A model for the study of the effective quasistatic conductivity and permittivity of dispersed systems with particlehost interphase, within which many-particle polarization and correlation contributions are effectively incorporated, is presented. The structure of the system's components, including the interphase, is taken into account through modelling their low-frequency complex permittivity profiles. The model describes, among other things, a percolation-type behavior of the effective conductivity, accompanied by a considerable increase in the real part of the effective complex permittivity. The percolation threshold location is determined mainly by the thickness of the interphase. The "double" percolation effect is predicted. The results are contrasted with experiment.

We analyze, without resort to any model field-mixing scheme, the leading temperature-dependent term in the 'diameter' of the coexistence curve asymptotically close to the vapor-liquid critical point. For this purpose, we use a simple non-parametric equation of state which we develop by meeting several general requirements. Namely, we require that the desired equation (1) lead to correct asymptotic behavior for a limited number of the fluid's parameters along selected thermodynamic paths, (2) reveal a Van der Waals loop below the critical point, and (3) be consistent with a rigorous definition of the isothermal compressibility in the critical region. For the temperature interval in question, the proposed equation approximates experimental data with an accuracy comparable to those given by Schofield's parametric equation and by other authors' equations. The desired term is obtained by applying the Maxwell rule to the equation and can be represented as D 2β |τ | 2β , where |τ | = |T − Tc|/Tc and β is the critical exponent for the order parameter. The amplitude D 2β is determined explicitly for the volume-temperature and entropy-temperature planes.

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Based upon our compact group approach and the Hashin-Shtrikman variational theorem, we propose a new solution, which effectively incorporates many-particle effects in concentrated systems, to the problem of the effective quasistatic permittivity of dispersions of graded dielectric particles. After the theory is shown to recover existing analytical results and simulation data for dispersions of hard dielectric spheres with power-law permittivity profiles, we use it to describe the effective dielectric response of nonconducting polymer-ceramic composites modeled as dispersions of dielectric core-shell particles. Possible generalizations of the results are specified.

Based on the method of compact groups of inhomogeneities, we formulate new mixing rules for suspensions of charged insulating particles. They express the quasistatic conductivity and permittivity of a suspension in terms of the effective geometric and dielectric parameters of the particles, electric double layers (EDLs), and suspending liquid. Also, we present our low-frequency impedance measurements of the conductivity and permittivity of Al 2 O 3isopropyl alcohol nanofluids as functions of Al 2 O 3 -particle volume concentration. Our rules give good fits for most of these data and allow us to estimate, among other things, the effective thickness, conductivity, and permittivity of the EDLs. The experimentally-recovered values agree well with elementary theoretical estimates suggesting the charging of the particles through preferential adsorption of contaminant ions. The possible effects of other mechanisms on the effective conductivity and permittivity of suspensions are also discussed.