High Surface Area Silicon Carbide Whiskers and Nanotubes Nanocast Using Mesoporous Silica

We report here the formation of high surface area silicon carbide materials comprising whiskers and nanotubes via a synthesis route, which utilizes mesoporous silica as sacrificial solid template. The silicon carbide materials are obtained via carbothermal reduction of mesoporous silica/carbon (i.e., SBA-15/sucrose) composites. Varying the carbothermal reduction conditions (i.e., temperature or duration) readily modifies the morphology of the silicon carbide so as to obtain whiskers or nanotubes. The whiskers, which grow in the [111] direction, are achieved by subjecting the mesoporous silica/carbon composites to carbothermal reduction at high temperature (1250 or 1300 C) for reduction periods of up to 14 h. For reduction periods of up to 14 h, using the higher temperature (1300 C) optimizes whisker formation. The diameter of the whiskers is 50-90 nm and their length is typically greater than 20 (mu)m. The surface area of the whisker containing SiC materials varies between 120 and 145 m2/g, while their pore volume is ca. 0.42 cm3/g. Increasing the carbothermal reduction period to 20 h, at 1250 or 1300 C, results in the formation of solid SiC nanotubes of diameter 60-100 nm and length greater than 10 (mu)m. The formation of nanotubes is accompanied by an increase in the surface area (up to 190 m2/g) of the silicon carbide materials