A review of 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 subject are also discussed.
We investigate the electrical properties of composite materials prepared as nano-and sub-micron-scale metal-oxide particles embedded in a commercial resin. The filler particles are barium titanate and calcium copper titanate. The physical and structural characteristics of the constituents and the fabricated composites are reported. Electrical characterization of the composite samples is performed using time-and frequency-domain dielectric spectroscopy techniques. The electrical breakdown strength of samples with nano-and sub-micron-sized particles have better electrical insulation properties than the unfilled resin.
In this article, the frequency dependent dielectric properties, ε(ω), of an “ideal” binary composite structure were investigated by using the finite element method in the frequency domain. The material properties of the phases, i.e., dielectric permittivity, ε, and direct-current conductivity, σ, were assumed to be frequency independent. Moreover, the inclusion phase was more conductive than the matrix phase. The inclusions were infinitely long unidirectional cylinders which could be assumed to be hard disks in two dimensions in the direction perpendicular to the cylinder direction. Three different inclusion concentration levels were considered, e.g., low, intermediate, and high. The calculated dielectric relaxations were compared with those of the dielectric mixture formulas in the literature and it was found that there were no significant differences between the formulas and the numerical solutions at low inclusion concentration. Furthermore, the obtained responses were curve fitted by the addition of the Cole–Cole empirical expression and the ohmic losses by using a complex nonlinear least squares algorithm in order to explain the plausible physical origin of the Cole–Cole type dielectric relaxation. The dielectric relaxations were Debye-like when the concentration of the inclusions were low. For intermediate and high concentrations, the responses obtained from the numerical simulations deviated from that of the Debye one, whose curve fittings with the Cole–Cole empirical expression were inadequate.
In this paper, we report the dielectric breakdown properties of a nanocomposite, a
potential electrical insulation material for cryogenic high voltage applications. The material
is composed of a high molecular weight polyvinyl alcohol and nanosized in situ synthesized
titanate particles. The dielectric breakdown strengths of the filled material samples,
measured in liquid nitrogen, indicate a significant increase in their strengths as compared
to unfilled polyvinyl alcohol. We conclude that nanometre-sized particles can be adopted as
a voltage stabilization additive.
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