Liquid Alkali Metals Research Articles

Phase Behavior and Atomic Dynamics in RbxNa1-x: Insights from Machine Learning Interatomic Potentials based on Ab Initio Molecular Dynamics.

Liquid alkali metal alloys have garnered significant attention because of their potential applications in coolant systems and batteries, driven by the need for environmental conservation and technological development. However, research on these complex systems is limited, necessitating a deeper understanding to ensure their safe and effective utilization. This study presents a comprehensive investigation of the factors that determine the phase diagram of RbxNa1-x. By reproducing the experimental results using the thermodynamic integration method and machine learning interatomic potentials based on ab initio molecular dynamics simulations, we uncovered the delicate balance between the energy and entropy contributions that influence the phase stability of these liquid metal alloys. Further analysis of the liquid phase revealed the crucial roles of volume and atomic mass. Additionally, the coordination numbers of the atoms revealed distinct clustering behaviors, where Na atoms tended to avoid proximity to other Na atoms, whereas Rb atoms exhibited a strong tendency to cluster together. Moreover, the diffusion dynamics further illustrated the asymmetry in the behavior of Rb and Na, with Rb showing increased diffusion at higher concentrations and Na exhibiting higher diffusion at lower concentrations. These findings offer significant insights into the phase stability and the dynamic and structural properties of these complex liquid metal alloys.

Prediction of Viscosity of Liquid Alkali Metals Using an Improved Mean Spherical Approximation

Prediction of Viscosity of Liquid Alkali Metals Using an Improved Mean Spherical Approximation

Enhancing strength and ductility of Nb alloy via Y addition by vacuum electromagnetic levitation melting under oxygen carrier route

Niobium (Nb) is considered as candidate material for heat pipe in space nuclear reactors due to high melting point, low density, excellent compatibility with alkali liquid metals, irradiation resistance, workability and welding performance, but low strength restricts it's engineering application. In this work, yttrium (Y) was introduced into Nb matrix to achieve solution strengthening from Y atoms and dispersion strengthening from yttrium oxides. The latter one was realized by oxygen carrier route and vacuum electromagnetic levitation melting technique. Finally, one Nb521 (Nb-5.0 wt%W-1.7 wt%Mo-1.0 wt%Zr-0.07 wt%C) and four kinds of Nb521-xY (x = 0.1, 0.2 0.3 and 0.4 wt%) alloys were prepared. TEM characterization indicated that 80 nm Y2O3 particles were formed in Nb521-0.1Y, which exhibited the highest yield strength of 673 MPa, ultimate tensile strength of 740 MPa as well as larger elongation of 12.8%. Moreover, the solution strengthening of Y atoms and Orowan strengthening of yttrium oxides were evaluated quantitatively.

Henry's constant of helium in liquid alkali metals

The determination of the solubility of helium in liquid lithium and in lead-lithium eutectic systems is of crucial importance for the assessment of the reliability, safety and efficiency of future nuclear reactor plants based on fusion technology. In this way, an important aspect to be considered concerns the possibility of accumulations of gas inside the so called breeding blankets of the reactors, due to the low solubility of helium, leading to potentially undesired effects. In the present work we have performed molecular dynamics simulations in order to examine the characteristics of the solubility of helium in alkali metals along a temperature interval that covers near ambient conditions up to temperatures of the order of a 1000 K. Our methodology relied on the classical Kirkwood perturbative approach, which involves the gradual coupling between the infinite diluted He atom and the solvent. Such insertion proceeds along three stages that involved a previous incorporation of a softly interacting cavity that prevented singularities due to the harshly repulsive nature of the actual He-Li potential. Simulated structure factors predicted by the force fields of the different alkali metals were found to be in excellent agreement with available experimental information. Moreover, at all thermal conditions, our results of Henry's constants predict a steady volatility reduction with increasing temperatures, in good agreement with available experimental data. Furthermore, Henry's law volatility constants increase as the sizes of the atoms of the host alkali metals become more comparable to the size of the He atom (the predicted solubility increases with the size of the alkali atoms), and are coherent with the scarce experimental data available.

The SAFT-VR Morse equation of state for liquid alkali metals

The SAFT-VR Morse equation of state for liquid alkali metals

Design and Analyses of Miniature, Submersible Annular Linear Induction Pump for Test Loops Supporting Development of Advanced Nuclear Reactors

A submersible annular linear induction pump (ALIP) design with an outer diameter of 66.8 mm with appropriate materials is developed for circulating molten lead and alkali liquid metals of sodium and sodium-potassium-78 (NaK-78) alloy in test loops at temperatures up to 500°C. These loops investigate the compatibility of these liquid coolants with nuclear fuel and structure materials to support the development of advanced, Generation IV nuclear reactors. The present ALIP, which employs high-temperature ceramic-insulated coil wires and Hiperco-50 center core and stators, fits in Type 316 stainless steel, 2.5-in. standard schedule 5 pipe. This pipe, considered for the riser tube of the Versatile Test Reactor (VTR) in-pile test cartridge loop, has an inner diameter of 68.8 mm permitting 1.0-mm radial clearance for the present ALIP. An improved equivalent circuit model (ECM) is developed to analyze the performance of the present ALIP design. The accuracy of the model predictions is successfully validated using reported experimental measurements by other investigators for a low liquid sodium flow ALIP at 200°C and 330°C. The improved ECM calculates the performance characteristics of the present ALIP design and investigates the effects of varying the terminal voltage, current frequency, winding wire diameter, center core length, width of the liquid flow annulus, and working fluid properties and temperature on the pump operation. For circulating molten lead, the calculated peak efficiency of the present ALIP design of 6.7% occurs at a flow rate of 9.5 kg/s and pumping pressure of 263 kPa. The calculated peak efficiency for circulating liquid sodium is much higher, 26.3%, and occurs at a lower flow rate of 2.2 kg/s but a higher pumping pressure of 364 kPa. The calculated peak efficiency for circulating NaK-78 (23%) is lower than for sodium and occurs at a lower flow rate and pumping pressure of 1.9 kg/s and 310 kPa, respectively.

Magnetohydrodynamic Analyses of a Miniature, Dual-Stage Electromagnetic Pump for Lead and Sodium In-Pile Test Loops

To support the development of Generation IV nuclear reactors, in-pile and out-of-pile test loops with miniature, submersible Direct-Current Electromagnetic Pumps (DC-EMPs) are used to investigate compatibility and corrosion issues of nuclear fuel and structure materials with flowing molten lead and alkali liquid metals. Owing to the absence of detailed experimental measurements and because of its simplicity and low computational cost, the Equivalent Circuit Model (ECM) is widely used to predict the pump characteristics. The simplifying assumptions in the ECM contribute to overpredicting the pump characteristics by >10%. To gain insight into the pump operation and assess the effect of various assumptions in ECM, not possible even experimentally, this work performed three-dimensional (3-D), Magneto-Hydro-Dynamic (MHD) analyses of a 66.8-mm-diameter, submersible, dual-stage DC-EMP, recently developed by the authors, for circulating molten Pb and liquid Na at up to 500°C. The solution of the coupled electromagnetism equations and the momentum and energy balance equations calculates the pump characteristics and provides 3-D images of the flow, electric current, and magnetic field strength distributions in the flow duct. The Grid Convergence Index (GCI) criterion confirmed the adequacy of the employed numerical mesh refinement and the results conversion. Results demonstrate strong dependence of the magnetic field strength distribution in the flow duct on the value and the distribution of the electric current but negligible effects of the fluid temperature on joule heating and pump characteristics. The Lorentz force highest densities occur at the entrance of the two pumping stages, and approximately 10.0% of the total force occurs in the fringe regions upstream and downstream of pumping stages. The MHD pump characteristics are in general agreement with, but consistently lower than, the ECM predictions. For molten lead and liquid sodium, the difference between the calculated characteristics increases with increased flow rate and input current, up to 12% and 14%, respectively.

Thermodynamic Quantities of Morse Fluids in the Supercritical Region

The critical point parameters for liquid alkali metals (sodium and potassium) are calculated accounting for the non-Gaussian order parameter fluctuations and the Morse interaction potential. The behavior of the isothermal compressibility, density fluctuations, and thermal expansion for sodium is studied in the supercritical temperature region. A significant increase in the isothermal compressibility and the density fluctuations near the critical point indicates a substantial density sensitivity to tiny pressure fluctuations. The thermal expansion coefficient for various fixed pressure values shows a typical gas decrease with increasing supercritical temperature. The Widom line separating the gaseous and liquid structures of the fluid at temperatures above the critical one is represented. Note that our calculations are valid in a small neighborhood of the critical point, which is problematic for theoretical and experimental studies.

Molecular hydrodynamic theory of the velocity autocorrelation function.

The velocity autocorrelation function (VACF) encapsulates extensive information about a fluid's molecular-structural and hydrodynamic properties. We address the following fundamental question: How well can a purely hydrodynamic description recover the molecular features of a fluid as exhibited by the VACF? To this end, we formulate a bona fide hydrodynamic theory of the tagged-particle VACF for simple fluids. Our approach is distinguished from previous efforts in two key ways: collective hydrodynamic modes and tagged-particle self-motion are modeled by linear hydrodynamic equations; the fluid's spatial velocity power spectrum is identified as a necessary initial condition for the momentum current correlation. This formulation leads to a natural physical interpretation of the VACF as a superposition of products of quasinormal hydrodynamic modes weighted commensurately with the spatial velocity power spectrum, the latter of which appears to physically bridge continuum hydrodynamical behavior and discrete-particle kinetics. The methodology yields VACF calculations quantitatively on par with existing approaches for liquid noble gases and alkali metals. Furthermore, we obtain a new, hydrodynamic form of the self-intermediate scattering function whose description has been extended to low densities where the Schmidt number is of order unity; various calculations are performed for gaseous and supercritical argon to support the general validity of the theory. Excellent quantitative agreement is obtained with recent MD calculations for a dense supercritical Lennard-Jones fluid.

Theoretical investigation on the structural and vibrational properties of some alkali liquid metals: A pseudopotential approach

Along with a few elastic constants, a recently created pseudopotential is employed to examine the vibrational properties of some simple alkali metals, i.e. Li, Na, K, Rb and Cs. The phonon dispersion curves (PDC) are computed in the text. (ωL and ωT), longitudinal sound velocity (vl), transverse sound velocity (vt), isothermal bulk modulus (B), modulus of rigidity (G), Young’s modulus (Y ), Debye temperature (θD) of some liquid alkali metals. The second order technique used in the current work, using Hubbard and Beeby (HB) equations, is based on pseudopotential theory. The various Percus-Yevick hard sphere (PYHS) and one-component plasma (OCP) structure factors used in the current investigation are used to construct the pair correlation function g(r). The current paper makes use of three distinct forms of local field correction functions developed by Hartree (H), Taylor (T), and Nagy (N). The current findings are found to qualitatively agree with the experimental and theoretical data that is currently available.

Membrane‐Free Alkali Metal‐Iodide Battery with a Molten Salt

Batteries with liquid metal electrodes are attractive candidates for sustainable energy‐storage applications due to low manufacturing cost and high recyclability. These batteries should be developed for lower operating temperature, higher cell voltage, and membrane‐free cell configuration. Herein, a new type of a membrane‐free cell relying on liquid alkali metals and iodide is demonstrated. As a proof‐of‐concept study, membrane‐free alkali metal‐iodide (A‐AI) batteries are constructed by a facile cell assembly introducing current collectors, LiI–LiCl–KI–CsI salt mixture, and an insulator without relying on solid‐state mediums for separating electrolytes. For the initial assembly, no active electrode materials are required since they are naturally formed during battery operation. Despite the unoptimized cell construction, the membrane‐free A‐AI batteries show promising electrochemical performance such as a reliable stability for 250 cycles. The cells are able to handle a high current density and show a relatively low self‐discharge rate, which implies the possibility of an iodine‐concentrated layer at the bottom of the cell. This is further supported by postmortem analyses using neutron radiography. X‐ray photoemission spectroscopy is performed to identify the changes in the iodine concentration in the cell.

Study into the physical chemistry and technology of alkali liquid metal coolants for nuclear and thermonuclear power plants

It is shown that, as the result of developing alkali liquid metal coolants, including sodium, eutectic sodium-potassium alloy, lithium and cesium, the scientific basis has been established for their application in nuclear power. The paper presents data from investigations of thermophysical, neutronic and physicochemical properties and characteristics of various alkali liquid metal coolants, the content of solid-phase and dissolved impurities in coolants, mass transport of impurities in circulation circuits with alkali liquid metal coolants, development of systems for removal of impurities, and control of the content of impurities in alkali liquid metal coolants. Alkali liquid metal coolants are considered as a part of a system that includes a structural material in contact with the coolant, and a gas space that compensates for the thermal expansion of the coolant. The state of the system is defined by the physicochemical properties of the system’s components. And the coolant and the structural materials also represent subsystems consisting of a base material, a coolant and impurities contained both in the material and in the coolant. It has been shown that each alkali liquid metal coolant has its own set of impurities that define its technology. It depends on the physicochemical properties of the solution of the structural material impurities and components in the coolant. Objectives have been formulated for investigating further alkali liquid metal coolants, as stemming from the need to improve the efficiency, environmental friendliness, reliability and safety, and for extending the life of nuclear power plants in operation or under design. Alkali liquid metals are promising candidate materials for being used in thermonuclear power not only as the coolant but also as the tritium breeding medium. These include, first of all, lithium and its eutectic alloy with lead (17 at. % of lithium). The possibility for using lithium or a lithium-lead alloy as a coolant in the blanket of the international thermonuclear power reactor is compared.

Criticality points on the phase diagram of substances as scaling parameters in the law of corresponding states: alkali metals

The law of corresponding states (LCS), based on a generalized van der Waals equation of state (gvdWEoS) has been formulated by rescaling its thermodynamic variables with liquid- vapour critical—point parameters, the spinodal, the thermodynamic limit of superheat (TLS) and the supercritical (SC) point. This gvdWEoS differs from the known van der Waals equation of state (vdWEoS) by the modified attractive term. The scaling properties have been derived on the basis of the gvdWEoS. The expressions for the isothermal compressibility, a derivate of Gibbs free energy, have been derived. In all the cases of rescaling, the gvdWEoS has the similar functional form and the expression for isothermal compressibility has a similar functional form. This shows that the parameters of any spinodal-point on the phase diagram, including the TLS as a particular case, and the SC point, characteristic point on the quasispinodal, provide the alternate scales of parameterizing the thermodynamic properties of substances other than the liquid-vapour critical point. Moreover, an isothermal compressibility regularity is formulated on the basis of the gvdWEoS and it is found to satisfactorily trace the literature data for saturated liquid alkali metals.

Research on precise and stable seed flow delivery control for plasma MHD power generation

In this paper, a technique for precise and stable delivery control of alkali metal seed flow is proposed and experimentally verified. A high-pressure syringe driven by a stepping motor delivers liquid alkali metal seeds through a pneumatic atomizing spray gun. The seed jet is uniformly mixed, heated, vaporized and ionized by the high-temperature main flow in the plasma generator to produce a plasma with high conductivity. Based on the high-temperature arc wind tunnel test platform, an experimental study of the alkali metal cesium seed flow measure and plasma ionization characteristics was carried out. The results show that the fluctuation range of the measured seed flow was 5.93-10.39% at a small flow rate of 19 mL/min. For the back pressure of 6 atm, the fluctuation range of the measured seed flow is 6.04-11.55%, which proves that the back pressure of the plasma generator has insignificant effect on the seed flow. The plasma ionization characteristics test shows that the conductivity of the argon cesium equilibrium plasma is between 26.93-31.69 S/m, indicating that the ionization characteristics of the plasma are relatively stable, which can indirectly prove that the seed system has a precise and stable flow rate during the actual power generation. Key words: MHD power generation, alkali metal seed, seed fraction, precise and stable injection. Tables 1, Figs 9, Refs 11.

Minimally Invasive Injectable Thermochemical Ablation Therapy of Malignant Tumor via Alkali Metal Fluid

In recent years, with the increasing occurrence of various malignant tumors throughout the world, cancer disease has become a major threat to human life and health care. So far, many classical tumor treatment methods such as surgical removal, radiotherapy, and chemotherapy still appear somewhat traumatic to the human body and may face tough issues when tackling advanced tumors or those with complex growth behaviors. In this regard, local tumor ablation technologies receive more and more attention owing to their minimally invasive feature and targeted treatment output. Among the many endeavors ever made, thermochemical ablation therapy, as a combination of physical treatment and chemical ablation, displays the outstanding characteristics of straightforward surgical administration at rather a low cost. As a unique representation, liquid alkali metals are recognized as a highly suitable thermochemical ablative agent for such practices due to their truly minimally invasive injectability, precise targeting, and nearly harmless residues. This article is dedicated to presenting an overview of the advancement of liquid alkali metals-based tumor ablation. The main contents would include but are not limited to the characteristics, therapeutic principles, tumor ablation effects, dosage administration, and damage of liquid alkali metals thus caused. For illustration, several typical applications of liquid alkali metal in tumor ablation therapy were also discussed. With the continuous development of fundamental research and technological endeavor, the liquid alkali metal is expected to become a powerful tool for minimally invasive ablation of malignant tumors in the coming time.

Electrochemical Reduction of La2O3, Nd2O3, and CeO2 in LiCl-Li2O Melt.

The reduction of pellets composed of individual CeO2, Nd2O3 and a La2O3-Nd2O3-CeO2 mixture by lithium extracted on a cathode during lithium chloride electrolysis at 650 °C was studied. The methods of cyclic voltammetry, electron microscopy, including determination of the elemental composition of the studied objects, and X-ray diffraction analysis were applied for the present study. The reduction degree of rare-earth metal (REM) oxides was determined using both the bromine method and reduction melting of the samples in the graphite crucible. The formation of the metallic phase composed of the rare-earth elements (REEs) was not observed even at the cathode potentials, corresponding to the formation of the liquid alkali metal phase, and lithium extraction, which, in the quantitative ratio, exceeds greatly the values needed for the reduction reaction. CeO2 was found to reduce to Ce2O3.

Evolving Machine Learning Methods for Density Estimation of Liquid Alkali Metals over the Wide Ranges

Alkali metals are widely used as industrial materials in products such as electrochemical cells because of their properties that make them suited to high temperatures. In this study, three computational approaches including gene expression programming (GEP), least squares support vector machine (LSSVM), and adaptive neuro fuzzy inference system (ANFIS) have been suggested to estimate density of different liquid alkali metals in extensive ranges of pressure and temperature. An experimental databank involving 595 experimental alkali metals’ densities has been gathered to prepare and test the models. The mathematical and visual comparisons of these models’ outputs and real density values are used to assess capacities of GEP, LSSVM, and ANFIS models in prediction of alkali metals’ density. The determined R-squared values for GEP, LSSVM, and ANFIS are 0.9999, 1, and 1, respectively. The MSE values are estimated to be 0.9184, 0.815, and 0.154 for GEP, ANFIS, and LSSVM, respectively. According to these results, these models can be suggested as simple and accurate ways for determining alkali metals’ properties. Results showed that LSSVM has the best performance in comparison with GEP and ANFIS. Moreover, the parametric analysis of input parameters is carried out to show the impact of them on alkali metals’ density. According to this analysis, the amount of lithium can be the most effective parameter on the mixture density.

Room temperature liquid metals for flexible alkali metal-chalcogen batteries.

Flexibility has become a certain trend in the development of secondary batteries to meet the requirements of wide portability and applicability. On account of their intrinsic high energy density, flexible alkali metal-chalcogen batteries are attracting increasing interest. Although great advances have been made in promoting the electrochemical performance of metal-S or metal-Se batteries, explorations on flexible chalcogen-based batteries are still limited. Extensive and rational use of soft materials for electrodes is the main bottleneck. The re-emergence of safe liquid metals (LMs), which provide an ideal combination of metallic and fluidic properties at room temperature, offers a fascinating paradigm for constructing flexible chalcogen batteries. They may provide dendrite-free anodes and restrain the dissolution of polysulfides and polyselenides for cathodes. From this perspective, we elaborate on the appealing features of LMs for the construction of flexible metal-chalcogen batteries. Recent advances on LM-based battery are discussed, covering novel liquid alkali metals as anodes and LM-sulfur hybrids as cathodes, with the focus placed on durable high-energy-density output and self-healing flexible capability. At last, perspectives are proposed on the future development of LM-based chalcogen batteries, and the viable strategies to meet the current challenges that are obstructing more practical flexible chalcogen batteries.

On the question of the applicability of the principle of thermodynamic similarity in liquid alkali metals

In this paper, we have created an interparticle interaction potential for liquid alkali metals using ab-initio simulations and machine learning. The resulting family of potentials was tested by molecular dynamics simulation, in which the liquid metals were heated to the melting point and the resulting system was then averaged. The simulation results show that near the melting point, the radial distribution function and the static structure factor are reproduced. This results indicates that the principle of corresponding states is fulfilled in liquid alkali metals.

Erratum: Self-diffusion coefficients of liquid alkali metals described by the square-well model within the mean spherical approximation

Erratum to the paper “Self-diffusion coefficients of liquid alkali metals described by the square-well model within the mean spherical approximation” (Indian J. Pure&Appl. Phys., 2015, v. 53, p. 392-394)