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Ga‐based liquid metal (GLM) can be used as a current‐carrying lubricant, due to its combination of excellent electrical conductivity and good lubricity. However, the influence of electric field parameters on the lubrication mechanism of GLM is still unclear. This paper attempts to investigate the influence of current magnitude, voltage magnitude, current direction, and load on the lubrication behaviors of GLM at atmosphere and room temperature (≈26 °C). It is found that the interface action mechanism induced by an electric field is mainly reflected in four aspects, namely, Joule heating effect, electric field force, electrochemical effect, and electromigration effect. These interfacial physical and chemical effects are governed by the current magnitude, voltage magnitude, current direction, and load, bringing about distinct frictional products and thereby influencing the lubrication behaviors. Briefly, FeGa3 can only be formed when the current reaches 6 A and the load is above 40 N, and it has obvious friction‐reducing properties, but increases the wear due to its low content. When the frictional product is just the Ga‐rich film, the increase of oxidation degree is detrimental to the wear resistance. [ABSTRACT FROM AUTHOR]

The PEIS-functionalized PMPC-GLM microgel-based (PEIS-Gel@PMPC-GLM) hydrogels exhibited satisfactory antibacterial and durable antifouling properties, as well as certain self-healing performance. [Display omitted] • Zwitterionic polymer cross-linked liquid metal microgels-based hydrogels were successfully prepared. • The as-prepared hydrogels have preferable mechanical properties to the original hydrogels. • The hydrogels exhibit excellent antibacterial and antifouling properties under various conditions. • The as-prepared hydrogels show certain self-healing performance. Hydrogels are a promising new class of antifouling materials. But their utility is constrained by low mechanical strength and unsatisfactory antifouling performance over the long term. Herein, we successfully prepared zwitterionic polymer PEIS cross-linked gallium-based liquid metal microgels-based (PEIS-Gel@PMPC-GLM) hydrogels via UV-curing and amidation reaction. The as-prepared hydrogels showed preferable mechanical properties and superior hydrophilicity to the original hydrogels. The PEIS-Gel@PMPC-GLM hydrogels could prevent the adhesion of more than 90 % of microalgae and nearly 100 % of bacteria in a short-term antifouling test. PEIS-Gel@PMPC-GLM hydrogels also performed exceptionally well in the high concentration antibacterial test and the long-term antifouling test (remove more than 90 % bacteria and 80 % microalgae). In addition to releasing a high concentration of gallium ions, as shown by the ICP-OES test, PEIS-Gel@PMPC-GLM hydrogels also exhibited excellent lubrication performance, as demonstrated by the friction test (coefficient of friction as low as 0.023). Therefore, the antifouling effect of gallium ions combined with the strong hydration ability of the surfaces endowed the hydrogels remarkable antibacterial and antifouling properties. As a result of the exposed gallium atoms inducing further crosslinking of residual vinyl monomer in hydrogels, PEIS-Gel@PMPC-GLM hydrogels revealed certain self-healing performance. [ABSTRACT FROM AUTHOR]

Supramolecular gelator functionalized liquid metal (Gelator@GLM) exhibited excellent tribological properties due to the synergistic effect of GLM nanodroplets and the gel generating protective film. [Display omitted] • Supramolecular gelator functionalized liquid metal nanodroplets were prepared by self-assembly and radical polymerization. • The Gelator@GLM nanodroplets displayed effective anti-wear and friction reduction properties as lubricant additives. • The lubrication performance is attributed to the synergistic effect of GLM nanodroplets and the gel generating protective film. In this work, dopamine n -butenylamide (DBA) modified GLM nanodroplets were prepared via directional ultrasound of bulk liquid metal in ethanol aqueous solution as well as DBA self-assembly, followed by grafting with urea-based gelators via radical polymerization to obtain GLM-based supramolecular gelators (Gelator@GLM). The grafting gelators can impart their good compatibility between the GLM nanodroplets and the base oil, so that the Gelator@GLM nanodroplets can be dispersed in the base oil uniformly and stably for more than 3 weeks. Meanwhile, the tribological properties of Gelator@GLM nanodroplets was significantly enhanced, with a reduction of coefficient of friction (COF) and the wear volume of 41.18% and 92.13%, respectively, when compared with the base oil. Furthermore, Gelator@GLM additives exhibited stable lubrication performance even under variable temperature and frequency conditions. The synergistic effect of GLM nanodroplets and the gels generating a physical adsorption film and a chemically protective film (containing iron and chromium oxides, nitrides and carbides) can be credited with the improved tribological performance. [ABSTRACT FROM AUTHOR]

Gallium-based liquid metal (GLM) has excellent extreme-pressure properties, but at low sliding speeds, it is typically in a boundary or mixed lubrication, causing poorer properties compared to traditional lubricants. In this paper, GLM/P composite lubricants composed of GLM particles and polydimethylsiloxane are prepared. Under a maximum-Hertz-stress of 0.69 GPa, GLM/P2–30% (viscosity of 1260 mPa∙s) can enter the elastohydrodynamic lubrication (EHL) regime at 0.2 m/s, has good EHL properties (friction coefficient of 0.06, wear rate in the order of 10−9 mm3/N·m). Meanwhile, it has high extreme-pressure properties (P B of 2300 N). The EHL film is formed mainly by polydimethylsiloxane, while GLM particles increase the thermal conductivity of lubricant and can be adsorbed on the frictional interfaces, thereby improving the EHL properties. [Display omitted] • GLM/P composite lubricant can enter the elastohydrodynamic lubrication regime under conventional load and low sliding speed. • Lubrication regimes and transition laws of GLM/P are determined by combining Stribeck curve with lubrication film thickness. • The lubrication mechanisms of GLM/P in elastohydrodynamic lubrication regime are revealed in detail. [ABSTRACT FROM AUTHOR]

Ga-based liquid metals have promising applications as coolants and lubricants in the computer science, medical, and nuclear industries. In this paper, soft metal Cu was used as an additive to improve the lubricating performance of Ga-In-Sn. CuGa 2 phases were in-situ generated. At room temperature (RT, 25 °C) and 150 °C, GC0.2 and GC0.5 (Ga-In-Sn doped with 2 wt% and 5 wt% Cu) exhibited significantly better lubricating properties than Ga-In-Sn. At 150 °C, the wear rate of T91 steel lubricated by GC0.2 was 72.95% lower than that lubricated by Ga-In-Sn. At 300 °C, GC0.2 maintained a similar lubricating performance to that of Ga-In-Sn. The lubrication mechanism showed that the change in lubricant characteristics and friction film were the main factors to improve the lubricity. • Novel Cu-doped gallium-based liquid metals were successfully prepared. • CuGa2 phases could be in-situ generated in Cu-doped liquid metal. • GC0.2 exhibited outstanding lubrication performance at RT∼300 °C. • The change of lubricant characteristics and friction film improved the lubricity. [ABSTRACT FROM AUTHOR]

Gallium-based liquid metals (GLMs) are a novel high-end lubricant with low friction coefficient and excellent load-carrying capacity. This paper aims to improve the lubrication properties of GLMs by regulating the frictional interfaces. Six types of GLMs doped with Zn, Mg, Bi, Cu, Ti, or Sc elements are prepared respectively, and the effects of metal element doping on the lubrication behaviors and mechanisms for AISI 440C steel self-mated pairs are investigated in the mixed lubrication regime with a ball-on-three-plate setup. Doping 1 wt% Zn or Cu elements can improve the lubrication properties, with the friction coefficient reduced by 20.3 % and the wear rate reduced by 55.1 % compared with those under eutectic Ga/In/Sn lubrication. However, doping Ti, Sc, Mg, or Bi all reduce the lubrication properties. Doping Zn improves the lubrication properties of GLMs by promoting the adsorption of gallium on the frictional interfaces. Conversely, doping Bi inhibits the adsorption of gallium. The improvement in the lubrication properties of Cu-doped GLM is attributed to the formation of low-hardness CuGa 2 particles. The doping of Ti or Sc generates high-hardness TiGa 3 or ScGa 3 particles, causing three-body abrasive wear. The doping of Mg generates a large number of Mg 2 Ga 5 particles, seriously disrupting the stable lubrication. [Display omitted] • The influence of six types of metal doping on the phase composition of GLM is elucidated. • Doping Zn can promote the adsorption of gallium, thereby improving the properties, while doping Bi has the opposite effect. • The effects of the hardness of intermetallic compounds generated by metal doping on the frictional interfaces are summarized. [ABSTRACT FROM AUTHOR]

Lead-bismuth eutectic liquid metal (LBE) is the primary coolant for the advanced liquid-metal nuclear reactor, and clarification of its lubrication behavior and mechanism at elevated temperature is of importance. In this paper, a self-mated high-temperature steel sliding-pair and a pin-on-disc configuration are selected to evaluate the lubrication behaviors of LBE at 250 °C and 400 °C under argon atmosphere. It is found that LBE possesses an excellent lubricity proofed by the low friction coefficient of 0.1 and the wear rate of 10−6 mm3/Nm for the steel discs. Close inspection on the friction interfaces indicates that the worn surfaces of the steel discs are covered by a smooth tribo-film consisting of Bi, Pb 7 Bi 3 and the related oxides. • The high-temperature lubricity of Lead-bismuth liquid metal (LBE) for the nuclear coolant was studied. • LBE presents an outstanding lubricity for the high-temperature steel at 250 and 400 °C. • The formation of a Bi/Pb 7 Bi 3 /oxides self-lubricating tribo-layer provides the lubricity. [ABSTRACT FROM AUTHOR]

Ga-based liquid metal (GLM) may be a promising current-carrying lubricant due to its excellent conductivity and good lubricity. But the lubrication mechanism of GLM under current-carrying condition is unclear. This paper attempts to investigate the feasibility of GLM as a current-carrying lubricant at atmosphere and room temperature (RT, ∼26 °C). It is found that GLM can effectively lubricate the metal sliding-pairs, and can further dramatically reduce the wear rate in current-carrying condition. The current promotes the adsorption of Ga on the counterpart connected to the cathode and inhibits the oxidation of Ga on both sliding-pairs. The present finding provides a technical supporting for the application of GLM used as a current-carrying lubricant, and enriches the lubrication science of liquid lubricants. [ABSTRACT FROM AUTHOR]

Abstract Extreme pressure lubrication is a great challenge for many mechanical systems like bearings and gears. Here, an novel functional material based on Ga-based liquid metal has been applied to successfully lubricate the steel-ceramic sliding pairs at extreme high load (1500 N), which significantly outperforms other liquid lubricants like oil and ionic liquid. Ga-based liquid metal provides a low friction coefficient (0.11–0.23) and wear rate (10−8-10−7 mm3/Nm) of AISI 52100 steel disc (C 0.98-1.10 Mn 0.25-0.45 P ≤0.025 S ≤0.025 Si 0.15-0.30 Cr 1.30-1.60 Fe 96.5-97.32 , mass %; American Iron and Steel Institute standard) when it slides against Si 3 N 4 balls over a load range 100–1500 N. To elucidating these interesting results, the lubrication mechanisms of Ga-based liquid metal are studied by tribo-surface analysis. Highlights • Liquid metal (LM) provides a new strategy for lubricating the steel-ceramic pairs. • LM displays good lubricity and extraordinary load-bearing for steel-ceramic pairs. • This good property is due to boundary lubrication of LM and nano-scale Ga tribo-film. [ABSTRACT FROM AUTHOR]

Gallium-based liquid metal is a novel lubricant for high-end equipment due to its low friction coefficient and excellent load-carrying capacity. In this work, the stribeck curve, static friction and a series of fixed-speed friction tests for steel self-mated pairs under gallium lubrication are conducted to reveal the lubrication regimes and transition laws. In the sliding speed ranging from 10−8 to 1.4 m/s and the normal load ranging from 2 to 20 N, gallium can only provide boundary and mixed lubrication. Uniformly distributed or island-like distributed gallium-rich films are formed under boundary or mixed lubrication regimes, respectively. The different formation mechanisms are revealed. The failure of the gallium-rich film is mainly related to the average contact stress of the frictional interfaces. • The stribeck curve under gallium lubrication is reported. • The lubrication regimes and transition laws provided by gallium are clarified. • Two different formation mechanisms of the gallium-rich film formed under boundary and mixed lubrication regimes are revealed respectively. • The failure of the gallium-rich film is mainly related to the average contact stress of the frictional interfaces. [ABSTRACT FROM AUTHOR]

Ga-based liquid metal may be a novel coolant and lubricant for the steels at high temperature and extreme pressure in the nuclear reactor. It is recently reported that the formation of FeGa 3 film may be responsible for the good lubricity of liquid metal, but no proof can clarify this point and its wear behavior is unclear. Therefore, an in-situ FeGa 3 film was prepared through the hot-reaction between liquid Ga 65 In 22 Sn 13 (65% Ga, 22% In, 13% Sn by mass) and T91 steel at 600 °C in this paper. The results indicate that FeGa 3 film forms and bonds strongly to the steel surface. It has good mechanical and tribological properties at room temperature, but increases the wear at 600 °C. The finding provides the technical support for the safety service of the steels in the liquid-metal environment and is also a new strategy for protecting the steel. [ABSTRACT FROM AUTHOR]

Predicated on the marine bio-adhesion strategy, we herein assembled tannic acid (TA) in-situ onto Gallium-based liquid metal (GLM) nanodroplets surface effectuating the formation of poly(TA/PEI) adhesive layer with polyethyleneimine (PEI) via Schiff-base reaction and/or Michael addition to derive poly(TA/PEI)-functionalized GLM nanodroplets (GLM-PEI). Subsequently, the zwitterionic precursor triisopropylsilyl methacrylate (TISM) was bonded with the amine group of poly(TA/PEI) through aza-Michael addition for extracting TISM-functionalized GLM nanodroplets (GLM-TISM). The on-site hydrolysis of the as-prepared GLM-TISM into a zwitterionic group could be achieved by placing the zwitterionic precursor triisopropylsilyl TISM in an aqueous environment. Therefore, the synergy created by the bactericidal activity of GLM nanodroplets along with the strong surface hydration of the zwitterionic group contributes towards the remarkable antifouling performance of the GLM-TISM, which exhibits good dispersibility in polydimethylsiloxane (PDMS) elastomer coating and as functional filler to fabricate nano-composite coatings (PDMS@GLM-TISM). The as-obtained PDMS@GLM-TISM demonstrate excellent antifouling effect with the inhibition of bacterial and algae adhesion (removal of more than 96 % of bacteria and 77 % of algae) under the synergistic effect of liquid metal and zwitterionic groups. Furthermore, GLM-TISM nanodroplets can furnish the PDMS coating with self-repair ability by crosslinking the unreacted vinyl monomer of PDMS with the exposure to GLM to initiate polymerization. [Display omitted] • In situ generation of zwitterionic functionalized liquid metals (GLM-TISM) was successfully prepared by Michael addition. • The as-prepared GLM-TISM could be hydrolyzed in-situ into a zwitterionic group in aqueous environment. • The GLM-TISM nanodroplets based nanocomposite coating exhibits satisfactory antifouling and self-healing performance. [ABSTRACT FROM AUTHOR]

Herein, a bioinspired molecule-dopamine n-butenylamide-was self-assembled on Gallium-based liquid metal (GLM) nanodroplets to introduce vinyl group, and the zwitterionic poly (2-methylacryloxyethyl phosphocholine) (PMPC) was grafted onto GLM nanodroplets via surface-initiated free radical polymerization to obtain hybrid PMPC-GLM microgel. The as-prepared PMPC-GLM microgel has good dispersion stability in aqueous solution (chemical stability > 2 months), and shows excellent antibacterial properties due to the hydration of PMPC and antibacterial effect of Ga3+. Moreover, the hydration layer endows PMPC-GLM microgel with satisfactory tribological properties as an aqueous lubricant additive, with the COF and wear rate reduced by 65% and 62%. In addition to hydration lubrication, the improved tribological performance is attributed to the formation of protective film on the worn surface. [Display omitted] • Gallium-based liquid-metal Nanodroplets hybrid microgel (PMPC-GLM) was successfully prepared. • PMPC-GLM microgel exhibits good chemical stability in water (more than two months). • PMPC-GLM microgel shows excellent lubrication performance as an aqueous additive. [ABSTRACT FROM AUTHOR]