Utilizing electrical, mechanical, adsorbent properties, and microwave response of carbon nanomaterials
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Carbon nanomaterials, specifically graphene and carbon nanotubes (CNTs) continue to gain enormous attention in multidisciplinary area including composite fabrication to biological applications. The main focus of this thesis is to utilize graphene or CNT as nanofiller to enhance the electrical, mechanical and thermal properties of polymer nanocomposites. However, the major challenge of maximizing the property transfer is to ensure effective mixing of nanofillers in the viscous polymer system. We used triphenylene derivative stabilized pristine graphene dispersions for the production of graphene loaded polyvinyl alcohol (PVA) composites by solution casting. The dispersion is aggregation resistant and homogeneously mixes in the aqueous solution of PVA. Hence the composites display improved electrical conductivity, Young’s modulus, and tensile strength in comparison to the baseline PVA. This is the first report of successfully using pristine graphene in fabricating PVA composites. Secondly, we emphasize on achieving electrical percolation in epoxy at extremely low loading of the filler and develop a facile method to create a segregated network of fillers in the matrix. It is done by making graphene or CNT loaded conductive aerogels where the fillers stays interconnected in the skeleton. The pores are then backfilled with polymer melt through capillary action and cured to make the composite. The advantage of this procedure is that it avoids the chance of filler aggregation. We report the lowest ever percolation threshold (~ 0.012 vol %) for any graphene based composites by following this procedure. Thirdly, various methods (dialysis, vacuum filtration, and spray drying) to remove the excess dispersants (not adsorbed onto graphene surface) from the colloidal dispersion of graphene are investigated. The removal has no or little effect on dispersion quality and significantly increases the electrical conductivity of graphene films. At last, the microwave induced heating of CNTs is employed to develop a novel quantitative detection technique in biological samples. Even a tiny fraction of CNTs (~ 0.008 µg CNT/mg sample) are reliably detectable according to this technique which is not possible by common analytical methods such as electron microscopy and Raman spectroscopy.