Generalized Wagner’s diffusion model of surface modification of materials by plasma diffusion treatment

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f^-1(t/t₀), where g(t) is the sub-layer thickness at time t, g₀ and t₀ are parameters that depend on the treated material and plasma characteristics, and f^-1 is the inverse function of f(x)=-(ln(1-x)+x), where x=g(t)/g₀, 0≤x≤1. Under negligible erosion effects, the model becomes of Wagner’s diffusion model type and the expression for g(t) reduces to the parabolic law. The model can be simplified by considering the compound layer as a united one. The general and simplified models can be used as a method for the experimental determining of the effective diffusion coefficients and the erosion rate during plasma treatment of material surfaces.