THERMALLY STIMULATED DEPOLARIZATION (TSD) CURRENTS IN ADSORBED PHASES ON SILICA

The low-temperature (LT) TSD spectra of water and methyl alcohol adsorbed on Aerosil have been experimentally resolved. The variation of the area under the peaks with relative pressure (partial dielectric isotherms) have been studied and correlated with the adsorption isotherms. The relationship between the peak areas and the adsorbed amount suggest peaks I, II, and III be attributed to the dipolar polarization of the water or methyl alcohol molecules H bonded to the surface OH groups. The lengthening of the relaxation times as compared with that of the bulk liquid is explained in terms of entropy change on adsorption. In contrast, peaks IV and IV* are probably due to the dielectric polarization into small-size molecular aggregates. The fine structure of the TSD spectrum of adsorbed water on Aerosil is also compared with hertzian spectra of water adsorbed on silica.