Polietilen ince filmin dielektrik özelliklerinin frekans, sıcaklığa bağlı davranışı ve camsı geçiş sıcaklığının tespiti

Abstract

 Determination of glass transition temperature by VFT model  Higher dielectric constant of PE thin film compared to dielectric constant of bulk PE  Determining glass transition temperature of PE thin film at higher temperatures than glass transition temperature of bulk PE Figure A. The dependence of the frequency value at which the maximum dielectric loss is observed from the dielectric loss obtained from the dielectric loss graph for 35000 g/mol and 750 nm thick polyethylene (PE) thin film (red dots and VFT fit curve) and the temperature dependence of the frequency values at which the maximum electric modulus is observed from the electric modulus graph (blue dots and activation curve) Purpose:The aim of this article is to analyze dielectric properties and glass transition temperature of PE thin film in comparison to bulk PE in order to evaluate the possible application opportunities of PE thin film in enery storage systems. Theory and Methods: PE thin film samples were deposited by thermal evaporation method between Al thin film electrodes under 10-5 Torr vacuum conditions. The dielectric spectroscopy measurements were operated by high frequency empedance analyzer. Results: The results show that thermal evaporation process causes breakage of PE main chain and occurance of oligomers and radicals. These oligomers and radicals may be the reason of increasing dielectric constant as a result of space-charge polarization. Also, the oligomers and radicals may react with each other and the main chain and cause the construction of cross-linked network. The presence of this network is the reason of increasing glass transition temperature. Conclusion: The results obtained for the change of dielectric constant and glass transition temperature show that PE thin films can be thought as candidate for organic energy storage systems.