Melt-Dispersion Mechanism for Energetic Reactions of Aluminum Nanoparticles

CBET-0755236 Levitas铝颗粒正被整合到高能配方中，并被考虑用于材料合成和军械应用的复合技术。最近，引入了一种新的机械化学机制，显示出理解极快Al纳米颗粒反应的潜力。该理论适用于Al纳米颗粒的快速加热期间，其中由于包裹在氧化铝壳中的Al核的熔化引起的体积变化引起1- 2GPa的极端压力，导致氧化物壳的分散。铝芯和暴露表面之间的不平衡压力产生具有高拉伸压力的卸载波，导致高速飞行的小液体铝团簇的分散。因此，纳米颗粒反应不受扩散的限制。提出的熔体分散机制是解决纳米Al燃烧中一些基本难题的唯一现有解释。该项目的目标是定义铝纳米颗粒反应的熔融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颗粒;并利用所获得的基础知识改进铝基配方。将考虑以下任务：（a）发展参与熔体分散机制的物理过程的综合理论，（B）基于理论预测和新的颗粒设计概念合成Al颗粒，（c）实验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）预测和实验确认将改善Al颗粒在各种配方中的反应性的方法。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格拉德生一起工作。 此外，纳米颗粒燃烧将被纳入燃烧课程和高能材料的继续教育计划。研究人员还计划在各种国际会议上组织专门讨论“机械化学”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.