SiC whiskers were synthesized in a coke bed using a two-step heat treatment process.The temperature was held for 3 h at 1 200 ℃ before heating to 1 430 ℃ and holding for 3 h.The morphologies of SiC synthesized by th...SiC whiskers were synthesized in a coke bed using a two-step heat treatment process.The temperature was held for 3 h at 1 200 ℃ before heating to 1 430 ℃ and holding for 3 h.The morphologies of SiC synthesized by the two-step heat treatment method were much more different from those produced by direct heating to 1 430 ℃.SiC whiskers formed at 1 200 ℃ firstly and grew at1 430 ℃ to obtain a mean diameter about 326 nm,while the SiC grains with a size range from 0.70 to2.30 μm were obtained by direct heating to the target temperature of 1 430 ℃.This was explained by the different formation mechanisms.The result proposes a promising alternative technical process for whisker-reinforced ceramic/refractory composites in-situ during sintering.展开更多
Cathode samples of nano-diamond by graphitization pretreatment with different temperatures were fabricated by electrophoresis, then the structures and morphologies of the cathode samples were characterized by scanning...Cathode samples of nano-diamond by graphitization pretreatment with different temperatures were fabricated by electrophoresis, then the structures and morphologies of the cathode samples were characterized by scanning electron microscope(SEM) and X-ray diffraction(XRD), and the field emission tests were conducted. The effects of graphitization pretreatment on the field emission characteristics of nano-diamond cathode surface on titanium substrate are studied. The results indicate that the surface morphologies of nano-diamond cathode samples after graphitization pretreatment change a lot, and the field emission characteristics in low-voltage area are improved obviously. However, in high-voltage area, the curve distortion happens, and it doesn't conform the mechanism of field emission characteristics.展开更多
基金supported by the 973 Program Earlier Research Project,under Grant No.2014CB660802
文摘SiC whiskers were synthesized in a coke bed using a two-step heat treatment process.The temperature was held for 3 h at 1 200 ℃ before heating to 1 430 ℃ and holding for 3 h.The morphologies of SiC synthesized by the two-step heat treatment method were much more different from those produced by direct heating to 1 430 ℃.SiC whiskers formed at 1 200 ℃ firstly and grew at1 430 ℃ to obtain a mean diameter about 326 nm,while the SiC grains with a size range from 0.70 to2.30 μm were obtained by direct heating to the target temperature of 1 430 ℃.This was explained by the different formation mechanisms.The result proposes a promising alternative technical process for whisker-reinforced ceramic/refractory composites in-situ during sintering.
基金supported by the PH.D Start-up Foundation of Yan’an University(No.YD 2010-04)the Special Foundation of Yan’an University(No.YDZD 2011-01)+3 种基金the 2014 Education and Innovation Project of Yan’an University for Graduate Studentthe 2014 Local University National Training Project of Innovation and Entrepreneurship for Undergraduates(No.201410719023)the Special Research Funds for Discipline Construction of High Level University Construction(No.2015SXTS02)the Natural Science Foundation of Shaanxi Province(No.2014JM2-5058)
文摘Cathode samples of nano-diamond by graphitization pretreatment with different temperatures were fabricated by electrophoresis, then the structures and morphologies of the cathode samples were characterized by scanning electron microscope(SEM) and X-ray diffraction(XRD), and the field emission tests were conducted. The effects of graphitization pretreatment on the field emission characteristics of nano-diamond cathode surface on titanium substrate are studied. The results indicate that the surface morphologies of nano-diamond cathode samples after graphitization pretreatment change a lot, and the field emission characteristics in low-voltage area are improved obviously. However, in high-voltage area, the curve distortion happens, and it doesn't conform the mechanism of field emission characteristics.
