Synthesis of ordered mesoporous silicon oxycarbide monoliths via preceramic polymer nanocasting

Highly ordered mesoporous silicon oxycarbide (SiOC) monoliths have been synthesized using liquid poly(hydridomethylsiloxane) (PHMS) as starting preceramic polymer and mesoporous carbon CMK-3 as direct template. Monolithic SiOC-carbon composites were generated via nanocasting of PHMS into CMK-3, pressing without any additive, cross-linking at 150 °C under humid air and subsequent thermolysis at 1000 or 1200 °C under argon atmosphere. The carbon template was finally removed by the thermal treatment at 1000 °C in an ammonia atmosphere, as a result of the generation of monolithic SiOC ceramics with ordered mesoporous structures. The products were characterized by scanning electron and transmission electron microscopes, X-ray diffraction, Fourier transformation infrared spectrometer, X-ray photoelectron spectroscope and nitrogen absorption–desorption analyzer. The as-prepared SiOC monoliths exhibited crack-free, ordered 2-dimentional hexagonal p6mm symmetry with high specific surface areas. With increasing the calcination temperature, the ordered mesoporous structure was still remained and the specific surface area just had a slight reduction from 616 to 602 m2 g−1. Moreover, the porous SiOC monoliths possessed good compression strengths and anti-oxidation properties.

Crack-free, high mechanical strength, ordered mesoporous silicon oxycarbide (SiOC) monoliths have been synthesized using poly(hydridomethylsiloxane) as starting preceramic polymer and mesoporous carbon CMK-3 as hard template, via nanocasting, pressing, crosslinking and subsequent pyrolysis under different atmospheres..Figure optionsDownload as PowerPoint slideHighlights
► This is the first attempt to synthesize ordered mesoporous SiOC monoliths.
► The monoliths exhibited crack-free, well ordered hexagonal p6mm symmetry.
► The SiOC monoliths showed high specific surface areas above 600 m2 g−1.
► The products possessed good mechanical strengths and high oxidation resistance.