Effects of carbon nano onions on the tribological performance of food‐grade calcium sulfonate complex grease

To improve the lubricity of the as‐prepared food‐grade calcium‐based grease, the effects of nano‐additive carbon nano onions (CNOs) on the tribological properties are systematically investigated using a ball‐disc wear tester. The properties of CNOs‐containing food‐grade calcium sulfonate complex greases (CSCG‐FG) were characterised by thermogravimetric analyser, rheometer and electrochemical workstation, Listeria monocytogenes, X‐ray photoelectron spectrometer and Raman spectrometer. The results revealed that pure and CNOs‐containing CSCG‐FG were proved to be safe. The average coefficient of friction (aCoF) and wear volume of the disc at CSCG‐FG of 0.10 wt% CNOs were the minimal values, which were 31.4 and 70.0% less than that of pure CSCG‐FG at 25°C and greatly lower than that of similar commercial food‐grade grease. At high temperature, CNOs‐containing CSCG‐FG had lower aCoFs and torques. CSCG‐FG of 0.10 wt% CNOs would be most possibly used in engineering applications and the results will provide valuable insight into developing food‐grade lubricants.