129Xe nuclear magnetic resonance of Al2O3 fibers.
129Xe NMR is used to study the adsorption of xenon in amorphous Al2O3 and Al2O3-ZrO2 fibers. Sintering affects the intensity of the NMR line of adsorbed Xe, and qual. this intensity is proportional to the degree of sintering. It definitely shows that the xenon adsorption sites have to be found in the pores which are affected by the sintering. Further, the chem. shift of adsorbed Xe is detd. as a function of both temp. and pressure. In the temp. dependence two regions can be discerned. In the low temp. region the curves for different pressures have the same curved shape and the lowest temp. and the chem. shifts become independent of the pressure. Above the transition temp., the chem. shifts become linearly dependent on the temp., while the pressure dependence follows a typical Langmuir-type pattern. A simple theor. model is proposed to explain the temp. and pressure dependence. For the low temp. region it is assumed that the Xe atom can move in a potential well due to interaction with an oxygen atom. For the high temp. region the temp. and pressure dependence of the chem. shift are described by the Langmuir model. This combination of two models can qual. describe the obsd. temp. and pressure dependences.
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