Gallium Alloy Research Articles

Shaping a gallium alloy and an ionic liquid into spherical mirrors for future liquid-based telescopes—experimental setup and demonstration in parabolic flights

Shaping a gallium alloy and an ionic liquid into spherical mirrors for future liquid-based telescopes—experimental setup and demonstration in parabolic flights

Investigation of laminar flow and heat transfer performance of Gallium alloy based nanofluids in minichannel heat sink

Investigation of laminar flow and heat transfer performance of Gallium alloy based nanofluids in minichannel heat sink

An X‐Ray Absorption Spectroscopy Investigation into the Fundamental Structure of Liquid Metal Alloys

Gallium and gallium alloys have gained significant interest due to gallium's low melting point. This property allows for gallium‐based catalysts to take advantage of the unique reaction environments only available in the liquid state. While understanding of the catalytic properties of liquid metals is emerging, a comprehensive investigation into the fundamental structures of these materials has yet to be undertaken. Herein, the structure of liquid gallium, along with related liquid alloys EGaIn, EGaSn, and Galinstan are explored using X‐ray absorption spectroscopy (XAS). In contrast to some other studies that show dimers, analysis of the XAS data both in X‐ray absorption near edge structure and extended X‐ray absorption fine structure shows that when fully dissolved the materials are largely homogenous with no obvious signs of local structures. Ga shows a bond contraction when melted which is consistent with its increase in density; however, an expansion in bond length is observed when alloyed with In and Sn. XAS data indicate that the effective nuclear charge (Zeff) of In and Sn follows the trend expected based on electronegativity. Molecular dynamic (MD) simulations are performed to simulate the structure and trends between MD and XAS; the trends agree well but MD overestimates bond lengths.

Flexible Crossbar Molecular Devices with Patterned EGaIn Top Electrodes for Integrated All-Molecule-Circuit Implementation.

Here, a unique crossbar architecture is designed and fabricated, incorporating vertically integrated self-assembled monolayers in electronic devices. This architecture is used to showcase 100 individual vertical molecular junctions on a single chip with a high yield of working junctions and high device uniformity. The study introduces a transfer approach for patterned liquid-metal eutectic alloy of gallium and indium top electrodes, enabling the creation of fully flexible molecular devices with electrical functionalities. The devices exhibit excellent charge transport performance, sustain a high rectification ratio (>103), and stable endurance and retention properties, even when the devices are significantly bent. Furthermore, Boolean logic gates, including OR and AND gates, as well as half-wave and full-wave rectifying circuits, are successfully implemented. The unique design of the flexible molecular device represents a significant step in harnessing the potential of molecular devices for high-density integration and possible molecule-based computing.

Liquid metal droplets impacting superhydrophobic surface in a viscous (non-oxidizing) environment

The hypothesis of the present research is the existence of distinct spatial-temporal characteristics of non-oxidized liquid metal (LM) droplets impacting a solid surface. To provide a quantitative claim to this hypothesis, we created a test matrix based on the well-known impingement regime map bounded by two dimensionless quantities—Weber number (We) and Ohnesorge number (Oh). The range of these quantities is from 10−2 to 102 (We) and 10−3 to 101 (Oh), leading to Reynolds number (Re) (≡We1/2/Oh) to vary from 10−2 to 104. The class of LMs opted for are post-transition metals—eutectic gallium alloys—due to their several desired practical features, such as low melting point, non-toxicity, and low vapor pressure. The research is conducted using numerical experiments performed using C++ OpenFOAM libraries. To ensure the reliability of the code, we tested our work with numerous impingement behaviors of fluids available in the literature. A plethora of droplet behaviors are reported, such as deposition, rebound, bubble entrapment, and splash. Several features of droplet impingement were critically examined, such as temporal spreading factor, maximum spreading factor, and contact time of droplets on the surfaces. Moreover, the conventional scaling laws regarding the impingement behavior of droplets were tested, with new ones proposed where deemed necessary. Furthermore, a distinct route for the entrapment of droplet is observed, caused by the bulging of LM droplet during the recoiling stage. Emphasis is made to form delineations for these impingement characteristics using dimensionless groups (i.e., We, Oh, and Re).

Low-loss liquid metal interconnects for superconducting quantum circuits

Building a modular architecture with superconducting quantum computing chips is one of the means to achieve qubit scalability, allowing the screening, selection, replacement, and integration of individual qubit modules into large quantum systems. However, the nondestructive replacement of modules within a compact architecture remains a challenge. Liquid metals, specifically gallium alloys, can be alternatives to solid-state galvanic interconnects. This is motivated by their self-healing, self-aligning, and other desirable fluidic properties, potentially enabling the nondestructive replacement of modules at room temperatures, even after operating the entire system at millikelvin regimes. In this study, we present coplanar waveguide resonators (CPWRs) interconnected by gallium alloy droplets, achieving high internal quality factors up to nearly one million and demonstrating performance on par with the continuous solid-state CPWRs. Leveraging the desirable fluidic properties of gallium alloys at room temperature and their compact design, we envision a modular quantum system enabled by liquid metals.

Versatile Patterning of Liquid Metal via Multiphase 3D Printing.

This paper presents a scalable and straightforward technique for the immediate patterning of liquid metal/polymer composites via multiphase 3D printing. Capitalizing on the polymer's capacity to confine liquid metal (LM) into diverse patterns. The interplay between distinctive fluidic properties of liquid metal and its self-passivating oxide layer within an oxidative environment ensures a resilient interface with the polymer matrix. This study introduces an inventive approach for achieving versatile patterns in eutectic gallium indium (EGaIn), a gallium alloy. The efficacy of pattern formation hinges on nozzle's design and internal geometry, which govern multiphase interaction. The interplay between EGaIn and polymer within the nozzle channels, regulated by variables such as traverse speed and material flow pressure, leads to periodic patterns. These patterns, when encapsulated within a dielectric polymer polyvinyl alcohol (PVA), exhibit an augmented inherent capacitance in capacitor assemblies. This discovery not only unveils the potential for cost-effective and highly sensitive capacitive pressure sensors but also underscores prospective applications of these novel patterns in precise motion detection, including heart rate monitoring, and comprehensive analysis of gait profiles. The amalgamation of advanced materials and intricate patterning techniques presents a transformative prospect in the domains of wearable sensing and comprehensive human motion analysis.

Regulating interfacial exchange coupling in perpendicular magnetized Fe/DO22-Mn3Ga bilayer films

Manganese gallium alloy with DO22-type chemical ordering (DO22-Mn3Ga) thin film represents an intriguing candidate for fabricating the fundamental composition of magnetic devices. In this paper, we prepare the Fe/DO22-Mn3Ga composite films on thermal MgO (100) substrates with different annealing temperatures and report the interfacial exchange coupling between Fe and DO22-Mn3Ga bilayers. Fe layer thickness and annealing temperature are predominant in regulating the nature and strength of interfacial exchange coupling. It is found that there is a ferromagnetic coupling between Fe and DO22-Mn3Ga layers. Their exchange coupling strength can be regulated by changing the Fe soft magnetic layer thickness in a reasonable range. Additionally, the interface diffusion generated from heat treatment induces to change of the nature of exchange coupling. It is possible that Fe replaces Mn site in the DO22-Mn3Ga unit cell due to smaller atomic radius and higher electronegativity compared with Mn. Antiferromagnetic coupling from annealed Fe/DO22-Mn3Ga film with high perpendicular magnetic anisotropy is technologically important to research synthetic antiferromagnetic structure for spin-transfer-torque magnetoresistive random access memory. Our works is helpful for the exploration of interfacial science and development of magnetic devices.

Scalable Microwires through Thermal Drawing of Co-Extruded Liquid Metal and Thermoplastic Elastomer.

This article demonstrates scalable production of liquid metal (LM)-based microwires through the thermal drawing of extrudates. These extrudates were first co-extruded using a eutectic alloy of gallium and indium (EGaIn) as a core element and a thermoplastic elastomer, styrene-ethylene/butylene-styrene (SEBS), as a shell material. By varying the feed speed of the co-extruded materials and the drawing speed of the extrudate, it was possible to control the dimensions of the microwires, such as core diameter and shell thickness. How the extrusion temperature affects the dimensions of the microwire was also analyzed. The smallest microwire (core diameter: 52 ± 14 μm and shell thickness: 46 ± 10 μm) was produced from a drawing speed of 300.1 mm s-1 (the maximum attainable speed of the apparatus used), SEBS extrusion speed of 1.50 mm3 s-1, and LM injection rate of 5 × 105 μL s-1 at 190 °C extrusion temperature. The same extrusion condition without thermal drawing generated significantly large extrudates with a core diameter of 278 ± 26 μm and shell thickness of 430 ± 51 μm. The electrical properties of the microwires were also characterized under different degrees of stretching and wire kinking deformation which proved that these LM-based microwires change electrical resistance as they are deformed and fully self-heal once the load is removed. Finally, the sewability of these microwires was qualitatively tested by using a manual sewing machine to pattern microwires on a traditional cotton fabric.

Long-Term Corrosion of Eutectic Gallium, Indium, and Tin (EGaInSn) Interfacing with Diamond.

Thermal transport is of grave importance in many high-value applications. Heat dissipation can be improved by utilizing liquid metals as thermal interface materials. Yet, liquid metals exhibit corrosivity towards many metals used for heat sinks, such as aluminum, and other electrical devices (i.e., copper). The compatibility of the liquid metal with the heat sink or device material as well as its long-term stability are important performance variables for thermal management systems. Herein, the compatibility of the liquid metal Galinstan, a eutectic alloy of gallium, indium, and tin, with diamond coatings and the stability of the liquid metal in this environment are scrutinized. The liquid metal did not penetrate the diamond coating nor corrode it. However, the liquid metal solidified with the progression of time, starting from the second year. After 4 years of aging, the liquid metal on all samples solidified, which cannot be explained by the dissolution of aluminum from the titanium alloy. In contrast, the solidification arose from oxidation by oxygen, followed by hydrolysis to GaOOH due to the humidity in the air. The hydrolysis led to dealloying, where In and Sn remained an alloy while Ga separated as GaOOH. This hydrolysis has implications for many devices based on gallium alloys and should be considered during the design phase of liquid metal-enabled products.

The mechanism of water decomposition on surface of aluminum and gallium alloy during the hydrogen production process: A DFT study

The efficient hydrogen-production through the Aluminum-water reaction has become a prominent subject of interest. The impediment encountered in the reaction can be effectively alleviated by Aluminum-based alloy. In this study, density functional theory (DFT) was utilized to explore the mechanism of water decomposition stage on the surface of aluminum and gallium alloy (AGA). Through surface reaction calculations of 12 stable AGA configurations, it was gradually revealed that the optimal alloy ratio was gallium-to-aluminum at 3.5:1. Analysis of the density of states (DOS) indicated that the presence of gallium amplified the activity of surface aluminum. Moreover, frontier orbital theory and charge density maps confirmed that, due to the weak interaction between Ga and ions, the presence of H2 inhibited Ga passivation, thereby enhancing the reactivity of AGA. This paper provided valuable insights into the surface reaction mechanisms of AGA using DFT, offering theoretical support for hydrogen production processes.

Remarkable reduction in thermal contact resistance between target and heat exchanger using TIMs in isotope neutron source accelerator

The high thermal contact resistance (TCR) between the target and the heat exchanger in the Isotope Neutron Source Accelerator will cause the high-energy charged particle beam to stay in the target, resulting in a remarkable increase of temperature which affects the production of stable isotopes. At present, the usage of thermal interface materials (TIMs) can fill the gap at the contact surface and thus reduces the TCR. In this paper, aiming at the actual working condition of neutron source, the steady-state TCR measurement experiment is designed under vacuum and high temperature environment. The TCR at the contact surface was reduced after adding graphite films, thermal greases, liquid metals and preloads. The improvement of TCR of the contact surface between palladium (Pd), copper (Cu) and graphite (Gr) were measured respectively. The results show that the TCR between palladium and graphite is reduced by 95 % by adding liquid metal (Gallium alloy). The TCR between copper and graphite was reduced by 91 % by brazing method. Compared with other TIMs, graphite film has the advantages of high thermal conductivity, high temperature resistance and no fluidity. Adding 0.08 mm thick graphite film between Pd/Gr and Cu/Gr contact surface can reduce the TCR by 50 % and 70 %, respectively. The improvement effect between the two contact surfaces was not obvious when 15.9–318.3 kPa preload was applied.

Graphene‐Assisted Chemical Stabilization of Liquid Metal Nano Droplets for Liquid Metal Based Energy Storage

AbstractEnergy storage devices with liquid‐metal electrodes have attracted interest in recent years due to their potential for mechanical resilience, self‐healing, dendrite‐free operation, and fast reaction kinetics. Gallium alloys like Eutectic Gallium Indium (EGaIn) are appealing due to their low melting point and high theoretical specific capacity. However, EGaIn electrodes are unstable in highly alkaline electrolytes due to Gallium oxide dissolution. In this letter, this bottleneck is addressed by introducing chemically stable films in which nanoscale droplets of EGaIn are coated with trace amounts of graphene oxide (GO). It is demonstrated that a GO to EGaIn weight ratio as low as 0.01 provides enough protection for a thin film formed by GO@EGaIn nanocomposite against significantly acidic or alkaline environments (pH 1‐14). It is shown that GO coating significantly enhances the surface stability in such environments, thus improving the energy storage capacity by over 10x. Microstructural analysis confirms GO@EGaIn composite stability and enhanced electrochemical performance. Utilizing this, a thin‐film supercapacitor is fabricated. Results indicate that when coating the EGaIn with GO to EGaIn ratio of 0.001, the areal capacitance improves by 10 times, reaching 20.02 mF cm−2. This breakthrough paves the way for advanced liquid metal‐based thin‐film electrodes, promising significant improvements in energy storage applications.

Atomic diffusion in liquid gallium and gallium-nickel alloys probed by quasielastic neutron scattering and molecular dynamic simulations

The atomic mobility in liquid pure gallium and a gallium-nickel alloy with 2 at% of nickel is studied experimentally by incoherent quasielastic neutron scattering. The integral diffusion coefficients for all-atom diffusion are derived from the experimental data at different temperatures. DFT-based ab-initio molecular dynamics (MD) is used to find numerically the diffusion coefficient of liquid gallium at different temperatures, and numerical theory results well agree with the experimental findings at temperatures below 500 K. Machine learning force fields derived from ab-initio molecular dynamics (AIMD) overestimate within a small 6% error the diffusion coefficient of pure gallium within the genuine AIMD. However, they better agree with experiment for pure gallium and enable the numerical finding of the diffusion coefficient of nickel in the considered melted alloy along with the diffusion coefficient of gallium and integral diffusion coefficient, that agrees with the corresponding experimental values within the error bars. The temperature dependence of the gallium diffusion coefficient DGa(T) follows the Arrhenius law experimentally for all studied temperatures and below 500 K also in the numerical simulations. However, DGa(T) can be well described alternatively by an Einstein–Stokes dependence with the metallic liquid viscosity following the Arrhenius law, especially for the MD simulation results at all studied temperatures. Moreover, a novel variant of the excess entropy scaling theory rationalized our findings for gallium diffusion. Obtained values of the Arrhenius activation energies are profoundly different in the competing theoretical descriptions, which is explained by different temperature-dependent prefactors in the corresponding theories. The diffusion coefficient of gallium is significantly reduced (at the same temperature) in a melted alloy with natural nickel, even at a tiny 2 at% concentration of nickel, as compared with its pure gallium value. This highly surprising behavior contradicts the existing excess entropy scaling theories and opens a venue for further research.

Sculpting liquid metal stabilized interfaces: a gateway to liquid electronics.

Liquid electronics have potential applications in soft robotics, printed electronics, and healable electronics. The intrinsic shortcomings of solid-state electronics can be offset by liquid conductors. Alloys of gallium have emerged as transformative materials for liquid electronics owing to their intrinsic fluidity, conductivity, and low toxicity. However, sculpting liquid metal or its composites into a 3D architecture is a challenging task. To tackle this issue, herein, we explored the interfacial chemistry of metal ions and tannic acid (TA) complexation at a liquid-liquid interface. First, we established that an MIII-TA network at the liquid-liquid interface could structure liquid in liquid by jamming the interfacial film. The surface coverage of the droplet largely depends on the concentration of metal ions, oxidation state of metal ions and pH of the surrounding environment. Further extending the approach, we demonstrated that TA-functionalized gallium nanoparticles (Ga NPs) can also sculpt liquid droplets in the presence of transition metal ions. Finally, a mold-based free-standing 3D architecture is obtained using the interfacial reaction and interfacial crowding of a metal-phenolate network. Conductivity measurement reveals that these liquid constructs can be used for low-voltage electronic applications, thus opening the door for liquid electronics.

MEMS Package for an Iron–Gallium Nanowire-Based Acoustic Sensor

A novel nanowire-based acoustic sensor incorporating cilia-like nanowires made of magnetostrictive iron–gallium (Galfenol) alloy has been designed and fabricated using micromachining techniques. The sensor and its package design are analogous to the structural design and the transduction process of a human-ear cochlea. The sensor responds when nanowires shear against the fixed membrane, in response to the motion of the flexible membrane on interaction with the acoustic waves. This results in a change in the magnetic flux in the nanowires, which is converted into electrical voltage by a giant magnetoresistive (GMR) sensor. As the acoustic sensor is designed for underwater applications, packaging is a key issue for the effective working of this sensor. A good package should provide a suitably protective environment to the sensor, while allowing sound waves to reach the sensing element with a minimal attenuation. In this paper, design efforts aimed at producing this microelectromechanical (MEMS) bio-inspired acoustic transducer have been detailed along with the process sequence for its fabrication. Package materials including external enclosure and fluid medium have been identified based on their acoustic performance in water by conducting several experiments to compare their impedance and attenuation characteristics and moisture absorption properties.

Short-Range Order and Its Stability in a Soft-Magnetic Iron–Gallium Alloy

Short-Range Order and Its Stability in a Soft-Magnetic Iron–Gallium Alloy

The Thermal Conductivity of Near-Eutectic Galinstan (Ga68.4In21.5Sn10) Molten Alloy

The need for new heat transfer agent for many applications, namely in the consumer electronics industry, requires materials, liquids at room temperature, with high thermal conductivity. From the different possibilities, Galinstan, a eutectic alloy of Gallium, Indium, and Tin with a melting point (Tm = 283.4 K) has been proposed for many applications, namely for replacing the toxic mercury element, used for many years. It is the purpose of this paper to report thermal conductivity measurements of Galinstan, product name Gallium/Indium/Tin Eutectic (NL-011), Ga68.4In21.5Sn10. The method used was the transient hot strip (THS), using a platinum metal-film sensor, produced by PVD in ceramic substrates, and electrically insulated with a heat-shrinkable coating. The details of the data acquisition system and measuring procedure are reported. Measurements were performed between 28 °C and 103 °C (301 K to 376 K), at atmospheric pressure, with an estimated uncertainty of 6%, and compared with available literature. Data were correlated for linear interpolation. This type of sensor is applied to molten metals for the first time, proofing to concept to future applications in molten metals and molten salts at higher temperatures.Graphical

Conjugate heat transfer of a turbulent tube flow of water and GaInSn with azimuthally inhomogeneous heat flux

An experimental study of the conjugate heat transfer in a turbulent tube flow with azimuthally homogeneous and inhomogeneous heat flux distribution, where the tube is heated with a constant heat flux only over the half circumference, is presented. Using two fluids with clearly different Prandtl numbers (water and a liquid metal alloy), thermohydraulic effects that occur when fluids with very low Prandtl number are used in contrast to ordinary fluids (e.g. water with Pr≈1) are discussed. The test section is validated with water (Pr=5−7.4) for a Reynolds number in the range of 5·103<Re<4.2·104. The experimental data agree excellently with literature data. The maximum nondimensional temperature at the inner surface of the tube is expressed using a simple relationship based on the efficiency of a fin with an adiabatic tip. A near eutectic alloy of gallium, indium and tin (GaInSn, Pr=0.03) is used for the liquid metal experiments. The Péclet number is varied within the range of 240<Pe<3·103. Based on the experimental data of this work, an adapted correlation for the Nusselt number in a turbulent liquid metal tube flow with azimuthally homogeneous heat flux is provided:Nu=4.364+0.0276·Pe0.803The experimental data underlines, that the azimuthally averaged Nusselt number for an azimuthally inhomogeneous heat flux distribution can also be calculated with this correlation with an acceptable level of accuracy. Remarkably, the ratio of the local convective heat transfer coefficient to the azimuthally averaged value for GaInSn reaches a value up to 0.6 at the location of the maximum wall temperature. This is in strong contrast to water, where this ratio is close to unity.

TWO TYPES OF GALLIUM EXPOSURE TO ALUMINUM

The effect of gallium on aluminum during their fusion is investigated. The corrosion rate of aluminum alloys with 1, 2 and 5 at % gallium content was experimentally determined, which was 0.001, 0.00101 and 0.00062 g/m2 · h, respectively, which is less than that of pure grade A99 aluminum – 0.0016 g/m2 · h. The rate of dissolution of these alloys in acidic and alkaline media is determined. X-ray phase analysis showed the homogeneity of the alloys under consideration. The morphology of aluminum alloys with gallium was studied, after exposure to an aggressive environment – a solution of hydrochloric acid. The possibility of obtaining hydrogen and nanoscale alumina by decomposition of water by activated gallium aluminum alloy is shown. Activation of the aluminum surface by gallium alloy occurs according to the Rebinder effect and the article presents a micrograph of the surface of aluminum treated with Ga-Sn alloy, clearly demonstrating this effect. When using metallic gallium in contact with aluminum, the interaction requires heating to a temperature above 30°C (the melting point of gallium is 29.7°C), the melting point of the eutectic composition 92Ga–8Sn is 20.0°C, which allows the interaction to begin at room temperature. At temperatures of about 4°C, activated aluminum can be stored for a long time. The quality of hydrogen obtained by decomposition of water should be higher than that obtained by cracking, and the cost is close to a well-developed technology of electrolysis of water and no more than 2 times the cost of its synthesis via cracking of hydrocarbons. Gallium and its liquid alloys are non-toxic, almost do not interact with water, activate aluminum, preventing the formation of a protective oxide film, penetrate into the intergranular space and aluminum easily interacts with water, forming hydrogen and aluminum hydroxide.