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Journal of Nanomaterials
Volume 2007, Article ID 30389, 9 pages
http://dx.doi.org/10.1155/2007/30389
Review Article

The AC and DC Conductivity of Nanocomposites

1Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
2Materials Physics Research Institute, School of Physics, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa
3National Institute of Aerospace, 100 Exploration Way, Hampton, VA 23666, USA

Received 25 April 2007; Accepted 9 August 2007

Academic Editor: Christian Brosseau

Copyright © 2007 David S. McLachlan and Godfrey Sauti. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The microstructures of binary (conductor-insulator) composites, containing nanoparticles, will usually have one of two basic structures. The first is the matrix structure where the nanoparticles (granules) are embedded in and always coated by the matrix material and there are no particle-particle contacts. The AC and DC conductivity of this microstructure is usually described by the Maxwell-Wagner/Hashin-Shtrikman or Bricklayer model. The second is a percolation structure, which can be thought to be made up by randomly packing the two types of granules (not necessarily the same size) together. In percolation systems, there exits a critical volume fraction below which the electrical properties are dominated by the insulating component and above which the conducting component dominates. Such percolation systems are best analyzed using the two-exponent phenomenological percolation equation (TEPPE). This paper discusses all of the above and addresses the problem of how to distinguish among the microstructures using electrical measurements.