Carbon nanotube and in-situ titanium carbide reinforced titanium diboride matrix composites synthesized by reactive spark plasma sintering

Mechanically milled powder mixtures of Titanium and Boron containing 1, 2, 4 and 6 vol% multi-walled carbon nanotubes (CNT) were consolidated by reactive spark plasma sintering resulting in TiB2-TiC-CNT hybrid composites. Addition of CNT was found to affect the reaction rate for TiB2 formation which results in sudden volume shrinkage. Rod shaped TiC were formed due to reaction between Ti and CNT. TiB2-TiC-CNT hybrid composites having more than 96% relative density with nanosized TiB2 grains were obtained. XRD results revealed TiB2 and TiC as major and minor phases respectively. Unreacted CNT were observed in SEM and TEM. TiB2-TiC-CNT composites showed nanohardness of above 25 GPa and elastic modulus of 520 GPa. Indentation fracture toughness was improved by 55% (3.3±0.1 to 5.11±0.6) by the addition of 4 vol% of CNT. The effect of CNT addition on oxidation and co-efficient of thermal expansion is also presented.