In-situ synthesis of copper azide chips and investigation of their initiation ability

Copper azide (CA), an environmentally compatible and highly energetic material, is considered a promising primary explosive for miniaturized explosive systems. Herein, an efficient in-situ synthetic strategy was developed for fabrication of CA chips. Utilizing a nanoporous copper (NPC) chip with interconnected pores and nanoparticles as precursors, a CA chip with a large density and enhanced initiation performance was subsequently fabricated in situ from high concentration gaseous HN₃. The effect of reaction time on the azide reaction was investigated, and a possible mechanism was established for the first time to explain the formation of CA. The reaction between NPC and gaseous HN₃ involved a complex series of processes and included three steps. Cu reacted first with gaseous HN₃ to produce Cu(N₃)₂, and then the Cu(N₃)₂ was reduced by unreacted Cu to produce CuN₃. These two reactions were very fast, and copper conversion reached 87.7% after 12 min. After that, CuN₃ reacted slowly with gaseous HN₃ to form Cu(N₃)₂. Increased reaction times were beneficial for the generation of Cu(N₃)₂ and had an obvious influence on initiation ability. The density of CA reached 2.38 g cm⁻³ after 26 h. Furthermore, the CA chip was further assembled into a micro-initiation device, which successfully detonated the HNS-IV explosive. The mass of CA was less than 0.75 mg, and the thickness was 0.4 mm under the preferred conditions. CA synthesized by this method achieved the same initiation performance as the charge size was reduced to the fullest extent possible, which offers more advantages in the application of miniaturized explosive systems.