Growth and characterization of multi-walled carbon nanotubes at NASA Glenn Research Center

Aligned multi-walled carbon nanotubes were prepared by the injection chemical vapor deposition (CVD) method using an iron-based organometallic compound as the catalyst source and toluene as the solvent. The concentration of the catalyst precursor was found to influence both the growth habit of the nanotubes, as well as the amount of iron in the deposited material. As deposited, the multi-walled carbon nanotubes contained as little as 2.8% iron by weight. The material was characterized by scanning electron microscopy, tunneling electron microscopy, Raman spectroscopy and thermogravimetric analysis. Using a second synthetic method, multi-walled carbon nanotubes were grown directly onto Co-coated stainless steel (SS) metal supports. Coulometric analysis of the cyclic voltammograms obtained for the carbon nanotube coated electrodes yielded lithium ion storage capacities as high as those observed for more conventional carbon materials, providing evidence that all the multi-walled carbon nanotubes within the entire ensemble are electrochemically active.