Patent ID: 6860118
Filing Date: 2005-03-01
Classification: C03B

Abstract:
1. A method for fabricating silica glass having a decreased quantity and size of micro-bubbles using a sol-gel process, the method comprising the steps of: forming a sol by mixing a starting material, deionized water and an additive together; a gelation step for gelatinizing the sol after filling a circular mold with the gel produced; separating the gel from the circular mold and drying the gel; placing the gel inside of a heat chamber and injecting helium gas into the heat chamber; and a low heat treatment step for pressurizing and depressurizing an internal pressure of the heat chamber repeatedly for several times, said method further comprising the step of sintering the gel that has been through the low heat treatment by heating the gel at high temperature, wherein the low heat treatment step includes: (i) providing a primary heat treatment sub-step to heat the chamber to a first predetermined temperature; (ii) cooling to reduce the first predetermined temperature of the heat chamber to a second predetermined temperature that is lower than the first predetermined temperature; (iii) providing a secondary heat treatment sub-step by: (a) decreasing an internal pressure if the heat chamber to a predetermined value of depressurization; (b) increasing the internal pressure of the heat chamber to a subsequent predetermined value of pressurization; and (b) repeating sub steps (iii) a and (iii) (b) for a predetermined plurality of times.