Surface Tension and Contact Angle

Surface tension is defined as the work for isothermal reversible creation of a new surface of a condensed phase. The temperature dependence of surface tension of a pure metal is negative, while that of an alloy can be both positive and negative. Once a nonreactive liquid is in contact with a flat solid surface, the liquid surface will intersect the solid surface at a contact angle θ. This process is called wetting. The equilibrium value of θe is determined by Young’s equation. In this chapter, three types of wetting are introduced: spreading wetting, immersion wetting, and adhesion wetting.