In Situ Friction-Induced Graphene Originating from Methanol at the Sliding Interface between the WC Self-Mated Tribo-Pair and Its Tribological Performance

Synergistic effects of hierarchical micro/nanostructures and PDMS/lubricant composites for superior tribological and wetting performance on aluminum

In this study, we propose a method to enhance the friction and wetting properties of aluminum surfaces with micro-/nanostructures by coating them with a PDMS/lubricant composite. Hierarchical micro/nanostructures were formed on the aluminum surface through an etching process, and coating solutions were prepared by mixing xylene and the PDMS/lubricant composites in various ratios. The surface morphology, roughness, and wettability of the coated specimens were analyzed, and their friction and wear characteristics were evaluated under dry and lubricated conditions. The results showed that the PDMS/lubricant composite coating significantly reduced friction and wear under both dry and lubricated conditions owing to the formation of a stable lubricating film. Additionally, the hierarchical micro/nanostructures formed by the etching process improved hydrophobicity and self-cleaning ability. The coated surface exhibited selective wettability towards water and oil, offering various advantages such as prevention of contamination, prevention of wear and performance degradation caused by lubricant oxidation, and enhanced corrosion resistance. The findings of this study are expected to contribute to the development of lightweight mechanical-component technologies with improved durability and wear resistance.

A fast and high-efficiency electrochemical exfoliation strategy towards antimonene/carbon composites for selective lubrication and sodium-ion storage applications

Two-dimensional (2D) layered antimony (Sb) materials are of importance due to their unique physicochemical properties, and they can be easily electrochemically exfoliated from bulk Sb in Na₂SO₄ electrolyte solution. However, the exfoliation yield is quite low and the exfoliated products are easily oxidized to Sb₂O₃, which prohibits their practical engineering applications. Herein, an antimonene/carbon composite is successfully fabricated with a high exfoliation yield through electrochemical exfoliation of bulk antimony chunk in a mixed electrolyte solution consisting of Na₂SO₄ and ethylene glycol. When the as-fabricated antimonene/carbon composite is added into PAO6 oil, the lubrication system exhibits a selective lubrication performance when sliding against GCr15 and YG8 ball, and the antiwear enhancement can be further improved by sliding against a YG8 ball. Besides, the antimonene/carbon composite can provide reliability and enough ion corridors during the charge/discharge processes. When tested as an anodic material for sodium-ion batteries, it exhibits a large capacity of 485.0 mA h g^-1 at a current density of 200 mA g^-1 after 150 cycles and a remarkable rate capability (334.5 mA h g^-1 at 5 A g^-1).

Achieving Ultralow Friction and Wear by Tribocatalysis: Enabled by In-Operando Formation of Nanocarbon Films

Under the high-contact-pressure and shear conditions of tribological interfaces lubricated by gaseous, liquid, and solid forms of carbon precursors, a variety of highly favorable tribocatalytic processes may take place and result in the in situ formation of nanocarbon-based tribofilms providing ultralow friction and wear even under extreme test conditions. Structurally, these tribofilms are rather complex and may consist of all known forms of nanocarbon including amorphous or disordered carbon, graphite, graphene, nano-onion, nanotube, etc. Tribologically, they shear readily to provide ultralow friction and protection against wear. In this paper, we review some of the latest developments in catalyst-enabled tribochemical films resulting from gaseous, liquid, and solid sources of carbon. Particular focus is given to the nature and lubrication mechanisms of such in situ derived tribofilms with the hope that future tribological surfaces can be designed in such a way to exploit the beneficial impact of catalysis in friction and wear control.

In situ Synthesizing Carbon-Based Film by Tribo-Induced Catalytic Degradation of Poly-α-Olefin Oil for Reducing Friction and Wear

Reducing friction and wear in a convenient and economical way has always been desired for industrial production. Here, a carbon-based film with excellent friction-reducing and antiwear abilities was formed in situ from the degradation of poly-α-olefin oil (PAO10) on the friction interfaces of the MoN/Pt coating sliding against the Si₃N₄ ceramic ball during the rubbing process. The MoN/Pt coating was prepared on stainless steel by direct current magnetron sputtering, in which an active 10 nm Pt layer grew well on the MoN layer. The MoN/Pt coating, lubricated by trace amounts of 5 mL PAO10 oil, exhibited a super low friction coefficient of 0.042 and an extremely low wear rate of 1.08 × 10^-8 mm³ (N m)^-1 after a long duration of applied friction under a high Hertz contact stress of 1.7 GPa. Raman spectra and transmission electron microscopy images revealed that the carbon-based film was composed of amorphous carbon phase dotted with sporadic Pt, MoO₃, and SiO₂ crystal phases. Molecular dynamics simulations illustrated that the MoN/Pt coating had catalytic action and resulted in the degradation of PAO10 during the rubbing process, which corresponded to the formation of the amorphous carbon-based film on the wear surfaces.