Crack Healing of Nano-Ni/Al2O3 Hybrid Materials via High-Temperature Oxidation

Authors :: Maruoka, Daisuke
Nanko, Makoto
Source :: Materials Science Forum; September 2011, Vol. 696 Issue: 1 p378-383, 6p
Publication Year :: 2011
Abstract: Crack-healing effectiveness was investigated on 5 vol% nano-Ni dispersed Al<subscript>2</subscript>O<subscript>3</subscript> hybrid materials. Influence of the Y or Si doping or SiC co-dispersion was also studied on the crack healing behavior. Cracks were introduced by a Vickers indentation to be a crack length of approximately 60 μm. Cracks of nano-Ni/Al<subscript>2</subscript>O<subscript>3</subscript> were completely disappeared, for example, by oxidation at 1200°C for 6 h in air, Y/Si doped one and SiC co-dispersed one have similar performance of crack disappearance. Bending strength of crack-disappeared samples showed about 550 MPa and was comparable or improved with that of as-sintered one. Mechanism of crack healing was considered as filling up of cracks by NiAl<subscript>2</subscript>O<subscript>4</subscript> oxidation product which is developed by outward diffusion of cations at grain boundary of Al<subscript>2</subscript>O<subscript>3 </subscript>matrix. Nano-Ni/Al<subscript>2</subscript>O<subscript>3</subscript> with Y or Si doping or SiC co-dispersion are realized to have crack-healing effectiveness with improved high-temperature oxidation resistance.