Development of nano biochar as a lubricating oil additive for tribological applications

Nano-materials, given their excellent anti-friction and anti-wear characteristics, have attracted significant attention in tribological applications. However, conventional nano-materials have difficulty meeting the development requirements of the eco-friendly lubricants. In this study, nano biochar derived from sesame stalk was synthesized and used as a lubricant additive in poly-alpha olefin-6 (PAO6). The tribological properties were evaluated by four ball tribological tests with steel and ceramic balls as the friction pair. Following the friction experiment, the worn surface on the steel ball was analyzed by X-ray photoelectron spectrometry. The steel ball friction results showed that the lubricants containing 0.2 wt% nano biochar achieved a maximum wear volume reduction of 46% compared to PAO6, and the friction coefficient decreased by 34.6% for the ceramic balls. Analysis indicated that the enhanced wettability of nano biochar lubricant contributed to improving the anti-wear properties. Characterization of the worn surface revealed that the addition of nano biochar facilitated the formation of strong Fe3O4 tribofilms. This study demonstrated that nano biochar could serve as an environmentally friendly additive in the liquid lubricant industry.