Effects of Preparation Methods on the Structure and Mechanical Properties of Kyanite-Reinforced Alumina Ceramics

In this work, kyanite-reinforced alumina ceramics were prepared using the prestress reinforcement method and the particle enhancement method. The effects of different preparation methods on the mechanical properties and microstructures of kyanite-reinforced alumina ceramics were investigated. The results showed that, compared to the pure alumina ceramic, the prestressed alumina ceramic (labeled as P-Al₂O₃) prepared by the prestress reinforcement method exhibited a significant improvement (31% higher than that of pure alumina) in flexural strength. This is mainly attributed to the fact that the compressive stress existing on the surface of P-Al₂O₃ inhibited crack propagation; therefore, the fracture energy and strength were increased. However, due to the numerous pores and cracks in the fracture surface caused by the decomposition reaction of kyanite, the alumina composites fabricated through the particle enhancement method (labeled C-Al₂O₃) displayed lower flexural strength and hardness than those with P-Al₂O₃. Additionally, an increase in kyanite content led to a decrease in properties such as flexural strength, Vickers hardness, density, the elastic modulus, and the thermal expansion coefficient, while resulting in an increase in porosity. This work demonstrates the importance of using a suitable preparation method aligned with the specific composite.