A THERMAL-ETCHING STUDY OF THE NICKEL/ALUMINA INTERFACE

Nickel-alumina compacts have been thermally etched. Sections taken through the surface revealed that characteristic dihedral angles tended to develop at the lines of intersection between the alumina particles and the nickel surface. The angles seen in the section were measured and from these the dihedral angles and hence the surface and interfacial energies in the system were estimated. It is suggested that the results of Humenik and Kingery (J. Amer. Ceram. Soc., 1954, 37, 18) on the equilibrium of a liquid-nickel drop on alumina are probably not accurate, and in view of this the agreement between the two sets of results is satisfactory. It is concluded that solid nickel does not “wet” alumina, and that this is why it is difficult to sinter nickel-alumina composites to theoretical density. The addition of 5% aluminium to the nickel results in no significant improvement.