Nanothermite Sensitivity and Stability

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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.