Conclusions and Future Work

Abstract

This thesis has presented research regarding the electromechanical properties of a composite formed of graphite nanoparticles in a silicone rubber matrix. We have made the exciting discovery of a NDR region in the I–V characteristics of the composite at low temperatures. We have conducted a detailed study on the effects of volume fraction, filler type, probe separation and temperature dependence; combined with theoretical modelling of the LDOS in graphite and the tunneling current across a single graphite-silicone barrier. From this evidence we arrived at the conclusion that the NDR occurs due to the composite breaking up into domains of constant electric field, separated by highly resistive domain boundaries. These are identified as individual graphite nanoparticles whose orientation in the electric field favour conduction across an embedded bilayer graphene. An electric field opens a partial energy gap at the Fermi level causing the current carrying bilayer to undergo a semi-metal to insulator transition. The current therefore decreases, causing the NDR.