Synthesis And Properties Of Silicon Carbide One-dimensional Nanostructures

One-dimensional silicon carbide(1D-SiC), as a third generation of wide band-gapsemiconductor, has been widely used for electronic and optoelectronic nanodevices,nanocomposites, hydrophobic devices, due to its wide band-gap, high thermal conductivity,high breakdown electric field, high electron drift velocity, high hardness, superior oxidation andcorrosion durability, etc. The key technical issue that has limited the application anddevelopment of the SiC nanodevices is the controlled growth of bulk synthesis of SiCnanowires, as well as their growth mechanism, physical and chemical properties, therefore,those work are important for the application of SiC nanowires.The1D-SiC nanomaterials have been synthesized via xerogel-carbothermal technology byhigh temperature reaction in Ar atmosphere. Moreover, we have obtained the3C-SiC tower-likenanowires (NWs) and6H-SiC ultra-long NWs by improving the gel craft, selecting differentcarbon sources (carbon black, bamboo charcoal). The phase, microscopic morphology andmicrostructures also have been investigated by using powder X-ray diffraction (XRD), fieldemission-scanning electron microscopy (FESEM), transmission electron microscope (TEM),selected area electron diffraction (SAED), etc. In addition, the vibration spectrum and opticband gap of samples have been studied by Fourier transform infrared spectrometer (FTIR), laserRaman spectrometer, ultraviolet visible spectroscopy of solid diffuse reflectance spectrometer(UV-Vis DRS). The growth mechanism, high temperature anti-oxidation capacity andphotocatalytic activity of the as-synthesized SiC NWs have been discussed. The main researchconclusions of this paper are as follows:1D tower-like SiC NWs have been synthesized from carbon black and silica xerogel. It isindicated that the NWs are single crystalline β-SiC with non-uniform distribution of stackingfaults and micro-twins along the preferred growth direction [111]. The3C-SiC NWs of variousmorphologies and sizes have been obtained in different temperatures (1500℃、1550℃、1600℃) or C/Si molar ratios (0.5-3). And the optimize craft of tower-like NWs would be1550℃, C/Si=1,5h. The vapor solid epitaxial (VSE) mechanism was proposed to explain the growth process, i.e. the growth of core stem NWs by VS reaction, then formation of thetower-like nanostructures by epitaxial growth.3C-SiC,6H-SiC NWs have been synthesized from bamboo charcoal and silica xerogelduring high temperature carbothermal condition. It has shown high efficient synthesis of SiCNWs, which may be the result of the continuous supply of the vapors due to high-porosity inbamboo charcoal. The SiC NWs of various morphologies and sizes have obtained in differenttemperatures or C/Si molar ratios. And the optimize craft of6H-SiC NWs synthesis would be1450℃, C/Si=1,5h. The gas supersaturation has influence on the formation of differentcrystal-structures and morphologies of SiC NWs. The growth of3C-SiC and6H-SiC NWs couldbe the result of different supersaturations, and the screw dislocation model was proposed toexplain the growth process based on VS reaction. Furthermore, we have found some uniquemorphology of the products, such as “mutational junction” NWs, nanobelts, Y shape NWs, etc.Moreover, the paper has studied the FTIR, UV-Vis DRS, photocatalysis and oxidationdurability, etc. The presence of residual carbon in the as-synthesized SiC NWs has beeninvestigated by FTIR. And the UV-Vis DRS results showed that SiC NWs was a indirecttransition semiconductor and the band gap energy was2.86eV. The as-synthesized3C-SiCNWs has strong photocatalytic activity for methylene blue solution, the de-coloration rate isabove90%. In addition,3C-SiC NWs possess better oxidation durability than6H-SiC NWsduring argon atmosphere.