DIFFUSION IN MATERIALS WITH VARIABLE-TEMPERATURE .1. ONE-DIMENSIONAL PROBLEMS

Solutions for diffusion in non-isothermal conditions are derived by an alogy with diffusion in isothermal conditions when diffusivity is cons tant or time dependent. The effects of heating or cooling rates on the concentration profiles, boundary-layer thickness, and amount of mater ial transferred, are described and can be assessed even when the tempe rature dependence of diffusivity and/or interfacial concentration is u nknown. The effects of the rate of change in temperature on the amount of material transferred can be used also to assess whether this is co ntrolled by diffusion or reaction.