Synthesis And Characterization Of Silicon Carbide And Titanium Carbide Nanomaterials

On the basis of comprehensive and thorough investigation of literatures concerning the developments of silicon carbide(SiC)and titanium carbide(TiC)nanomaterials synthesis and applications,in this dessertation,high-temperature pyrolysis transition metal organic compounds and reduction route were used to prepare the above mentioned functional materials with interesting structures,such asβ-SiC nanowires and TiC hollow spheres.Combining the experimental analysis results and the study of the related reports,some proper theories are referred to discuss the growth mechanism of as-prepared nanomaterials.Moreover,the as-obtained product was measured to have a BET surface area of 78.30 m²/g and pore volume of 0.04 cm³/g.The main contents can be summarized as follows:1.β-SiC nanowires were successfully produced by reduced silicon tetrachloride and high-temperature pyrolysis transition metal organic compounds ferrocene with metallic Na at 500℃in a stainless-steel autoclave.X-ray powder diffraction pattern results indicated that the product was face-centered cubic SiC with a lattice constant a =4.36(?)that is close to that of the reported value(JCPDS card No.75-0254,a= 4.358(?)).Transmission electron microscopy photographs showed theβ-SiC nanowires have typical diameters of 15-50 nm,and lengths up to several tens micrometers,which have a preferential grow along the[111]direction.According to the experimental analysis results and the study of the related reports,the possible growth mechanism of the nanowires is vapor-liquid-solid(VLS)mechanism. Ferrocene in this reaction acted as a carbon source,also because it contains iron element,may play a catalytic role in nanowire growth,which might be utilized for the synthesis of the carbides nanomaterials.2.The co-reduction route were developed to synthesis TiC using TiCl₄,C₂Cl₄ (Tetrachloroethylene)and metallic sodium as reactants in a stainless steel autoclave at 240-400℃X-ray powder diffraction pattern results indicated that the product was face-centered cubic TiC with a lattice constant a=4.32(?)that is close to that of the reported value(JCPDS card No.75-0254,a=4.358(?)).Transmission electron microscopy photographs showed the hollow spheres have an average outer diameters ranging from 70 to 110 nm and shell-thickness of about 10 to 20 nm.Selected area electron diffraction patterns showed that the samples were polycrystalline TiC.The morphology of the as-prepared sample was further characterized by FESEM,and the typical images are shown that besides the irregular particles,the proportion of the spheres with diameters of～70-110 nm in the product is approximately 70%.The lattice fringes can be clear seen from high-resulution transmission electron microscopy photographs,which revealing its high crystallinity.The inter-planar spacing is about 2.50(?),which corresponding to(111)spacing of face-centered cubic TiC.X-ray photoelectron spectra further indicate that the final product was relatively pure TiC.Its possible formation mechanism was also tentatively discussed.In addition,a nearly complete oxidation of the TiC product was achieved under air atmosphere in a tube-furnace.Crystalline TiO₂ nanoparticles with anatase or rutile phases were selectively prepared at different target temperature.