Process for molding optical components of silicate glass to a near net shape optical precision

Claim 1

A method for making a near net shape silicate optical glass article comprising the following steps: Step 1--completely hydrolyzing silicon alkoxide in a solvent at a pH from about 2 to about 4 to form a solution having a molar ratio of silicon alkoxide to water in the range of about 1 to about 10; Step 2--partially removing from about 20 to about 60 volume percent of the solvent from the resulting solution of step 1 by vacuum distillation to form a concentrate having a pH of 6.8; Step 3--adding sufficient ammonium hydroxide to the concentrate of step 2 to raise the pH of the concentrate from about 6.8 to about 8.0 to accelerate gelation; Step 4--transferring the product formed in step 3 into a mold before complete gelation occurs and completing gelation to provide a gel in the mold; Step 5--curing the gel formed in the mold from step 4 for a period of about 16 to about 48 hours and at a temperature from about 20° C. to about 60° C., without drying, to form a cured molded article having a solvent remaining therein; Step 6--removing the cured molded article having a solvent remaining therein from the mold; Step 7--adding a displacing solvent to the product of step 6 to displace the remaining solvent to form a molded article having the remaining solvent displaced; Step 8--supercritically drying the molded article having the remaining solvent displaced from step 7 to form a dried molded article; Step 9--flushing the product from step 8 with an inert gas sufficient to remove any trace of the displacing solvent; Step 10--heating the product from step 9 in a dry oxidizing atmosphere to about 500° C.; Step 11--sintering the product of step 10 to 1150° C. in oxygen for a period sufficient to form a dense glass article having a dimensional deviation equal to or less than about a 12 microns deviation over a 3 mm center distance on the surface of the dense glass article.

Claim 2

A method for making a near net shape silicate optical glass article comprising the following steps: Step 1--completely hydrolyzing silicon alkoxide in a solvent at a pH from about 2 to about 4 to form a solution having a molar ratio of silicon alkoxide to water in the range of about 1 to about 10; Step 2--partially removing from about 20 to about 60 volume percent of the solvent from the resulting solution of step 1 by vacuum distillation to form a concentrate having a pH of 6.8; Step 3--adding sufficient ammonium hydroxide to the concentrate of step 2 to raise the pH of the concentrate from about 6.8 to about 8.0 to accelerate gelation; Step 4--transferring the product formed in step 3 into a mold before complete gelation occurs and completing gelation to provide a gel in the mold; Step 5--curing the gel formed in the mold from step 4 for a period of about 16 to about 48 hours and at a temperature from about 20° C. to about 60° C., without drying, to form a cured molded article having a solvent remaining therein; Step 6--removing the cured molded article having a solvent remaining therein from the mold; Step 7--adding a displacing solvent to the product of step 6 to displace the remaining solvent to form a molded article having the remaining solvent displaced; Step 8--supercritically drying the molded article having the remaining solvent displaced from step 7 to form a dried molded article; Step 9--flushing the product from step 8 with an inert gas sufficient to remove any trace of the displacing solvent; Step 10--heating the product from step 9 in a dry oxidizing atmosphere to about 500° C.; Step 11--sintering the product of step 10 to 1150° C. in oxygen for a period sufficient to form a dense glass article having a dimensional deviation equal to or less than about a 12 microns deviation over a 3 mm center distance on the surface of the dense glass article.