Key Laboratory of Soft Chemistry and Functional Materials of MOE, School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China.
Phys Chem Chem Phys. 2018 Nov 28;20(46):29341-29350. doi: 10.1039/c8cp05006f.
Aluminized explosives have important applications in civil construction and military armaments, but their thermal decomposition mechanisms are not well characterized. Here, the thermal decomposition of TNT, RDX, HMX and CL-20 on Al nanoparticles is examined by reactive dynamics simulations using a newly parameterized reactive force field with low gradient correction (ReaxFF-lg). Partially passivated Al nanoparticles were constructed and mixed with TNT, RDX, HMX and CL-20 crystals and then the mixed systems are heated to a high temperature in which the explosives are fully decomposed. The simulation results show that the aluminized explosives undergo three main steps of thermal decomposition, which were denoted "adsorption period" (0-20 ps), "diffusion period" (20-80 ps) and "formation period" (80-210 ps). These stages in sequence are the chemical adsorption between Al and surrounding explosive molecules (R-NO2-Al bonding), the decomposition of the explosives and the diffusion of O atoms into the Al nanoparticles, and the formation of final products. In the first stage, the Al nanoparticles decrease the decomposition reaction barriers of RDX (1.90 kJ g-1), HMX (1.95 kJ g-1) and CL-20 (1.18 kJ g-1), respectively, and decrease the decomposition reaction barrier of TNT from 2.99 to 0.29 kJ g-1. Comparing with the crystalline RDX, HMX and CL-20, the energy releases are increased by 4.73-4.96 kJ g-1 in the second stage. The number of produced H2O molecules increased by 25.27-27.81% and the number of CO2 molecules decreased by 47.73-68.01% in the third stage. These three stages are further confirmed by the evolutive diagram of the structure and temperature distribution for the CL-20/Al system. The onset temperatures (To) of generating H2O for all the aluminized explosives decrease, while those of generating CO2 for aluminized HMX and CL-20 increase, which are in accord with the experiment of aluminized RDX.
含铝炸药在民用建筑和军事装备中有重要的应用，但它们的热分解机制尚未得到很好的描述。在这里，我们使用新参数化的具有低梯度修正的反应力场（ReaxFF-lg），通过反应动力学模拟研究了 TNT、RDX、HMX 和 CL-20 在 Al 纳米粒子上的热分解。构建了部分钝化的 Al 纳米粒子，并将其与 TNT、RDX、HMX 和 CL-20 晶体混合，然后将混合系统加热到高温，使炸药完全分解。模拟结果表明，含铝炸药经历了三个主要的热分解步骤，分别表示为“吸附期”（0-20 ps）、“扩散期”（20-80 ps）和“形成期”（80-210 ps）。这些阶段依次为 Al 与周围炸药分子之间的化学吸附（R-NO2-Al 键合）、炸药的分解以及 O 原子扩散到 Al 纳米粒子中以及最终产物的形成。在第一阶段，Al 纳米粒子分别降低了 RDX（1.90 kJ g-1）、HMX（1.95 kJ g-1）和 CL-20（1.18 kJ g-1）的分解反应势垒，并将 TNT 的分解反应势垒从 2.99 降低至 0.29 kJ g-1。与晶体状的 RDX、HMX 和 CL-20 相比，第二阶段的能量释放增加了 4.73-4.96 kJ g-1。第三阶段产生的 H2O 分子数增加了 25.27-27.81%，CO2 分子数减少了 47.73-68.01%。CL-20/Al 体系结构和温度分布演化图进一步证实了这三个阶段。所有含铝炸药生成 H2O 的起始温度（To）降低，而含铝 HMX 和 CL-20 生成 CO2 的起始温度升高，这与含铝 RDX 的实验结果一致。
