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- Author or Editor: V. Fedorov x
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Abstract
A measuring complex with certified neutron flux units and variable neutron energies, a fast neutron spectrometer and radiometric device have been developed for the study of spontaneous fission of actinide elements.
Abstract
Dehydration processes of series of rhenium cluster compounds were studied (by thermogravimetry, differential scanning calorimetry, dilatometry methods). Cluster anions of compounds are [Re6S8Br6]3−, [Re6S7Br7]3−, [Re6S8(OH)6]4−, [Re6Se8(OH)6]4−. TG- and DSC-data were used for kinetic studies, these data were processed using special computer program with ‘model-free’ approach. Quantitative data on thermodynamic and kinetic stability of compounds are obtained. The role of water molecules in the cluster compounds stability is discussed.
DTA and TG methods were used to study the melting, polymorphic transformation and thermal decomposition processes of alkali metal and ammonium mixed bifluorides formed by mutual replacement of the cations in the crystal lattice. We studied the structural features and the characteristics in the changes of thermal properties of individual compounds, solid solutions with unlimited solubility and solid solutions with limited solubility.
A simple method has been proposed to achieve reliable thermostatic control of the oven of the Derivatograph by applying a calibrated stabilized voltage to the heater to compensate heat losses.
The thermal stability of alkaline earth metal hydrofluorides was studied by means of a Derivatograph. The values of the activation energy, reaction order and rate constant were determined. The comparison of the kinetic parameters of the decomposition process for the complete series of hydrofluorides studied led to a certain regularity in the differences in their thermal stabilities and its correlation with the strength of the hydrogen bond in their structure.
Abstract
Extraction of 0.05–0.25M uranyl nitrate into 30% tributyl phosphate (TBP) in dodecane from nitric acid solutions of thorium nitrate at equilibrium with its salt has been studied. Under investigated conditions a third (second organic) phase is formed. As the heavy organic phase extracts uranium, the calculated ratio of TBP to thorium and uranium sum decreases from 2.7 to less than 7. Electronic spectra show that in heavy organic phase approximately 80% of uranium is found as trinitrate complex, while in the light organic phase this complex is not detected. The measurements of dielectric constant (
) of the heavy phase reveal a frequency dependence of . The data obtained point to the existence of an ordered structure in the heavy organic phase.
The thermal stability and non-isothermal kinetics of the decomposition of alkali metal bifluorides were studied using a derivatograph. The removal of hydrogen fluoride from LiF · HF and NaF · HF takes place before melting and their decomposition occurs in a single stage; however, potassium, rubidium and cesium bifluorides at first undergo polymorphous transformation and melting on heating, and their decomposition proceeds stepwise. The thermal stability of alkali metal bifluorides has been found to increase with increasing ionic radius of the cation, reflecting its correlation with the hydrogen bond strength in these compounds.
Data are presented on the properties of alkali metal and alkaline earth hydrofluorides. Melting, thermal decomposition and interaction of hydrofluorides with various classes of inorganic substances are discussed. Some regularities of changes in thermal properties within the sequences of the above hydrofluorides are established. Future directions of research in this field are outlined.
