The excellent properties of metallic glass(MG)films make them perfect candidates for the use in miniature systems and tools.However,their high coefficients of friction(COFs)and poor wear resistance considerably limit ...The excellent properties of metallic glass(MG)films make them perfect candidates for the use in miniature systems and tools.However,their high coefficients of friction(COFs)and poor wear resistance considerably limit their long-term performance in nanoscale contact.We report the fabrication of a MG/graphene multilayer by the repeated deposition of Cu_(50)Zr_(50) MG with alternating layers of graphene.The microstructure of the multilayer was characterized by the transmission electron microscopy(TEM).Its mechanical and nanotribological properties were studied by nanoindentation and nanoscratch tests,respectively.A molecular dynamics(MD)simulation revealed that the addition of graphene endowed the MG with superelastic recovery,which reduced friction during nanoscratching.In comparison with the monolithic MG film,the multilayer exhibited improved wear resistance and a low COF in repeated nanowear tests owing to the enhanced mechanical properties and lubricating effect caused by the graphene layer.This work is expected to motivate the design of other novel MG films with excellent nanowear properties for engineering applications.展开更多
Using an atomic force microscope,the running-in process of a single crystalline silicon wafer coated with native oxide layer(Si-SiO_(x))against a SiO_(2)microsphere was investigated under various normal loads and disp...Using an atomic force microscope,the running-in process of a single crystalline silicon wafer coated with native oxide layer(Si-SiO_(x))against a SiO_(2)microsphere was investigated under various normal loads and displacement amplitudes in ambient air.As the number of sliding cycles increased,both the friction force Ft of the Si-SiO_(x)/SiO_(2)pair and the wear rate of the silicon surface showed sharp drops during the initial 50 cycles and then leveled off in the remaining cycles.The sharp drop in Ft appeared to be induced mainly by the reduction of adhesion-related interfacial force between the Si-SiO_(x)/SiO_(2)pair.During the running-in process,the contact area of the Si-SiO_(x)/SiO_(2)pair might become hydrophobic due to removal of the hydrophilic oxide layer on the silicon surface and the surface change of the SiO_(2)tip,which caused the reduction of friction force and the wear rate of the Si-SiO_(x)/SiO_(2)pair.A phenomenological model is proposed to explain the running-in process of the Si-SiO_(x)/SiO_(2)pair in ambient air.The results may help us understand the mechanism of the running-in process of the Si-SiO_(x)/SiO_(2)pair at nanoscale and reduce wear failure in dynamic microelectromechanical systems(MEMS).展开更多
基金The authors would like to thank the National Natural Science Foundation of China(No.51801161)Guangdong Basic and Applied Basic Research Foundation,China(No.2021A1515010756)+1 种基金the Natural Science Foundation of Jiangsu Province,China(No.BK20180266)the Fundamental Research Funds for the Central Universities(No.3102019JC001).
文摘The excellent properties of metallic glass(MG)films make them perfect candidates for the use in miniature systems and tools.However,their high coefficients of friction(COFs)and poor wear resistance considerably limit their long-term performance in nanoscale contact.We report the fabrication of a MG/graphene multilayer by the repeated deposition of Cu_(50)Zr_(50) MG with alternating layers of graphene.The microstructure of the multilayer was characterized by the transmission electron microscopy(TEM).Its mechanical and nanotribological properties were studied by nanoindentation and nanoscratch tests,respectively.A molecular dynamics(MD)simulation revealed that the addition of graphene endowed the MG with superelastic recovery,which reduced friction during nanoscratching.In comparison with the monolithic MG film,the multilayer exhibited improved wear resistance and a low COF in repeated nanowear tests owing to the enhanced mechanical properties and lubricating effect caused by the graphene layer.This work is expected to motivate the design of other novel MG films with excellent nanowear properties for engineering applications.
基金the financial support from National Basic Research Program(No.2011CB707604)Natural Science Foundation of China(51175441,90923017).
文摘Using an atomic force microscope,the running-in process of a single crystalline silicon wafer coated with native oxide layer(Si-SiO_(x))against a SiO_(2)microsphere was investigated under various normal loads and displacement amplitudes in ambient air.As the number of sliding cycles increased,both the friction force Ft of the Si-SiO_(x)/SiO_(2)pair and the wear rate of the silicon surface showed sharp drops during the initial 50 cycles and then leveled off in the remaining cycles.The sharp drop in Ft appeared to be induced mainly by the reduction of adhesion-related interfacial force between the Si-SiO_(x)/SiO_(2)pair.During the running-in process,the contact area of the Si-SiO_(x)/SiO_(2)pair might become hydrophobic due to removal of the hydrophilic oxide layer on the silicon surface and the surface change of the SiO_(2)tip,which caused the reduction of friction force and the wear rate of the Si-SiO_(x)/SiO_(2)pair.A phenomenological model is proposed to explain the running-in process of the Si-SiO_(x)/SiO_(2)pair in ambient air.The results may help us understand the mechanism of the running-in process of the Si-SiO_(x)/SiO_(2)pair at nanoscale and reduce wear failure in dynamic microelectromechanical systems(MEMS).
