Novel Approach for Improved Tribological Behavior of Biodiesel Soot in Liquid Paraffin

To improve the tribological behavior of biodiesel soot (BDS) in liquid paraffin (LP), the order of biodiesel soot was increased through thermally oxidized treatment at 500 °C, and the oil solubility was then improved through a modification using oleylamine (OLA). The BDS and thermally oxidized oleylamine-modified BDS (T-BDS-OLA) were characterized through various methods including the use of TG, FETEM, Raman spectroscopy, FTIR, and a zeta potentiometer. The tribological properties and mechanisms of the BDS before and after the thermally oxidized treatment modification were investigated using a ball-on-disc reciprocating tribometer, FESEM, 3D laser-scanning microscopy, and Raman spectroscopy. The results showed that T-BDS-OLA has a higher degree of order than the BDS, with an onion-like microstructure. BDS and T-BDS-OLA can both improve the antifriction and antiwear properties of LP at a soot content of 0.1％–0.4％, while T-BDS-OLA in LP shows better antifriction and antiwear properties than BDS. The tribological mechanisms can be attributed to both types of soot acting as spacing and roll bearing between the friction surfaces. In addition, the exfoliated graphitic sheets from T-BDS-OLA can form a carbon lubrication layer providing easy sliding.