Wideband electrical characterisation of carbon-based nanocomposites

Abstract

Nanocomposite materials are composed of two or more different materials having different physical properties forming distinct ‘phases’. At least one of these constituents has dimensions of the order of the nanometre and the properties of these nanoparticles lead to the creation of a unique composite material. In particular, nanocomposites based on high aspect ratio particles like carbon nanotubes should exhibit outstanding mechanical, thermal and electrical properties at very small particle content. Carbon-based nanocomposites are a rapidly growing field of investigation. The range of available shapes, types and properties of these composites is constantly increasing and that of their possible applications is wider still. In this thesis, the wideband electrical properties of these nanocomposite materials are investigated. First a thorough examination of the literature is presented. Different characterisation techniques are developed and their adequacy with the nanocomposite characteristics is discussed. A wideband, from DC to 40 GHz characterisation of polymer-CNT composites is presented in details and used to extract information on the material microstructure, as well as the influence of the nanoparticle content on the electrical properties. Specifically designed nanocomposites for particular applications are presented; from composite foams for EMI shielding applications to dispersed solutions of carbon particles exhibiting a non-ohmic behaviour. Finally, nanostructured membranes for fuel cell applications are also shown. The particular aim of this thesis is to find the best adequacy between characterisation method, material properties and required characteristics for a given application.(FSA 3) -- UCL, 201