Asahi Denka Kogyo Kabushiki Kaisha

M. Watanabe Co., Ltd.

Hirofumi Uehara

Hiroshi Morita

Hiroyuki Watanabe

Masaki Kusuhara

Jinichi Omi

Kunio Sugiyama

Shuichi Tada

Tadahiro Nakada

Keiko Sanpei

A hydrous silica gel is dehydrated by freezing, thawing, and removing water separated by thawing, thereby yielding silica particles. In addition, the silica particles thus formed is washed and fired, thereby producing a synthetic quartz glass power. A water glass is dealkalized, an oxidizing agent and an acid are added, the mixture thus formed is passed through a hydrogen type cation exchange resin, the aqueous silica solution thus formed is then gelled, and the gelled material is then washed and fired, thereby producing a synthetic quartz powder. Silica is sequentially held for a predetermined time at each temperature range of 150 to 400&#xb0; C., 500 to 700&#xb0; C., and 1,100 to 1,300&#xb0; C., thereby producing a quartz glass.

Method for producing silica particles

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Tokyo, Japan

Hirofumi Uehara