Decompression-triggered chemical reactions in high-energetic materials– Dr. Lei Su

A team led by Dr. Lei Su at SHARPS reports the first experimental evidence of decompression-induced chemical decomposition in the high explosive CL-20 at room temperature. Using in situ infrared spectroscopy and molecular dynamics simulations, the study reveals that mechanical shear stress during pressure release triggers bond cleavage at 26.2 GPa under nonhydrostatic conditions – 13% lower than hydrostatic compression (30.1 GPa). Key gaseous products (N₂O and CO₂) were identified, fundamentally altering safety paradigms for energetic materials. These findings were published in JACS (DOI: 10.1021/jacs.5c06401).

Energetic materials like CL-20 are critical for defense and aerospace applications but exhibit unpredictable sensitivity under extreme conditions. While temperature-driven decomposition is well-studied, pressure effects were assumed negligible:

Traditional view: CL-20 remains chemically stable up to 60 GPa during compression. 

Knowledge gap: Decompression pathways were ignored, assuming full reversibility.

Critical problem: Nonhydrostatic stress in real-world scenarios (e.g., munitions manufacturing) could lower reaction thresholds, posing unrecognized risks.

Caption: Chemical reaction of CL-20 after the compression-decompression cycle under nonhydrostatic pressure conditions.

The team demonstrated a novel chemical reaction in CL-20, triggered during decompression from a peak pressure of 26.2 GPa under non-hydrostatic conditions. Infrared spectroscopy confirmed chemical bond cleavage, yielding gaseous decomposition products primarily composed of N₂O and CO₂. Molecular dynamics (MD) simulations revealed that the initial decomposition steps involved H migration, OH transfer, β-scission of the C-C bridge, and cleavage of C-N bonds. "Decompression can no longer be considered a benign process. Our work proves that mechanical energy alone can initiate reactions in condensed explosives at ambient temperatures." explained Dr. Su.

近日，由上海前瞻物质科学研究院、北京高压科学研究中心、南京理工大学、北京计算数学与应用物理研究所、南开大学等单位组成的研究团队，通过原位红外光谱与分子动力学模拟，首次证实含能材料CL-20（六硝基六氮杂异伍兹烷）在卸压过程中发生化学分解，产生N₂O和CO₂气体。该反应在非静水压条件下阈值压力仅26.2 GPa，显著低于此前普遍认为 CL-20 在高达 60 GPa 压力下仍具有化学稳定性的认知；而使用KBr作为传压介质的静水压条件下，反应阈值上升至30.1 GPa。这一差异揭示了剪切应力是诱发 CL-20 化学反应的关键因素，对含能材料在极端加载环境下的安全性评估具有重要意义。该研究成果发表在《美国化学会志》(Journal of the American Chemical Society)，DOI: 10.1021/jacs.5c06401。