On the ex situ and in situ doping of refractory Ta by pulsed laser ablation

Ex situ and in situ doping processes of refractory Ta were accomplished by pulsed laser ablation of bulk Ta in vacuum with C–O–H supply from C-coated collodion film and within tetraethyl orthosilicate (TEOS), respectively. Analytical electron microscopic observations of the resultant particulates and condensates indicated that the former process involved interdiffusion in the condensed state to form two kinds of core–shell structures, i.e., C–O–H doped Ta with α-type (bcc) core and lamellar shell and O–H doped γ-TaC1−x with amorphous Ta–C–O–H surrounding, respectively, for potential wear and lubrication applications at high temperatures. In situ TEOS mediation, however, enhanced solute trapping to form Si–C–O–H overdoped α-Ta with significant tetragonality (c/a ratio up to 1.27) and Si–O–H doped γ-TaC1−x with {111}γ twin/fault and occasional epitaxial relationship [ $$ \overline{1} $$ 23]α//[ $$ \overline{1} $$ 12]γ; (121)α//( $$ \overline{1} $$ 1 $$ \overline{1} $$ )γ due to particle coalescence. Such Si–C–O–H mediated Ta particles may have potential optocatalytic applications.