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  • Küçük Resim
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    Alloying effect on K-shell fluorescence parameters of porous NiTi shape memory alloys
    (Elsevier Science Bv, 2014) Cengiz, E.; Ozkendir, O. M.; Kaya, M.; Tirasoglu, E.; Karahan, I. H.; Kimura, S.; Hajiri, T.
    The K-alpha,K-beta shell production cross-sections and K-beta/K-alpha intensity ratios of porous Ni -49 at% Ti shape memory alloys were determined using energy dispersive X-ray fluorescence (EDXRF) technique. Also, the alloying effect on the K shell fluorescence parameters was investigated. The samples were excited by 59.5 key gamma-rays from an Am-241 annular radioactive source. The K X-rays emitted by the samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 key. The structure analyses of the samples were also made using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The deviations between the present results and theoretical values, calculated for pure Ti and Ni, were attributed to charge transfer phenomena and/or rearrangement of valance shell electrons and porosity. (C) 2014 Elsevier B.V. All rights reserved.
  • Küçük Resim
    Öğe
    Traces of Defects in the Electronic Structure of Porous Ni-Ti Alloys
    (Journal Mater Sci Technol, 2013) Ozkendir, O. M.; Cengiz, E.; Tirasoglu, E.; Kaya, Mehmet; Karahan, I. H.; Orhan, N.
    The electronic structures of Ni-Ti shape-memory alloy samples were investigated by X-ray absorption fine structure (XAFS) spectroscopy both experimentally and theoretically. In the experimental section, the samples were measured at low temperature to determine the persistent traces of both preheating process and atomic concentration effects on the crystal and electronic structure by X-ray absorption near-edge structure (XANES) spectroscopy. As a second step, the extended-X-ray absorption fine structure (EXAFS) calculations, which are based on different choices of one electron potentials according to Ti coordinations by using the real space multiple scattering method FEFF 8.2 code, were performed. The crystallographic and electronic structures of the porous Ni-Ti alloys were tested at various temperatures ranging from 5 to 1323 K.