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    Electronic Structure Study of Ni-B Alloy Coatings by XAFS Technique
    (Springer, 2021) Özkendir, Osman Murat; Cengız, Erhan; Karahan, Ismail Hakki; Klysubun, Wantana
    The crystal and electronic structure properties of Ni-B (nickel-boron) alloy coatings produced by an electrodeposition method have been investigated. The crystal structures of the alloy coatings were determined by x-ray diffraction patterns and supported by extended x-ray absorption fine structure (EXAFS) spectroscopy. The local atomic structure around the Ni atom was obtained from EXAFS studies at the Ni K-edge, and the EXAFS data were fitted with theoretical calculations. With the addition of boron atoms in the nickel environment, NiB composite alloys were formed in the crystals with an orthorhombic "Cmcm" structure. The analysis revealed a limited effect of boron doping in the electronic structure of the nickel atoms. Boron atoms were determined as sitting between the Ni atoms and causing a disturbance in the crystal structure due to providing inhomogeneous interstitial potential and defects. © 2021, The Minerals, Metals & Materials Society.
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    K?-to-K? X-ray intensity ratio studies on changes of valance electron structures of nickel in Ni-B/hBN composite coatings
    (Pergamon-Elsevier Science Ltd, 2022) Cengiz, Erhan; Karahan, Ismail Hakki
    In this study, K beta/K alpha X-ray intensity ratio values of nickel in Ni coating and Ni-B/hBN (hBN: hexagonal Boron Nitride) composite coatings have been determined by the Energy Dispersive X-ray fluorescence spectroscopy (EDXRF) method. The K beta/K alpha X-ray intensity ratios of nickel in the Ni coating and Ni-B/hBN composite coatings have been compared with theoretical, experimental, and fitted data of the pure nickel. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) measurements have been performed to observe how hBN particles with different bath concentrations affected the crystal structure and microstructure, respectively. The valence electronic structure of Ni in the coatings has been determined by comparing the experimental K beta/K alpha X-ray intensity ratios with Multiconfiguration Dirac-Fock (MCDF) predictions for various electron structures of Ni. The results show that while the values of the K beta/K alpha X-ray intensity ratio of the Ni-B/hBN composite coatings over pure Ni coatings increases, the 3d electron populations decreases. The change in the valence electronic structure were interpreted through charge transfer and rearrangement processes.