PREPARATION OF Al₂O₃-CaAl₁₂O₁₉-ZrO₂ COMPOSITE CERAMIC MATERIAL BY THE HYDRATION AND SINTERING OF Ca₇ZrAl₆O₁₈-REACTIVE ALUMINA MIXTURE

Al 2 O 3 -CaAl 12 O 19 -ZrO 2 compatibility field was obtained as a result of hydration and sintering of the mixture of Al 2 O 3 and Ca 7 ZrAl 6 O 18 powders. The hydrated Al 2 O 3 -Ca 7 ZrAl 6 O 18 mixture products were studied by XRD, DTA-TG-EGA and FT-IR after 14 days of curing and hydration at 50C. C 3 AH 6 , Al(OH) 3 and CaZrO 3 compounds were formed upon hydration. CaZrO 3 and the lime-rich calcium aluminates formed as transient phases during hydration and dehydration processes were converted to CA 6 and ZrO 2 in the presence of an excess of Al 2 O 3 during sintering at 1500C. The Al 2 O 3 -based dense refractory composite material was investigated by XRD, FT-IR, SEM-EDS and mercury porosimetry. The sintered ceramic microstructure consists of a homogeneous distribution of zirconia grains in an alumina matrix reinforced with the calcium hexaaluminate phase. The presence of Al 2 O 3 , CaAl 12 O 19 and ZrO 2 in the synthesized material was confirmed by XRD and FT-IR techniques. By applying the mercury intrusion porosimetry technique, the heterogeneous pore size distribution of the refractory composite material was determined.