Thermal decomposition kinetics of potassium iodate

The thermal decomposition of potassium iodate (KIO₃) has been studied by both non-isothermal and isothermal thermogravimetry (TG). The non-isothermal simultaneous TG–differential thermal analysis (DTA) of the thermal decomposition of KIO₃ was carried out in nitrogen atmosphere at different heating rates. The isothermal decomposition of KIO₃ was studied using TG at different temperatures in the range 790–805 K in nitrogen atmosphere. The theoretical and experimental mass loss data are in good agreement for the thermal decomposition of KIO₃. The non-isothermal decomposition of KIO₃ was subjected to kinetic analyses by model-free approach, which is based on the isoconversional principle. The isothermal decomposition of KIO₃ was subjected to both conventional (model fitting) and model-free (isoconversional) methods. It has been observed that the activation energy values obtained from all these methods agree well. Isothermal model fitting analysis shows that the thermal decomposition kinetics of KIO₃ can be best described by the contracting cube equation.     

Thermal decomposition kinetics of potassium iodate

The effect of gamma ray irradiation on the rate and kinetics of thermal decomposition of potassium iodate (KIO₃) has been studied by thermogravimetry (TG) under non-isothermal conditions at different heating rates (3, 5, 7, and 10 K min^?1). The thermal decomposition data were analyzed using isoconversional methods of Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Friedman. Irradiation with gamma rays increases the rate of the decomposition and is dependent on the irradiation dose. The activation energy decreases on irradiation. The enhancement of the rate of the thermal decomposition of KIO₃ upon irradiation is due to the combined effect of the production of displacements and extended lattice defects and chemical damage in KIO₃. Non-isothermal model fitting method of analysis showed that the thermal decomposition of irradiated KIO₃ is best described by the contracting sphere model equation, with an activation energy value of ~340 kJ mol^?1.     

Thermal decomposition of potassium octahydridotriborate

Conclusions The thermal decomposition of KB₃H₈ in vacuum at 150 forms 9-pentaborane and potassium hydridoborate followed by partial reaction between the latter to form K₂B₁₂H₁₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1629–1632, July, 1984.     

Thermal decomposition and non-isothermal decomposition kinetics of carbamazepine

The thermal stability and kinetics of isothermal decomposition of carbamazepine were studied under isothermal conditions by thermogravimetry (TGA) and differential scanning calorimetry (DSC) at three heating rates. Particularly, transformation of crystal forms occurs at 153.75°C. The activation energy of this thermal decomposition process was calculated from the analysis of TG curves by Flynn-Wall-Ozawa, Doyle, distributed activation energy model, ?atava-?esták and Kissinger methods. There were two different stages of thermal decomposition process. For the first stage, E and logA [s^?1] were determined to be 42.51 kJ mol^?1 and 3.45, respectively. In the second stage, E and logA [s^?1] were 47.75 kJ mol^?1 and 3.80. The mechanism of thermal decomposition was Avrami-Erofeev (the reaction order, n = 1/3), with integral form G(α) = [?ln(1 ? α)]^1/3 (α = ～0.1–0.8) in the first stage and Avrami-Erofeev (the reaction order, n = 1) with integral form G(α) = ?ln(1 ? α) (α = ～0.9–0.99) in the second stage. Moreover, ΔH ^≠, ΔS ^≠, ΔG ^≠ values were 37.84 kJ mol^?1, ?192.41 J mol^?1 K^?1, 146.32 kJ mol^?1 and 42.68 kJ mol^?1, ?186.41 J mol^?1 K^?1, 156.26 kJ mol^?1 for the first and second stage, respectively.     

Thermal behavior and decomposition kinetics

The thermal behaviors of [1,1,1-trifluro-3-(2-thenoyl)-acetonato]copper(II) Cu(TTA)₂ and its adducts with pyridine Cu(TTA)₂(Py)₂, 2,2'-bipyridine Cu(TTA)₂(Bpy), quinoline Cu(TTA)₂(Ql)₂, and dimethyl sulfoxide Cu(TTA)₂(DMS) in a nitrogen atmosphere were studied under the non-isothermal conditions by simultaneous TG-DTG-DSC technique. The results showed that the evolution of the solvent molecules generally proceeded before the release of TTA in different ways according to their structures. The Cu(TTA)₂(Bpy) exhibited a unique decomposition pattern due to its distinctive structure. The dependences of activation energy on extent of reaction for all the stage of each compound were determined by using an isoconversional method, Flynn-Wall-Ozawa equation, which show E values varied with reaction progress, indicating the complexity of these decomposition reactions. In addition, the values of activation energy E for TTA molecules evolution are generally higher than that for the solvent molecules release. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition kinetics of sodium metaperiodate

Aged and fresh samples of sodium metaperiodate are subjected to thermal decomposition studies in air by TG, DTG and DTA techniques. The kinetic parameters for their decomposition have been evaluated by weighted least squares method using equations of Coats-Redfern, Horowitz-Metzger and Freeman-Carroll. The results indicate that, within the limits of experimental error, ageing did not change the E^* values considerably.

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过氧化二异丙苯的热分解动力学研究

过氧化二异丙苯(DCP)是一种有广泛用途的过氧化物交联剂,具有高的交联效率和优良的交联性能.其分解温度较低,热分解速度较快,即使没有外界能量的作用,在自然储存的条件下也会发生化学反应,放出热量[1,2].     

Thermal decomposition kinetics of strontium oxalate

The thermal decomposition behavior in air of SrC₂O₄ · 1.25H₂O was studied up to the formation of SrO using DTA-TG-DTG techniques. The decomposition proceeds through four well-defined steps. The first two steps are attributed to the dehydration of the salt, while the third and fourth ones are assigned to the decomposition of the anhydrous strontium oxalate into SrCO₃ and the decomposition of SrCO₃ to SrO, respectively. The exothermic DTA peak found at around 300°C is ascribed to the recrystallization of the anhydrous strontium oxalate. On the other hand, the endothermic DTA peak observed at 910°C can be attributed to the transition of orthorhombic-hexagonal phase of SrCO₃. The kinetics of the thermal decomposition of anhydrous strontium oxalate and strontium carbonate, which are formed as stable intermediates, have been studied using non-isothermal TG technique. Analysis of kinetic data was carried out assuming various solid-state reaction models and applying three different computational methods. The data analysis according to the composite method showed that the anhydrous oxalate decomposition is best described by the two-dimensional diffusion-controlled mechanism (D₂), while the decomposition of strontium carbonate is best fitted by means of the three-dimensional phase boundary-controlled mechanism (R₃). The values of activation parameters obtained using different methods were compared and discussed.     

Thermal decomposition kinetics of some aromatic azomonoethers

The non-isothermal kinetic parameters corresponding to the decomposition of 4-[(4-chlorobenzyl)oxy]-4’-nitro-azobenzene were evaluated. The kinetic analysis was performed by means of different multi-heating rates methods: isoconversional (‘model-free’) methods (Flynn–Wall–Ozawa) and invariant kinetic parameters method (IKP) associated with the criterion of the independence of activation parameters on the heating rate. The values of the obtained non-isothermal kinetic parameters are in satisfactory agreement.     

Thermal decomposition kinetics of some aromatic azomonoethers

Thermal analysis of 4-[(4-chlorobenzyl)oxy]-4′-chloro-azobenzene dye, exhibiting liquid crystalline properties, was performed in dynamic air atmosphere. The compound behavior was investigated using TG, DTG, DTA and DSC techniques, under non-isothermal linear regime. The evolved gases were analyzed by FTIR spectroscopy. Kinetic parameters of the first decomposition step were obtained by means of multi-heating rates methods, such as isoconversioanl methods, IKP method and Perez-Maqueda et al. criterion.     

Thermal decomposition kinetics of nickel fluorenone semicarbazone

Thermal decomposition of nickel fluorenone-semicarbazone has been studied by TG. Thermoanalytical data (TG and DTG) of the chelate are presented. Mass loss considerations at the main decomposition stages indicate conversion of the complex to oxide. Mathematical analysis of TG data shows that first order kinetics is applicable for the first stage and second order to the second stage. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.

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Thermal decomposition kinetics of some aromatic azomonoethers

Thermal analysis of three azomonoether dyes, exhibiting liquid-crystalline properties, was performed in dynamic air atmosphere. Thermal stability studies and the evaluation of the kinetic parameters of each physical or chemical transformations are essential for a full characterization, before attempting accurate thin films’ depositions of such materials used in non-linear optical applications. New synthesized dyes with general formula: where R is a nematogenic group: CN, CF₃ or a highly polarizable group: NO₂ were investigated using TG, DTG, DTA and DSC techniques, under non-isothermal regime. The evolved gases were analyzed by FTIR spectroscopy. The activation energies of the first decomposition step were evaluated for each compound, the obtained results revealing complex mechanisms.     

Thermal decomposition kinetics of aluminum sulfate hydrate

The kinetics of individual stages of thermal decomposition of Al₂(SO₄)₃·18H₂O were studied by TG method. It is found that Al₂(SO₄)₃·18H₂O decomposes to Al₂O₃ in four major stages, all of endothermic. Some of these major stages are formed by sub-stages. The first three major stages are dehydration reactions in which two, ten and six moles water are lost, respectively. The last major stage is sulfate decomposition. In this study the kinetic parameter values of these major and sub-stages were calculated by integral and differential methods. The alterations of activation energies with respect to the decomposition ratio and to the method were investigated.     

Thermal decomposition of potassium carbonatooxoperoxovanadate(V)

The thermal decomposition of K₃[V(CO₃)O(O₂)₂] was studied under isothermal, dynamic and quasi-isobaric-isothermal condition. A mixture of K₄V₂O₇ and K₂CO₃ was identified as the primary product of thermal decomposition. Under experimental conditions not allowing a continuous loss of volatile products, the reaction of K₄V₂O₇ with CO₂ gives KVO₃ and K₂CO₃.

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Zusammenfassung Unter isothermen, dynamischen und quasi-isobaren Bedingungen wurde die thermische Zersetzung von K₃[V(CO₃)O(O₂)₂] untersucht. Als Primärprodukt der thermischen Zersetzungsreaktion wurde ein Gemisch aus K₄V₂O₇ und K₂CO₃ festgestellt. Wird unter experimentellen Bedingungen das Entweichen flüchtiger Produkte verhindert, so gibt die Reaktion von K₄V₂O₇ mit CO₂ die Produkte KVO₃ und K₂CO₃.

     

3,4-二硝基吡唑热分解及非等温动力学

采用TG-DSC综合热分析的方法,对3,4-二硝基吡唑(DNP)的热分解和非等温动力学进行了研究。结果表明DNP的热分解分两阶段进行,并且在升温速率达到15K/min时才能明显区分。分别采用Archar微分法和Coats-Redfen积分法计算了DNP第一阶段热分解反应动力学参数:Ea=91.6kJ.mol-1,lnA=42.7s-1。最可能的DNP热分解机理为随机成核和随后生长机理,符合动力学机理函数Avrami-Erofeev方程,n=3。     

Thermal decomposition kinetics of solids from DDTA curves

It is shown that the activation energy for solid thermal decompositions which follow a first order kinetic equation can be determined in a very simple manner from a single derivative differential thermal analysis (DDTA) curve. The experimental results are in good agreement with those obtained by other workers.     

Thermal decomposition kinetics of magnesite from thermogravimetric data

Thermal decomposition kinetics of magnesite were investigated using non-isothermal TG-DSC technique at heating rate (β) of 15, 20, 25, 35, and 40 K min⁻¹. The method combined Friedman equation and Kissinger equation was applied to calculate the E and lgA values. A new multiple rate iso-temperature method was used to determine the magnesite thermal decomposition mechanism function, based on the assumption of a series of mechanism functions. The mechanism corresponding to this value of F(a), which with high correlation coefficient (r-squared value) of linear regression analysis and the slope was equal to −1.000, was selected. And the Malek method was also used to further study the magnesite decomposition kinetics. The research results showed that the decomposition of magnesite was controlled by three-dimension diffusion; mechanism function was the anti-Jander equation, the apparent activation energy (E), and the pre-exponential term (A) were 156.12 kJ mol⁻¹ and 10^5.61 s⁻¹, respectively. The kinetic equation was

Thermal decomposition of potassium cobalt hexacyanoferrate(II)

Potassium cobalt hexacyanoferrate(II), K₂CoFe(CN)₆ · 1.4H₂O, loses its water when heated up to 170°C, and the anhydrous compound begins to decompose above 230°C. The cyanide groups are evaporated off in the temperature range 230–350°C, and the solid products thus formed are K₂CO₃, Fe₂O₃, Co₃O₄ and CoFe₂O₄. In the range 550–900°C, the cobalt-containing compounds become CoO, and K₂CO₃ probably partly decomposes to K₂O, so that the product mixture at 900°C is K₂CO₃/K₂O, Fe₂O₃ and CoO. Above this temperature, K₂CO₃ decomposes to K₂O.     

Thermal decomposition of potassium hexanitronickelate(II) hydrate

The thermal decomposition of the complex K₄[Ni(NO₂)₆]·H₂O has been investigated over the temperature range 25-600 °C by a combination of infrared spectroscopy, powder X-ray diffraction, FAB-mass spectrometry and elemental analysis. The first stage of reaction is loss of water and isomerisation of one of the coordinated nitro groups to form the complex K₄[Ni(NO₂)₄(ONO)]·NO₂. At temperatures around 200 °C the remaining nitro groups within the complex isomerise to the chelating nitrite form and this process acts as a precursor to the loss of NO₂ gas at temperatures above 270 °C. The product, which is stable up to 600 °C, is the complex K₄[Ni(ONO)₄]·NO₂, where the nickel atom is formally in the +1 oxidation state.