TiCx-Ti2C nanocrystals and epitaxial graphene-based lamellae by pulsed laser ablation of bulk TiC in vacuum

Nonstoichiometric delta-TiCx, delta'/delta-Ti2C and 2-D turbostratic graphene-based lamellae were co-synthesized by pulsed laser ablation of bulk delta-TiC in a vacuum and characterized using X-ray diffraction, electron microscopy and optical spectroscopy. The predominant delta-TiCx occurred as submicron-sized particulates and nanocondensates with size dependent shapes (5 nm sphere vs. 10 and 15 nm cubo-octahedra), which tended to coalesce over well-developed (111) as a unit or impinged by the similar to(001) vicinal surface to form a [ 1 (1) over bar0] tilt boundary. The minor Ti2C nanocondensates occurred as cubo-octahedra for the cubic d'-phase and triangular plates with well-developed (0001), {1 (1) over bar 02} and {1 (1) over bar0 (4) over bar} faces for the trigonal delta-phase, which tended to coalesce over (0001) as a unit. The turbostratic graphene-based lamellae occurred as nanoribbons or an artificial epitaxy shell on delta-TiCx and delta'/delta-Ti2C to facilitate carbon vacancy diffusion. The present TiCx-Ti2C-graphene phase assembly with characteristic Raman modes sheds light on their natural dynamic occurrence in presolar settings. The bimodal UV-visible absorbances of this phase assembly in the form of nanoparticles may have potential photocatalytic and abrasive/ lubricant applications.