Tosoh Corporation

Nippon Silica Glass Co., Ltd.

Other

Yoshikazu Kikuchi

Koji Tsukuma

Tomoyuki Akiyama

Hiroya Nagata

Masayuki Kudo

Nobusuke Yamada

Hideaki Segawa

Shinkichi Hashimoto

Yushiharu Funakoshi

Emiko Abe

Kouichi Ono

Kenji Kamo

Koichi Orii

Yukinobu Hara

An opaque silica glass article comprising a transparent portion and an opaque portion, wherein the opaque portion has an apparent density of 1.70-2.15 g/cm and contains 5&times;10 -5&times;10 bubbles per cm , said bubbles having an average diameter of 10-100 &mgr;m; and the transparent portion has an apparent density of 2.19-2.21 g/cm and the amount of bubbles having a diameter of at least 100 &mgr;m in the transparent portion is not more than 1&times;10 per cm. The opaque silica glass article is made by a process wherein a mold is charged with a raw material for forming the opaque portion, which is a mixture comprising a silica powder with a small amount of a silicon nitride powder, and a raw material for forming the transparent portion so that the two raw materials are located in the positions corresponding to the opaque and the transparent portions, respectively, of the silica glass article to be produced; and the raw materials are heated in vacuo to be thereby vitrified.

Opaque silica glass article having transparent portion and process for producing same

A high-purity transparent silica glass containing Fe, Na and K impurities each in an amount of 0.01-0.3 ppm, and an OH group in an amount of 0-3 ppm; among the Fe impurities, the content of metallic Fe having a valency of +0 being not larger than 0.1 ppm. This transparent silica glass exhibits, even when it is maintained at 900-1,400.degree. C. for at least 20 hours, an extinction coefficient of not larger than 0.009 at a wavelength of 400 nm, and does not become colored as visually examined. The silica glass is made by a process wherein powdery silica filled in a mold cavity is melted at 1,700.degree. C. or higher, characterized in that the melting is conducted in a graphite mold having a porous high-purity graphite layer provided on the mold inner surface so that the filled silica is not contacted with the mold; said porous layer having a bulk density of 0.1-1.5 g/cm.sup.3, and the content of each of Fe, Na and K impurities in the porous layer being not larger than 1 ppm.

High purity transparent silica glass

Pure transparent quartz glass is provided by molding powdery amorphous silica into an article, converting the molded powdery amorphous silica into crystalline silica of high-temperature type cristobalite structure, and then fusing the crystalline silica, the quartz glass containing impurities respectively at a content of not higher than 1 ppm, and an OH group at a content of not higher than 20 ppm, and having a viscosity of 10.sup.12.0 poise or more at 1200.degree. C. The quartz glass is transparent and has high purity, and is excellent in high temperature viscosity characteristics. The quartz glass can be produced at a low cost.

Process for production of pure transparent quartz

The high-purity, opaque quartz glass containing 3.times.10.sup.6 -9.times.10.sup.6 of closed cells having an average size of 20-40 .mu.m per 1 cm.sup.3, a ratio of closed cells having sizes of 100 .mu.m or more to the whole of cells being 1% or less, thereby showing 5% or less of linear transmittance for near infrared rays (.lambda.=900 nm) at a thickness of 1 mm is produced by compacting amorphous silica powder having an average particle size of 0.5-10 .mu.m, in which each of impurities selected from Li, Na, K, Fe, Ti and Al is 1 ppm or less, if any, and sintering the resultant green body at 1730.degree.-1850.degree. C.

High-purity, opaque quartz glass, method for producing same and use

Growing community of inventors

Sagae, Japan

Yoshikazu Kikuchi