Study On The Preparation Of Aluminium-based Amorphous Powder And Its Application In Reactive Material

Al/polytetrafluorethylene?PTFE? reactive material has broad application prospects in military and civil fields due to its excellent insensitivity, shock initiation and energy release characteristics. In despite of its limited applications resulting from the poor glass forming ability, Al-based amorphous alloys present higher levels of driving force of chemical reaction than equilibrium Al alloys, due to it's much further from the thermo dynamic equilibrium. Therefore, this thesis introduced the Al-based amorphous alloys into Al/PTFE reactive material in order to achieve a type of novel reactive materials. Namely, the Al-based amorphous alloy powder was prepared by mechanical alloying, and its phase composition, morphology characteristics, phase structure and thermal behavior were analyzed by XRD, SEM, HRTEM, and DSC methods. The non-equilibrium Al/PTFE reactive materials were prepared via mixing/pressing route using Al-based amorphous alloy and PTFE powders. Finally, the thermal behaviors and reaction kinetics of non-equilibrium Al/PTFE reactive materials were examined by DSC.By the principle of eutectic points, the alloy composition of Al70Ni15Ti10Zr5 was designed as the candidate of Al-based amorphous alloy. The influence of ball milling parameters on the amorphization mechanism during mechanical alloying process was analyzed. The results show that a high level of amorphous state Al alloy powder is obtained after milling at the milling speed of 400rpm/min for 160 h with the ball to powder ratio of 30:1. Low milling speed and small ball to powder ratio lead to less amorphous structure during ball milling. There are nano crystalline island areas dispersed in amorphous phase matrix in the product non-equilibrium powder. Under the heating rate of 40K/min in argon atmosphere, Al-based amorphous alloy powder has two continuous crystallization transition exothermic peaks at 413.5°C and 445.7°C, respectively.The non-equilibrium Al/PTFE reactive materials were prepared using mixing/pressing technique with Al-based non-equilibrium alloy powders and PTFE micrometer powders. The effect of oxygen partial pressure of testing atmosphere on the thermal behavior was studied with DSC method as well. The results show that oxygen can promote the thermal decomposition of PTFE in the non-equilibrium Al/PTFE reactive materials, and thus leads to a early reaction between Al and PTFE. With the increase of the oxygen partial pressure from 0% to 20%, the reaction peak temperatures of the non-equilibrium Al/PTFE decrease from 623.8°C to 491.5°C. Within the DSC curve of non-equilibrium Al/PTFE reactive materials, there is a much sharper, exothermic peak with a similar peak area, in comparison with that of the nano-Al/PTFE reactive materials, which indicates a stronger reaction activity.The effect of oxygen partial pressure on the reaction kinetics of non-equilibrium Al/PTFE reactive materials was studied by the linear heating DSC at different heating rates. The results show that the non-equilibrium Al/PTFE reactive materials have a good linear relationship between the peak temperature Tp and the heating rate ? under the different heating atmospheres. With the oxygen partial pressure increased from 0% to 20%, the extrapolated reaction peak temperature at 0K/min reduces from 607.9°C to 476.8°C. The reaction activation energy reduces from 421.7kJ·mol^-1 to 308.5kJ·mol^-1 calculated by Kissinger method, as well as from 436.1kJ·mol^-1 to 321.7kJ·mol^-1 by Ozawa method.