典型含能离子盐中的氢键及其对结构与性能影响的理论研究

发布时间：2018-06-12 14:24

本文选题：TKX-50 + 含能离子盐　；参考：《西南科技大学》2017年硕士论文

【摘要】：含能离子盐具有能量高、感度低以及环境友好等优点,有望取代现有常用的单质炸药。但是,含能离子盐的结构-性能间关系尚不清晰,有待于深入研究。本文以含能离子盐晶体中的氢键为切入点,采用量子化学、从头算分子动力学及晶体结构分析方法研究含能离子盐晶体中氢键对结构与性能的影响机制。首先,二羟基联四唑羟胺盐(TKX-50)是近年合成出来的一种含能离子盐,它具有高能量、高密度、低的撞击感度、低毒性和易合成的优点,有望成为下一代含能材料。与普遍应用的CHON含能材料不同的是,TKX-50具有强的分子间氢键(HBs)。通过从头算分子动力学模拟剪切应变及热分解实验研究强氢键对TKX-50稳定性影响的双面效应。也就是说,一方面,TKX-50中阴阳离子间的强氢键作用形成于(010)面方向,从而形成了较强的层内作用,而相邻层间仅通过两种最弱的氢键连接,这一特性有利于外界动能转换成层间滑移,并降低撞击感度;另一方面,TKX-50晶体中广泛的氢键为H转移(包括质子转移)准备了条件,可加速后期的热分解。因此,氢键一方面有利于降低撞击感度,另一方面又导致热稳定性降低。此外,我们对羟胺盐的晶体结构进行了深入研究,发现用羟胺阳离子成盐可增加含能离子盐的堆积系数和堆积密度。分析表明,羟胺阳离子与阴离子间的分子间强氢键作用是增加含能离子盐密度的主要原因。这种强氢键作用通常存在于羟胺类离子盐中,却罕见于其它离子盐中,在中性含能分子晶体中基本不存在。与其它阳离子相比,羟胺阳离子通过强氢键作用得到高的堆积系数和相对高的晶体堆积密度,弥补了羟胺阳离子相对较低分子密度的不足。此外,与普通炸药中的氢键作用比较分析,我们发现最强氢键越短,堆积系数越大,这表明最强氢键作用可作为堆积系数的简单指标。因此,我们认为增强分子间氢键是增加晶体紧密度的主要方法。总之,在含能离子盐中,强氢键是普遍存在的,本文研究了TKX-50晶体中强氢键的双面作用。在TKX-50晶体的研究基础上,分析了羟胺类离子盐晶体以及不同阳离子的离子盐晶体的氢键作用特点、堆积模式,研究得到结构与性能间的作用机理,有助于理解其他含能离子盐的结构与性能,丰富了含能材料关于感度机理的认识。这些结论为新型高能钝感炸药分子与晶体设计提供了理论支撑。
[Abstract]:Energetic ionic salts have the advantages of high energy, low sensitivity and environmental friendliness. However, the relationship between structure and properties of energetic ion salts is not clear, which needs further study. In this paper, the mechanism of the influence of hydrogen bonds on the structure and properties of energetic ionic salt crystals is studied by means of quantum chemistry, ab initio molecular dynamics and crystal structure analysis. First, TKX-50) is a kind of energetic ion salt synthesized in recent years. It has the advantages of high energy, high density, low impact sensitivity, low toxicity and easy to synthesize. It is expected to become the next generation of energetic materials. Different from the commonly used CHON energetic materials, TKX-50 has a strong intermolecular hydrogen bond. The effects of strong hydrogen bonds on the stability of TKX-50 were investigated by ab initio molecular dynamics simulation of shear strain and thermal decomposition. That is to say, on the one hand, the strong hydrogen bond between anion and anion in TKX-50 is formed in the direction of the 010) surface, thus forming a strong intralayer interaction, while the adjacent layers are connected only by two of the weakest hydrogen bonds. This property is conducive to the conversion of external kinetic energy to interlaminar slip and reduces the impact sensitivity. On the other hand, a wide range of hydrogen bonds in TKX-50 crystal provide the conditions for H transfer (including proton transfer), which can accelerate the thermal decomposition in the later stage. Therefore, the hydrogen bond can reduce the impact sensitivity, on the other hand, it leads to the decrease of thermal stability. In addition, we have studied the crystal structure of hydroxyamine salt. It is found that the accumulation coefficient and density of energetic ion salt can be increased by using hydroxylamine cationic salt. The results show that the strong intermolecular hydrogen bonding between hydroxylamine cations and anions is the main reason for increasing the density of energetic ions. This strong hydrogen bond is usually present in hydroxylamine ionomer salts, but rare in other ionic salts, and almost non-existent in neutral energetic molecular crystals. Compared with other cations, hydroxylamine cations can obtain high stacking coefficient and relatively high crystal packing density through strong hydrogen bonding, which makes up for the shortage of relatively low molecular density of hydroxylamine cations. In addition, compared with the hydrogen bond interaction in the ordinary explosives, we find that the shorter the strongest hydrogen bond, the larger the stacking coefficient, which indicates that the strongest hydrogen bond can be used as a simple index of the stacking coefficient. Therefore, we consider that strengthening the intermolecular hydrogen bond is the main method to increase the density of crystals. In conclusion, strong hydrogen bonds are common in energetic ionic salts. In this paper, the double side interaction of strong hydrogen bonds in TKX-50 crystals is studied. Based on the study of TKX-50 crystal, the hydrogen bonding characteristics and stacking mode of hydroxylamine ion-salt crystal and different cationic ion-salt crystal are analyzed, and the interaction mechanism between structure and properties is obtained. It is helpful to understand the structure and properties of other energetic ionic salts and enrich the understanding of sensitivity mechanism of energetic materials. These conclusions provide theoretical support for the molecular and crystal design of new high energy insensitive explosives.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ560.1

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