Preparation And Property Of Energetic Aluminum Nano-powders

It is a common method to improve the energy performance of explosives and solid propellants by adding metal powder. Metal nanopowder show unique advantages compared to micro-size powder. Aluminum nanoparticles (Al-NPs) are one of the most important metal additive in explosives and solid propellants owing to the advantages of high active, high calorific value and strong after burning effect. However, Al-NPs are easily to be oxidized and lose activity due to the property of high activity. Therefore, surface modification is in need to keep the activity of Al-NPs, one of the most effective methods is to coat carbon layer onto the surface.In this paper, carbon-coated Al-NPs were prepared by DC arc plasma method and chemical method. Al-NPs prepared by DC arc plasma method at 1.0KPa CH4 and 2.5KPa Ar atmosphere, which were confirmed coating with carbon or Al2O3 by XRD and HRTEM; TG-DTA show that incipient oxidation temperature of Al-NPs decreases. However,Al-NPs were prepared by DC arc plasma method at 0.5KPa CH4 and 2.5KPa Ar or 2.0KPa CH4 and 2.5KPa Ar. XRD has diffraction peaks of Al2O3 and Al4C3,which shows that large amount of Al2O3 and Al4C3 were formed,respectively. Carbon-coated Al-NPs were also prepared by chemical method. Infrared Carbon-Sulfur Determinator, XRD, TEM, BET, Raman, TG-DTA were used to analyze the prepared nanoparticles. The results exhibit a carbon content of 0.37% in the prepared nanoparticles, and no crystal structure was founded on the surface which is different from passivated aluminum nanoparticles. The BET results show that the specific surface area is 5.967m2·g-1 and the mean size is 373.8nm, while related to the TEM images, it can be concluded that aggregation is easy to occur among Al-NPs because of the high activity. In summary, carbon-coated Al-NPs prepared by chemical method is nanocrystalline graphite and alumina shell. Results of TG-DTA indicate that, oxidize resistance and stability of carbon-coated Al-NPs significantly improved compared with passivated Al-NPs.Particle size of Al-NPs, which is the most fundamental and important performance indicator, determines its chemical activity. The influence of process parameters, such as cathode current and argon pressure on the productivity and particle size of Al-NPs were discussed, in order to prepare of Al-NPs with reasonable particle size by DC arc plasma method. The results show that cathode current and argon pressure influent greatly on the productivity and particle size of Al-NPs in the process of preparing Al-NPs by DC arc plasma method, and the productivity of Al-NPs increases with the increase of cathode current, while the particle size of Al-NPs increases at first and then decreases with the increase of cathode current. In an atmosphere of hydrogen and argon, both productivity and particle size of Al-NPs show the first increase and then decrease trend with the increase of the proportion of argon.