Multifunctional alumina composites with toughening and crack-healing features via incorporation of NiAl particles

In this research, NiAl particles modified Al₂O₃ composites with toughening and crack-healing performances were prepared by spark plasma sintering. The toughening effects as a function of the NiAl particle size and content were systematically investigated. The fracture toughness was increased by 80% compared with pure alumina after incorporation of 1 μm NiAl particles at 15 wt%. A self-healing process of damaged composites induced by indentation was found to occur, mediated by oxidation of NiAl at elevated temperatures with the size of the NiAl particles. Atomic force microscopy was adopted to characterize the crack-healing performance and to explore the healing mechanism under each healing condition. The best crack-healing efficiency of 99.2% was found in the composite containing 1 μm NiAl at 15 wt% that was annealed at 1300°C for 5 h. In addition, the fracture toughness of the composite was further enhanced by 40% after the crack-healing process. These multifunctional ceramic composites may have promising and broad application in areas such as thermal barrier coatings, fuel cell membranes, etc.