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Author: search.filters.author.Boonchom, BanjongSubject: search.filters.subject.Thermodynamic properties

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    A new synthesis of BaHPO4 precipitated by BaCO3-H4PO4-NaOH system at room temperature
    (2013-08-30)
    Boonchom, Banjong
    ;
    Ruttanapun, Chesta
    ;
    Thongkam, Montree
    ;
    Chaiyasith, Pachernchaipat
    ;
    Woramongkonchai, Somsak
    Barium hydrogenphosphate, BaHPO<inf>4</inf> was synthesized for the first time through simple and rapid method using BaCO<inf>3</inf>-H<inf>3</inf>PO<inf>4</inf>-NaOH, pH =9.0 at room temperature for 30 min. The studied BaHPO<inf>4</inf> decomposed in a single well-defined stage via deprotonated hydrogenphosphate reactions, revealed by TG/DTG and DSC techniques. The calculated wavenumbers based on DSC peak were comparable with FTIR results, which support the breaking bonds of P-OH (HPO<inf>4</inf><sup>2-</sup>) in the deprotonated hydrogenphosphate reactions. The thermodynamic functions (ΔH*, ΔG*, and ΔS*) for the deprotonated hydrogenphosphate reactions calculated from DSC data indicate that the deprotonated HPO<inf>4</inf><sup>2-</sup> reaction occur a lower-energy pathway and spontaneous process. The FTIR, XRD and SEM data of the studied BaHPO<inf>4</inf> and its decomposed product Ba<inf>4</inf>P<inf>2</inf>O<inf>7</inf> are also reported. © (2013) Trans Tech Publications, Switzerland.
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    Study on thermal transformation of CuHPO4.H2O obtained by acetone-mediated synthesis at ambient temperature
    (2012-11-01)
    Baitahe, Rattanai
    ;
    Vittayakorn, Naratip
    ;
    Boonchom, Banjong
    Copper hydrogenphosphate monohydrate, Cu- HPO<inf>4</inf>.H<inf>2</inf>O, was synthesized for the first time through simple and rapid method using the mixing of copper carbonate and phosphoric acid in acetone medium at ambient temperature. The obtained CuHPO<inf>4</inf>.H<inf>2</inf>O decomposed in three stages via dehydration and deprotonated hydrogenphosphate reactions, revealed by TG/DTG and DSC techniques. The kinetic triplet parameters (E<inf>a</inf>, A, and n) and thermodynamic functions (δHz.ast;, δGz.ast;, and δS*) for the first two decomposed steps were calculated from DSC data. All the obtained functions indicate that the deprotonated HPO<inf>4</inf> <sup>2-</sup> reaction for the second step occurs at a higher energy pathway than the dehydration reaction for the first step. The calculated wavenumbers based on DSC peaks were comparable with FTIR results, which support the breaking bonds of OH (H<inf>2</inf>O) and P-OH (HPO<inf>4</inf> <sup>2-</sup>) according to decomposed mechanisms. All the calculated results are consistent and in good agreement with Cu- HPO<inf>4</inf>.H<inf>2</inf>O's thermal transformation mechanisms. © Akademiai Kiado, Budapest, Hungary 2012.
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    Thermodynamics and kinetics of the dehydration reaction of FePO4·2H2O
    (2010-05-01)
    Boonchom, Banjong
    ;
    Puttawong, Spote
    The thermal decomposition kinetics of FePO<inf>4</inf>·2H<inf>2</inf>O in dynamical air atmosphere was studied by mean TG-DTG-DTA. The stage and product of the thermal decomposition were determined. A number of kinetic models and calculation procedures were used to determine the kinetic triplet and thermodynamic parameters characterizing the dehydration process. The obtained activation energy and most kinetic model indicate the single kinetic mechanism and three-dimension diffusion as "Ginstling-Brounstein equation (D4 model)", respectively. The thermodynamic functions (ΔH*, ΔG* and ΔS*) of the dehydration reaction are calculated by the activated complex theory and indicate that the process is non-spontaneous without connecting with the introduction of heat. The kinetic and thermodynamic results were satisfactory which present good correlation with a linear correlation coefficient close to unit a low standard deviation. © 2010 Elsevier B.V. All rights reserved.