Effect of Internal Pore Sizes of the Silica Gel on the Dielectric Permittivity in the Frequency Range from 100 Hz to 8 GHz

Abstract

In the frequency range from 100 Hz to 8 GHz, three samples of silica gel powder with internal pores sizes of 4, 6 and 9 nm and different contents of adsorbed water and one sample of sandy globules with grain sizes close to silica gel sizes were studied. The powders were moistened with distilled water. It is shown that at frequencies above 10 MHz, the differences in the complex relative dielectric permittivity (CRP) of silica gels with different pore sizes with the same moisture are negligible. In two samples of silica gel with similar values of the maximum amount of adsorbed water the CRP depends mainly on the size of internal pores. The CRP values of the third sample differ from the CRP of other samples due to the higher content of adsorbed water. The relaxation processes observed in the studied frequency range exist only in the presence of adsorbed water. The occurrence of films of liquid water on the surface of the grains leads to the appearance of an intensive relaxation process with a low relaxation frequency that is outside the bounds the studied frequency range.