Preparation of broadband absorption ceramic coatings by using plasma electrolytic deposition

Two types of black ceramic coatings with high spectrum absorptivity were prepared on Al alloy substrate by using plasma electrolytic deposition method. The spectrum absorption properties of coatings were tested by using 355 nm ultraviolet laser pulses. Particle counter device was employed to collect and analyze the particles formed during the irradiation process. Experimental results showed that the coatings have porous structures. The sample coatings 1 and 2 have thickness of 120 μm and 60 μm with holes' diameter of about 70 μm and 15 μm, respectively. The coating 1 is mainly composed of Al₂O₃ and SiO₂ while coating 2 consists of Al₂O₃. The reflectivity of both coatings is much lower than that of Al alloy substrate. The absorptivity of samples 1 and 2 is about 99.88% and 99.92% for wavelength from 300 nm to 800 nm. The mechanisms of spectrum absorption were also explored.