Tensile tests were carried out on gradient nanograined copper samples to investigate the grain orientation dependence of mechanically induced grain boundary migration(GBM) process. The relationship between GBM and the...Tensile tests were carried out on gradient nanograined copper samples to investigate the grain orientation dependence of mechanically induced grain boundary migration(GBM) process. The relationship between GBM and the orientations of nanograins relative to loading direction was established by using electron backscatter diffraction. GBM is found to be more pronounced in the grains with higher Schmid factors where dislocations are easier to slip. As a result, the fraction of high angle grain boundaries decreases and that of low angle grain boundaries increases after GBM.展开更多
Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sinte...Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.展开更多
基金financially supported by the Chinese Ministry of Science and Technology (Nos. 2017YFA0204401 and 2017YFA0700700)the Chinese Academy of Sciences (No.zdyz201701)。
文摘Tensile tests were carried out on gradient nanograined copper samples to investigate the grain orientation dependence of mechanically induced grain boundary migration(GBM) process. The relationship between GBM and the orientations of nanograins relative to loading direction was established by using electron backscatter diffraction. GBM is found to be more pronounced in the grains with higher Schmid factors where dislocations are easier to slip. As a result, the fraction of high angle grain boundaries decreases and that of low angle grain boundaries increases after GBM.
基金financially supported by the National Natural Science Foundation of China(Nos.51302138 and 21663001)the Western Light Talent Training Program of Chinese Academy of Sciences。
文摘Dense nano-grained Ni_(0.7)Mn_(2.3O4) negative temperature coefficient(NTC) thermistors were fabricated by a novel two-step sintering approach that combines rapid sintering and principle of conventional two-step sintering technique.Samples were sintered at 1042℃ for 30 s in the first rapid step and then at 850-950℃ for 20 h in the second soaking step.Crystal phase,microstructure and electrical properties of sintered samples were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),resistance temperature relationship and aging performance.Sintered samples show a single-phase cubic spinel structure and indicate a high relative density ranging from 84% to 91% of the theoretical density.Moreover,average grain sizes of sintered samples under SEM are distributed between 254 and 570 nm.Meanwhile,the resistivity and the aging coefficient significantly decrease when soaking sintering temperature rises.In addition,the obtained material constant(B) ranges from 3931 to 3981 K.Ni_(0.7)Mn_(2.3)O_(4)-3(soaking at 900℃) and Ni_(0.7)Mn_(2.3O4)-4(soaking at 950℃) present little aging behavior,implying great electrical stability.
