High strength metal-carbon nanotube composites

Uniform dispersion of pre-synthesized nanotubes in metal matrices is difficult to achieve, and there is substantial damage to the nanotubes during subsequent composite fabrication. The demonstration of an in-situ process involving chemical vapor deposition of single-wall and multi-wall carbon nanotubes into iron matrices without the concomitant formation of iron carbides is reported here. It was found that the yield strength of carbide-free iron-carbon nanotube composites increased up to 45% with about 1 wt % of infiltrated single wall carbon nanotubes (SWNTs), and 36% with -1 wt % multiwall carbon nanotubes (MWNTs), relative to that of similarly treated pure iron matrices of the same piece density. Vickers hardness coefficients were also substantially enhanced -74% and 96%, respectively, for composites with SWNTs and MWNTs relative to the metal matrices without nanotubes.