The buckling behavior of a typical structure consisting of a micro constantan wire and a polymer membrane under coupled electrical-mechanical loading was studied. The phenomenon that the constantan wire delaminates fr...The buckling behavior of a typical structure consisting of a micro constantan wire and a polymer membrane under coupled electrical-mechanical loading was studied. The phenomenon that the constantan wire delaminates from the polymer membrane was observed after unloading. The interfacial toughness of the constantan wire and the polymer membrane was estimated. Moreover, several new instability modes of the constantan wire could be further triggered based on the buckle-driven delamination. After electrical loading and tensile loading, the constantan wire was likely to fracture based on buckling. After electrical loading and compressive loading, the constantan wire was easily folded at the top of the buckling region. On the occasion, the constantan wire buckled towards the inside of the polymer membrane under electrical-compressive loading. The mechanisms of these instability modes were analyzed.展开更多
The Ni （001） surface, Ni3Nb （001） surface and Ni （001）/Ni3Nb （001） interfaces were studied using the first-principles pseudopotential plane-wave method. The adhesion work, thermal stability and electronic stru...The Ni （001） surface, Ni3Nb （001） surface and Ni （001）/Ni3Nb （001） interfaces were studied using the first-principles pseudopotential plane-wave method. The adhesion work, thermal stability and electronic structure of Ni/Ni3Nb （001） interfaces were calculated to expound the influence of atom termination and stacking sequence on the interface strength and stability. Simulated results indicate that Ni and Ni3Nb （001） surface models with more than eight atomic layers exhibit bulk-like interior. The （Ni＋Nb）-terminated interface with hollow site stacking has the largest cohesive strength and critical stress for crack propagation and the best thermal stability among the four models. This interfacial Ni and the first nearest neighbor Nb atoms form covalent bonds across the interface region, which are mainly contributed by Nb 4d and Ni 3d valence electrons. By comparison, the thermal stability of Ni/Ni3Nb （001） interfaces is worse than Ni/Ni3A1 （001） interface, implying that the former is harder to form. But the Ni/Ni3Nb interface can improve the mechanical properties ofNi-based superalloys.展开更多
Carbon quantum dots(CQDs),which contain a core structure composed of sp^(2)carbon,can be used as the reinforcing phase like graphene and carbon nanotubes in metal matrix.In this paper,the CQD/Cu composite material was...Carbon quantum dots(CQDs),which contain a core structure composed of sp^(2)carbon,can be used as the reinforcing phase like graphene and carbon nanotubes in metal matrix.In this paper,the CQD/Cu composite material was prepared by powder metallurgy method.The composite powder was prepared by molecular blending method and ball milling method at first,and then densified into bulk material by spark plasma sintering(SPS).X-ray diffraction,Raman spectroscopy,infrared spectroscopy,and nuclear magnetic resonance were employed to characterize the CQD synthesized under different temperature conditions,and then CQDs with a higher degree of sp^(2)were utilized as the reinforcement to prepare composite materials with different contents.Mechanical properties and electrical conductivity results show that the tensile strength of the 0.2 CQD/Cu composite material is~31%higher than that of the pure copper sample,and the conductivity of 0.4 CQD/Cu is~96%IACS,which is as high as pure copper.TEM and HRTEM results show that good interface bonding of CQD and copper grain is the key to maintaining high mechanical and electrical conductivity.This research provides an important foundation and direction for new carbon materials reinforced metal matrix composites.展开更多
基金Supported by National Basic Research Program of China(2014CB 921102)National Natural Science Foundation of China(11434009,11374279,11461161009)+1 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB01020000)the Fundamental Research Funds for the Central Universities(WK2030020027)
基金Projects(2010CB631005,2011CB606105)support by the National Basic Research Program of ChinaProjects(11232008,91216301,11227801,11172151)supported by the National Natural Science Foundation of ChinaProject supported by Tsinghua University Initiative Scientific Research Program
文摘The buckling behavior of a typical structure consisting of a micro constantan wire and a polymer membrane under coupled electrical-mechanical loading was studied. The phenomenon that the constantan wire delaminates from the polymer membrane was observed after unloading. The interfacial toughness of the constantan wire and the polymer membrane was estimated. Moreover, several new instability modes of the constantan wire could be further triggered based on the buckle-driven delamination. After electrical loading and tensile loading, the constantan wire was likely to fracture based on buckling. After electrical loading and compressive loading, the constantan wire was easily folded at the top of the buckling region. On the occasion, the constantan wire buckled towards the inside of the polymer membrane under electrical-compressive loading. The mechanisms of these instability modes were analyzed.
基金Project(2011DFA50520)supported by International Cooperation Project Supported by Ministry of Science and Technology of ChinaProjects(51204147,51274175)supported by the National Natural Science Foundation of China+1 种基金Projects(2011-key6,2013-81)supported by Research Project Supported by Shanxi Scholarship Council of ChinaProjects(2013081017,2012081013)supported by International Cooperation Project Supported by Shanxi Province,China
文摘The Ni （001） surface, Ni3Nb （001） surface and Ni （001）/Ni3Nb （001） interfaces were studied using the first-principles pseudopotential plane-wave method. The adhesion work, thermal stability and electronic structure of Ni/Ni3Nb （001） interfaces were calculated to expound the influence of atom termination and stacking sequence on the interface strength and stability. Simulated results indicate that Ni and Ni3Nb （001） surface models with more than eight atomic layers exhibit bulk-like interior. The （Ni＋Nb）-terminated interface with hollow site stacking has the largest cohesive strength and critical stress for crack propagation and the best thermal stability among the four models. This interfacial Ni and the first nearest neighbor Nb atoms form covalent bonds across the interface region, which are mainly contributed by Nb 4d and Ni 3d valence electrons. By comparison, the thermal stability of Ni/Ni3Nb （001） interfaces is worse than Ni/Ni3A1 （001） interface, implying that the former is harder to form. But the Ni/Ni3Nb interface can improve the mechanical properties ofNi-based superalloys.
基金Project(52064032)supported by the National Natural Science Foundation of ChinaProjects(2019ZE001,202002AB080001)supported by the Yunnan Science and Technology Projects,ChinaProject(YNWR-QNBJ-2018-005)supported by the Yunnan Ten Thousand Talents Plan Young&Elite Talents,China。
文摘Carbon quantum dots(CQDs),which contain a core structure composed of sp^(2)carbon,can be used as the reinforcing phase like graphene and carbon nanotubes in metal matrix.In this paper,the CQD/Cu composite material was prepared by powder metallurgy method.The composite powder was prepared by molecular blending method and ball milling method at first,and then densified into bulk material by spark plasma sintering(SPS).X-ray diffraction,Raman spectroscopy,infrared spectroscopy,and nuclear magnetic resonance were employed to characterize the CQD synthesized under different temperature conditions,and then CQDs with a higher degree of sp^(2)were utilized as the reinforcement to prepare composite materials with different contents.Mechanical properties and electrical conductivity results show that the tensile strength of the 0.2 CQD/Cu composite material is~31%higher than that of the pure copper sample,and the conductivity of 0.4 CQD/Cu is~96%IACS,which is as high as pure copper.TEM and HRTEM results show that good interface bonding of CQD and copper grain is the key to maintaining high mechanical and electrical conductivity.This research provides an important foundation and direction for new carbon materials reinforced metal matrix composites.
