Nanothermite Sensitivity and Stability

粉末金属燃料和金属氧化物氧化剂的组合，每一个都是纳米尺寸，可以导致一个化学上不稳定的系统，称为纳米热矿。纳米热矿作为高能材料具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器点燃。基于铝燃料和一系列金属氧化物的系统被广泛研究。通常采用在有机溶剂中使用超声处理混合，然后蒸发溶剂。虽然纳米热电材料具有固有的反应性，但这些材料的应用受到罕见的意外和不受控制的引发的限制，这被认为是由摩擦和静电放电（ESD）引起的。本提议的重点是查明这种敏感性的根源，并审查可减轻这些敏感性的方法。虽然存在大量的文献检查nanothermite性能和应用，它被认为是超声波混合提供燃料和氧化剂的均匀分布，在化学组成和粒度方面。拟议的研究将调查沉降对nanothermite组合物的影响，并检查所得材料的摩擦和静电放电敏感性。虽然已知减小的粒度增加了纳米热敏材料的灵敏度，但不知道常规混合材料中粒度分布和灵敏度变化的程度。聚集通常在纳米材料中观察到，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率，以及颗粒尺寸分布，也将被检查。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。文献很少表征所研究的纳米热矿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菌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，但不存在定量或预测性的理解。目前的工作将合成各种各样的氧化铜（II）纳米材料的不同粒径，粒径分布和形态，以建立氧化剂和摩擦和ESD敏感性之间的结构/活性关系。含铝燃料的氧化铜（II）系统特别适合于此类研究，因为它存在于中等灵敏度，其行为变化可以容易地检测和量化。最后，将探索一种新的混合方法：惰性气体夹带。这种方法提供了在组合之前筛选出单独夹带的气流中的高反应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.