Nanothermite Sensitivity and Stability

粉末金属燃料和金属氧化物氧化剂的结合，每一个都是纳米尺寸，可以导致一个热力学不稳定的系统，被称为纳米热剂。纳米热螨作为高能材料有潜在的军事和民用应用，可以作为电阻加热或低功率激光点燃。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。在有机溶剂中使用超声波混合，然后进行溶剂蒸发是常用的方法。尽管纳米热螨本身具有反应性，但这些材料的应用受到罕见的计划外和不受控制的起爆的限制，这被认为是由摩擦和静电放电（ESD）引起的。本建议的重点是查明这种敏感性的根本原因，并审查一种可以减轻这些敏感性的方法。虽然有大量的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颗粒大小方面提供了均匀的燃料和氧化剂分布。该研究将研究沉积对纳米热剂组成的影响，并检查所得材料的摩擦和静电放电敏感性。虽然我们知道减小颗粒尺寸会增加纳米热剂材料的敏感性，但对于在常规混合材料中颗粒尺寸分布和敏感性变化的程度却一无所知。在纳米材料中通常观察到聚集，并且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例，以及颗粒大小分布，也将进行研究。在第二个主题中，将探讨单一燃料：氧化剂系统的结构/反应性关系。文献很少描述所研究的纳米热剂系统的粒度分布或形态。事实上，很少有研究直接考虑纳米热螨对外部刺激的敏感性。因此，虽然人们普遍认为较小的颗粒尺寸会增加灵敏度，但没有定量或预测性的理解存在。本研究将合成各种不同粒径、粒径分布和形貌的氧化铜纳米材料，以建立氧化剂与摩擦和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，可以很容易地检测和量化其行为的变化。最后，探索一种新的混合方法；惰性气体夹带量。这种方法提供了在组合之前，在单独夹带的气体流中筛选出高活性小颗粒和流氓微米颗粒的潜力。

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.