Effects of Magnetic Fields on Morphology and Nanostructure Evolution of Incipient Soot Particles from n-heptane/2,5-dimethylfuran Inverse Diffusion Flames

Abstract

Differences of the morphology and nanostructure evolution of incipient soot particles generated in n-heptane/2,5-dimethylfuran (DMF) inverse diffusion flames (IDFs) with/without magnetic fields were investigated. Utilizing a high resolution transmission electron spectroscopy, the morphology and nanostructures of soot sampled from spatial locations at different heights in IDFs were analyzed. The graphitization and the oxidation reactivity of soot were tested by an X-ray diffraction and a thermogravimetric analyzer, respectively. Results demonstrated that the magnetic force on paramagnetic species, such as oxygen molecules, can modify the soot formation and oxidation. More incipient soot particles with larger diameters appeared in chains or branches or tufted forms on the flame wing region and the higher position than that on the flame centerline region and the lower position. With magnetic fields, greater amounts of clustered soot particles displayed more crowded distribution and larger diameters. Soot particles with typical structures of the core-shell were promoted to own more orderly bordered lamellae with longer fringe length and smaller fringe tortuosity by the magnetic force acting on oxygen at the same sample position. These modifications resulted in relatively larger diffraction angle of the peak, higher graphitization degree and slightly lower oxidation reactivity of soot.