High-temperature friction and oxidation resistance of self-sacrificial diamond-graphene heterostructures coatings

The inherent brittleness and lack of self-support capabilities of diamond and graphene limit their application in durable lubrication systems. However, pre-encapsulating flexible graphene on diamond coatings holds immense potential to balance brittleness with toughness in high-temperature friction applications. Herein, diamond-graphene heterostructure coatings with a semi-coherent interface, characterized by robust bonding interspersed with dislocation defects, were synthesized in situ using hot-filament chemical vapor deposition. Benefiting from the synergistic effects of enhanced interfacial strength and oxygen-trapping capabilities, these coatings demonstrated over 35 % improvement in friction performance across various temperatures. Experimental and computational analyses indicated that the robust interface facilitates energy transfer, allowing graphene to undergo elastic adjustment and stress dissipation in a self-sacrificial manner before the brittle diamond experiences catastrophic failure. Additionally, the engineered defects within graphene layers serve as preferential adsorption sites for oxygen atoms, creating a high-energy barrier against oxygen diffusion into the diamond interior. These results reveal the influencing mechanisms of interfacial strength and defect engineering on diamond-graphene heterostructure coatings, setting the stage for next-generation materials tailored for high-temperature friction applications.