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  • Author or Editor: V. E. Fedorov x
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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.

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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.

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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.

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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.

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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.

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Journal of Thermal Analysis and Calorimetry
Authors: A. V. Nikolaev, A. A. Opalovsky, V. E. Fedorov, and T. D. Fedotova

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.

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Abstract  

Acid Zr salt of dibutyl phosphoric acid (ZS HDBP) dissolved in 30% TBP with isoparaffines was investigated and successfully tested on “hot” rigs as TBP-compatible solvents for TPE and RE recovery from simulated and real HLW, containing 1–3 mol/L HNO3, and for their partitioning with DTPA in formic media. Mo was also separated. The possibility of the use of 1–1.5 mol/L HDBP solutions in meta-nitrobenzotrifluoride (F-3) for these purposes is demonstrated as well. Addition of chlorinated cobalt dicarbollide (CCD) to ZS HDBP solution in F-3 gives rise to synergetic effect during extraction and, in combination with PEG, allows to extract Cs and Sr along with TPE and RE from HLW of mentioned acidity, and to separate the elements to fractions by their valence.

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