Dynamically controlled formation of TiN by combustion of Ti in air

This paper studies the formation of titanium nitride (TiN) by combustion of Ti particles in air. It is proposed that the combustion reaction is a dynamically controlled process, in which the formation of TiN is fulfilled by delayed gas infiltration behind the propagation of combustion wave. With the addition of NH₄Cl or carbon black, the yield of TiN can be enhanced. The as-synthesized TiN grains show a terraced morphology with parallel layers stacked in the normal direction. It is thought that this terraced morphology has been derived from a surface-coarsening process. The parallel layers show regular hexagonal outlines and thus are considered to be (111) planes according to the symmetric characters of the FCC structure. The (111) texture is also revealed by X-ray diffraction results, where the relative intensity of (111) peak is clearly higher than the reference in the JCPDS card. In addition, nanoscale twinning areas are observed in TiN grains. From transmission electron microscopy (TEM) results, it is determined that the twinning plane is (111) and the twinning direction is [211]. The movement of atoms during twinning is discussed according to the FCC structure of TiN and high-resolution TEM images.