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A simple synthesis and characterization of binary Co0.5Fe 0.5(H2PO4)2·2H2O and its final decomposition product CoFeP4O12
(2011-01-01)
Boonchom, Banjong
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Danvirutai, Chanaiporn
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Vittayakorn, Naratip
This paper reports the synthesis of binary Co<inf>0.5</inf>Fe <inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O by a simple, rapid and cost-effective method using CoCO<inf>3</inf>-Fe(c)-H <inf>3</inf>PO<inf>4</inf> system in water-acetone media at ambient temperature. Thermal transformation of the synthesized powder was investigated by TG/DTG/DTA and DSC techniques, which indicate that its final decomposed product was a binary cobalt iron cyclotetraphosphate CoFeP<inf>4</inf>O<inf>12</inf>. The FTIR and XRD results of the synthesized Co<inf>0.5</inf>Fe<inf>0.5</inf>(H <inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and the decomposed CoFeP<inf>4</inf>O<inf>12</inf> indicate the pure monoclinic phases with space group P2<inf>1</inf>/n and C2/c, respectively. The morphologies of Co<inf>0.5</inf>Fe<inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and CoFeP<inf>4</inf>O<inf>12</inf> powders appear non-uniform particle shapes and high agglomerates, which are different from the cases of the single compounds M(H<inf>2</inf>PO<inf>4</inf>) <inf>2</inf>·2H<inf>2</inf>O and M<inf>2</inf>P<inf>4</inf>O<inf>12</inf> (where M = Co, Fe). The magnetic properties of the studied compounds are superparamagnetic behaviors, which are important for specific applications. The physical properties of the studied powders are comparable with those reported in our previous study, affected by medium and condition of preparation method. © 2010 Elsevier Masson SAS. All rights reserved.
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Non-isothermal decomposition kinetics of synthetic serrabrancaite (MnPO4 · H2O) precursor in N2 atmosphere
(2010-01-01)
Boonchom, Banjong
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Danvirutai, Chanaiporn
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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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Rapid synthesis, kinetics and thermodynamics of binary Mn 0.5Ca0.5(H2PO4)2 • H2O
(2009-12-01)
Boonchom, Banjong
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Danvirutai, Chanaiporn
The binary manganese and calcium dihydrogen phosphate monohydrate Mn <inf>0.5</inf>Ca<inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf> • H<inf>2</inf>O was synthesized by a rapid and simple co-precipitation method using phosphoric acid, manganese metal, and calcium carbonate at ambient temperature. Thermal transformation shows complex processes and the final decomposed product was the binary manganese calcium cyclotetraphosphate MnCaP<inf>4</inf>O<inf>12</inf>. The activation energies of some decomposed steps were calculated by Kissinger method. Activated complex theory has been applied to each step of the reactions and the thermodynamic functions are calculated. These values for transformation stages showed that they are non-spontaneous processes without the introduction of heat. The differences of physical and chemical properties of the synthesized compound and its decomposed product are compared with M(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf> • H<inf>2</inf>O and M<inf>2</inf>P<inf>4</inf>O<inf>12</inf> (M = Mn and Ca), which indicate the effects of the presence of Ca ions in substitution of Mn ions and confirm the formation of solid solution. © 2009 Akadémiai Kiadó, Budapest, Hungary.
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Kinetics and thermodynamics of thermal decomposition of synthetic AlPO 4•2H2O
(2009-12-01)
Boonchom, Banjong
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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-1, 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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Study of the dehydration of Co(H2PO4) 2-2H2O
(2009-04-09)
Boonchom, Banjong
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Danvirutai, Chanaiporn
The thermal transformation of Co(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf> 2H<inf>2</inf>O was studied under a dry air atmosphere using TG-DTG-DTA. The TG-DTG-DTA curves show that the transformation occurs in three steps, which are dehydration processes. Co(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf> · 2H<inf>2</inf>O and its thermal transformation product were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), and UV-vis near-IR techniques. The nonisothermal kinetics of Co(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf> · 2H<inf>2</inf>O was studied by means of the Kissinger method. The specificity of the thermal transformation was characterized by identification of the bonds to be selectively activated because of energy absorption at the vibrational level, which are confirmed by the comparison of calculated wavenumbers and observed wavenumbers of the FTIR spectra. The activated complex theory has been applied to each step of the reactions, and the thermodynamic functions δH ≠, δG≠, and δS≠ are calculated. These values for three stages showed that they are connected with the introduction of heat and are nonspontaneous processes. © 2009 American Chemical Society.
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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
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Danvirutai, Chanaiporn
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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‡, ΔS‡, ΔG‡) 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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A simple synthesis and room temperature magnetic properties of new binary Mn0.5Fe0.5(H2PO4)2·xH2O obtained from a rapid co-precipitation at ambient temperature
(2009-02-01)
Boonchom, Banjong
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Maensiri, Santi
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Youngme, Sujittra
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Danvirutai, Chanaiporn
A new binary Mn<inf>0.5</inf>Fe<inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·xH<inf>2</inf>O powder was synthesized by simple and cost-effective method using phosphoric acid, manganese and iron metals as starting chemicals. The synthesized solid shows the complex thermal transformations and the final decomposition product is a new binary manganese iron cyclo-tetraphosphate, MnFeP<inf>4</inf>O<inf>12</inf>. The X-ray diffraction and FTIR results indicate that the synthesized new binary Mn<inf>0.5</inf>Fe<inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·xH<inf>2</inf>O and the decomposition MnFeP<inf>4</inf>O<inf>12</inf> powders are a pure monoclinic phase with space group P2<inf>1</inf>/n (Z = 2) and C2/c (Z = 4), respectively. The particle morphologies of Mn<inf>0.5</inf>Fe<inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·xH<inf>2</inf>O and MnFeP<inf>4</inf>O<inf>12</inf> powders appear as the rod-like tetragonal shape and show a high agglomeration of small particles, which are similar to the case of Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and Fe<inf>2</inf>P<inf>4</inf>O<inf>12</inf>, respectively. Room temperature magnetization results show a ferromagnetic behavior of the Mn<inf>0.5</inf>Fe<inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·xH<inf>2</inf>O and MnFeP<inf>4</inf>O<inf>12</inf> powders, having the hysteresis loops in the range of -10,000 Oe < H < +10,000 Oe with the specific magnetization values of 25.63 and 13.14 emu/g at 10 kOe, respectively. The lower magnetizations of Mn<inf>0.5</inf>Fe<inf>0.5</inf>(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·xH<inf>2</inf>O and MnFeP<inf>4</inf>O<inf>12</inf> than those of Fe(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and Fe<inf>2</inf>P<inf>4</inf>O<inf>12</inf> powders indicate the presence of Mn ions in substitution position of Fe ions. © 2008 Elsevier Masson SAS. All rights reserved.
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Synthesis, characterization and non-isothermal decomposition kinetics of manganese hypophosphite monohydrate
(2008-11-01)
Noisong, Pittayagorn
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Danvirutai, Chanaiporn
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Srithanratana, Tipaporn
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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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Simple synthesis, magnetic properties, and nonisothermal decomposition kinetics of Fe(H2PO4)2 · 2H2O
(2008-10-15)
Boonchom, Banjong
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Danvirutai, Chanaiporn
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Youngme, Sujittra
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Maensiri, Santi
Fe(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O was synthesized by a simple and cost-effective method using iron metal and phosphoric acid as starting chemicals. The thermal transformation products from the synthesized Fe(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf> · 2H <inf>2</inf>O according to the thermal treatment at 423 and 673 K were found to be FeH<inf>2</inf>P<inf>2</inf>O<inf>7</inf> and Fe<inf>2</inf>P <inf>4</inf>O<inf>12</inf>, respectively. The activation energies of decomposition reaction of Fe(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>· 2H<inf>2</inf>O were calculated through the isoconversional methods of Ozawa and Kissinger-Akahira-Sunose. The synthesized Fe(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, X-ray powder diffraction, and FTIR spectroscopy. Room-temperature magnetization results showed a ferromagnetic behavior of the Fe(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H <inf>2</inf>O and its thermal transformation products. The hysteresis loops were in the range -10000 Oe < H < + 10000 Oe, and the strong specific magnetization values were in the range 32.25-96.28 emu/g at 10 kOe. © 2008 American Chemical Society.
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Synthesis of MnNiP2O7 and nonisothermal decomposition kinetics of a new binary Mn0.5Ni0.5HPO4 · H2O precursor obtained from a rapid coprecipitation at ambient temperature
(2008-08-20)
Boonchom, Banjong
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Danvirutai, Chanaiporn
The new binary metal hydrogen phosphate monohydrate Mn<inf>05</inf>Ni <inf>0.5</inf>HPO<inf>4</inf> · H<inf>2</inf>O was synthesized by a rapid and simple coprecipitation method using phosphoric acid, manganese metal, and nickel carbonate at ambient temperature. The kinetics of dehydration of Mn <inf>05</inf>Ni<inf>0.5</inf>HPO<inf>4</inf> · H<inf>2</inf>O was studied under nonisothermal heating by thermogravimetry (TG), and its final decomposition product was a binary metal pyrophosphate, MnNiP<inf>2</inf>O <inf>7</inf>. The activation energies of the dehydration step of Mn <inf>05</inf>Ni<inf>0.5</inf>HPO<inf>4</inf>·H<inf>2</inf>O were calculated through the isoconversional methods of Ozawa and Kissinger-Akahira- Sunose (KAS), and the possible conversion functions have been estimated through the Coats-Redfern method. The activation energies calculated for the dehydration of Mn<inf>05</inf>Ni<inf>0.5</inf>HPO<inf>4</inf> · H<inf>2</inf>O by different methods and techniques were found to be consistent. The possible conversion function of the dehydration reaction for Mn<inf>05</inf>Ni <inf>0.5</inf>HPO<inf>4</inf> · H<inf>2</inf>O was "spherical symmetry" of a "three-dimensional diffusion mechanism". © 2008 American Chemical Society.

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