From Gel to Glass

The aerogel treated at 500°C practically abides by the condition of one order of magnitude for the ratio /a, corresponding to a D value obtained to standard preparation fotmd for acid-catalyzed classic silica aerogels [82]. Densification studies have shown that dense sono-aerogels can be readily converted into dense glasses, provided sufficient care is 

The spherical aggregates of 3 nm radius particles easily sinter above 700°C due to the viscous flow of these small clusters. 

The sintering is more complex at the length scale of 10 nm because of the closed porosity that contains residual OH groups. 

The elastic modulus of dense sono-aerogel is several orders of magnitude higher than for classic ones (Chap. 22). Table 20.9 summarizes results obtained for the bulk modulus and apparent density. 

A device debvermg to the system 0.6 W cm of ultrasound power was employed for 500 s and 250 s, respectively, for the STMH and STMM samples. They were heat-treated at 600°C, 900°C, and 1,100°C. 

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