Shenbao Jin

Self-propagating high-temperature synthesis of nano-TiCx particles with different shapes by using carbon nano-tube as C source

With using the carbon nano-tube (CNT) of high chemical activity, nano-TiCx particles with different growth shapes were synthesized through the self-propagating high temperature in the 80 wt.% metal (Cu, Al, and Fe)-Ti-CNT systems. The growth shapes of the TiCx particles are mainly octahedron in the Cu- and Al-Ti-CNT systems, while mainly cube- and sphere-like in the Fe-Ti-CNT system.

Effect of stoichiometry on the surface energies of {100} and {111} and the crystal shape of TiCx and TiNx

The surface energies of the {100} and {111} surfaces of TiCx and TiNx with different stoichiometries (x ≤ 1.0) were investigated using the density-functional theory, employing Perdew Wang 91 (PW91) under the generalized gradient approximation (GGA) method. The result explains the dominating effect of the TiCx and TiNx stoichiometry on their growth shapes and why TiCx and TiNx evolve from octahedron to truncated-octahedron and finally to sphere during the self-propagating high-temperature synthesis (SHS). With the increases in stoichiometry, both the {100} and {111} surface energy values decrease. However, the surface energy of the {100} surfaces decrease more quickly than that of the {111} surfaces, which means that the {100} surfaces tend to be more stable at quite high stoichiometries. In this case, the {100} surfaces gradually expose on the crystal growth shape, while the {111} surfaces gradually shrink. According to this result, through controlling the stoichiometry during the SHS, the TiCx and TiNx particles with different shapes can be obtained.

Effect of reactant C/Ti ratio on the stoichiometry, morphology of TiCx and mechanical properties of TiCx–Ni composite

TiCx with different morphologies were synthesized from combustion synthesis of Ni–Ti–C system by changing the reactant C/Ti ratio. High stoichiometry of TiCx changed the growth direction from (111) to (100) surface and therefore resulted in cubic morphology while high combustion temperature at high reactant C/Ti ratio led to the roughening transition of (100) surface and form spherical morphology.