Alumina-based ceramics reinforced with calcium hexaaluminate

Abstract

In this study, alumina ceramics containing calcium hexaaluminate are investigated. The specimens are obtained by axial pressing of granulated powders and pressureless sintering. Fracture toughness is tested using the indentation method. Microhardness is determined by the Vickers method. XRD and microstructural studies using a scanning electron microscope are carried out. It was found that the use of Ca(OH)2 leads to the formation of CaAl12O19 in sintered alumina ceramics. As the platelet content increases, the average length of the platelets increases from 2 to 3 µm. The width of the platelets is about 0.4 µm. Increasing the CaAl12O19 content decreases the size of Al2O3 grains. The average grain size of the alumina ceramics is 1.65 ± 0.02 µm. For the material containing 6 wt.% CaAl12O19 the average grain size is 0.95 ± 0.05 μm. An increase in the critical stress intensity factor for the formation of 6 wt.% CaAl12O19 in a material compared to alumina ceramics without additives has been established. The relative density of such a material is 95.3 ± 0.5 %, microhardness is 1800 ± 50 HV, fracture toughness is 5.2 ± 0.4 MPa ∙ m1 / 2. The increase in fracture toughness of composites containing CaAl12O19 platelets is due to the fracture of platelets, crack bridging and crack deflection.