Selective generation of laser-induced periodic surface structures on​ Al₂O₃-ZrO₂ -Nb composites​

Laser-induced periodic surface structures (LIPSS) were selectively fabricated on the metal phase of Al₂O₃-nZrO₂-Nb (78.3-1.7-20 vol.%) ceramic matrix compo­sites. For this purpose, sample surfaces were irradiated with fs-laser pulses (τ=300fs, λ=1025nm) of different laser peak fluences ranging from 0.23 to 0.40 J/cm². The structured surfaces were characterized by scanning electron micro­scopy (SEM), atomic force micro­scopy (AFM), attenuated total reflectance Fourier transform infrared spectro­scopy (ATR-FTIR), and by measuring the water contact angle. Well-pronounced LIPSS with a period of Λ≈750nm and a height of h≈263nm were found solely on the metal phase of the composite when applying the highest fluence whereas no structural and chemical modi­fications were found on the sur­face of the ceramic matrix. This can be explained by the different light absorp­tion behaviour of both phases, which results in different ablation thres­holds. The water contact angle of compo­site surfaces was success­fully reduced from 68.4° for untreated samples to 40.9° for struc­tured samples. Selectively struc­tured compo­sites with adjustable wettability are of particular interest for biomedical and tribo­logical appli­­cations.