Processing and applications of carbon based nano-materials.

摘要

Carbon-based nanomaterials, including single walled carbon nanotubes (SWNTs) and graphite nanoplatelets (GNPs, multi-layer graphene), possess exceptional electrical, thermal and mechanical properties coupled with high aspect ratio and high temperature stability. These unique properties have attracted increased attention during the past decade. These materials form the basis of the work presented here, which includes research targeting fabrication, processing and applications in new composites and devices.; As-prepared SWNTs are typically contaminated with amorphous carbon as well as metal catalyst and graphitic nanoparticles. We have demonstrated an efficient approach for removing most of these impurities by the combination of nitric acid treatment and both low speed (2000 g) and high speed centrifugation (20,000 g). This approach gives rise to the highest-purified arc-discharge SWNTs which are almost free from impurities, and in addition are left in a low state of aggregation.; The new purification process offers a convenient way to obtain different grade of SWNTs and allows the study of the effect purity on the thermal conductivity of SWNT epoxy composite. Purified functionalized SWNTs provide a significantly greater enhancement of the thermal conductivity, whereas AP-SWNTs allow the best electrical properties because of their ability to form efficient percolating network. We found that purified SWNTs provide ∼5 times greater enhancement of the thermal conductivity than the impure SWNT fraction demonstrating the significance of SWNTs quality for thermal management.; The introduced GNPs have directed the thermal management project to a new avenue due to the significant improvement of the thermal conductivity of the composites in comparison with that of SWNTs. A novel process was demonstrated to achieve a 4-graphene layer structure referred to GNPs with a thickness of ∼2 nm. This material was embedded in an epoxy resin matrix and the measured thermal conductivity of the composite is up to 10 W/m·K with 40 vol% loading, which surpasses the performance of conventional fillers that require a loading of ∼70 vol% to achieve these values.; The highly purified SWNTs have further been utilized to fabricate transparent and conducting SWNT films on glass and PET (polyethylene terephthalate) substrates by the filtration and PDMS stamping techniques. The measured transmittance and electrical resistance of SWNT film on PET substrate are comparable to indium tin oxide (ITO), but maintain stable electrical properties with bending.