Preparation of β-SiC nanorods with and without amorphous SiO₂ wrapping layers

Preparation of β-SiC nanorods with and without amorphous SiO₂ wrapping layers Was achieved by carbothermal reduction of sol-gel derived silica xerogels containing carbon nanoparticles. The β-SiC nanorods with amorphous SiO₂ wrapping layers were obtained by carboreduction at 1650°C for 1.5 h, and at the end of 1.5 h the temperature was steeply raised to 1800°C and held for 30 min; they are typically up to 20 μm in length. The diameters of the center thinner β-SiC nanorods within the amorphous SiO₂ wrapping layers are in the range 10-30 nm, while the outer diameters of the corresponding amorphous SiO₂ wrapping layers are between 20 and 70 nm. The β-SiC nonorods without amorphous SiO₂ wrapping layers were produced by carbothermal reduction only at 1650°C for 2.5 h, and their diameters are in agreement with those of the center thinner β-SiC nanorods wrapped in amorphous SiO₂ layers. Large quantities of SiC rod nuclei and the nanometer-sized nucleus sites on cabon nanoparticles are both favorable to the formation of much thinner β-SiC nanorods. The formatrion of the outer amorphous SiO₂ wrapping layer is from the combination reaction of decomposed SiO vapor and O₂.