Improving the strengthening efficiency of carbon nanotubes in titanium metal matrix composites

Titanium (Ti) metal matrix composites (TMCs) reinforced with multi-walled carbon nanotubes (MWCNTs) were prepared by spark plasma sintering (SPS). Different concentrations (0.5wt% and 1.0wt%) of MWCNTs were dispersed into the Ti matrix by high energy ball milling (HEBM) and solution ball milling (SBM). The impact energy provided to the powder mixtures during the dispersion processing was quantified and optimized to disperse MWCNTs into Ti matrix. The effect of dispersion processing parameters on the sp2 C-C network in MWCNTs, resultant microstructures and mechanical properties of TMCs was investigated. The interfacial reactions between MWCNTs and Ti matrix were controlled by retaining the crystallinity of MWCNTs during the processing stages of TMCs. The defects originated in MWCNTs during the synthesis of TMCs were quantified and their relationship was established with the strengthening efficiency of the MWCNTs in TMCs. The strengthening efficiency of MWCNTs in the composites consolidated from the powder mixtures with pre-sonicated MWCNTs were significantly enhanced as opposed to the composites consolidated from the powder mixtures prepared via solely HEBM process.