Effect of Oxygen on the Surface Tension of Liquid Nickel and the Wettability of Alumina by Liquid Nickel

Abstract

The surface tension of liquid Ni-O alloys and the wettability of Al2O3 substrates by liquid Ni-O alloys were measured by a sessile drop method in an atmosphere of Ar+H2O+H2 gas mixtures at 1873 K. The adsorption of oxygen in a surface layer and the adhesion in the liquid Ni-O alloy/Al2O3 substrate interface were considered on the basis of experimental results. The following conclusions have been obtained.(1) The surface tension of liquid Ni was remarkably lowered with the addition of a very small amount of oxygen.(2) Excess surface concentration corresponding to monolayer coverage was 18×10−6 mol/m2, and this value agreed approximately with the reported values in the liquid Fe-O system.(3) The wettability of Al2O3 by liquid Ni was strongly affected by the dissociation of Al2O3 in the region of very small content of oxygen (<0.003 wt%O) and the formation of NiAl2O4 layer at the interface in the region of higher oxygen contents (>0.005 wt%O).