Effects of boron on water dissociation and surface diffusivity of hydrogen on Ni3(Al,Ti)(110) single crystal surfaces

The interaction between water vapor (D2O) and boron-modified Ni3(Al,Ti)(110) was investigated using temperature-programmed desorption and X-ray photoelectron spectroscopy. Boron dosing was performed using a solid-state boron ion source. Results showed that boron reacts with water to form hydroxyls at temperatures as low as 130 K. D2 desorption occurs at ∼950 K from boron-modified Ni3(Al,Ti)(110), indicating strong B–D bonding. Surface diffusion coefficients of atomic D, obtained from dissociation of water, on clean and boron-modified Ni3(Al,Ti)(110) surfaces were measured at 270 K with electron-stimulated desorption. The surface diffusion coefficient of atomic D on 0.05 monolayer boron-modified surface is about 10 times smaller than that on the boron-free surface. This slower diffusion of atomic hydrogen may explain why boron improves the ductility of polycrystalline Ni3Al in moist environments.