First-Eutectic Features of Polar Metals in Double Systems

It is known that the dense part of any liquid metal consists of ramified clusters of almost regular tetrahedrons (triangular pyramids with atoms in their vertexes) that are connected into chains by faces. Any metal additive as a second component of liquid alloy can be both beyond these clusters as separated atoms and into them as inherent clusters. The liquid-metal alloy transfers into the second state, at the first eutectic of the solvent. This polymorphic transition of liquid matrix is discovered in the systems, Pb-K and Na-Pb, by molecular-dynamic simulating their microstructure and in experiments on scattering slow neutrons by these alloys of different compositions. In the first system, the obtained results identify both the homogeneous alloy at low concentrations of potassium in liquid lead and the alloy clustering, (Pb4K)n, at potassium concentrations following the eutectic, Pb0.91K0.09. In the second one at the concentrations of lead more than 2%, just the second state is discovered with the clusters, (Na4Pb)n. One can expect the same polymorphic transition in the eutectic, Na0.93Tl0.07, with the micro-inhomogeneity, (Na6Tl)n, and with the melting point of 64 C. This eutectic maintained by the oxygen-free technology and enriched by the isotope, 205Tl, can become the best coolant for fast nuclear reactors due to the depressed chemical activity of sodium and composition stability.

On Diffusive Confining a Galvanic Crystallization out of Molten Salts

The electron-energy band structure of electric Double Layer (DL) between a molten salt and metal electrode (an anode or cathode) is studied for the electrodepositing crystallization process when the width of DL metal part is less than the one in the molten salt. It is shown that just the molten-salt part of the double layer confines a rate of electrodepositing process. The reason of this is a neutralization of depositing ions into the molten-salt near the electrode and hence their diffusively confined motion in a density gradient field. It is important to minimize the electrodepositing potential for effective component crystallization out of the molten salt and its exchange process including selective extracting of salt components by their crystallization on electrodes of galvanic circuit. It is shown that this can be carried out by means of fine and controllable variation of reduction-oxidation (RedOx) potential of the non-stoichiometric salts. A possible application of a potentiometer for monitoring and managing the salt composition is considered. For this, one uses precise methods of electric-motion-force and coulometer titration by solid electrolyte(for example, M+–β ”–Al2O3) of the basic salt metal (M。) as a reduction agent in the molten-salt solution.

MD Simulated Microstructure of Liquid Sodium Alloyed with Lead

The results of molecular-dynamics (MD) simulation are obtained for structural and thermodynamic properties of the molten system, Na1-xPbx (x ≤ 0.1), at 698 K in the model of nearly free electronic gas (NFE approximation). The all numerical experiments are carried out by unified procedure: 1) equilibrating the MD cell 1 ps;2) calculating partial radial distribution functions gab(r) in 1, 5, and 10 ps;3) data handling for calculating other characteristics. It follows from this that lead impurity in liquid sodium at concentration in the range of 1% - 10% is characterized by micro-heterogenetic structure in the form of cluster compounds with variable composition. Just therefore the sodium alloys, Na-MIV, with four-group elements of Periodic table have no eutectic in this range of additive concentrations. This eutectic is needed for modifying sodium coolant of the fast nuclear reactor. Therefore it is reasonable to find an alternative alloy of sodium with additive from adjacent groups which has a eutectic in this range of concentrations, for example, the eutectic, Na0.929Tl0.071, with melting point of 64°C. The modified sodium coolant by isotope, 205Tl, can appear attractive for inhibiting the chemical activity of sodium just as the lead alloyed one.