Chemical composition aerogels

The heat transfer via the solid backbone of aerogels depends on the backbone stmcture and connectivity (Chap. 21), and its chemical composition. For a given temperature gradient within an aerogel, heat is transferred by diffusing phonons via the chains of the aerogel backbone, where the mean free path of the phonons is far below the dimensions of the mostly amorphous, dielectric primary particles. Within the primary particles, the thermal conductivity is a property of the backbone material and is described in terms of the phonon diffusion model by Debye [7], i.e., ... 

Chemical composition, synthesis conditions, and initial BET surface areas of aerogel and... 

IR spectra obtained from An promoted catalysts are presented in Fig.l. The chemical composition of the silica aerogel is characterized by the following set of absorption bands 470, 808, 1100, and 1640 cm. Bond vibrations at 1100 cm are Si-O-Si asymmetric stretching vibrations. Absorption bands at 808 and 470 cm can be assigned to bending vibrations of Si-O-Si and O-Si-O gronps. A weak absorption band at 1640 cm appears because of the presence of adsorbed water on the surface of the samples. 

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