In situ nanocompression of carbon black to understand the tribology of contaminated diesel engine oils

The study has evaluated the role of soot, surrogated by carbon black (CB) experimentally, in affecting the performance of engine oils. It is very well known that the existence of soot in oil produces abrasive wear on contact surfaces. Other mechanisms influence the oil performance such as additives adsorption on soot and oil degradation due to the interactions with soot. Recent research has suggested the existence of another wear mechanism related to soot particles, which remains poorly understood. This study investigates the effect of soot interactions in engine oil on its mechanical properties. Carbon black particles (CBPs) were used in the experiments to simulate real soot in the engine. The microstructure and crystal structure of CBPs compared to real soot were investigated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). In situ compression of the single particle was conducted in a scanning electron microscope (SEM) to evaluate the mechanical properties of fresh and aged CBPs with different sizes. The results show that aged CBPs are significantly harder than fresh CBPs, indicating that ageing in oil modifies the turbostratic crystal structure of CBPs and alters its mechanical properties, potentially affecting tribological performance.