Calculation of sublimation with allowance for impurity diffusion

Abstract

We have calculated the impurity distribution in a spherical material during sublimation. The solutions found depend on two dimensionless parameters: separation factor β and diffusional Peclet number Pe = wR₀/(ρ₁D), where w is the mass vaporization rate, R₀ is the initial sphere radius, ρ₁ is the density of the material, and D is the impurity diffusion coefficient. For the limiting cases Pe ≫ 1 and Pe < 1, we derived analytical expressions for the impurity distribution in the subliming material and for the average impurity concentrations in the residue and condensate as functions of time t or the degree of sublimation g(t). The present results can be used to optimize the dimensions of subliming materials and sublimation conditions.