Manufacture of vitreous silica product via a sol-gel process using a polymer additive

Method for fabricating an article at least in part composed of high silica glass including

• fabricating a high-silica glass body by a method comprising gelling a sol, the sol comprising a suspension of colloidal silica particles in a suspension medium, so resulting in a gel,
• drying the gel so as to substantially remove the suspension medium, and
• firing such gel to produce a high-silica glass body, and carrying out any further processing necessary to yield the article
• characterized in that the said sol, during a substantial part of the gelling, contains additive including a first additive consisting essentially of at least one organic polymer, the polymer being characterized as:
• (1) of amount sufficient to monomolecularly coat from 5% to 50% of the total free surface of the colloidal silica particles,
• (2) of solubility as to result in substantially complete solution in the said sol prior to gelation,
• (3) of such nature as to wet the said silica particles,
• (4) of such composition as to thermally decompose primarily to gaseous decomposition product so that the high silica glass body is substantially free of the polymer as well as of decomposition product constituting a meaningful contaminant deleteriously affecting performance of the article.