Isothermal structural evolution of CL-20/HMX cocrystals under slow roasting at 190 °C

Area of Science:

• Materials Science
• Chemical Engineering
• Energetic Materials

Background:

• Cocrystal explosives, like CL-20/HMX, offer high energy density and low sensitivity.
• Understanding their decomposition behavior is crucial for safe handling and application.
• Previous studies noted a decomposition temperature of 235 °C for CL-20/HMX cocrystals at faster heating rates.

Purpose of the Study:

• To investigate the isothermal structural evolution of CL-20/HMX cocrystals at 190 °C.
• To elucidate the decomposition mechanism of CL-20/HMX cocrystals at sub-decomposition temperatures.
• To provide insights into the safety characteristics of CL-20/HMX cocrystal explosives.

Main Methods:

• Isothermal roasting of CL-20/HMX cocrystals at 190 °C.
• Analysis of structural changes and decomposition pathways using advanced characterization techniques (implied).
• Monitoring gas product evolution and crystal phase transformations.

Main Results:

• Initial decomposition of CL-20 occurs via separation from the (010) plane.
• Gas products (NO2, NO) escape, forming microbubbles and holes.
• Residual HMX recrystallizes into δ-phase HMX, causing a 72% volume shrinkage.
• Gully-like structures form on the (010) plane with prolonged heating.
• Complete decomposition of CL-20 and full recrystallization to δ-HMX observed after extended heating.
• The interaction between CL-20 and HMX significantly slows the decomposition rate compared to pure CL-20.

Conclusions:

• The decomposition of CL-20/HMX cocrystals at 190 °C involves a complex interplay of CL-20 decomposition and HMX recrystallization.
• The observed slower decomposition rate enhances the safety profile of these energetic materials at temperatures below their recognized decomposition point.
• This research deepens the understanding of cocrystal energetic material stability and safety.