Claims
- 1. A method for making a porous glass article comprising the steps of:
- a. fusing a mixture containing 38 to 42 percent by weight SiO.sub.2, 49 to 52 percent B.sub.2 O.sub.3, 8 to 10 percent by weight R.sub.2 O, where R is sodium or potassium, and 0 to 4 percent by weight Al.sub.2 O.sub.3,
- b. phase separating such glass into two phases, one of which is a borate-rich phase and the other a silica-rich phase,
- c. leaching the phase-separated glass with either water or mineral acid for a time and at a temperature sufficient to remove a major portion of the borate-rich phase to form a porous glass high in silica, and
- d. rinsing the porous glass.
- 2. A method for making a low alkali-containing porous glass article comprising:
- a. melting a glass containing 38 to 42 percent by weight SiO.sub.2, 49 to 52 percent by weight B.sub.2 O.sub.3, and 8 to 10 percent by weight R.sub.2 O, where R is alkali metal,
- b. heating the phase-separable alkali-borate glass to a temperature of about 460.degree. to 500.degree.C. for about 2 to 6 hours, followed by cooling uniformly over a period of about 1 to 3 hours to a temperature of 400.degree. to 420.degree.C. and then slowly cooling to room temperature over a period of about 1 to 16 hours to thereby separate the glass into two phases, one of which is a borate-rich phase and is soluble in aqueous solution,
- c. leaching the phase-separated glass with the aqueous solution for a time and at a temperature sufficient to remove a major portion of the borate-rich phase to form a porous glass high in silica, and
- d. rinsing the porous glass; said porous glass articles having pore diameters within the range of 50 to 200 Angstrom units.
- 3. A method for making a low alkali-containing porous glass article comprising:
- a. melting the glass containing 38 to 42 percent by weight SiO.sub.2, 49 to 52 percent by weight B.sub.2 O.sub.3, and 8 to 9 percent by weight R.sub.2 O, where R is alkali metal, to produce a phase-separable alkali-borosilicate glass,
- b. heating the phase-separable alkali-borosilicate glass to a temperature of 560.degree. to 600.degree.C. for about 2 to 6 hours, followed by cooling uniformly said glass over a period of about 1 to 3 hours to a temperature of 400.degree. to 420.degree.C. and then cooling to room temperature over a period of 1 to 16 hours to separate the glass into two phases, one of which is a borate-rich phase and is soluble in an aqueous solution,
- c. leaching the phase-separated glass with the aqueous solution for a time and at a temperature sufficient to remove a major portion of the borate-rich phase to form a porous glass high in silica, and
- d. rinsing the porous glass;
- said porous glass article having pore sizes within the range of 600 to 1000 Angstrom units.
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a division of U.S. patent application Ser. No. 447,199. filed Mar. 1, 1974, now U.S. Pat. No. 3,923,533, which is a continuation-in-part of U.S. patent application Ser. No. 311,191, filed Dec. 1, 1972, now U.S. Pat. No. 3,843,341, which in turn is a continuation-in-part of the following U.S. applications: Ser. No. 231,346, filed Mar. 2, 1972, now abandoned, and Ser. No. 264,081, filed June 19, 1972, now abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
3843341 |
Hammel et al. |
Oct 1974 |
|
Divisions (1)
|
Number |
Date |
Country |
Parent |
447199 |
Mar 1974 |
|
Continuation in Parts (2)
|
Number |
Date |
Country |
Parent |
311191 |
Dec 1972 |
|
Parent |
231346 |
Mar 1972 |
|