Effect of surface texturing by femtosecond laser on tantalum carbide ceramics for solar receiver applications

Tantalum carbide, as a Ultra-High Temperature Ceramic, is known to be characterized by intrinsic spectral selectivity, which makes it attractive for novel high-temperature thermal solar absorbers. However, a weakness point of TaC is the solar absorbance, which, in absence of any treatment, is usually lower than that of other materials currently under development for solar absorber applications. In the present work we have investigated the effect of surface texturing by femtosecond laser machining on this superhard material. Laser-induced microstructural and optical property changes have been characterized in two samples with different starting roughness and for four 'laser treatments each, as a function of the accumulated laser fluence. As the interaction with the laser beam takes place and gets stronger, both surface and chemical composition changes appear. Optical properties are heavily affected: solar absorbance considerably increases, at a slight expense of spectral selectivity.