Exceptional mechanical performance and macroscale superlubricity enabled by core-shell-like MoS2/B4C film

Abstract

Molybdenum disulfide (MoS₂) films are widely deployed in industrial applications owing to their inherent interlayer slip characteristics, offering energy consumption savings and prolonged mechanical part performance. Nevertheless, their practical utility is limited by environmental constraints and the limitations of preparation techniques, which hinder the attainment of robust superlubricity (friction coefficient < 0.01). Herein, through magnetron sputtering technology, we synthesize a core-shell-like nanocomposite composed of MoS₂ nanosheets encapsulating B₄C. The core-shell-like structure enables the resulting films to preferentially grow crystalline MoS₂, providing them with outstanding mechanical properties and efficient lubrication over a wide range of temperatures. Remarkably, such film achieves robust macroscale superlubricity and an ultralow wear rate (1.7 × 10⁻⁸ mm³ N⁻¹ m⁻¹) under high contact stress in a mild vacuum environment. This noteworthy outcome is primarily attributable to the self- segmentation of the macroscale contact interface during the friction process, involving: (1) a large amount of wear debris is embedded into the wear track to create extensive micro-sized asperities; (2) a nanolayer of amorphous carbon enriched with oxide nanoparticles is formed on the uppermost part of these asperities; (3) numerous incommensurate nanocontacts comprising nanoparticles and highly oriented MoS₂ nanosheets are established, culminating in the achievement of robust superlubricity. Our pioneering design, coupled with the elucidation of the underlying superlubricity mechanism, holds significant promise for advancing the development of robust and high performance lubricants.