Functionally graded Al2O3-based ceramic systems by gel casting method

Functionally graded ceramic systems consisted of Al2O3/(Al2O3-ZrO2) and Al2O3/(Al2O3-Nd2Ti2O7) have been produced by gel casting. In Al2O3/ZrO2 systems, Al2O3 was gathered with three different Al2O3/ZrO2 mixtures with varying ZrO2 contents. For Al2O3/Nd2Ti2O7 system, Al2O3 layer was combined with 3 mol% Nd2Ti2O7-doped Al2O3. All samples sintered at 1480 and 1540 degrees C showed strong adhesion between layers without any crack formation. In the Al2O3/ZrO2 systems, both layers were intact; a distinct separation was observed, whereas a large reaction zone was observed for the Al2O3/Nd2Ti2O7 system as a consequence of reaction between both phases. The separation between layers for both systems was identified by SEM-EDX analyses. The hardness and wear tests of the samples showed that functional grading approach ensures combining various physical properties in a monolithic body.