Experimental methods for studying the diffusion of radioactive gases in solids. VIII. Longitudinal-section method

The methodical details of the application of the longitudinal-section method in combination with autoradiography to the study of the diffusion of radioactive gases and vapors in solids have been considered. The diffusion parameters of cyclohexane, carbon tetrachloride, and benzene labeled with carbon-14 in low-density polyethylene have been determined. Various mathematical models of the diffusion of vapors in polymers, viz., classical diffusion in the presence of radioactive decay or a first-order chemical reaction, diffusion with trapping, dissociative diffusion, and diffusion with concentration and coordinate dependences of the diffusion coefficient, have been analyzed. A method for treating experimental data has been proposed. Concentration dependences of the diffusion coefficient have been calculated from the distribution curves of the concentration across the thickness of the sample. It has been shown that the plasticizing effect of the diffusates becomes stronger along the series: cyclohexane, carbon tetrachloride, benzene