Authors: M. Olek, K. Kempa, S. Jurga and M. Giersig
Affilation: Caesar - Research Center, Germany
Pages: 167 - 170
Keywords: carbon nanotubes, nanoindentation, composites, hardness, Young's modulus, silica coating
Nanomechanical properties of polymer composites, reinforced with silica coated multiwall carbon nanotubes (MWNT), have been studied using the nanoindentation technique. The nanohardness and the Young’s modulus have been found to increase strongly with the increasing content of these nanotubes in the polymer matrix. Similar experiments conducted on thin films containing MWNT, but without silica shell, revealed that the presence of these nanotubes does not affect nanomechanical properties of the composites. Even strong interconnectivity between carbon nanotubes (CNT) and polymer and high CNT concentration (as is obtained for layer-by-layer structures) does not lead to a significant increase of the nanomechanical reinforcement under indentation load (1). While CNT have a very high tensile strength due to small nanotube stiffness, composites fabricated with CNT may exhibit inferior toughness. The silica shell on the surface of a nanotube enhances its stiffness and rigidity. Our composites, at 4wt% of the silica coated MWNT, display maximum hardness of 120 ± 20 MPa, and the Young modulus of 9 ± 1 GPa. These are respectively 2 and 3 times higher than those for the polymeric matrix. We show a method for the silica coating of MWNT that is a simple and efficient technique, adoptable to largescale production.