Synthesis of SiC precursors by a two-step sol-gel process and their conversion to SiC powders

Phenolic resin-SiO2 hybrid gels were synthesised as SiC precursors, with tetraethoxysilane (TEOS) and novolac phenolic resin as the starting materials, and oxalic acid (OA) and hexamethylenetetramine (HMTA) as catalysts. The influences of the molar ratio of OA/TEOS and prehydrolysis time on the sol-...

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Bibliographic Details
Published in:Journal of the European Ceramic Society 2000-10, Vol.20 (11), p.1853-1857
Main Authors: Li, Jinwang, Tian, Jiemo, Dong, Limin
Format: Article
Language:English
Subjects:
Applied sciences
Building materials. Ceramics. Glasses
Ceramic industries
Chemical industry and chemicals
Chemistry
Colloidal state and disperse state
Exact sciences and technology
General and physical chemistry
Powders
Structural ceramics
Technical ceramics
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Summary:Phenolic resin-SiO2 hybrid gels were synthesised as SiC precursors, with tetraethoxysilane (TEOS) and novolac phenolic resin as the starting materials, and oxalic acid (OA) and hexamethylenetetramine (HMTA) as catalysts. The influences of the molar ratio of OA/TEOS and prehydrolysis time on the sol-gel reaction were investigated. An optimum OA/TEOS ratio resulted in the shortest prehydrolysis time needed to form transparent gels. An increase of temperature accelerated the sol-gel reaction. The dried hybrid gels were yellowish transparent glassy solids with uniform microstructure composed of nanometre-sized particles. The conversion of the gels to silicon carbide powders was complete when heated at 1650 C for 30 min in vacuum. The oxygen and free carbon were 0.43 and 0.50 wt%, respectively, in powder produced from gel prepared with starting resin/TEOS of 0.143 g/ml. 11 refs.
ISSN:0955-2219
1873-619X
DOI:10.1016/S0955-2219(00)00055-8