Combustion of Al nanoparticles coated with NC/ethanol/ether molecules by equilibrium molecular dynamics simulations

Abstract

Al nano-particle (ANP) have high reactivity, but they are easily inactivated by external oxidants. To improve its surface property, we coat ANPs with nitrocellulose (NC)/ethanol/ether solution. And MD simulation method is used to simulate the coating, ignition and combustion processes of ANPs under three different coating conditions. Our results show that the NC/ethanol/ether formed a dense coating layer on the surface of annealed ANPs and passivated ANPs through physical and chemical adsorption. The coating layer can block the contact between the active Al atoms and O2 molecules at low temperature. In ignition phase, NC/ethanol/ether coating layer can increase the density of O2 molecules around ANPs and the surface temperature of ANPs. At the same time, due to the desorption and diffusion of the coating layer exposed more reaction sites, ANPs have shorter ignition delay and lower ignition temperature. According to the change of atomic displacement, the combustion stage can be divided into three stages. The NC molecules can increase the combustion propagation speed, combustion time and efficiency of ANPs. Such improvement will enable ANPs to obtain better storage performance, combustion performance and play a stronger role in the field of energetic materials.