School of Materials Science and Engineering, University of Shanghai for Science and Technology, PR China.
J Phys Chem B. 2012 Dec 6;116(48):14136-45. doi: 10.1021/jp308351g. Epub 2012 Nov 19.
To gain an atomistic-level understanding on physical and chemical processes occurring at the interfaces of hypergolic propellants, we carried out the first reactive dynamic (ReaxFF) simulations to study the reactive hypergolic mixture of monomethylhydrazine (MMH) and dinitrogen tetroxide (NTO), in comparison with the ethanol (EtOH) and NTO mixture that is reactive but nonhypergolic. Our studies show that the MMH-NTO mixture releases energy more rapidly than the EtOH-NTO mixture upon mixing the fuels and oxidizers. We found that the major early chemical reactions between MMH and NTO are hydrogen abstractions and N-N bond scissions. The MMH-NTO mixture has more reaction channels than EtOH-NTO based on statistical analyses of chemical reaction events and channels at early stages of the dynamics. Analyzing the evolution of product distribution over reaction time shows that the oxidizer (NO(2)) diffuses into the fuels (MMH or EtOH) for the occurrence of reactions, demonstrating the influence of physical mixing on chemical reactions. Our simulations suggest that effective hypergolic systems require fuels with low energy barriers of H abstractions and/or bond scissions and oxidizers with large diffusion mobility for efficient physical mixing.
为了深入了解在自燃推进剂界面上发生的物理和化学过程，我们进行了首次反应动力学（ReaxFF）模拟，以研究偏二甲肼（MMH）和四氧化二氮（NTO）的反应性自燃混合物，并与具有反应性但非自燃的乙醇（EtOH）和 NTO 混合物进行了比较。我们的研究表明，在混合燃料和氧化剂时，MMH-NTO 混合物比 EtOH-NTO 混合物释放能量更快。我们发现，MMH 和 NTO 之间的主要早期化学反应是氢提取和 N-N 键断裂。基于动力学早期的化学反应事件和通道的统计分析，MMH-NTO 混合物比 EtOH-NTO 具有更多的反应通道。分析反应时间内产物分布的演化表明，氧化剂（NO（2））扩散到燃料（MMH 或 EtOH）中以发生反应，这表明物理混合对化学反应的影响。我们的模拟表明，有效的自燃系统需要具有低氢提取和/或键断裂能垒的燃料和具有大扩散迁移率的氧化剂，以实现有效的物理混合。
