Preignition characteristics of nano- and micrometer-scale aluminum particles in Al–CO2 oxidation systems

The objective of this study was to gain understanding of the preignition oxidation of Al powders in CO2. The thermal behavior and reaction energy was studied using simultaneous thermogravimetric analysis and differential scanning calorimetry (TG–DSC). The particle morphology was examined at different stages of the process using field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM). The corresponding chemical changes were analyzed by X-ray diffraction spectrometry (XRD) and energy dispersion X-ray spectrometry (EDS). Dimensional properties of Al particles have a significant influence on the oxidation processes. Distinctly different properties were shown between nm-Al and μm-Al, where the reactions are found to occur at different temperature ranges. The powder behavior is controlled by the oxide layer that coats each particle and prevents exposure of the metal core to the reactive CO2 gas. The properties of the oxide layer are related to the particle size. Carbon has been shown to play an important role in the reacting Al–CO2 system. A new mechanism of nano-Al particle oxidation in CO2 under gradually increasing temperature was proposed.