Synergistic effect on the tribological characteristics for coal‐to‐liquids soot modified by nitric acid and oleic acid

Abstract A self‐made soot capture device was applied to burn coal‐to‐liquids and collect its soot (CS), and then modified the CS with nitric acid or nitric acid and oleic acid to obtain nitric acid modified CS (CSN) or nitric acid and oleic acid modified CS (CSNO). The influence of CS, CSN and CSNO on the lubrication performance of 10 # white oil (WO) was investigated on a four‐ball tester. The structural difference, surface topography, element composition and tribological mechanism of the three types soot were analysed by Fourier transform infrared spectrometer, X‐ray photoelectron spectroscopy, scanning electron microscope, high resolution transmission electron microscope, and so on. From the obtained results, after further modification with oleic acid, the solubility of oil is significantly improved. Compared with 10 # WO, the average friction coefficient and average wear scar diameter of CS, CSN and CSNO are all reduced. Among them, CSNO has the best anti‐friction and anti‐wear effect. CSNO is expected to be used as carbon lubricating material from coal‐to‐liquids soot.