Loss and Recovery of Nano-MoS 2 Lubricity in Carbon Soot Contaminated Polyalphaolefin

Carbon soot (CS) is a contaminant of engine oil, and the interaction between CS and oil additives should be understood. This work investigated the interaction between CS and nano-MoS 2 . Results show that adding 0.5% nano-MoS 2 in polyalphaolefin significantly improved the lubricity. However, the lubricity of nano-MoS 2 unexpectedly disappeared after adding 0.5% CS because CS prevented nano-MoS 2 from forming a tribofilm. Interestingly, the lubricity was mostly recovered by ZDDP, which removed the inhibition of CS by helping form a MoS 2 -contained tribofilm. Another method was also found to remove the inhibition without the help of ZDDP, that is, replacing nano-MoS 2 with nano-MoS 2 /nano-TiO 2 heterostructures. Nano-TiO 2 was immune to soot and could carry nano-MoS 2 into the friction interface by their heterojunction to synergistically form a tribofilm. Graphical abstract