Role of Pores in the Carbothermal Reduction of Carbon−Silica Nanocomposites into Silicon Carbide Nanostructures

Abstract

Silicon carbide nanostructures were synthesized by carbothermal reduction of carbon−silica (C−SiO2) nanocomposites. C−SiO2 nanocomposites with C/SiO2 molar ratios of 1.90−4.21 were used in this study. Thermogravimetric analysis, nitrogen sorption, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and infrared spectroscopy were used to characterize C−SiO2 nanocomposites and SiC products. Highly crystalline SiC nanoparticles and nanofibers (CS-3.28 and CS-4.21) were obtained from mesoporous C−SiO2 nanocomposites with the carbon content greater than a C/SiO2 stoichiometric ratio of 3 (e.g., C/SiO2 = 3.28 and 4.21 by mole), and they had a BET surface area of 83.0−76.7 m2/g after unreacted silica and carbon were removed. In contrast, SiC was not formed in the mesoporous C−SiO2 nanocomposites with a lower carbon content (e.g., C/SiO2 = 1.91 and 2.51 by mole). However, when such mesoporous nanocomposites were infiltrated with a small amount of carbon, SiC nanoparticles and nanofi...