Melt-Dispersion Mechanism for Energetic Reactions of Aluminum Nanoparticles

CBET-0755236Levitas铝颗粒正在被整合到高能配方中，并被考虑用于重叠技术，如材料合成和兵器应用的铝热剂。最近，一种新的机械力化学机制被引入，它显示了理解极快的Al纳米粒子反应的潜力。这一理论适用于铝纳米颗粒的快速加热，其中包裹在氧化铝外壳中的铝芯由于熔化而产生的体积变化会导致1-2 Gpa的极端压力，从而导致氧化物外壳的剥落。铝芯和裸露表面之间的不平衡压力产生了具有高拉伸压力的卸荷波，导致高速飞行的小液铝团簇的分散。因此，纳米粒子的反应不受扩散的限制。提出的熔体分散机制是目前唯一能解决纳米铝燃烧中一些基本难题的解释。该项目的目标是确定铝纳米粒子反应的熔体分散机制的主要条件和控制物理参数；将该机制扩展到微米级粒子；并利用所获得的基础知识来改进铝基配方。将考虑以下任务：(A)发展参与熔体分散机制的物理过程的全面理论，(B)基于理论预测和新的颗粒设计概念合成Al颗粒，(C)从实验上研究熔体分散机制的含义，(D)将熔体分散机制扩展到微米级颗粒，以及(E)预测和实验证实将在各种配方中改善Al颗粒反应性的方法。除了潜在的技术影响，还将开发一个指导计划，让本科生在研究环境中与研究生合作。此外，纳米颗粒燃烧将被整合到燃烧课程和高能材料的继续教育计划中。研究人员还计划在各种国际会议上组织专门讨论“机械化”过程的专题讨论会。

CBET-0755236LevitasAluminum particles are becoming integrated into energetic formulations and considered for overlapping technologies such as materials synthesis and thermites for ordnance applications. Recently, a new mechanochemical mechanism has been introduced that shows potential for understanding extremely fast Al nanoparticle reactions. This theory applies during fast heating of Al nanoparticles, where the volume change due to melting of the Al core encased in an alumina shell induces extreme pressures of 1-2 GPa, resulting in a spallation of the oxide shell. The unbalanced pressure between the Al core and exposed surface creates an unloading wave with high tensile pressures, resulting in dispersion of small liquid Al clusters that fly at high velocity. Thus, nanoparticle reactions are not limited by diffusion. The proposed melt-dispersion mechanism is the only existing explanation that resolves a number of basic puzzles in nano-Al combustion. The goal of this project is to define the main conditions and controlling physical parameters for operation of the melt-dispersion mechanism for reactions of Al nanoparticles; to extend this mechanism for micron-scale particles; and to utilize obtained fundamental knowledge for the improvement of Al-based formulations. The following tasks will be considered: (a) develop comprehensive theories for physical processes participating in the melt-dispersion mechanism, (b) synthesize Al particles based on theoretical predictions and new particle design concepts, (c) study implications of the melt-dispersion mechanism experimentally, (d) expand the melt-dispersion mechanism to micron-scale particles, and (e) predict and experimentally confirm methods that will improve the reactivity of Al particles in various formulations. Beyond the potential for technological impact, a mentoring program will be developed where undergrads work with grad students in a research environment. In addition, nanoparticle combustion will be integrated into the combustion curriculum and a continuing-education program in energetic materials. The investigators also plan to organize special symposia devoted to "mechanochemical" processes at various international conferences.