Dehydroxylation and nitriding of porous glass by means of water-soluble nitrogen-containing organic compounds

Abstract

Hydroxyl groups in reconstructed 96 % SiO2 glass are effectively removed by impregnating porous glass in an aqueous solution containing organic compounds that are thermally decomposable to produce reactive gaseous nitrogen species prior to consolidation of the porous structure in a nonoxidizing atmosphere. Infrared measurements show that glasses that have been impregnated in the porous state with urea, guanidine hydrochloride, or guanidine carbonate have essentially zero water content and furthermore contain nitrogen at sites normally occupied by oxygen atoms. Amide groups are absent in final glasses that have been prepared from porous glass containing high concentrations of guanidine hydrochloride, suggesting removal of hydrogen from such groups by interaction with chloride ions at elevated temperatures. The annealing points of such final glasses are markedly higher than those of untreated glasses.