Investigate on preparation and dry tribological behaviors of onion-like carbon/MoS2 polyimide coatings

The development of biomass materials can effectively mitigate the scarcity of energy and minimize resource waste. In this work, onion-like biomass carbon nanoparticles (OLCs) were prepared using rice husk ash (RHA) which was subjected to a high-temperature graphitization reaction catalyzed by iron nitrate. OLCs/molybdenum disulfide (MoS₂) composite particles were prepared and incorporated into polyimide (PI), and a composite coating of OLCs/MoS₂/PI with excellent tribological properties was successfully prepared. The tribological properties of coatings were evaluated using a controlled atmosphere tribometer (WMT-2E) under dry friction conditions. The related friction and wear mechanism of PI coatings including particles was clarified by the SEM/EDS, XPS, HRTEM and DFT theory. Results show that the wear rate of the three composite coatings of polyimide with OLC, MoS₂, and OLC/MoS₂ particles were reduced by 52.9 %, 48.2 %, and 58.1 %, respectively. For the coefficient of friction, PI-0.20 OLC/MoS₂ coating material decreased by 16.1 %. Anti-wear and friction reduction mechanism is attributed to the presence of a transfer film on the surface of the steel balls. The addition of MoS₂ facilitated the deposition of nanoparticles, which further improved the stability and densification of the friction film, resulting in better protection of the metal surface against severe wear. Besides, the component structure changes of OLCs and MoS₂ and adsorption energy of friction products on the surface of tribo-pairs were also important reasons for clarifying the modification tribological behavior of PI coatings including three kinds of nanoparticles.