含能添加物对纳米铝热剂能量释放特性的调控机制研究

Researches of thermites serving as a new species of green and safety highly energetics materials are being promoted by development of nano materials technology. Restricted by thermal/mass transfer process of condensed phase reaction, the energy release rates of nanothermites are well below their potential maximal value. Compared with decreasing particles sizes of reactants or ameliorating interfacial structure between fuels/oxides, introducing energetic additives into reactants to adjust reactions courses and thermodynamic characteristics is much more effective, however the boosting reaction mechanism needs to be systematic studied. In this program, high organic explosives, energetic gas generator and fluoro-oxidant would be chosen as additives of different nanothermites Al/Fe2O3、Al/CuO and Al/Bi2O3 with varying gas production. To investigate the influence of spices and contents of additives on the energy release characteristics, electrospary would be utilized to assemble the additives and nanotherimites, then measurements of morphology, thermodynamic characteristics, combustion performance and micropropulsion performance of the mixtures，as well as preliminary evolution of deflagration to detonation transition would be implemented. A combustion propagation model based on microscale heat transfer theory would be conducted to verify the tests results and to reveal the control mechanism of energetic additives on the reaction behaviors. These results would open up new horizons for establishing system of highly energetic materials, and provide experimental and theoretical evidences for its application to micro/nano-energetic devices.

纳米材料技术的发展促进了铝热剂作为新型绿色安全高能含能材料的研究。受限于凝聚相反应的传质传热过程，纳米铝热剂的能量释放速率仍有巨大的提升空间。与降低反应物粒径、调整燃料/化剂的界面结构相比，含能添加物可以改变纳米铝热剂的热力学特性和反应历程，但是反应促进机制仍待系统地研究。针对不同产气量的Al/Fe2O3、Al/CuO和Al/Bi2O3纳米铝热剂体系，本项目拟选择高能有机炸药、含能产气剂和含氟强氧化剂作为含能添加物，通过静电喷射技术高效、有序地组装为复合含能材料，通过对目标混合物的形貌表征、热力学性能、燃烧性能和微推进性能测试，初步考察燃烧转爆轰的能力，研究含能添加物对纳米铝热剂能量释放特性的影响规律，建立基于微尺度传热理论的燃烧传播模型，揭示含能添加物对纳米铝热剂反应特性的调控机制。研究结果将会为建立新型高能含能材料体系提供新的途径，为在微纳含能器件上的应用提供实验指导和理论依据。

与有机高能炸药相比，纳米铝热剂具有更高的体积/质量能量密度，可以用作MEMS火工品的点火药、起爆药等。然而，受限于低产气量，以及氧化剂与还原剂之间的传质、传热过程，纳米铝热剂的燃烧性能仍有较大的提升空间。通过静电喷雾可以高效地将纳米铝热剂和含能添加物均匀地组装在同一微米量级的颗粒中，改善铝热反应历程，提高反应输出性能。本项目系统研究了静电喷射参数、含能添加物种类以及含量、金属氧化物种类以及传热主导模式对复合含能材料反应特性的影响规律，主要结论如下：（1）溶剂种类会影响组装颗粒的形貌和微区界面结构，继而影响反应速率。高挥发速率的溶剂有利于形成多孔的表面，为铝热反应提供更多的传质、传热通道；而高黏度的溶剂容易产生纳米硝化棉纤维，阻碍反应的进行。（2）高能炸药（RDX、HMX、CL-20）对纳米铝热剂增压特性和燃烧性能的增强效果优于强氧化剂高氯酸铵和含氟化合物全氟代十四酸。在纳米铝热剂燃烧主导区域（≤30%wt），Al/CuO/NC/HMX的增压速率优于Al/CuO/NC/CL-20；而在高能炸药燃烧主导区域（≥40%wt），HMX较低的燃烧效率导致复合含能材料的增压特性低于Al/CuO/NC/CL-20。（3）金属氧化物的物化性质决定了纳米铝热剂的反应特性。Bi2O3对含能添加物放热分解反应的催化效果最显著，而添加物的分解产物对Al/Fe2O3反应特性的增强效果最高。（4）提高药剂的装填密度，传热主导模式会由热对流转为热传导，反应特性出现骤变，增压速率会降低2~3个数量级，燃烧持续时间会增加1个数量级，反应产物质量流率的降低也会引起峰值压强的下降。提高复合含能材料的燃烧温度、气体产物的密度、气体产物的比容，有利于提高对流传质、传热效率。

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