Pressure-Induced Irreversible Phase Transition in the Energetic Material Urea Nitrate: Combined Raman Scattering and X-ray Diffraction Study

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• 作者：Shourui Li ; Qian Li ; Kai Wang ; Mi Zhou ; Xiaoli Huang ; Jing Liu ; Ke Yang ; Bingbing Liu ; Tian Cui ; Guangtian Zou ; Bo Zou
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：January 10, 2013
• 年：2013
• 卷：117
• 期：1
• 页码：152-159
• 全文大小：566K
• 年卷期：v.117,no.1(January 10, 2013)
• ISSN：1932-7455

文摘

In situ high-pressure Raman spectroscopy and synchrotron X-ray diffraction (XRD) have been employed to investigate the behavior of the energetic material urea nitrate ((NH₂)₂COH⁺路NO₃^{鈥?/sup>, UN) up to the pressure of 26 GPa. UN exhibits the typical supramolecular structure with the uronium cation and nitrate anion held together by multiple hydrogen bonds in the layer. The irreversible phase transition in the range 9鈥?5 GPa has been corroborated by experimental results and is proposed to stem from rearrangements of hydrogen bonds. Further analysis of XRD patterns indicates the new phase (phase II) has Pc symmetry. The retrieved sample is 10.6% smaller than the ambient phase (phase I) in volume owing to the transformation from two-dimensional (2D) hydrogen-bonded networks to three-dimensional (3D) ones. The mechanism for the phase transition involves the cooperativity of noncovalent interactions under high pressure and distortions of the layered structure. This work suggests high pressure is an efficient technique to explore the performance of energetic materials, and to synthesize new phases with high density.}