采用溶胶-凝胶法结合固相反应制备了具有立方尖晶石结构的Li Mn1-xNixTi O4(x=0、0.1、0.2、0.3)锂离子电池正极材料。通过场发射扫描电镜(FESEM)观察材料的表面形貌,所制备的材料均呈现出典型的烧结体特征;用X射线衍射仪(XRD)分析材料...采用溶胶-凝胶法结合固相反应制备了具有立方尖晶石结构的Li Mn1-xNixTi O4(x=0、0.1、0.2、0.3)锂离子电池正极材料。通过场发射扫描电镜(FESEM)观察材料的表面形貌,所制备的材料均呈现出典型的烧结体特征;用X射线衍射仪(XRD)分析材料的物相变化,Ni替代前后均产生杂相Ti O2,但没有产生与替代元素相关的杂相。通过循环伏安、恒电流充放电等测试研究样品的电化学性能。结果表明:Li Mn Ti O4有两对氧化还原峰,分别对应Mn3+/Mn4+、Mn3+/Mn2+的转变,而Ni替代后出现了额外的氧化还原对,即Ni3+/Ni4+的转变。Li Mn1-xNixTi O4(x=0.1、0.2、0.3)的电化学性能均优于Li Mn Ti O4,尤其当Ni替代量为0.1时,Li Mn0.9Ni0.1Ti O4在30 m A/g电流密度下的首次放电容量为171.6 m Ah/g,48次循环后容量为162.8 m Ah/g,容量保持率为82.7%。对Li Mn0.9Ni0.1Ti O4进行非原位XRD测试发现,材料一次循环后结构无明显变化,不存在立方相与四方相之间的转变。展开更多
Multistage heat treatment involving quenching(Q),lamellarizing(L),and tempering(T)is applied to marine 10Ni5CrMoV steel.The microstructure and mechanical properties were studied by multiscale characterizations,and the...Multistage heat treatment involving quenching(Q),lamellarizing(L),and tempering(T)is applied to marine 10Ni5CrMoV steel.The microstructure and mechanical properties were studied by multiscale characterizations,and the kinetics of reverse austenite transformation,strain hardening behavior,and toughening mechanism were further investigated.The lamellarized specimens possess low yield strength but high toughness,especially cryogenic toughness.Lamellarization leads to the development of film-like reversed austenite at the martensite block and lath boundaries,refining the martensite structure and lowering the equivalent grain size.Kinetic analysis of austenite reversion based on the JMAK model shows that the isothermal transformation is dominated by the growth of reversed austenite,and the maximum transformation of reversed austenite is reached at the peak temperature(750℃).The strain hardening behavior based on the modified Crussard-Jaoul analysis indicates that the reversed austenite obtained from lamellarization reduces the proportion of martensite,significantly hindering crack propagation via martensitic transformation during the deformation.As a consequence,the QLT specimens exhibit high machinability and low yield strength.Compared with the QT specimen,the ductile-brittle transition temperature of the QLT specimens decreases from-116 to-130℃due to the low equivalent grain size and reversed austenite,which increases the cleavage force required for crack propagation and absorbs the energy of external load,respectively.This work provides an idea to improve the cryogenic toughness of marine 10Ni5CrMoV steel and lays a theoretical foundation for its industrial application and comprehensive performance improvement.展开更多
Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin f...Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin first”strategy,corn straw is converted to valuable chemicals including lignin monomers,furfural and 5-methoxymethylfurfural via a two steps process.The key of this research lies in the development of a green and low-cost catalytic process utilizing magnetic Raney Ni catalyst and high boiling point ethylene glycol.The utilization of neat ethylene glycol as the sole slovent under atmospheric conditions obviates the need for additional additives,thereby facilitating the entire process to be conducted in glass flasks and rendering it highly convenient for scaling up.In the initial step,depolymerization of corn straw lignin resulted in a monomer yield of 18.1 wt%.Subsequently,in a dimethyl carbonate system,the carbohydrate component underwent complete conversion in a one-pot process,yielding furfural and 5-methoxymethylfurfural as the primary products with an impressive yield of 47.7%.展开更多
The interdiffusion coefficients in Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys were efficiently determined by combining diffusion couple experiments and high-throughput determination of ...The interdiffusion coefficients in Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys were efficiently determined by combining diffusion couple experiments and high-throughput determination of interdiffusion coefficients(HitDIC)software at 1273−1373 K.The results show that the addition of Al,Cu,and Mn to CoCrFeNi high-entropy alloys promotes the diffusion of Co,Cr,and Fe atoms.The comparison of tracer diffusion coefficients indicates that there is no sluggish diffusion in tracer diffusion on the thermodynamic temperature scale for the present Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys.The linear relationship between diffusion entropy and activation energy reveals that the diffusion process of atoms is unaffected by an increase in the number of components as long as the crystal structure remains unchanged.展开更多
文摘采用溶胶-凝胶法结合固相反应制备了具有立方尖晶石结构的Li Mn1-xNixTi O4(x=0、0.1、0.2、0.3)锂离子电池正极材料。通过场发射扫描电镜(FESEM)观察材料的表面形貌,所制备的材料均呈现出典型的烧结体特征;用X射线衍射仪(XRD)分析材料的物相变化,Ni替代前后均产生杂相Ti O2,但没有产生与替代元素相关的杂相。通过循环伏安、恒电流充放电等测试研究样品的电化学性能。结果表明:Li Mn Ti O4有两对氧化还原峰,分别对应Mn3+/Mn4+、Mn3+/Mn2+的转变,而Ni替代后出现了额外的氧化还原对,即Ni3+/Ni4+的转变。Li Mn1-xNixTi O4(x=0.1、0.2、0.3)的电化学性能均优于Li Mn Ti O4,尤其当Ni替代量为0.1时,Li Mn0.9Ni0.1Ti O4在30 m A/g电流密度下的首次放电容量为171.6 m Ah/g,48次循环后容量为162.8 m Ah/g,容量保持率为82.7%。对Li Mn0.9Ni0.1Ti O4进行非原位XRD测试发现,材料一次循环后结构无明显变化,不存在立方相与四方相之间的转变。
基金financially supported by the National Key K&D Program of China(No.2023YFE0200300)the National Natural Science Foundation of China(Nos.52174303and 51874084)the Program of Introducing Talents of Discipline to Universities(No.B21001)。
文摘Multistage heat treatment involving quenching(Q),lamellarizing(L),and tempering(T)is applied to marine 10Ni5CrMoV steel.The microstructure and mechanical properties were studied by multiscale characterizations,and the kinetics of reverse austenite transformation,strain hardening behavior,and toughening mechanism were further investigated.The lamellarized specimens possess low yield strength but high toughness,especially cryogenic toughness.Lamellarization leads to the development of film-like reversed austenite at the martensite block and lath boundaries,refining the martensite structure and lowering the equivalent grain size.Kinetic analysis of austenite reversion based on the JMAK model shows that the isothermal transformation is dominated by the growth of reversed austenite,and the maximum transformation of reversed austenite is reached at the peak temperature(750℃).The strain hardening behavior based on the modified Crussard-Jaoul analysis indicates that the reversed austenite obtained from lamellarization reduces the proportion of martensite,significantly hindering crack propagation via martensitic transformation during the deformation.As a consequence,the QLT specimens exhibit high machinability and low yield strength.Compared with the QT specimen,the ductile-brittle transition temperature of the QLT specimens decreases from-116 to-130℃due to the low equivalent grain size and reversed austenite,which increases the cleavage force required for crack propagation and absorbs the energy of external load,respectively.This work provides an idea to improve the cryogenic toughness of marine 10Ni5CrMoV steel and lays a theoretical foundation for its industrial application and comprehensive performance improvement.
基金supported by the Fundamental Research Funds for the Central Universities(QNTD202302)National Natural Science Foundation of China(22378024)the Foreign expert program(G2022109001L).
文摘Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin first”strategy,corn straw is converted to valuable chemicals including lignin monomers,furfural and 5-methoxymethylfurfural via a two steps process.The key of this research lies in the development of a green and low-cost catalytic process utilizing magnetic Raney Ni catalyst and high boiling point ethylene glycol.The utilization of neat ethylene glycol as the sole slovent under atmospheric conditions obviates the need for additional additives,thereby facilitating the entire process to be conducted in glass flasks and rendering it highly convenient for scaling up.In the initial step,depolymerization of corn straw lignin resulted in a monomer yield of 18.1 wt%.Subsequently,in a dimethyl carbonate system,the carbohydrate component underwent complete conversion in a one-pot process,yielding furfural and 5-methoxymethylfurfural as the primary products with an impressive yield of 47.7%.
基金supported by the National Natural Science Foundation of China(No.52374372)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.23KJB430042)+3 种基金the Jiangsu Province Large Scientific Instruments Open Sharing Autonomous Research Filing Project,China(No.TC2023A037)the Yangzhou City−Yangzhou University Cooperation Foundation,China(No.YZ2022183)High-end Talent Support Program of Yangzhou University,China,Qinglan Project of Yangzhou University,ChinaLvyangjinfeng Talent program of Yangzhou,China.
文摘The interdiffusion coefficients in Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys were efficiently determined by combining diffusion couple experiments and high-throughput determination of interdiffusion coefficients(HitDIC)software at 1273−1373 K.The results show that the addition of Al,Cu,and Mn to CoCrFeNi high-entropy alloys promotes the diffusion of Co,Cr,and Fe atoms.The comparison of tracer diffusion coefficients indicates that there is no sluggish diffusion in tracer diffusion on the thermodynamic temperature scale for the present Al_(0.2)CoCrFeNi,CoCrCu_(0.2)FeNi,and CoCrFeMn_(0.2)Ni high-entropy alloys.The linear relationship between diffusion entropy and activation energy reveals that the diffusion process of atoms is unaffected by an increase in the number of components as long as the crystal structure remains unchanged.
