US 4,317,668 A · Method for producing silica glass

Abstract

A method for producing silica glass wherein a dry silica gel subjected to a water desorption treatment and a carbon removal treatment is heated and has its temperature raised in an atmosphere containing chlorine, to perform a hydroxyl group removal treatment, the resultant silica gel is thereafter heated to a temperature of approximately 1,000.degree. C.-1,100.degree. C. in an atmosphere containing at least 1% of oxygen, to perform a chlorine removal treatment, and the resultant silica gel is further heated to a temperature of 1,050.degree. C.-1,300.degree. C. in He or in vacuum, to perform a sintering treatment. The silica glass thus produced does not form bubbles even when heated to high temperatures of or above 1,300.degree. C. Therefore, it is easily worked and it is free from the lowering of transparency attributed to the bubble formation.

Claims16

Dependent claims

A method for producing silica glass which comprises

(i) subjecting a dry silica gel to a water desorption treatment,
(ii) heating the resultant silica gel to effect a carbon removal treatment,
(iii) increasing the temperature in a chlorine-containing atmosphere to effect a hydroxyl group removal treatment,
(iv) further heating the resultant silica gel to a temperature of about 1,000.degree. to 1,100.degree. C. in an atmosphere other than air, containing at least 1% by volume of oxygen and the substantial remainder being a high purity inert or neutral gas that is moisture free to effect a chlorine removal treatment, and
(v) further heating the resultant silica gel to a temperature of about 1,050.degree. to 1,300.degree. C. in a helium atmosphere or in a vacuum to effect a sintering treatment.

2 more elements

Dependencies are inferred from the claim text.

Method for producing silica glass

Life of this patent

Method for producing silica glass

Life of this patent

Abstract

Claims16