Surface Nitridation Of Aluminum Nanoparticles

Aluminum nanoparticles possess desirable combustion characteristics such as high heats of combustion, fast energy release rates, burning completeness and phenomenon of no cluster aggregation in combustion process. Because of their capability to enhance performance, various metals have been introduced in solid propellant formulations. There are many advantages of incorporating nano-sized materials into fuels and propellants, such as: 1) significantly improved the specific impulse; 2) reduced pressure index and characteristic signal. However, Aluminum nanoparticles have a large specific surface area and high specific surface energy, which can easily be oxidized and deactivated, thus limiting their current use.In order to obtain the corresponding kinetic parameters(apparent activation energy(Ea), pre-exponential constant(A) and the most probable kineticmodel function, the DSC curves at heating rates of 5, 7, 8, and 9 K·min- 1 were dealt by five integral methods(Ordinary-Integral,Mac Callum-Tanner,Satava-Setak,Agrawal,Flynn-Wall-Ozawa)and one differential methods. The apparent activation energy(Ea) and pre-exponential factor(A) of the main decomposition reaction were 111.74 k J?mol-1 and 103.46 s-1. The reaction mechanism obeys Mampel Power with n=3/2. The kinetic equation can be expressed asIn this work, the surface nitriding of aluminum nanoparticles were studied by the method of off-line and on-line nitriding, based on flow-levitation method. The phase, morphology and structure of Aluminum nanoparticles were analyzed by X- ray diffraction, scanning electron microscope, transmission electron microscopy and X-ray photoelectron spectroscopy. The results show that the aluminum nanoparticles before nitriding are spherical, and the surface layer is about 3nm thick aluminum oxide layer; After nitriding, the particles show a clear core shell structure and thickness of the shell is about 6~7 nm, besides, particle size and the degree of the ball do not change.Temperature, holding time and additives are important factors for the off-line nitriding of aluminum nanoparticles. In the tube furnace, the diffraction peak of the aluminum nitride is appeared, when the temperature reached 550 ? and heat insulation for 30 minutes. Under the same conditions, when the mass fraction of NH4 Cl was 10wt%, 20wt% and 50wt%, the phase of XRD was different. Although the conditions are the same for the offline nitriding in the glove box, the results are different. The important factors affecting the on-line nitriding are the gas flow rate of the high purity nitrogen and argon gas and silking rate. Under the condition of silking rate of 90 Hz and high purity Nitrogen gas with high purity Argon gas flow ratio of 5-2, diffraction peak of aluminum nitride does not appear in the XRD. The molar ratio of aluminum nitride, alumina and aluminium is 8.72: 61.08: 30.2, through the analysis of test results of XPS.