Diffusion with the moving interface boundary - Analytical solving of the Stefan problem by means of the thermal potential of a double layer

摘要

The solution of the diffusion equation on the non-stationary boundary represents so called Stefan problem, which was solved by means of the thermal potential of a double layer with the accuracy sufficient for the description of diffusion phenomena. The results were new methods of calculation for determination of the mean value of the interdiffusion coefficient. The interface boundary shift and diffusivity in the binary systems Ni-Al and Ni-Si can be determined very precisely from the areas below and above the concentration curve. Further auxiliary four methods utilize, besides the areas, the concentration gradients at the interface boundary determined experimentally which are usually determined with lower accuracy. The diffusivities in the systems Ni-Al and Ni-Si were calculated from the balance equations that express the law of conservation of the diffusing material in the specimens and on the interface boundary.