Patent ID: 7181862
Filing Date: 2007-02-27
Classification: C03B,C03C

Abstract:
1. Process for the production of glassy articles comprising the following operations: a) preparation of an aqueous or hydroalcoholic solution, or suspension, of at least a compound having the formula wherein M is a cation of an element belonging to the 3 rd , 4 th , or 5 th Group of the Periodic System, n means the cation valence, X is R 1 or OR 1 , R 1 being the same or different from R, m is zero or an integer number lower than 3, R and R 1 are hydrocarbon radical having a carbon atom number up to 12; b) hydrolysis of the above said compound, either in solution or in suspension, to obtain a sol; c) eventual addition in colloidal suspension of possible M d) sol gelling; e) substitution of gel pore solvent with a non protic solvent; f) gel setting in a pressure chamber; g) inert gas fluxing into the pressure chamber; h) pressure chamber heating over a programmed time period to achieve predeterminate temperature and pressure values, lower than the relevant critical value of the gel solvent, and evaporation thereof; i) depressurization of the pressure chamber with vapor discharge; j) pressure chamber washing by an inert gas; k) cooling dried gel and removal thereof from the pressure chamber; l) dried gel syntherization by heating at a prefixed temperature to form a glassy body without any cracking.