Method of making alkali metal, calcium fluorosilicate glass-ceramic articles
AssigneeCorning Glass Works
InventorGeorge H. Beall
Life of this patent
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Abstract
The instant invention is directed to the production of highly crystalline glass-ceramic articles demonstrating high intrinsic mechanical strength and toughness containing crystals of canasite and/or agrellite and/or fedorite as the predominant crystal phase. The articles have overall compositions consisting essentially, expressed in terms of weight percent on the oxide basis, of about ______________________________________ SiO.sub.2 45-75 CaO 8-30 F 3.5-12 Na.sub.2 O 3-15 K.sub.2 O 0-20 Na.sub.2 O + K.sub.2 O 5-25 B.sub.2 O.sub.3 0-6 Al.sub.2 O.sub.3 0-7 ZrO.sub.2 0-12. ______________________________________
Claims3
A method for preparing a highly crystalline glass-ceramic article exhibiting high toughness and a modulus of rupture in excess of 20,000 psi, wherein the predominant crystal phase is canasite and/or agrellite and/or fedorite, which comprises the following steps:
- (a) melting a batch for a glass consisting essentially, expressed in terms of weight percent on the oxide basis, of about
- ______________________________________ SiO.sub.2 45-75 CaO 8-30 F 3.5-12 Na.sub.2 O 3-15 K.sub.2 O 0-20 Na.sub.2 O + K.sub.2 O 5-25 B.sub.2 O.sub.3 0-6 Al.sub.2 O.sub.3 0-7 ZrO.sub.2 0-12 ______________________________________
- (b) simultaneously cooling the melt to a temperature at least below the transformation range thereof and shaping a glass article of a desired configuration therefrom;
- and
- (c) exposing said glass article to a temperature between about 500.degree.-1000.degree. C. for a time sufficient to cause the growth therein of the desired crystals.
Dependencies are inferred from the claim text.