Dmitry S. Maltsev

Combined Approach for the Structural Characterization of Alkali Fluoroscandates: Solid-State NMR, Powder X-ray Diffraction, and Density Functional Theory Calculations

The structures of several fluoroscandate compounds are presented here using a characterization approach combining powder X-ray diffraction and solid-state NMR. The structure of K5Sc3F14 was fully determined from Rietveld refinement performed on powder X-ray diffraction data. Moreover, the local structures of NaScF4, Li3ScF6, KSc2F7, and Na3ScF6 compounds were studied in detail from solid-state 19F and 45Sc NMR experiments. The 45Sc chemical shift ranges for six- and seven-coordinated scandium environments were defined. The 19F chemical shift ranges for bridging and terminal fluorine atoms were also determined. First-principles calculations of the 19F and 45Sc NMR parameters were carried out using plane-wave basis sets and periodic boundary conditions (CASTEP), and the results were compared with the experimental data. A good agreement between the calculated shielding constants and experimental chemical shifts was obtained. This demonstrates the good potential of computational methods in spectroscopic assignments of solid-state 45Sc NMR spectroscopy.

Thermodynamic properties of gadolinium in Ga–Sn and Ga–Zn eutectic based alloys

Thermodynamic properties of gadolinium in Ga–Sn and Ga–Zn eutectic based alloys were studied. Temperature dependences of gadolinium activity in the studied alloys were determined at 573–1073 K employing the EMF method. Solubility of gadolinium in the Ga–Sn and Ga–Zn alloys was measured at 462–1073 K using IMCs sedimentation method. Activity coefficients as well as partial and excess thermodynamic functions of gadolinium in the studied alloys were calculated on the basis of the obtained experimental data.

Thermodynamic properties of rare earth elements in La–RE–Ga–In alloys (RE = Nd, Y)

Thermodynamic properties of La, Nd, and Y were studied in pseudo-quaternary systems La–Nd–(Ga–In)eut and La–Y–(Ga–In)eut. Temperature dependences of lanthanum, neodymium, and yttrium activity in the alloys were determined at 300–800 °C employing the e.m.f. method. Partial thermodynamic functions of lanthanum in the alloys studied were calculated on the basis of the experimental data.

Electrode potentials of uranium in the LiCl–KCl–CsCl eutectic melt

The electrode potentials of uranium in the melt of the eutectic mixture of lithium, potassium, and cesium chlorides are measured in the temperature range 573–1073 K. Formal standard potentials EU*(III)/U and the main thermodynamic characteristics of uranium trichloride in the LiCl–KCl–CsCl melt are calculated, and the electronic absorption spectra of UCl63– ions are measured.

Uranium and neodymium partitioning in alkali chloride melts using low-melting gallium-based alloys

Abstract Partitioning of uranium and neodymium was studied in a ‘molten chloride salt - liquid Ga-X (X = In or Sn) alloy’ system. Chloride melts were based on the low-melting ternary LiCl-KCl-CsCl eutectic. Nd/U separation factors were calculated from the thermodynamic data as well as determined experimentally. Separation of uranium and neodymium was studied using reductive extraction with neodymium acting as a reducing agent. Efficient partitioning of lanthanides (Nd) and actinides (U), simulating fission products and fissile materials in irradiated nuclear fuels, was achieved in a single stage process. The experimentally observed Nd/U separation factor valued up to 106, depending on the conditions.

Study of uranium solubility in gallium-indium eutectic alloy by emf method

Activity, activity coefficients and solubility of uranium in Ga-In eutectic alloy as well as activity of uranium in U-Ga and U-In alloys were determined between 573 and 1073 K using electromotive force (emf) method.

The interaction of scandium fluoride with alkali metal fluorides

Series of alkali metal fluoroscandiates were prepared by reacting corresponding individual alkali fluorides MeF and ScF3 (were Me was Li, Na, K, Rb, Cs) at 400–600 °C for 100 h under argon atmosphere. The Me : Sc ratio varied from 1 : 1 to 3 : 1. X-ray powder diffraction analysis showed that the following phases were formed: Li3ScF6, Na3ScF6, NaScF4, K3ScF6, KSc2F7, Rb3ScF6, Cs3ScF6, CsScF4.

Redox potentials of uranium in molten eutectic mixture of lithium, potassium, and cesium chlorides

The behavior of uranium(III) and (IV) ions in the melts based on the eutectic mixture of lithium, potassium, and cesium chlorides has been studied using cyclic voltammetry in the range of 573–1073 K. The red-ox potentials of uranium have been determined and formal standard EU(III)/U(IV)* red-ox potentials have been calculated.

Diffusion coefficients of the uranium(III) and (IV) ions in the LiCl–KCl–CsCl eutectic melt

Diffusion coefficients of the uranium(III) and (IV) ions in the eutectic melt of the lithium, potassium, and cesium chlorides in the temperature range of 573–1073 K have been determined using two independent methods: cyclic voltammetry and chronopotentiometry.