HYDROGEN STORAGE IN FETI - SURFACE SEGREGATION AND ITS CATALYTIC EFFECT ON HYDROGENATION AND STRUCTURAL STUDIES BY MEANS OF NEUTRON-DIFFRACTION

Surface studies by means of AES and XPS show that during the activation process of FeTi titanium diffuses to the surface and metallic iron clusters are formed. They catalyze the hydrogen absorption and are the reason for the irreversible change of the magnetic properties of FeTi upon hydrogenation. At room temperature the surface segregation is not effective enough to restore the catalytic active surface so that FeTi is deactivated easily in air. Structural studies of FeTi, FeTiD and FeTiD1.74 were performed. The best agreement between observed and calculated intensities of FeTiD is obtained with space groups P2221 (Pmc21) and P2/c. The lattice parameters of the orthorhombic unit cell are a = 2.966 A ̊, b = 4.522 A ̊ and c = 4.370 A ̊. © 1979.