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Chemically derived ceramic composites

Thesis/Dissertation ·
OSTI ID:6883084
Silicon carbide was made from various organosilane precursors by crosslinking and pyrolyzing them in an inert atmosphere. Crosslinking of these silane precursors was studied by various means. Pyrolyses of the silane precursors were carried out and increased ceramic yield after crosslinking was shown as compared with uncrosslinked precursors. The ceramic yields by TGA ranged from 10-70% depending on the precursors and the crosslinking treatments. Partially densified sol-gel-derived silica monoliths were impregnated with the silane precursors while the silica monoliths were still highly porous. Diamond microhardness increased 2-3 times from an unimpregnated gel-derived silica monolith. Optical and mechanical properties, and porosity data are presented. Using these silica precursors and the processing techniques to obtain ..beta..-SiC, molecular composites of SiC with SiO/sub 2/, with TiO/sub 2/ and with Al/sub 2/O/sub 3/ were made in monoliths and powder forms. The silica as a matrix was derived from a tetralkoxysilane via sol-gel reactions. The monolithic composite of molecularly dispersed SiC phase in the SiO/sub 2/ gel matrix showed the hardening effect by SiC phase. The molecular composite powders of SiC/Al/sub 2/O/sub 3/ and SiC/TiO/sub 2/ showed suppressed crystallization of either phase after heating to 1400/sup 0/C.
Research Organization:
Florida Univ., Gainesville (USA)
OSTI ID:
6883084
Country of Publication:
United States
Language:
English