Silicon oxycarbide ceramics with reduced carbon by pyrolysis of polysiloxanes in water vapor

Ceramic foams and micro-beads from emulsions of a preceramic polymer

“…32 While, no Raman data were presented in that paper, it was shown, using solid state NMR spectroscopy, that the pyrolysis of polysiloxanes in the presence of water vapor remarkably modifies the atomic bonding configurations, and suppresses the precipitation of free-carbon in the pyrolyzed ceramic. It was proposed that the water-carbon reduction proceeds through the attacking by water of the carboncontaining organic groups, such as Si-CH 3 /Si-CH 2 -Si and Si-CH 3 (depletion of Si-C bonds), to form more Si-O bonds in the SiOC ceramic.…”

Boria Effects on the High Temperature Oxidation of Silicon Carbide

“…Volatilization of the organics in oxygenated and water vapor gas environments was found to reduce carbon retention in the heat treated glasses [78][79][80] . A preferable approach to reducing carbon retention in sol-gel coatings that would avoid SiC substrate oxidation during glass conversion is exposure of the coatings to hydrogen during glass conversion, which was found to decrease carbon concentration SiOC ceramics derived from silicone resin by the evolution of methane gas [81][82][83] .…”

“…The synthesis also does not replicate binary SiO2-B2O3glasses, primarily due to carbon retention from partial organic volatilization during the gel-to-glass conversion 75 . The retained carbon is expected to oxidize in the high temperature oxygen environment 80,82,83 and might affect oxygen transport through the glass coating during exposure. Boria volatilization is also expected to occur during high temperature exposure 57 , thus changing the glass composition over the duration of the test.…”

“…A free carbon phase was confirmed by Raman analysis. The issue of carbon retention is important to address since its oxidation is expected in the high-temperature oxidizing environment 77,80,82 that glass coatings will be exposed to during SiC oxidation testing.…”

Preparation of Silicon Oxycarbide Composites Toughened by Inorganic Fibers via Pyrolysis of Precursor Siloxane Composites

“…Typical SiOC also contains turbostratic graphite [1,4,9] which is responsible for its black color. Only under special synthesis conditions, completely graphite-free, colorless SiOC can be prepared [13]. SiOC synthesis via * corresponding author; e-mail: strachota@imc.cas.cz pyrolysis typically leads to porous products, so that it is difficult to obtain large, well-shaped, monolithic pieces.…”