High entropy oxide as interfacial material for toughened textured alumina

• Main Authors: Liu, Junbo, Ma, Zhuoran, Behera, Rohit Pratyush, He, Hongying, Xiong, Ji, Le Ferrand, Hortense
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2024
• Subjects: Engineering::Materials; High-Entropy Oxide; Magnetically Assisted Slip Casting
• Online Access: https://hdl.handle.net/10356/173030
• Institution: Nanyang Technological University

Textured alumina ceramics with brick-and-mortar microstructures exhibit surprisingly high values of strength and toughness as compared to traditional ceramics. However, in full ceramic systems, pressure-assisted sintering restricts their shaping potential and the study of interfacial materials is still insufficient. Here, we create a textured alumina with high indentation fracture toughness by using a high entropy oxide (HEO) as the mortar. Our HEO mortar is strong, tough, has a high wetting behavior to alumina platelets used in the green body, and promotes densification via liquid phase sintering. Textured aluminas with HEO mortar at concentrations varying from 0 to 90 wt% were fabricated using magnetically assisted slip casting (MASC) and pressureless sintering through the templated grain growth (TGG) process. Trade-off between density and grain anisotropy led to the highest mechanical properties. Textured alumina with 10 wt% HEO exhibited >95% relative density, an elastic modulus of ~240 GPa, a flexural strength of ~360 MPa, and an indentation fracture toughness of ~6.8 MPa∙m0.5, which is more than 1.9 times that of the usual polycrystalline alumina. Thanks to the mineral nature of HEO, the simplicity of the process and the mechanical properties, the textured alumina with HEO mortar can be produced in complex shapes and could find applications in stringent environments.