Dielectric Constants of SiO2 and RF Aerogels Measured by a Response Function Method

Abstract

We measured the real and imaginary part of the dielectric constant e of organic resorcinol-formaldehyde (RF)- and inorganic silica (SiO2) aerogels. The samples were used as the capacitive part of a low pass filter. Values of e were obtained from the response function of this filter in the frequency range from 1 Hz–50 kHz. The RF aerogels were made by polycondensation of resorcinol and formaldehyde, the SiO2 aerogels via hydrolysis and polycondensation of tetramethoxysilane in water. The wet gels were supercritically dried in CO2. Two density series of RF aerogels (density range from 380 up to 880 kg/m3) both differing in primary particle size as well as one density series of SiO2 aerogels (3 samples, densities 120, 180 and 240 kg/m3) were investigated.