Skeletal density aerogel

Silica aerogels are amorphous materials. They have a skeletal density, as measured by Helium pycnometry [102] 2 g cm, close to that of amorphous silica (2.2 g cm ). They typically have a pore volume above 90% of their whole monolith volume. Some ultraporous... 

Ayral A, Phalippou A, Woignier T (1992) Skeletal density of silica aerogels determined by helium pycno-metry. J Materials Science 27 1166-1170... 

Figure 13.20. A. Poly[acrylonitrile]-crossliiiked silica decorated with Si-AIBN (pt = 0.47 gcm", 60%, w/w, polymer, 228 g 60%, v/v, empty space). B. Pure silicon carbide aerogel by pyrolysis of the poly[acrylonitrile]-crosslinked silica shown in A. (pi, = 0.97 gcm, skeletal density Ps = 3.12 gcm , 39 g" , 69%, v/v, empty...

Single sample, average of 50 measurements in brackets calculated skeletal densities based on the thermogravimetric analysis data of the next column and the skeletal densities of native MOx, RF and polyurea (PUA) aerogels prepared independently (see text). 

The skeletal densities of the solid phases were evaluated by the maximum entropy method [72] and found to be po = 2.09 0.02 g/cm and 2.19 0.02 g/cm for silica glass. These differences come from the presence of nonbridging oxygens on the pore-matrix interface in the aerogels causing lengthening of the average Si-O bonds [73] (Table 20.3). 

Figure 20.19. Skeletal and bulk density for light sono-aerogels held for 10 h at temperatures up to 1,100°C. Reprinted with permission from [68],...

The mechanical behavior of X-aerogel depends on their mass density. The effect of density on the stress-strain relationship was investigated at strain rates in the range 300-400 s X-VOx specimens with different densities were compressed on the SHPB to determine the effect of density on the stress-strain relationships. X-aerogel specimens with higher densities were prepared by applying a thicker conformal polymer coating on the skeletal framework. 

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