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Showing papers in "Journal of Thermal Analysis and Calorimetry in 1975"


Journal ArticleDOI
TL;DR: In this paper, the methods of Freeman and Carroll (I), Coats and Redfern (II), Sharp and Wentworth (III), and the present author (IV) are applied to five theoretical thermoanalytical data calculated for assumed kinetic parameters at various heating rates.
Abstract: The methods of Freeman and Carroll (I), Coats and Redfern (II), Sharp and Wentworth (III) and the present author (IV) are applied to five theoretical thermoanalytical data calculated for assumed kinetic parameters at various heating rates. These are a first-order reaction, a second-order reaction, two cases of random scission in main chains of polymers, and a system of two parallel competitive first-order reactions. Although methods I, II and III cannot be applied to the latter three cases, when one does apply them to these cases, nearly straight relations are observed and false unreal kinetic parameters are obtained. For the two cases of random scission in the main chains of polymers, the author's method gives correct kinetic parameters. For the last case, the increase of the apparent activation energy with increasing conversion implies that even method IV cannot be applied. The reason for these results and methods for avoiding false unreal results are discussed.

180 citations


Journal ArticleDOI
TL;DR: In this article, a simple and satisfactorily accurate solution of the exponential integral in the nonisothermal kinetic equation for linear heating is proposed, and a small-intraction bound of 0.
Abstract: A simple and satisfactorily accurate solution of the exponential integral in the nonisothermal kinetic equation for linear heating is proposed: $$\mathop \smallint \limits_0^T e^{ - E/RT} dT = \frac{{RT^2 }}{{E + 2RT}}e^{ - E/RT} $$

139 citations


Journal ArticleDOI
TL;DR: The applicability of Satava's integral method for the kinetic description of nonisothermal heterogeneous processes is first discussed in this article, where the method is found insensitive as regards distinction between different types of nucleation growth models.
Abstract: The applicability of Satava's integral method for the kinetic description of nonisothermal heterogeneous processes is first discussed The method is found insensitive as regards distinction between different types of nucleation-growth models This disadvantage is countered by using additional criteria, such as the interval of straightline-fitting, the standard deviation and the value of the preexponential factor The algorithm for the necessary mathematical operations is explained A graphical printout in the form of a numerical plot available for any computer is described The program is tested on different processes It proves suitable for the preliminary classification of processes and for detection of changes in the reaction mechanism by separate analysis of three consecutive parts of the process

130 citations


Journal ArticleDOI
TL;DR: The applicability of the Arrhenius equation to a particular reaction could be tested by finding constancy or a predictable variation in the “frequency factor” with changes in experimental conditions or sample treatment or history.
Abstract: The “kinetic compensation effect” arises from deficiencies in the Arrhenius equation. Determination of the pre-exponential factor generally comprises only the reconciliation of the expression of the temperature dependence of the rate (the exponential term) with the observed rate. The applicability of the Arrhenius equation to a particular reaction could be tested by finding constancy or a predictable variation in the “frequency factor” with changes in experimental conditions or sample treatment or history.

125 citations


Journal ArticleDOI
TL;DR: In this article, the thermal decomposition of lithium, sodium, potassium, rubidium and caesium formates was investigated by a complex dynamic thermoanalytical method and the ratio of the products in reactions resulting in alkali metal carbonates and oxalates depended variously on the atmosphere used.
Abstract: The thermal decompositions of lithium, sodium, potassium, rubidium and caesium formates were investigated by a complex dynamic thermoanalytical method. The ratio of the products in reactions resulting in alkali metal carbonates and oxalates depended variously on the atmosphere used. Differences were found compared to isothermal investigations, in that the catalytic effects of bases could not be observed and the oxalate-conversion was lower. The formation of oxalate did not occur in the cases of lithium and caesium formates; the order for the other salts was sodium formate rubidium formate.

56 citations


Journal ArticleDOI
TL;DR: The exponential integral of the exponential integral can be approximated by means of the empirical formula, e.g. as mentioned in this paper, which approximates p(x) = - \int\limits_\infty ^x {\frac{{e^{ - u} }}{{u^2 }}} \cdot du\).
Abstract: The exponential integral\(p(x) = - \int\limits_\infty ^x {\frac{{e^{ - u} }}{{u^2 }}} \cdot du\) can be approximated by means of the empirical formula\(p(x) \approx \frac{{e^{ - x} }}{{(x - d)(x + 2)}}\) with\(d = \frac{{16}}{{(x^2 - 4x + 84)}}\). Ifx> 1.6, errors are less than 0.5%.

54 citations


Journal ArticleDOI
TL;DR: In this article, a study was made of the thermal decomposition of 22 derivatives of [M(en)3]X3 type complexes and the validity of a linear kinetic compensation law was observed.
Abstract: A study was made of the thermal decompositions of 22 derivatives of[M(en)3]X3 type complexes. Partial de-amination leading to the formation of[M(en)2X2]X type complexes occurs in the case ofM=Cr(III) ifX=Cl, Br, I orNCS, but in the case ofM=Co(III) it is possible only ifX=Cl. In other cases redox reactions hinder the formation of stable intermediates. Kinetic parameters were derived for the dehydration of 19 compounds.The validity of a linear kinetic compensation law was observed. The dependence of the kinetic compensation parameters on the nature of the thermal process is discussed.RésuméOn a étudié la décomposition thermique de 22 dérivés des complexes du type[M(en)3]x3. La réaction de désamination partielle qui amène la formation des complexes du type[M(en)2X2]X se produit dans le cas deCr(III), siX=Cl, Br, I ouCNS, mais dans le cas deCo(III) elle n'est possible que siX=Cl. Dans les autres cas, la formation d'intermédiaires stables est empêchée par des réactions d'oxydo-réduction. On a calculé les paramètres cinétiques pour la déshydratation de 19 composés.On a constaté la validité d'une loi de compensation cinétique linéaire. On discute la manière dont les paramètres de compensation cinétique dépendent de la nature du processus thermique.ZusammenfassungDie thermische Zersetzung von 22 Derivaten des Komplextyps[M(en)3]X3 wurde untersucht. Die partielle Deaminierungsreaktion, welche zur Bildung von Komplexen des Typs[M(en)2X2]X führt, tritt beiCr(III)-Komplexen in dem FalleX=Cl, Br, I oderNCS auf, ist aber beiCo(III)-Komplexen nur beiX=Cl möglich. In anderen Fällen wird die Bildung von stabilen Zwischenprodukten durch Redoxreaktionen verhindert. Für die Dehydratation von 19 Verbindungen wurden kinetische Parameter abgeleitet.Die Gültigkeit eines linearen kinetischen Kompensationsgesetzes wurde beobachtet. Die Abhängigkeit kinetischer Kompensationsparameter von der Beschaffenheit des thermischen Vorganges wird erörtert.РезюмеИсследован терморас пад 22 производных комплексов типа [М(ен)3] Х3. Реакция, приводящая к образов анию комплексов типа [М(ен)3] Х3X, имеетместо в случае Сr (III) комплексов, в которыхX=Cl, Br, I илиNCS, в случае же производныхСо (III) эта реакция возможна тол ько приX=Сl. В других сл учаях окислительно-восста новительные реакции мешают образ ованию стабильных пр омежуточных соединений. Рассчита ны кинетические параметры дегидрата ции 19 соединений.Обнаружена справедл ивость закона линейн ой кинетической компен сации. Обсуждается зависимость парамет ров кинетической ком пенсации от характера термическ ого процесса.

45 citations


Journal ArticleDOI
TL;DR: In this article, the oxidation in air and oxygen of iron (II) sulphide Fe1−xS was studied using TG, DTA, X-Ray powder photography and chemical analysis.
Abstract: The oxidation in air and oxygen of iron (II) sulphide Fe1−xS was studied using TG, DTA, X-Ray powder photography and chemical analysis A reaction sequence was deduced, in which in the temperature range 425–520‡ partial oxidation occurred forming FeSO4, FeS2, Fe3O4 Rapid oxidation to Fe2O3 was usually observed in the range 520–575‡ but under certain conditions this reaction did not occur In the temperature range 575–625‡ oxidation of FeSO4 to [Fe2(SO4)3]2 · Fe2O3 took place Decomposition of this material gave Fe2O3 as the final product at 725‡

42 citations


Journal ArticleDOI
TL;DR: In this paper, the main decomposition temperature ranges are: for CuL2, DTG 250-350°, DTA 300-320°, and for NiL2 for DTG 290-390°, differential thermal analysis (DTA) 360-400°.
Abstract: Thermogravimetric (TG), derivative thermogravimetric (DTG) and differential thermal analysis (DTA) curves of CuL2 and NiL2 (L−=diethyl dithiocarbamate anion) in air are studied. The main decomposition temperature ranges are: For CuL2, DTG 250–350°, DTA 300–320° and for NiL2, DTG 290–390°, DTA 360–400°. Mass loss considerations at the main decomposition stages indicate conversion of the complex to sulphides. Mathematical analysis of TG data shows that first order kinetics are applicable in both cases. Kinetic parameters (energy and entropy of activation and preexponential factor) are reported.

40 citations


Journal ArticleDOI
TL;DR: The quantities of products formed, and their first order kinetic parameters, are strongly dependent on the heating rate as discussed by the authors, which is the same as the rate of formation of total gases and the oxides of carbon.
Abstract: Cellulose has been pyrolysed in nitrogen at two heating rates, and the rates of formation of total gases, and the oxides of carbon, have been measured. The quantities of products formed, and their first order kinetic parameters, are strongly dependent on the heating rate.

40 citations


Journal ArticleDOI
TL;DR: Vanadate formation during reactions of V2O5 with CoO, NiO, ZnO, MgO, and MnO has been studied in this paper, where the initial products of solid-solid reaction with Zn2V2O7, mg3V4O13 and MnV2E6 respectively.
Abstract: Vanadate formation during reactions of V2O5 with CoO, NiO, ZnO, MgO and MnO has been studied. The initial products of solid-solid reaction with ZnO, MgO and MnO are Zn2V2O7, Mg3V4O13 and MnV2O6 respectively. CoO and NiO predominantly form the vanadate which corresponds to the stoichiometry of the initial oxide mixture. Subsequent formation of ortho-, pyro- and metavanadates as intermediates indicate that the principal mechanistic process is the transport of V2O5 to the reaction interface.

Journal ArticleDOI
TL;DR: In this article, the thermal decomposition of MgNH4PO4·H2O, MnNH 4PO4 · H2O and CoNH 4 PO4 · · H 2O was investigated under conventional and under quasiisothermal-quasi-isobaric conditions.
Abstract: The thermal decomposition of MgNH4PO4·H2O, MnNH4PO4 · H2O, CoNH4PO4 · · H2O and CdNH4PO4·H2O were investigated under conventional and under quasiisothermal-quasi-isobaric conditions. The experiments were carried out with a Derivatograph suitable for performing simultaneous TG and EGA examinations. It was found that the thermal decompositions of the four compounds each consist of two partial processes: the departure of the water of crystallization, and the subsequent inseparable escape of the ammonia and constitution water. Depending on the experimental conditions, the two processes more or less overlap. The relatively best separation of the two processes can be attained by using quasi-isothermal and quasi-isobaric conditions.

Journal ArticleDOI
TL;DR: The explosive sensitivity of methylammonium perchlorates has been investigated by differential thermal analysis, thermogravimetric analysis, mass spectrometry and explosion delay experiments as mentioned in this paper.
Abstract: The explosive sensitivity of methylammonium perchlorates has been investigated by differential thermal analysis, thermogravimetric analysis, mass spectrometry and explosion delay experiments. The decomposition temperature of these compounds increases in the order CH3NH3ClO4>(CH3)2NH2ClO4>(CH3)3NHClO4. The activation energy shows the reverse order, indicating thereby that the stability increases with increasing substitution. Mass spectrometric investigation, however, suggests an increasing reactivity with increasing substitution. A possible explanation for such behaviour is proposed. It appears that explosion delay is correlated with thermal decomposition and impact sensitivity.

Journal ArticleDOI
W. Ludwig1
TL;DR: In this article, the special position occupied by glasses amongst solids is again underlined by their thermal behaviour. But the authors used As2Se3 as model glass and found that the range of transformation characteristic of glass is less sharply defined than the freezing point.
Abstract: The special position occupied by glasses amongst solids is again underlined by their thermal behaviour. This feature was studied using As2Se3 as model glass. The range of transformation characteristic of glass is less sharply defined than the freezing point. In the thermal characterization of glass the former is highly dependent on the rate of heating and the thermal history of the glass. The recrystallization and melting temperatures are subject to corresponding modifications.

Journal ArticleDOI
TL;DR: In this article, the authors measured the thermal expansion coefficients on ultraoriented polyethylene fibers with a solid-state extrusion in an Instron Capillary Rheometer at 136°, 2100 atm.
Abstract: Thermal expansion coefficients have been measured on ultraoriented polyethylene fibers. Samples were prepared by a solid-state (crystalline) extrusion in an Instron Capillary Rheometer at 136°, 2100 atm. and at a draw ratio of 50. The expansion coefficients between −150 and +50°, perpendicular to the fiber axis, were positive and of the order of 10−4 °C−1. Conversely, parallel to that direction, the observed values were both negative and small, of the order −10−6 °C−1. Length changes were reversible and reproducible between −150 and < +50°. Negative coefficients were attributed to the presence of highly-extended and fully-aligned chains along the fiber. Valuable information about chain conformation, dynamics and lattice perfection can be obtained for the ultraoriented morphologies simply by measuring the linear thermal expansion.

Journal ArticleDOI
TL;DR: For a series of similar-type chemical transformations in non-isothermal kinetics, identical or closely similar values of T�Ω(T�ℓ№) are observed in the equation.
Abstract: If, for a series of similar-type chemical transformations in non-isothermal kinetics, identical or closely similar values of T cr are observed in the equation 1/T cr =1/T si + + (R/E i)·ln (E i q/RT si 2 the existence of the compensation relationship lnA i= =E i/RT cr may regularly be assumed.

Journal ArticleDOI
TL;DR: In this article, the Derivatograph has been found to be suitable for the investigation of biopolymers consisting of polysaccharides and proteins, and it has been demonstrated that interactions between the macromolecules of the collagen-proteoglycan-glycoprotein complexes significantly influence the thermal stability of the individual components.
Abstract: The Derivatograph has been found to be suitable for the investigation of biopolymers. consisting of polysaccharides and proteins. It could be demonstrated that interactions between the macromolecules of the collagen-proteoglycan-glycoprotein complexes significantly influence the thermal stability of the individual components.

Journal ArticleDOI
TL;DR: In this article, the thermal decomposition of methylammonium perchlorate (MAP) has been studied under isothermal and non-isothermal conditions and the results have been explained on the basis of a methyl group transfer in addition to proton transfer in the decomposition process.
Abstract: The thermal decomposition of methylammonium perchlorate (MAP) has been studied under isothermal and non-isothermal conditions. Differential thermal analysis of MAP showed, in addition to the exotherm due to decomposition, another exotherm at 408° which was observed for the first time. Chemical analysis and the infrared spectrum of the residue left behind after the decomposition proved it to contain NH4ClO4. The results have been explained on the basis of a methyl group transfer in addition to proton transfer in the decomposition process.

Journal ArticleDOI
TL;DR: The thermal behavior of a series of flame-resistant materials was studied using the combined techniques of Differential Scanning Calorimetry and thermogravimetry in this paper, where materials were separated into three main groups according to the manner in which their flame resistance was achieved.
Abstract: The thermal behaviour of a series of flame-resistant materials was studied, using the combined techniques of Differential Scanning Calorimetry and thermogravimetry. Materials were separated into three main groups according to the manner in which their flame resistance is achieved. The groups studied were (i) cellulosic materials which have been rendered flame-resistant by additives. (ii) chlorine-containing materials and (iii) high, temperature, resistant materials.

Journal ArticleDOI
TL;DR: In this paper, several maxima of the gas evolution rate are observed, when microgram quantities of Mg(OH)2 are heated under ultrahigh vacuum conditions, and when a critical thickness is reached, it spontaneously recrystallizes to cubic MgO.
Abstract: The thermal decomposition of finely divided Mg(OH)2 does not occur smoothly. Several maxima of the gas evolution rate are observed, when microgram quantities of Mg(OH)2 are heated under ultrahigh vacuum conditions. This phenomenon is attributed to the formation of an overlayer of partially decomposed hydroxide Mg(OH)2−x Ox,2 □x,2 with x → 2 (□: anion-sized neutral vacancy left by H2O molecules in the hydroxide lattice). This defect layer represents a diffusion barrier for further H2O molecules. When a critical thickness is reached, it spontaneously recrystallizes to cubic MgO exposing fresh Mg(OH)2 surface.

Journal ArticleDOI
TL;DR: In this paper, the free energy of formation was calculated by the analyses due to Wagner and Jordan using this heat of fusion and liquidus data, and the experimentally determined value of the heat of formation and the calculated free energy was combined to obtain the entropy of formation.
Abstract: The heats of formation and fusion of SnTe were determined in a differential thermal analysis calorimeter. Its free energy of formation was calculated by the analyses due to Wagner and Jordan using this heat of fusion and liquidus data. The experimentally determined value of the heat of formation and the calculated free energy of formation were combined to obtain the entropy of formation. The thermodynamic properties were interpreted in terms of the structure and bonding of the compound.

Journal ArticleDOI
TL;DR: In this paper, the dependence of the thermal stability of polyimides on the structure of their diamine component was established and it was shown that the effect of thermal stability progressively weakens with the increase in the rigidity of their chemical structure.
Abstract: Thermogravimetry of polyimides based on dianhydrides of pyromellitic, diphenyl- and diphenyloxidetetracarboxylic acids and a series of diamines has been used to determine their temperature characteristics and calculate their activation energies. The dependence of the thermal stability of the polyimides on the structure of their diamine component was established. It was shown that the effect of the thermal stability of the polyimides progressively weakens with the increase in the rigidity of their chemical structure.


Journal ArticleDOI
TL;DR: In this article, eine einfache correlation zwischen der Zersetzungstemperatur und der Lage des Liganden L in der spektrochemischen Reihe konnte gefunden werden.
Abstract: Das thermische Verhalten einer Anzahl komplexer Verbindungen des Typs [FeII(CN)5L]5− wurde mittels thermogravimetrischer und Differential-Thermoanalyse untersucht. Eine einfache Korrelation zwischen der Zersetzungstemperatur und der Lage des Liganden L in der spektrochemischen Reihe konnte gefunden werden. Die aus dem Studium der festen Zersetzungsprodukte erhaltenen experimentellen Beweise gestatten es, einige Zersetzungsschemata aufzustellen.

Journal ArticleDOI
TL;DR: In this paper, the authors define six lois de diffusion and show that trois d'entre elles sont valides, car elles tiennent compte de tous les parametres, whereas les phenomenes qui se manifestent tres souvent a la fin des reactions de decomposition ne peuvent pas etre representatifs de ce qui se produit reellement dans le solide.
Abstract: De nombreux chercheurs font etat de lois cinetiques pour l'etude par thermoanalyse, de reactions heterogenes, essentiellement les reactions de decompositions thermiques. Les auteurs font une analyse theorique de six lois de diffusion et montrent que seulement trois d'entre elles sont valides, car elles tiennent compte de tous les parametres. Ils discutent ensuite de la definition a donner au terme “diffusion” et montrent que les phenomenes qui se manifestent tres souvent a la fin des reactions de decomposition ne peuvent pas etre representatifs de ce qui se produit reellement dans le solide.

Journal ArticleDOI
TL;DR: In this paper, the thermal degradation of polyvinyl acetate was investigated under dynamic atmosphere of helium up to 400° with a thermobalance, and the volatile products were analyzed by a gas chromatograph.
Abstract: The thermal degradation of poly(vinyl acetate) was investigated under dynamic atmosphere of helium up to 400° with a thermobalance. The volatile products were analyzed by a gas chromatograph.

Journal ArticleDOI
TL;DR: In this article, thermische Zersetzung des MgCl2·6H2O thermoanalytisch and massenspektrometrisch unter normalbedingungen analysiert.
Abstract: Unter dynamischen Bedingungen wurde die thermische Zersetzung des MgCl2·6H2O thermoanalytisch und massenspektrometrisch unter Normalbedingungen analysiert. Es wurde besonders der Einflus der Aufheizgeschwindigkeit und des Probengewichtes auf die Entwasserung und die Hydrolyse untersucht. Es ergab sich, das der Entwasserungsvorgang in relativ weiten Grenzen durch die Analysenbedingungen beeinflust werden kann. Die Kinetik des Hydrolyseprozesses wird demgegenuber durch die ablaufenden chemischen Reaktionen in relativ weiten Grenzen unabhangig von den auseren Bedingungen bestimmt.

Journal ArticleDOI
TL;DR: In this paper, a number of X-ray diffraction studies of antimony(III) oxide, (Sb2O3), in air, nitrogen and argon atmospheres have been made.
Abstract: Thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction studies of antimony(III) oxide, (Sb2O3), in air, nitrogen and argon atmospheres have been made.

Journal ArticleDOI
TL;DR: In this article, the kinetics and thermodynamics of the thermal decomposition of ammonium metavanadate (AMV) are combined with the structural information available for AMV, for the important decomposition intermediate, ammonium hexavanadates (AHV), and for vanadium pentoxide, the product of the decomposition in non-reducing atmospheres, to enable the atomic movements involved in the course of decomposition to be discussed in detail.
Abstract: The kinetics and thermodynamics of the thermal decomposition of ammonium metavanadate (AMV) are combined with the structural information available for AMV, for the important decomposition intermediate, ammonium hexavanadate (AHV), and for vanadium pentoxide, the product of the decomposition in non-reducing atmospheres, to enable the atomic movements involved in the course of decomposition to be discussed in detail.

Journal ArticleDOI
TL;DR: In this paper, the enthalpies of fusion and prefusion of some organic acids were measured using a combination of both the saliency and the temperature of the mixture. But they were only applied to two types of molecules.
Abstract: Calorimetric and cryometric methods are employed to measure the enthalpies of fusion and prefusion of some organic acids.