Semicrystalline ceramic body and method of making it

• US 3,161,528 A
• Filed: 10/03/1962
• Issued: 12/15/1964
• Est. Priority Date: 10/03/1962
• Status: Expired due to Term

• Current Assignee: Richard A. Eppler
• Original Assignee: Richard A. Eppler
• Inventors: Eppler, Richard A.
• Application Number:
  US04/228,036
• Time in Patent Office: 804 Days
• US Class Current: 501/7
• CPC Class Codes: C03C 10/0027 containing SiO2, Al2O3, Li2O as main constituents
• CPC Class Codes: C03C 4/06 for phototropic or photochromic glass
• CPC Class Codes: C03C 4/065 for silver-halide free photochromic glass

Claims

1. A SEMICRYSTALLINE CERAMIC BODY HAVING A COEFFICIENT OF THERMAL EXPANSION AT 0-300*C. RANGING FROM ABOUT 19-80X10**7/*C. AND A SPECIFIC GRAVITY OF 99-101% OF THAT OF THE GLASS BODY OF IDENTICAL COMPOSITION CONSISTING ESSENTIALLY OF A MULTIPLICITY OF HETEROGENEOUSLY-NUCLEATED INORGANIC CRYSTALS RANDOMLY DISPERSED IN A GLASSY MATRIX, SAID CRYSTALS BEING PREDOMINANTLY LITHIUM METASILICATE, SILICA O, AND BETA-SPODUMENE SOLID SOLUTION AND BEING FORMED BY CRYSTALLIZATION IN SITU ABOUT SUBMICROSCOPIC NUCLEI OF A PHOTOSENSITIVE METAL FROM A GLASS BODY CONSISTING ESSENTIALLY, BY WEIGHT, OF 7-11% LI2O, 1-2% NA2O, 3-5% K2O, 3-4% ZNO, 12-16% AL2O3, 62-74% SIO2, AND THE INDICATED PROPORTION OF AT LEAST ONE PHOTOSENSITIVE METAL SELECTED FROM THE GROUP CONSISTING OF 0.001-0.03% GOLD COMPUTED AS AU, 0.001-0.3% SILVER COMPUTED AS AGCL, AND 0.0001-1% COPPER COMPUTED AS CU2O, SUBSTANTIALLY ALL OF SAID CRYSTALS BEING SMALER THAN 30 MICRONS IN DIAMETER AND COMPRISING AT LEAST 30% BY WEIGHT OF SAID SEMI-CRYSTALLINE CERAMIC BODY, SAID GLASSY MATRIX CONSISTING ESSENTIALLY OF THE UNCRYSTALLIZED PORTION OF THE GLASS REMAINING AFTER THE DEVELOPMENT OF THE CRYSTALS.

2. A METHOD OF MANUFACTURING A SEMICRYSTALLINE CERAMIC BODY HAVING A COEFFICIENT OF THERMAL EXPANSION AT 0-300*C. RANGING FROM ABOUT 19-80X10**7/*C.. AND A SPECIFIC GRAVITY OF 99-101% OF THAT OF THE GLASS BODY OF IDENTICAL COMPOSITION WHICH COMPRISES PROVIDING AN ARTICLE OF PHOTOTHERMALLY OPACIFIABLE GLASS CONSISTING ESSENTIALLY, BY WEIGHT, OF 7-11% LI2O, 1-2% NA2O, 3-5% K2O, 3-4% ZNO, 12-16% AL2O3, 62-74% SIO2, AND THE INDICATED PROPORTION OF AT LEAST ONE PHOTOSENSITIVE METAL SELECTED FROM THE GROUP CONSISTING OF 0.0001-0.03% GOLD COMPUTED AS AU, 0.001-0.3% SILVER COMPOUND AS AGCL, AND 0.001-1% COPPER COMPUTED AS CU2O, EXPOSING THE ARTICLE TO SHORT-WAVE RADIATIONS, HEATING THE EXPOSED ARTICLE TO A TEMPERATURE OF AT LEAST ABOUT 560*C., BUT NOT MORE THAN ABOUT 620*C., FOR AT LEAST 2 MINUTES TO INITIATE THE NUCLEATION OF SUBMICROSCOPIC NUCLEI OF PHOTOSENSITIVE METAL, RAISING THE TEMPERATURE OF SAID ARTICLE TO AT LEAST ABOUT 625*C., BUT NOT MORE THAN ABOUT 670*C., FOR AT LEAST 5 MINUTES TO OPACIFY THE GLASS FOR FORMING THEREIN SILICEOUS CRYSTALLITES WHICH ARE PREDOMINANTLY LITHIUM METASILICATE IN AN AMOUNT ADEQUATE TO SUPPORT THE ARTICLE AGAINST DEFORMATION UPON HEATING TO A TEMPERATURE ABOVE THE SOFTENING POINT OF THE ORIGINAL GLASS, RAISING THE TEMPERATURE OF SAID ARTICLE TO AT LEAST ABOUT 750*C., BUT NOT MORE THAN ABOUT 850*C., FOR A TIME SUFFICIENT TO ATTAIN THE DESIRED CRYSTALLIZATION CONSISSTING PREDOMINANTLY OF LITHIUM METASILICATE, SILICA O, AND BETA-SPODUMENE SOLID SOLUTION, AND THEREAFTER COOLING SAID ARTICLE TO ROOM TEMPERATURE.