Preparation of Monolithic Silica Gels by Hypercritical Drying and Their Thermal Characteristics

概要

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Monolithic silica gels without cracking were prepared by supercritical drying of methanol from a homogeneous mixture of tetramethyl orthosilicate (TMOS)-methanol (MeOH)-water (H-O) system. The preparation of monolithic silica gel was highly effected by H-O/TMOS ratio in the hydrolyzed solution. Monolithic silica gels were composed of fine particles containing SiOH-groups. They contained many open pores, which was confirmed by N-gas permeation experiments. These gels vitrified at 1100C. The volatile matters in the monolithic gel were eliminated through open pores by firing, and the densification of the gel took place by dehydration of SiOH-groups, where a volumetric shrinkage of about 60% was accompanied on firing at 1100C. Finally the monolithic silica bulk became silica glass in structure by densification. The obtained silica bulk was optically transparent without cracks or bubbles.
東海大学の論文