Papers by Keyword: Dielectric Dispersion

Abstract: Complex permittivity spectra of various concentrations (0.0 → 1.0) of n-Butanol and its mixtures with Valeronitrile were obtained in the radio and microwave frequency range (0.2 GHz to 20 GHz) using Vector network analyzer (VNA). Complex permittivity data points were fitted into Havriliak-Negami Model. CNLS fitting using LEVMW software used to obtain dielectric parameters. Excess static dielectric constant and excess inverse relaxation time for the binary mixtures were calculated and fitted in Redlich-Kister polynomial to derive the binary coefficients and standard deviations. Variation of these parameters were discussed in terms molecular interaction between molecular species.

Abstract: The dielectric and electric properties of poly (methyl Methacrylate) (PMMA) and Poly (vinyl Pyrrolidione) (PVP) in polar solvent have been studied in the frequency range of 20 Hz to 2 MHz at room temperature. The effect of polar solvent environment on the dielectric and electrical parameters such as the complex dielectric constant (Є*), relaxation times complex electrical modulus (M*) and complex impedance (Z*) has been analysed . Dielectric dispersion curves show that the polymer concentration plays an important role in governing its segmental motion in solvent solution. At low frequencies, the ionic conduction and electrode polarization seems to have dominant influence on the large increase of complex dielectric constant values.

Abstract: The Bi2Mn0.1V0.9O5.35-δ (BIMNVOX.10) thin films have been successfully deposited on the LaNiO3(LNO)/Si (100) substrates by chemical solution deposition process. The phases, morphology and electrical properties of samples have been studied. The BIMNVOX.10 films show a (00l)-preferred orientation and have a homogeneous distribution of grains. A low frequency dielectric dispersion observed in the films may be originated from the short distant diffusion of oxygen vacancies. The Cole-Cole plots of dielectric constant for the BIMNVOX.10 films appear semicircular arc with the center off the x-axis and deviate from the ideal mono-dispersive Debye model. The frequency dependent of ac conductivity for BIMNVOX.10 films follows the Joscher’s power law, mainly contributed to the grain resistivity and predicts the nature of an oxygen vacancies conduction process. The complex impedance spectra reveal that electrical process arises due to contribution from the grain interior and grain boundary effects.

Abstract: This paper examines the relative permittivity of irradiated and non-irradiated crude oil samples in the frequency range 0.1 – 100.0MHz and room temperature regulated at 25 ± 1oC. Samples of crude oil of mean specific gravity 0.780 ± 0.015 were irradiated for periods of two, four, six, eight and ten months respectively using a gamma radiation source (Cobalt 60) at a dose rate of 0.65mSv per hour. Dielectric measurements were made by using a Boonton RX meter type 250A admittance bridge manufactured by central research Laboratories, Inc, Red, Wing, Minnesota. Analysis of the resulting dielectric data revealed that both the irradiated and non-irradiated samples exhibited dielectric dispersion over the frequency range investigated. However, the relative permittivity values of the irradiated samples were found to be higher than those of the non-irradiated sample. This difference is understandable as it can be attributed to the ionization of atoms and weakening of molecular bonds in the irradiated samples. The increase in relative permittivity for the irradiated samples was observed to be time dependent as the longer the time of irradiation of sample the higher the value of its relative permittivity. Also, in this study, it was observed that the non-irradiated crude oil sample has longer relaxation time than the irradiated ones. The relaxation time decreases gradually with increasing irradiation time. This has physical significance on the basis of the molecular theory of matter and the fact that relaxation time is inversely proportional to relaxation frequency. These results are comparable with the work of other researchers for which similar trends have been observed.