Abstract

The adhesive energies of nickel on thorium dioxide (ThO2), nickel/chromium (80/20) on ThO2, and iron/nickel/chromium (304 stainless steel) on aluminum oxide (Al2O3) were determined at temperatures ranging from roughly 200°C (360°F) below the melting point of the metallic component to approximately 50°C (90°F) above. The technique involves the measurement of the average surface free energy for the solid metals and liquid metal drops utilizing the zero-creep and sessiledrop shape concepts, respectively. Measurements of equilibrium energetics and associated geometries as well as the contact angles at metallic particles in contact with the ceramic substrates are described using the techniques of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Measurements of surface free energy of nickel/chromium and stainless steel drops equilibrated at temperatures below the melting point and utilizing the sessile-drop method are compared with those determined by the zero-creep method. The results of this investigation represent the first systematic study of the variation of adhesive energy of a metal/ceramic system with temperature, and the comparison of surface free energies determined from equilibrium particle shapes with zero-creep measurements of wires of the same material in the solid state.

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