Fabricating physicochemical microstructures with super hydrophilicity on Cf/SiC composites surface via picosecond-laser induced ablation

Abstract

Cf/SiC composites are advanced high-temperature materials for thermal protection and high-performance braking systems in the aerospace industry. Their surface wettability significantly affects the adhesion properties of the coatings. This study investigated the physical and chemical transformations of Cf/SiC composites during picosecond laser ablation and successfully fabricated micro-structured surfaces with super-hydrophilicity. The findings revealed that three-scale microstructures were formed on Cf/SiC composites after picosecond laser-ablating, which were orderly composed of regular convex plates (20–60 μm), agglomerate ablative products (1–5 μm), and nano particles (100–500 nm). The relative content of O on the laser-ablating surface was mostly>25%, both Si–O and Si–C bonds were found on the Si2p peak of the XPS spectrum. The primary content of the ablative products was crystalline and amorphous SiO2, resulting from the oxidation of the SiC matrix. The initial surface of the Cf/SiC composites was hydrophobic, and its contact angle was 92.7°. Conversely, the laser-ablating surfaces showed significant absorption of water droplets owing to the presence of the hydroxyl group in the amorphous SiO2, and the droplets quickly disappeared from the surface through the micro “tubular channels” caused by carbon fibers sublimating and oxidizing under the high laser temperature. Consequently, the superhydrophilic surfaces of the Cf/SiC composites were obtained via picosecond laser ablation, and the motion of the droplets was closely related to the laser power and scanning distance.