Spark plasma sintering of the nonstoichiometric ultrafine-grained titanium carbides with nano superstructural domains of the ordered carbon vacancies

We report here spark plasma sintering (SPS) of the nonstoichiometric ultrafine-grained TiCx with the simultaneous formation of ordered carbon vacancies. The SPS-sintered TiCx exhibits interesting laminar microstructure with grains of ∼250 nm in average size. The cubic superstructure of the ordered vacancies in the C sublattice is found to exist in nano domains. With the increase of carbon content, the observed quick drop in the superstructural domain size indicates that the ordering length of the carbon vacancies depends strongly on the carbon content or the vacancy concentration. In comparison to the case of disordered carbon vacancies, the greatly enhanced compressive strength is observed due to the presence of ordered carbon vacancies.