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 μm. The surface area of the whisker containing SiC materials varies between 120 and 145 m 2 /g, while their pore volume is ca. 0.42 cm 3 /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 μm. The formation of nanotubes is accompanied by an increase in the surface area (up to 190 m 2 /g) of the silicon carbide materials.