Black phosphorus (BP) nanosheets were synthesized through high-energy ball milling and liquid-phase exfoliation. The impact of BP on the tribological characteristics of castor oil (CO) was evaluated by using a four-ball test. The lubrication and extreme pressure performance of oil-based lubricants containing various mass fractions of BP nanosheets were examined in steel/steel frictional pairs, with the results compared to pure CO. Experimental results demonstrate that BPNS significantly fortifies the load-carrying capacity and antiwear resistance of the base oil, achieving a 43% reduction in friction and an 83% decrease in wear volume, alongside a 54% increase in extreme pressure performance. Molecular dynamics simulations revealed that when BP was introduced into the system, the friction force decreased by 44.4%. These enhancements are primarily attributed to the formation of the tribo-chemical layer consisting of iron oxides (Fe2O3, Fe3O4) and POx/P–O–C and the physical adsorption film on the worn surface. The interlayer shear properties of BP nanosheets also contribute significantly to reducing friction and mitigating wear.
Lv et al. (Mon,) studied this question.