Synergistic interactions of aerogel and liquid metal: a novel aerogel-reinforced metal matrix composite for advanced aerospace applications

A Bright Future for Liquid Functional Materials?

Experimental investigation on the interaction characteristics of lead‑bismuth liquid metal and water

Liquid metals (LMs) and alloys are attracting increasing attention owing to their combined advantages of high conductivity and fluidity, and have shown promising results in various emerging applications. Patterning technologies using LMs are being actively researched; among them, direct ink writing is considered a potentially viable approach for efficient LM additive manufacturing. However, true LM additive manufacturing with arbitrary printing geometries remains challenging because of the intrinsically low rheological strength of LMs. Herein, colloidal suspensions of LM droplets amenable to additive manufacturing (or "3D printing") are realized using formulations containing minute amounts of liquid capillary bridges. The resulting LM suspensions exhibit exceptionally high rheological strength with yield stress values well above 103 Pa, attributed to inter-droplet capillary attraction mediated by the liquid bridges adsorbed on the oxide skin of the LM droplets. Such liquid-bridged LM suspensions, as extrudable ink-type filaments, are based on uncurable continuous-phase liquid media, have a long pot-life and outstanding shear-thinning properties, and shape retention, demonstrating excellent rheological processability suitable for 3D printing. These findings will enable the emergence of a variety of new advanced applications that necessitate LM patterning into highly complicated multidimensional structures.

Electrochemical deposition of Sr and Ba into liquid metals (Bi and Sb) was investigated in LiCl-KCl-SrCl2-BaCl2 electrolytes at 500–650 °C as a means to separate stable alkaline-earth ions from the molten salts (eutectic LiCl-KCl) utilized for recycling used nuclear fuel. Considering the higher stability of Sr and Ba ions relative to the Li and K ions in the chloride system, it would seem impractical to deposit Sr and Ba from the molten chloride solutions by electrochemical means; however, this work will present that the deposition of Sr and Ba into liquid metal electrodes becomes thermodynamically feasible by leveraging the strong chemical interactions between alkali/alkaline-earth metals and liquid metals. The thermodynamic properties of four binary alkaline earth-liquid metal alloys, (Sr, Ba)-(Bi, Sb), were determined by electromotive force (emf) measurements using solid-state electrolytes to examine the degree of chemical interactions (activity) between alkaline-earth metals and liquid metals. Using a pure alkaline-earth metal A (A = Sr or Ba) as the reference electrode and binary A-B alloys (B = Bi or Sb) as working electrodes in solid-state binary CaF2-AF2 electrolyte, emf measurements were conducted over a temperature range of 450–850 °C in 25 °C increments. Reproducible emf values were obtained within ±5 mV accuracy during cooling-heating cycle at alloy mole fractions up to x A(in B) = 0.40. Based on the experimentally determined emf values of alkaline-earths in liquid Bi and Sb electrodes, the electrode reactions involving Sr and Ba elements were found to be thermodynamically feasible due to substantially larger emf values of Sr and Ba in Bi, compared to those of Li and K in Bi. Namely, the chemical interactions of liquid metals (Bi and Sb) were stronger for alkaline-earths (Sr and Ba) than for alkali (Li and K) metals. Based on thermodynamic measurements, the liquid metal electrodes were subjected to cathodic discharge at a constant current density of 50 mA cm–2 in eutectic LiCl-KCl with the addition of 5–10 mol% of SrCl2 and/or BaCl2. As shown in Figure 1, the use of liquid metals (Bi and Sb) resulted in the deposition of Ba in LiCl-KCl-10mol%BaCl2 electrolyte. Further study in LiCl-KCl-SrCl2-BaCl2 electrolytes also indicated that the use of strongly interacting liquid metal electrodes could result in the co-deposition of Sr and Ba in addition to Li. The results of this work show that alkaline-earth fission products (Sr2+ and Ba2+) accumulated in molten salts can be recovered into liquid metals by electrochemical separation, which could be employed as a critical step for recycling the process salt (LiCl-KCl) in order to minimize the generation of additional nuclear wastes. Figure 1. Cross-section analyses of Bi (discharged at 510 °C) and Sb (discharged at 650 °C) electrodes under constant current density at 50 mA cm– 2 in LiCl-KCl-10mol%BaCl2 electrolyte, using SEM and elemental X-ray mapping. Figure 1

Liquid metals are employed as a coolant in liquid metal fast reactors (LMFR) and are considered breeders and coolants for future power-producing fusion reactors. The interaction of liquid metals with other coolants, such as air and water, is one of the possible occurrences in liquid metal-cooled reactors. Although the SIMMER-III computer code is currently in the validation and verification phase, it is a prospective candidate code for correctly investigating possible accidents. This study aims to determine the stability and well-posedness of the SIMMER-III code Eulerian-Eulerian two-fluid model (TFM) under any such accident scenario. This work also considers the influence of the virtual mass force and diffusion forces in momentum on TFM stability in accelerated liquid metal, steam, and non-condensable gaseous flows throughout all flow regimes. The characteristics method is used to assess the ill-posed nature of TFM for all types of accidents and accident scenarios in a hypothetical simplified system model with several components (Lead–Lithium, non-condensable gases, and water vapor). It has been discovered that the analysis findings vary from the air and water two-component two-phase flows (characteristics roots spectrum and error growth rate patterns) and are particularly sensitive to the diffusion and virtual mass coefficients. This is because liquid metals have a higher density than liquid water and steam, resulting in strong virtual mass forces and weak diffusion forces in liquid-metal and gas two-phase flows. Because of the extensive range of possible interactions between fluxes of different components, producing an accurate representation of diffusion in multi-component mixtures is difficult. Because of this, it is strongly suggested that the virtual mass coefficient and diffusion coefficients be handled more accurately for these kinds of flows. The values of these coefficients significantly affect how accurate proposed TFM predictions are, but there hasn't been much research on how to estimate them. The study also sheds light on the model's accuracy and highlights the areas where the model's predictions will be mathematically trustworthy.

The nuclear quadrupole relaxation time in liquid metals is calculated, assuming free-ion cores interacting by an oscillatory screened potential, and whose positions in the liquid are described by the time-dependent pair distribution function of Oppenheim and Bloom. The relaxation time depends on two- and three-particle correlation functions, and the three-particle correlations are treated by means of the superposition approximation. Uncertainties in the antishielding factor and the potential oscillations are eliminated by using the experimental value of the quadrupole coupling constant in the solid. Detailed calculations are performed for Ga and In, and good agreement with the observed relaxation time is obtained if the three-particle terms are neglected. The calculated three-particle terms are not negligible, and it is suggested that the superposition approximation introduces serious errors.

Quantum theory of pure liquid metals as two-component systems

With the ultimate aims of clarifying the interpretation and the utility of effective ion-ion interactions in liquid metals, and of understanding the unusual isotopic mass dependence of the shear viscosity of liquid metal Li, a fully quantum statistical mechanical theory is developed from the many-body Hamiltonian of the conduction electron-positive ion assembly. We have set up quantum equations of motion which are analogs of classical continuity and conservation equations by expanding the equation for the Wigner distribution function about its diagonal. The most important of these equations for our present purposes relates the time derivative of the current density j(r, t) to the flux of current and to density-density correlation functions for electrons, electron-ions, and ions. This theory is then applied to neutron scattering by liquid metals. While the theory is sufficiently general in principle to treat electron-ion interaction of arbitrary strength, it is shown that when the interacion is weak, the usual results are recovered, along with the effective ion-ion interaction. In this latter connection, it is also demonstrated how the effective Ornstein-Zernike function C(q) in a liquid metal is related to bare ion and bare electron direct correlation functions and to the bare electron partial structure factor. Combining C(q) with one of the classical equations of liquid structure such as Born-Green or Percus-Yevick then relates the effective ion-ion interaction to the partial correlation functions of the bare ions and electrons. It is further shown how gradient expansions of the correlation functions lead to equations of motion for the density, current, and energy density which are simply the hydrodynamic equations of the present quantum theory of two-component systems. It is pointed out that the analog of the Navier-Stokes equation for the two-component system may be used to identify the quantity 4 3 η + ζ for the liquid metal, η and ζ being respectively the shear and bulk viscosities. Finally, it is demonstrated that 4 3 η + ζ depends explicitly on functional derivatives of the nonequilibrium pair distribution functions of ion-ion, electron-ion, and electron-electron correlations.

Energy transfer and interaction between liquid metal with water

Dry liquid metals stabilized by silica particles: Synthesis and application in photothermoelectric power generation

A mathematical model is developed to describe the interaction of a liquid metal with the metallic inclusions introduced into cellular polystyrene in a casting model. This model takes into account the filling kinetics of a mold, the influence of the thermal destruction of cellular polystyrene, and the heat exchange between the base alloy and the filler material. The results of experiments on lost-foam casting of samples support the predictions of mathematical simulation.

A formula for an effective interionic interaction in a liquid metal is derived by means of the density-functional method. The effective interaction is described in terms of the direct correlation function (DCF) of an electron-ion mixture: the electron-electron DCF Cee and the electron-ion DCF Cel. In this formula, the influence of ions on the exchange-correlation effect for electrons can be introduced appropriately through the DCF Cee, which involves the local-field correction (LFC) Gee in the presence of ions, and the non-linear effects are taken into account by the DCF Cel, which plays the role of a 'non-linear' pseudopotential. Also, an expression for the internal energy of a perfectly ionised electron-ion mixture is derived by following the usual pseudopotential method with a modification that ions are taken as a component of a liquid metal, instead of being treated as a uniform positive background. This expression proves to lead to the same expression for an effective interatomic interaction. As an application, effective proton-proton interactions in liquid metallic hydrogen are calculated. In this system, it is shown to be inappropriate to use the fundamental approximation that the LFC Gee in a metal should be equal to the LFC Gjell in the jellium. Furthermore, non-linear effects, characterised by the LFC Gep between electrons and protons, are found to be important. As a consequence, effective proton-proton interactions show a strong dependence on the proton configuration.

The use of liquid metals introduces solid-liquid metal interactions which are not primarily electrochemical, as found in systems involving aqueous raedia. The corrosion of solid metals by these coolants occurs as the system attempts to attain chemical equilibrium. The mechanisms by which this can occur are (a) dissolutioning, which results from the solubility relationships between the solid and liquid metals, and (b) impurity reactions, resulting from the presence of interstitial impurities, such as oxygen, nitrogen, and carbon, in the solid and liquid metals. The manner in which dissolutioning proceeds gives rise to many types of attack ranging from simple solution to mass transfer of one or more constituents of an alloy. Some variables which influence the rate and type of dissolutive corrosion are: temperature, flow velocity, surface area to volume ratio, surface condition of solid metal, temperature gradient, and number of materials in contact with the same liquid metal. The refractory metals tungsten, molybdenum, tantalum, and niobium, as well as other high-melting bodycentered cubic metals, have excellent resistance to dissolutive attack by the alkali liquid metals at high temperatures. However, there are numerous occasions when it is desirable to utilize the unique capabilities of several structural materials in the same system. A few experiments have been conducted which show that, when more than one type of solid metal or alloy is in contact with an alkali metal, the tendency for the system to achieve equilibrium results in a number of complex interactions involving interchange of metallic and nonmetallic constituents. These interactions generally are deleterious and therefore material selection can be limited. The most significant corrosion problem involving refractory metals appears to be the influence of the impurities, oxygen, nitrogen, and carbon. Experiments have been conducted to study the effect of such impurities in both the refractory metals and alkali metals. As an example, data are presented which show that the presence of small quantities of oxygen in either tantalum or niobium results in the penetration of these metals by lithium over a wide range of temperatures. It has also been found that oxygen in sodium increases its corrosion rate when in contact with niobium and other refractory metals. In addition, a method to predict the redistribution of impurities which are present in solution in either the solid or liquid metal is compared with experimental results. The corrosion of solid metals by liquid metals often occurs in complex multicomponent systems. For this reason, further data on solubilities of single components, multicomponent effects, temperature coefficients of solubilities, and kinetics of dissolution and precipitation of solid metals are needed. It is also suggested that more emphasis be placed on analytical techniques for determining the concentrations of oxygen, nitrogen, and carbon in liquid metals in order that their effects upon various corrosion processes might be better understood. (auth)

An experimental study is performed to investigate the quasi-static fracture toughness and damage monitoring capabilities of liquid metal (75.5% Gallium/24.5% Indium) reinforced intraply glass/carbon hybrid composites. Two different layups (G-0, where glass fibers are along the crack propagation direction; C-0, where carbon fibers are along the crack propagation direction) and two different weight percentages of liquid metal (1% and 2%) are considered in the fabrication of the composites. A novel four-probe technique is employed to determine the piezo-resistive damage response under mode-I fracture loading conditions. The effect of layups and liquid metal concentrations on fracture toughness and changes in piezo-resistance response is discussed. The C-composite without liquid metal demonstrated higher fracture toughness compared to that of the G-composite due to carbon fiber breakage. The addition of liquid metal decreases the fracture initiation toughness of both G- and C-composites. Scanning electron microscopy images show that liquid metal takes the form of large liquid metal pockets and small spherical droplets on the fracture surfaces. In both C- and G-composites, the peak resistance change of composites with 2% liquid metal is substantially lower than that of both no-liquid metal and 1% liquid metal composites.

Magnetically responsive soft smart materials have garnered significant academic attention due to their flexibility, remote controllability, and reconfigurability. However, traditional soft materials used in the construction of these magnetically responsive systems typically exhibit low density and poor thermal and electrical conductivities. These limitations result in suboptimal performance in applications such as medical radiography, high-performance electronic devices, and thermal management. To address these challenges, magnetically responsive gallium-based liquid metals have emerged as promising alternatives. In this review, we summarize the methodologies for achieving magnetically responsive liquid metals, including the integration of magnetic agents into the liquid metal matrix and the utilization of induced Lorentz forces. We then provide a comprehensive discussion of the key physicochemical properties of these materials and the factors influencing them. Additionally, we explore the advanced and potential applications of magnetically responsive liquid metals. Finally, we discuss the current challenges in this field and present an outlook on future developments and research directions.