In-situ high temperature X-ray diffraction study of Ni/Al2O3 interface reactions

In-situ experiments on the Ni/Al2O3 interface reaction were carried out with a high temperature X-ray diffractometer capable of measuring the X-ray diffraction pattern in 1-2 s using an imaging plate. The kinetic formation processes of the interface reaction layer were measured by short-period exposure experiments with a high temperature X-ray diffractometer. NiAl2O4 was formed at the Ni/Al2O3 interface from 1468 K to 1673 K in air. The formation of NiAl2O4 obeyed the parabolic rate law. The value of the activation energy suggests that the diffusion of Al through NiAl2O4 controls the rate of formation. The results of thermal expansion coefficient measurements suggest that when a sample is cooled to room temperature, the magnitude of the stress on the Al2O3 owing to NiAl2O4 is smaller than that caused by NiO. (C) 1997 Acta Metallurgica Inc.