Liquid Metal Systems Research Articles

Atomic Dispersion via High‐Entropy Liquid Metal Alloys

Gallium‐based liquid metal alloys exhibit unconventional and intriguing properties as metallic solvents, demonstrating an exceptional potential to dissolve and reconfigure a vast array of elements within the liquid metal matrix. Leveraging on these distinctive characteristics of gallium‐based alloys, the synthesis of high‐entropy liquid metal alloys (HELMAs) in low dimensions is reported. The nanoscale HELMAs offer advantages including the solvation of multiple metallic elements at room temperature, while promoting their atomic dispersion at elevated concentrations. Entropy estimations for HELMAs surpass those of high‐temperature molten metals, leading to the realization of high‐entropy liquid metal systems at room temperature. Through a proof‐of‐concept hydrogen evolution reaction comparison, the potential of these HELMAs in enhancing the activities of nanocatalysts is demonstrated. In this case, atomic dispersion of Pt is shown in senary GaIn‐AuCuPtPd HELMA, contrasting with lower entropy systems in which Pt forms discernible clusters. These presented features can lead to catalytic systems with enhanced and tailored activities.

Exploring Challenging Properties of Liquid Metallic Systems through Machine Learning: Liquid La and Li4Pb Systems.

In this machine learning (ML) study, we delved into the unique properties of liquid lanthanum and the Li4Pb alloy, revealing some unexpected features and also firmly establishing some of the debated characteristics. Leveraging interatomic potentials derived from ab initio calculations, our investigation achieved a level of precision comparable to first-principles methods while at the same time entering the hydrodynamic regime. We compared the structure factors and pair distribution functions to experimental data and unearthed distinctive collective excitations with intriguing features. Liquid lanthanum unveiled two transverse collective excitation branches, each closely tied to specific peaks in the velocity autocorrelation function spectrum. Furthermore, the analysis of the generalized specific heat ratio in the hydrodynamic regime investigated with the ML molecular dynamics simulations uncovered a peculiar behavior, impossible to discern with only ab initio simulations. Liquid Li4Pb, on the other hand, challenged existing claims by showcasing a rich array of branches in its longitudinal dispersion relation, including a high-frequency LiLi mode with a nonhydrodynamic optical character that maintains a finite value as q → 0. Additionally, we conducted an in-depth analysis of various transport coefficients, expanding our understanding of these liquid metallic systems. In summary, our ML approach yielded precise results, offering new and captivating insights into the structural and dynamic aspects of these materials.

Thermodynamic features of corrosion processes in liquid lead coolant in the presence of dissolved oxygen

In this work, the thermodynamic formalism of the law of acting masses is used to analyze the chemical equilibrium in a lead-based liquid metal solution in the case when iron and oxygen are present in the melt as impurities. The calculations were carried out using iron as an example, since it is this chemical element that is the main component of steels, which are currently regarded as the most promising container material for lead liquid-metal systems. The technology for controlling oxygen activity comes down to the fact that while maintaining the required oxygen concentration, lead becomes less chemically aggressive towards iron. By ensuring the constant required amount of oxygen in the liquid lead coolant, it is possible to maintain the basis of protective films on the surface of steel, which include iron and chromium oxides.

Towards High Efficiency and Rapid Production of Room-Temperature Liquid Metal Wires Compatible with Electronic Prototyping Connectors.

We present in this work new methodologies to produce, refine, and interconnect room-temperature liquid-metal-core thermoplastic elastomer wires that have extreme extendibility (>500%), low production time and cost at scale, and may be integrated into commonly used electrical prototyping connectors like a Japan Solderless Terminal (JST) or Dupont connectors. Rather than focus on the development of a specific device, the aim of this work is to demonstrate strategies and processes necessary to achieve scalable production of liquid-metal-enabled electronics and address several key challenges that have been present in liquid metal systems, including leak-free operation, minimal gallium corrosion of other electrode materials, low liquid metal consumption, and high production rates. The ultimate goal is to create liquid-metal-enabled rapid prototyping technologies, similar to what can be achieved with Arduino projects, where modification and switching of components can be performed in seconds, which enables faster iterations of designs. Our process is focused primarily on fibre-based liquid metal wires contained within thermoplastic elastomers. These fibre form factors can easily be integrated with wearable sensors and actuators as they can be sewn or woven into fabrics, or cast within soft robotic components.

Subchannel thermal–hydraulic analysis of a wire-wrapped 19-pin rod bundle in the NACIE-UP facility

Based on the experimental campaign performed on the NACIE-UP (NAtural Circulation Experiment-Upgraded) facility, the benchmark activity was proposed by ENEA to qualify and validate the numerical tools for the Heavy Liquid Metal (HLM) system. Xi’an Jiaotong University participated in the benchmark exercise of subchannel validation and the self-developed subchannel code YAOGUANG was applied to the thermal hydraulic analysis. The performed two tests with different power distributions on the Fuel Pin bundle Simulator (FPS) were simulated, characterized by transition from forced to natural circulation. The applicability of this code to the stable state and mass flow rate transient was evaluated by comparing the numerical outcomes with the experimental results. Then the effect of the non-uniform heating on the thermal field was analyzed. The results indicate that this subchannel code has good accuracy in simulating both steady state and transient conditions with uniform power distribution. For the non-uniform case, the subchannel calculations can capture the general trend of temperature distributions, with a larger simulation deviation observed. This discrepancy is mainly due to the limitations of existing models adopted because they didn’t consider the impacts of non-uniform conditions on the flow and heat transfer in rod bundles. Finally, the influence of non-uniform heating is mainly manifested as the increase of axial and radial temperature gradients and it helps to flatten the radial thermal field to some degree.

Ligand Mediation for Tunable and Oxide Suppressed Surface Gold-Decorated Liquid Metal Nanoparticles.

Gallium-based liquid metal systems hold vast potential in materials science. However, maximizing their possibilities is hindered by gallium's native oxideand interfacial functionalization. In this study, small-molecule ligands are adopted as surfactants to modify the surface of eutectic gallium indium (EGaIn) nanoparticles and suppress oxidation. Different p-aniline derivatives are explored. Next, the reduction of chloroanric acid (HAuCl4 ) onto these p-aniline ligand modified EGaIn nanoparticles is investigated to produce gold-decorated EGaIn nanosystems. It is found that by altering the concentrations of HAuCl4 or the p-aniline ligand, the formation of gold nanoparticles (AuNPs) on EGaIn can be manipulated. The reduction of interfacial oxidation and presence of AuNPs enhances electrical conductivity, plasmonic performance, wettability, stability, and photothermal performance of all the p-aniline derivative modified EGaIn. Of these, EGaIn nanoparticles covered with the ligand of p-aminobenzoic acid offer the most evenly distributed AuNPs decoration and perfect elimination of gallium oxides, resulting in the augmented electrical conductivity, and highest wettability suitable for patterning, enhanced aqueous stability, and favorable photothermal properties. The proof-of-concept application in photothermal therapy of cancer cells demonstrates significantly enhanced photothermal conversion performance along with good biocompatibility. Due to such unique characteristics, the developed gold-decorated EGaIn nanodroplets are expected to offer significant potential in precise medicine.

State-of-the-art review of the T/H system codes RELAP5 for HLM applications

Thermal-hydraulic code RELAP5, originally developed by INEEL under NRC contract for LWRs LOCA analysis, has been extensively validated and it is actually used worldwide as a best estimate code for LWRs transient analysis. This code was chosen in the early 2000s as the reference code for the thermal-hydraulics and accident analysis of Heavy Liquid Metal Fast Reactors within the frame of Italian research programs. Several original RELAP5 routines have been updated in order to implement suitable correlations generating the reference physical and thermodynamic properties for Lead and Lead-Bismuth Eutectic fluids. Similarly, some specific heat transfer correlations for liquid metals have been added. In almost twenty years, ENEA has conducted an extensive validation program to demonstrate the capability of the code to simulate the thermal–hydraulic behaviour of heavy liquid metal systems. This program was mainly conducted on the facilities of the Brasimone center (CHEOPE, CIRCE, NACIE), but also used data from international programs (MEGAPIE International Experiment and LACANES Benchmark OECD/NEA). Furthermore, the participation of ENEA in the projects financed by the European Commission in several Euratom programs for the study and design of HLM-cooled reactors (ELSY, SEARCH, MAXSIMA, LEADER, SESAME. MYRTE) has allowed to increase the confidence on the transient and accidental analyses conducted with RELAP5 also through the comparison with the results of other codes. RELAP5 is currently a reliable tool both as a support to reactor design (safety by design) and for accidental analyses.

Experimental, numerical and analytical evaluation of j×B -thrust for fast-liquid-metal-flow divertor systems of nuclear fusion devices

Divertor systems of fusion devices are exposed to intense heat loads from plasmas, which degrade solid plasma-facing components. Fast liquid metal (LM) flow divertors may be more advantageous for this purpose but have risk of piling due to intense magnetohydrodynamic (MHD) drag. However, severe deceleration of the flow could be countered with the injection of currents that are transverse to external magnetic fields, allowing to thrust the flow with j×B (Lorentz) forces. Given that the injection of currents as an approach to propel LM-divertor flows has remained experimentally understudied, this article focuses on the evaluation of j×B -thrust and finding its drawbacks. j×B -thrust was experimentally tested with free-surface-LM flows, a vertical magnetic field and an externally applied current. Experiments were reviewed with a theoretical model, showing agreement in the trends of theory and experiments. Full 3D-MHD-free-surface-flow simulations were also performed with FreeMHD and confirmed the sensitivity to unstable flow behavior in LM systems when applying external currents. Furthermore, excessive power requirements are expected for the implementation of j×B -thrust at the reactor scale, making these systems inefficient for commercial devices. This paper evidences that the simple operation of a LM-flow divertor with j×B -thrust, without any of the instabilities caused from reactor plasmas or parasitic currents, already presents intrinsic challenges.

On the application of liquid metal cooling for electronic switching devices

Increasingly smaller and lighter power electronics converters are needed for the advancement of electrified transport. The development of high heat flux heat sinks is imperative to maintain modern converters at an operable temperature. So far, liquid metal based heat sinks have not received as much attention as other solutions, yet they provide a multitude of benefits beyond their superior thermal conductivity. Their use with compact magnetohydrodynamic pumping systems, straight-forward incorporations of active cooling techniques, elimination of water corrosion issues in power converter systems using press-pack IGBT’s and a significant increase in thermal performance in conventional pin–fin structures are demonstrated in this paper. Some additional functionalities of liquid metal systems which could be explored in the future are also highlighted.

Subchannel modelling capabilities of RELAP5-3D© for wire-spaced fuel pin bundle

The paper deals with the presentation of a subchannel modeling approach developed with RELAP5-3D for lead and lead–bismuth eutectic (LBE) cooled wire-wrapped fuel bundle. For the modeling assessment, the code-to-experiment analysis is performed using experimental data from the NACIE-UP facility, hosted at ENEA Brasimone Research Center. Three relevant thermal hydraulic phenomena must be accounted in case of wire-wrapped fuel bundle: pressure drops along bundle, crossflow between adjacent subchannels, and sweeping mixing induced by helical wire. Furthermore, in case of liquid metal system, the effect of radial thermal conduction must be evaluated. All these phenomena are considered in the modeling methodology. A thermal hydraulic nodalization of the whole facility has been developed, with particular attention to the fuel pin bundle simulator (modelled with a detailed subchannel approach). The main outcomes of the activity are the assessment of satisfactory capabilities of the proposed subchannel modeling and the identification of some open issues to be investigated in the future works.

Dynamic Zinc in Liquid Metal Media as a Metal Ion Source for Highly Porous ZIF‐8 Synthesis

AbstractLiquid metals provide new dimensions for controlling and governing of reactions. The concept of freely moving metal solutes in liquid metals can be potentially used for enhancing and tuning interfacial reactions. In this work, zinc (Zn), as the solute metal is shown that, can move to the interface, enriching the interfacial area for the efficient synthesis of highly crystalline and porous zeolitic imidazolate framework‐8 (ZIF‐8). The highest rate of reaction is illustrated, and the best quality ZIF‐8, are obtained when a eutectic liquid metal system of Zn with gallium (Ga), containing 3.6 wt.% of Zn, is implemented. It is computationally shown that a combination of Ga activation and freely moving Zn leads to the highest reaction rate and better coordination with organic linkers. The comparisons with solid samples and non‐eutectic systems of Ga liquid demonstrate the advantages of eutectic mix. The work can be expanded to a variety of future interfacial reactions of zeolite imidazole frameworks for commercial scale up.

Development and validation of analysis code for spallation products behavior in LBE coolant system of ADS comparing with the distribution data in MEGAPIE spallation target

It is important to evaluate the inventories and the release and transport behavior of the spallation products (SPs) including polonium-210 in the Lead-Bismuth Eutectic (LBE) coolant system of Accelerator Driven System (ADS) for the safety studies of the radiological hazard both in the cases of normal operation and accident. Especially, the transport and deposition inside the coolant circulation system and the evaporation from the coolant to the cover gas are dominant mechanisms to evaluate the release and transport behavior of SPs. University of Fukui and Japan Atomic Energy Agency (JAEA) have been developing the computer analysis code TRAIL (Transport of RAdionuclides In Liquid metal systems) which predicts the time dependent behavior of SPs within the LBE coolant system of ADS for the wide range of operational events. The TRAIL code is intended to deal with the SPs transport, deposition and evaporation behavior mechanistically in consideration of a variety of the physicochemical configuration of SPs in LBE. The physicochemical configuration of the SPs is essential to evaluate the release and transport behavior because the physical and chemical properties such as the molecular weight, the density, the solubility in LBE and the vapor pressure depend on the configuration. The SPs behavior modelled in the code are based on the generalized flow network model including pipe and tank components. The flow network model is constituted from mass and energy conservation equations in consideration of the mass and energy transfer due to coolant flow effect, deposition or adsorption of SPs onto the structure surfaces, transport into the cover gas due to evaporation and radioactive decay of the radioactive SPs. The source term of both radioactive and stable SPs in the LBE coolant is given as input and the radioactive decay chain model for the radioactive SPs is implemented in the code to evaluate the effect of precursors on the SPs mobility. This paper presents the recent advancement status of the code development and the validation results comparing with the distribution data of volatile SPs in MEGAPIE spallation target.

Structural and electronic changes in Ga-In and Ga-Sn alloys on melting.

The melting behaviour of surface slabs of Ga-In and Ga-Sn is studied using periodic density functional theory and ab initio molecular dynamics. Analysis of the structure and electronics of the solid and liquid phases gives insight into the properties of these alloys, and why they may act as promising CO2 reduction catalysts. We report melting points for slabs of hexa-layer Ga-In (386 K) and Ga-Sn (349 K) that are substantially lower than the pure hexa-layer Ga system (433 K), and attribute the difference to the degree to which the dopant (In or Sn) disrupts the layered Ga network. In molecular dynamics trajectories of the liquid structures, we find that dopant tends to migrate from the centre of the slab towards the surface and accumulate there. Bader charge calculations reveal that the surface dopant atoms have increased positive charge, and density of states analyses suggest the liquid alloys maintain metallic electronic behaviour. Thus, surface In and Sn may provide good binding sites for intermediates in CO2 reduction. This work contributes to our understanding of the properties of liquid metal systems, and provides a foundation for modelling catalysis on these materials.

Performance test and uncertainty analysis of the FBG-based pressure transmitter for liquid metal system

The pressure measurement in the high-temperature liquid metal system, such as Sodium-cooled Fast Reactor(SFR), is important and yet it is very challenging due to its nature. The measuring pressure is relatively at low range and the applied temperature varies in wide range. Moreover, the pressure transfer material in impulse line needs to considered the high temperature condition. The conventional diaphragm-based approach cannot be used for it is impossible to remove the effect of thermal expansion. In this paper, the Fiber Bragg Grating(FBG) sensor-based pressure measuring concept is suggested that it is free of problems induced by the thermal expansion. To verify this concept, a prototype was fabricated and tested in an appropriate conditions. The uncertainty analysis result of the experiment is also included. The final result of this study clearly showed that the FBG-based pressure transmitter system is applicable to the extreme environment, such as SFR and any other high-temperature liquid metal system and the measurement uncertainty is within reasonable range.

Textile-Integrated Liquid Metal Electrodes for Electrophysiological Monitoring.

Next generation textile-based wearable sensing systems will require flexibility and strength to maintain capabilities over a wide range of deformations. However, current material sets used for textile-based skin contacting electrodes lack these key properties, which hinder applications such as electrophysiological sensing. In this work, a facile spray coating approach to integrate liquid metal nanoparticle systems into textile form factors for conformal, flexible, and robust electrodes is presented. The liquid metal system employs functionalized liquid metal nanoparticles that provide a simple "peel-off to activate" means of imparting conductivity. The spray coating approach combined with the functionalized liquid metal system enables the creation of long-term reusable textile-integrated liquid metal electrodes (TILEs). Although the TILEs are dry electrodes by nature, they show equal skin-electrode impedances and sensing capabilities with improved wearability compared to commercial wet electrodes. Biocompatibility of TILEs in an in vivo skin environment is demonstrated, while providing improved sensing performance compared to previously reported textile-based dry electrodes. The "spray on dry-behave like wet" characteristics of TILEs opens opportunities for textile-based wearable health monitoring, haptics, and augmented/virtual reality applications that require the use of flexible and conformable dry electrodes.

Stretchable Micro-devices towards Digital Transformation

In recent years, the demand for digital transformation (DX) in the industrial sector has been extremely high. In response to this high demand, a variety of smart devices have been invented and offered. Especially in the research field, flexible or bendable smart devices have been devised by using thin-film polymers such as polyimide and parylene as substrates. Micro/nanofabrication is a fundamental technology in the research and development of these smart devices. The presenter's laboratory has conducted research on flexible smart devices for social implementation based on micro/nanofabrication. Based on the knowledge obtained from flexible smart devices, we have also studied stretchable devices, which are expected to be the next generation of smart devices. In this presentation, we report an overview of our research on flexible smart devices and stretchable systems. In particular, we present our research on flexible smart devices and the development of smart devices for use in medical and animal experiments. In addition, research on stretchable sensors using liquid metal and stretchable systems are reported. Stretchable devices based on micro- and nano-fabrication might be further accelerated toward social implementation in the future.

Swirling to improve heat transfer in the MHD flow of liquid metal in a duct

The subject of this study is the effect of the initial “swirling” of the flow by installing cylindrical elements in the initial flow region affected by strong magnetic field. In particular, various designs (longitudinal, transverse, and inclined arrangement with respect to the magnetic field) and the dimensions of the cylinders are considered. To create liquid metal systems that are more predictable and possibly more efficient from the point of view of thermal hydraulics, we experimentally studied the flow in a rectangular channel with dimensions of 56×16 mm. For the first time, it was found that the presence of an initial flow disturbance leads to significant changes in the flow at a significant length (700 mm).

Liquid metal bubbles

Classical bubbles are ubiquitous in nature, throughout industrial production and daily life. So far, tremendous researches on bubbles are mostly focused on aqueous or lipid systems. In this study, a new conceptual bubble system based on liquid metals, whose surface tension is nearly eight times larger than that of water, is proposed and demonstrated. Such liquid metal bubbles display a series of completely different features over the existing bubbles generated via common liquids, especially those composed of conventional aqueous solutions. Through delivering fluids inside the interior of liquid metal system, we successfully achieved the regulation of liquid metal surface with diverse morphologies, including forming single bubble, hole and multi-bubble clusters etc. For more precise manipulations, the solution environment where liquid metal is immersed into can be divided into “film-forming” and “remover” species, enabling the control of generation and vanishing of oxide on the metal surface in particular area through different combinations, resulting in the complicated administration and control of liquid metal matters. Further, the electrical characteristics of these morphologies were justified and disclosed to be capable of building logic circuits. Along this way, a display device was developed to exhibit various patterns, showing or even storing information inside. Overall, the liquid metal bubble as well as its periodic excitation opens applications in diverse areas, including but not limited to soft robotics, logic system, or underwater circuits.

Coupled system thermal Hydraulics/CFD models: General guidelines and applications to heavy liquid metals

This work aims to review the general guidelines to be adopted to perform coupled System Thermal Hydraulics (STH)/CFD calculations. The coupled analysis is often required when complex phenomena characterized by different characteristic time and length scales are investigated. Indeed, by STH/CFD coupling the main drawbacks of both stand-alone codes are overcome, reducing the computational cost and providing more realistic solutions. A review of several works available in literature and involving different coupling approaches, codes, time-advancing schemes and application fields is given. Besides STH/CFD coupling techniques, spatial domains and numerical schemes are analysed in detail. A brief description of applications to heavy liquid metal systems is also reported; lessons drawn in the frame of these and other works are then considered in order to develop a set of good practice guidelines for coupled STH/CFD applications.

Conductivity influence on interfacial waves in liquid metal batteries and related two-layer systems

Fluid flows in liquid metal batteries can be generated by a number of effects. We start with a short overview of different driving mechanisms and then address questions specific to the metal pad role instabilities in three-layer systems. We focus on the role of the conductivity distribution in the cell, noting at the same time that interfacial tension should be considered as well for smaller cells. Following this discussion, numerical results on the excitation of interfacial waves in two-layer liquid metal systems with miscibility gaps bearing an interface normal electric current are presented. Confirming recent results from the literature, we find that magnetic damping plays a decisive role for strong vertical magnetic fields. In addition, boundary conditions for the electric field strongly influence critical currents and growth rates.