Room-Temperature Aqueous Synthesis of Copper Nanoparticles and Their In Situ Conversion to Copper Azides

Copper azides are promising energetic materials for miniaturized pyrotechnic devices and micro explosive trains owing to their short detonation growth distance and high initiation energy. However, controllable preparation of copper nanoparticle precursors and their in situ conversion to copper azides under mild conditions remains challenging. In this study, copper nanoparticles were synthesized via a coordination-assisted aqueous reduction method at room temperature under air atmosphere using nitrilotriacetic acid disodium salt (NTA·H·2Na) as the complexing agent. The resulting nanoparticles were pressed into polyester rings to construct confined precursor structures, and copper azide micro-charges were prepared through in situ gas-solid reaction with HN₃ gas generated from NaN₃ and concentrated phosphoric acid at 60 °C. SEM characterization revealed that the morphological evolution of copper azides followed a three-stage pattern: "product island nucleation, branch/block coalescence growth, and continuous product layer formation and structural reconstruction". Detonation velocity tests using the electrical probe method showed an average value of (5.10 ± 0.07) × 10³ m/s. Flyer impact initiation tests demonstrated that, with a charge thickness of 1.00 mm, both a 30 μm polyimide flyer and a 40 μm titanium flyer could successfully initiate a HNS-IV explosive. The preparation methodology and performance characterization established in this work provide an experimental basis for the application of copper azides in micro-initiation systems.