NMR Study of Adsorbate Self-Diffusion in Porous Glasses |
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Authors: | JÖ RG KÁ RGER,JÖ RG LENZNER,HARRY PFEIFER,HARTMUT SCHWABE,WOLFGANG HEYER,FRANK JANOWSKI,FRIEDRICH WOLF,SERGEJ PETROVI DANOV |
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Affiliation: | Sektion Physik der Karl-Max-Universität Leipzig, Wissenschaftsbereich Experimentalphysik, German Democratic Republic;Sektion Chemie der Martin-Luther-Universität Halle, Wissenschaftsbereich Technische Chemie, German Democratic Republic;GrebenŠČicov Institute, Academy of Sciences of the USSR, Leningrad, USSR |
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Abstract: | The NMR pulsed field gradient technique was used to study molecular transport in porous glasses. The adsorbent materials were produced by leaching phase-separated sodium-boron-silica glasses of different composition, then heat-treating. The pore diameters of the glass samples produced were within the interval 0.8 to 50 nm. Water, methanol, dodecane, and do-decene were used as adsorbates. The coefficients of adsorbate self-diffusion were found to decrease with decreasing pore diameter. In comparison with the neat liquids, a reduction in the adsorbate mobility (up to two orders of magnitude) was observed. For the larger pores, that decrease may be attributed to the tortuosity of the adsorbent, whereas the low diffusivities in the porous glasses with small pores are a consequence of the stabilizing effect of the rigid adsorbent framework. |
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