Femtosecond Laser Processing of AlN Ceramics for Gradient Wettability Control

Femtosecond laser processing gradient wettability is emerging as a powerful technology to control the wettability of surfaces due to its several advantages such as low pollution, good stability, and short processing cycle. A micro-textured surface with a stripe groove structure was processed on the surface of an AlN ceramic using a 1030 nm femtosecond laser. The surface roughness, the chemical composition, contact angle, and surface microstructures were determined using optical profilometry, X-ray photoelectron spectroscopy, contact angle measuring instrument and, scanning electron microscope, respectively. The wettability surfaces of different gradients were obtained by changing the number of laser scanning passes. Moreover, the flow state of the droplet on the gradient wettability surface was observed via a high-speed camera. The experimental results show that as the surface roughness increases, the surface wettability gradually becomes hydrophilic. Furthermore, the hydrophobic loss is due to the increase in the number of hydrophilic C–O bonds and to the reduction of the hydrophobic C–C bonds on the surfaces. And, the wetting rate of the droplet is faster when a large gradient is present. This new technology can be applied in cutting tools with their rake face subject to reduced wear and to improve the machining efficiency and accuracy.