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Author: search.filters.author.Phoohinkong, WeerachonSubject: search.filters.subject.XANES

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    Nonlocal XANES pre-edge feature of FeTiO3 ilmenite-type at Ti and Fe K-edge
    (2020-09-01)
    Phoohinkong, Weerachon
    ;
    Boonyarattanakalin, Kanokthip
    ;
    Mekprasart, Wanichaya
    ;
    Pavasupree, Sorapong
    ;
    Pecharapa, Wisanu
    The pre-K-edge feature of Ti and Fe XANES of ilmenite FeTiO<inf>3</inf> were investigated. The electronic structure of FeTiO<inf>3</inf> was examined based on the partial density of electronic state distribution on both local and nonlocal atoms. A strong contribution of nonlocal metal-metal intervalence electronic states of Ti and Fe pre-K-edge was observed in X-ray absorption near-edge structure (XANES) measurement. This observation agrees well with the calculated local state density. The nonlocal excitation transitions in the pre-edge feature contribute to local pre-K-edge at both Ti and Fe. Ti pre-K-edge consists of highly hybridized Ti-3d(t<inf>2g</inf>) with a small part of dipole-allowed 4p and a small 4s density transition state feature which is predominated by nonlocal of Fe-3d mixed with 4p state delocalized via O-2p as the main component peak. The peak feature at Ti-3d(e<inf>g</inf>) energy state is assigned to hybridization of Ti-3d(e<inf>g</inf>) and Ti-4p state contributed with nonlocal of the hybridized Fe-sp and the Ti-pd state. Fe pre-K-edge shows two main prominent transition peaks of hybridized Fe-pd state and the delocalized local Fe-sp with nonlocal Ti-3d(t<inf>2g</inf>) and 4p mixing states centered at 7112.38 and 7116.48 eV, respectively. The local and nonlocal excited transition energy states and density of both Ti pre-K-edge and Fe pre-K-edge features are corresponded with each other through the O-2p state transition pathway.
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    ACTIVE-ILMENITE SURFACE STRUCTURE INFLUENCE ON ACID-ASSISTED BALL MILLING
    (2018-12-01)
    Phoohinkong, Weerachon
    ;
    Pavasupree, Sorapong
    ;
    Boonyarattanakalin, Kanokthip
    ;
    Mekprasart, Wanichaya
    ;
    Pecharapa, Wisanu
    Active-ilmenite powder derived from natural ilmenite sand was prepared by the ball milling process with acid-solution and Deionized (DI) water. Morphology and particle size of active-ilmenite product in acid/DI-assisted ball milling process were monitored by field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Surface atomic component and chemical bonding were investigated by X-ray photoelectron spectroscopy (XPS). Meanwhile, bulk chemical oxidation and fine structure of active-ilmenite were studied by X-ray absorption near edge structure (XANES) and extended X-ray absorption ne-structure spectroscopy (EXAFS) to confirm the oxidation state and local active species structure at surface. Active-ilmenite by acid-assisted ball milling process is a distinctive method for the preparation of active-ilmenite product with high active surface. Moreover, the distortion of TiO <inf>6</inf> and FeO <inf>6</inf> octahedral cluster on the sample surface was detected in all milled samples with acid-assisted ball milling process. The presence of Fe <sup>2+</sup> , Fe <sup>3+</sup> ions and miniature sulfate was also detected on the sample surface by milled product with acid-assisted method.
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    Structural, optical and magnetic properties of diluted magnetic perovskite ZnTiO3 doped with Co and Mn prepared by sonochemical method
    (2017-01-01)
    Wattanawikkam, Chakkaphan
    ;
    Phoohinkong, Weerachon
    ;
    Pecharapa, Wisanu
    We employed a sonochemical method to fabricate transition metal ion doped perovskite ZnTiO<inf>3</inf> (M-ZnTiO<inf>3</inf>) nanoparticles, including individual Co and Mn ions. The Zn:Ti was mixed in molar ratio of 1:1 to obtain starting precursor for ZnTiO<inf>3</inf>. The different concentrations of Co (5-10 mol%) and Mn (3-7 mol%) were doped in ZnTiO<inf>3</inf>, then the mixing solution were irradiated in high frequency ultrasound of a sonometer (20 kHz, 750 W) at room temperature to obtain the as-prepared samples. The final products were calcined at 800°C for 3 h to improve the crystallinity. We confirmed formation structures of M-ZnTiO<inf>3</inf> nanoparticles by X-ray diffraction (XRD), and used X-ray absorption near edge spectroscopy (XANES) and X-ray photoelectron spectroscopy (XPS) technique to investigate the crystal structure and valence states of the sample. Meanwhile, we studied their optical properties by diffuse reflectance spectroscopy, and evaluated magnetic properties of the samples at room temperature by vibrating sample magnetometer (VSM). Magnetization measurements revealed the paramagnetic behavior for Co-ZnTiO<inf>3</inf> and weak ferromagnetic behavior for Mn-ZnTiO<inf>3</inf>. We also investigated and discussed the effect of metal ion doping concentration on the structural, optical and magnetic properties.