Phase-transition-mediated impact desensitization of FOX-7 at elevated temperatures

Area of Science:

• Materials Science
• Chemical Engineering
• Energetic Materials

Background:

• Mechanical sensitivity reduction in energetic materials is crucial for safety.
• 1,1-diamino-2,2-dinitroethene (FOX-7) is a high-energy material with significant safety concerns.
• Polymorphic transitions offer a potential route for material desensitization.

Purpose of the Study:

• To investigate the temperature-induced polymorphic transition of FOX-7 for desensitization.
• To quantify the reduction in mechanical sensitivity of the β-phase of FOX-7.
• To explore combined strategies for enhanced safety and performance.

Main Methods:

• In-situ X-ray diffraction was used to identify phase transitions.
• Elevated-temperature impact tests measured sensitivity (H50).
• Finite-element thermo-mechanical modeling predicted phase transition kinetics and stress evolution.

Main Results:

• The α to β phase transition of FOX-7, occurring above 116 °C, significantly reduces impact sensitivity.
• At 126 °C, unmodified FOX-7 showed a 57% increase in H50 compared to ambient conditions.
• A polydopamine (PDA) coating with a fluoropolymer (F2314) binder further increased H50 to 111.6 cm at 126 °C.

Conclusions:

• Temperature-induced phase transition engineering is a viable strategy for desensitizing FOX-7.
• Structural reorganization and altered hydrogen bonding in the β-phase enhance energy dissipation.
• Phase-transition engineering offers a promising pathway for developing intrinsically safer high-energy materials.