The alumina shell plays a crucial role in the energy
release of
aluminum powder. The experimental results indicate the presence of
protrusions on the alumina shells during the process of aerobic heating.
To investigate the causes of protrusion formation during the aerobic
heating process, in situ transmission electron microscopy was employed
to observe the process of protrusion formation. The experiment revealed
that within the temperature range of 70–850 °C, the alumina
shell undergoes a gradual transition from smooth to rough, accompanied
by the emergence of protrusions at 850 °C. This is because, for
35–500 nm aluminum particles (ANPs), larger particle sizes
generate greater internal and tensile stresses, thereby increasing
the potential for crack formation on the alumina shell. As molten
aluminum flows out of the cracks, the potential for protrusion formation
increases and the molten aluminum rapidly oxidizes during the fast
oxidation process. Moreover, the larger diameter of ANPs results in
a higher quantity of active aluminum, leading to greater heights of
the protrusions. These results reveal the reasons for the formation
of protrusions in the dynamic oxidation process of ANPs and its relationship
with the particle size, which complements the current research on
the morphology changes in the oxidation process of ANPs, and has important
significance for further exploration of the oxidation mechanism of
ANPs.