02_dielectric mixture - IEEE Transactionson Dielectrics and...

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IEEE Transactions on Dielectrics and Electrical Insulation Vol. 9 No. 5, October2002 809 Dielectric Mixtures: Electrical Properties and Modeling E. Tuncer, Y. V. Serdyuk, S. M. Gubanski Chalmers University of Technology. Gathenburg, Sweden ABSTRACT A review of the current state of understanding of dielectric mixture properties, and approaches to use numerical calculations for their modeling. are presented. It is shown that interfacial polarization can yield different non-Debye dielectric responses depending on the properties of the constituents, their concentrations and geometrical arrangements. Future challenges on the subiect are also discussed. 1 INTRODUCTION Many materials used in our daily life are composites, which often are made up of at least two constituents OJ phases. The outstanding mechanical properties of many composites, and especially the unique combination of low density with high strength and stiffness, have led not only to extensive research but also to highly developed technolo- gies [l-31. In comparison, relatively little attention was given to their other physical properties, which in parallel affected their use in electri- cal applications [P7]. The main advantage of composites is the ability to tailor materials for special purposes. Their applications are evolv- ing day by day through developments whichlead to better precision in their manufacturing. Designing of composite materials for electrical applications with a classical 'trial and error' approach requires much time and money However, by using computers, the modeling of desired properties of insulation systems can be estimated and corrected. The electrical prop- erties of the system, i.e. its conductivity and dielectric permittivity, are influenced by the properties of the constituents, interaction between them and geometrical configuration. One should not forget that insu- lating materials or dielectrics, as Faraday called them [a], show various properties at different voltages, temperatures, frequencies, moisture content and mechanical stresses. These should be considered in the design as well as in the diagnostics. From the early days of electromagnetic field theory predicting and calculating the dielectric properties of mixtures has been a challeng- ing problem of both theoretical and practical importance [4-7,9-13]. In composites, the polarization of charges due to the differences be- tween the electrical properties of the constituents plays an important role. Maxwell [14] was the first to notice this phenomenon when he con- sidered a binary layered structure and expressed the effective dielectric properties of the composite. When structures other than the layered arrangement of phases were studied [P7,15-17], it was realized that the problem was not trivial, and even the geometrical shapes [7,18-211 and arrangements of inclusions [21-281 played an important role in the electrical properties of composites.
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02_dielectric mixture - IEEE Transactionson Dielectrics and...

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