Experimental Study on the Effect of Partial Oxidation on the Microscopic Morphology of Soot Particles

Abstract

Diesel engine exhaust pipes are in a high-temperature and high-oxygen environment; the carbon soot formed by fuel combustion will be partially oxidized, and its physicochemical properties will change significantly after oxidation. In order to study the effect law of partial oxidation on carbon soot particles emitted from automobiles, commercial carbon black samples (Printex-U carbon) were selected to replace actual carbon soot particles in this paper, and experiments were conducted on a fixed-bed catalytic oxidation device to obtain carbon soot particles with four oxidation rates by varying the time duration of oxygen introduction. Subsequently, the microstructure images of the corresponding carbon soot particles were obtained using TEM and measured after image processing with ImageJ software. The results showed that the average particle size, particle layer spacing, and distortion of carbon soot particles gradually decreased with the increase in oxidation rate. Moreover, the basic particle edge structure of carbon soot particles gradually blurred, the disordered structure inside the carbon soot particles increased, and the structure was destroyed or oxidized away with the gradual oxidation of the outer layer. Lastly, the density degree inside the particles gradually increased, the outer carbon layer arrangement became more regular, and the graphitization degree gradually became larger. The oxidation of carbon soot particles followed the contraction model and the internal oxidation model.