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Nonisothermal Diffusion Measurements on Granular Solids: Noble Gas Diffusion in Fused Silica

Abstract Samples of fused SiO2 and of a soda-lime glass were exposed to He, Ne, and Ar at temperatures between 523 and 763 °K, cooled to room temperature, transferred to a desorption cell, and then heated slowly and uniformly. The cell was connected to a mass spectrometer and the desorption rates were measured as a function of time. From the data, the parameters E and Do of the Arrhenius equation for the diffusion coefficient [D = D0exp(-E/RT)] were calculated. The results were found to agree rather well with literature data obtained on similar glasses using isothermal methods. Since the nonisothermal technique may be very useful for the study of granular materials and powders, the problems related to the presence of a grain size distribution and to the irregularities of grain shapes are treated in this study in some detail.