Journal of Surface Science and Technology

D. J. Sharmila ¹, J. Brijitta ², R. Sampathkumar ¹

Affiliations
1 Department of Physics, Sathyabama University, Chennai-600119, Tamil Nadu, IN
2 Center for Nanoscience and Nanotechnology, Sathyabama University, Chennai-600119, Tamil Nadu, IN

Abstract

Polypropylene and zinc oxide nanorods composites were prepared by combination of solution and mixture melting methods. Dielectric properties of the composite thin films were studied to see if zinc oxide nanorods have effect on the dielectric properties of polypropylene thin film. Introduction of zinc oxide nanorods at low filler content in the polypropylene matrix significantly improves the dielectric constant of the matrix. Simultaneously the structure of the composites was characterized by UV, XRD and SEM to understand the features in the structure that determine the functionality of the material. Composites with different weight percentage of zinc oxide nanorods show better absorption in the UV region compared to polypropylene matrix. This is due to the inherent capability of nano zinc oxide to absorb in the UV region. X-ray diffraction pattern of nanocomposites show sharp and highly intense peaks whereas neat polypropylene shows less intense peaks. This may due to the development of crystallinity in the polymer. Uniform distribution of zinc oxide which have a width of around 160-200 nm is observed in the SEM photographs of composites.

Keywords

Film Capacitor, Dielectric Properties, Polypropylene, Zinc Oxide Nanorods Composites.

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R. Sampathkumar ¹, A. V. Aswathy ¹, V. Balachandar ¹

Affiliations
1 Department of Physics, Sathyabama Institute of Science and Technology, Chennai - 600119, Tamil Nadu, IN

Abstract

Composites of polypropylene with different weight percentages of ZnO-TiO₂ core-shell nanoparticles were prepared by the combination of solution and mixture melting methods. Dielectric properties of polypropylene composite films were studied at frequencies ranging from 50 Hz to 5 MHz at four different temperatures (313, 333, 353, and 373 K). It is observed that the dielectric constant reduces quickly in the low-frequency range followed by a near frequency independent behavior above 1 KHz. The dielectric properties of composites at low frequency can be explained by interfacial polarization or Maxwell-Wagner-Sillars effect. It is also observed that the dielectric constant reaches the maximum value at 3 wt% of ZnO-TiO₂, which is the percolation threshold of nanocomposite. As the weight percentage of ZnO-TiO₂ increases beyond the percolation threshold up to 7%, the dielectric constant of the nanocomposites decreases. The dielectric loss of the composites follows the similar trend with frequency as the dielectric constant. A sharp increase in the dielectric loss of the nanocomposite observed near the percolation threshold is due to leakage current produced by the formation of conductive network by ZnO-TiO₂ core-shell nanoparticles. Further, peaks in the loss tangent observed for the nanocomposite systems indicating the appearance of a relaxation process. These relaxations peaks were shifted to higher frequencies as the particle content increased, since relaxation processes were influenced by the interfacial polarization effect which generated electric charge accumulation around the ZnO-TiO₂ core-shell nanoparticles.

Keywords

Dielectric Properties, Film Capacitor Application, Nanocomposites, Percolation Threshold, Polypropylene Matrix, ZnO-TiO₂ Core-Shell Nanoparticles.

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R. Sampathkumar ¹, V. Balachandar ¹, D. Gopalakrishnan ¹

Affiliations
1 Department of Physics, Sathyabama Institute of Science and Technology, Chennai – 600119, Tamil Nadu, IN

Abstract

Dielectric relaxation studies of acetate buffer solutions of Sodium Dodecyl Sulphate (SDS- anionic), Cetyl Trimethyl Ammonium Bromide (CTAB- cationic), Tween 80 (TW-80-non-ionic), Betaine Anhydrous (BA- zwitterionic) surfactants have been examined in the frequency region between 1GHz and 25GHz for various concentrations of surfactants at the temperatures of 283, 288, 293 and 298K using time domain dielectric spectroscopy. The obtained corrected loss spectra of all the amphiphiles except betaine anhydrous in acetate buffer solution depicted peaks near 1-2GHz and 15GHz, respectively. For betaine anhydrous, expected peak was not observed in the 1-2GHz frequency region. The peak ascertained near 15GHz, and another peak about 1-2GHz was accorded to free water relaxation and bound water reorientation of the surfactant micelles, and has acquired the reliance of temperature with concentration in detail. Single Debye and Cole-Cole function was employed to compute the relaxation times of free water and bound water, respectively. The Arrhenius plot was used to calculate the enthalpy and entropy for the micelle forming surfactants.

Keywords

Cole-Cole Plot, Complex Permittivity, Dielectric Relaxation, Hydration, Micelles, Surfactants, Time Domain Reflectometry, Thermodynamic Parameters.

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