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Porous Silicon Oxycarbide Glasses
Author(s) -
Singh Anant K.,
Pantano Carlo G.
Publication year - 1996
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1996.tb09035.x
Subject(s) - ammonium hydroxide , mesoporous material , materials science , thermal stability , chemical engineering , specific surface area , carbon fibers , porosity , silicon , pyrolysis , hydrolysis , sol gel , argon , mineralogy , composite number , composite material , nanotechnology , catalysis , chemistry , organic chemistry , metallurgy , 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 ∼275 m 2 /g and an average pore size of ∼30 Å 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 2 /g were retained at 1200°C under an argon atmosphere. 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.