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Author: search.filters.author.Mekprasart, WanichayaSubject: search.filters.subject.Calcination

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    Synthesis and characterization of cubic-like zinc stannate powders prepared by co-precipitation method
    (2016-01-01)
    Mekprasart, Wanichaya
    ;
    Tangcharoen, Thanit
    ;
    Nakhanivej, Puritat
    ;
    Pecharapa, Wisanu
    Spinel-type zinc stannate (Zn<inf>2</inf>SnO<inf>4</inf>) powders were synthesized by co-precipitation method using zinc chloride and tin chloride as the precursors for Zn and Sn sources, respectively. Co-precipitation process is one of effective techniques due to non-complex system, short process time, high yield, large scale production and cost-effectiveness comparing to other methods. The influence of calcination temperature in the range of 900 °C to 1100 °C on the structure, morphologies and cation distribution were studied using various characterization techniques. A single spinel structure phase formation after-calcined powders are confirmed by X-ray diffraction (XRD) results meanwhile scanning electron microscope (SEM) showed the appearance of cubic-like shape. The aggregation of particle and strong crystallinity was distinctly increased resulting to their greater size by the effect of high calcined temperature. Moreover, the non-equilibrium site occupancy of zinc (Zn<sup>2+</sup>) and tin (Sn<sup>4+</sup>) ions was investigated through Zn K-edge and Sn L3-edge investigated by X-ray absorption (XAS) spectra via the synchrotron radiation light source. Compared with the calcined temperature sample, XANES spectra revealed that the oxidation state of Zn was +2 and Sn valence was +4 in all spinel Zn<inf>2</inf>SnO<inf>4</inf> samples which well corresponds to the theoretical values.
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    Characterization and effect of calcination temperature on structural properties of spinel zinc aluminate synthesized via Co-precipitation process
    (2015-06-01)
    Mekprasart, Wanichaya
    ;
    Worasawat, Suchada
    ;
    Tangcharoen, Thanit
    ;
    Pecharapa, Wisanu
    Zinc aluminate (ZnAl<inf>2</inf>O<inf>4</inf>) nanopowders were synthesized by co-precipitation method using zinc chloride and aluminum chloride as starting precursors. The calcination temperature which was a crucial preparation factor was varied and its influence on relevant physical properties of the product was investigated. Structural properties of synthesized nanoparticles were investigated by X-ray diffraction, X-ray absorption spectroscopy, scanning electron microscope, and Raman spectroscopy. The results suggest that that ZnAl<inf>2</inf>O<inf>4</inf> in spinel structure with high crystallinity can be obtained after calcination beyond specific temperature affirmed by XRD results. Raman result indicates the correlated chemical bonding relating to the formation of ZnAl<inf>2</inf>O<inf>4</inf> structure. Meanwhile, the Zn K-edge X-ray absorption near-edge structure (XANES) spectra of these samples with different calcination temperature obtained from the synchrotron X-ray absorption spectroscopy measurement show the existence of accurate oxidation state for zinc ion (Zn<sup>2+</sup>) in the spinel crystal structure. Moreover, it is revealed that the calcination temperature has significant effect on the local environment of the zinc absorbing atoms through the interesting change of white line appearance.