On the Permittivity of Nanodielectrics

Vaughan, Alun (2011) On the Permittivity of Nanodielectrics. Dielectrics 2011, The University of Kent, Canterbury, United Kingdom. 12 - 14 Apr 2011.

Record type: Conference or Workshop Item (Other)

Abstract

A wide range of different nanocomposite materials have been produced by adding nanometric fillers to insulating polymers and, because of attractive properties that such materials can exhibit, such systems have attracted considerable interest. Experimental studies of the composition dependence of the permittivity of nanocomposites have revealed that a local minimum exists in the real part of the permittivity at low nanofiller concentrations, even when the permittivity of the nanofiller material exceeds that of the polymer matrix. This behaviour cannot be explained by conventional mixing laws and, consequently, it has been suggested that such observations provide evidence for the existence of an interphase between the nanofiller and the matrix which exhibits modified properties. This paper will describe a simulation study that set out quantitatively to test this hypothesis. First, a random three phase model of a nanocomposite will be described which is based upon isometric nanoparticles surrounded by an interphase embedded within a matrix. In this, the nanoparticles are added sequentially to the system and the cells not occupied by nanoparticles are partitioned probabilistically between the matrix and the interphase. Comparison of this approach with periodic lattice models with various symmetries and dimensionalities reveals that both approaches converge in the limit that the nanoparticle fill fraction ?p ? 0 and at high values of ?p. By varying the parameter values input into the model, it is possible to reproduce the form of the behaviour seen experimentally. The implications of the derived parameters will discussed.

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