Interfacial coupling dielectric-magnetic heterojunction network C-CoFe/CNTs on HMX via recrystallization for rapid microwave ignition and enhanced combustion

Microwaves serve as a non-contact external energy source capable of enabling simultaneous multi-point ignition and enhanced combustion of energetic materials (EMs) by indirectly coupling electromagnetic energy into both their condensed phase and flame zone via microwave-to-heat conversion materials, which offers the potential to break through the intrinsic chemical energy limitation of EMs. However, the low dielectric property of EMs leads to poor microwave coupling efficiency. Herein, taking 1,3,5,7-Tetraaza-1,3,5,7-tetranitrocyclooctane (HMX) as a typical inert explosive, a C-CoFe alloy/CNTs dielectric-magnetic heterojunction network (NCCF) derived from CoFe-MOF was coated on HMX via recrystallization, where NCCF serves as a microwave-to-heat bridge at the interface and acts as a high-energy fuel that intensifies combustion. XPS revealed that recrystallization promotes the intermolecular coupling and interfacial polarization between NCCF and HMX. HMX@NCCF-8 (800 °C-derived alloy, 15 wt%) achievers a shortest ignition delay of 17.63 ms, breaking through the limitation that pure HMX cannot be ignited under identical microwave irradiation. Thermal analysis indicated that the recrystallization strategy and alloy serving as a high-energy fuel promote stable self-sustained combustion of HMX with enhanced flame brightness. Electromagnetic characteristics indicate that HMX@NCCF-8 and HMX@NCCF-9 enhanced the intrinsic microwave absorption of HMX (-1.04 dB), improving minimum reflection loss (RL min ) by ~2000% and ~3300% with effective absorption bandwidths (EABs) of 4.2 and 2.9 GHz, respectively. This electromagnetic coupling paradigm offers a universal route for tunable microwave responses in propellants and explosives.