The Behavior of Phase Transition and Thermal Decomposition on CL-20/DNB Cocrystals under Extreme Conditions

CL-20/DNB cocrystal has been discovered as a promising explosive owing to its excellent comprehensive performance. The cocrystal molecular formula is C12H10N14O16, and its unit cell structure belongs to the orthorhombic system with space group Pbca. The cocrystal has a unique structure formed by orderly arrangement of CL-20 and DNB molecules through hydrogen bonds and nitro-aromatic interactions, which makes it effectively achieve a fine balance between energy and sensitivity. In this work, the thermal decomposition behavior and structural evolution of CL-20/DNB cocrystal under high temperature and high pressure were studied by means of thermogravimetric differential heating, Raman spectroscopy and X-ray diffraction. The study found that the process of decomposition on sample can be divided into three stages, namely an endothermic melting stage and two exothermic decomposition stages. It can be concluded that the co-crystallization can adjust the explosive melting point and improve its thermal stability. And the stability of cocrystal under compression is also significantly higher than that of CL-20. Additionally, there is a structural phase transition at the pressure range of 13-14 GPa, which is accompanied by a color change of the sample and a red shift of the absorption edge.