Search Results
Abstract
The enthalpies of formation of 13 calcium silicates, aluminates, alumino-silicates and ferro-alumino-silicates were measured by dissolution calorimetry with the help of a high-temperature Calvet calorimeter. Dissolution experiments were performed in a lead metaborate (2PbO−B2O3) baths at 1173 K. The synthesis of the samples was realized by melting together pure silica, alumina, ferric oxide and calcium carbonate in appropriate ratios. The samples obtained in this way were examined by X-ray diffraction and scanning electronic microscopy. The free lime content was also determined by chemical analysis. The enthalpy of formation of silicates and aluminates obeys two different linear relations with respect to the ratio Ca/X (X=Al or/and Si) except for Ca12Al14O33 which does not exist in its pure form but has to be stabilized by anions as OH− or Cl−. The data corresponding to the two aluminosilicates are located between these lines. The enthalpy of formation of tricalcium silicate (Ca3SiO5 i.e. C3S according to the Bogue terminology) from dicalcium silicate and lime could be calculated as −6kJ·mol−1. This reaction is the most important one in the industrial process of clinkerization.
Abstract
The standard molar enthalpy of formation of crystalline di-isobutyldithiocarbamate complexes of P, As, Sb and Bi(III) has been derived by solution calorimetry at 298.15 K. The corresponding standard molar enthalpies of sublimation were estimated by means of differential scanning calorimetry. From the standard molar enthalpies of formation of the gaseous chelates the homolytic and heterolytic mean metal-sulphur bond-dissociation enthalpies were calculated.
Abstract
Traditionally, the kinetic treatment of adiabatic calorimetry data has been based on the results of one or more experiments, but always with the assumption of the kinetic model that the reaction follows to calculate the kinetic parameters. In this paper a method for the determination of the activation energy that uses a set of adiabatic calorimetry data is developed. To check the method, the thermal decompositions of two peroxides were studied.
Abstract
Thermodynamic investigations of Ga-GeSb0.855 section in the ternary system Ga-Ge-Sb, which is of a practical importance in electric-industry, are presented in this paper. Results of a comparative thermodynamic analysis at 1273 K obtained by Oelsen calorimetry and predicting methods - general solution model and Hajra's method are also given.
Abstract
Adsorption isotherms of n-butane on a granulated activated carbon were measured by two different but complementary experimental methods: calorimetry and gravimetry. Adsorption heats were determined in different ways. For the system studied, the experimental results prove that the adsorbent offers a homogeneous site distribution. Besides, there can be differences between the adsorption heat values which might come from the way they are obtained (by calculation or direct measurements).
Abstract
The enthalpies of mixing of liquid Gd-Si (17705 K) and Al-Gd (17605 K) alloys have been measured by high-temperature isoperibolic calorimetry. The calorimetric study of the gadolinium-based liquid alloys demonstrates the great negative enthalpies of mixing, which is associated with the contribution of GdSi and GdAl2 intermetallides into the liquid-state thermodynamics. The comparison of obtained results with literature data has been performed.
Abstract
High-temperature differential scanning calorimetry was used to investigate the thermodynamic parameters of the γ–β and β–α transitions in calcium pyrophosphate (Ca2P2O7). The measured enthalpy of transition compared well with previous results when higher heating rates (≥20 K min−1) were used. Recommendations for optimal use of HTDSC in high-temperature phase transition measurements are presented.
Abstract
Differential scanning calorimetry was used to study the stability of omeprazole in two forms: granules and powder. The drug was subjected to light, elevated temperature (40 and 60�C) and different pH values. The greatest alterations in stability were caused by pH, followed by light.
Study of solid state reactions in Nb/Al multilayer thin films
Differential scanning calorimetry
Abstract
Solid state reactions of sputter-deposited Nb/Al multilayer thin films, with periodicities in the range 10–333 nm, have been studied by differential scanning calorimetry. The first phase to form upon annealing the films in NbAl3. Constant-heating-rate calorimetric measurements show the presence of two peaks for the formation of this phase, while isothermal scans reveal that the first peak is associated with a nucleation and growth type transformation. The formation of NbAl3 is thus interpreted as a two-stage process of nucleation and growth to coalescence (first peak) followed by growth until the consumption of one or both reactants (second peak).
Abstract
The effect of phalloidin on the thermal stability of skeletal actin filaments polymerized from ADP-binding monomers was investigated with the method of differential scanning calorimetry. Phalloidin shifted the melting temperature of the ADP-F-actin from 59.1±1.0 to 80.0±1.2°C. The stabilizing effect of phalloidin propagated cooperatively along the filament. The cooperativity factor according to the applied model was 1.07±0.11. With these measurements it was possible to demonstrate that the binding of phalloidin has lower influence on the adjacent protomers in ADP- (k=1) than in ATP-actin filaments (k=3).
