Fabrication of large size near net shape components of silica glass

Large size silica articles, in particular optical glass components, are made by forming a silica colloidal solution; after gelation, the gel is cured, dried and sintered to form a dense glass having near net shape dimensions thereby reducing expensive polishing steps needed to obtain the desired final dimensions and surface quality. The process is characterized by the use of a two step acid-base procedure for the hydrolysis and condensation of tetralkoxides, addition to the sol of fumed silica in order to increase its concentration, hypercritical drying of the alcogel and sintering of the aerogel so obtained. Densification is uniform with three-dimensional shrinkage of the aerogel to a final shaped component of clear silica of the same properties as silica glass on the market, such as bulk density, Vickers hardness and thermal expansion coefficient.