Wettability control of BeO surfaces by alpha-irradiation-induced nuclear transmutation

Abstract

A simple method to control the wettability of BeO surfaces is developed on the base of alpha irradiation. In this research, BeO disks were irradiated with an alpha beam under conditions of ∼25MeV in alpha particle energy and ∼315nA/cm2 in beam current density. After the alpha irradiation, changes in morphology and chemical composition of BeO surfaces were analyzed using a field emission scanning electron microscopy and X-ray photoelectron spectroscopy. The wettability of pristine and alpha-irradiated BeO surfaces was analyzed by measuring water contact angles (CAs). The result of analysis indicated that C and F atoms were produced by the alpha irradiation. 12C atoms were mainly produced by (α, n) nuclear reaction when 9Be atoms collide with energetic alpha particles. On the other hand, 19F atoms were mostly created by (α, n) reaction and following β+ decay when 16O atoms collide with alpha particles. Moreover, CF2 functional groups, which provide hydrophobic property, were formed by the combination of produced C and F atoms. The amount of CF2 functional groups produced on the surface increased as the fluence increased while no significant change in the surface roughness was observed. Accordingly, the CA of alpha-irradiated BeO surfaces gradually increased as the fluence increased. In conclusion, the wettability of BeO surfaces could be easily and precisely controlled by the alpha irradiation, from hydrophilicity to hydrophobicity.