【作者】 张伟；

【导师】 沈瑞琪；

【作者基本信息】 南京理工大学 ， 兵器科学与技术， 2014， 博士

【摘要】 激光起爆炸药是一种新型的起爆手段,与传统的起爆手段相比具有高可靠性和高安全性的特点,是未来起爆装置的备选技术之一。激光起爆过程包含着一系列复杂的物理和化学过程,对于激光起爆的分子动力学机理还缺乏系统的认识。为进一步揭示激光与含能材料的作用机理,系统地研究了硝酸脂类(PETN)、硝胺类(RDX和HMX)和芳香族硝基类(TNT和HNS)等三类典型含能化合物在532nm和1064nm两种波长激光作用下的解离过程,初步探讨了叠氮化钠(NaN3)在532 nm激光烧蚀下团簇的形成机理。实验中采用飞行时问质谱仪(TOFMS)分别探测激光解离含能材料形成的正、负离子,研究了激光能量和延迟时间对解离产物的影响。通过对离子成分的分析,提出了各含能化合物可能的解离机理。采用量子化学方法对解离过程中产生的各中间产物和过渡态的几何结构进行了优化和振动频率计算,并在分子能量水平上对所提出的解离过程进行了分析。具体研究内容如下：(1)测试了五种含能化合物(ETN、RDX、HMX、TNT和HNS)在400 nm～1000nm和P900nm～1700nm两个波段下的光反射率,实验结果表明,各含能化合物对1064nm光的反射率要高于对532 nm光的反射率。用飞行时间质谱仪探测了三类含能化合物在两种波长激光作用后产生的正、负离子产物,并研究了激光能量密度和延迟时问对解离产物离子强度的影响,结果表明：同种炸药在两种波长的激光作用下解离产生的离子种类相似,说明其在两种波长下的解离机理相似；同类炸药的离子种类也具有相似性,说明同类炸药的解离机理也相似；在实验测试范围内,各炸药解离产生的离子信号强度随激光能量的增大而增大,说明解离速度和解离量增大；在实验测试范围内,各炸药解离产生的离子信号强度随延迟时间的增大呈先增大后减小,说明激光作用后不同时间解离反应发生的程度不同。(2)根据各含能化合物的分子结构和飞行时间质谱分析得到的部分离子峰的归属,提出了各含能化合物可能的解离路径。使用量子化学的密度泛函理论(DFT)在B3LYP/6-31+G (d,p)水平上对解离路径中各中间体和过渡态进行了结构优化和频率计算。通过比较各解离路径的能垒、放热量和产物的稳定性,确认了各含能化合物最可能的发生解离路径。对于PETN,逐次消去四个HONO生成CO和CH4的路径是主导反应。对于RDX,逐次消去三个HONO然后开环生成HCN的反应最容易发生对于HMX,逐次消去四个HONO然后发生开环反应生成HCN是主要的解离路径。对于TNT,甲基邻位硝基和对位硝基通过异构化反应分别消去三个NO后生成CO,O2和C6H7的反应最有可能发生。对于HNS,邻位硝基通过异构化反应消去NO的初始解离反应较易发生。通过比较同类含能化合物的可能发生的解离路径发现：结构相似的含能化合物,其主导解离路径具有相似性。(3)研究了NaN3在532nm激光烧蚀下产生的正负离子团簇,离子-分子(原子)碰撞反应可以用来解释烧蚀产物中大离子团簇。更多还原

【Abstract】 The initiation of explosives by laser is a new initiation method. Compared with the traditional initiation methods, laser initiation has the characteristics of high reliability and high safety. It can be used as one of the alternative technologies for future initiation device. A microscopic understanding of the complex physical and chemical processes involved in the reaction process is essential for laser initiation. In order to give a better understanding of the mechanism of laser interaction with energetic materials, the systematic investigations for revealing dissociation processes have been carried on. Three categories of energetic compounds were selected, such as nitrate ester (PETN), nitramines (RDX and HMX) and aromatic nitro compounds (TNT and HNS). Preliminary study on the possible formation processes of sodium azide (NaN3) clusters under 532 nm laser ablation was carried out. The wavelengths of the laser were 532 nm and 1064 nm, respectively. A time of flight mass spectrometer (TOFMS) was used to detect the positive ions and the negative ions produced in the laser-induced dissociation processes. According to the possible components of the ions, possible dissociation paths of energetic compounds were proposed. The influences of the intensity and the delay time to the decomposition were also studied. Quantum chemistry method was used to optimize the geometric structure of intermediates and transition states, the vibration frequencies were also calculated. On the energy level of the molecule, the proposed dissociation processes were analyzed. The specific contents are as follows:(1) The reflectivity at 400 nm-1000 nm and 900 nm-1700 nm of five kinds of energetic compounds (PETN, RDX, HMX, TNT and HNS) mentioned above were tested. The experimental results showed that the reflectivity of these energetic compounds at 1064 nm is higher than those at 532 nm. The negative ions and positive ions of laser-induced dissociation reactions were detected by a time of flight mass spectrometer, the influence of delay time and laser energy to the intensity of the ions were also studied. The results showed that the attribution of the ions was similar for the same explosive at two different wavelengths, it indicated that the similar dissociation paths involved in the processes of explosives after irradiated by 532 nm and 1064 nm laser. For the same category of energetic compounds, the attribution of the ions was similar, that means the dissociation paths were similar. In the experimental laser energy range, the intensity of the ions increased gradually with the increasing of laser energy. Moreover, it was clear that fragmentation processes are highly dependent on the laser energy. Higher energy values resulted in an excess of internal energy and more efficient dissociation. In the experimental delay range, with the increasing of delay time, the intensity of main ions increased first and then decreased, indicating that different dissociation reactions occurred at different delay times.(2) Based on the molecular structure and the analysis of the attribution of the ions obtained by time of flight mass spectrometry, possible dissociation paths of different energetic compounds were proposed. By using density functional theory (DFT) of quantum chemical, the structure of the intermediates and the transition states were optimized and the vibration frequencies were calculated at the B3LYP/6-31+G (d, p) level. By comparing the energy barrier for dissociation path, heat release, and the stability of the product, the most favorable dissociation paths for different explosives were confirmed. For PETN, the path of successive elimination of four HONO to generate CO and CH4 was the dominant dissociation reaction. For RDX, after eliminating three HONO, the ring opened to generate three HCN, this dissociation path was most likely to occur. For HMX, after the elimination of four HONO, the ring opened to generate four HCN, it was the main dissociation path. For TNT, ortho nitro and para nitro eliminating three NO by isomerization reaction to form CO, O2 and C6H7 was an energy favor dissociation path. For HNS, the path that ortho nitro eliminate NO through isomerization reaction was prone to happen. We can conclude that if the structures of the energetic compounds were similar, the dissociation paths were similar.(3) Both positive and negative clusters produced by 532 nm laser ablation of NaN3 were detected, ion-molecule (atom) collision reaction can be used to explain the formation mechanism of clusters更多还原