Novel methods for the fabrication of ferromagnetic nickel and nickel boride thin films
Metal‐rich nickel boride thin films fabricated from boron‐containing precursor compounds by a cluster deposition process are shown to be ferromagnetic. The metal‐rich films fabricated by this approach exhibit hysteresis curves similar to those obtained for pure nickel foils. These films are a mixture of pure nickel and the Ni3B nickel boride phases. It is postulated that the hysteresis curves with smaller remnant magnetizations obtained from these films are a consequence of Ni3B inclusions within the films. Other novel organometallic source compounds for nickel chemical‐vapor deposition are briefly reviewed.
The adsorption of nickelocene: Part 2: decomposition and selective area deposition
Abstract We have studied the photofragmentation of nickelocene by photoemission and laser-induced photodesorption. The ultraviolet photolytic decomposition leads to relatively clean metal-to-ligand cleavage and photoinduced desorption of the cyclopentadienyl ligand fragments. This photolytic decomposition process is mechanistically different from the pyrolytic decomposition process, which results in the formation of C 3 H 3 and C 2 H 2 that desorbs both as free ligands and bound to nickel. The laser- and electron-induced fragmentation of nickelocene leads to the deposition of nickel containing features with considerable spatial resolution. Lines as fine as 10 nm across have been fabricated with electron beams. The photolytic decomposition of nickelocene can be used to fabricate micron-scale ferromagnetic nickel features in a wide variety of shapes and sizes.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME