Structure Of Liquid Metals Research Articles

Giant Decrease in Interfacial Energy of Liquid Metals by Native Oxides.

Native oxides form on the surface of many metals. Here, using gallium-based liquid metal alloys, Johnson-Kendall-Roberts (JKR) measurements are employed to show that native oxide dramatically lower the tension of the metal interface from 724 to 10 mNm-1. Like conventional surfactants, the oxide has asymmetry between the composition of its internal and external interfaces. Yet, in comparison to conventional surfactants, oxides are an order of magnitude more effective at lowering tension and do not need to be added externally to the liquid (i.e., oxides form naturally on metals). This surfactant-like asymmetry explains the adhesion of oxide-coated metals to surfaces. The resulting low interfacial energy between the metal and the interior of the oxide helps stabilize non-spherical liquid metal structures. In addition, at small enough macroscopic contact angles, the finite tension of the liquid within the oxide can drive fluid instabilities that are useful for separating the oxide from the metal to form oxide-encased bubbles or deposit thin oxide films (1-5nm) on surfaces. Since oxides form on many metals, this work can have implications for a wide range of metals and metal oxides in addition to explaining the physical behavior of liquid metal.

Three-Dimensional Electrodes of Liquid Metals for Long-Term, Wireless Cardiac Analysis and Modulation.

Cardiovascular disease is a major public health issue, and smart diagnostic approaches play an important role in the analysis of electrocardiograms. Here, we present three-dimensional, soft electrodes of liquid metals that can be conformably attached to the surfaces of the heart and skin for long-term cardiac analysis. The fine micropillar structures of biocompatible liquid metals enable precise targeting to small tissue areas, allowing for spatiotemporal mapping and modulation of cardiac electrical activity with high resolution. The low mechanical modulus of these liquid-metal electrodes not only helps avoid inflammatory responses triggered by modulus mismatch between the tissue and electrodes, but also minimizes pain when embedded in biological tissues such as the skin and heart. Furthermore, in vivo experiments with animal models and human trials demonstrate long-term and accurate monitoring of electrocardiograms over a period of 30 days.

Recent advances in synchrotron X-ray studies of the atomic structures of metal alloys in liquid state

Research into the atomic structures of metal materials in the liquid state, their dynamic evolution versus temperature until the onset of crystal nucleation has been a central research topic in condensed matter physics and materials science for well over a century. However, research and basic understanding of the atomic structures of liquid metals are far less than those in the solid state of the same compositions. This review serves as a condensed collection of the most important research literature published so far in this field, providing a critical and focused review of the historical research development and progress in this field since the 1920s. In particular, the development of powerful synchrotron X-ray sources and the associated experimental techniques and sample environments for studying in-situ the atomic structures of different metallic systems. The key findings made in numerous pure metals and metallic alloy systems are critically reviewed and discussed with the focus on the results and new understandings of structural heterogeneities found inside a bulk liquid, at the liquid surface or liquid-solid interface. The possible future directions of research and development on the most advanced experimental and modeling techniques are envisaged and briefly discussed as well.

Liquid metal manifold microchannel heat sink for ultra-high heat flux cooling

Advanced heat dissipation technology is crucial for chip operation and performance utilization. Room temperature liquid metal convection cooling technology has demonstrated its efficacy as a viable approach for addressing high heat flux heat dissipation. However, the smaller specific heat capacity of liquid metal leads to a large temperature rise, hindering the advancement of its cooling technology. To address this, a liquid metal manifold channel structure is proposed to convert the continuous long-range flow into a segmented short-range flow. The good matching between liquid metal and manifold structures is adequately demonstrated through a comparison with alternative coolant and channel structure. The simulation results demonstrate the effectiveness of liquid metal manifold channel cooling in dealing with a heat flux of 1000 W/cm2, ensuring that the maximum temperature of the chip remains below 351.7 K. Moreover, the convective heat transfer coefficient even reaches 106 W/(m2·K), which is ten times larger than that of water conventional microchannel heat sink. Orthogonal experiments analyzed the impact of structural parameters on dissipation performance, including the height of the microchannel, ratio of manifold length to fin length, length of fin in manifold, width of channel, and ratio of fin with to channel width. The height of the microchannel has been identified as the most critical factor. This manifold structure mitigates the inherent limitation of liquid metal's lower specific heat capacity, enabling efficient thermal management for electronic devices under ultra-high heat flux conditions.

Dynamic sampling of liquid metal structures for theoretical studies on catalysis.

Liquid metals have recently emerged as promising catalysts that can outcompete their solid counterparts for many reactions. Although theoretical modelling is extensively used to improve solid-state catalysts, there is currently no way to capture the interactions of adsorbates with a dynamic liquid metal. We propose a new approach based on ab initio molecular dynamics sampling of an adsorbate on a liquid catalyst. Using this approach, we describe time-resolved structures for formate adsorbed on liquid Ga-In, and for all intermediates in the methanol oxidation pathway on Ga-Pt. This yields a range of accessible adsorption energies that take into account the at-temperature motion of the liquid metal. We find that a previously proposed pathway for methanol oxidation on Ga-Pt results in unstable intermediates on a dynamic liquid surface, and propose that H desorption must occur during the path. The results showcase a more accurate way to treat liquid metal catalysts in this emerging field.

Electrosynthesis of Quasi-Epitaxial Crystals on Liquid Metals.

Electrosynthesis of single-crystalline metallic and intermetallic particles with a preferred orientation onto liquid metal electrodes has been performed. Liquid gallium electrodes immersed in aqueous alkaline electrolytes without any molecular additive or external solid seeding substrates were used to electroreduce separately Pb2+, Bi3+, Pd2+, and Mn2+. The crystallinity, composition, and orientation of the electrodeposition products were characterized by using scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, grazing incidence X-ray diffraction, and energy-dispersive X-ray spectroscopy. Electrodeposition of Pb and Bi results in the incipient formation of two-dimensional (2D) nuclei that subsequently direct the growth of Pb and Bi single crystals along the most close-packed [111] and [0001] directions, respectively. The absence of any intervening surface oxides and a low electroreduction flux are necessary to avoid polycrystalline dendrite formation. Under comparable conditions, the electrodeposition of Pd and Mn results in single-crystalline intermetallic particles at the interface. Each crystal exhibits a preferred orientation consistent with the unique atomic packing of the near-surface region of the liquid Ga. The presented study suggests a new concept in electrodeposition processes where the liquid metal structure imparts quasi-epitaxial growth in a system in which the electrode material specifically has no crystallinity or long-range order. This study is thus the first demonstration of highly oriented electrodeposition at a liquid/liquid interface under ambient conditions, highlighting the unique solvation environment of liquid metal interfaces for forming thin metallic and intermetallic films.

Solidification-Controlled Compartmentalization of Bismuth-Tin Colloidal Particles.

Nucleation and growth are the main steps of microstructure formation. Nucleation occurs stochastically in a bulk material but can be controlled by introducing or removing catalytic sites, or creating local gradients. Such manipulations can already be implemented to bulk materials at a high level of sophistication but are still challenging on micrometer or smaller scales. Here, we explore the potential to transfer this vast knowledge in classical metallurgy to the fabrication of colloidal particles and report strategies to control phase distribution within a particle by adjusting its solidification conditions. Benefiting from the core-shell structure of liquid metals and the constrained volume of particles, we demonstrate that the same alloy particle can be transformed into a lamellar, composite, Janus, or striped particle by the felicitous choice of the phase separation process pathway. This methodology offers an unprecedented opportunity for the scalable production of compartmentalized particles in high yields that are currently limited to inherently unscalable methods.

Effect of copper salt on the synthesis of copper-doped gallium metal liquid based photocatalyst (Cu/Ga2O3), and its application in acetaminophen photodegradation

This work investigates the impact of two copper salts on the synthesis, crystal structure, morphology, and optical properties of copper-doped Gallium Liquid Metal (GLM)-based photocatalysts. Ga2O3 and Ga2O3‑copper ion doped were synthesized from nitrate and sulfate salts using GLM as the precursor by ultrasonic transducer. Characterization was done by TGA, XRD, XPS, SEM/EDS, ATR-FTIR, UV–Vis–NIR diffused reflectance and Zeta potential. We explore their application in photodegrading and mineralizing acetaminophen under different experimental conditions. Results show that salt significantly affects the physical-chemical and photocatalytic properties. Doping gallium oxides with copper leads to high levels of degradation (up to 80%) and mineralization.

Understanding and Expanding the Prospects for Electrosynthesis with Liquid Metal Electrodes

ConspectusThis Account describes and summarizes the latest work from our laboratory on developing and maturing strategies based on low-temperature liquid metals as reaction environments for materials synthesis. The electrochemical liquid-liquid-solid (ec-LLS) crystal growth concept is a hybrid method that combines electrodeposition and melt crystal growth. Using liquid metals as both electrodes and solvents for the purpose of producing inorganic crystals and materials, a simple and environmentally friendly process is possible. The impetus is to address the key deficiency in the inorganic crystalline materials that are the basis of modern optoelectronics and renewable energy capture/conversion systems. Specifically, existing methods for synthesizing crystalline inorganic materials for these purposes are largely energy- and resource-intensive, with a substantial impact on the environment when scaled. A long-term goal of our work with ec-LLS is to realize a materials synthetic process that is matured without requiring intensive resources or negatively impacting the environment. To this end, the factors that both limit and govern ec-LLS processes must be identified and understood. To date, questions regarding the factors that affect crystal nucleation and growth, form factors, and overall composition remain.Previous work established concretely ec-LLS as a versatile method for synthesizing and producing crystalline semiconductors at low temperatures as either particles, nanowires, or microwires. Subsequent experiments have focused on two tiers. First, the microscopic details of the liquid metal and its interfaces that dictate materials synthesis and crystal growth must be identified. Second, strategies that widen the attainable material form factors to facilitate device architectures must be realized. Hence, this Account describes results aimed at answering three questions: (1) What are the consequences of reaching supersaturation by an electrochemical rather than a thermal driving force for crystal growth in ec-LLS? (2) Can the location of nucleation and subsequent crystal growth be controlled? (3) Does the atomic structure of the liquid metal affect product formation in ec-LLS? The science described herein illustrates the value of in situ methods spanning transmission electron microscopy, X-ray diffraction, and X-ray reflectance for revealing the role that liquid metal composition and structure can play in ec-LLS. Additionally, we summarize work that shows for the first time that it is possible to produce both single-crystalline epitaxial films and complex intermetallic compounds through ec-LLS by tuning the cell design, electrochemical excitation waveform, and composition of the liquid metal electrodes.The cumulative findings described here substantially enrich our understanding of the ec-LLS concept while simultaneously motivating further questions moving forward. Is it possible to attain complete control over the crystalline quality and composition of ec-LLS products? Can the materials produced by ec-LLS provide tailored functional properties for targeted applications? Can the ec-LLS strategy be further refined to allow material synthesis and deposition at precise locations with deterministically chosen form factors? What synthetic pathways are accessible when even more sophisticated electrochemical waveforms and cell designs are used? Our hope is that this Account will spur additional researchers to help answer such questions.

Unique Surface Fluorescence Induced from the Core-Shell Structure of Gallium-Based Liquid Metals Prepared by Thermal Oxidation Processing.

Liquid metals (LMs) have emerged as promising functional materials that combine the properties of both liquid and metal. These characteristics enabled them to find applications in many fields. However, the LMs usually can only display a silver-white physical appearance, which limits their further applications in the fields with the imposition of stringent requirements for color and aesthetics. Herein, we report that the surface of LMs was transformed directly from metal to fluorescent semiconductor layer by an example of eutectic GaInSn (eGaInSn) induced by thermal oxidation. Specifically, a core-shell structure is formed from the fluorescent layer and the LMs. The shell endows the LMs with fluorescence without affecting their interior fluidity and conductivity. In particular, the formation process as well as the degree of crystallization, phase transformation, and light emission of the fluorescent oxide shell on the surface of LMs is regulated by the component content. A thorough analysis of surface morphology, composition, structure, and properties of the fluorescent shell suggests that the Ga2O3 layer is formed on the surface of gallium-based LMs after their immersion in deionized water. Subsequently, thermal oxidation results in the formation of the β-Ga2O3 shell on the surface of liquid metals. Importantly, abundant oxygen vacancies (VO) in β-Ga2O3 as the donors and the gallium vacancies (VGa), gallium-oxygen vacancy pairs (VO-VGa), defect energy levels, and intrinsic defects as the acceptors enabled the light emission. The fluorescent LMs have promising potential for flexible lighting and displays, anticounterfeiting measures, sensing, and chameleon robots.

3D Printed Spring‐Type Electronics with Liquid Metals for Highly Stretchable Conductors and Inductive Strain/Pressure Sensors (Adv. Mater. Technol. 7/2022)

Spring-Type Electronics In article number 2101657, Tomoyuki Yokota, Takao Someya and colleagues develop soft spring-type electronic devices formed by core–sheath structures of liquid metals and 3D-printed elastomeric shells. The spring devices work not only as stretchable conductors with minor resistance change, but also as inductive strain/pressure sensors for robotic applications by using the change in the magnetic flux caused by the spring deformation.

Shape stabilization and laser triggered shape transformation of magnetic particle functionalized liquid metal motors

Liquid metal motors made from biologically benign gallium are promising candidates for various applications ranging from drug delivery to targeting and killing cancer cells directly. One of the main problems with this novel technology is the need to utilize a membrane, making it possible to maintain a defined shape in order to perform the required functions. For magnetic remote guidance, liquid metal motors can be doped with magnetic iron microparticles, forming a transition magnetic liquid. In an alternative approach liquid metal structures are coated with magnetite nanoparticles. We hereby present an approach to laminate biologically benign gallium-based magnetic liquid metal motors with a biodegradable and biocompatible macromolecular thin film to retain the initial shape. Thanks to the polymer lamination and by the help of magnetic fields, the presented liquid metal motors can be remotely guided. The shape retaining macromolecular thin film can be liquefied by photothermal effects such as laser irradiation in order to change the shape of the liquid metal motor into a droplet due to surface energy minimization, allowing for penetration of structures smaller than the initial motor size. This work uses a relatively large technical demonstrator to show the technical realization and properties of this novel system, which opens up new paths and potential applications.

Pseudogap in a crystalline insulator doped by disordered metals

Key to our understanding of how electrons behave in crystalline solids is the band structure that connects the energy of electron waves to their wavenumber. Even in phases of matter with only short-range order (liquid or amorphous solid), the coherent part of electron waves still has a band structure. Theoretical models for the band structure of liquid metals were formulated more than five decades ago1-15, but, so far, band-structure renormalization and the pseudogap induced by resonance scattering have remained unobserved. Here we report the observation of the unusual band structure at the interface of a crystalline insulator (black phosphorus) and disordered dopants (alkali metals). We find that a conventional parabolic band structure of free electrons bends back towards zero wavenumber with a pseudogap of 30-240millielectronvolts from the Fermi level. This is wavenumber renormalization caused by resonance scattering, leading to the formation of quasi-bound states in the scattering potential of alkali-metal ions. The depth of this potential tuned by different kinds of disordered alkali metal (sodium, potassium, rubidium and caesium) allows the classification of the pseudogap of p-wave and d-wave resonance. Our results may provide a clue to the puzzling spectrum of various crystalline insulators doped by disordered dopants16-20, such as the waterfall dispersion observed in copper oxides.

Electrically Induced Wire‐Forming 3D Printing Technology of Gallium‐Based Low Melting Point Metals

AbstractLow‐melting point metals and alloys, as emerging 3D printing ink, have attracted more and more attention especially for flexible or intelligent conductors and electronics. However, achieving 3D continuity of liquid metal structures or patterns using a common method is still challenging and worth pursuing. In this study, a generalized method is proposed for 3D printing structures made of low melting gallium‐based alloys with diverse melting points, which should greatly expand their applications. The mechanism for shaping liquid metal inks relies on the combination actions between electrocapillarity and oxidation, which significantly reduces the high surface tension as well provides solid frame for the inner liquid metals. Taken galinstan as an example, the printing conditions, including the viscosity of hydrogel, positive voltage (0–15 V), calcium chloride concentration, and velocity (the movement speed of the printing head) are explored to optimize the process. The printed galinstan is characterized to observe the morphology and elemental analysis of the surface oxide layer. During the process, the chemical reagents are all safe and non‐toxic, which is in line with the green product requirements. This printing method shall have broad application prospect in flexible electronics, biosensors, biomedical engineering, contrast agent in vivo, and other fields.

Modeling of liquid lithium flow in porous plasma facing material

Abstract Flowing liquid lithium can, in principle, create a renewable surface interacting with the plasma, providing protection for the underlying solid substrate. Recent experiments [1] showed that liquid lithium supplied through a porous medium can limit the plasma facing surface temperature, even at high heat flux values in excess of 10 MW/m2. The use of new 3D printing techniques allows creation of plasma facing components that supply liquid lithium through capillary channels. Numerical analysis can be used to develop and optimize porous plasma facing component using virtual prototyping. The present contribution introduces a numerical model of liquid metal flow in a porous structure, interacting with the plasma. The model uses computational fluid dynamics (CFD) to model a flow through a complex 3D geometry including magneto-hydrodynamics (MHD) effects. The CFD set-up covers the liquid metal, plasma and solid structures, simultaneously, connected by realistic interfaces. Small scale interface structures are modeled separately to obtain a self-consistent interface functions. Customized version of the general-purpose CFD is used to handle complex 3D geometries, and efficient pre- and post-processing. MHD is introduced using the magnetic vector potential approach, allowing precise fluid–solid interface treatment. Special stabilization procedures were derived and applied to improve convergence of the momentum balance equations with source terms due to Lorentz force and surface tension. Conjugate heat transfer analysis was performed in the plasma, liquid metal and solid components. The customized code was validated using analytical results for high Hartmann number flow. Results of the validation and numerical analysis of liquid lithium plasma facing components using porous walls will be presented.

Some remarks on the investigation of structure, thermodynamic and surface properties of liquid metals using square well potential

The shortcomings found in the paper of Mishra, Lalneihpuii and Pathak [Chem. Phys. 457 (2015) 13] are discussed. It is shown that the random phase approximation is used in the work, but not the mean spherical approximation as it is declared by the authors.

Noninvasive Conductivity and Temperature Sensing Using Magnetic Induction Spectroscopy Imaging

The work presents a perspective in evaluating electromagnetic tomography reconstruction through a spectral eddy current imaging arrangement. Embarking from an established analytical basis, the spectroscopic relation of a metallic conductive body to its physical properties is revealed via multifrequency mutual impedance measurement. Characteristics are evident, from either modeling or experiment, on certain frequency ranges that discriminate the object’s circumstances. Both the amplitude ratio and phase-contrast image spectrum show information on the conductivity and structure of a target considered pivotal for industrial applications. Two test cases are reported: liquid metal structure determination and contactless temperature evaluation of a remote/hidden medium/object. Using eddy current-based spectroscopic imaging data and appropriate calibration, this work, for the first time, demonstrates a novel thermal mapping system. This is a wireless and inductive-based temperature mapping device that can have great potential applications where none of the existing thermal measuring devices could work noninvasively.

Effect of Heat Treatment of a Melt on the Structure and Properties of the Corresponding Crystalline Ingots or Castings

The modern concepts of the structure of liquid metals and alloys are considered. Several types of microinhomogeneity and microheterogeneity are shown to exist in liquid metal solutions. Their structural state changes as a result of variations in composition, history, temperature, and pressure or the influence of various external actions. Upon subsequent cooling at an appropriate rate, these changes can persist up to liquidus and affect the structure and properties of the solidified alloy. The main attention is paid to the influence of the heating temperature of a liquid metal. For aluminum-based alloys, the possibility of developing the optimum heat-treatment conditions for melting using the results of studying the structure and properties of melts has been shown. This optimized heat treatment of melts is shown to be an effective method to improve the quality of alloys.

Interaction of exogenous refractory nanoparticles of Al2O3 and MgAl2O4 with nonferrous metal impurities in iron melts

The exogenous refractory nanoparticles is proposed for refining iron-based melts from nonferrous metal impurities. Investigated the heterophase interaction of Al2O3 and MgAl2O4 nanoparticles with Sb/Sn/Cu and showed that the degree of removal of nonferrous metal impurities was in the Fe-Sb system up to 30 rel.%, in the Fe-Sn system up to 29 rel. % and in the Fe-Cu system up to 23 rel. %. The existence of refractory nanoparticles in a liquid metal was proved by studying the structural properties of the melt. In the melts, after the introduction of the nanoparticles, inversion of the temperature coefficient of surface tension is observed, as well as multidirectional change depending on the nature of the nanoparticles and the holding time during interfacial interaction. Decompression and compression of the melts after the introduction of nanoparticles and the multidirectional nature of the dependences of properties indicate a possible change in the cluster structure of liquid metal.

Heat Flow in Earth's Core From Invariant Electrical Resistivity of Fe‐Si on the Melting Boundary to 9 GPa: Do Light Elements Matter?

AbstractThe electrical resistivity and thermal conductivity of liquid Fe alloys are the least constrained parameters in Earth's outer core (OC). These parameters are important as they modulate energy budget available for the geodynamo and affect the spatiotemporal evolution of the core. We report results of electrical resistivity measurements on solid and liquid Fe‐4.5 wt%Si from 3–9 GPa using a large volume multianvil press. The internally modified 18/11 octahedron cell was used to maintain the geometry of the liquid sample and to delay the onset of contamination. Electrical resistivity of solid Fe‐4.5Si decreases steadily with pressure and is very sensitive to increasing temperature‐driven onset of phase transitions. Along the melting boundary and within error, electrical resistivity remains constant and assumes the same value of 120 μΩcm as observed in pure liquid Fe. The results are interpreted in the context of icosahedral short‐range order (ISRO) structures that exhibit higher concentration with increasing pressure. Along the melting line, the increasing concentration of ISROs reduces charge carrier mean free path and prevents decrease of electrical resistivity with increasing pressure as seen in liquid metals, Cu, Ag, and Au, which do not have ISROs. In light of recent developments in understanding of the structure and dynamics of liquid transition metals and alloys, we postulate that our findings are applicable to other Fe alloys in the OC with small light element (C, S, and O) content. We calculated an adiabatic heat flow of 9.4–12 TW at the OC‐CMB interface, which admits thermal convection.