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Abstract: Cubic phase silicon carbide (3C-SiC) nanowires (labeled as “Sample 1”) with diameters ranging from 10nm to 80nm and lengths up to several micrometers were obtained by using CHI3, Si powder, and metallic Na as reactants at 230°C. In addition, SiC polyhedra (labeled as “Sample 2”) with smooth surfaces and diameters of 2–5μm were obtained by using the different amounts of the same reactants at 500°C. The room-temperature photoluminescence (PL) spectra of Sample 1 and Sample 2 show strong ultraviolet emission peaks centered at 360nm and 354nm, respectively. Thermal gravimetric analysis (TGA) curves reveal that the thermal stability (against air oxidation) of Sample 2 is better than Sample 1. The possible formation mechanisms of the products with distinct dimensions were briefly discussed. [Copyright &y& Elsevier]

Abstract: Silicon carbide (3C-SiC) nanocrystals were prepared starting from SiO2, C2H5OH, and metallic Mg in an autoclave at 200°C. X-ray diffraction patterns of the sample can be indexed as the cubic phase of SiC with the lattice constant a =4.357Å, in good agreement with the reported value (JCPDS card no. 29-1129; a =4.359Å). Transmission electron microscopy images show that the product mainly composed of nanowires with diameters in the range of 10–30nm and lengths up to tens of micrometers; High-resolution transmission electron microscopy images reveal that these 3C-SiC nanowires grow along [111] direction; As polyvinylpyrrolidine was added into the above reactant system, the final products obtained at 180°C were mixed 3C and 2H-SiC flakes. Thermal gravimetric analysis curves reveal that these two samples have thermal stability below 800°C, and room-temperature photoluminescence spectrum of the 3C-SiC sample show a strong emission peak centered at 403nm. [Copyright &y& Elsevier]

Nanocrystalline silicon carbide has been prepared via reacting magnesium silicide (Mg2Si) with carbon tetrachloride (CCl4) in an autoclave at 450–600°C. X-ray diffraction patterns of the products can be indexed as the cubic cell of SiC with the lattice constant, a=4.352 Å, in good agreement with a=4.349 Å (JCPDS card No. 75-0254). The transmission electron microscopy images show that the sample mainly consists of nanoparticles with an average size from 30 to 80 nm co-existing with a small fraction of nanorods and nanowires. Typically the nanorods range from 20 to 40 nm in diameter and the nanowires have diameters of 20 nm and lengths up to 10 μm. The Raman spectrum shows a characteristic sharp peak at 790 cm-1. X-ray photoelectron spectra (XPS) gives an atomic ratio of Si to C as 1.08:1.00 from the quantification of the peak intensities. Photoluminescence spectrum reveals that the SiC sample emits ultraviolet light of 328 nm. A possible mechanism and the influence of temperature on the formation of crystalline SiC are proposed. [Copyright &y& Elsevier]