Aerogel de Sílica: caracterização estrutural e estudo da propriedade da água adsorvida na superfície. / Silica Aerogels: structural characterization and property study of adsorbed water on the surface.

AUTOR(ES)
DATA DE PUBLICAÇÃO

1992

RESUMO

The synthesis of glasses using the sol-gel method appeared recently of great interest either from the technological or from the scientific point of view. We describe the process used to obtain pure vitreous silica (gel formation → hypercritical drying → densification) as well as some physical and chemical characteristics of the various products fabricated. Silica aerogels have been prepared by hydrolysis and condensation of sols of composition TMOS methanol - H2O with molar ratio TMOS: H2O = 4.1 and volume ratio of TMOS in solution of TMOS-methanol = 0,2; 0,3; 0,4; 0,5 and 0,6. Their structural properties such as true and apparent densities, BET surface area, total pore volume, pore size distribution, dielectric constant and loss have been systematically investigated as a function of the densification heat treatment. The relaxation properties of water adsorbed on the highly reactive surface have been studied by dielectric and nuclear magnetic resonance techniques as a function of the H2O coverage (0 < θH2O < 6) and temperature. The adsorption kinetics of the water was studied too in the aerogels with several heat temperature of sinterization.

ASSUNTO(S)

caracterização secagem hipercritica superficial drying aerogéis de sílica silica aerogels characterization preparação preparation

ACESSO AO ARTIGO

Documentos Relacionados