Preparation And Characterization Of Carbon And Silicon Carbide Low-dimensional Nanoscale Materials

Carbon and silicon carbide low-dimensional nanomaterials have become the focus of intensive research owing to their novel physical, chemical, and biological properties as well as the potential applications in nanodevices. It was of not only their importance in understanding fundamental physical phenomenon, e.g. electron transportation, but also the promising applications such as interconnects and functional building blocks for novel electrical and optical nanodevices. This thesis consistes of two sections: First, the research of low-dimensional carbon nanoscale materials, including the effct of systhesis and characterization of one-dimensional carbon nanoscale materials by metal catalyst precursor treated under hydrothermal conditions, and depesition of nanocrystalline diamond films by double bias assisted hot filament plasma enhanced chemical vapor deposition; Second, systhesis, growth mechanism and PL characterization of silicon carbide nanowires/ nanorods by thermal vapor method, hydrothermal method and temple method. The research is fundamental and pioneering, and is of great significance on theory and application. The significant results achieved in this dissertation are given as below:Firstly, synthesis ofβ-Ni(OH)₂ andγ-Fe₂O₃/SiO₂ as catalyst precursors by hydrothermal method. The research results demonstrate that Ni(OH)₂ treated under hydrothermal condition shows a nanosheet structure, which face diameter is about 80nm, thickness is 15nm. Theγ-Fe₂O₃/SiO₂ composites synthesized by hydrothermal method have the diameter of about 30nm. The effect of systhesis and characterization of one-dimentional carbon nanoscale materials by metal catalyst precursors treated under hydrothermal conditions have been tested by cracking the acetylene. The highest CNTs yield ofγ-Fe₂O₃/SiO₂ as catalyst precursor is 1000%, and that ofβ-Ni(OH)₂ as the catalyst precursor is the 2800%, which is ten times than that without treatment by hydrothermal method. In addition, the oriented CNFs have been sthesized on the -Ni(OH)₂ films.Secondly, the nanocrystalline diamond films have deposited in CH4 gas by double bias voltage assisted hot filament plasma enhanced chemical vapor deposition system at radio frequency of 80W, hot filament current 60A, substrate negative bias voltage -120V, grid bias voltage 100V. The NCD film has a higher nucleation density and smooth surface, and grain size is about 40 nm. The effects of growth parameters, including frequency power, bias voltage and hot filaments are investigated.Thirdly, large-scale SiC nanowires have been systhesized from activated carbon, CNTs, CNFs and carbon films by thermal vapor method without any metal catalysts. The SiC nanowire is the diameters of about 50-70nm and tens of micrometers long. The nanowires are corel-shell structure, which wrapped by amorphous SiO₂. The nanowires axes lie along the [111] direction. The growth mechanism is analysed by change the preparation parameters, such as reaction temperature, time and silicon sources.Fourthly, single crystalline SiC nanorods with the diameter of about 40nm and length of 1μm have been prepared under the hydrothemal conditions of 470℃and 9.5MPa by silicon carbide and silica. The research results demonstrate that the SiC nanorods samples are composed of single crystallineβ-SiC and residual carbon nanoscale grains. The formation and growth of the SiC nanorods are explained according to the oxide-assisted growth mechanism. PL spectrum of the SiC nanorod sample shows that PL peak center at 445nm is strong and asymmetrical. And the range of PL emission peak is 400-460nm.Finally, large-scale pure SiC nanowires/nanorods have been synthesized by anodic aluminum oxide template assisted thermal vapor and hythermal methods. SiC nanowires have been synthesized from monoxide and activated carbon powders by anodic aluminum oxide template assisted thermal vapor method at 1400℃for 2h. The results show that the SiC nanowire is the diameters of about 70nm and tens of micrometers long. The nanowires are corel-shell structure, which wrapped by amorphous SiO₂ with the thickness of 3nm. The nanowires axes lie along the [111] direction. PL spectra of theβ-SiC nanowires shows that PL peak center at 400nm is strong and asymmetrically broad. And the range of PL emission is 330-600nm. Large-scale SiC nanorods have been prepared from SiC and SiO₂ powders by AAO template assisted hydrothermal method at 470℃, 7.8 MPa for 2h. The results show that the SiC nanorod is the diameters of about 70nm and several micrometers long. The nanorods are corel-shell structure, which wrapped by amorphous SiO₂ with the thickness of 3nm. With the hythermal temperature rised, the longth of SiC nanorods increases, and the diameter of nanorods decreases.