Nitridation of SiO2–B2O3 aerogels

SiO2–B2O3 aerogels have been prepared by drying wet gels at a supercritical condition for ethanol in an autoclave. Aerogels have been nitrided for 6 h in flowing ammonia at the temperature of 1200 °C. It has been found that the amount of nitrogen incorporated in these aerogels always exceeds 20 wt%. This is a much higher value compared with the amount of nitrogen incorporated in a pure silica aerogel nitrided at the same conditions. The specific surface area of SiO2–B2O3 aerogels has been between 312 and 359 m2/g. After nitridation some shrinkage of aerogels has been observed and the surface area decreases about 20%. In FTIR spectra of SiO2–B2O3 aerogels a typical bands for SiO2 are observed. After nitridation a shift and broadening of 1100 cm−1 band to lower wavenumbers indicates that Si–N and B–N bonds are formed in nitrided aerogels.