Abstract
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.
Highlights
The liquid alkali metals and heavy metals are always characterized by existence of chemical compound clusters in their alloys [1] [2]
It turned out that one can describe the liquidus near the first eutectic of the solvent in double systems of polar liquid metals as a solidification of two solutions on both branches of this eutectic respectively
The introduction solution is homogeneous and impurity atoms turn out introduced into the liquid matrix of the solvent
Summary
The liquid alkali metals and heavy metals are always characterized by existence of chemical compound clusters in their alloys [1] [2]. The first gives away electron (Na+) while the second accepts it (Pb−) and serves as an oxidizer in liquid sodium If unifying their contrasts in the alloy after the first eutectic, we will obtain the liquid-metal coolant with components that fulfill differing technological functions: sodium provides the low corrosion activity of the eutectic and lead in the colloidal form inhibits the chemical activity of sodium right up to automatic shut-down its fire outdoors [3] [4]. Some aspects of forming the colloidal alloy remain not quite understood and they require the analysis of phase diagrams in the neighborhood of the first eutectic of solvent This knowledge can be useful for choosing the optimal eutectic modification of the sodium coolant for the fast nuclear reactors. One can verify the model of clustering the second component in the first eutectic of the basic component (solvent) by such analysis
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