Low Temperature Synthesis Of AIN Powder By Plasma-assisted Mechanical Activation

Aluminum nitride(Al N) is a new type and a widely used of functional ceramic materials, which has good thermal conductivity, electrical insulation and the thermal expansion coefficient close to silicon, etc. With the development of ship toward to intelligence and automation, the application of Al N in the ship and the marine engineering is getting more and more. In this paper, Al N was synthesized by plasma assisted mechanical activation at room temperature. Compared with conventional carbon thermal reduction method and direct nitrogen nitride method, the synthesis temperature of Al N was significantly decreased by DBDP assisted ball milling.In this paper, the synthesis of Al N from three systems by conventional ball milling and dielectric barrier discharge plasma(DBDP) assisted ball milling is studied.The gas-solid reaction system of Al+NH3 mixture was studied in this paper. It was found that despite the chemical properties of NH3 was more lively and violently than N2, synthetic molecule Al N was hardly achieved by DBDP assisted ball milling at room temperature because of the limitations of gaseous nitrogen source,which had small molecular weight and was not sufficient when contacted with the reactants. But the energy particles produced by DBDP can refined the powder effectively.The gas-solid reaction system was studied, in which the N2 was taken as nitrogen source and Al+Li OH?H2O as raw material. A very small amount of Al N powder was obtained only after one hour milling at room temperature by the two kinds of ball milling methods. With the increase of milling time, the Al N diffraction peak weakened gradually and then disappeared, because the Al N hydrolysis reaction has happened with the ball milling in the ball milling tank.The gas-solid reaction system of Al+DAMN mixture was studied. The Al N was successfully prepared by DBDP assisted ball milling at room temperature. The conversion of Al N gradually increased with the increase of time, and the conversion of Al N by DBDP assisted ball milling was higher than the conversion by common milling. It indicates that the synergistic effect of plasma and mechanical energy is more favorable for the reaction compared with the sole mechanical energy.By means of electric diagnosis, the intensive and stable pulsed discharge is obtained during the plasma assisted ball milling, leading to produce a lot of energetic particles. According to the analysis on the changes of the functional groups in the reaction process by FTIR, the main reason for synthesis of Al N from Al+DAMN is that the high-energy particles produced by plasma bombarding which make the powder produce electric blasting partially and lose nitrile and amino of the unstable DAMN. These free nitrogen groups will promote the synthesis of Al N in the end by reacting with Al. The energy particles produced by DBDP have high thermal effect, kinetic energy, surface sputtering and activation on the powders, thus improving the activity of powder and decreasing the activation energy of the reaction significantly. Al N will be synthesized at room temperature directly.