Abstract
Dense nanocrystalline yttria ceramics without grain growth were obtained within a short densification period by a method combining SHS reaction and quick pressing (SHS-QP). The reactive mixtures consisting of Ni and Al with TiC as a diluent were used as a heat source. An yttria compact was inserted inside the reactants and warmed up by reaction heat at a heating rate of above 1300°C/min. When the temperature reached its maximum, high mechanical pressure was applied to the sample for densification. Dense nanocrystalline yttria was produced when temperature T was 1350°C and pressure P, 120 MPa. The rapid densification process was accomplished in 1 min. Microstructural analysis showed almost no grain growth compared to initial powder. For comparison, the hot pressing (HP) process was also used to densify the same yttria powders. The results prove that the HP process causes grains coarsening even when the sintering temperature is 1250°C.
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