Initial oxidation of TiFe_1-xMn_x (x = 0-0.3) by low dose exposures to H₂O and O₂

The very initial room-temperature oxidation processes of the ternary pseudo-binary TiFe_1-xMn_x (x = 0-0.3) intermetallics by trace amounts of H₂O vapor and O₂ were studied utilizing XPS and AES techniques. Different reactivities of the two gases were obtained, with a lower oxidation ability of H₂O, relative to O₂, as anticipated from thermodynamic considerations. The exposure to O₂ results in a two stage oxidation of the Ti ingredient, which first converts into a divalent TiO (up to exposures of about 2 L), then proceeds into a tetravalent TiO₂ form. Unlike oxygen, water exposure produces only the divalent oxide through the whole exposure range studied (11 L). The Mn component in these compounds is oxidized only by O₂ and not by H₂O. The Fe ingredient is not oxidized at all and remains in its metallic form up to exposures of 30 L.