Heat-Induced Solid-Solid Phase Transformation of TKX-50
Heat-Induced Solid-Solid Phase Transformation of TKX-50
复制标题
TKX-50 的热致固相固相变
DOI：
10.1021/acs.jpcc.7b00086
复制
发表时间：
2017-04-20
影响因子：
3.7
通讯作者：
Zhang, Chaoyang
中科院分区：
文献类型：
--
作者：
Lu, Zhipeng;Xue, Xianggui;Zhang, Chaoyang
双羟基铵5，5‘-双四唑-1，1’-二元酸盐(TKX-50)是一种性能优于普通炸药的高能离子盐。通过拉曼光谱和热重-差示扫描量热(TGA-DSC)测量，结合从头计算，我们报道了TKX-50到一个新的亚稳相(Meta-TKX-50)的固-固相变。Meta-TKX-50是由NH3OH+旋转形成的，体积膨胀3%，晶体对称性从P21/C降低到P-1。该相变为二级相变，比热容变化0.3J.K~(-1)·mol~(-1)。比热容的这种微小变化是过去测量中忽略相变的主要原因。此外，相变还促进了NH_3OH~+向C_2O_2N_(82-)的氢转移和NH_3OH~+的N-O键解离，最终生成稳定的小分子NH_3和H_2O。因此，相变可能会促进TKX-50的分解，使其热稳定性变差。
Dihydroxylammonium 5,5 '-bistetrazole-1,1 '-diolate (TKX-50) is an attractive energetic ionic salt and outperforms many common explosives. We report a solid-solid phase transition of TKX-50 to a new metastable phase (Meta-TKX-50) at similar to 180 degrees C by Raman spectroscopy and thermogravimetry-differential scanning calorimetry (TGA-DSC) measurements, in combination with ab initio calculations. Meta-TKX-50 is formed by the rotation of NH3OH+ with a small volume expanding of 3% and a crystal symmetry reduction from P21/C to P-1. In addition, the phase transition features a second order with a slight change of 0.3 J.K-1.mol(-1) in specific heat capacity. This slight change of specific heat capacity is the main reason that the phase transition was overlooked in the past measurements. Besides, it is found that the phase transition facilitates the H transfer from NH3OH+ to C2O2N82- and the N-O bond dissociation of NH3OH+ to produce final small stable molecules including NH3 and H2O. Thus, the phase transition is expected to promote the decomposition of TKX-50 and deteriorate its thermal stability.