Functional groups control of metal by electron beam irradiation and its application to superhydrophobic surface

Since electron beam irradiation tended to increase metal wettability, significantly decreasing surface wettability remained difficult. In this paper, low-energy electron beam irradiation was used to significantly decrease the surface wettability of 316 L stainless steel, and the mechanism of modifying functional groups was revealed. The experimental results demonstrated that the hydrophilic functional groups C-O-C, O-C=O, and -OH had a significant decrease in contents, and the hydrophobic C-C/C-H group contents increased dramatically. The contact angle increased from 50° to 91°. This was due to the interaction of excited secondary electrons with precursor molecules, as well as fragmented carbon radicals and other fragments adsorbed on the surface, which generated new chemical bonds. The effects of various metal materials and microtextures on secondary electron emission were investigated. It was observed that a higher excitation coefficient for secondary electrons corresponds to a greater increase in the contact angle. The addition of different types of precursor molecules has the effect of controlling the wettability of electron beam irradiation. Nitrogen reduced the effect of electron beam irradiation modification, and hydrocarbon molecules increased the effect. A superhydrophobic surface with a contact angle of 160° and a sliding angle of 6° was successfully prepared by combining a pitting texture with hydrocarbon molecules. It has excellent wear resistance, high temperature resistance, and ultraviolet radiation resistance.