Drying control chemical additives for rapid production of large sol-gel derived silicon, boron and sodium containing monoliths
AssigneeUniversity of Florida
InventorsLarry L. Hench, Gerard F. Orcel
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Abstract
Large sol-gel derived silicon-containing monoliths are prepared with the use of drying control chemical additives selected from the group consisting of glycerol, formamide, oxalic acid and acids of the formula C.sub.n H.sub.2(n-1) O.sub.2 N to control the ultrastructure of the gel solid and pore phases. Gelation, aging, drying, and densification of the sol-gel derived monoliths may be performed rapidly in tens of hours instead of tens of days without cracking, final densification at temperature of 800.degree. C. to 1200.degree. C. or less being possible. The silicon-containing monolith comprises a ternary SiO.sub.2 --B.sub.2 O.sub.3 --Na.sub.2 O system.
Claims8
A method for producing a crack-free sol-gel derived silicon-containing gel monolith comprising
- (1) forming a silicon-containing sol comprising SiO.sub.2 --B.sub.2 O.sub.3 --Na.sub.2 O in a proportion of 42 mole % SiO.sub.2, 30 mole % B.sub.2 O.sub.3 and 28 mole % Na.sub.2 O and a drying control chemical additive, said drying control agent enabling the formation of a crack-free gel monolith under drying conditions of elevated temperatures of between 70.degree. and 150.degree. C. for a period of between 18 hours and 96 hours;
- (2) casting said sol;
- (3) gelling said cast sol;
- and
- (4) drying said gelled cast sol to form a crack-free gelled monolith.
Dependencies are inferred from the claim text.