The native silica aerogels were prepared using tetramethoxysilane via base-catalyzed cross-linking reactions [22]. These silica aerogels are composed of interconnected particles with diameter ranging from 5 to 10 nm. Mesopores with
diameters of around 50 nm are formed during the cross-linking of the particles.
Following the formation of the silica aerogels, the gels are washed with ethanol,
propylene carbonate and a mixture of propylene carbonate and poly(hexamethylene
diisocyanate). After the cross-linking process with di-ISO, the interconnections
between the silica particles are observed to become wider as compared with the
image on the left. This significantly strengthens the robustness of the novel silica
Fig. 6.6 a Comparison of SEM images showing different microstructures of a native silica
aerogel (left, density = 0.169 g cm
−3
) and a di-ISO cross-linked silica aerogel composite (right,
density = 0.380 g cm
−3
). b Photograph of mechanically strong silica aerogels that can withstand
15 kg load. Adapted with permission from Ref. [21]. Copyright 2002 American Chemical Society
6.2 Silica-Based Gels
197
diameters of around 50 nm are formed during the cross-linking of the particles.
Following the formation of the silica aerogels, the gels are washed with ethanol,
propylene carbonate and a mixture of propylene carbonate and poly(hexamethylene
diisocyanate). After the cross-linking process with di-ISO, the interconnections
between the silica particles are observed to become wider as compared with the
image on the left. This significantly strengthens the robustness of the novel silica
Fig. 6.6 a Comparison of SEM images showing different microstructures of a native silica
aerogel (left, density = 0.169 g cm
−3
) and a di-ISO cross-linked silica aerogel composite (right,
density = 0.380 g cm
−3
). b Photograph of mechanically strong silica aerogels that can withstand
15 kg load. Adapted with permission from Ref. [21]. Copyright 2002 American Chemical Society
6.2 Silica-Based Gels
197