Thermal Reactivity of Nanostructure Al0.8Mg0.2 Alloy Powder Used in Thermites

摘要:

采用双向球磨法，通过控制球磨时间和助磨剂的添加量，制备了具有纳米级晶粒度的Al-Mg合金，该合金很有希望应用为冲击引发含能材料中的固体燃料。结构表征表明，机械合金化处理后得到的Al0.8Mg0.2呈粒状，且其表面存在大量尺寸约为15～30 nm的纳米结构。另外，球磨后材料的晶粒度从原料Al的>100 nm降低到Al0.8Mg0.2的22.7 nm。热分析结果表明，Al0.8Mg0.2合金粒子具有很高的热反应活性。在空气中，Al0.8Mg0.2合金于熔化前就发生了明显的氧化还原反应，而这种固-气相反应在原料Al的DSC图谱中却没有出现，且Al0.8Mg0.2-O2体系的高温反应放热峰较Al-O2体系提前了33 °C。从TG图谱中可以看出，当加热温度达到1100 °C后，有69.13%的Al0.8Mg0.2被空气中的O2氧化，而在相同的条件下原料Al只有15.52%被氧化，可见原料Al的氧化效率远低于Al0.8Mg0.2。另外，对于Al0.8Mg0.2-Fe2O3铝热体系，其在合金熔化前也发生了显著的固-固相反应，该反应的活化能比随后的液-固相反应降低了331.664 kJ·mol-1，这表明由Al-Mg合金组成的铝热剂应具有优异的点火性能。

Abstract:

Al-Mg alloy, as a kind of promising solid fuel applied in impact-initiated energetic materials, was fabricated by bi-direction rotation ball milling. Structure characterization reveals that the surface of Al0.8Mg0.2 granular particles exhibits a mass of nanostructure with size of 15-30 nm and the crystallite size decreases from more than 100 nm (raw Al) to 22.7 nm (Al0.8Mg0.2) after mechanical alloying. Thermal analysis indicates that Al0.8Mg0.2 presents excellent thermal reactivity. In the air, Al0.8Mg0.2 will be oxidized by O2 distinctly before melting. Moreover, the high temperature reaction of Al0.8Mg0.2-O2 is advanced by 33 °C compared with Al-O2 system. TG traces show that about 69.13% of Al0.8Mg0.2 are oxidized when the temperature increases to 1100 °C, but the value is merely 15.52% for raw Al. Using the alloy in thermites, other than Al-Fe2O3, Al0.8Mg0.2-Fe2O3 system presents a considerable solid-solid reaction. In addition, for Al0.8Mg0.2-Fe2O3, the average active energy of solid-solid reaction is lower by 331.664 kJ·mol-1 than that of the liquid-solid reaction, which means an advantage in ignition.