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Author: search.filters.author.Danvirutai, ChanaipornSubject: search.filters.subject.Non-isothermal kinetics

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    Non-isothermal decomposition kinetics of synthetic serrabrancaite (MnPO4 · H2O) precursor in N2 atmosphere
    (2010-01-01)
    Boonchom, Banjong
    ;
    Danvirutai, Chanaiporn
    ;
    Thongkam, Montree
    The thermal decomposition of synthetic serrabrancaite (MnPO<inf>4</inf> · H<inf>2</inf>O) was studied in N<inf>2</inf> atmosphere using TG-DTG-DTA. Thermal analysis results indicate that the decomposition occurs in two stages, which are assigned to the dehydration and the reduction processes and the final product is Mn<inf>2</inf>P<inf>2</inf>O<inf>7</inf>. X-ray powder diffraction, FT-IR and FT-Raman techniques were used for identification of the solid decomposition product. The decomposition kinetics analysis of MnPO <inf>4</inf> · H<inf>2</inf>O was performed under non-isothermal condition through isoconversional methods of Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The dependences of activation energies on the extent of conversions are observed in the dehydration and the reduction reactions, which could be concluded the "multi-step" processes. © Akadémiai Kiadó, Budapest, Hungary 2009.
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    Kinetics and thermodynamics of thermal decomposition of synthetic AlPO 4•2H2O
    (2009-12-01)
    Boonchom, Banjong
    ;
    Danvirutai, Chanaiporn
    The non-isothermal kinetics of dehydration of AlPO<inf>4</inf>•2H <inf>2</inf>O was studied in dynamic air atmosphere by TG-DTG-DTA at different heating rates. The result implies an important theoretical support for preparing AlPO<inf>4</inf>. The AlPO<inf>4</inf>•2H<inf>2</inf>O decomposes in two step reactions occurring in the range of 80-150 °C. The activation energy of the second dehydration reaction of AlPO<inf>4</inf>•2H<inf>2</inf>O as calculated by Kissinger method was found to be 69.68 kJ mol<sup>-1</sup>, while the Avrami exponent value was 1.49. The results confirmed the elimination of water of crystallization, which related with the crystal growth mechanism. The thermodynamic functions (ΔH*, ΔG*and ΔS*) of the dehydration reaction are calculated by the activated complex theory. These values in the dehydration step showed that it is directly related to the introduction of heat and is non-spontaneous process. © 2009 Akadémiai Kiadó, Budapest, Hungary.
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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.
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    Soft solution synthesis, non-isothermal decomposition kinetics and characterization of manganese dihydrogen phosphate dihydrate Mn(H2PO4)2·2H2O and its thermal transformation products
    (2008-06-15)
    Boonchom, Banjong
    ;
    Danvirutai, Chanaiporn
    ;
    Maensiri, Santi
    Manganese dihydrogen phosphate dihydrate (Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O) was synthesized by a simple, rapid and cost-effective method using Mn(c) and H<inf>3</inf>PO<inf>4</inf> in water-acetone medium at ambient temperature. The thermal stability of the Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O was studied by means of the non-isothermal kinetic (Kissinger method). The specificity of thermal decomposition was characterized by identification of the bonds to be selectively activated due to energy absorption at vibrational level, which was assigned by comparison of the calculated wavenumbers with the observed wavenumbers in FTIR spectra. These results were used to identify the molecules or ions that were eliminated in each thermal transition step. The thermal transformation products from the synthesized Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O according to the thermal treatments at 243, 773 and 1073 K were obtained to be Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>, Mn<inf>2</inf>P<inf>4</inf>O<inf>12</inf> and Mn<inf>2</inf>P<inf>2</inf>O<inf>7</inf>, respectively. The synthesized Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and its thermal transformation products were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and FTIR spectroscopy. The SEM micrographs of the obtained products show the different morphologies, which are important for specific applications. © 2007 Elsevier B.V. All rights reserved.
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    A simple synthesis and thermal decomposition kinetics of MnHPO 4•H2O rod-like microparticles obtained by spontaneous precipitation route
    (2008-01-01)
    Boonchom, Banjong
    ;
    Danvirutai, Chanaiporn
    Manganese hydrogenphosphate monohydrate (MnHPO<inf>4</inf>•H <inf>2</inf>O) was prepared by a rapid precipitation (10 min) using Mn(c)-H <inf>3</inf>PO<inf>4</inf> system at ambient temperature. The thermal treatment of MnHPO<inf>4</inf>•H<inf>2</inf>O at 773 K found to be a manganese pyrophosphate (Mn<inf>2</inf>P<inf>2</inf>O<inf>7</inf>). The activation energies of the major mass loss step were calculated by Ozawa and Kissinger-Akahira-Sunose (KAS) isoconversional methods, which were used to determine the decomposition mechanism. The energy absorptions at the vibrational level of thermal decomposition steps were calculated and were compared with spectroscopic data, which were used to identify the molecules or ions that were released in each thermal transformation steps. The synthesized MnHPO <inf>4</inf>•H<inf>2</inf>O and its thermal decomposition product Mn <inf>2</inf>P<inf>2</inf>O<inf>7</inf> were investigated by scanning electron microscope (SEM), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The SEM micrographs show rod-like microparticles for the synthesized MnHPO<inf>4</inf>•H<inf>2</inf>O and porosity on surface of the decomposition product Mn<inf>2</inf>P<inf>2</inf>O<inf>7</inf>, which are important for specific applications.