合金可以同时对析氢和析氧反应(HER和OER)具有超高的催化活性,只需要880和845 m V的过电位就可以达到-500 mA cm-2(HER)和500 mA cm-2(OER)的电流密度.特别地,该催化剂只需要3.00 V就可以达到500 mA cm-2的全解水电流密度,并且在此电流密度下表现出超过100小时的出色稳定性.我们的研究表明,阳极氧化的块体AlCoCrFeNi高熵合金作为高效催化剂在工业水电解制氢中具有广阔的应用前景,有望用于缓解环境问题和能源危机.