An investigation of the contact angles between low melting metals and substrates of niobium and zirconium

Abstract

Contact angles between droplets of tin, indium and gallium and substrates of niobium and zirconium were measured for various substrate surface roughnesses over the temperature range 303 −- 923 K. Three characteristic regions of the temperature dependence of contact angles were observed. A steady-state region in which the contact angle θ is relatively independent of temperature was preceded and followed by regions in which θ decreased rapidly with increasing temperature. For the steady-state or second region, contact angles were found to be independent of time, whereas in the third region the contact angles showed a decreasing trend with increasing time at constant temperature. In accordance with theoretical predictions, when θ is greater than 90°, an increase in roughness of the substrate causes a corresponding increase in θ. Electron microprobe analyses showed that only the system Ga-Zr exhibited evidence of interdiffusion at the interface.