Journal
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
Volume 91, Issue 10, Pages 3298-3302Publisher
BLACKWELL PUBLISHING
DOI: 10.1111/j.1551-2916.2008.02603.x
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Funding
- Natural Science Foundation of Fujian Province of China [E0510002]
- National Natural Science Foundation of China [50532010]
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Partially ethynyl-substituted ethynylhydridopolycarbosilane (EHPCS) is prepared by Grignard coupling of chloromethyl-trichlorosilane, chloromethylmethyldichlorosilane, and ethynyl-magnesium bromide, followed by reduction with lithium aluminum hydride. The as-synthesized EHPCS, with a hyperbranched structure and an approximate formula of [SiH1.35(CH3)(0.37) (C CH)(0.28)CH2]n, has been characterized by GPC, FT-IR, and H-1, C-13, and Si-29 NMR. The EHPCS can be cured readily in an inert atmosphere at 140 degrees C for 6 h. Pyrolysis behavior and structure evolution of the cured EHPCS were studied by means of thermal gravimetric analysis-differential scanning calormetry, FT-IR, X-ray diffraction, and elemental analysis. It is suggested that hydrosilylation, ethynyl group polymerization, dehydrocoupling, and demethanation are involved in the cross-linking of EHPCS. The polymer-ceramic conversion is complete at 900 degrees C, and it gives a stoichiometric and amorphous silicon carbide (SiC) with a yield of 78%. Further beating at 1200 degrees C induces partial crystallization, forming locally ordered SiC4. The characteristic peaks of beta-SiC are observable above 1600 degrees C.
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