Copper Azide Research Articles

Study on CL-20 Initiated by Flyer Driven by Copper Azide

Abstract A simulation model of copper azide microcharge driving flyer initiation microscale CL-20 explosive was established, and the action process of copper azide detonation driven flyer initiation microscale CL-20 explosive was numerically simulated by ANSYS/LS-DYNA fluid-structure interaction algorithm. The internal pressure and velocity changes of the flyer during the detonation of copper azide and the internal pressure change of the CL-20 explosive during the detonation were studied. The results show that the error between the experimental and numerical simulation results of the average speed of the flyer is within 10%. This provides a feasible solution for the study of the micro-explosion detonation mechanism by simultaneously analyzing the explosion process of the multi-physical field change law. The numerical simulation results are consistent with the experimental results, indicating that the established simulation model can be used to simulate the detonation process of CL-20 initiated by a flyer driven by copper azide. The copper azide charge, with a diameter of 1 mm and a charge thickness of 0.6 mm, successfully initiates the detonation of the CL-20 explosive.

Airborne metal nanoparticles released by azides detonation: determination and potential public exposure

Metal azides are highly energetic materials that release a large amount of gas upon detonation. They also release metal particles, generating an aerosol. The most common azide is sodium azide (NaN3), which is used nowadays in car airbags. If the decomposition is not complete, harmful azide particles might be inhaled. Heavy metal azides find application as a primary explosive (primer) in ammunition. Public health officials have raised concerns about heavy metal particles released during training in shooting ranges. We identify a lack of knowledge on airborne metal particles properties released from azide detonation and on the analytical methods applied to characterize them. As a case study, we detonated milligram amounts of silver azide, copper azide, and a mixture of them in a glove box. We then analyse the airborne particles with an ensemble analytical setup, able to measure real-time their particle size distribution and chemical composition. We detected spherical metal nanoparticles in the range of 2–500 nm. These findings and the developed analytical tools may allow identifying airborne nanoparticles the passenger compartments of vehicles after airbag activation as well as in indoor shooting ranges, contributing to the evaluation of public health risks.

Synthesis and protection: a controllable electrochemical approach to polypyrrole-coated copper azide with superior safety for MEMS.

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.

Development of an Energetic Material Information Self-Destruction Microsystem Based on Bistable Off-On Actuator Composed of Fusible Alloy

The physical self-destruction of an information storage chip (ISC) driven by a detonation wave generated using energetic materials is an important method to ensure the security of key core information. To solve the related problems of high electrostatic sensitivity, poor overcurrent capability, and easy erroneous triggering, a bistable off-on actuator (BO-OA)-based energetic material information self-destruction microsystem is proposed based on a fusible alloy. First, the BO-OA model based on the fusible alloy is constructed. By performing a finite element numerical analysis and experimenting, the response time of the Bi-Sn alloy with a continuous temperature rise from 22°C to 138°C is obtained. Second, a model of the energetic material dose and detonation wave transmission in an air domain is constructed. An analysis using LS-DYNA software indicates that copper azide can produce GPa-level stress waves in a millimeter-level air domain to realize ISC physical self-destruction. Finally, through bulk silicon processing and in situ reaction of the energetic materials, self-destruction module preparation and functional integration are realized. Experiments and simulations show that when driven by a 12 V electromotive force, the BO-OA reaches the fusible alloy melting point of 138°C within 320 μs, and can realize electrical conduction within 33 μs. 0.45 mg of copper azide can generate a 3.27 GPa detonation wave within 5.9 μs at 0.3 mm in the air domain to realize the physical self-destruction of the ISC. This scheme can greatly improve the safety of the energetic materials and provides strong practical value for information self-destruction.

A new strategy to prepare high-performance copper azide film for micro-initiator.

Copper azide (CA) has gradually become the chosen priming agent for microexplosive devices as a lead-free green priming agent. However, charge loading is challenging due to its high electrostatic sensitivity, severely limiting its practical application. In this study, copper hydroxide particles were evenly coated on the surface of carbon fiber using electrospinning and quick hot-pressing, and CA-based composites with uniform load were created using the in-situ azide technique while keeping good film characteristics. The produced CA-HP film has an electroostatic sensitivity of 3.8 mJ, which is much higher than the raw material of 0.05 mJ. The flame sensitivity has also been increased from 45 cm to 51 cm, and the use safety has been considerably enhanced. Furthermore, hot-pressed CA-HP films can improve the film's qualities, such as easy cutting and processing into the required shape, compatibility with MEMS processes, and the ability to successfully detonate secondary explosives with only 1 mg. This novel coupling technology expands the possibilities for developing high-safety primers for micro-initiator.

Investigation of the noncovalent interactions of the Cu (II) amine complex with flexible aromatic moiety to the interaction with bovine serum albumin

In crystallographic studies, non-covalent interactions are identified based on which atom is involved. A more accurate and quantitative idea can be obtained from the Hirshfeld surface (HS) analysis of the crystal structure of the molecule. The crystal structure of the synthesized Cu(II) complex (azidobis(N-benzylethylenediamine)copper(II) azide) with N-benzylethylenediamine was investigated to identify all the non-covalent interactions present in the crystal. Apparently, the hydrogen bond was the leading force in constructing the crystal from the crystallographic study, and this idea was overruled by HS analysis. The HS study indicates van der Walls interactions majorly contribute to crystal formation. Again, the high energy gap between HOMO and LUMO showed the inertness of the molecule toward chemical reactions. The conformational analysis of the molecule showed that the Cu(II) complex has a flexible phenyl ring and covalent azide, which makes the complex adjustable according to the environment. All these features of the complex make it a good candidate for interaction with proteins. In the presence of bovine serum albumin (BSA), the complex preferred to go into the hydrophobic site of the protein from water due to its van der Walls interactions preference. The interaction of the complex with BSA was investigated with multi-spectroscopic methods like UV–vis, fluorescence, circular dichroism, and time-resolved fluorescence lifetime. The experimental results also support the theoretical prediction that the binding of the complex with BSA is through hydrophobic interactions. Molecular docking results also indicate the hydrophobic interactions play the BSA-complex conjugation.

Copper Azide-based Complexes without Repulsive Steric Clashes between Azides for Advanced Primary Explosives

Primary explosives are essential energy transfer materials in explosive systems. At present, heavy metal-containing materials, such as lead azide (LA), are still the most widely used primary explosives. Copper azide (CA)-based primary explosives are considered as promising replacements for LA. However, there has little advancement in the high initiation performance and high safety of CA-based primary explosives because of the absence of the relevant theories and structural models. Herein, we report [Cu(N3)(2-bmttz)]n1 with the exceptionally remarkable initiating capability and high safety. Performance tests indicated only 5 mg of 1 can successfully ignite the commercial secondary explosive RDX, as 1/6 priming charge of LA, demonstrating 1 is possibly the most efficient primary explosive known to date. Moreover, 1 possesses the rarely low impact sensitivity (IS = 2.5 J), which is comparable to that of LA and better than most of reported CA-based candidates. Both experimental and theoretical studies have shown that passivation of high-energy primary explosives can be achieved through the coordination between functional ligands and azide ions, in which azide ions without repulsive steric clashes only act as energetic building blocks. This work offers a new insight for designing high performance primary explosives for applications in advanced explosive systems.

Reactive antistatic additive modified copper(II) azide as a primary explosive with simultaneously enhanced stability and energy

The emergence of micro-priming systems expedites the demand for balancing the inherent contradiction between energy and safety in primary explosives. This paper proposes a new strategy (metal organic framework/reactive antistatic agent strategy, MOF/RAA strategy) which introduces the reactive antistatic agent (WO3) into ternary copper azide /carbon activity system by carbonization and azide of polyoxometalate-based metal–organic frameworks. Subsequent characterization validates that the novel reactive multi-component system (ternary copper azide /carbon/tungsten trioxide) performs well with both high electrostatic safety and remarkable detonating ability (detonate CL-20 as low as 0.98 mg) due to the electrical conductivity and active participation in secondary reaction of reactive antistatic agent (WO3). In general, this discovery has obtained prominent achievements in the application of copper azide in micro-initiating systems, providing a safe yet energy simultaneously enhanced way for the design and synthesis of novel energetic compounds.

Core–Shell Copper Azide-Based Nanofiber Films Prepared by Coaxial Electrospinning for MEMS Microinitiators

The main bottleneck preventing powders from being used in a microinitiation system is the paradox between safety and detonation performance, as well as powders’ inherent brittleness and difficulty in shaping. To address this problem, we used the coaxial electrospinning technology to design and fabricate a core–shell film (CA@C–D) with low sensitivity and high energy. Electrostatic sensitivity (E50 = 5.22 mJ) and flame sensitivity (H50 = 51 cm) are both significantly lower than those of the raw copper azide (CA) material and can detonate secondary explosives. Extensive characterization and experiments show that the unusual core–shell structure of coaxial electrostatic spinning fibers is responsible for this significant improvement. This high specific surface area carbon shell wraps around the CA particles, providing double protection, while the superior thermal and electrical conductivity of the carbon material helps improve system safety and maintains the azide output performance. More importantly, it always maintains a good film structure and is simple to process, meeting the actual requirements of MEMS initiators and introducing a new scheme for the preparation of film-based initiators.

Effect of Electrostatic Discharge (ESD) on Heat Response Performance of NiCr Micro-heater

The NiCr micro-heater is a key element of MEMS-based electro-explosive device (mEED), while electrostatic discharge (ESD) may excite the micro-heater accidentally. To discover mechanism that how the ESD excitations effect on heat response performance of NiCr micro-heater, electro-thermal conversion process was numerically modelled by using commercial software. Three different shapes of micro-heaters, including rectangular, V-shape and square ones, are designed, and a series of simulation models are built under ESD events of 25kV, 5000Ω, 500pF and 25kV, 500Ω, 150pF. Heat response performance of NiCr micro-heater with different shapes and sizes were numerically computed under the said ESD events and compared with. The critical safety value at which LTNR and copper azide would not be ignited accidentally were calculated according to the fitted formulas. Conclusions are that maximum temperature decreases exponentially with increase of width of rectangular micro-heater, decreases exponentially with increase of wm and α of V-shape micro-heater, and decreases exponentially with increase of length or width of square micro-heater. The ESD event of 25kV, 500Ω, 150pF is a more severe case for micro-heater than ESD event of 25kV, 5000Ω, 500pF. These results could supply critical data to guide the design of MEMS -based EED for ESD protection.

Study on microcharge design and output performance test

Taking copper azide microcharge as research object, PVDF piezoelectric sensor was used to test the detonation pressure of copper azide microcharge and the detonation pressure of titanium flyer driven by copper azide microcharge explosion respectively. The effect of titanium flyers on the output performance of copper azide microcharge was investigated. The research results shown that: different microcharge structure parameters affected charge weight, and the charge weight directly affected the output pressure. The output pressure of copper azide microcharge to drive titanium flyer is much greater than the output pressure of copper azide microcharge. Titanium flyer driven by copper azide microcharge explosion, which could play the role of energy gathering and amplification.

Influence of Micro Initiation Train parameters on critical detonation thickness of medium

In this paper, copper azide of 2mm in diameter was exerted as the burster, and the study object was the micro initiation train of Cl20-based explosive that generated by flyer plate impacting the medium in the accelerating chamber. Results shows that: the thickness of critical burst increased with the thickness of flyer plate.Simulation calculation and experimental verification were conducted to study the parameter influence of flyer plate and accelerating chamber on the critical burst thickness of medium. which could serve as a reference for the design of MEMS products. The larger diamete of accelerating chamber was conducive to forming the stable detonation inside the explosive, and the critical burst thickness of the medium increased accordingly.The thickness of critical burst increased with the length of acceletating chamber.

Research on Energetic Micro-Self-Destruction Devices with Fast Responses.

Information self-destruction devices represent the last protective net available to realize information security. The self-destruction device proposed here can generate GPa-level detonation waves through the explosion of energetic materials and these waves can cause irreversible damage to information storage chips. A self-destruction model consisting of three types of nichrome (Ni-Cr) bridge initiators with copper azide explosive elements was first established. The output energy of the self-destruction device and the electrical explosion delay time were obtained using an electrical explosion test system. The relationships between the different copper azide dosages and the assembly gap between the explosive and the target chip with the detonation wave pressure were obtained using LS-DYNA software. The detonation wave pressure can reach 3.4 GPa when the dosage is 0.4 mg and the assembly gap is 0.1 mm, and this pressure can cause damage to the target chip. The response time of the energetic micro self-destruction device was subsequently measured to be 23.65 μs using an optical probe. In summary, the micro-self-destruction device proposed in this paper offers advantages that include low structural size, fast self-destruction response times, and high energy-conversion ability, and it has strong application prospects in the information security protection field.

Constructing Highly Reliable and Adaptive Primary Explosive Composites for Micro-Initiator Assisting by a Hybrid Template of Metal-Organic Frameworks and Cross-Linked Polymers.

Primary explosive, as a reliable initiator for secondary explosives, is the central component of micro-initiators for modern aerospace systems and military operations. However, they are typically prepared as powders, posing potential safety risks because of the inevitable particles scattering issues in the actual working environments. Here, the fabrication of a highly adaptive bulk material of copper azide (CA)-based safe primary explosive for micro-initiators is demonstrated. This bulk material, as derived by a complete azidation reaction of the carbonized metal-organic framework/cross-linked polymer hybrid template, enables the firm embedding of active CA species in a cross-linked carbon network (denoted as CA-C). Interestingly, this CA-C bulk material demonstrates multifarious mechanical stabilities (e.g., good shock and vibration resistance, and anti-overload capacity) in the simulated working conditions. Meanwhile, the CA contents in the CA-C bulk material reached as high as 70.3%, ensuring its detonation power. As a proof of concept, CA-C bulk material assembling in a micro-detonator can efficiently detonate the secondary explosive of CL-20 under laser irradiation. This work hereby advances the fabrication of safe and powerful primary explosives for the fulfillment of safe micro-initiator in a broad range of applications in aerospace systems.

A Highly Effective Liquid-Solid Reaction for In Situ Preparation of Copper Azide.

Copper azide (CA) is a promising energetic material with characteristics of high energy output and environmental friendliness that can be used as a microinitiator charge, but the extreme sensitivities hinder its practical applications. In situ preparation of CA can avoiding operating on sensitive CA directly and depressed the risk of handling. However, it is still a challenge to develop a straightforward, high-efficiency in situ preparation method. Consequently, a simple and rapid liquid-solid reaction strategy for azidation has been proposed via the in situ transformation of Cu(OH)2 into CA in a hydrazoic acid aqueous solution. In situ preparation of CA on a Cu film was performed to demonstrate the application of this strategy in detail. The transformation was completed in 4 min, which significantly improved the efficiency for production of CA compared to previously reported methods. This work provides a facile and highly efficient method for the in situ preparation of CA.

Core‐Shell Hetero‐Framework derived Copper Azide Composites as Excellent Laser‐Ignitable Primary Explosives

AbstractLaser initiation has attracted increasing interest owing to its extraordinary safety and high reliability. However, traditional metal complex‐based laser‐ignitable primary explosives are limited by high input laser energy and low detonation ability. In this study, an efficient laser‐ignitable primary explosive‐based copper azide is prepared by constructing core‐shell hetero‐framework Cu‐MOF@COF as the precursor. The pyrolysis of Cu‐MOF@COF hybrid material affords copper azide (CA) nanoparticle confined in a porous carbon shell, referred to CA@C Shell. The evenly coated porous carbon shell functions as light‐to‐heat conversion layer efficiently promoting the laser initiation process of inside CA. Consequently, CA@C Shell can be initiated at lower laser energy thresholds (0.80 mJ at 1064 nm). This value is significantly lower than typical laser ignitable metal complex tetraamine‐cis‐bis(5‐nitro‐2H‐tetrazolato‐N2)cobalt(III)perchlorate (726 mJ at 808 nm). Moreover, the CA@C Shell successfully detonates the secondary explosives CL‐20 by laser energy when it is assembled in a micro‐detonator system. This study offers a unique method for constructing high performance laser‐ignitable primary explosives for micro‐detonator applications.

Fabrication of electrostatic safety copper azide film with in situ growing MOF

Due to its extremely low electrostatic sensitivity, copper azide primary explosive is greatly limited in practical applications. In this study, a composite film with Cu-MOF in-situ growth on carbon nanofilm was prepared by electrospinning and solvothermal methods, and CNF@Cu–N3 film with electrostatic safety was obtained by carbonization and azide later. Its electrostatic sensitivity (E50) was greatly increased from 0.05 mJ of raw materials to 4.06 mJ, and still maintained a good detonation performance which could successfully detonate the CL-20 secondary explosive. This is mainly due to the synergistic effect of the carbon film and the MOF structure, which greatly improves the conductivity of the entire system and the uniform distribution of copper particles, providing a new preparation strategy for metal azide film that is suitable for the micro-initiator device.

Recovering copper ions from wastewater with chitosan to synthesize lead-free primary explosives

Chitosan (CTS) is a well-known adsorbent capable of absorbing copper ions. It's also a high-quality biomass carbon source. The carbon skeleton formed by the pyrolysis of CTS has outstanding electrical conductivity, which can help copper azide (CA), a new type of primary explosive that's particularly sensitive to electrostatic stimuli, be more electrostatically safe. The CTS-Cu complex is precipitated by using CTS to adsorb and flocculate copper ions in wastewater. To construct the Cu@carbonized chitosan (CCTS) precursor material, the organic ligands in the CTS-Cu complex are calcined into a porous three-dimensional carbon matrix, and the copper ions are transformed into copper nanoparticles embedded in CCTS. The azide reaction converts copper nanoparticles (CuNPs) into high-energy CA. With its good electrical conductivity, CCTS maintains its framework structure and effectively improves the electrostatic safety of composite energetic materials. CA@CCTS has a CA content of 69.7%, an electrostatic ignition energy (E 50 ) of about 1.19 mJ, and a heat release of 1803.22 J/g. This work takes advantage of CA and CTS's environmental friendliness. CA@CCTS, as a novel lead-free primary explosive, has good electrostatic safety while containing a high proportion of CA. • The CTS-Cu complex is precipitated by using CTS to adsorb and flocculate copper ions in wastewater. • The Cu@CCTS precursor is constructed by carbonizing the CTS-Cu complex. • The Cu@CCTS precursor is converted to CA@CCTS via a gas-solid phase azide reaction. • CA@CCTS has a CA content of 69.7%, an 50% electrostatic ignition energy (E 50 ) of about 1.19 mJ.

Energetic properties of copper azide nanoparticles encapsulated within a conductive porous matrix via electrosynthesis

The copper-based azide (CA), as a sustainable alternative to currently-used primary explosives, will play a critical role in the deployment of miniature initiating systems owing to its outstanding blasting power and environmentally benign nature. However, a secure and controlled synthesis still remains challenging for the high-performance CA-based energetic film. Here, a conductive metal–organic framework (MOF) of cuprous 7,7,8,8-tetracyanoquinodimethane (CuTCNQ) is employed as a template for the electrochemical preparation of the CA nanoparticles encapsulated with conductive porous matrix. Impressively, the composition, morphology, energetic characteristics (1090 ∼ 2780 J·g−1) and electrostatic sensitivity (0.19 ∼ 12.3 mJ) of such CA/CuTCNQ energetic films can be easily tuned by carefully adjusting current density and azidation time in order to achieve the tailored energy release in the form of combustion or detonation. Furthermore, density functional theory (DFT) calculations provide valuable insights for the electrochemical azidation mechanism of the CA/CuTCNQ film. This work pioneers a new pathway to develop the CA composite film as an interesting energetic material for advanced initiating applications.

Information self-destruction module design based on micro thermoelectric power generation and energetic materials

Information self-destruction modules (ISDMs) play a vital role in the information security area. In this paper, an ISDM based on the integration of a micro-thermoelectric generation mechanism (M-TEGM) with energetic materials (EMs) is proposed. On the basis of energy conversion relationship, an open-loop electromotive force is induced, and this energy will drive the EMs to release the detonation wave and realize information storage module self-destruction. During the tests, under the temperature difference (100 K), the open-loop electromotive force (3.86 V) is induced by the M-TEGM and can drive the EMs (0.37 mg copper azide) to generate a detonation wave (GPa) in 3.4 μs, which can physically destroy the information storage modules. This ISDM has advantages that include rapid response times, low drive energy compared with traditional information security technology.