Laser ablation synthesis of tantalum carbide particles with specific phase assemblage and special interface

Abstract

Pulsed laser ablation of bulk TaC in vacuum under a high power density was used to fabricate fine-sized tantalum carbide particles, i.e., γ-TaC1−x with varied extent of carbon deficiency and α-Ta2C surrounded by an amorphous phase of Ta-doped carbon clusters or lamellae according to X-ray and electron diffraction. The predominant γ-TaC1−x has a high x value (~0.4) and almost spherical shape when rapidly solidified as submicron-sized particulates, whereas x ~ 0.2 and facetted with occasional {111} coalescence twin when condensed as nanoparticles. The minor α-Ta2C occurred either as nanocondensates with hexagonal crystal form or as a stable epitaxial intergrowth with the γ-TaC1−x particulate having close-packed planes in parallel with the precipitation process. The γ-TaC1−x and α-Ta2C nanocondensates were also coalesced approaching a secondary relationship, i.e., [011]TaC1−x//[01\( \overline{ 1} \)0]Ta2C and (100)TaC1−x//(0001)Ta2C having a fair coincidence site lattice at the interface. The refractory materials have a bimodal minimum band gap (ca. 3.8 and 2.3 eV) for potential optocatalytic and tribology applications at high temperatures.