Calcium hexaluminate articles

Claim 1

THAT METHOD OF MAKING ARTICLES OF STABLE CALCIUM HEXALUMINATE MATERIAL COMPRISING FORMING A MIXTURE OF 100 PARTS, BY WEIGHT, OF DRY MATERIALS WHICH YIELD ALPHA ALUMINA AND CALCIA ON ABOUT A 6 TO 1 MOLAR OXIDE BASIS AT A TEMPERATURE BELOW 2000*F. AND IN THE FORM OF INTIMATELY ADMIXED PARTICLES SUBSTANTIALLY ALL OF WHICH ARE -150 MESH WITH THE MAJOR PORTION THEREOF BEING FINER THAN 325 MESH, SAID MATERIALS AT 2000*F. ANALYZING AT LEAST ABOUT 99% AL2O3+CAO, BY WEIGHT, ON AN OXIDE BASIS, AND UP TO 30 PARTS, BY WEIGHT, OF -28 MESH BURNOUT MATERIAL, MIXING SAID DRY INGREDIENTS WITH ABOUT 6 TO 50 PARTS, BY WEIGHT, OF WATER, FORMING THE RESULTING WET MIXTURE INTO SELF-SUSTAINING SHAPES, FIRING SAID SHAPES TO A TEMPERATURE IN THE RANGE 2100 TO NO MORE THAN 3300*F., MAINTAINING SAID TEMPERATURE UNTIL EQUILIBRIUM CONDITIONS EXIST SUCH THAT SAID CALCIUM HEXALUMINATE MAERIAL IS MICROSCOPICALLY CHARACTERIZED AS A MASS OF RANDOMLY ORIENTED HEXAGONAL PLATES SUBSTANTIALLY FREE OF VITRIFIED PHASES AND HAS A POROSITY BETWEEN ABOUT 15 AND 70% AND GOOD CAPILLARITY.