Carbon nitride films were deposited on Si (100) substrates using plasma-enhanced chemical vapor deposition (PECVD) technique from CH4 and N2 at different applied dc bias voltage. The microstructure, composition and ch...Carbon nitride films were deposited on Si (100) substrates using plasma-enhanced chemical vapor deposition (PECVD) technique from CH4 and N2 at different applied dc bias voltage. The microstructure, composition and chemical bonding of the resulting films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The mechanical properties such as hardness and elastic modulus of the films were evaluated using nano-indentation. As the results, the Raman spectra, showing the G and D bands, indicate the amorphous structure of the films. XPS and FTIR measurements demonstrate the existence of various carbon-nitride bonds in the films and the hydrogenation of carbon nitride phase. The composition ratio of N to C, the nano-hardness and the elastic modulus of the carbon nitride films increase with increasing dc bias voltage and reach the maximums at a dc bias voltage of 300 V, then they decrease with further increase of the dc bias voltage. Moreover, the XRD analyses indicate that the carbon nitride film contains some polycrystalline C3N4 phase embedded in the amorphous matrix at optimized deposition condition of dc bias voltage of 300 V.展开更多
A kind of conductive and heating unit, which can reach a high surface electroheat temperature at a low voltage, was developed in view of the traditional electroheat coating which has a low surface electroheat temperat...A kind of conductive and heating unit, which can reach a high surface electroheat temperature at a low voltage, was developed in view of the traditional electroheat coating which has a low surface electroheat temperature and an insufficient heat resistance of its binder. The coating molded electroheat carbon film(CMECF) was prepared by carbonizing the coating which was prepared by adding modified resin into flake graphite and carbon fiber, coating molded onto the surface of the heat resisting matrix after dried, while the hot pressing molded electroheat thick carbon film(HPMETCF) was prepared by carbonizing the bodies whose powders were hot pressing molded directly. The surface and inner microstructure of the carbon film was characterized and analyzed by SEM and DSC/TG, while electroheat property was tested by voltage-current volume resistivity tester and electrical parameter tester. The results show that, close-packed carbon network configuration is formed within the composite electroheat carbon film which yields a volume resistivity of 0.5×10 -210.0×10 -2Ω·cm at room temperature. The electroheat carbon film after anti-oxidizable treatment reaches a higher surface electroheat temperature than that of the existing electroheat coatings at a low voltage, and has excellent electroheat property, high thermal efficiency as well as stable physicochemical property. It is found that, at room temperature(19±2℃) and 22V for 5min, the surface electroheat temperature of the self-produced CMECF (m_ filler/m_ resin=1.8/1) reaches 112℃ while HPMETCF (m_ filler/m_ resin=3.6/1) reaches 265℃.展开更多
以硅烷和氨气分别做为硅源和氮源,以高纯氮气为载气,采用热壁式管式反应炉,通过低压化学气相沉积(low pressure chemical vapor deposition,LPCVD)技术制备了氮化硅薄膜(SiN_x)。借助椭圆偏振仪研究了SiN_x薄膜的生长动力学,通过Fourie...以硅烷和氨气分别做为硅源和氮源,以高纯氮气为载气,采用热壁式管式反应炉,通过低压化学气相沉积(low pressure chemical vapor deposition,LPCVD)技术制备了氮化硅薄膜(SiN_x)。借助椭圆偏振仪研究了SiN_x薄膜的生长动力学,通过Fourier红外光谱和X光电子能谱表征了SiN_x薄膜的性质,并利用原子力显微镜观察了SiN_x薄膜的微观形貌。在其它工艺条件相同的情况下,SiN_x薄膜的生长速率随着工作压力的增大单调增加,原料气中氨气与硅烷的流量之比(R)对薄膜的生长速率有相反的影响。随着反应温度的升高,沉积速率逐渐增加,在840℃附近达到最大,随后迅速降低。当R<2时获得富Si的SiN_x薄膜(x<1.33);当R>4时获得近化学计量(z≈1.33)的SiN_x薄膜。展开更多
1985,1989年A.Y.May与M.L.Cohen先后采用半经验公式和第一原理赝势算法(First principle pseudo energy calculation)计算并预言了硬度可与金刚石相媲美的β-C_3N_4材料的存在。之后,各国材料工作者对C_3N_4的材料性能以及实验合成进行...1985,1989年A.Y.May与M.L.Cohen先后采用半经验公式和第一原理赝势算法(First principle pseudo energy calculation)计算并预言了硬度可与金刚石相媲美的β-C_3N_4材料的存在。之后,各国材料工作者对C_3N_4的材料性能以及实验合成进行了广泛的探索。新型超硬材料C_3N_4的研究日益成为材料科学的研究热点。本文根据介绍了C_3N_4材料的理论起源和研究现状。展开更多
Via structural searching methodology and first-principles calculations, we predicted two new BC_6N allotropes, a Ccentered monoclinic BC6N (Cm-BC6N) and a primitive-centered monoclinic BC6N (Pm-BC6N).The lattice vibra...Via structural searching methodology and first-principles calculations, we predicted two new BC_6N allotropes, a Ccentered monoclinic BC6N (Cm-BC6N) and a primitive-centered monoclinic BC6N (Pm-BC6N).The lattice vibrations,elastic properties, ideal strength, theoretical hardness, and electronic structure of the predicted BC6N were investigated systematically.Our results reveal that Cm-BC6N is more favorable energetically than graphite-like g-BC6N above 20.6 GPa,which is lower than the transition pressures of r-BC6N, t-BC6N, and Pm-BC6N.Both Cm-BC6N and Pm-BC6N are indirect semiconductors with band gaps of 2.66 eV and 0.36 eV, respectively.Cm-BC6N exhibits the excellent ideal shear strength of 53.9 GPa in (011)[011], much greater than that of Pm-BC6N (25.0 GPa in (010)[101] shear direction), and Cm-BC6N shows a much lower anisotropy in shear strength than Pm-BC6N.The Vickers hardness of Cm-BC6N is estimated to be above 80 GPa, which is more outstanding than those of t-BC6N and r-BC6N.展开更多
基金Projects(59925513 50323007) supported by the National Natural Science Foundation of China+2 种基金 project(G1999065005) supported by the National Basic Research Program of China project(2003AA305670) supported by the Hi-tech Research and Development Program of China and supported by "Top Hundred Talents Program" of Chinese Academy of Sciences
文摘Carbon nitride films were deposited on Si (100) substrates using plasma-enhanced chemical vapor deposition (PECVD) technique from CH4 and N2 at different applied dc bias voltage. The microstructure, composition and chemical bonding of the resulting films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The mechanical properties such as hardness and elastic modulus of the films were evaluated using nano-indentation. As the results, the Raman spectra, showing the G and D bands, indicate the amorphous structure of the films. XPS and FTIR measurements demonstrate the existence of various carbon-nitride bonds in the films and the hydrogenation of carbon nitride phase. The composition ratio of N to C, the nano-hardness and the elastic modulus of the carbon nitride films increase with increasing dc bias voltage and reach the maximums at a dc bias voltage of 300 V, then they decrease with further increase of the dc bias voltage. Moreover, the XRD analyses indicate that the carbon nitride film contains some polycrystalline C3N4 phase embedded in the amorphous matrix at optimized deposition condition of dc bias voltage of 300 V.
文摘A kind of conductive and heating unit, which can reach a high surface electroheat temperature at a low voltage, was developed in view of the traditional electroheat coating which has a low surface electroheat temperature and an insufficient heat resistance of its binder. The coating molded electroheat carbon film(CMECF) was prepared by carbonizing the coating which was prepared by adding modified resin into flake graphite and carbon fiber, coating molded onto the surface of the heat resisting matrix after dried, while the hot pressing molded electroheat thick carbon film(HPMETCF) was prepared by carbonizing the bodies whose powders were hot pressing molded directly. The surface and inner microstructure of the carbon film was characterized and analyzed by SEM and DSC/TG, while electroheat property was tested by voltage-current volume resistivity tester and electrical parameter tester. The results show that, close-packed carbon network configuration is formed within the composite electroheat carbon film which yields a volume resistivity of 0.5×10 -210.0×10 -2Ω·cm at room temperature. The electroheat carbon film after anti-oxidizable treatment reaches a higher surface electroheat temperature than that of the existing electroheat coatings at a low voltage, and has excellent electroheat property, high thermal efficiency as well as stable physicochemical property. It is found that, at room temperature(19±2℃) and 22V for 5min, the surface electroheat temperature of the self-produced CMECF (m_ filler/m_ resin=1.8/1) reaches 112℃ while HPMETCF (m_ filler/m_ resin=3.6/1) reaches 265℃.
文摘以硅烷和氨气分别做为硅源和氮源,以高纯氮气为载气,采用热壁式管式反应炉,通过低压化学气相沉积(low pressure chemical vapor deposition,LPCVD)技术制备了氮化硅薄膜(SiN_x)。借助椭圆偏振仪研究了SiN_x薄膜的生长动力学,通过Fourier红外光谱和X光电子能谱表征了SiN_x薄膜的性质,并利用原子力显微镜观察了SiN_x薄膜的微观形貌。在其它工艺条件相同的情况下,SiN_x薄膜的生长速率随着工作压力的增大单调增加,原料气中氨气与硅烷的流量之比(R)对薄膜的生长速率有相反的影响。随着反应温度的升高,沉积速率逐渐增加,在840℃附近达到最大,随后迅速降低。当R<2时获得富Si的SiN_x薄膜(x<1.33);当R>4时获得近化学计量(z≈1.33)的SiN_x薄膜。
文摘1985,1989年A.Y.May与M.L.Cohen先后采用半经验公式和第一原理赝势算法(First principle pseudo energy calculation)计算并预言了硬度可与金刚石相媲美的β-C_3N_4材料的存在。之后,各国材料工作者对C_3N_4的材料性能以及实验合成进行了广泛的探索。新型超硬材料C_3N_4的研究日益成为材料科学的研究热点。本文根据介绍了C_3N_4材料的理论起源和研究现状。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21671168 and 21875205)the Hebei Natural Science Foundation,China(Grant No.B2015203096)the Qinhuangdao Science and Technology Support Program,China(Grant No.201703A014)
文摘Via structural searching methodology and first-principles calculations, we predicted two new BC_6N allotropes, a Ccentered monoclinic BC6N (Cm-BC6N) and a primitive-centered monoclinic BC6N (Pm-BC6N).The lattice vibrations,elastic properties, ideal strength, theoretical hardness, and electronic structure of the predicted BC6N were investigated systematically.Our results reveal that Cm-BC6N is more favorable energetically than graphite-like g-BC6N above 20.6 GPa,which is lower than the transition pressures of r-BC6N, t-BC6N, and Pm-BC6N.Both Cm-BC6N and Pm-BC6N are indirect semiconductors with band gaps of 2.66 eV and 0.36 eV, respectively.Cm-BC6N exhibits the excellent ideal shear strength of 53.9 GPa in (011)[011], much greater than that of Pm-BC6N (25.0 GPa in (010)[101] shear direction), and Cm-BC6N shows a much lower anisotropy in shear strength than Pm-BC6N.The Vickers hardness of Cm-BC6N is estimated to be above 80 GPa, which is more outstanding than those of t-BC6N and r-BC6N.
