Growth of carbon nanotubes in six orthogonal directions on spherical alumina microparticles

Multi-walled carbon nanotubes (MWCNTs) of uniform diameter grow in six orthogonal directions on micrometer spherical alumina particles by chemical vapor deposition. A mixture of xylene and acetylene is used as the carbon source for the growth of CNTs. Detailed investigation shows that the MWCNT arrangement is greatly dependent on the geometry, size and crystallography of the alumina microparticles. Similar CNT growth is found on the pristine and high-temperature (1350 degrees C) treated particles under the experimental conditions used. Characterization of the treated particles reveals that the growth of CNTs occurs at the crystal step sites, which also exist on the surface of pristine microparticles. The CNT organization varies with the orientation of the crystal steps. The specific surface structures potentially determine the growth of CNTs in six orthogonal directions. The directions of the CNT bundles are normal to {0 0 0 2} or {1 (1) over bar 00} planes, according to selected area diffraction analysis by transmission electron microscopy. (C) 2011 Elsevier Ltd. All rights reserved.