Effect of water on the surface oxidation of an Al-Pd-Mn quasicrystal

X-ray photoelectron spectroscopy is used to determine the effect of water on the oxidation of a quasicrystalline alloy at room temperature. We use a single-grain sample, oriented with the fivefold axis perpendicular to the surface plane, and with nominal bulk composition Al70Pd21Mn9. We compare the oxide which forms upon exposure to four basic environments: pure oxygen in ultrahigh vacuum, ambient air, humid air and liquid water. These environments are increasingly aggressive toward the alloy, as judged by the number of alloy constituents oxidized and by the thickness of the oxide layer.