Fig. 3.

²⁹Si solid-state NMR measurement of silica aerogel. (a) Prior to epoxy modification, Si—O substitutions were 55.9% in Q⁴, 39.0% in Q³, and 5.1% in Q², and their corresponding characteristic peaks appeared at −110 ppm, −102 ppm, and −92 ppm, respectively. (b) Post-epoxy modification, Si—O substitutions were 15% in T³ and 7.3% in T², and their characteristic peaks appeared at −66 ppm and −57 ppm, respectively. The proportion of Q³ dropped to 14.6%.