含フッ素ソーダホウケイ酸塩ガラスの多孔質化過程と二元型細孔構造の生成

概要

論文の詳細を見る
Leaching process in the preparation of porous glass from fluorine containing sodium borosilicate glass was intensively investigated under different conditions of phase-separation temperature, the thickness of specimens and the amount of acid leaching solution. Techniques employed are pore size distribution measurements and SEM observation with focusing on the leaching of SiO_2 component from the B_2O_3-rich phase. The pores formed in the inner part of specimens, after being treated with 0.5 mol/l sulfuric acid solution of 200 ml/(g-specimen)at 92±1℃ for 0.5h, had a smaller size than those formed in the surface layer of specimens. Those smaller pores contained a larger amount of silica-gel which precipitated from the B_2O_3-rich phase in the leaching process. This is the cause why a bimodal pore structure was inevitably obtained through the course of leaching:the silica-gel was removable by leaching with a larger amount of acid solution for a prolonged time. In the early stage of leaching process, the dissolution of the B_2O_3-rich phase proceeds, forming smaller pores with residual silica-gel, and the silica-gel is subsequently removed from the smaller pores resulting in enlargement. This diffusion-controlled process proceeds from the surface of the specimen to its inner part, indicating that a thin specimen is effective to accomplish the complete removal of the silica-gel with a minimum amount of the leaching solution.
1996-03-01