Shin-Etsu Quartz Products Co., Ltd.

Tohru Yokota

Akira Fujinoki

Tatsuhiro Sato

Kyoichi Inaki

Nobumasa Yoshida

Akihiko Sugama

An efficient method is proposed for the utilization of heretofore useless extremely fine fluffy silica particles obtained as a flue dust in the flame-hydrolysis of vaporizable silicon compound in an oxyhydrogen flame in the manufacturing process of fused silica glass. The method comprises the steps of (a) uniformly mixing the silica particles with water, (b) drying the wet mixture under specified conditions to give dried cakes of the silica particles, (c) disintegrating the dried cakes into porous silica beads having an appropriate particle diameter, (d) semi-sintering the porous silica beads at 800 to 1300&deg; C. and (e) vitrifying the semi-sintered silica beads at 1350 to 1550&deg; C. into vitrified poreless silica glass particles which can be used as a base material for the production of fused silica glass articles.

Method for the preparation of vitrified silica particles

Opaque silica glass having a density of 2.0 to 2.18 g/cm.sup.3, sodium and potassium elements concentrations in the silica glass of each 0.5 ppm or less and an OH group concentration of 30 ppm or less, and containing bubbles which are independent bubbles having the following physical values: a bubble diameter of 300 .mu.m or less, and a bubble density of 100,000 to 1,000,000 bubbles/cm.sup.3, and a production process for opaque silica glass, including: filling quartz raw material grain having a particle size of 10 to 350 .mu.m in a heat resistant mold, heating it in a non-oxidizing atmosphere from a room temperature up to a temperature lower by 50 to 150.degree. C. than a temperature at which the above raw material grain is melted at a temperature-raising speed not exceeding 50.degree. C./minute, then, slowly heating it up to a temperature higher by 10 to 80.degree. C. than the temperature at which the quartz raw material grain is melted at the speed of 10.degree. C./minute or less, and cooling after maintaining at the above temperature.

High purity opaque silica glass

A process for producing opaque silica glass in which a quartz raw material grain having a particle size of 10 to 350 .mu.m is filled into a heat resistant mold, the quartz raw material grain is heated in a non-oxidizing atmosphere from a room temperature up to a temperature lower by 50.degree. to 150.degree. C. than a temperature at which the above raw material grain is melted at a temperature-increase speed not exceeding 50.degree. C./minute, then, slowly heated up to a temperature higher by 10.degree. to 80.degree. C. than the temperature at which the quartz raw material grain is melted at the speed of 10.degree. C./minute or less, and the heated quartz raw material grain is further maintained at the temperature higher by 10.degree. to 80.degree. C. than the temperature at which the quartz raw material grain is melted, followed by cooling down to the room temperature. Especially, in the case of producing a large scale opaque silica glass block, a quartz raw material grain filled into a heat-resistant mold is heated by a belt-like heating source located perpendicularly to a trunk of a filling layer of the quartz raw material grain so as to form a moving heating zone in the filling layer and the heating zone is successively moved either upwardly starting at the lower end portion of the filling layer or downwardly starting at the upper end portion thereof in a non-oxidizing atomosphere.

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Koriyama, Japan

Tohru Yokota