Synthesis and characterizations of amorphous carbon nanotubes / gold particles hybrid materials / Lim Yu Dian

Carbon nanotubes (CNT) have attracted great attentions due to its unique properties. However, most works being carried out focus on crystalline CNT. In this work, amorphous CNT (a-CNT) were synthesized successfully via a simple chemical technique at 220 °C in a short period of time. Surface morphological studies revealed that as prepared nanotubes present in agglomerated tubular structures with open ends, having diameter of 51.6 nm. The diameter of a-CNT reduced to 40 nm upon functionalization with nitric acid and further reduced to 10.2 nm as treated with auric chloride solution due to introduction of defective sites by these treatments. Both structural and elemental studies confirmed that the nanotubes were carbon and amorphous. From zeta potential measurement, it was found that nitric acid served as the most effective oxidation agent in functionalizing a-CNT with carboxyl groups compared to citric, sulphuric, and hydrochloric acids. Oxidation of nanotubes increased dispersion stability and ensured the successful hybridization between the a-CNT and gold (Au) nanoparticles. Thermal stability of a-CNT decreases with decorations of gold particles on its surface as per findings in Thermogravimetry Analysis (TGA). Electrical conduction are proven to be improved by surface modification where functionalized a-CNT has lower electrical resistivity than as-synthesized a-CNT, and the electrical resistivity decreases significantly with increasing gold content. As-synthesized and modified a-CNT/Epoxy composites exhibits lower electrical resistivity when cured in room temperature compared to 15 ºC, where exception was found on functionalized a-CNT. Through transference number measurement, gold particles are found to contribute to the overall electrical conduction via electron conduction