Wikipedia

Liquid metal

For other uses, seeLiquid metal (disambiguation).
Not to be confused withLiquidmetal.

Aliquid metalis ametalor ametal alloywhich isliquidat or nearroom temperature.[1]

Liquidgalliummetal, at 30°C (86°F).

The only stable liquid elemental metal at room temperature ismercury(Hg), which is molten above −38.8 °C (234.3 K, −37.9 °F). Three more stable elemental metals melt just above room temperature:caesium(Cs), which has a melting point of 28.5 °C (83.3 °F);gallium(Ga) (30 °C [86 °F]); andrubidium(Rb) (39 °C [102 °F]). The radioactive metalfrancium(Fr) is probably liquid close to room temperature as well. Calculations predict that the radioactive metalscopernicium(Cn) andflerovium(Fl) should also be liquid at room temperature.[2]

Alloys can be liquid if they form aeutectic,meaning that the alloy's melting point is lower than any of the alloy's constituent metals. The standard metal for creating liquid alloys used to bemercury,butgallium-based alloys, which are lower both in theirvapor pressureat room temperature and toxicity, are being used as a replacement in various applications.[3][4]

Thermal and electrical conductivity

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Alloy systems that are liquid at roomtemperaturehavethermalconductivity far superior to ordinary non-metallic liquids,[5]allowing liquid metal to efficiently transfer energy from the heat source to the liquid. They also have a higher electrical conductivity that allows the liquid to be pumped more efficiently, by electromagnetic pumps.[6]This results in the use of these materials for specific heat conducting and/or dissipation applications.

Another advantage of liquid alloy systems is their inherent high densities.

Viscosity

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Theviscosityof liquid metals can vary greatly depending on the atomic composition of the liquid, especially in the case of alloys. In particular, the temperature dependence of the viscosity of liquid metals may range from the standardArrhenius lawdependence, to a much steeper (non-Arrhenius) dependence such as that given empirically by theVogel-Fulcher-Tammann equation. A physical model for the viscosity of liquid metals, which captures this great variability in terms of the underlying interatomic interactions, was also developed.[7]

The electrical resistance of a liquid metal can be estimated by means of the Ziman formula, which gives the resistance in terms of the staticstructure factorof the liquid as can be determined byneutronorX-ray scatteringmeasurements.

Wetting to metallic and non-metallic surfaces

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Gallium wets skin, as shown here.

Onceoxideshave been removed from the substrate surface, most liquid metals willwetmost metallic surfaces. At room temperature, liquid metals are often reactive and soluble to metallic surfaces, though some solid metals are resistant to attack by the common liquid metals.[8]For example gallium iscorrosiveto all metals excepttungstenandtantalum,which have a high resistance to corrosion, more so thanniobium,titaniumandmolybdenum.[9]

Similar toindium,gallium and gallium-containing alloys have the ability to wet to many non-metallic surfaces such asglassandquartz.Gently rubbing the alloy into the surface may help induce wetting. However, this observation of "wetting by rubbing into glass surface" has created a widely spread misconception that the gallium-based liquid metals wet glass surfaces, as if the liquid breaks free of the oxide skin and wets the surface. The reality is the opposite: the oxide makes the liquid wet the glass. In more details: as the liquid is rubbed into and spread onto the glass surface, the liquid oxidizes and coats the glass with a thin layer of oxide (solid) residues, on which the liquid metal wets. In other words, what is seen is a gallium-based liquid metal wetting its solid oxide, not glass. Apparently, the above misconception was caused by the super-fast oxidation of the liquid gallium in even a trace amount of oxygen, i.e., nobody observed the true behavior of a liquid gallium on glass, until research at theUCLAdebunked the above myth by testingGalinstan,a gallium-based alloy that is liquid at room temperature, in an oxygen-free environment.[10]Note: These alloys form a thin dull looking oxide skin that is easily dispersed with mildagitation.The oxide-free surfaces are bright and lustrous.

Applications

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Applications of liquid metals includethermostats,switches,barometers,heat transfersystems, andthermal coolingand heating designs. They can also be used to conduct heat and electricity between non-metallic and metallic surfaces. Due to their free-flowing nature, another potential application is wearable and medical devices, where material deformability is important.[4][3]

Liquid metal is sometimes used as athermal interface materialbetweencoolersandprocessorsbecause of its high thermal conductivity. ThePlayStation 5video game consoleuses liquid metal to cool components inside the console.[11]Liquid metal cooled nuclear reactorsalso use them.

Liquid metal can sometimes be used for biological applications, i.e., making interconnects that flex without fatigue. As Galinstan is not particularly toxic, wires made from silicone with a core of liquid metal would be ideal for intracardiac pacemakers and neural implants where delicate brain tissue cannot tolerate a conventional solid implant. In fact, a wire constructed of this material can be stretched to 3 or even 5 times its length and still conduct electricity, returning to its original size and shape with no loss.[12]

Due to their unique combination of highsurface tensionandfluidic deformability,liquid metals are useful for creating softactuators.[13][14][15]The force-generating mechanisms in liquid metal actuators are typically achieved by modulation of their surface tension.[16][17][18]For instance, a liquid metal droplet can be designed tobridgetwo moving parts (e.g., inrobotic systems) in such a way to generate contraction when the surface tension increases.[19]The principles of muscle-like contraction in liquid metal actuators have been studied for their potential as a next-generationartificial musclethat offers several liquid-specific advantages over other solid materials.[20]

Liquid-mirror telescopescan use liquid metals formed into a parabola through a spinning tank to serve as theprimary mirrorof areflecting telescope.[21]

TheSpallation Neutron Sourceemploys liquid metals as targets for generating pulsed neutron beams.

See also

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References

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  1. ^Neumann, Taylor V.; Dickey, Michael D. (2020)."Liquid Metal Direct Write and 3D Printing: A Review".Advanced Materials Technologies.5(9): 2000070.doi:10.1002/admt.202000070.ISSN2365-709X.
  2. ^Mewes, Jan-Michael; Schwerdtfeger, Peter (11 February 2021)."Exclusively Relativistic: Periodic Trends in the Melting and Boiling Points of Group 12".Angewandte Chemie.60(14):7703–7709.doi:10.1002/anie.202100486.PMC8048430.PMID33576164.
  3. ^abKleiner, Kurt (3 May 2022)."Gallium: The liquid metal that could transform soft electronics".Knowable Magazine.doi:10.1146/knowable-050322-2.Retrieved31 May2022.
  4. ^abTang, Shi-Yang; Tabor, Christopher; Kalantar-Zadeh, Kourosh; Dickey, Michael D. (26 July 2021)."Gallium Liquid Metal: The Devil's Elixir".Annual Review of Materials Research.51(1):381–408.Bibcode:2021AnRMS..51..381T.doi:10.1146/annurev-matsci-080819-125403.ISSN1531-7331.S2CID236566966.
  5. ^ Kunquan, Ma; Jing, Liu (October 2007). "Liquid metal management of computer chips".Frontiers of Energy and Power Engineering in China.1(4):384–402.doi:10.1007/s11708-007-0057-3.ISSN1673-7504.S2CID195071023.
  6. ^Miner, A.; Ghoshal, U. (2004-07-19). "Cooling of high-power-density microdevices using liquid metal coolants".Applied Physics Letters.85(3):506–508.Bibcode:2004ApPhL..85..506M.doi:10.1063/1.1772862.ISSN0003-6951.
  7. ^Fu, Yu; Li, Hongxia; Tang, Kai; Yang, Shenglan; Shi, Yue; Liu, Bin; Luo, Qun; Zhang, Lijun; Li, Qian; Pan, Fusheng (2024-06-01)."Melt viscosity of light alloys: Progress and challenges".Journal of Materials Science & Technology.183:72–88.doi:10.1016/j.jmst.2023.11.002.ISSN1005-0302.S2CID265424554.
  8. ^Wade, K.; Banister, A. J. (1975).The Chemistry of Aluminum, Gallium, Indium, and Thallium.Pergamon Texts in Inorganic Chemistry. Vol. 12.ASINB0007AXLOA.
  9. ^Lyon, Richard N., ed. (1952).Liquid Metals Handbook(2 ed.). Washington, D.C.{{cite book}}:CS1 maint: location missing publisher (link)
  10. ^ Liu, T.; S., Prosenjit; Kim, C.-J. (April 2012). "Characterization of Nontoxic Liquid-Metal Alloy Galinstan for Applications in Microdevices".Journal of Microelectromechanical Systems.21(2):443–450.CiteSeerX10.1.1.703.4444.doi:10.1109/JMEMS.2011.2174421.S2CID30200594.
  11. ^Grubb, Jeff (October 7, 2020)."PlayStation 5 uses liquid metal — here's why that's cool".VentureBeat.RetrievedDecember 19,2020.
  12. ^Zhang, Mingkuan; Wang, Xiaohong; Huang, Zhiping; Rao, Wei (2020)."Liquid Metal Based Flexible and Implantable Biosensors".Biosensors.10(11): 170.doi:10.3390/bios10110170.PMC7696291.PMID33182535.
  13. ^Dickey, Michael D; Chiechi, Ryan C; Larsen, Ryan J; Weiss, Emily A; Weitz, David A; Whitesides, George M (2008)."Eutectic gallium-indium (EGaIn): a liquid metal alloy for the formation of stable structures in microchannels at room temperature".Advanced Functional Materials.18(7):1097–1104.doi:10.1002/adfm.200701216.S2CID538906.
  14. ^Liao, Jiahe (2022).Liquid metal actuators(Ph.D. thesis). Carnegie Mellon University.
  15. ^Majidi, Carmel (2021)."Fluid-like soft machines with liquid metal".Matter.4(2):336–337.doi:10.1016/j.matt.2021.01.009.
  16. ^Liao, Jiahe; Majidi, Carmel (2021)."Soft actuators by electrochemical oxidation of liquid metal surfaces".Soft Matter.17(7):1921–1928.Bibcode:2021SMat...17.1921L.doi:10.1039/D0SM01851A.PMID33427274.S2CID231577619.
  17. ^Russell, Loren; Wissman, James; Majidi, Carmel (18 December 2017)."Liquid metal actuator driven by electrochemical manipulation of surface tension".Applied Physics Letters.111(25): 254101.Bibcode:2017ApPhL.111y4101R.doi:10.1063/1.4999113.
  18. ^Khan, Mohammad Rashed; Eaker, Collin B; Bowden, Edmond F; Dickey, Michael D (2014)."Giant and switchable surface activity of liquid metal via surface oxidation".Proceedings of the National Academy of Sciences.111(39):14047–14051.Bibcode:2014PNAS..11114047K.doi:10.1073/pnas.1412227111.PMC4191764.PMID25228767.
  19. ^Liao, Jiahe; Majidi, Carmel (2022)."Muscle-Inspired Linear Actuators by Electrochemical Oxidation of Liquid Metal Bridges".Advanced Science.9(26): 2201963.doi:10.1002/advs.202201963.PMC9475532.PMID35863909.
  20. ^Liao, Jiahe; Majidi, Carmel; Sitti, Metin (2023)."Liquid Metal Actuators: A Comparative Analysis of Surface Tension Controlled Actuation".Advanced Materials.36(1): 2300560.doi:10.1002/adma.202300560.hdl:20.500.11850/641439.PMID37358049.
  21. ^"What is an LMT?".www.astro.ubc.ca.Retrieved2024-10-02.
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