Silicon nitride synthesis from electrospun silica/carbon composite nanofibers

Abstract

The synthesis of silicon nitride, one of the most promising structural materials for high-temperature and high mechanical-stress applications, from electrospun silica/carbon composite, whereas source of carbon including either pyrolyzed polymer or carbon black is investigated. Morphology of the starting materials is in form of gel and fibers, which are prepared by combining sol-gel and electrospinning method. Silica/carbon composite is converted into silicion nitride via the carbothermal reduction and nitridation. For preparation of silicon nitride form pyrolyzed silica/polymer composite, 3-Amino propyl trimethoxysilane and low-molecular weight PVP are found to be the suitable precursors for silicon and carbon, respectively. It is also found that aging time and morphology of the starting materials (e.g. gel and fibers) are important factors affecting the subsequent nitridation. The silica/polymer composite in form of fibers is not appropriate for converting to silicon nitride because of inadequate free carbon content. For the use of silica/carbon black composite, silicon nitride/silicon carbide composite can be prepared in form of fibers. The obtained products also remain the same morphology as the as-spun silica/carbon black composite fibers and have the average size in the range of 0.4-0.65 micro m. Carbon-to-silica ratio and aging time of the starting material are the major factor affecting mechanism of the carbothermal reduction and nitridation