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Author: search.filters.author.Noisong, Pittayagorn

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    Thermodynamic and kinetic properties of the formation of Mn 2P2O7 by thermal decomposition of Mn(H 2PO2)2·H2O
    (2009-03-12)
    Noisong, Pittayagorn
    ;
    Danvirutai, Chanaiporn
    ;
    Boonchom, Banjong
    The kinetic properties in terms of activation energies and pre-exponential factors of two decomposition stages of Mn(H<inf>2</inf>PO<inf>2</inf>) <inf>2</inf>·H<inf>2</inf>O were calculated through the isoconversional method of Kissinger. The calculated results were further used to calculate some transition-state thermodynamic functions (ΔH<sup>‡</sup>, ΔS<sup>‡</sup>, ΔG<sup>‡</sup>) of the transition-state complex according to the transition-state complex theory of Erying. Kinetic and thermodynamic results are consistent with the indication that the two steps are nonspontaneous before the introduction of heat is involved. The Avrami constant, n, of the two decomposition steps was calculated and interpreted to be responsible for the mechanism of 1D growth decomposition, which is a nucleation controlled mechanism. Vibrational frequencies of breaking bonds in two stages were estimated and assigned by comparison with the observed FTIR spectra. The results exhibit a very close correlation between calculated and observed values. © 2009 American Chemical Society.
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    Synthesis, characterization and non-isothermal decomposition kinetics of manganese hypophosphite monohydrate
    (2008-11-01)
    Noisong, Pittayagorn
    ;
    Danvirutai, Chanaiporn
    ;
    Srithanratana, Tipaporn
    ;
    Boonchom, Banjong
    The manganese hypophosphite monohydrate (α-Mn(H<inf>2</inf>PO<inf>2</inf>)<inf>2</inf>·H<inf>2 </inf>O) was synthesized and characterized by differential thermal analysis-thermogravimetry (TG/DTG/DTA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The thermal transformation products form the synthesized Mn(H<inf>2</inf>PO<inf>2</inf>)<inf>2</inf>·H<inf>2</inf>O according to the thermal treatment at 160 and 450 °C were found to be α-Mn(H<inf>2</inf>PO<inf>2</inf>)<inf>2</inf>·xH<inf>2 </inf>O and Mn<inf>2</inf>P<inf>2</inf>O<inf>7</inf>, respectively. The activation energies of two decomposition reaction steps of Mn(H<inf>2</inf>PO<inf>2</inf>)<inf>2</inf>·H<inf>2</inf>O were calculated through the isoconversional methods of Ozawa and KAS. The obtained activation energies can be concluded that the reactions of the dehydration and the decomposition steps for Mn(H<inf>2</inf>PO<inf>2</inf>)<inf>2</inf>·H<inf>2</inf>O were the single and multi-step mechanisms, respectively. © 2008 Elsevier Masson SAS. All rights reserved.