Showing papers in "Journal of Thermal Analysis and Calorimetry in 1972"

Energy of activation for the decomposition of the alkaline-earth carbonates from thermogravimetric data

Abstract: Activation energies for the vacuum thermal decomposition of calcium, strontium and barium carbonates have been determined from thermogravimetric data, using the Coats and Redfern equation. A computer program, written in 4100 Algol, was used to process the data and to obtain the order (n) of the decomposition reactions. In all three cases, a value ofn=2/3 was in closest agreement with the experimental results, suggesting that decomposition occurs at a progressively shrinking spherical interface. The energies of activation obtained were in close agreement with the corresponding values of the enthalpy of decomposition, calculated at the temperature at which half of the sample had decomposed.

Heterogeneous reactions of solid nickel(II) complexes, III

Abstract: The stoichiometry of thermal decomposition was studied for the following compounds: Ni(pyNO)Cl2H2O (I), (pyNO=pyridine N-oxide), Ni(2-MepyNO)Cl2·2H2O (II), Ni(3-MepyNo)Cl2·2H2O (III) and Ni(4-MepyNO)2Cl2·C2H5OH (IV). The heating of the compounds led first to the release of H2O molecules (or C2H5OH molecules), with the formation of Ni(pyNO)Cl2 (V), Ni(2-MepyNO)Cl2(VI), Ni(3-MepyNO)Cl2 (VII) and Ni(4-MepyNO)2Cl2 (VIII). In the next stage, decomposition of the heterocyclic liugands set in. The compositions and spectral and magnetic properties of these complexes indicate their dimeric (II, III, IV, VIII) of polymeric (I, V, VI, VII) structure with coordinated molecules of H2O (or C2H5OH).

The interconversion of orthorhombic chromium oxy-hydroxide and chromium dioxide

Abstract: The thermal behaviour of CrOOH and CrO2 in different atmospheres has been studied by means of DTA, TG and X-ray diffraction. The easy interconversion between the two substances at one atmosphere pressure is explained on the basis of the results obtained.

Nomenclature in thermal analysis, Part IV

Abstract: The recommendations in the earlier reports of the Nomenclature Committee of the International Confederation for Thermal Analysis (ICTA)1–3 and its Sub-Committees4–7 have been well received and have been accepted by such international and national bodies as IUPAC8, ISO9, ASTM10 and AFNOR11. An integrated version of the second and third reports2,3 is currently being considered for adoption by IUPAC12. The unofficial and accurate translations that have appeared in several other languages3 are welcomed. A Working Group on Symbols has now been established under the Chairmanship of Dr.J. H. Sharp, U.K., and a Sub-Committee on nomenclature in the Chinese language, convened by Dr. D. T. Y. Chen, Hong Kong, has issued its firs publication.13. It has become evident since the first report1 was published that the definition of thermal analysis given therein is not entirely satisfactory; moreover, over the years several new techniques have emerged or minor techniques have assumed increasing importance. The Committee, having considered both these factors, presented the following report to the Fifth International Conference on Thermal Analysis, Kyoto, Japan, in August 1977, where it was accepted at the Business Session. Council of ICTA have therefore directed that it be published as a definitive document of ICTA with the request that the recommendations herein be adhered to in all publications in the English language.

DSC study of the kinetics of the thermal dehydration of BaCl2 · 2H2O and BaCl2 · H2O

Abstract: The kinetics of the thermal dehydration of various kinds of BaCl2 · 2H2O and of BaCl2 · H2O are investigated using a differential scanning calorimeter. The loss of H2O proceeds in two steps: BaCl2 · 2H2O→BaCl2 · H2O→BaCl2 and is therefore revealed by two endothermic peaks.

The preparation, characterization, and thermal behaviour of some lithium aluminum oxides: Li3AlO3 and Li5AlO4

Abstract: The purpose of this research was to study the best conditions for the synthesis of the double oxides Li5AlO4 and Li3AlO3 in the solid state starting from the simple oxides, and to determine their heats of formation

Thermal decomposition kinetics of sodium bicarbonate by differential thermal analysis

Abstract: The thermal decomposition of sodium bicarbonate has been studied by DTA. It has been shown that the application of the first order kinetic equation provides a convenient quantitative description of the DTA curves. The influence of particle size, dilution, rate of heating and the size of the sample holder has been examined.

The correlation between isothermal and non-isothermal kinetics in thermogravimetry

Abstract: It is shown that the total differential of the function of the amount of conversion versus temperature and time (α=f(T, t)) is equal to zero non-isothermal kinetics at constant heating rate. Hence, the mathematical expression used in the literature for the rate of the non-isothermal transformation,\(\frac{{d\alpha }}{{dt}} = \left( {\frac{{\partial \alpha }}{{\partial t}}} \right)_T + \left( {\frac{{\partial \alpha }}{{\partial T}}} \right)_t \cdot \frac{{dT}}{{dt}}\), is not valid.

Analysis of thermal processes: The exponential integral

Abstract: Thermal processes can often be characterized by peak reaction temperatures, pre-exponentials, and activation energies, as well as by other parameters. Values of the exponential integralEi(−x), or of a related integralI(x), where the numeric argumentx is a function of activation energy and temperature, are essential to the analyses of many of these processes. It is shown that the use of only the first term of the concomitant asymptotic series to approximate these integrals can result in less reliability than the uncertainty in thermal reaction data. Hence, values ofI(x) which are accurate to 4 significant digits over the range ofx from 15 to 50 are presented.

The determination of quartz in clay materials

Abstract: The quartz contents (maximum, 4 wt.%) of four clay materials and a tourmaline were determined by differential thermal analysis, by X-ray diffraction and by chemical analysis. The results are used to make a critical comparison of these three methods. DTA gives a better precision than X-ray diffraction analysis. The chemical method is judged unreliable in that feldspar and mica, present as minor components, are recorded in part as quartz.

Thermal investigation of polyols

Abstract: The thermal behaviour of D-mannitol, dulcitol, D-sorbitol, the semihydrate of D-sorbitol, L-arabitol, xylitol and ribitol was investigated by means of differential thermal analysis and a derivatograph. All these polyols are stable up to 200–250°. The endothermic peaks on the DTA curves at lower temperatures are due to melting. These effects are not accompanied by an increase in the electric conductivity. The hexitols decompose endothermally at boiling above 200–250°, the majority of the decomposition products boil out, and the residue is oxidized. The beginning of the decomposition of the pentitols is accompanied by an exothermic peak.

Thermal studies of polyvinylcarbazole and polyvinyldibromocarbazole

Abstract: The thermal stabilities and behaviour of polyvinylcarbazole and polyvinyldibromocarbazole were investigated by a derivatograph. The initial and final temperatures of decomposition of these polymers were determined and their thermal properties compared.

Analyse thermique differentielle et cinetique de reaction: III. Surface des pics d'analyse thermique differentielle et applications

Abstract: It is shown how the heat of fusion (or solidification), and sometimes the specific heat, can be calculated from DTA curves. Expressions for the peak areas of DTA curves are also derived from relations presented in Parts I and II. Accuracy and limits of the DTA method for the determination of kinetic parameters and heat of transformation are given.RésuméOn montre tout d'abord comment les courbes d'analyse thermique différentielle peuvent servir à déterminer des chaleurs de fusion (ou de solidification), et dans certains cas, des chaleurs spécifiques. On établit ensuite l'expression de la surface des pics d'analyse thermique différentielle à partir des relations établies dans les deux premières parties. Enfin, on montre les limites des possibilités de l'analyse thermique différentielle dans la détermination des paramètres cinétiques et des chaleurs de transformation.ZusammenfassungEs wurde gezeigt, wie sich DTA-Kurven zur Bestimmung von Schmelz-(Erstarrungs-) wärmen und, in gewissen Fällen, von spezifischen Wärmen verwenden lassen. Mit Hilfe vorgegebener Gleichungen wurden Spitzenflächen von DTA-Kurven ermittelt. Es wurde weiterhin auf die Grenzen der Anwendbarkeit der DTA-Methode zur Bestimmung von kinetischen Parametern und Umwandlungswärmen hingewiesen.РезюмеДано описание расчет а тепла ассоциации (ил и затвердевания), а иног да и удельной теплоты по д ифференциальным термоаналитическим кривым. Выражения пло щади пиков дифференциаль ных термоаналитичес ких кривых также дифференциров аны по соотношениям, выведе нным в части I и II. Привед ены точность и границы те рмоаналитического метода для определен ия кинетических пара метров и теплоты превращений.

Determination of water content by means of the Derivatograph

Abstract: The determination of water content by means of the Derivatograph is treated in the paper. The determination of water in analytical precipitates, various pharmaceutical products, biological substances, the products of food industry is treated on the basis of some practical examples. The applicability of the Derivatograph for determining the adsorption capacity of industrial adsorbents, the hydration conditions of cement, the system Ca3A-CaSO4 · H2O and the rehydrability of clay minerals is demonstrated. The aluminium oxide barrier layers were investigated on the basis of the water content of the aluminium hydroxide. For the characterization of the different strengths by which water is bound in strontium chloride hydrates the apparent activation energies are also presented.

Les complexes halogenes d'iridium

Abstract: Les hexachloroiridates de potassium, ammonium, rubidium et cesium forment une famille de complexes isomorphes qui cristallisent dans le systeme cubique a faces centrees. La dissociation thermique des hexachloroiridates de potassium, rubidium et cesium, sous atmosphere inerte, se deroule en deux etapes a des temperatures superieures a 500° en donnant l'iridium metallique et le chlorure correspondant qui se volatilise partiellement. La bande d'absorption infrarouge de la vibration de valence (v3) de la liaison Ir-Cl est situee entre 323 et 308 cm−1.

Kaolinite-mullite series: Firing vs. reactive hot-pressing

Abstract: The effect of an applied pressure on the transformation of metakaolin to spinel has been studied under reactive hot-pressing conditions and the results are compared with the conventionally fired clays. For the experiments both Georgia kaolin and a Canadian fireclay (kaolinitic) were used. The results indicated that the transformation temperature of metakaolin to spinel can be lowered by the application of an external pressure, confirming the earlier work of Carruthers and Wheat. The application of Clapeyron-Clausius equation showed that in order to lower the transformation temperature, the enthalpy change (ΔH) for this transformation has to be positive, contrary to experimental DTA plots, where an exothermic reaction is generally encountered. This anomalous behaviour can be explained, if it is accepted that the exothermic peak at about 900°C in the kaolinite to mullite transformation sequence is due to the crystallization of amorphous silica, as suggested by Nicholson and Fulrath.

A thermogravimetric study of some dithiocarbamate fungicides

Abstract: A series of dithiocarbamate-based fungicides was investigated by thermogravimetry and differential thermal analysis. The differences in the thermal decompositions of various dithiocarbamate derivatives were traced to differences in their structures. The characteristic sections of the thermogravimetric curves of the group of fungicides based on ethylene-bis-dithiocarbamates of bivalent metal ions were established. On the basis of the differences in the shapes of the T and TG curves some fungicides can be identified. A group-method was developed for the quantitative determination of the active ingredient in fungicides based on the ethylene-bis-dithiocarbamates of bivalent metals, the characteristic shape of the TG curve being utilized for analytical purposes.

Apport de l'analyse thermique differentielle quantitative a l'etude du polymorphisme du nitrate de potassium a la pression atmospherique

Abstract: Application de l'ATD quantitative a l'etude des transformations structurales du nitrate de potassium. Les echantillons (1 a 8 mg) sont chauffes et refroidis dans l'azote sec, a la pression atmospherique. Au refroidissement, on observe toujours les transitions successives I → III → II. Le pic exothermique correspondant a I → III apparait dans un intervalle de temperature tres reproductible (118 – 120°). Les mesures de surface confirment la parfaite reversibilite de I ⇄ III deja signalee par C. Mazieres. Les transitions III → I et II → I ont lieu pratiquement a la meme temperature (127–130°) mais l'aire du pic endothermique correspondant a III → I est plus faible et represente 51.5 % de la valeur observee pour II → I. En prenantΔH=13.2 cal/g comme valeur de reference pour la transition II → I, on trouveΔH=6.8± 0.2 cal/g pour III → I. La transformation III → II suit un processus en deux etapes, fortement influence par le traitement thermique anterieur de la phase I.

Heterogeneous reactions of solid nickel(II) complexes, IV: Thermal decomposition of compounds of the type Ni(NCS)2L2 Part B: Thermochemical properties

Abstract: The decomposition heats (ΔH) for complexes of the type Ni(NCS)2L2 were studied by means of a differential scanning calorimeter. From the decreasing values ofΔH the following order has been established:a) for pseudooctahedral complexes: py >β-pic > > Q; andb) for square-planar complexes: 2,6-lut > Q >α-pic. The results obtained are compared with the data from the TG, DTG, and DTA curves.RésuméDétermination par analyse enthalpique différentielle des chaleurs de décomposition (ΔH) des complexes de formule générale Ni(SCN)2L2. Le classement des valeurs deΔH par ordre décroissant montre que pour les complexes pseudo-octaédriques py >gb-pic > Q et que pour les complexes plans carrés lut-2,6 > Q >α-pic. Comparaison de ces résultats avec les données des courbes TG, TGD et ATD.ZusammenfassungEs erfolgte die Bestimmung der Zersetzungswärmen (ΔH) der Komplexe vom Typ Ni(NCS)2L2 durch die Differential Scanning Calorimetrie. Mit abnehmendenΔH Werten ergab sich die Reihenfolge:a) Pseudooktaedrische Komplexe: Py >ß-Pic > Q;b) Quadratische Komplexe: 2,6-Lut. > Q >α-Pic. Ergebnisse mit aus den DTA, TG und DTG-Kurven gewonnenen Resultaten wurden verglichen.РезюмеС помощью сканирующе го калориметра изуче на теплота распада (ΔH) дл я комплексов типа Ni(NCS)2L2. В р яду уменьшающих вели чинΔH найден следующий пор ядок: а) для псевдооктаэдри ческих комплексов ру >β-pic > Q; и б) для планарных комплексов 2,6 lut > Q >α-Pic. Полу ченные результаты сравнены с данными, по лученными исходя из кривых ТГ, ДТ Г и ДТА.

Analyse thermique differentielle et cinetique de reaction

Abstract: On etablit theoriquement, moyennant des approximations justifiables, l'equation de la courbe de temperature differentielleΔT - f[Θ,α(t)] dans le cas des reactions heterogenes comportant une phase solide et s'accompagnant d'une perte de masse;Θ est la vitesse de chauffe supposee constante, etα(t) un parametre fonction du tempst, caracterisant le degre d'evolution de la reaction consideree. La relation obtenue traduit bien l'allure et les proprietes generales des courbes d'analyse thermique differentielle experimentales.

Determination of the kinetic parameters from differential thermal analysis

Abstract: A theory of differential thermal analysis for a block-type system with spherical cells packed with inert material is developed. From the solution of DTA equations, a method for determining the reaction order, activation energy and frequency factor of the Arrhenius equation is presented. This method is applied to the decomposition of magnesite. The agreement between theory and experiment is very good.

Analyse thermique differentielle et cinetique de reaction: II. Equations des courbes d'analyse thermique differentielle

Abstract: Equations are given for describing the differential temperature curves of phase transformation (fusion and solidification) and allotropic transformations, as well as of dismutation reactions proceeding without any change in weight. It is shown how the obtained relationships are modified according to whether the reaction proceeds with or without weight change. Finally, the properties of the derivative d/dt gDT are established theoretically that can be used to advantage in the investigation of heterogeneous kinetics on the basis of DTA curves.RésuméDans cette seconde partie, en désignant parθ la vitesse de chauffe supposée constante etα(t) un paramètre dépendant du tempst, caractérisant le degré d'évolution de la transformation considérée, on établit les équations des courbes de température différentielleΔT== f [θ, α(t)] dans le cas des transformations de phase (fusion, solidification) des transformations allotropiques et dans le cas des réactions de dismutation sans variation de masse. On montre également comment les relations obtenues sont modifiées lorsque l'on considère les réactions avec ou sans variation de masse, inverses de celles déjà étudiées. Enfin, on établit théoriquement les propriétés de la dérivée d/dt ΔT, propriétés dont une est mise à profit dans certaines études de cinétique hétérogène faites à partir des courbes d'analyse thermique différentielle.ZusammenfassungDie Gleichung der differentialthermoanalytischen KurveΔT == f[θ, α(t)] für den Fall von Phasenumwandlungen (Schmelzen, Erstarren), von allotropen Umsetzungen und von ohne Gewichtsänderung verlaufenden Umwandlungsreaktionen wurden theoretisch abgeleitet, wobeiθ die konstante Aufheizungsgeschwindigkeit,α(t) ein zeitabhängiger, den Verlaufsgrad der Reaktion kennzeichnender Parameter ist. Es wurde gezeigt, wie sich die erhaltenen Beziehungen ändern, wenn die Reaktionen mit oder ohne Gewichtsänderung in entgegengesetzter Richtung verlaufen. Gewisse Eigenschaften der Derivierten d/dtΔT wurden theoretisch untersucht. Eine von ihnen läßt sich bei der Untersuchung der Kinetik von heterogenen Reaktionen durch die Differentialthermoanalyse verwenden.РезюмеВ данной части II для слу чая превращений, заключающихся в изме нении фазы (плавление, затве рдевание) аллотропно м изменении и дисмутадии без изме нения массы, введено теорет ическое уравнение из менения температурыΔT=f[θ,α(t)], гдеθ является постоянно й скоростью нагрева,α(t) — параметр, зависящий от времени, описывающ ий развитие превращени я в течение экспериме нта. Показано как можно из менить эти соотношения в слу чае реакций обратных тем, которые были изучены без изме нения массы. Установлены те оретически некоторы е особенности функции d/dt ΔT; одна из этих особенностей исполь зована в расчетах при изучении кинетики некоторых г етерогенных реакций.

Investigation of surface phenomena on solid catalysts by thermogravimetry: I. Methyl alcohol and cumene on the surface of zeolites and silica gels treated with sodium hydroxide

Abstract: Thermogravimetry was applied to the investigation of the phenomena of adsorption, chemisorption, desorption and surface reactions on solid catalysts. The measurements were carried out with 13 NaX and NaY type zeolites and with silica gels treated with sodium hydroxide, in the presence of cumene and methanol. On the basis of the quantitative results it is possible to give an interpretation of surface phenomena and to establish the existence of various active centres on the surface of the catalysts.RésuméOn a appliqué la méthode thermogravimétrique à l'étude des phénomènes d'adsorption, de chemisorption et de désorption ainsi qu'aux réactions de surface sur des catalyseurs solides. Les mesures ont été effectuées sur zéolites de type 13 NaX et NaY et sur des silicagels traités par la soude en présence de cumène et de méthanol. Des résultats quantitatifs permettent de donner une interprétation des phénomènes de surface et d'établir l'existence de divers centres actifs à la surface des catalyseurs.ZusammenfassungAdsorptions-, Chemisorptions- und Desorptionserscheinungen, sowie Oberflächenreaktionen an festen Katalysatoren wurden thermogravimetrisch untersucht. Die Messungen wurden an Zeoliten der Typen 13 NaX und NaY und an mit Natriumhydroxid behandelten Silikagelen in Gegenwart von Cumol und Methanol durchgeführt. Aufgrund der quantitativen Ergebnisse war es möglich, die Oberflächenerscheinungen zu deuten und das Vorhandensein von verschiedenen aktiven Zentren an der Katalysatoroberfläche nachzuweisen.РезюмеОписано использован ие термогравиметричес кого метода для иссле дования адсорбции, хемосорбции, десорбц ии и реакций, происходящих на пове рхности твердых катализаторов. Этот м етод, хотя и имеет неко торые недостатки, но облада ет тем преимуществом, что дает возможность определять одновременно измене ния массы и тепловых эффектов, происходящ ие в исследованной си стеме. Измерения проведены с цеолитами типа 13 NaX и NaY и силикагелем, обра ботанным гидроокись ю натрия в присутствии кумена и метанола. На основан ии полученных количе ственных результатов возможн а интерпретация поверхностных явлен ий и установление нал ичия различных активных ц ентров на поверхности катализ атора.

Baseline interpolation in DTA and DSC quantitative analysis of slow processes

Abstract: A simple method is described for use with the differential scanning calorimeter for baseline interpolation in continual processes over a wide temperature interval. For the process of water desorption from the synthetic zeolite LiA with the coveragegq=1.5, the measured heat of desorption wasQ=11.2±0.5 kcal/mole.

Evolution thermique des zeolites synthetiques de type “4 A”

Abstract: Afin d'expliquer certaines divergences concernant le nombre d'effets exothermiques observes en ATD au cours de la decomposition de zeolites de type “4 A” de diverses origines, les auteurs ont enregistre les courbes d'ATD de 14 echantillons preleves a des temps donnes au cours d'une synthese realisee dans des conditions telles que la valeur du rapport molaire silice/alumine soit inferieure a la valeur 2 theorique. Ces essais ont permis de montrer que les courbes d'ATD pouvaient presenter — soit deux — soit trois effets exothermiques au-dela de 800°. Le troisieme qui se manifeste, entre 900 et 1000°, et qui est associe a la transformation carnegieite-nepheline, presente une frequence d'apparition qui varie de facon tout a fait aleatoire en fonction du temps de cristallisation. Compte tenu des observations de Berger et Yakoblev, sa manifestation ou son absence a pu etre attribuee a une heterogeneite dans la composition des prelevements; de faibles ecarts a la valeur 1,85 choisi arbitrairement pour le rapport silice/alumine pouvant influer de facon tres sensible sur la cinetique de formation de la nepheline entre 900 et 1000° lors du traitement thermique.

How is an acceptable Nomenclature system achieved

Abstract: The philosophy and procedure adopted by the Nomenclature Committee of the International Confederation for Thermal Analysis are briefly outlined with illustrative examples taken from the contents of the two reports so far prepared.

Investigation of the thermal decomposition of some periodates by means of emanation thermal analysis (ETA) and DTA

Abstract: Thermal decomposition of Be3(IO5)2 · 12H2O, Mg2I2O9 · 11H2O, Ca2I2O9 · 9H2O and Ba2I2O9 · 9H2O in the temperature interval of 20 to 600° was studied by means of emanation thermal analysis (ETA) and differential thermal analysis (DTA). The magnetic properties of decomposition intermediates of periodates studied are discussed.

Contribution de l'analyse thermique a l'etude des acides humiques et de leurs sels de sodium

Abstract: On a etudie le comportement thermique sous oxygene des acides humiques et de leurs sels de sodium. On prepare les humates de sodium, soit par neutralisation des acides humiques, soit par dialyse de leurs pseudo-solutions dans la soude. L'examen des spectres infrarouges et de diffraction X des prelevements effectues entre les etapes de dissociation (suivie par ATD-TG -TGD) suggere un double mecanisme. Au-dessous de 500°, il s'est forme du carbonate de sodium et du carbone. Des 600°, debute la dissociation du carbonate. Le carbone restant s'oxyde brutalement a 770°. L'importance de la reaction varie avec la teneur initiale en sodium.

Study of the thermal decomposition of solids in a fluidized bed, III

Abstract: The influence of the air humidity upon the thermal decomposition of diammonium hydrogen phosphate was studied in a fluidized bed, under isothermal conditions. It was found that the increase of the decomposition rate is influenced directly by the partial pressure of the water vapour in the air, and indirectly by the working temperature. The moisture effect is explained by the salt hydrolysis in the water condensed on the grain surface. The energy of activation of the thermal decomposition decreases when the air humidity increases.