Preparation by mechanical alloying of Al powders with single-, double-, and multi-walled carbon nanotubes for carbon/metal nanocomposites

Nanocomposites were prepared via mechanical alloying (MA) of Al powders with single-, double, and multi-walled carbon nanotubes (SWCNTs, DWCNTs, and MWCNTs) as reinforcements in order to investigate the MA behavior and resulting mechanical properties depending on the types of the CNTs. While CNTs in general functioned as grinding aid preventing agglomeration of Al particles which typically accompanies ball-milling, dispersion of the CNTs within the Al particle matrix was dependent on the type of the CNTs: only the MWCNTs were uniformly incorporated into the Al matrix particles whereas the SWCNTs and the DWCNTs were not dispersed fully into the matrix. Nanocomposite samples prepared by plasma activated sintering of the MA product of MWCNT–Al mixtures showed structural soundness without the formation of observable defects or secondary phase clusters. Consequently, only in the MWCNT–Al nanocomposite samples, significant improvement of mechanical property as compared to sintered pure Al samples was observed. Possible origin of the improvements in mechanical properties, despite the predicted poor CNT–Al interfacial bonding, was proposed conceptually.