STUDIES OF CERAMIC PROCESSING

The object of this program is to improve the structure of ceramics by processing. The overall temperature range of interest is 1800 F to above 3000 F. In the high portion of the range, 3000 F and above, spinel MgO-Al2O3 is presently under study. The parameters have been established for preparing suitable starting materials. Pure alums which by proper heat treatment result in the formation of ultra fine, pure magnesia and alumina, have been studied along with the formation of spinel. DTA, TGA, X-ray, electron microscopy, etc., have been utilized. Three compositions are of particular interest namely, 0.9Mg0.1. OAl2O3, 1.OMg0.1.OAl2O3 and 1.OMgO.0.9Al2O3. They have been studied as starting materials prereacted over the temperature range 950-1200 C and as bodies made of these prereacted materials and fired over the range 1370-1650 C. The intermediate temperature range 2600-3000 F, was studied utilizing the presintering approach to the prereacted raw materials technique and the results were reported in earlier reports. The low range, 1800-2600 F, was studied using the devitrification approach of the prereacted raw material technique. Cordierite is the crystalline phase of particular interest because of its low thermal expansion. The one-glass and the two-glass approaches have been studied.