Publications

Cathodic processes in Li 2 MoO 4 –K 2 MoO 4 –MoO 3 and K 2 MoO 4 –MoO 3 melts containing added UO 2 MoO 4 were investigated at 550–800 °C using cyclic voltammetry, cathodic polarization and bulk electrolysis. Cathodic reduction of molybdate melts (not containing uranium) resulted in formation of molybdenum dioxide. Products of the cathodic reactions in the melts containing uranium molybdate predominantly consisted of crystalline uranium oxides (mostly UO 2 and U 4 O 9 ) and MoO 2 . Minor products formed included other uranium oxides (U 3 O 8 , U 13 O 34 ), mixed uranium-molybdenum oxides (U 1.5 Mo 10 O 32 , Mo 2 UO 8 ) and molybdates (provisionally attributed to K 2 U(MoO 4 ) 3 ). Effect of temperature, cathodic current density 0.05–1 A cm −2 ), excess MoO 3 concentration (30–50 mol%) on the composition of the cathodic reaction products were analyzed. Oxygen-to-uranium atomic ratio (oxygen coefficient) for primary uranium oxide phases was determined and varied from 1.963 to 2.161 for UO 2±x and from 2.209 to 2.287 for U 4 O 9±y . The effect of the electrolysis regime on the composition of the cathodic product was also considered. Constant-current and constant-potential electrolysis, as well pulsed-current, pulsed-potential and pulsed-reversed-current electrolysis were investigated with varying the parameters of alternating pulses (duration, current density or potential). Chemical and phase composition of the products produced by bulk electrolysis was fully characterized.

No abstract is provided for this article.

Modern aerospace engineering relies on Al-based alloys with enhanced high-temperature strength properties and oxidation resistance. These requirements can be fulfilled by modifying alloys’ structure employing rare earths metal doping. Direct addition of metallic rare earths to aluminium is complicated due to high chemical activity of molten rare-earth metals and significant vapor pressure of aluminium at elevated temperatures. To overcome these drawbacks, lanthanide-containing master alloys with relatively low REE content can be employed instead of pure scandium. Currently there are three methods for preparing aluminium-based alloys containing rare earths, i.e. direct fusing, molten salt electrolysis and exchange or metallothermic reduction reactions. In the last case, Al–Gd and Al–Sc master alloy can be prepared by aluminothermic reduction of GdF 3 or ScF 3 in a molten binary NaF–KCl salt mixture at 800–1050 °С. In the present work we suggest the modification of the above mentioned method for aluminium–cerium and aluminium–neodymium master alloy production with a lanthanide concentration of 1 to 7 wt. %. Based on thermodynamic calculations we proposed that the high-temperature exchange reaction between metallic aluminum and corresponding fluoride containing salt electrolyte should be carried out at temperatures from 740 to 780 ° C to provide the higher recovery of REE. The influence of the time of the exchange reaction and «aluminium–salt» ratio on the process to obtain ligatures of various compositions is analyzed. The yield higher than 85 % is achieved. The microstructure of the alloys represents a metal matrix of aluminum in which intermetallic compounds of Ln 3 Al 11 compositions are distributed In the case of an exchange reaction between aluminum and cerium fluoride, the formation of a new phase, presumably related to the Al 4 Ce intermetallic compound, is found.

Corrosion resistance of such ceramic materials as BN, Si3N4, YSZ (yttria stabilized zirconia) was studied in fused KCl–LiCl mixtures containing 8 wt. % UCl3. The rate and the mechanism of the corrosion of the materials studied were determined. The processes taking place during the interaction between perspective materials and the melt were investigated.

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

No abstract is provided for this article.

The phase stability of nickel-based solid solution VDM® Alloy C-4 was studied, and time-temperature-precipitation diagram was built. The processes of heat treatment of sheets and tubes made of VDM® Alloy C-4 were investigated. The following regime of heat treatment was chosen – annealing at 1100 °C for 10 min/mm thickness with further rapid cooling in air. It was also shown that the cooling rate should be higher than 0.1 °С/s to prevent sigma-phase formation along the grain boundaries.

In situ EXAFS spectroscopic studies of uranium compounds in high temperature alkali chloride melts indicate the presence of oligomeric species. An investigation into UCl(3) and UCl(4) dissolved in LiCl reveals long range ordering of uranium atoms in the molten state which is not maintained on quenching. Studies of uranium dioxide dissolved in LiCl-KCl eutectic with HCl exhibit long range ordering in both molten and quenched states, and the EXAFS data can be modeled using multiple coordination shells.