Effect of flame temperature on the microstructure and oxidation reactivity of soot particles

The effect of flame temperature on the microstructure and oxidation reactivity of soot particles in premixed methane/oxygen flames at the same fuel-air equivalence ratio were studied by the high resolution transmission electron microscopy(HRTEM), Raman spectrum, and thermogravimetric analysis. The HRTEM results show that the mean fringe length, separation distance and fringe tortuosity fall in the range of 0.651-0.979 nm, 0.351-0.402 nm and 1.191-1.425 respectively. With the increase of flame temperature, the mean fringe length increases while the fringe tortuosity and separation distance decrease. The values of IG/ID received from Raman spectrum rise with the flame temperature, which range from 1.017 to 1.177. These results indicate that the microstructure gradually becomes more ordered and graphitic and the activation energy increases, ranging from 124.65 to 154.38 kJ/mol with the increase of flame temperature. There is a close relationship between microstructure and oxidation reactivity and more orderly and graphitic microstructure could lead to higher activation energy and lower oxidation activity. ©, 2015, Tianjin University. All right reserved.