TABLE OF CONTENTS Most kinetic phenomena in solids involve diffusion, or a unit step very similar to that operating in diffusion. It is appropriate therefore to start our study of kinetic phenomena with a study of the fundamentals involved in diffusion in various materials. We cannot provide a complete description of diffusion because, as with nearly every other chapter in this book, such a complete description requires a book in itself. This chapter begins with a phenomenological treatment of linear processes that is based on the thermodynamic theory of irreversible processes. This very general approach is made specific by application to diffusion in a binary alloy. Diffusion in ionic crystals and semiconductors follows on the basis of the relations developed for metals and the thermodynamics of defects in these materials. Then diffusion along high diffusivity regions, such as grain boundaries, is discussed. Finally, the current computer assisted strategies for extending the basic concepts described in this chapter to problems involving multicomponent diffusion in technological applications are discussed. Also, diffusion of polymer strands is treated briefly. Diffusion in liquids is not considered in this chapter.
It is often possible to relate fluxes of matter, heat and charge to corresponding forces linearly, as shown in equation 8.1
where J i is the number or quantity of i passing unit area per unit time, L ik is a conductance relating the kth generalized force X k to the flux J i. In the case of...
