Thermally induced damage in hexanitrohexaazaisowurtzitane

The evolution of the microstructure of hexanitrohexaazaisowurtzitane (CL-20) after a thermal stimulus plays a key role in the performance of CL-20. In the current work, microstructural variations of CL-20 caused by thermal treatment were investigated by X-ray diffraction, in situ variable-temperature optical microscopy, atom force microscopy, and small-angle X-ray scattering. A wave-like process, an abrupt volume expansion, movement, and fragmentation of CL-20 particles during phase transition were observed. After the phase transition (160 °C) the CL-20 sample acquired a very rough surface with numerous dimple depressions, and during the thermal decomposition stage (200 °C) a large number of voids were produced in both the bulk and the surface of the CL-20.