Shock wave-induced phase transition in RDX single crystals.

Area of Science:

• Materials Science
• Shock Physics
• Crystallography

Background:

• Hexahydro-1,3,5-trinitro-s-triazine (RDX) is a high explosive sensitive to shock compression.
• Understanding RDX's molecular response under shock is crucial for safety and performance.
• Previous studies have explored static compression effects, but dynamic shock response requires further investigation.

Purpose of the Study:

• To investigate the real-time, molecular-level response of oriented RDX single crystals to shock compression.
• To determine the occurrence and characteristics of phase transitions in shocked RDX.
• To assess the influence of crystal orientation on RDX's response to shock.

Main Methods:

• Utilized Raman spectroscopy, including high-resolution and time-resolved techniques.
• Subjected oriented RDX single crystals ([111], [210], [100]) to stepwise shock loading (3.0–5.5 GPa).
• Analyzed frequency shifts of CH stretching modes and spectral changes at peak stress and during shock reverberation.

Main Results:

• Below 3.5 GPa, CH stretching mode frequency shifts were similar across all orientations.
• Above 4.5 GPa, significant spectral changes indicated an alpha-gamma phase transition, consistent with static compression results.
• No orientation dependence was observed in the molecular response up to 5.5 GPa.
• The alpha-gamma phase transition exhibited an incubation time of ~100 ns at 5.5 GPa.

Conclusions:

• Shock compression induces an alpha-gamma phase transition in RDX crystals above 4.5 GPa.
• The molecular response and phase transition are independent of crystal orientation under shock loading.
• The observed phase transition may be linked to the initiation of chemical decomposition in shocked RDX.