| 摘要 |
PURPOSE:To obtain porous glass having both high mechanical strength and heat insulating characteristic by increasing a void of the glass from its surface toward its center. CONSTITUTION:A sol is prepd. by mixing a hydrolyzate of ethyl silicate with fine particles of SiO2. After adding to the sol a foaming agent such as azo- dicarbonamide having a difference of specific gravity from the sol and dispersing the foaming agent in the sol, the concn. of the foaming agent in the sol is changed. When the concn. reaches a fixed distribution, a wet gel is obtd. by gelling the sol. A dry gel obtd. by drying the wet gel is calcined at about 300 deg.C, and a foamed dry gel is obtd. by expanding the dry gel. After adhering two faces of two sheets of the gel to each other at each surface of larger void, the product is fused to stick to each other by calcining at about 24hrs at about 1080 deg.C. Thus, porous glass having a dense surface but having larger voids toward its central part is obtd. |
