YAlO3 Reinforced AlN Composite Ceramics with Significantly Improved Mechanical Properties and Thermal Shock Resistance

AlN is regarded as a promising ceramic material for high performance structural and high temperature applications due to its superior properties such as high thermal conductivity, excellent stability and wear resistance. However, challenges remain in fabricating AlN ceramics with high strength and high thermal shock resistance. In this work, AlN/YAlO3 composites with different YAlO3 contents (3-10 wt%) were prepared by a simple pressureless sintering method, and the impact of YAlO3 content on mechanical properties and thermal shock resistance of AlN/YAlO3 composites was investigated. Results show that the grain growth of AlN is inhibited and the densification is improved with the addition of 3 wt% and 5 wt% YAlO3. Hence, the flexural strength and fracture toughness of AlN/YAlO3 composites are improved due to the grain refinement and compactness enhancement, and the highest value, 369 MPa and 3.84 MPa m1/2, are reached by the AlN-5 wt% YAlO3 composite. Moreover, the thermal shock resistance was assessed through theoretical forecast and cyclic thermal shock tests over a temperature range between 1000 degrees C and 1600 degrees C. Comparing with pure AlN, the thermal stress damage resistance parameters (RIV) of AlN/YAlO3 composites were increased, while their residual strengths and retention ratios after 10-50 cycles of thermal shock tests maintained a higher level as well. Microstructure analysis revealed that the thermal shock resistance of AlN/YAlO3 composites was evidently improved attributing to various strengthening mechanisms such as crack deflection, crack branching and microcrack toughening.