Electric field sensitivity of RDX/TNT-CNT composites: a DFT-based assessment of charge-driven breakdown mechanisms and microwave ignition experimental validation

In complex electromagnetic environments, the stability of energetic materials (EMs) encounters substantial challenges. Revealing the evolution of charge structures in EMs under electromagnetic fields is crucial for enhancing their safety. EMs are generally non-magnetic, so the effect of magnetic fields in the system can usually be negligible, with the focus instead on the process of electric fields acting on EMs. To systematically investigate the response characteristics of EMs under electric field, this study employed density functional theory to conduct quantitative calculations on the charge characteristics and chemical bond orders of RDX, TNT and their composites doped with single-walled carbon nanotubes (SWCNTs) of different sizes under different electric field conditions (strength and direction). A method based on the amount of charge transfer is proposed to assess the microwave-sensitivity of each system and estimate the threshold breakdown field strength. These predictions were subsequently validated through microwave resonant cavity ignition experiments conducted on RDX and TNT compositions. Under electric fields, the N–N bonds in the RDX molecule are weakened. The introduction of SWCNT molecules further weakens the C–N bonds, which may facilitate the formation of new reaction pathways. The breakdown field strength of each system can be ascertained based on the amount of charge displacement under an electric field. The threshold breakdown field strengths for RDX and TNT molecules respectively under a strong electric field are on the order of 1 × 10−3 V Å⁻¹. After being doped with carbon nanotubes, TNT shows stronger microwave susceptibility than RDX. This enhanced effect, as well as the predictions about electric fields sensitivity, has been verified through experiments.