碱金属叠氮化物和叠氮化银的高压研究

发布时间：2018-05-06 15:27

本文选题：含能材料 + 叠氮化物　；参考：《吉林大学》2017年博士论文

【摘要】：近年来,叠氮化物作为富氮含能材料家族的重要成员,已经成为合成高能量密度材料-聚合氮的理想前驱体。对其进行高压研究将为合成高能量密度材料提供新途径和数据支持。本文主要利用X射线衍射、拉曼散射光谱、红外吸收光谱技术同时结合理论模拟方法,对叠氮化铷(RbN_3)、叠氮化铯(Cs N_3)、叠氮化钠(NaN_3)、以及叠氮化银(AgN_3)进行了系统的高压研究,取得主要成果如下:1.首先,在室温下利用同步辐射光源对叠氮化铷进行了X射线衍射实验,测试最高压力为42.0 GPa。实验结果揭示了RbN_3在6.5GPa和16.0 GPa压力时发生了两次结构相变,相变序列为α-RbN_3→γ-RbN_3→δ-RbN_3。α-RbN_3到γ-RbN_3相变过程中晶胞对称性由四重对称变为两重对称,并伴有叠氮根的重新排布。经分析得γ-RbN_3为具有C2/m空间群的单斜结构。压力继续增加使叠氮根变为能量更稳定的相互垂直结构,晶胞转变为δ-RbN_3相,δ-RbN_3结构为具有P222/Pmm2/Pmmm空间群的正交结构。α-RbN_3呈现出的各向异性的压缩率可归因于叠氮根之间的相互排斥力。计算得到α-RbN_3体弹模量为18.4GPa,与KN_3和Cs N_3相近似。此外,对比碱金属叠氮化物的性质和相变压力点我们发现他们低压相变压力点随其离子键增强而降低。室温下对RbN_3进行了拉曼散射光谱和红外吸收光谱的测试,实验最高压力分别为28.5 GPa和30.2 GPa。结合实验数据与CASTEP计算结果我们对RbN_3所有振动模式进行了全面系统指认。振动光谱随压力的变化情况揭示了样品在6.5GPa和16.0 GPa处发生了两次结构相变。随着压力增加,晶胞发生了α-RbN_3到γ-RbN_3的位移型相变。中红外光谱分析揭示了叠氮根在α-RbN_3→γ-RbN_3→δ-RbN_3的相变过程中出现了由相互垂直→相互平行→相互垂直的排布规律的变化。此外,δ-RbN_3中叠氮根的对称伸缩模式出现红外活性揭示了压力作用下叠氮根离子的线性对称结构被破坏,同时叠氮根在此相中占据两个非等效位置。2.室温条件下利用拉曼散射和红外吸收光谱技术研究了压力对于叠氮化铯(Cs N_3)结构稳定性的影响,最高压力为30.0 GPa。样品分别在0.5 GPa、3.7 GPa以及16.0 GPa时,出现了II→III→IV→V相的三次相变。T(Eg)振动模式的软化行为揭示了II相到III相过程中晶胞的剪切变形。III相中T(Eg)和R(Eg)振动模式的劈裂揭示了叠氮根等效位置的消失。指认出IV相为单斜结构且空间群为C2/m。同时V相的对称性要低于其他各相。中红外光谱中叠氮根弯曲振动模式随压力的演化以及叠氮根对称伸缩振动模式表现出红外活性共同揭示了压力作用下叠氮根离子的旋转和弯折行为象。并且压力持续增加会使叠氮根弯折的程度加大。弯折的叠氮根离子将更有利于降低叠氮化物的聚合压力继而易于形成聚合氮。3.室温下对叠氮化钠(NaN_3)进行了高压拉曼散射光谱和红外吸收光谱的测量,实验最高压力分别为35.0 GPa和26.0 GPa。首先结合实验数据和理论计算结果对常压下所有振动模式进行了系统全面的指认。随着压力增加拉曼散射和红外吸收结果均一致显示NaN_3在0.5GPa、14.0GPa以及27.6 GPa发生了三次结构相变,相变序列为β-NaN_3→α-NaN_3→γ-NaN_3→δ-NaN_3。β-NaN_3到α-NaN_3的相变过程中晶胞出现了剪切形变并伴有叠氮根离子的旋转行为。压力继续增加,内模振动模式的劈裂揭示了γ-NaN_3结构中叠氮根离子出现了非等效的位置。叠氮根的弯曲振动模式出现的异常对称式演化过程揭示了压力下叠氮根离子的旋转行为。此外压力作用会使叠氮根继续旋转为能量更稳定的相互垂直的结构。4.对叠氮化银(AgN_3)进行了高压拉曼散射和红外吸收光谱测试,测试所达到的最高压力分别为24.0 GPa和13.0 GPa。常压下叠氮根的弯曲振动和反对称伸缩振动具有拉曼活性说明其具有非线性或者非对称结构。压力增至2.7 GPa时晶体由正交相结构变成四方相结构。相变后晶体对称性升高使得拉曼散射振动光谱中多组振动模出现了简并重组。红外吸收光谱中v 2(B2u)模式的软化和v 2(B3u)模式的硬化行为揭示了叠氮根离子在压力下的旋转行为。此现象揭示了晶体在a轴方向出现负压缩性以及正交相到四方相结构相变产生的本质原因。此外我们认为四方结构中相互垂直排布的叠氮根离子具有较稳定的能量,使得此结构能保持至较高压力。
[Abstract]:In recent years, as an important member of the family of nitrogen rich energetic materials, azide has become an ideal precursor for the synthesis of high energy density materials - polymerized nitrogen. High pressure research on it will provide new ways and data support for the synthesis of high energy density materials. This paper mainly uses X ray diffraction, Raman scattering, and infrared absorption spectroscopy. At the same time, the theoretical simulation method is used to study the high pressure of rubidium azide (RbN_3), caesium azide (Cs N_3), sodium azide (NaN_3) and silver azide (AgN_3). The main achievements are as follows: 1. first, the X ray diffraction experiment on rubidium azide was carried out by using synchrotron radiation light source at room temperature, and the maximum pressure was 42 GPa. real. The experimental results reveal that RbN_3 has two structural phase transitions at 6.5GPa and 16 GPa pressure. The phase transition sequence is that the cell symmetry changes from four symmetry to double symmetry in the phase transition process of alpha -RbN_3 to [-RbN_3] -RbN_3. a -RbN_3 to gamma -RbN_3, and is accompanied by the rearrangement of azide roots. The pressure continues to increase to make the azide root into a more stable vertical structure with a more stable energy. The cell is transformed into a delta -RbN_3 phase, and the delta -RbN_3 structure is an orthogonal structure with the P222/Pmm2/Pmmm space group. The anisotropic compression rate of alpha -RbN_3 is attributable to the mutual repulsion between the azide roots. The modulus of the alpha -RbN_3 body is calculated to be 18.4GPa, It is similar to KN_3 and Cs N_3. In addition, compared with the properties of alkali metal azides and phase transition pressure points, we found that their low-pressure phase transition pressure points were reduced with their ion bond enhancement. At room temperature, the Raman scattering and infrared absorption spectra of RbN_3 were tested at room temperature, the experimental maximum pressure was 28.5 GPa and 30.2 GPa. combined with experimental data, respectively. With the results of CASTEP, all the vibration modes of RbN_3 are systematically identified. The vibration spectra with the pressure change reveal that the sample has two structural phase transitions at 6.5GPa and 16 GPa. With the increase of pressure, the cell occurs the displacement phase change of the alpha -RbN_3 to the gamma -RbN_3. In the phase transformation process of -RbN_3 - gamma -RbN_3 - -RbN_3, there are changes in the law of vertical, parallel and vertical arrangement. In addition, the symmetrical expansion mode of azide roots in Delta -RbN_3 reveals that the linear symmetry structure of azide ions under pressure is destroyed, and the azide roots occupy two of the phase in this phase. The effect of pressure on the structural stability of caesium azide (Cs N_3) was investigated by Raman scattering and infrared absorption spectroscopy at room temperature at a non equivalent position.2.. The softening behavior of the three phase transition.T (Cs) mode of II to III, IV to V appeared at the highest pressure of 30 GPa. samples at 0.5 GPa, 3.7 GPa and 16 GPa, respectively. The splitting of the shear deformation of the cells in the II phase to the III phase, the splitting of the T (Eg) and R (Eg) modes in the.III phase, reveals the disappearance of the equivalent position of the azide root. The symmetry of the IV phase is monoclinic and the space group is C2/m. and the V phase is lower than the other phases. The nitrogen root symmetrically telescopic vibration model shows that the activity of the azide root ion is rotated and flexed under pressure, and the continuous increase of the pressure will increase the degree of bending of azide roots. The bending of azide ions will be more beneficial to reducing the polymerization pressure of azides and then forming the.3. room at room temperature. The High Pressure Raman scattering and infrared absorption spectra of sodium azide (NaN_3) were measured. The maximum pressure of the experiment was 35 GPa and 26 GPa. respectively. First, all the vibration modes under atmospheric pressure were systematically identified with the experimental data and theoretical calculation. The phase transformation of NaN_3 at 0.5GPa, 14.0GPa and 27.6 GPa occurred in three times. The phase transition sequence was the shear deformation and the rotation of azido root ions in the phase transition process of beta -NaN_3, alpha -NaN_3, gamma -NaN_3 and delta -NaN_3. beta -NaN_3 to alpha -NaN_3. The pressure continued to increase, and the splitting of the internal model vibration mode revealed the gamma -NaN_3 structure. The non equivalent position of azido root ions appears. The abnormal symmetry evolution of the bending vibration mode of azide roots reveals the rotation behavior of the azide root ions under pressure. In addition, the pressure action will continue to rotate the azide roots to a more stable and vertical structure.4. for the High Pressure Raman scattering of AgN_3. The maximum pressure of the azide root under 24 GPa and 13 GPa. atmospheric pressure is measured by the fire and infrared absorption spectra, and the bending vibration of azide roots and the anti symmetric expansion vibration have the nonlinear or asymmetric structure. When the pressure increases to 2.7 GPa, the crystal is transformed from the orthogonal phase to the Quartet phase structure. The behavior of multi group vibration modes in the Raman scattering vibration spectrum is degenerate. The softening of the V 2 (B2u) mode and the hardening behavior of the V 2 (B3u) mode in the infrared absorption spectrum reveal the rotation behavior of the azide ion under pressure. This phenomenon reveals the negative compressibility of the crystal in the direction of the a axis and the structure of the quadrature phase to the Quartet phase. The essential reason for the phase transition is that the azide ions, which are vertically arranged in the Quartet structure, have more stable energy, which keeps the structure at high pressure.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O521

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