Showing papers on "Thermogravimetric analysis published in 1977"
TL;DR: In this paper, a comparative study of phase-boundary and diffusion-controlled reactions has been carried out using thermogravimetric data, and the results reported support the hypothesis that a single TG diagram does not allow the determination of whether a solid decomposition reaction is controlled by a diffusion mechanism or governed by the movement of an interface coming from a nucleation process.
98 citations
TL;DR: In this paper, isothermal and dynamic techniques were employed to examine the rate of weight loss of CaCO3 in an atmosphere of He, N2, Ar, and various percentage of CO2 in Ar.
67 citations
TL;DR: In this paper, the kinetics of anhydride formation of poly(acrylic acid) (PAA) in porous PAA-alumina composites have been investigated by using a thermogravimetric technique (TGA).
Abstract: The kinetics of anhydride formation of poly(acrylic acid) (PAA) in porous PAA–alumina composites have been investigated by using a thermogravimetric technique (TGA). Three distinct reaction peaks at 200°C (I), 250°C (II), and 390°C (III) were identified in the dynamic TGA thermogram. These peaks were attributed to bound water removal (I), anhydride formation (II), and polymer degradation (III). The kinetics of the anhydride reaction were studied in a temperature range of 220–240°C and found to follow a second-order mechanism with an activation energy of approximately 38 kcal/mole. In addition, the bound water was found to inhibit the onset of anhydride formation. The degree of conversion to anhydride was correlated with the equilibrium swelling level attained by the composite in water.
36 citations
TL;DR: The oxide that grows on aluminum metal on exposure to room temperature air is similar in both its physical and chemical properties to γ-alumina as discussed by the authors, but it is not an aluminum hydrate.
34 citations
TL;DR: In this article, different techniques were applied to convert samples of sodium beta alumina to hydronium boric acid, and the results showed that the conversion appears to proceed with a moving boundary from the surface into the bulk.
33 citations
TL;DR: In this paper, a thermogravimetric study of the decomposition of cobalt salts together with surface area measurements indicated the best choice of starting compound and optimum decomposition temperatures for the preparation of high-area Co3O4 powder catalysts.
30 citations
TL;DR: In this paper, the influence of red phosphorus on the rate of thermal degradation of poly(ethylene terephthalate) has been studied in the temperature range of 400° to 500°C in inert and oxidizing atmospheres by means of isothermal thermogravimetric analysis.
Abstract: The influence of elemental red phosphorus on the rate of thermal degradation of poly(ethylene terephthalate) has been studied in the temperature range of 400° to 500°C in inert and oxidizing atmospheres by means of isothermal thermogravimetric analysis. Addition of red phosphorus is found to reduce the rates of both the pyrolytic and the thermo-oxidative degradation and to increase the amount of residual char. A correlation of pyrolysis rates with oxygen index data has been attempted.
30 citations
TL;DR: In this paper, the chemical and thermal properties of sputtered aluminum oxide films were examined, showing that the anomalous expansion is cumulative with additional higher temperature heating, similar to a thermal ratchet effect, until a temperature of 850°C.
Abstract: The chemical and thermal‐mechanical stability of sputtered aluminum oxide films are examined. Sputtered alumina is quite soluble in bases and phosphate‐containing solutions. Carbon dioxide was detected in the films by infrared spectroscopy and by mass spectroscopy during thermal gravimetric analysis; the presence of CO2 is likely due to adsorption on the sputtered film. Heating and cooling of sputtered alumina results in an irreversible expansion of the film. The anomalous expansion is cumulative with additional higher temperature heating, similar to a thermal ratchet effect, until a temperature of 850°C is reached. At temperatures above 850°C rapid argon evolution from the sputtered film occurs and is accompanied by film contraction.
23 citations
TL;DR: In this paper, non-isothermal thermogravimetric analysis was used for determination of the kinetics of aluminium hydroxide dehydration in an air atmosphere and for processing of the experimental results by the method due to Chatterjee.
Abstract: Non-isothermal thermogravimetric analysis was used for determination of the kinetics of aluminium hydroxide dehydration in an air atmosphere and for processing of the experimental results by the method due to Chatterjee.
23 citations
TL;DR: An efficient non-template synthesis of a new macrocycle, a conjugated tautomer of 1,14 : 7,8-diethenotetrapyrido, is described in this paper.
Abstract: An efficient non-template synthesis of a new macrocycle, a conjugated tautomer of 1,14 : 7,8-diethenotetrapyrido-[2,1,6-cd:2′,1′,6′-gh :2″,1″,6″-jk:2‴,1‴,6‴-na][1,4,8,11]tetra-azacyclotetradecine (3), is described. The thermal behaviour of several disubstituted 1,10-phenanthrolines towards dimerization is studied by use of differential thermal analysis and thermogravimetric analysis, and some spectroscopic properties of the macrocycles produced are described.
20 citations
TL;DR: In this paper, the thermal stability of several series of polyitaconates has been assessed using thermogravimetric and thermal volatilisation techniques, and general degradation patterns have been established.
Abstract: The thermal stability of members of several series of polyitaconates has been assessed using thermogravimetric and thermal volatilisation techniques. From these data general degradation patterns have been established. The poly (di-n-alkyl itaconates) are stable up to 570K before chain breakdown occurs. The poly(mono-n-alkyl itaconates) are less stable and undergo a dehydration/de-esterification reaction at 430K which results in the formation of anhydride structures. This reaction can be suppressed by the formation of the salts. In the copolymers, salt formation also leads to increased stability but the range of copolymers studied was too restricted to draw general conclusions about their thermal behaviour.
TL;DR: In this article, molecular weight and thermal stability measurements on the presumed polymers of aminoborane, H2BNH2, and aminodifluorobborane, F2NBH2 were explored using a laser light scattering technique for the molecular weight measurements and both differential thermal analyses and thermogravimetric analyses for the thermal stability studies.
Abstract: Molecular weight and thermal stability measurements on the presumed polymers of aminoborane, H2BNH2, and aminodifluoroborane, F2BNH2, were explored using a laser light scattering technique for the molecular weight measurements and both differential thermal analyses and thermogravimetric analyses for the thermal stability studies. Weight-average molecular weight of polymeric aminodifluoroborane in water was determined as 23,000 g/mole, whereas the molecular weight of polymeric aminoborane could not be determined since a suitable solvent was not found. Both DTA and TGA observations showed partial decomposition of polymeric aminoborane between 135° and 200°C, and the vaporization of polymeric aminodifluoroborane between 250° and 360°C.
TL;DR: In this article, a ternary phase was precipitated when the ZnCl2 solutions were diluted to a pH of 5.48 ± 0.05, and the resulting phase diagram showed 2 ternaries phases, 4ZnO·ZnCl 2·5H2O (4·1·5) and ZnO-ZnCL2·2H 2O (1.1.2).
Abstract: Solutions of ZnCl2 were prepared from ZnCl2·nH2O and by reaction of zinc metal with HCl. Specific gravities and pH values were determined as a function of composition. A ternary phase, 4ZnO·ZnCl2·5H2O, was precipitated when the ZnCl2 solutions were diluted to a pH of 5.48 ± 0.05. Mixtures of ZnO with ZnCl, and HCI solutions were equilibrated in sealed containers and analyzed by X-ray diffraction. The resulting phase diagram shows 2 ternary phases, 4ZnO·ZnCl2·5H2O (4·1·5) and ZnO·ZnCl2·2H2O (1.1.2), both of which are soluble to the extent of < 1 wt% in ZnCl2 solutions. Thermogravimetric data indicate that the 1.1.2 phase loses half the constituent H2O at ∼230°C and the remainder, with ZnCl2, at higher temperatures. The 4.1.5 phase dissociates to ZnO and 1.1.2 at ∼160°C. The system ZnCl2-H2O is not binary, but is a section through the ternary system ZnO-HCl-H2O, with the solubility curve of the 4.1.5 phase intersecting the ZnCl2-H2O section in dilute solutions.
TL;DR: A thermal analytical study of Li, Na, K, Rb, Cs, NH4, Mg, Ca, Sr, Ba and Zn dithionates is reported in this article.
Abstract: A thermal analytical study of Li, Na, K, Rb, Cs, NH4, Mg, Ca, Sr, Ba and Zn dithionates is reported. The decomposition of the dithionate ion is endothermic in the case of the Na, K, Rb, Cs and NH4 salts, but exothermic with Li, Mg, Sr, Ba and Zn. Kinetic parameters have been derived from the TG curves by means of the Coats-Redfern method. The validity of a linear kinetic compensation law is reported for the loss of crystal water and separately for the decomposition of the dithionate ion.
TL;DR: The current recycle fissile fuel for steam cycle high-temperature gas-cooled reactors in the U.S. is derived from weak acid ion-exchange resin microspheres loaded with uranyl ions as discussed by the authors.
Abstract: The current recycle fissile fuel for steam cycle high-temperature gas-cooled reactors in the U.S. is derived from weak acid ion-exchange resin microspheres loaded with uranyl ions. This material offers great versatility in the control of chemical and physical properties through careful process control. Processing the upgraded loaded resin begins with thermal decomposition or carbonization, which yields finely dispersed UO/sub 2/ in a porous carbon matrix. This step requires a controlled heating rate from 350 to 450/sup 0/C, and is complete by approximately 900/sup 0/C. If carbide or mixed-oxide/carbide fuel is desired, carbothermic reduction, or conversion, is done at 1500 to 1750/sup 0/C. This step reduces the UO/sub 2/ to UC/sub 2/ to optimize irradiation performance. Physical properties after carbonization correlate with the observed thermogravimetric behavior. The mercury density, volume decrease, weight loss, bulk density, carbon content, and particle size depend strongly on the particular heating rate employed through the 350 to 450/sup 0/C region. The conversion process generally follows the anticipated thermodynamic behavior for removal of carbon monoxide based on its partial pressure. The particular phases present after conversion can be manipulated by controlling the conversion temperature or by additions of hydrogen or carbon monoxide to the fluidizing gas.
TL;DR: In this paper, the temperature dependence of the preexponential factor in the Arrhenius expression for the rate constant has been investigated for both thermogravimetric and derivative data.
Abstract: The well-known methods of Coats-Redfern, Freeman-Carroll, and Achar et al. are modified to include the temperature dependence of the pre-exponential factor in the Arrhenius expression for the rate constant. These modifications serve to cast these methods into their most general Arrhenius form. Suggestions are given regarding various numerical methods for extracting the temperature dependence of the preexponential factor from thermogravimetric and derivative thermogravimetric data.
TL;DR: In this article, three polyphenylquinoxalines were prepared by the one-step solution cyclopolycondensation of 3,3′,4, 4,4′-tetraaminobenzophenone with three bisbenzils containing oxyphenylene groups.
Abstract: Three polyphenylquinoxalines were prepared by the one-step solution cyclopolycondensation of 3,3′,4,4′-tetraaminobenzophenone with three novel bisbenzils containing oxyphenylene groups. High molecular weight polymers were obtained that exhibited good solubility in chlorinated solvents and m-cresol and formed tough, flexible films from solution. Glass transition temperatures Tg which were determined by thermomechanical analysis, torsional braid analysis, and dielectric loss measurements showed that the inclusion of oxyphenylene units into the polymer chain was effective in reducing the Tg. However, the onset of polymer decomposition, as determined by thermogravimetric analysis and isothermal aging, disclosed that the oxyphenylene units also decreased the thermooxidative stability for two of the polymers studied.
TL;DR: In this paper, a systematic study about the thermal decomposition kinetics in function of substituted bases in (BH) 2 Mo 4 O 13 type compounds shows a decomposition pattern with three or two steps which are controlled by a random nucleation mechanism.
TL;DR: In this article, the applicability of the thermogravimetric technique in the determination of the degree of conversion of two standard high alumina cement (HAC) concrete samples was evaluated.
TL;DR: In this article, the enthalpy and activation energy for the oxidation of CuFeO2 were calculated to be ∼26.6±2 and ∼18±2 kcal mol−1 respectively.
Abstract: The oxidation kinetics of CuFeO2 have been studied between 500 and 1000° C under various oxygen partial pressures using thermogravimetric analysis (TGA). The oxidation rate was found to increase as the oxygen partial pressure was increased, and for a given partial pressure of oxygen it was found to be maximum at ∼700° C. The enthalpy and activation energy for the oxidation of CuFeO2 were calculated to be ∼26.6±2 and ∼18±2 kcal mol−1 respectively. The oxidation of CuFeO2 resulted in the formation of CuFe2O4 and CuO, and the rate of reaction followed an S-type curve as found in the pearlitic transformation in steels.
TL;DR: In this paper, the TGA method was used in studies of the thermal decomposition of copolymers of styrene with 1,2,2-tetrachloroethyl esters of acrylic and fumaric acids, and of homopolymers of halogenated monomers and mixtures of polystyrene with poly[N-2,4,6-trichlorophenyl)maleimide.
TL;DR: A number of alcoholate complexes of chromium chloride with the general formula, CrCl3 · xROII (R = Me, Et, i-Pr, n-Bu and n-Ilexyl; x = 3 and 4) have been synthesized by the reactions of CrCl 3 · 3 TIIF with an excess of the appropriate alcohols under reflux.
Abstract: A number of alcoholate complexes of chromium chloride with the general formula, CrCl3 · xROII (R = Me, Et, i-Pr, n-Bu and n-Ilexyl; x = 3 and 4) have been synthesized by the reactions of CrCl3 · 3 TIIF with an excess of the appropriate alcohols under reflux. Physicochemical studies such as i.r., visible reflectance, electron spin resonance spectra and thermogravimetric measurements, in addition to elemental analyses, throw light on the structure of these complexes.
TL;DR: In this article, a bisphenol F-based rubberized epoxy, cured with aromatic amines, is described as an epoxy material suitable as a matrix system for wet filament winding.
TL;DR: Aromatic polyimides were synthesized by polymerization of 1,4,5,8-naphthalenetetricarboxylic dianhydride and 2-dialkylamino-4,6-dihydrazino-1,3,5-triazines by a solution polymerization method followed by cyclodehydration as discussed by the authors.
Abstract: Aromatic polyimides were synthesized by polymerization of 1,4,5,8-naphthalenetetracarboxylic dianhydride and 2-dialkylamino-4,6-dihydrazino-1,3,5-triazines by a solution polymerization method followed by cyclodehydration. The polyimides had number-average molecular weights over 13,000–16,000 or viscosity values of 0.23–0.65 dl/g. The x-ray diffraction diagram of polyimide I showed a crystal pattern, but the pattern became less pronounced with increasing length of the polymer side chain, and thus polyimide V showed a typical amorphous pattern. Study of the thermal stability of the polyimides by thermogravimetric analysis showed that a steep weight loss occurred in the range 380–410°C. Among the polyimides, I had only poor solubility in organic solvent, while IV and V were soluble even in general organic solvents such as tetrahydrofuran and dioxane.
TL;DR: In this paper, the best conditions for the preparation of potassium hexafluorovanadate(III) were determined by means of thermogravimetric analysis, differential thermal analysis and X-ray diffraction analysis.
Abstract: In order to determine the best conditions for the preparation of potassium hexafluorovanadate(III), the reaction of V2O3 with KHF2 was studied by means of thermogravimetric analysis, differential thermal analysis and X-ray diffraction analysis. The reaction begins at about 225 °C and terminates at about 300 °C and the decomposition of excess KHF2 terminates at from 300 to 450 °C, depending on the amount of the mixture of V2O3 and KHF2. Potassium hexanuorovanadate(III) is stable in air up to about 300 °C and is oxidized at temperatures higher than 300 °C. Potassium hexanuorovanadate(III) has four polymorphic forms, and the transition points are 158, 200, and 218 °C. The transition from δ to γ or from γ to β on cooling is hindered by adding a small amount of sodium ion.
TL;DR: In this article, the thermal oxidation of isotactic poly(4-methyl-1-pentane) was studied in the bulk phase using thermogravimetric analysis (t.a.) at temperatures from 155° to 185°C and oxygen concentration from 75 to 100% by volume.
TL;DR: In this article, the thermal decomposition of hydrazinium monoperchlorate (HP-1) in the molten state has been investigated using differential thermal analysis, thermogravimetric analysis, a constant volume manometric technique and mass-spectrometry.
Abstract: The thermal decomposition of hydrazinium monoperchlorate (HP-1) in the molten state has been investigated using differential thermal analysis, thermogravimetric analysis, a constant volume manometric technique and mass-spectrometry. The stoichiometry of the reaction can be represented by the equation: 20 N2H5C1O4 → 13 NH4C1O4 + 3.5 Cl2 + 2 O2 + 13 N2 + 0.5 N2O + 0.5 H2 + + 23.5 H2O The data seem to indicate that the mechanism, which involves an associated complex, remains unchanged from 140 to 190°. Consequently, impurities capable of forming associated complexes with the hydrazinium or the perchlorate ion desensitize the thermal decomposition of HP-1, the extent of desensitization being determined by the size, the charge and the concentration of the impurity.
TL;DR: In this article, the results of simultaneous thermogravimetric and differential scanning calorimetric measurements of PTOX have been analyzed by using a sample pan system with good thermal conductivity and good thermal contact.
Abstract: Thermally unstable poly (trioxane) (PTOX) has been studies by simultaneous thermogravimetric and differential scanning calorimetric measurement in order to clarify the melting behavior. When the sample pan system has good thermal conductivity and good thermal contact, the decomposition of poly (trioxane) takes place after melting. In this case the profile of melting endotherm does not require a correction for the thermal decomposition in obtaining the melting point and the enthalpy of melting. In order to compare the results of thermogravimetry and differential scanning calorimetry, the lid of a sample pan system must have high thermal conductivity and have space for dissipation of gases evolved. Usage of a silver net lid with good thermal contact is thus recommended.