Experimental determination of surface energy for high-energy surface: A review

The experimental determination of surface free energy is of great importance for engineering applications. However, there is no universal, reliable, and convenient measurement means to achieve experimental determination of solid surface energy for high-energy surface. In this work, the existing techniques for experimental determination of surface energy of solids, including indirect (4 kinds) and direct methods (3 kinds), were critically reviewed. In the indirect methods: the explicit interfacial bonding characteristics are required for the multiphase equilibrium technique and for the determination method from crystal equilibrium shape; the critical surface energy technique does not satisfy Zisman's hypothesis that the solid-liquid interface tension is zero (or close to zero), and the parameters fitted by empirical equations cannot have definite physical meaning; the derivation based on the surface tension in the liquid state can only obtain the surface energy of the solid phase near the melting point, and is limited to the prediction of the surface energy of elemental metal. Among the direct determination methods, except for the zero-creep method, are based on generalized determination technologies. All determined results are strongly influenced by the accuracy of the particle (grain) size, scale effect, the atmosphere, etc. This leads to the fact that the errors are still huge regardless of the determination method used, and it is difficult to achieve uniformity of the data. All methods rely to some extent on specific assumptions or theoretical models.