FABRICATION OF CORDIERITE CERAMICS BY DEN SIFICATION CRYSTALLIZATION OF GLASS COMPACTS AND EVALUATION OF THEIR THERMAL-SHOCK FRACTURE-RESISTANCE/

Four kinds of cordierite ceramics were fabricated by firing the glass compacts having the composition of 2MgO.2Al(2)O(3) . 5SiO(2) and the s ame composition with small amount of ZrO2 at 1373 K for Ih at heating rate of 6 K/min and 20 K/min, Their thermal shock fracture resistance was investigated through a rapid change in bending strength of quenche d specimen. The critical quenching temperature difference (Delta T-c) of the sintered bodies with the chemical composition close to cordieri te bred at 6 K/min was about 650 K, while the Delta T-c=550 K for the sintered bodies fired at 20 K/min. On the other hand, the cordierite c eramics with small amount of ZrO2 revealed to have 500-550 K as their Delta T-c. Although an addition of ZrO2 to cordierite composition and high heating rate have given rise to higher strength of sintered bodie s, no effect on an increase in Delta T-c was recognized because Young' s modulus and the thermal expansion coefficient of sintered bodies inc reased simultaneously.