Analogy of thermogravimetric measurements

Dimensionless number has been developed and introduced for quantitative analysis of the effect of thermogravimetric measuring factors like sample quantity, heating rate, etc. The TG, DTG and T data of different thermogravimetric measurements can be used directly for calculation of the three constants of analogy. TG data of CaCO₃ measured in very different conditions show the method of transformation and its applicability for calculation of the correlation of measurements.     

Dehydration kinetics of ulexite from thermogravimetric data

In the present study, the kinetic parameters of the thermal decomposition of ulexite were investigated by using TGA data. For the kinetic analysis, the Suzuki and Coats-Redfern methods were applied. It was determined that the process fits a first-order kinetic model, and the value of the activation energies and frequency factors decreased with decreasing particle size, which can be attributed to the increasing particle internal resistance to the escape of water as the grain size increases. The activation energy values were found to be 47.34–60.01 kJ mol^–1 for region I and 0.225–1.796 kJ mol^–1 for region II for the range of particle size fraction used. The frequency factors were calculated to be 9821.8–524.9 s^–1 for region I and 3.05×10^–44–2.807×10^–5 for region II for the same conditions.     

不同次级结构的硫酸钡多晶体制备研究

以过氧化钡(Ba O2)晶体为母体钡源,利用溶液中碱性条件下过氧化氢电离控制Ba O2分解速度,结合过量SO42-制备了具有Ba O2宏观形貌的Ba SO4多晶体,该多晶体由条形结构单元组成。进一步通过不同聚合物添加剂调节次级结构单元的形貌,在溶液中引入聚苯乙烯磺酸钠制备了由球形次级结构单元组成的Ba SO4多晶体;而在不同浓度的聚丙烯酸添加剂作用下,可制得由纳米颗粒和纳米棒状结构单元组成的Ba SO4多晶体。制备的多晶体材料为具有母体材料统一宏观形貌的大颗粒,其次级结构可通过聚合物添加剂调控,为合成具有特定形貌的功能晶体材料提供了一个新的途径。     

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

由热重数据计算动力学参数

热重法(TG)是一种动态测量技术,可在程序升温或降温情况下对给定物质或体系提供一个连续的,以温度或时间为函数的重量变化曲线,所以由它跟踪反应能给出反应动力学的有关信息。这种非等温法与早期使用的等温法相比,有快速、连续和需要较少实验数据等优点,近年来在动力学研究方面得到广泛应用,但还只限于研究下列几种类型的简单     

Kinetic constants of polymeric materials from thermogravimetric data

The thermal decomposition of polytetrafluoroethylene (TFE, Teflon), high and low density polyethylene (HDP and LDP), Delrin Acetal (DA), AVCO Phenolic Fiberglass (APFG), and carbon phenolic (CP), were studied by a thermogravimetric technique which utilized a constant heating rate. Loss in sample weight was recorded as a function of time or temperature from room temperature to approximately 700°. Reaction orders were established from logarithmic rate versus temperature plots. Arrhenius frequency factors and overall activation energies were determined from computerized integrations of the appropriate rate equations in which the results were treated on the basis of first-order reaction mechanisms for specific temperature regions. Zero-order mechanisms were estimated by the usual graphical methods.

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Zusammenfassung Die thermische Zersetzung von Polytetrafluoräthylen (TFE, Teflon), von Polyäthylen niedriger und hoher Dichte (HDP und LDP), von Delrin Acetal (DA), von AVCO Phenolglaswolle (APFG) und von Phenolkohle (CP) wurde thermogravimetrisch mit konstanter Aufheizgeschwindigkeit untersucht. Der Gewichtsverlust wurde als Funktion der Zeit und der Temperatur von Zimmertemperatur bis zu 700° registriert. Aus der Darstellung der Logarithmen der Reaktionsgeschwindigkeit gegen die Temperatur wurde die Reaktionsordnung ermittelt. Die Arrheniusschen Frequenzfaktoren und die Werte der durchschnittlichen Aktivierungsenergien wurden durch komputerierte Integrierung der geeigneten Geschwindigkeitsgleichungen bestimmt. In den entsprechenden Geschwindigkeitsgleichungen wurden für spezielle Temperaturgebiete die Ergebnisse aufgrund des Reaktionsmechanismus von erster Ordnung behandelt. Reaktionen nullter Ordnung wurden nach den üblichen graphischen Methoden ausgewertet.

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Résumé Etude de la décomposition thermique du polytétrafluoroéthylène (Teflon), du polyethylene haute et basse densité, de l'acétal Delrin, de la fibre de verre phénolique AVCO et du carbone phénolique par TG à vitesse d'échauffement constante. Enregistrement de la perte de poids en fonction du temps ou de la température, depuis la température ambiante jusqu'à 700°C environ. Détermination de l'ordre des réactions en portant le logarithme de la vitesse en fonction de la température. Détermination des facteurs de fréquence et des énergies d'activation moyennes par intégration numérique des équations de vitesse appropriées en traitant les résultats sur la base de mécanismes réactionnels du 1er ordre dans les domaines de température correspondants. Emploi des méthodes graphiques habituelles dans le cas des réactions d'ordre zéro.

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(, ), c ( , ), (), () () c . ( , , 700°). . . . .

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The authors wish to acknowledge the many hours of valued assistance accomplished by Leonie Boehmer who performed all computational calculations reported herein and for the programming and compilation of data for the CDC 6061 computer. Acknowledgment is also extended to Mark Middleton who assisted with the technical measurements and calculations presented in this report.     

Kinetic analysis of thermogravimetric data

Four many curves methods, viz. calculation techniques based on Eqs (30), (31), (34) and (36), respectively, for deriving kinetic parameters from several TG curves recorded with different heating rates are tested on two sets of theoretical TG curves. The maximum reaction rate temperature and conversion, as well as the approximate formulae used for their calculation are discussed. Some aspects of the kinetic compensation effect are analysed. The final conclusion is that the use of the many curves methods is not reasonable.     

Kinetic analysis of thermogravimetric data

Fifteen thermogravimetric curves of the thermal decomposition of CaCO₃ reported in the literature have been analysed and kinetic parameters have been derived by means of Coats and Redfern's method. The activation energy varies between 26 and 377 kcal/mole, and the pre-exponential factors between 10² and 10⁶⁹, as functions of the working conditions. The kinetic compensation effect has been observed, and the results are well described by the following empirical compensation law: logZ=0.195E? 1.86.     

Kinetic analysis of thermogravimetric data

Thermal decomposition of 6 complexes of the type AH[Cr(NCS)₄ (am)₂]· nH₂O is studied with derivatograph. The formation of Cr(NCS)₃ as a labile intermediate is presumed. For some decomposition stages kinetic parameters are derived. The kinetic compensation effect is discussed.     

Kinetic analysis of thermogravimetric data

Nineteen salts of hexachloroplatinic acid with monovalent metals, aromatic and heterocyclic amines and phosphine were obtained and characterized by chemical analysis. The thermal decomposition of these complexes was studied by means of derivatograph and differential scanning calorimetry. The nature of the pyrolysis processes is discussed. From the TG curves, kinetic parameters were derived for different stages of the thermal decompositions.     

Kinetic analysis of thermogravimetric data

The potassium, ammonium and thirteen amine salts of hexabromoplatinic acid were obtained and characterized by chemical analysis. The thermal decompositions of these complex salts were studied by derivatograph and differential scanning calorimetry. The natures of the pyrolysis processes are discussed and compared with those obtained for the analogous chlorocomplexes. From the TG curves, kinetic parameters were derived for different stages of the thermal decomposition.

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Zusammenfassung Es wurden die Kalium-, Ammonium- und dreizehn verschiedene Aminsalze von Hexabromoplatinsäure hergestellt und mittels Elementaranalyse charakterisiert. Mittels Derivatographie und DSC wurde die thermische Zersetzung dieser Komplexsalze untersucht. Das Wesen der Pyrolysevorgänge wird besprochen und mit dem der analogen Chlorokomplexe verglichen. Anhand der TG-Kurven wurden für verschiedene Schritte der thermischen Zersetzung kinetische Parameter ermittelt.

     

Kinetic analysis of thermogravimetric data

Computer programs are given in Fortran language for three integral methods of deriving kinetic parameters from TG curves. Method 1 is a computerized variant of Doyle's curve-fitting method and performs the calculation of the exponential integralp(x) by means of author's empirical formula. Methods 2 and 3 are variants of the Coats-Redfern linearization method. Testing of the methods on both theoretical and experimental TG curves shows them to be almost equivalent as far as the results obtained are concerned, but Method 1 needs a ten-fold higher computer time.     

Kinetic analysis of thermogravimetric data

Journal of Thermal Analysis and Calorimetry - The thermal decomposition rates of seven [CoX 2(amine)2] type complexes (amine=aromatic amines) have been studied by thermogravimetry at 3 different...     

Electric and thermogravimetric properties of brownmillerites based on barium oxides

The electric and thermogravimetric properties of oxygen-deficient perovskite-like complex oxides Ba₂HoGaO₅, Ba₂YGaO₅, Ba₂ScInO₅, and Ba₂Sc₂O₅ are studied. It is found that these phases are capable of intercalating water from a gas phase; however, the total water amount is smaller than the supposed nominal concentration of oxygen vacancies calculated from formula A₂BB′O₅[V _O]₁. A comparison of the temperature dependences of conductivities suggests that the highest oxygen-ion conductivity is inherent in the phases with a statistical arrangement of oxygen vacancies (Ba₂Sc₂O₅, Ba₂ScInO₅). In a humid atmosphere (when the contribution of proton conductivity is significant), the total conductivity alters in line with the oxygen-ion conductivity, i.e. it increases in the series Ba₂YGaO₅-Ba₂HoGaO₅-Ba₂ScInO₅-Ba₂Sc₂O₅.     

Remarks on the determination of kinetic constants from thermogravimetric data

The methods for determining kinetic constants may have significant effects on the estimation results. The two-variable linear correlation method leads to values of the kinetic constants for which the difference between the calculated and measured values is comparable to or greater than the measurement precision. The non-linear method for calculating kinetic constants by searching for the minimum of the error function \(S1 = \sum\limits_{i = 1}^N {(m_{it} - m_i )^2 /N}\) , wherem _i andm _i are the measured and calculated values, respectively, andN is the number of experimental data, gives very precise results. A simple calculating technique is necessary for the fitting of the minimum point and the confidence region limit at the significance level. An appropriate calculation was made for metal oxidation according to the parabolic law.     

Kinetic analysis of thermogravimetric data XVI

The influence of the sample weight and the heating rate upon the thermal deamination of [Co(niox · H)₂(pyridine)₂]I(I), [Co(niox · H)₂(aniline)₂]I (II) and [Co(niox · H)₂ (pyridine)₂] NCS · 1.5 H₂O (III) and upon the dehydration of (III) has been studied (niox · H₂ stands for nioxime: 1,2-cyclohexanedione dioxime). Kinetic parametersn, E andZ have been derived by means of the authors' three computerized integral methods. Analysis of the results shows method 1 to be equivalent to method 2 with respect to the numerical values obtained, but it needs a tenfold computer time. Method 3 gives better results due to the better choice of input data. The influence of the working conditions and of the chemical constitution upon the kinetic parameters, as well as the kinetic compensation effect, are discussed.

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Zusammenfassung Der Einfluss des Probengewichts und der Aufheizgeschwindigkeit auf die thermische Desaminierung von [Co(niox · H)₂(pyridin)₂]I (I), [Co(niox · H)₂(anilin)₂]I (II) und [Co(niox · H)₂(pyridin)₂]NCS · 1.5 H₂O (III) sowie auf die Dehydratisierung von (III) wurde untersucht (niox · H₂ bedeutet Nioxim: 1,2-cyclohexandion-dioxim). Die kinetischen Parametern, E undZ wurden mit Hilfe der drei komputerisierten Integralmethoden der Autoren abgeleitet. Die Analyse der Ergebnisse zeigt, da\ Methode 1 der Methode 2 hinsichtlich der erhaltenen numerischen Werte ebenbürtig ist, doch eine zehnfache Rechenzeit beansprucht. Methode 3 ergibt bessere Resultate dank der besseren Wahl der eingegebenen Daten. Der Einfluss der Arbeutsbedingungen und der chemischen Struktur auf die kinetischen Parameter, sowie der kinetische Kompensationseffekt werden diskutiert.

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Résumé On a étudié l'influence du poids de l'échantillon et de la vitesse de chauffage sur la désamination thermique de [Co(niox · H)₂(pyridine)₂]I (I), [Co(niox · H)₂(aniline)₂]I (II) et [Co(niox · H)₂(pyridine)₂]NCS · 1.5 H₂O (III) ainsi que sur la déshydratation de (III) (niox · · H₂ représente la nioxime: 1,2-cyclohexanedione dioxime). A l'aide des trois méthodes d'intégration sur ordinateur des auteurs, les paramètres cinétiquesn, E et Z ont pu Être déduits. L'analyse des résultats montre que la méthode est équivalente à la méthode 2 quant aux valeurs numériques obtenues; elle exige cependant dix fois plus de temps d'ordinateur. La méthode 3 donne de meilleurs résultats en raison de la meilleure sélection des données d'entrée. On discute l'influence des conditions de travail et de la structure chimique sur les paramètres cinétiques ainsi que l'effet de compensation cinétique.

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[(. )₂ ( I (I), [(. )₂ ()₂] I (II) [Co(.)₂ ( NCS. 1.5 H₂O (III), ( .)₂ — : 1.2-. . , , , , E.Z. , 1 2 , . 3 , . , .

     

Errors of kinetic data obtained from thermogravimetric curves at increasing temperature

Errors of kinetic data obtained from thermogravimetric curves at increasing temperature are discussed.