MEASUREMENT OF CONTACT-ANGLE IN SYSTEMS INVOLVING LIQUID-METALS

A technique has been developed for measurement of the contact angle of liquid metals with solid materials. The liquid metal, when contained in a small cup (inner diameter < 4 mm) forms a concave or convex mirro r surface. For the present technique, an optical method was devised to measure the radius of curvature of this mirror surface, from which th e contact angle can be determined. The surface of the liquid metal app roaches sphericity as the diameter of its container is decreased. The optical system formed in this method is non-paraxial. An analytical fo rmula, Valid for a spherical non-paraxial mirror, for calculation of i mage size was deduced. The technique has been demonstrated using the m ercury-graphite (15.9% total porosity) system at room temperature and the contact angle was determined to be 152.5 +/- 2 degrees.