Formation of TiC<inf>x</inf> during reactive spark plasma sintering of mechanically milled Ti/carbon nanotube mixtures

In this study, powder mixtures of Ti with 5 and 10 wt% carbon nanotubes (CNT) were ball milled and subjected to spark plasma sintering (SPS) with an aim to prepare Ti-25 wt% TiC and Ti-50 wt% TiC composites. Changes in the powder particle size and the phase evolution were studied as a function of milling time. The effect of SPS temperature (800 °C, 1000 °C and 1200 °C) on the microstructure, phase evolution and the properties are presented. Reaction between Ti and CNT lead to formation of non-stoichiometric TiCx (x < 1) phase in all the compositions. Complete conversion to TiCx was observed at 1200 °C temperature for the Ti-CNT mixtures. CHN measurements were carried out on the powder and the compact to study the source of additional carbon in the samples. Microstructural studies indicated that completely dense TiCx was produced at 1200 °C from Ti-CNT powders, while the milled Ti powders resulted in fully dense Ti-TiCx composite. The effect of C/Ti ratio on the lattice parameter of TiCx was studied. Mechanical properties were measured using Vickers microhardness and Nanoindentation.