奥氏体耐热钢由于良好的高温性能因而在火电、核电、航空航天等领域有着重要的应用.细小的晶粒尺寸及基体中弥散分布的碳化物是奥氏体钢具有优异高温性能的关键.奥氏体钢在服役过程中受热循环的影响,其显微组织发生衰退.为探究热循环过...奥氏体耐热钢由于良好的高温性能因而在火电、核电、航空航天等领域有着重要的应用.细小的晶粒尺寸及基体中弥散分布的碳化物是奥氏体钢具有优异高温性能的关键.奥氏体钢在服役过程中受热循环的影响,其显微组织发生衰退.为探究热循环过程中组织演变对力学性能的影响,针对一种供货态的奥氏体耐热钢0Cr25Ni13Si2MoN开展了三组热循环实验.借助光镜(optical microscope,OM)、扫描电镜(scanning electron microscope,SEM)、透射电镜(transmission electron microscope,TEM)和冲击试验机等试验设备,对不同热循环次数后的试样分别进行了显微组织及力学性能分析.结果表明:热循环过程中的组织演变表现出一定的时间依赖性,一次热循环过程完成了回复与再结晶,晶界处析出网状分布的M 23 C 6,降低了材料的韧性.后两次的热循环过程退火孪晶密度增大,但晶界处碳化物数量增加并发生粗化,材料的韧性逐渐恶化.展开更多
Based on density functional theory, we investigate the electronic and magnetic properties of semi-hydrogenated, fully hydrogenated monolayer and bilayer MoN2. We find that the AB stacking bilayer MoN2 exhibits ferroma...Based on density functional theory, we investigate the electronic and magnetic properties of semi-hydrogenated, fully hydrogenated monolayer and bilayer MoN2. We find that the AB stacking bilayer MoN2 exhibits ferromagnetic coupling of intralayer and antiferromagnetic coupling of interlayer, however, the ground states of the semi-hydrogenated, fully hydrogenated monolayer and AA stcaking bilayer MoN2 are nonmagnetic. The fully hydrogenated system has a quasidirect band-gap of 2.5 eV, which has potential applications in light-emitting diode and photovoltaics. The AB stacking bilayer MoN2 shows the Dirac cone at K point in BZ around Fermi energy. Furthermore, the interlayer of the AB stacking bilayer MoN2 is subjected to a weak van der Waals force, while the interlayer of the AA stacking forms N-N covalent bond.展开更多
The advancement of sodium-ion batteries is impeded by challenges such as sluggish ion kinetics and structural instability,particularly in nitride and telluride-based anodes.Herein,a novel multiheterostructured composi...The advancement of sodium-ion batteries is impeded by challenges such as sluggish ion kinetics and structural instability,particularly in nitride and telluride-based anodes.Herein,a novel multiheterostructured composite,MoN/CoTe/NiTe_(2)@NCNTs,was rationally designed by integrating multiple electroactive phases,conductive networks,and hierarchical frameworks into a unified architecture.Unlike conventional binary heterostructures,this ternary system leverages multi-phase synergy to construct extensive interfacial charge redistribution zones,enhancing both structural stability and Na~+ diffusion kinetics.The multidimensional framework ensures structural robustness and buffers volume fluctuations during electrochemical cycling.In half-cell tests,the composite delivers a high reversible capacity of 375.7 mAhg^(-1) at 0.2 A g^(-1),retaining 230.1 mAhg^(-1) after 1000 cycles at 2.0 A g^(-1), demonstrating excellent cycling stability.Even at a high current density of 10.0 A g^(-1),a remarkable capacity of 197.7 mAh g^(-1) is maintained.In full-cell configuration,the MoN/CoTe/NiTe_(2)@NCNTs//Na_(3)V_(2)(PO_4)_(3) system achieves a competitive energy density of 146.9 Wh kg^(-1) and excellent cycling stability with an average capacity degradation rate of <0.11 % per cycle over 500 cycles.Combined density functional theory calculations and ex-situ characterizations reveal a phase-dependent sodium storage mechanism,where intercalation dominates at MoN-rich sites and conversion reactions occur at CoTe/NiTe_(2) domains,supported by interfacial charge redistribution.This work offers a promising strategy for designing advanced multi-heterostructured materials and provides valuable insights into the practical application of highperformance sodium-ion batteries.展开更多
文摘奥氏体耐热钢由于良好的高温性能因而在火电、核电、航空航天等领域有着重要的应用.细小的晶粒尺寸及基体中弥散分布的碳化物是奥氏体钢具有优异高温性能的关键.奥氏体钢在服役过程中受热循环的影响,其显微组织发生衰退.为探究热循环过程中组织演变对力学性能的影响,针对一种供货态的奥氏体耐热钢0Cr25Ni13Si2MoN开展了三组热循环实验.借助光镜(optical microscope,OM)、扫描电镜(scanning electron microscope,SEM)、透射电镜(transmission electron microscope,TEM)和冲击试验机等试验设备,对不同热循环次数后的试样分别进行了显微组织及力学性能分析.结果表明:热循环过程中的组织演变表现出一定的时间依赖性,一次热循环过程完成了回复与再结晶,晶界处析出网状分布的M 23 C 6,降低了材料的韧性.后两次的热循环过程退火孪晶密度增大,但晶界处碳化物数量增加并发生粗化,材料的韧性逐渐恶化.
基金supported by the National Natural Science Foundation of China(Grant Nos.11747168,11604246,and 11704007)the Natural Science Foundation of Guizhou Provincial Education Department,China(Grant Nos.KY[2015]384,KY[2015]446,and KY[2017]053)+1 种基金the Natural Science Foundation of Guizhou Provincial Science and Technology Agency(Grant Nos.LH[2015]7232 and LH[2015]7228)the Science Research Foundation of Tongren University,China(Grant No.trxy DH1529)
文摘Based on density functional theory, we investigate the electronic and magnetic properties of semi-hydrogenated, fully hydrogenated monolayer and bilayer MoN2. We find that the AB stacking bilayer MoN2 exhibits ferromagnetic coupling of intralayer and antiferromagnetic coupling of interlayer, however, the ground states of the semi-hydrogenated, fully hydrogenated monolayer and AA stcaking bilayer MoN2 are nonmagnetic. The fully hydrogenated system has a quasidirect band-gap of 2.5 eV, which has potential applications in light-emitting diode and photovoltaics. The AB stacking bilayer MoN2 shows the Dirac cone at K point in BZ around Fermi energy. Furthermore, the interlayer of the AB stacking bilayer MoN2 is subjected to a weak van der Waals force, while the interlayer of the AA stacking forms N-N covalent bond.
基金financially supported by the program of the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT, and Future planning (grant number 2022R1A4A1034312, 2023R1A2C1007413)the Commercialization Promotion Agency for R&D Outcomes (COMPA) grant funded by the Korean Government (Ministery of Science and ICT) (RS2023-00304764)。
文摘The advancement of sodium-ion batteries is impeded by challenges such as sluggish ion kinetics and structural instability,particularly in nitride and telluride-based anodes.Herein,a novel multiheterostructured composite,MoN/CoTe/NiTe_(2)@NCNTs,was rationally designed by integrating multiple electroactive phases,conductive networks,and hierarchical frameworks into a unified architecture.Unlike conventional binary heterostructures,this ternary system leverages multi-phase synergy to construct extensive interfacial charge redistribution zones,enhancing both structural stability and Na~+ diffusion kinetics.The multidimensional framework ensures structural robustness and buffers volume fluctuations during electrochemical cycling.In half-cell tests,the composite delivers a high reversible capacity of 375.7 mAhg^(-1) at 0.2 A g^(-1),retaining 230.1 mAhg^(-1) after 1000 cycles at 2.0 A g^(-1), demonstrating excellent cycling stability.Even at a high current density of 10.0 A g^(-1),a remarkable capacity of 197.7 mAh g^(-1) is maintained.In full-cell configuration,the MoN/CoTe/NiTe_(2)@NCNTs//Na_(3)V_(2)(PO_4)_(3) system achieves a competitive energy density of 146.9 Wh kg^(-1) and excellent cycling stability with an average capacity degradation rate of <0.11 % per cycle over 500 cycles.Combined density functional theory calculations and ex-situ characterizations reveal a phase-dependent sodium storage mechanism,where intercalation dominates at MoN-rich sites and conversion reactions occur at CoTe/NiTe_(2) domains,supported by interfacial charge redistribution.This work offers a promising strategy for designing advanced multi-heterostructured materials and provides valuable insights into the practical application of highperformance sodium-ion batteries.
