Engineering carbon nanostructures : development of novel aerogel-nanotube composites and optimization techniques for nanotube growth

摘要

Carbon aerogels offer several unique advantages which make them ideal for evaluating a metal's ability to catalyze nanotube growth, including in situ carbothermic reduction of oxidized nanoparticles to their catalytic metallic phase as they form and production of a bulk quantity of nanoparticles which can be easily characterized. In this work, metal-doped carbon aerogels of seven transition metals were synthesized, characterized, and evaluated for their ability to catalyze growth of carbon nanotubes by thermal chemical vapor deposition (CVD). It was found that carbon aerogels doped with Fe, Rh, Re, Au, and Nb all catalyzed the formation of nanotubes in moderate to high yields, resulting in a direct growth of nanotubes on the exterior surfaces of aerogel monoliths. Ta was found to grow nanotubes only after thorough reduction of its oxides. Growth with W was inconclusive. CVD growth of nanotubes throughout the interior porosity of metal-doped carbon aerogels was also achieved by templating a network of interconnected macropores into the monoliths. Surface-based nanoparticles composed of rhenium, gold, and varying combinations of gold and rhenium were investigated for their ability to catalyze carbon nanotube growth.