Porous silicon oxycarbide glasses
- Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering
High-surface-area silicon oxycarbide gels and glasses were synthesized from mixtures of methyldimethoxysilane (MDMS) and tetraethoxysilane (TEOS) through acidic hydrolysis and condensation. A surface area of {approximately}275 m{sup 2}/g and an average pore size of {approximately}0 {angstrom} was obtained for a 50% MDMS-50% TEOS glass at 800 C under a flowing argon atmosphere. The average pore size was increased by aging the precursor gels in ammonium hydroxide. The increased average pore size and the higher strength of the mesoporous gel network enhanced the surface-area stability of the glasses: in this case, surface areas >200 m{sup 2}/g were retained at 1,200 C under an argon atmosphere. {sup 29}Si MAS NMR spectra revealed that an oxycarbide structure was established in the mesoporous glasses obtained after pyrolysis of the aged gels. The role of carbon was demonstrated by comparing the surface-area stability of the oxycarbide glasses with that of pure silica and that of oxycarbide glasses where all the carbon groups were removed through low-temperature plasma-oxidation treatments. In the absence of carbon, the thermal stability of the surface area decreased dramatically.
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States)
- OSTI ID:
- 413321
- Journal Information:
- Journal of the American Ceramic Society, Vol. 79, Issue 10; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
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