Institute for Shock Physics and Department of Physics, Washington State University, Pullman, Washington 99164-2816, USA.
J Phys Chem A. 2010 Aug 12;114(31):8099-105. doi: 10.1021/jp105226s.
Raman spectroscopy and optical imaging were used to determine the phase boundaries between various hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) polymorphs. Experiments were performed on single crystals at pressures up to 8.0 GPa and temperatures ranging from room temperature to 550 K. Several distinct pressure regions were found in the RDX response at elevated temperatures: (i) melting of alpha-RDX followed by decomposition, below 2.0 GPa, (ii) decomposition of alpha-RDX between 2.0 and 2.8 GPa, (iii) irreversible transformation of alpha- and gamma-RDX to epsilon-RDX between 2.8 and 6.0 GPa, and (iv) decomposition of gamma-RDX above 6.0 GPa. A triple point between the alpha-, gamma-, and epsilon-RDX was found at 3.7 GPa and 466 K. The alpha-gamma phase transition was confirmed to occur at the same pressure, approximately 3.7 GPa, regardless of temperature, in the range of 295-460 K. Furthermore, it was determined that epsilon-RDX (i) has limited chemical stability under the pressure and temperature conditions where it is produced and (ii) decomposes according to the autocatalytic rate law. The findings reported here have provided new information about the response of RDX crystals at high pressures and temperatures.
拉曼光谱和光学成象技术被用于确定各种六氢-1,3,5-三硝基-1,3,5-三嗪（RDX）多晶型物之间的相界。在高达 8.0 GPa 的压力和从室温到 550 K 的温度范围内对单晶进行了实验。在高温下，RDX 的响应中发现了几个明显的压力区域：（i）在低于 2.0 GPa 时，α-RDX 的熔化伴随着分解，（ii）在 2.0 至 2.8 GPa 之间，α-RDX 的分解，（iii）在 2.8 至 6.0 GPa 之间，α-和γ-RDX 不可逆地转化为ε-RDX，（iv）在高于 6.0 GPa 时，γ-RDX 的分解。在 3.7 GPa 和 466 K 处发现了α-RDX、γ-RDX 和ε-RDX 之间的三相点。无论温度如何，在 295-460 K 的范围内，α-γ 相变被证实发生在相同的压力下，大约 3.7 GPa。此外，确定ε-RDX （i）在其产生的压力和温度条件下具有有限的化学稳定性，（ii）根据自催化速率定律分解。这里报道的发现为 RDX 晶体在高压和高温下的响应提供了新的信息。
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