Showing papers in "Journal of Thermal Analysis and Calorimetry in 1989"
TL;DR: In the last few years, a new generation of materials can polycondense just like organic polymers, at temperatures lower than 100 deg. C. This new generation, whether used pure, with fillers or reinforced, is already finding applications in all fields of industry as mentioned in this paper.
Abstract: Spectacular technological progress has been made in the last few years through the development of new materials such as ‘geopolymers’, and new techniques, such as ‘sol-gel’. New state-of-the-art materials designed with the help of geopolymerisation reactions are opening up new applications and procedures and transforming ideas that have been taken for granted in inorganic chemistry. High temperature techniques are no longer necessary to obtain materials which are ceramiclike in their structures and properties. These materials can polycondense just like organic polymers, at temperatures lower than 100 deg. C. This new generation of materials, whether used pure, with fillers or reinforced, is already finding applications in all fields of industry. Some examples:
pure: for storing toxic chemical or radioactive waste, etc.
filled: for the manufacture of special concretes, molds for molding thermoplastics, etc.
reinforced: for the manufacture of molds, tooling, in aluminum alloy foundries and metallurgy, etc.
773 citations
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TL;DR: In this article, a theoretical examination of various ignition models and experimental approaches is presented, including condensed phase ignition, thermal radiative and convective ignition, general ignition theory, initiation of chemical reactions, and experimental studies.
Abstract: This book is text in which a theoretical examination of various ignition models and experimental approaches is presented. The book contains papers on condensed phase ignition, thermal radiative and convective ignition, general ignition theory, initiation of chemical reactions, and experimental studies. Each chapter contains detailed theoretical treatments of the various aspects of ignition and each chapter is also supported by many references.
131 citations
TL;DR: In this article, a modification of the Nernst-Lindemann equation was proposed to convert calculated heat capacities at constant pressure to heat capacity at constant volume for solid, linear macromolecules.
Abstract: A modification is proposed for the Nernst-Lindemann equation that is used to convert calculated heat capacities at constant pressure (C
p
) to heat capacities at constant volume (C
v
) for solid, linear macromolecules. the constant A0 per mole of repeating unit in this equation is derived by taking into account the variable number of vibrators excited at different temperatures. With the new equation it is possible to calculateC
p
for solid polymers over a wider temperature range. The constant is calculated for solid polymers from experimental thermal expansivity, isothermal compressibility and heat capacity data obtained from the literature. An average value of (3.9±2.4)×10−3(K mol)/J was obtained for A0 (new) from data on 22 solid polymers. This average value may be used as a universal constant in case no experimental data on compressibility and expansivity are available for computation ofA
0. The remaining variation of A0 (new) with temperature is discussed and example calculations are shown for polyethylene. Effects of premelting and possibly large-amplitude motion are discovered for polyethylene in the temperature range 290 to 410 K.
103 citations
TL;DR: In this paper, the transferability of the DTA and DSC results is given only for application in static latent heat storage units and the results are discussed in connection with the examples of Na2SO4·10H 2O, CH3COONa·3H2O, Na2S·9H 2 O, Na 2S·5H2 O, Mg(NO3)2·6H 2
Abstract: DTA and DSC methods and quasi-isothermal and quasi-isobaric thermogravimetry are of great importance in the investigation of salt hydrates as latent heat-storage materials. However, the transferability of the DTA and DSC results is given only for application in static latent heatstorage units. Special calorimetric methods adapted to the storage principle are preferred for the study of salt hydrates under dynamic storage conditions. The findings are discussed in connection with the examples of Na2SO4·10H2O, CH3COONa·3H2O, Na2S·9H2O, Na2S·5H2O, Mg(NO3)2·6H2O, MgCl2·6H2O and the eutectic mixture of Mg(NO3)2·6H2O-MgCl2·6H2O.
102 citations
TL;DR: The theoretical upper and lower limit temperature (T(βα) and T(αβ) respectively) of β-IPP formation is demonstrated in this paper, and essential properties of crystallization, melting and recrystallization of βIPP are summarized.
Abstract: Preparation methods and thermal preconditions of formation of the β-modification of isotactic polypropylene (β-IPP) are rewieved. The existence of theoretical upper and lower limit temperature (T(βα) and T(αβ) respectively) of β-IPP formation is demonstrated. Essential characteristics of crystallization, melting and recrystallization of β-IPP are also summarized. In this respect, the attention is called to some new and peculiar phenomena, including the βα- and αβ-bifurcation of growth on the growing crystal fronts as well as the melting and annealing memory effects. Filled systems (composites) and polymer blends based on β-IPP are also covered. An interpretation to polymorphism of IPP is attempted on the basis of enantiotropy.
102 citations
TL;DR: In this article, a series of electroconducting acid-doped polyanilines were evaluated and the weight loss results suggest that the majority of dopants are eliminated between 230 °C to 350 °C leaving behind the skeletal non-conducting poly-aniline.
Abstract: Thermogravimetry (TG) has been conducted on a series of electroconducting acid-doped polyanilines The weight loss results suggest that the majority of dopants are eliminated between 230 °C to 350 °C leaving behind the skeletal non-conducting polyaniline The doped polyaniline are thermally more stable than the pristine polyaniline in air at high temperatures This suggests that despite the early elimination observed, the presence of dopant at the begining has a stabilizing effect on the skeletal polyaniline By comparison the acid-doped polyanilines are more thermally stable than many other electroconductive polymers, such as polypyrroles and polyacetylenes
62 citations
TL;DR: In this paper, a review of thermodynamic studies of clathrate hydrates, mainly of structures I and II, is presented, which is based on 147 references, with particular emphasis given to orientational ordering.
Abstract: Thermodynamic studies of clathrate hydrates, mainly of structures I and II, are considered in this review which is based on 147 references There are two main subjects The first is the host lattice energy and the guest-host interaction energy, both of these quantities being related to the enthalpy of dissociation and composition of the hydrates The second subject concerns orientational ordering phenomena occurring in both host and guest, as reflected in the low temperature heat capacity The classical theoretical treatment of clathrate formation has been reconsidered on the basis of recent experimental results Particular emphasis has been given to orientational ordering since this topic is undoubtedly central to clarifying the nature of clathrate hydrates
58 citations
56 citations
TL;DR: The mode of loss of hydroxyl group from the structure with respect to temperature is discussed in this paper, where the results were supplemented by differential thermal analysis. And the results obtained were correlated with those of the above study to investigate the pozzolanic activity at various temperatures.
Abstract: Clay from the Nagrotta area of Jammu (J & K State, India) was calcined at various temperatures. The products were analysed by X-ray diffraction. The mode of loss of hydroxyl group from the structure with respect to temperature is discussed. The results were supplemented by differential thermal analysis. The calcined products were subjected to lime reactivity tests and the data obtained were correlated with those of the above study to investigate the pozzolanic activity at various temperatures.
46 citations
TL;DR: In this article, the authors explored the facts and fictions surrounding the compensation effect and found that false compensation effect occurs mainly due to: propagation of computational and experimental errors resulting in inaccurate estimates of the Arrhenius parameters; and, the natural compensation between InA andE.
Abstract: In this article, the facts and fictions surrounding the compensation effect is explored. False compensation effect occurs mainly due to: propagation of computational and experimental errors resulting in inaccurate estimates of the Arrhenius parameters; and, the natural compensation between InA andE. Since Arrhenius parameters are sensitive to errors in temperature; the errors due to uncertainty in temperature should be minimized to eliminate false compensation effect. Increasing the experimental temperature range is helpful in minimizing errors due to uncertainty in temperature. A point of concurrence in a plot of Ink and 1/T establishes the occurrence of true compensation effect. True compensation effect has been shown to be a useful tool in chemical research for: identifying the governing reaction mechanism; predicting the effects of various reaction parameters; and, correlating and reducing experimental data.
42 citations
TL;DR: In this article, a simple kinetic model of surface-induced glass crystallization is proposed, where the grain size of glass powders, a constant density of surface nuclei and a steadily increasing temperature throughout the reaction are taken into account.
Abstract: A simple kinetic model of surface-induced glass crystallization is proposed. The grain size of glass powders, a constant density of surface nuclei and a steadily increasing temperature throughout the reaction are taken into account. The crystal growth rate and the density of surface nuclei can be estimated easily from overall kinetic curves (e.g. DTA curves) of powder of different grain size.
TL;DR: The Cone Calorimeter as mentioned in this paper is the most significant of small scale instruments in this field, and applications including correlation with large scale fire tests are discussed in detail in the paper.
Abstract: The rate of heat release is the most important parameter for characterising an unwanted fire. The oxygen consumption principle has accelerated the development and use of equipment of measure rate of heat release. The Cone Calorimeter is the most significant of small scale instruments in this field. The paper describes the apparatus and theory. Applications including correlation with large scale fire tests are discussed.
TL;DR: In this article, different formulations of diglycidyl ether of bisphenol-A, diepoxidized cardanol as reactive diluent, an anhydride as curing agent, and a tertiary amine as curing catalyst, with/without the use of an epoxy fortifier, were analyzed.
Abstract: Different formulations, composed of the diglycidyl ether of bisphenol-A, diepoxidized cardanol as reactive diluent, an anhydride as curing agent, and a tertiary amine as curing catalyst, with/without the use of an epoxy fortifier, were analysed. The effect of the fortifier on the diluent was also observed. The overall kinetics of curing was observed to follow a simple Arrhenius-type temperaturedependence, with an activation energy in the range 54–120 kJ/mol, with first-order kinetics up to 85% conversion. An increase in activation energy was observed with an increase of diluent content. The curing reaction was found to follow a three-step mechanism, involving a nucleophilic bimolecular displacement reaction, for which an explanation was offered. Incorporation of the fortifier lowers the curing temperature, but does not alter the final degree of reaction.
TL;DR: In this article, the specific contributions made by DTA and DSC are reviewed and the value/applications of this approach established, within this context the specific contribution made by the DTA approach and the specific applications of the approach are established.
Abstract: With petroleum reserves limited, and nuclear sources increasingly unacceptable, the use of coal (and potentially oil shale) is rapidly increasing as is its content of inorganics (minerals). Thermal analysis techniques are particularly suited for the evaluation, characterisation, analysis, basic, applied and pollution research of such organic and inorganic fossil fuel materials. The type, composition, quality and thermal decomposition characteristics of which control the calorific value, volatile yield, petrochemical potential, coke and fly ash derivatives together with end product ash. slag and gases such as hydrocarbons, SOx, NOx and CO2. Within this context the specific contributions made by DTA and DSC are reviewed and the value/applications of this approach established.
TL;DR: In this article, the activation energies for the dehydration and decomposition reactions in nitrogen and air media were evaluated and a tentative reaction mechanism for the thermal decomposition of the complex was proposed.
Abstract: Cobalt(II) bis(oxalato)cobaltate(II) tetrahydrate (Co[Co(C2O4)] · 4H2O) was synthesized and characterized on the basis of elemental and spectral analysis. The thermal decomposition of the complex was investigated in air and nitrogen media. In air, complete dehydration of the complex occured at 251°, followed by rapid decomposition to a mixture of CO2O3 and Co3O4 at 300°; in nitrogen, dehydration occurred at 206°, followed by decomposition to a mixture of Co and CoC2O4, and finally to Co + CoO, at 394° and 420°, respectively. The activation energies for the dehydration and decomposition reactions in nitrogen and air media were evaluated and a tentative reaction mechanism for the thermal decomposition of the complex was proposed.
TL;DR: In this article, new measurements and literature data on polysiloxanes covering heat capacities, transition parameters, enthalpies, entropies and Gibbs energies are presented and critically reviewed.
Abstract: New measurements and literature data on polysiloxanes covering heat capacities, transition parameters, enthalpies, entropies and Gibbs energies are presented and critically reviewed. TheATHAS computation method is used to bring heat capacities into agreement with an approximate frequency spectrum. The various crystal and mesophases are discussed. TheATHAS (1990) recommended data are as follows: For poly(dimethyl siloxane) the glass transition is at 146 K with an increase in heat capacity of 29.24 J/(K mol). The completely crystalline sample melts at about 219 K with a heat of fusion of 2.75 kJ/mol. For poly(diethyl siloxane) the glass transition is at 135 K with an increase in heat capacity of 34.48 J/(K mol). The completely crystalline sample changes to a condis crystal at 206.7 K with a heat of disordering of 2.72 kJ/mol. The transition to a poorly characterized “viscous crystal” with thermodynamic properties close to the melt occurs at 282.7 K with an enthalpy of transition of 1.84 kJ/mol. Final fusion occurs at 308.5 K and a small endotherm of about 231 J/mol. Tables of heat capacities, enthalpies, entropies and Gibbs energies are given from 0 K to 550 K.
TL;DR: In this paper, the authors used the Coats-Redfern and Horowitz-Metzger methods to determine the mode of decomposition of Ni(S2CNHR) dithiocarbamates to sulphide.
Abstract: Thermogravimetric and derivative thermogravimetric curves of some complexes [Ni(S2CNHR)2] (R=Me, Et, Pri, Bui, But, Bz,p-MePh,p-MeOPh,p-ClPh,p-NO2Ph) in a dynamic nitrogen atmosphere were studied to determine their modes of decomposition. All these complexes show similar TG profiles. The weight losses in the main decomposition stages indicate conversion of the nickel(II) dithiocarbamates to sulphide. Reaction orders were estimated via the shape characteristics of the corresponding derivative thermogravimetric curves and kinetic analysis of the thermogravimetric data was performed by using the Coats-Redfern and Horowitz-Metzger methods.
TL;DR: DTA, TG and DTG curves of montmorillonite and laponite treated with various amounts of acridine orange, were recorded in air, simultaneously with EGA curves of H2O, CO2, NO2, CH3 and C2H6 as mentioned in this paper.
Abstract: DTA, TG and DTG curves of montmorillonite and laponite treated with various amounts of acridine orange, were recorded in air, simultaneously with EGA curves of H2O, CO2, NO2, CH3 and C2H6. The thermal analysis curves could be divided into three regions representing dehydration of the clay, oxidation of the organic cation and dehydroxylation of the clay. The oxidation region showed two exothermic peaks representing the oxidation of H and C of the organic matter, respectively. Thermal analysis curves of laponite differred from those of montmorillonite. The profile of EGA curves of laponite did not change with the degree of saturation of the clay by the dye whereas those of montmorillonite were affected by the degree of saturation.
TL;DR: In this article, the thermal dehydration and decomposition of Zn(NO3)2·6H2O (I) were studied via DTA, TG and DSC, quantitative analysis and IR spectroscopy.
Abstract: The thermal dehydration and decomposition of Zn(NO3)2·6H2O (I) were studied via DTA, TG and DSC, quantitative analysis and IR spectroscopy, and compared with those of Zn(NO3)2·6D2O (II). The following phase transitions were observed: melting of the salts; partial dehydration to tetrahydrate; formation of basic nitrate-hydrate; and formation of ZnO.
TL;DR: In this paper, the curing behavior of bismethacryloxy derivative of diglycidyl ether of bisphenol A (vinyl ester resin) containing styrene as the reactive diluent (40% w/w) was studied using gel point determination method and DSC.
Abstract: The curing behaviour of bismethacryloxy derivative of diglycidyl ether of bisphenol A (vinyl ester resin) containing styrene as the reactive diluent (40% w/w) was studied using gel point determination method and DSC. Seven samples of styrene/α-methylstyrene in the ratio 40∶0, 35∶5, 30∶10, 25∶15, 20∶20, 15∶25 and 0∶40 were studied. Delayed curing was observed in samples containing increasing proportions of α-methylstyrene. The energy of activation decreased from 869 kJ mol−1 to 333 kJ mol−1 as the concentration of α-methylstyrene increased in the formulations. However, no difference in thermal stability was observed by replacement of styrene by α-methylstyrene. It was concluded that in vinyl ester resin samples 10–15% α-methylstyrene and 30-25% styrene can be used as reactive diluent.
TL;DR: In this article, the adsorption of crystal violet on laponite was investigated by X-ray diffraction and thermal analysis, where the evolved H2O, CO2, NO2, H2 and C2H6 were simultaneously determined by mass spectrometry.
Abstract: The adsorption of crystal violet on laponite was investigated by X-ray diffraction and thermal analysis. DTA, TG and DTG curves were recorded in air. The evolved H2O, CO2, NO2, H2 and C2H6 were simultaneously determined by mass spectrometry. The thermal analysis curves were compared on one hand with the thermal analysis curves of laponite and on the other hand with thermal analysis curves of non-adsorbed crystal violet and of crystal violet adsorbed on montmorillonite. The thermal analysis curves of crystal violet adsorbed on laponite show similarities to the curves of the non-adsorbed crystal violet, but differ from the curves of crystal violet adsorbed on montmorillonite. The differences in the thermal behaviour were attributed toπ interactions which do not occur between crystal violet and laponite but do occur between this dye and montmorillonite.
TL;DR: The phase equilibria in the total range of component concentrations in the V2O5-Cr2O3 system up to 1000 °C were studied by means of phase powder diffraction and DTA.
Abstract: The phase equilibria in the total range of component concentrations in the V2O5-Cr2O3 system up to 1000 °C were studied by means of phase powder diffraction and DTA. Two compounds exist in the system: CrVO4, melting incongruently at 860±5 °C, and Cr2V4O13, which decomposes in the solid state at 640±5 °C to CrVO4(s) and V2O5(s). At 645±5 °C, CrVO4 and V2O5 form a eutectic mixture with the CrVO4 content not exceeding 2% mol.
TL;DR: In this paper, simultaneous TG, DTA and DTA profiles of the entire combustion process were obtained to provide a set of parameters which characterize the oxidation potential of these coal samples, which can also be used to predict the combustion performance of pulverized coal in industrial furnaces.
Abstract: Simultaneous TG, DTA techniques have been applied to investigate the combustion characteristics of Victorian brown coal derived from different coal fields and including various lithotypes. TG and DTA profiles of the entire combustion process were obtained to provide a set of parameters which characterize the oxidation potential of these coal samples. These parameters can also be used to predict the combustion performance of pulverized coal in industrial furnaces. The area of the major DTA combustion peak is closely related to the heat released during the combustion process and therefore provides a means of determining the specific energy of the coal. Different lithotypes are also characterized by their corresponding TG and DTA burning profiles.
TL;DR: In this article, seven complex compounds exhibiting the compositions Ni(en)3Ni(CN)4·H2O (I), Ni(n)2Ni(cn)4 · 2.5H 2O (II) and β-Ni(n)-Ni(en)-2Ni-CN 4·2H 2 O (III) were prepared from the system Ni-en-[Ni(nc)4]2−-H 2−-O.
Abstract: Seven complex compounds exhibiting the compositions Ni(en)3Ni(CN)4·H2O (I), Ni(en)3Ni(CN)4 (II),α-Ni(en)2Ni(CN)4 (III), Ni(en)Ni(CN)4·2H2O (IV), Ni(en)Ni(CN)4 (V), Ni(en)2Ni(CN)4 · 2.5H2O (VI) andβ-Ni(en)2Ni(CN)4 (VII) were prepared from the system Ni-en-[Ni(CN)4]2−-H2O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)→(II)→(III)→(V)⇄(IV) and (VI)→(VII)→(III)→(V)⇄(IV) Process (VII)→(III) represents isomerization. The reversibility of the process (V)⇄(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.
TL;DR: In this paper, the phase diagrams of the binary systems of picric acid with naphthalene, anthracene and phenanthrene, determined by the thaw-melt method, show the formation of a molecular complex and two eutectics in each system.
Abstract: The phase diagrams of the binary systems of picric acid with naphthalene, anthracene and phenanthrene, and of α-naphthol withp-toluidine, determined by the thaw-melt method, show the formation of a molecular complex and two eutectics in each system. The heats of the pure components, eutectics and molecular complexes were determined by differential scanning calorimetry. Comparison of the experimental heats of fusion with the theoretical values calculated via the mixture law suggests cluster formation in the melts. The entropy of fusion, enthalpy of mixing and excess thermodynamic functions were also calculated from the heat of fusion data.
TL;DR: In this article, the application of thermal analysis in the study of reaction kinetics and reaction mechanisms in combination with presently available powerful analytical tools, in the sphere of materials with particular reference to high energy materials is presented and discussed.
Abstract: The application of thermal analysis in the study of reaction kinetics and reaction mechanisms in combination with presently available powerful analytical tools, in the sphere of materials with particular reference to high energy materials is presented and discussed. Also an attempt has been made to correlate the kinetic data obtained by TA with the performance characteristics, for some important materials.
TL;DR: The principles of the emanation thermal analysis, based on the measurement of inert gas release from solids, are given in this article. But the results of the computer modelling of the gas release curves during heating of porous and dispersed samples are demonstrated
Abstract: The principles of the emanation thermal analysis, based on the measurement of inert gas release from solids, are given Results of the computer modelling of inert gas release curves during heating of porous and dispersed samples are demonstrated
TL;DR: The thermal curves of diatomites (kieselguhrs) in air display different profiles, depending on the type and quantity of impurities (carbonates, clays, etc.) present.
Abstract: The thermal curves of diatomites (kieselguhrs) in air display different profiles, depending on the type and quantity of impurities (carbonates, clays, etc.) present. TG and DTG runs can be used for a quick diagnosis of quality, but also give a nearly quantitative picture of the silica content of these minerals.
TL;DR: In this article, the thermal decomposition of rare earth pentanitrato complexes has been studied by TG and DTA in both air and nitrogen, and the results showed that when M = K and Ln = La, the intermediate K2La(NO3)5 is remarkably stable and KLaO2is formed at 800°C.
Abstract: Thermal decomposition of rare earth pentanitrato complexes has been studied by TG and DTA. M2Ln(NO3)5·nH2O (M=NH4, Ln=La, Nd, Pr) decomposes in air through anhydrous (NH4)2Ln(NO3)5 to Ln(NO3)3, LnONO3 and finally to Ln2O3 above 600°C. When M=K and Ln=La, the intermediate K2La(NO3)5 is remarkably stable and KLaO2is formed at 800°C. Except for Nd, the nonanitrato complex M3Ln2(NO3)9 was detected during the degradation process in both air and nitrogen but its stability range is too narrow to allow its preparative isolation as single phase. For comparison, the TG and DSC curves were recorded for La(NO3)3·6H2O where La(NO3)3 and especially LaONO3 appear as stable intermediates.