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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]

MXene has tremendous potential for enhancing thermal and tribological properties of fabric composites. Yet, its susceptibility to stacking and weak interfacial adhesion in organic matrix impedes practical application. Herein, MXene-h-BN hybrids were successfully achieved utilizing facile thiol-ene click reaction to introduce hexagonal boron nitride onto the surface of MXene to construct unique hierarchical structure. h-BN is grafted onto MXene through covalent bonding, effectively boosting interfacial adhesion and dispersion in the resin matrix. The layered MXene-h-BN possesses good lubrication behavior, and h-BN can increase strength and thermal conductivity of the MXene support skeleton. The results demonstrate that the thermal conductivity, tensile and bonding strength of reinforced fabric composites are elevated by 43.28%, 34.25% and 43.75% compared with pure fabric composites, respectively. Additionally, the wear rate of reinforced fabric composites is significantly decreased by 63.44%. This paper will contribute a novel and prospective reinforcement design strategy for click reaction constructed nano-materials in tribology. • h-BN was efficiently and promptly grafted onto the surface of MXene through the thiol-ene click reaction. • The structure of 3D point plane network was constructed. • The thermal conductivity, tensile and bonding strength of fabric composites are enhanced by 43.28%, 34.25% and 43.75%. • The reinforced fabric composites create robust tribofilm and wear rate is reduced by 30%. [ABSTRACT FROM AUTHOR]

The PEEK fabric-reinforced polyimide resin containing microcapsules with excellent mechanical and lubrication properties is reported. The GO-COOH/TiO 2 @PAO double-wall microcapsules (Capsule) were prepared by interfacial condensation polymerization of titanium butoxide (TBT) and self-assembly between GO-COOH and TiO 2 shell. A double crosslink of chemical bond (amide or ester) and hydrogen bond were constructed between microcapsules and polyimide (PI) to improve the mechanical properties of PEEK fabric-reinforced polyimide resin (PEEK/PI). It was identified that the addition of Capsules induced a 12.98% decrease in friction coefficient and 56.85% in the wear rate of the composites. This superior frictional behavior was primarily attributed to the combined effect of the boundary lubrication of PAO6, load-bearing effect of TiO 2 and PEEK fabric, and friction-reducing of GO-COOH. • Developed a novel containing oil microcapsules applied in lubrication. • The chemical bond and hydrogen bond was constructed between microcapsules and polyimide. • The microcapsules demonstrate good lubrication. • Regular fluctuations were observed in the friction curve of the samples containing microcapsules. [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]

Sodium dodecyl sulfate (SDS) and 8-Hydroxyquinoline (8-HQ) intercalated layered double hydroxides (LDH) sheets were in-situ formed in MAO layer to prepare a composite coating (CI@LDH-MAO) on AZ31 magnesium alloy. This composite coating demonstrates commendable anti-corrosion performance, primarily attributed to the formation of LDH sheets and insoluble Mg(HQ) 2 compounds. The electrochemical impedance modulus of the composite coating surpasses that of the MAO coating by three orders of magnitude after immersion of 360 h. Concurrently, the CI@LDH-MAO composite coating exhibits exemplary tribological properties, characterized by a friction coefficient of approximately 0.19 and a wear rate of (11.5 ± 1.5)× 10−6 mm3/(N·m). This outstanding tribological performance can be ascribed to enhanced interaction of lubricants with the friction interface by 8-HQ and SDS anions. • 8-HQ and SDS anions intercalated LDH was in-situ formed in MAO coating. • The composite coating has excellent tribological and anti-corrosion performance. • The COF was reduced by > 80% and the wear rate was reduced by > 50%. • 8-HQ and SDS anions facilitated the interaction of lubricants with friction interface. [ABSTRACT FROM AUTHOR]

Developing high-performance fabric composites with comprehensive properties is of paramount importance to broaden their application areas. In this work, a novel technique was studied to enhance interfacial adhesion via the adsorption of the complex amphiphilic biopolymer protein onto the surface of PPS/PTFE fabrics. Additionally, WS 2 @Ti 3 C 2 nanohybrids with heterostructures were synthesized, and the distinctive hierarchical microstructure facilitated the multiple reinforcement of the fabric composites. The results suggest that the decoration of BSA offers reaction sites with the phenolic resin and enhances the interfacial performance. Compared to the pure hybrid fabric composites, the tensile and bonding strength of the reinforced hybrid fabric composites are increased by 35.91% and 68.51%. Moreover, the wear rate of the reinforced hybrid fabric composites is decreased by 59.3%. [Display omitted] • The WS 2 @Ti 3 C 2 nanohybrids with heterostructures were synthesized. • The complex amphiphilic biopolymer protein BSA adsorbed onto the surface of fabrics, which enhanced interfacial adhesion. • The tensile and bonding strength of the reinforced hybrid fabric composites increased by 35.91% and 68.51%. • The wear rate of the reinforced hybrid fabric composites was decreased by 59.3%. • The synergistic effects of bioprotein decoration and WS 2 @Ti 3 C 2 could create robust tribofilm on the steel counterpart. [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]

CoCrFeNiMn high entropy alloy (HEA) owns prominent strain hardening capacity and high tensile elongation but poor wear resistance. In present work, in-situ carbide/CoCrFeNiMn composites with excellent anti-wear properties were fabricated by a flake powder metallurgy route using graphene oxide (GO) and CoCrFeNiMn as original powders. As a result, the hard carbide phase, Cr 7 C 3 , is formed in the soft matrix via in-situ reaction at the GO/HEA interface, which leads to a dense distribution of small-sized Cr 7 C 3 and strong interfacial bonding of the composites. With the addition of 5 wt% GO, the microhardness is improved by 66.7% and the macroscopic wear rate is decreased by 78.3% as compared with CoCrFeNiMn HEA. Increased nano-scratch resistance indicates that the dense distribution of hard Cr 7 C 3 carbide and the strong Cr 7 C 3 -CoCrFeNiMn interfacial bonding play key roles to resist the plastic flow of the HEA matrix during friction and wear. This study may provide a pathway to improve the wear resistance of HEA for engineering applications. [ABSTRACT FROM AUTHOR]

In recent years, the development of high-performance fabric composites has attracted widespread interest, but the frictional heat accumulation of fabric composites under high-speed has resulted in frictional failure, which has hindered the application of fabric composites. To remedy this deficiency, inspired by multilayer structure of fish scales, biomimetic MXene derivative DOPO-HQ-IPTS@Ti 3 C 2 T x was manufactured in situ, which boosted interfacial compatibility with MXene and provided remarkable enhancement in terms of mechanical performances and tribological properties of fabric composites. The tensile strength of reinforced fabric composites is enlarged by 45%. In addition, the wear rate of the reinforced fabric composites is reduced by 77%. Hence, the biomimetic nanomaterial DOPO-HQ-IPTS@Ti 3 C 2 T x offers a simple and dependable method for obtaining fabric composites with superior overall properties. [Display omitted] • The plywood-like biomimetic MXene derivatives (DOPO-HQ-IPTS@Ti 3 C 2 T x) were successfully fabricated. • The scale-spine like DOPO-HQ-IPTS was embedded on Ti 3 C 2 T x , which boosted the compatibility of Ti 3 C 2 T x. • The tensile strength of the reinforced fabric composites was enlarged by 45% compared to the pure fabric composites. • The wear rate of the reinforced fabric composites was reduced by 77%. • The incorporation of DOPO-HQ-IPTS@Ti 3 C 2 T x could create a homogeneous and firm tribofilm on the steel counterpart. [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]

Effect of Si addition on the high temperature tribological properties of TiZrV 0.5 Nb 0.5 refractory high entropy alloy was systematically studied. The results demonstrate that Si-microalloying affects the tribological properties by modulating the evolution of tribo-layer. Si-microalloying produces local tribo-layer with strong wear resistance by increasing the sintering rate of wear debris below 600 ℃, ultimately significantly reducing the coefficient of friction and wear rate. At 600 °C, Si-microalloying deteriorates the wear resistance due to the stress concentration at hard particles leading to accelerated fracture of the tribo-layer which hinders the formation of continuous protective tribo-layer. The enhanced tribological properties at 800 °C are attributed to the synergistic effect of suppressed oxide volatilization and rapid oxidation behavior ensuring continuous dense tribo-layer formation. • The high temperature tribological properties of TiZrV 0.5 Nb 0.5 Si x RHEA was studied. • The evolution of the tribo-layer plays a crucial role in the wear process. • The sintering rate of debris determines the formation of tribo-layer below 600 ℃. • A continuous and dense tribo-layer was formed for the Si0.3 alloy at 800 °C. [ABSTRACT FROM AUTHOR]

WS 2 films with duplex-layer structure were deposited by magnetron sputtering. The tribological differences of as-deposited, AO-irradiated WS 2 films and WS 2 /P201 hybrid system were mainly investigated for the same film. In comparison with as-deposited WS 2 film, AO-irradiated WS 2 film exhibits the lower initial friction coefficient and lower wear rate, and longer service longevity. Meanwhile, WS 2 /P201 hybrid system significantly extended service life further. It is found that the generated WS 2 debris act as lubricating agent with different participation states and air isolation in the different lubricating systems affect the tribological property of WS 2 film. Eventually, different lubrication mechanisms for AO-irradiated WS 2 film and WS 2 /P201 hybrid system in vacuum were revealed. [ABSTRACT FROM AUTHOR]

Inheriting the advantages of bulk metallic glasses (BMGs) and high entropy alloys (HEAs), high entropy bulk metallic glasses (HE-BMGs) have sparked great interest in recent years. In this work, the evolutions of structural heterogeneity, thermal stability and mechanical property of the TiZrHfCuBe HE-BMG with minor Sn addition were characterized, and the corresponding tribological properties under different normal loads and frequencies were investigated. The results showed that minor Sn addition can significantly enhance wear resistance of the HE-BMG by improving its structural heterogeneity and mechanical properties in a rather limited composition range. When excessive Sn is added, plentiful crystal particles are precipitated in the amorphous matrix, and the wear mechanism of the HE-BMG changes from slight abrasive and oxidation wear to severe fatigue and oxidation wear, leading to dramatically declined wear resistance. These findings would provide guidance for the development of advanced HE-BMGs with unique properties. • A rather limited Sn addition could enhance mechanical properties and wear resistances of (TiZrHfCuBe) 1- x Sn x HE-BMGs. • Declined wear resistance of the (TiZrHfCuBe) 0.97 Sn 0.03 was caused by the excessive Sn addition. • The wear mechanisms of (TiZrHfCuBe) 1- x Sn x HE-BMGs change from abrasive and oxidation wear to fatigue and oxidation wear. [ABSTRACT FROM AUTHOR]

High-temperature self-lubricating nickel-alloy based composites with Ag and three amounts of BaF2/CaF2 eutectic were prepared by hot press sintering technique. Both the composites with 5wt% and 10wt% BaF2/CaF2 eutectic exhibited markedly higher strength than 15wt% composite. The friction coefficient of the three composites was comparable. All three composites showed the highest wear rate at 600°C, but very lower at 800 and 900°C. The friction coefficient of the three composites was slightly lower as sliding against Si3N4 than Inconel 718. The friction and wear mechanism was proposed. [ABSTRACT FROM AUTHOR]

Abstract: The anti-wear and antioxidant behaviors of 2,2,6,6-tetramethyl-1-piperidinooxy (TEMPO) and its derivatives were studied. The tribological properties of lubrication oils with or without the addition of TEMPOs were investigated on an Optimol SRV IV oscillating friction wear tester and the oxidative stability was evaluated by RBOT test using SH/T-0193 and ASTM D2272 procedures. The results showed that the addition of TEMPOs can improve the antiwear and antioxidant behaviors of lubrication oils remarkably. Moreover, the addition of TEMPOs can improve the performance of lubrication oil under atomic oxygen radiation. [Copyright &y& Elsevier]

Abstract: The high-temperature tribological behaviour of Fe–28Al–5Cr alloy and its composites containing TiC was investigated against a Si3N4 ceramic from 25 to 800°C. The high-temperature wear resistance of the materials was significantly improved by the addition of TiC, which was attributed to the high hardness of the composites, as well as the support role of hard TiC. The oxidation played an important role to friction and wear. [Copyright &y& Elsevier]

Abstract: Bronze–graphite composites containing 8.4∼15wt% of Ni-coated graphite were fabricated by P/M method. The tribological properties were investigated under sea water condition. The friction coefficient of composites decreased with increasing graphite content. The wear resistance was improved by the addition of Ni-coated graphite but degraded at high graphite content. The results indicated that bronze–nickel coated graphite composites showed much better tribological properties in comparison with bronze and bronze–uncoated graphite composites. The composite with 11.7wt% nickel coated graphite showed the best tribological properties. The addition of nickel coated graphite not only increased the mechanical properties, but improved tribological properties. [Copyright &y& Elsevier]

Abstract: The paper reports the dry-sliding tribological behavior of Fe100−x –Ni x (x=20,23,25,30) alloys with various martensite fractions. For all the alloys, the friction coefficient decreased with increasing applied load and increased with increasing sliding speed, but there was nearly no difference between the different alloys. The wear rate of the alloys increased with increasing applied load and decreased slightly with increasing sliding speed. Microstructures had great influence on the wear behavior of these alloys. The Fe77Ni23 alloy with well-proportioned martensite exhibited the best wear resistance. [Copyright &y& Elsevier]

Abstract: The Ni3Si–Cr7C3 composite coatings with various contents of Cr7C3 were deposited on the AISI 1020 steel substrate by self-propagating high temperature synthesis casting and their tribological performances were studied under water and acid environments. The results demonstrated that all the Ni3Si–Cr7C3 composite coatings showed excellent friction-reduction, and wear resistance performances compared to the substrate and the AISI 321 stainless steel. While it is worth noting that the coating containing 37.2wt.% of Cr7C3 exhibited the best tribological performances. In addition, the friction reduction and wear resistant mechanism was also discussed and considered to be microploughing under both water and acid environments. [Copyright &y& Elsevier]

Abstract: High temperature self-lubricating composites Ni3Al–BaF2–CaF2–Ag–Cr were fabricated by powder metallurgy technique. In this paper the effect of Cr content on tribological properties at a wide temperature range starting from room temperature to 1000°C was investigated. It was found that Ni3Al matrix composite with 20wt% Cr exhibited low friction coefficient of 0.24–0.37 and a wear rate of 0.52–2.32×10−4 mm3 N−1 m−1. Especially at 800°C it showed the lowest friction coefficient of 0.24 and a favorable wear rate of 0.71×10−4 mm3 N−1 m−1. This implied that 20wt% Cr was the optimal Cr content and its excellent tribological performance could be attributed to the balance between strength and lubricity. [Copyright &y& Elsevier]

Abstract: The tribological behaviors of Babbitt alloy 16-16-2 sliding against aluminum bronze ZCuAl9Mn2 lubricated by sea water were systematically investigated in this paper. The results indicated that the friction coefficient decreased as the load increased to 30N and then remained at a steady level at high loads, but decreased with increase in sliding speed. The wear rate increased with load, but decreased with sliding speed. The formation of basic lead carbonate Pb3(OH)2(CO3)2 during the sliding process played a critical role in the remaining low friction coefficient in sea water. [Copyright &y& Elsevier]

Cr-doped graphite-like carbon (Cr-GLC) coatings and Cr-doped diamond-like carbon (Cr-DLC) coatings were prepared by PVD and PECVD, respectively. The lubrication behaviour of the solid-liquid composite lubrication systems was investigated using two ionic liquids (ILs) as lubricants. The results show that the friction coefficient was reduced by approximately 40% compared with that under the dry condition, and the composite system exhibited a good synergistic lubrication effect. The Cr-DLC coating showed better tribological behaviour than the Cr-GLC coating, which can be ascribed to a better physicochemical film formation under friction and the compact microstructure of the Cr-DLC coating. The synergistic effect of the composite systems was affected by the viscosity and corrosiveness of the ILs and the microstructure of the coatings. Image 1 • The Cr-GLC and Cr-DLC coatings were prepared by PVD and PECVD method, respectively. • The friction coefficient decreases from 0.11 (dry condition) to 0.045–0.06 (ILs condition). • The lubrication of solid-liquid systems is mainly affected by the wettability of ionic liquids. • The tribological properties of Cr-GLC in ionic liquids are more affected by the corrosion effect. [ABSTRACT FROM AUTHOR]