RESUMO
Traditional lead-based primary explosives present challenges in application to micro-energetics-on-a-chip. It is highly desired but still remains challenging to design a primary explosive for the development of powerful yet safe energetic films. Copper-based azides (Cu(N3)2 or CuN3, CA) are expected to be ideal alternatives owing to their properties such as excellent device compatibility, excellent detonation performance, and low environmental pollution. However, the significantly high electrostatic sensitivity of CA limits its use in micro-electro-mechanical systems (MEMS). This study presents an in situ electrochemical approach to preparing and modifying a CA film with excellent electrostatic safety using a Cu chip. Herein, a CA film is prepared by employing Cu nanorod arrays as precursors. Next, polypyrrole (PPy) is directly coated on the surface of the CA materials to produce a CA@PPy composite energetic film using the electrochemical process. The results show that CuN3 is first generated and gradually oxidized to Cu(N3)2, essentially forming enclosed nest-like structures during electrochemical azidation. The microstructure and composition of the product can be regulated by varying the current density and reaction time, which leads to controllable heat output of the CA from 521 to 1948 J g-1. Notably, the composite energetic film exhibits excellent electrostatic sensitivity (2.69 mJ) owing to the excellent conductivity of PPy. Thus, this study offers novel ideas for the further advances of composite energetic materials and applications in MEMS explosive systems.
RESUMO
The development of green primary explosives has become a "holy grail" of energetic materials research. Cu-based 5-nitrotetrazolate is considered one of the most promising candidates due to its excellent blasting power and environmentally benign nature. However, synthesizing Cu-based 5-nitrotetrazolate controllably and securely remains highly challenging. Herein, room-temperature anodization of metallic Cu and a Cu(I)-imidazole nanowire array on copper substrates in a sodium 5-nitrotetrazolate electrolyte leads to in situ electrosynthesis of Cu(I) 5-nitrotetrazolate (DBX-1, CuNT) and its analogue, Cu(II) 5-nitrotetrazolate [Cu(NT)2], respectively. Both obtained CuNT and Cu(NT)2 films demonstrate remarkable energy output and good laser-induced ignition performance. The thermal stability (Tp = 291 °C) and electrostatic safety (E50 = 2.54 mJ) of CuNT proved to be superior to those of Cu(NT)2 (Tp = 257 °C, and E50 = 0.57 mJ). Remarkably, this study provides an exciting new method for the rational design and development of Cu-based 5-nitrotetrazolate as a primary explosive for advanced initiating applications.
RESUMO
It is highly desired but still remains challenging to design a primary explosive-based nanoparticle-encapsulated conductive skeleton for the development of powerful yet safe energetic films employed in miniaturized explosive systems. Herein, a proof-of-concept electrochemical preparation of metal-organic frameworks (MOFs) derived porous carbon embedding copper-based azide (Cu(N3 )2 or CuN3 , CA) nanoparticles on copper substrate is described. A Cu-based MOF, i.e., Cu-BTC is fabricated based on anodized Cu(OH)2 nanorods, as a template, to achieve CA/C film through pyrolysis and electrochemical azidation. Such a CA/C film, which is woven by numerous ultrafine nanofibers, favorably demonstrates excellent energy release (945-2090 J g-1 ), tunable electrostatic sensitivity (0.22-1.39 mJ), and considerable initiation ability. The performance is superior to most reported primary explosives, since the CA nanoparticles contribute to high brisance and the protection of the porous carbon network. Notably, the growth mechanism of the CA/C film is further disclosed by detailed experimental investigation and density functional theory (DFT) calculation. This work will offer new insight to design and develop a CA-based primary explosive film for applications in advanced explosive systems.