On complex permittivity of dilute random binary dielectric mixtures in two-dimensions

Influence of number of particles considered in numerical simulations on complex dielectric permittivity of binary dilute dielectric mixtures in two-dimensions are reported. In the simulations, dodecagons (polygons with 12-sides) were used to mimic disk-shaped inclusions. Using such an approach we were able to consider $16^2$ particles in a unit-square. The effective dielectric permittivity of the mixtures were calculated using the finite element at two different frequecies which were much higher and lower than the characteristic relaxation rate of the Maxwell-Wagner-Sillars polarization. The results were compared to an analytical solution. It was found that the permittivity values at low frequencies were inside Wiener bounds however they violated the Hashin-Shtrikman bounds.Comment: 3 figures, submitted to Turkish Journal of Physic

A formula for dielectric mixtures

Dielectric properties of material mixtures are of importance in diagnostics, characterization and design of systems in various engineering fields. In this Letter, we propose a peculiar dielectric mixture expression, which is based on the dielectric relaxation phenomena and the spectral density representation [E. Tuncer J. Phys. Condens. Matter 17(12) L125 (2005)]. The expression is tested on several composite systems. Results illustrate that the proposed expression can be used to obtain valuable structural informations in composites, even for highly filled, bi-percolating, systems. Lastly, the proposed expression is an alternative to other existing homogenization formulas in the literature

How round is round? On accuracy in complex dielectric permittivity calculations: A finite-size scaling approach

Accuracy in complex dielectric permittivity calculations in binary dielectric mixtures in two-dimensions are reported by taking into account the shape of the inclusion phase. The dielectric permittivity of the mixtures were calculated using the finite element, and the permittivities were estimated by two different procedures. The results were compared with those of analytical models based on mean field approximation and regular arrangement of disks. We have approached the problem emphasizing the finite-size behavior in which regular polygons with $n$ sides were assumed to mimic the disk inclusion phase. It was found that at low concentrations, $< 30$, considering an decagon ($n=10$) cause an error of $<0.1$ in the effective medium quantities compared with the results obtained using the analytical models.Comment: 13 pages 5 figures, submitted Turkish Journal of Physic

Dielectric properties of a two dimensional binary sytem with ellipse inclusions

A two-dimensional binary composite system composed of ellipse inclusions and a host medium is considered. Dielectric permittivity of the system is calculated as a function of orientation angle, the volume fraction of the inclusions and their excentricity using the finite element method. It was observed that both the orientation of the inclusions in the field and their excentricity have significant effects on the dielectric permittivity.Comment: LaTeX, 5 pages, 11 figures. Unpublishe

Dielectric mixtures: Importance and theoretical approaches

Physics of dielectric mixtures are presented to stimulate discussion and to provide information on the recent advances in this topic

Electrical properties of polyetherimide thin films: Nonparametric dielectric reponse analysis with distribution of relaxation times

High temperature polymeric materials for electrical insulation and energy storage are needed for transformational power applications such as pulsed-power and hyrid electrical vehicles. One of the candidate materials has been polyetherimide, an amourphous thermoplastic with a glass transition over 200C. Here dielectric studies on the material are reported by taking into account the polarization and conduction processes in the polyetherimide

The Landau-Lifshitz/Looyenga dielectric mixture expression and its self-similar fractal nature

In this paper, dielectric permittivity of dielectric mixtures is discussed in view of the spectral density representation method. A distinct representation is derived for predicting the dielectric properties [Tuncer E 2005 J. Phys. Condens. Matter 17 L125]. In order to illustrate the strength of the representation and confirm the proposed hypothesis, Landau-Lifshitz/Looyenga expression is selected, and the structural information of the mixture is extracted. Both a recently developed numerical method to solve inverse integral transforms and the proposed empirical scaled permittivity expression are employed to estimate the spectral density function of the Landau-Lifshitz/Looyenga expression. In the simulations the concentration q of the inclusions phase are varied. The estimated spectral functions for the mixtures with different inclusion concentration compositions show similar spectral density functions, composed of couple of bell-shaped distributions, with coinciding peak locations. We think therefore that the coincidence is an absolute illustration of a self-similar fractal nature of mixture topology (structure) for the considered Landau-Lifshitz/Looyenga expression. Consequently, the spectra are not altered significantly with increased filler concentration level--exhibit a self-similar spectral density functions for different concentration levels. We conclude that the Landau-Lifshitz/Looyenga expression is therefore suitable for complex composite systems that have hierarchical order in their structure, which confirms the finding in the literature.Comment: 13 pages, 17 figures, 2 table

Analogy between dielectric relaxation and dielectric mixtures: Application of the spectral density representation

The spectral representation is an effecient tool to explore electrical properties of material mixtures. It separates the contributions of geometrical topology and intrinsic properties of the constituents in the system. The aim of this paper is to derive an expression for the spectral density representation, which favors dielectric relaxation phenomenon. This unfamiliar form is distinct in a way that the existing dielectric relaxation models and data analysis tools can be employed for extracting the spectral density function of a given system

Elastic properties of cellular polypropylene films: Finite element simulations and their comparison with experiments

The Young's modulus of a two-dimensional truss-like structure is simulated by using the finite element method. A power-law expression is proposed for the effective Young's modulus of the system. The obtained numerical results are compared with the experimental data of the {\em anisotropic thin cellular polypropylene films}. At high solid volume fractions ($>0.4$), the average shape of the cells are lateral, and their dimensions have around one-to-five ratio. As the samples are inflated further, volume fraction of the solid is decreased, the average shape approach a diamond-like structure with one-to-two ratio. In addition the effective Young's modulus of the system increases. It is concluded that valuable structural information can be obtained by analyzing the experimental data and the numerical simulations, which take into account the material's micro-structural information, simultaneously.Comment: 7 figures and 2 table

High temperature viscosity measurement system and viscosity of a common dielectric liquid

A device to measure viscosity of dielectric oils was developed. The device is an inset to an autoclave system where the temperature and the pressure could be controlled. The device is capable of measuring viscosities up to 400C and 5000psi, which are the limits of our autoclave at the moment