Chapter IV - Thermodynamics of Interfaces

Abstract

For materials, one of the important set of properties is associated with surfaces and interfaces. This chapter illustrates thermodynamic aspects of these interfaces. The excess free energy associated with interfaces provides a driving force for a variety of kinetic processes. It is observed that these relations are developed quantitatively. The chapter describes two contrasting approaches to the concept of the surface or interface, those of Gibb's and Guggenheim. Various types of interfaces are also explored briefly and expressions governing their local equilibria are developed. The specific surface energy is calculated using a nearest-neighbor bond approximation for the cohesive energy. Values of specific surface energy so obtained deduced are compared to measured values of the average specific surface free energy. In addition, the bond model yields a good approximation for the value of the specific surface energy and thus the concept that the excess energy associated with the surface is related to the defect of bonds across the surface exhibits rough predictive value, at least for metals and covalently bonded materials.