| 摘要 |
A highly crystalline glass-ceramic which exhibits high toughness and a modulus of rupture in excess of 1406 Kg/sq.cm (20,000 psi), which has as the predominant crystal phase canasite and/or agrellite and/or fedorite and which comprises, in weight percent on the oxide basis, from 45 to 75% SiO2, from 8 to 30% CaO, from 3.5 to 12% F, from 3 to 15% Na2O, from 0 to 20% K2O, from 5 to 25% Na2O + K2O, from 0 to 6% B2O3, from 0 to 7% Al2O3 and from 0 to 12% ZrO2 is disclosed.
<??>A process for the production thereof which comprises:
(a) melting a batch for a glass;
(b) simultaneously cooling the melt to a temperature at least below the transformation range thereof and shaping a glass of a desired configuration therefrom; and
(c) exposing the glass to a temperature of from 500 to 1000 DEG C to cause the growth therein of the desired crystals is also disclosed.
<??>The present materials have a number of advantages over the prior art, particularly as regards the toughness, strength and breakage properties thereof. |
