Opportunity
Friction and wear are pervasive in mechanical systems, drastically reducing the efficiency and lifespan of modern technology. Approximately one quarter of global energy consumption and associated greenhouse gas emissions can be attributed to the relative sliding of engineering materials. Conventional solid lubricants such as soft metals, metal fluorides, and inorganic salts can lower the coefficient of friction (COF) to around 10⁻¹ by reducing interfacial shear strength. Advanced two-dimensional (2D) nanomaterials like graphene, MoS₂, h-BN, and 2D MXenes have pushed the boundaries of superlubricity, achieving COF values in the range of 10⁻² to 10⁻³. However, the superlubricity of these materials often degrades under extreme conditions, particularly high contact pressure and elevated temperature. There remains a critical need for solid lubricants that can maintain low friction and near-zero wear over a wide range of pressures and temperatures, especially in demanding applications such as automotive, aerospace, biomedical engineering, and microelectromechanical systems (MEMS). The present invention addresses this challenge by providing a tribological material that does not rely on incommensurate interfaces or specific crystal orientations, thereby offering isotropic tribological performance even under harsh operating conditions.
The invention provides a tribological material comprising a Ti-MXene composite with zero-dimensional (0D) nanostructures. Specifically, the 0D nanostructure is a 0D/0D heteronanostructure containing Ti nanocrystals and Ti₃C₂Tₓ-type MXene nanocrystals. The MXene nanocrystals are dispersed within the Ti nanocrystals and arranged to form interfacial chemical bonding with them. In some embodiments, the heteronanostructure further includes TiO₂ nanocrystals (rutile phase). The average grain size of the heteronanostructure is about 6 nm, and the material has an extremely smooth surface with a root-mean-square roughness of only 0.32 nm. The composite exhibits remarkable mechanical properties: Young's modulus of 115–145 GPa, yield strength of 5–6.4 GPa, and ductility of 26–34%. Technology
The fabrication method employs a polymer surface buckling-enabled exfoliation (PSBEE) process. A Ti layer is deposited onto a water-absorbing substrate (e.g., a dehydrated PVA gel on glass) by electron beam evaporation. During this step, the 0D/0D heteronanostructure forms in situ. The precursor is then immersed in water, causing the substrate to swell and buckle, thereby detaching the Ti-MXene composite as a freestanding nanomembrane with thickness tunable from 30 to 50 nm. This method yields large-area, ultra-smooth nanomembranes that can be transferred onto various engineering surfaces via van der Waals interactions.
The tribological mechanism is unique: under high pressure and temperature, MXene nanocrystals decompose, triggering carbon migration and the formation of nanoscale oxides (TiO₂) that provide tribochemical protection. At the same time, carbon segregation reduces friction. This combination of rapid nano-oxidation and carbon diffusion enables the material to repair wear tracks on the nanoscale, leading to near-zero wear and ultralow friction under extreme conditions (contact pressure up to 20 GPa, temperature up to 573 K). Density functional theory (DFT) and molecular dynamics (MD) simulations confirm that the low activation energy for oxidation (1.00 ± 0.24 eV) and the facilitated oxygen dissociation on unsaturated Ti oxides are key to the superior performance.
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