Influence of particle size on the breaking of aluminum particle shells

Abstract

The rupture of the alumina shell (shell-breaking) is a prerequisite for the energy release of aluminum powder. The thermal stress overload in a high temperature environment is one of the important factors for the rupturing of the alumina shell. COMSOL Multiphysics was used to simulate and analyze the shell-breaking response of micron aluminum particles with different particle sizes at 650 ℃ under vacuum environment. The simulation result shows that the thermal stability time and shell-breaking response time of 10-100 μm aluminum particles are 0.15-11.44 μs and 0.08-3.94 μs respectively. It also shows the direct shell-breaking cause of aluminum particle with different particle sizes. When the particle size is less than 80 μm, the shell-breaking response is directly caused by compressive stress overload. When the particle size is 80-100 μm, the shell-breaking response is directly caused by tensile stress overload. This article has guiding significance for the research on the energy release of aluminum powder.

Study on the Size Dependence of the Shell-Breaking Response of Micro/Nano Al Particles at High Temperature

“…This result indicates that the In the range of 100-600 nm, due to the difference of specific surface area and R ratio, the maximum tensile stress of 100-200 nm Al nanoparticles is uniformly distributed (which is consistent with the distribution of 25-70 nm), and the maximum tensile stress of 300-600 nm Al nanoparticles is distributed in two straight lines perpendicular to each other. It is worth noting that in the previous article on micrometer Al particles [24], the maximum stress is mainly distributed in two lines at 45 • and 135 • , which are also two straight lines perpendicular to each other, and this is consistent with the distribution of the stress in 300-600 nm in this paper. Therefore, it can be considered that the maximum stress at 25-70 nm is uniformly distributed, while the maximum stress at 100-200 nm is uniformly distributed but begins to transition towards a vertical linear distribution.…”

“…This is due to the fact that the maximum compressive stress is determined by both the center temperature and the ratio R of the Al particles. The lower the center temperature, the smaller the maximum compressive stress and the larger the ratio R [24].…”

“…The small size effect and surface effect of Al nanoparticles have led to higher reactivity than micron Al particles [22,23], and thus to a wider range of applications, but have also led to a different reaction mechanism than that of micron Al particles. The previous paper [24] investigated the force-heat coupling process of micron particles and analyzed the shell-breaking characteristics and causes, and this paper takes up the previous paper to quantitatively characterize the thermo-mechanical behavior of Al nanopowder using simulation software COMSOL. Oxide shell rupture is affected by a variety of zfactors [25] such as internal stress due to differences in coefficients of thermal expansion, oxidative thickening of the shell, and crystal transformation, etc.…”

Experimental Study on the Alumina Shell Protrusions of Aluminum Nanoparticles during the Aerobic Heating Environment

“…The measurements showed that the height of protrusion increased with increasing particle size. The reason is that the larger the d ANPs is, the greater the compressive stress in the aluminum core and the tensile stress on the alumina shell are. , As a consequence, ANPs with larger diameters are more prone to cracking on the alumina shell under compressive and tensile stresses. Larger particles have higher reactive aluminum content, the volume share of the aluminum core is relatively greater, and more aluminum liquid flows out of the cracks and is oxidized to develop protrusions.…”