3.3. Specific surface area
Fig. 5 illustrates the specific surface area of the silica gel and the
colloidal nanosilica samples synthesized at different sonication
times. As can be seen, there is a rising trend in the specific surface area
with a much higher slope during the first 5 min of sonication. The
specific surface area of the silica gel was measured 190.08m2/g,
whereas it was about 369.60m2/g for the colloidal nanosilica
obtained after 60min of sonication. Since specific surface area has
an inverse relationwith particle size, the variations of specific surface
area are consistent with the results of DLS analysis.