Several Attempts On Si And Fe-based Nanomaterials

The thesis consists of three main parts: 1. research on the reaction of carbon nanotubes (CNT) with Si wafer at high temperature; 2. research on the preparation of Fe₂O₃ nanowires and the growth mechanism; 3. Hybrid nanocomposite of Fe nanoparticles on the surface of SiO₂ nanowires by sublimation route.The thesis investigated the growth mechanism of SiC nanowires generated from the reaction of CNT with Si wafer at high temperature, and then analyzed the stability of CNT and SiC nanowires in this system. First, CNT were prepared by CVD route, and then Si wafer and CNT were heated at high temperature to obtain SiC naniwires. The stability of CNT and that of SiC nanowires were compared in the reaction system. Firstly, both CNT and Si atoms reacted with the residual O in the tubular furnace, formed CO and SiO, and then two types of SiC nanowires were synthesized after CO reacted with SiO at different temperature, one is pure SiC nanowires and the other is SiC nanowires with a shell of SiO₂.A simple route was developed to synthesize the hybrid nanocomposite with Fe nanoparticles (NPs) dispersed on the surface of SiO₂ nanowires (NWs), where SiO₂ NWs with the diameter of 20-40 nm were produced by heating single-crystal silicon wafer, and Fe NPs in the size range of 3-20 nm were generated by heating Fe powders. The nucleation and growth of Fe NPs follows the solid-vapor-solid (S-V-S) mechanism, namely, Fe powders firstly sublime and then Fe atoms deposit on SiO₂ NWs to form Fe NPs.Fe₂O₃ nanowires and triangle nanocrystals were generated by oxidation Fe powders (28μm) and Fe nanofilm (500 nm and 1μm) in air at high temperature, respectively. The size of the bottom end of the nanowire is less than 600 nm, and its length is around 10μm; the size of the triangle nanocrystals is about 300 nm. The size of raw materials and reaction time has significant influence on the final product. The diffusion of Fe atoms determines the growth of Fe₂O₃ nanowires.