Ni粒子分散Al₂O₃複合材料のNiAl₂O₄自己治癒層成長に対するNiイオン拡散の影響

抄録

It is known as Al₂O₃ dispersed with Ni particles composite (Ni/Al₂O₃) has self-healing function which recovers mechanical properties by the high-temperature oxidation of dispersoids. Ni/Al₂O₃ appear self-healing function not only by the contribution of high-temperature oxidation of Ni particles exposed on sample surface, but also contribution of grain boundary diffusion of Ni ions through Al₂O₃ matrix. The objective of this study is to investigate the influence of Ni ion diffusion on the growth of NiAl₂O₄ self-healing layers with different Ni volume fractions. Dence Ni/Al₂O₃ were prepared and etched nitric acid to remove surface Ni particles. Samples were heat treated at 1100–1355℃ for 6–48 h in air. NiAl₂O₄ self-healing layer is observed on the sample surfaces with and without etching. The NiAl₂O₄ self-healing layer grows with parabolic manner with respect to the heat treatment time, indicating that the diffusion of Ni ion through the Al₂O₃ grain boundary is the rate-controlling. The contribution of surface Ni to the growth of NiAl₂O₄ layers is independent of heat treatment conditions due to the surface Ni particles are defined by the Ni dispersion ratio. The contribution of Ni ion diffusion increases linearly with increasing Ni volume fraction. It indicates that the amount of Ni ions diffused through the grain boundary is proportional to the Ni volume fraction.