Also, at higher frequency, the dielectric constant is approximately constant which is due to the electronic polarization
The increasing of the conductivity is small at high frequencies; this is attributed to the electronic polarization
and the electronic charge carriers which travel by hopping process.
In general, charge polarization in MWCNT/polymer (nonpolar) composites originates from three sources, namely (1) interfacial polarization, (2) MWCNT polarization, and (3) electronic polarization of polymer.
The electronic polarization of polymer matrix is the third side of the charge polarization triangle in MWCNT/polymer composites.
In the frequency range from dozens of megahertz to several gigahertz, three main polarization phenomena contribute to the dielectric dispersive behavior of oil bearing reservoirs: the electronic polarization (rock's inherent permittivity), the molecular polarization (brine water molecules) and the interfacial polarization which is also called Maxwell-Wagner polarization.
It is known that dry rock matrix permittivity does not depend on frequency as it only benefits from electronic polarization, so it probably plays an insignificant role in rocks at the earth's surface.
In the SEOP method, electronic polarization is produced by optical pumping of alkali atoms (usually rubidium), and the polarization is transferred to the [.sup.3]He nuclei by the hyperfine interaction during collisions.
Electronic polarization of the potassium atoms occurs on a rapid time scale due to Rb-K spin-exchange collisions, hence high potassium polarization can be maintained.
It has been observed that the variation of AC conductivity as a function of frequency (not shown here) increases with the frequency for both the PMMA and the composites and as reported (18), the increase in AC conductivity at low frequency is due to the interfacial polarization and in the high frequency region, it is attributed to the electronic polarization
In the metastability-exchange method, electronic polarization
is produced by optical pumping of metastable helium atoms, and the polarization is rapidly transferred to the nucleus of the metastable atom via the hyperfine interaction.