Nanothermite Sensitivity and Stability

粉末金属燃料和金属氧化物氧化剂的组合，每个纳米尺寸，可能会导致一个热力学不稳定的系统，被称为纳米热剂。纳米铝热石作为含能材料具有潜在的军事和民用应用前景，可作为阻性加热或低功率激光点火。基于铝燃料和一系列金属氧化物的系统得到了广泛的研究。通常采用的方法是先在有机溶剂中超声混合，然后再挥发溶剂。尽管纳米铝热材料本身具有活性，但由于摩擦和静电放电(ESD)导致的非计划和不受控制的引发现象很少发生，限制了这些材料的应用。目前的建议集中在找出这种敏感性的根本原因，并研究一种可以减轻这些敏感性的方法。尽管有大量文献研究纳米热剂的性质和应用，但假设超声波混合在化学成分和粒度方面提供了燃料和氧化剂的均匀分布。这项拟议的研究将调查沉淀对纳米铝热剂组成的影响，并检查生成的材料的摩擦和静电放电灵敏度。虽然众所周知，减小颗粒尺寸会增加纳米铝热剂材料的感度，但尚不知道在常规混合材料中，颗粒尺寸分布和感度的变化程度。在纳米材料中通常可以观察到聚集现象，这种效应在多大程度上有助于产生异常的燃料和氧化剂比率，以及颗粒大小的分散。在第二个主题中，我们将探索单一燃料：氧化剂系统的结构/反应关系。文献很少描述所研究的纳米铝热剂体系的粒度分布或形态。事实上，很少有研究直接考虑纳米温度计对外界刺激的敏感性。因此，虽然人们普遍认为较小的颗粒尺寸会提高灵敏度，但还不存在定量或预测性的理解。本工作将合成一系列不同粒度、粒度分布和形貌的氧化铜(II)纳米材料，以建立氧化剂和摩擦与ESD敏感性之间的结构/活性关系。含铝燃料的铜(II)氧化物体系特别适合于这类研究，因为它具有中等灵敏度，其行为变化很容易检测和量化。最后，将探索一种新的混合方法，即惰性气体夹带方法。这种方法提供了在组合之前从单独携带的气流中筛选出高活性小颗粒和流氓微米颗粒的可能性。

The combination of powder metal fuel and metal oxide oxidant, each of nanometre dimensions, can lead to a thermodynamically unstable system known as a nanothermite. Nanothermites have potential military and civilian applications as energetic materials, being ignited as resistive heating or low-power lasers. System based on aluminium fuel and a range of metal oxides are widely studied. Mixing using ultrasonication in organic solvents followed by solvent evaporation is commonly employed. Although nanothermites are inherently reactive, applications of these materials are limited by the rare occurrence of unplanned and uncontrolled initiation, which is believed to result from friction and electrostatic discharge (ESD). The present proposal focuses on identifying the root causes of this sensitivity and examining a methodology by which these sensitivities may be mitigated.Although an extensive body of literature exists examining nanothermite properties and applications it is assumed that ultrasonic mixing afford a homogeneous distribution of fuel and oxidant, in terms of chemical composition and particle size. The proposed study will investigate the effects of sedimentation on nanothermite composition and examine the resultant materials for friction and electrostatic discharge sensitivity. Whilst it is know that decreases particle size increases the sensitivity of nanothermite materials, no knowledge exists of the extent to which particle size distribution and thus sensitivity vary in a conventionally mixed material. Aggregation is commonly observed in nano materials and the extent to which this effect contributes to the generation of aberrant fuel and oxidant ratios, and to particle size distrubition, will also be examined.In a second theme the structure/reactivity relationship of a single fuel:oxidant system will be explored. The literature rarely characterises the particle size distributions or morphologies of studied nanothermite systems. Indeed, few studies directly consider the sensitivity of nanothermites to external stimuli. Thus, whilst it is widely acknowledged that smaller particle sizes increase sensitivity, no quantitative or predictive understanding exists. The present work will synthesise a wide range of copper(II) oxide nano materials of diverse particle size, particle size distribution and morphology to establish structure/activity relationships between oxidant and friction and ESD sensitivity. The copper(II) oxide system with aluminium fuel is particularly suited to such studies since it exists in at an intermediate sensitivity for which changes in behaviour can be readily detected and quantified.Finally, a novel mixing method will be explored; that of inert gas entrainment. This approach offers the potential to screen out highly reactive small particles and rogue micron particles in separately entrained streams of gas, before combination.