Fabrication of fibrous Al₂O₃-(m-ZrO₂)/HAp-(t-ZrO₂) core/shell composites with elongated grain formation

Abstract

Fibrous Al₂O₃-(monoclinic-ZrO₂)/HAp-(tetragonal-ZrO₂) composites were fabricated with a core/shell microstructure by the multi-pass extrusion process depending on the volume fraction of Al₂O₃-(m-ZrO₂) core and HAp-(t-ZrO₂) shell. In the sample sintered at 1200°C, the Al₂O₃-(m-ZrO₂) core was composed of porous, equiaxed grains, independent of core/shell volume fraction. However, after sintering at 1500°C, the core phase was changed with elongated grains of a reaction phase CaAl₁₂O₁₉. Formation of elongated grain increased as the core diameter decreased. A significantly improved value of fracture toughness (4.3 MPa·m^1/2) was obtained in the Al₂O₃-(m-ZrO₂)/HAp-(t-ZrO₂) composites with 50_core/50_shell composition sintered at 1500°C.