Thesis (M.Eng.)--Chulalongkorn University, 2006

The synthesis of porous silicon nitride, one of the most promising structural materials for filter at high-temperature applications, from silica/ RF gel composite which was prepared by combining sol-gel and polymerization methods with the use of silica, precursor was investigated. Silica/RF carbon composite was converted into porous silicon nitride via the carbothermal reduction and nitridation. From the results, 3-Amino propyl trimethoxysilane was found to be a suitable silica precursor for the synthesis of porous silicon nitride. It was also found that aging time of silica/RF gel does not affect the porosity of silicon nitride. Solvent exchange with t-butanol and nolar ratio of silicon and carbon that are used in the preparation of silica/RF gel are the major factor affecting in the porosity of silicon nitride. The reaction time for the carbothermal reduction and nitridation is an important factor affecting the agglomeration and sintering of silicon nitride particles.