Oxynitride glasses prepared by densification of nitrided silica aerogels

Silica aerogels were nitrided by ammonia treatment at temperatures ranging from 700 degreesC to 1300 degreesC. It was found that the amount of nitrogen incorporated in silica aerogel depends on the final temperature of ammonolysis and on the time of heat treatment. The specific surface area of nitrided aerogels remains large and decreases with the temperature of ammonolysis and with nitrogen content. Nitrided aerogels can be converted into dense homogeneous oxynitride glasses containing 8.4-13.0 wt% of nitrogen by heat treatment at 1600 degreesC in vacuum or in nitrogen atmosphere. The spectra of the Fourier transform infrared spectroscopy (FTIR) reveal that Si-N bonds exist in nitrided aerogels as well as in oxynitride glasses.