Molded amorphous silica bodies and molding powders for manufacture of same

Claim 1

A PROCESS FOR MAKING AMORPHOUS SILICA BODIES HAVING A DENSITY OF FROM 91 TO 100% OF THE THEORETICAL DENSITY OF AMORPHOUS SILICA WHICH COMPRISES THE STEPS (1) COMPACTING UNDER PRESSURE TO A UNIFORM DENSITY OF AT LEAST ABOUT 1 GRAM PER CUBIC CENTIMETER A POWDER CONSISTING ESSENTIALLY OF AGGREGATES OF AMORPHOUS SILICA ULTIMATE PARTICLES SUBSTANTIALLY FREE OF NON-VOLATILE CONSTITUENTS OTHER THAN SILICA, SAID AGGREGATES HAVING A PARTICLE SIZE IN THE RANGE FROM 0.1 TO 50 MICRONS, SAID POWDER HAVING A TAPPED BULK DENSITY OF AT LEAST 0.2 GRAM PER CUBIC CENTIMETER, THE ULTIMATE AMORPHOUS SILICA PARTICLES BEING SPHEROIDAL AND SUBSTANTIALLY UNIFORM IN SIZE AS OBSERVED BY ELECTRON MICROSCOPY, BEING DENSE, HAVING A COALESENCE FACTOR OF LESS THAN ABOUT 30% AND HAVING AN AVERAGE DIAMETER OF FROM 5 TO 300 MILLIMICRONS; (2) RELEASING THE PRESSURE AND THEN HEATING THE COMPACTED MATERIAL AT A TEMPERATURE ABOVE 1000*C. BUT BELOW THE DEVITRIFICATION TEMPERATURE OF THE MATERIAL UNTIL THE DENSITY OF THE RESULTING BODY IS INCREASED TO AT LEAST 2.0 GRAMS PER CUBIC CENTIMETER; (3) COOLING THE BODY BEFORE ANY CRISTOBALITE IS FORMED BY DEVITRIFICATION OF THE AMORPHOUS SILICA.