Influence of Engine Age on Morphology and Chemistry of Diesel Soot Extracted from Crankcase Oil

In this study, the role of engine age on the structure and chemistry of crankcase soot was studied using X-ray diffraction, high-resolution transmission electron microscopy, energy-dispersive spectroscopy, and Raman spectroscopy. Results indicate that the basic structure of the carbonaceous species remains the same in all cases and is composed of turbostratic carbon. However, there are some very subtle changes in the structure of the soot as the age of the engine increases. Older engines have a greater proportion of non-crystalline amorphous carbonaceous constituents in the soot relative to newer engines. In addition, the wear-induced debris increase with the age of the engine, with a larger proportion of phosphates of Ca and Zn as well as sulfates of Ca in the soot of older engines. The presence of these wear debris particles incorporated in the soot extracted from the crankcase indicates that they arise from three-body abrasive wear between the soot and the tribofilms formed within the engine.