Flame propagation characteristics and combustion mechanism of FeOOH-coated zirconium particles

Abstract

Zirconium (Zr) particles are coated with ferric oxyhydroxide (FeOOH) nanoparticles to form a core–shell structure, and this process alters the combustion performance of the zirconium particles. This study explored the flame propagation characteristics and combustion mechanism of FeOOH-coated zirconium particles. A high-speed observation system was used to reveal the flame propagation velocities and temperatures, and scanning electron microscopy, thermogravimetry (TG), and X-ray diffraction were used to examine and elucidate the combustion mechanism of FeOOH-coated zirconium particles. The results showed that when the concentration was increased, the flame propagation velocities of pure zirconium dust cloud were higher than those of FeOOH-coated zirconium dust cloud with the molar ratio of 1:6, which in turn were higher than the molar ratio of 1:3 due to the zirconium content. With increasing the concentration from 0.313 to 0.938 kg m−3, the temperatures of FeOOH-coated zirconium dust cloud with the molar ratio of 1:6 and 1:3 both were no peak. Moreover, the temperatures of FeOOH-coated zirconium dust cloud with the molar ratio of 1:6 were always higher than those with the molar ratio of 1:3. There were three phases of mass loss FeOOH-coated zirconium particles by TG test. The first phase of mass loss was because of evaporation of the FeOOH-coated zirconium particles, and the second phase of mass loss was the generation of Fe2O3 because of dehydroxylation of FeOOH. The third phase of mass loss was the residual of thermal decomposition due to Fe3O4 being formed from Fe2O3. It was also concluded that a replacement reaction occurred between Zr and Fe2O3 in the combustion process, and pure Fe is oxidized to Fe3O4 at high temperatures.