Surface Tension and Supercooling Phenomenon of Liquid Ga

Surface tensions (γL) and contact angles (θ) of liquid gallium on Teflon and other substrates (Al2O3, SiO2, glass, graphite, BN, Al, Ni, As etc.) were investigated. The values on Teflon were 0.700 N/m and 156°, respectively, in pure argon atmosphere. we were especially interested in the relative values, γL′s, on the substrates as compared with γL on the Teflon substrate. Liquid Ga showed spreading wetting on pure Ni metal and adhesional wetting on Al (supposed to be corvered by Al2O3), semimetal As and nonmetal substrates. Surface tension of Ga was remarkably decreased by surface oxidation due to oxygen in air. The surface layer of liquid Ga caused by the contamination was in the pasty state where the structure was nearly the same as liquid Ga. The contamination caused liquid Ga a rather high supercooling of ΔT∼35 K. It seems that the origin of this high supercooling was due to the removal of nucleation sites of crystal Ga by the surface oxidation of liquid Ga.