Synthesis And Characterization Of Silicon Carbide Whisker Arrays Prepared By Thermal Evaporation Method

SiC nano-whiskers have not only a wide band-gap, high critical breakdown electrical field, high thermal conductivity, high charge carrier mobility, but also a series of excellent characters of both whisker and one-dimensional nanostructures in electrical and thermal conductivity, magnetic and mechanical performance which are quite different from the ordinary bulk materials, leading to important applications in optics, composite materials, sensors, catalysts and so on. With the ordered array-structure, SiC nano-whiskers may also become a new generation of high resolution display materials and luminescent materials. It is of great significance to study the preparation, performance, growth mechanism and application of SiC nano-whisker arrays in both the scientific research and engineering application.This paper is focused on the preparation of the one-dimensional SiC nano-whisker arrays. By using thermal evaporation of silicon melt in the absence of catalyst, the nano-SiC whisker arrays with different structures and morphologies were synthesized on carbon fibers and graphite plates which act as the templets and carbon sources. The influences of the experiment conditions on the morphology and structure of the array were investigated. Characterizations including composition, structure, morphlogiy and photoluminescence were carried out, based on which, the growth mechanisms are discussed.The results show that the different carbon sources and vacuum levels have significant implications with the morphology and array structure of the nano-SiC whiskers. Tube-brush shaped array structure of SiC nano-whiskers with needle-like tips were obtained around carbon fiber axes, but hexagon prism shaped SiC nano-whiskers less regularly arrayed were grown on the graphite plates. The yields were all high in both cases. For tube-brush shaped arrays on carbon fiber low-vacuum system is needed, but no matter in low or high vacuum, hexagon prism shaped SiC whiskers on graphite plate can be obtained.Growth temperature has little effect on the experimental results. Different temperatures have an impact on the growth pace, which is in turn reflected in the length of the whiskers. During different reaction time, the products have obvious distinctions in the appearance, which suggests the different stages of the reaction. From the different appearances and the experiment facts, the formation mechanisms of theSiC nano-whiskers with different morphologies are proposed. Furthermore, some other products with very special morphologies were also prepared in various experimental conditions, suggesting that preparation method, the state of carbon, the surface finish of templets, vacuum and flowing gas are related to the morphologies of products.The room temperature photoluminescence spectra were measured, and the blue shift of the PL peaks are demonstrated. This may be ascribed to the quantum size effect of the nanometer dimension of the SiC whiskers. However, further study remains necessary.The catalyst free preparation of SiC nano-whisker arrays on carbon fibers and graphite plates by thermal evparation of silicon melt is a novel and simple technique. The raw materials are easy to find, and the products are of array structure rather than random whiskers. It is regarded as a valuable and significant exploit in nanostrucutred materials.