Diameter- and length-dependent self-organizations of multi-walled carbon nanotubes on spherical alumina microparticles

Multi-scale hybrid structures of multi-walled carbon nanotubes (MWCNTs) and micrometric alumina particles (mu Al2O3) have been produced. The hybrid structures are obtained by in situ grafting carbon nanotubes (CNTs) on spherical mu Al2O3 particles using an easy chemical vapor deposition method, without any pre-patterned catalyst treatment. The study of the influence of temperature and hydrogen ratio shows three regular hybrid structures defined according to CNT arrangement on mu Al2O3. Furthermore, the organization modes demonstrate that the hybrid structures are strongly dependent on the diameter, length and area number density of CNTs. This dependency has been explained using a proposed nano-cantilever beam model. it evaluates the maximum deflection of one CNT due to weak van der Waals interactions. The model analysis shows that the MWCNT organizations are a result of varying competitive interactions between MWCNT rigidity and their attractive forces on the large curvature surface of mu Al2O3. In addition, the influence of specific characteristics of mu Al2O3 on hybrid structures is also discussed. (C) 2009 Elsevier Ltd. All rights reserved.