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

Nonstoichiometric δ-TiC x , δ′/δ′′-Ti 2 C and 2-D turbostratic graphene-based lamellae were co-synthesized by pulsed laser ablation of bulk δ-TiC in a vacuum and characterized using X-ray diffraction, electron microscopy and optical spectroscopy. The predominant δ-TiC x 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 ~(001) vicinal surface to form a [11&cmb.macr;0] tilt boundary. The minor Ti 2 C nanocondensates occurred as cubo-octahedra for the cubic δ′-phase and triangular plates with well-developed (0001), {11&cmb.macr;02} and {11&cmb.macr;04&cmb.macr;} faces for the trigonal δ′′-phase, which tended to coalesce over (0001) as a unit. The turbostratic graphene-based lamellae occurred as nanoribbons or an artificial epitaxy shell on δ-TiC x and δ′/δ′′-Ti 2 C to facilitate carbon vacancy diffusion. The present TiC x -Ti 2 C-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. Faceted δ-TiC x and δ′′-Ti 2 C nanocondensates co-existing with ribbon-like graphene-based lamellae with a 2-D turbostratic structure.