Energetic Films Research Articles

Combustion and thermodynamics properties of erythritol tetranitrate-based energetic films composed by electrospinning nano fibers

ABSTRACT High energy composite films made from high explosives has important applications in pyrotechnics. In this study, electrostatic spraying was used to prepare energy-containing films based on 1,2,3,4-butanetetrol tetranitrate (ETN). The results show that all energy containing films are made of nanofibres. They have excellent hydrophobicity and combustion properties. In particular, monolayer films in which ETN is the main energy containing substance. Once ignited, the trace monolayer film generates a maximum pressure of 0.85 MPa and an adiabatic flame temperature of 2,855 °C. For single and double layer films, the heat of combustion can reach 9899 J/g and 11975 J/g respectively. The level of combustion heat can also be controlled by adjustment of the ETN content. The results of the thermo-properties performance evaluation show that by optimizing the nanostructure, the ETN-based energy-containing fiber membranes can meet the requirements of advanced pyrotechnic products. In particular, there is great potential in the metastable intermixed composites (MICs) field.

Effect of copper in the stabilization of Al/CuO energetic semiconductor bridge

The long-term storage performance of energetic multilayer nanofilms is of great significance for their applications. In this paper, it is proposed to add a 10 nm Cu barrier layer between Al/CuO composite films to increase their storage stability. The Al/CuO composite film and Al/Cu/CuO composite film were aged for 14 days in an environment with a relative humidity of 40% and a temperature of 71 °C. Scanning electron microscopy and differential scanning calorimetry were used to analyze the microstructure and thermodynamic properties of the energetic films before and after aging, and the electrical detonation performance and ignition ability of energy-containing semiconductor bridges were studied. The results indicate that after aging for 14 days in an environment with a relative humidity of 40% and a temperature of 71 °C, the Al layer of the Al/CuO composite film becomes thinner, the Al2O3 interface layer increases, and the heat release decreases. The interlayer microstructure of the Al/Cu/CuO energetic multilayer nanofilms did not change significantly, and the addition of a 10 nm Cu layer formed a low-temperature Al–Cu alloy, reducing the reaction initiation temperature from 626 to 570 °C. The critical ignition time and critical ignition energy of the Al/CuO-energetic semiconductor bridge (ESCB) increased, the flame duration shortened from 440 to 300 μs, the flame size decreased by 50%, the plasma temperature decreased, and aging had no significant effect on the electrical explosion performance of Al/Cu/CuO-ESCB. After aging for 14 days in an environment with a relative humidity of 40% and a temperature of 71 °C, the maximum ignition gap of B/KNO3 for Al/CuO-ESCB decreased from 1.4 to 1.2 mm, while the maximum ignition gap for Al/Cu/CuO-ESCB remained at 1.6 mm, which significantly improved the ignition performance and long storage performance of the energetic semiconductor bridge.

In-situ synthesis of MEMS compatible Al/Cu2HIO6/PVDF Metastable composites film with high combustion performance

To address the challenges related to significant pressure loss and weakened combustion performance of energetic materials when ignited on Micro-Electro-Mechanical Systems (MEMS), periodate-based MICs (Metastable Intermolecular Composites) have emerged as promising candidates due to their high energy density and combustion pressure. However, the integration of periodate-based MICs onto MEMS has not been effectively achieved thus far. Herein, we propose a simple, environmentally friendly, and cost-effective approach to fabricate a MEMS-compatible Al/Cu2HIO6/PVDF (polyvinylidene difluoride) energetic composite film. Our method involves utilizing a Cu(OH)2 array as a template and employing an in-situ and spin-coating process. The resulting Al/Cu2HIO6/PVDF film was characterized using various techniques including SEM, TEM, XRD, and XPS. These analyses reveal a tightly packed nano array morphology with a porous structure. DSC-TG analysis was conducted to investigate the thermal reaction of the Al/Cu2HIO6/PVDF composite film. The results demonstrate that the thermal reaction involved a complex multi-step process, with higher heat release (1121 J g-1), a faster reaction rate, and a lower initial reaction temperature (294.5 °C) compared to the Al/CuO/PVDF composite film. the reaction process of Al/Cu2HIO6/PVDF film was also been proposed by analyzing the products at different temperatures. combustion diagnostic tests were carried out to evaluate the combustion performance of the Al/Cu2HIO6/PVDF composite film. The results indicate that as CuO transformed into Cu2HIO6, the film exhibits a reduced ignition delay (8 ms) and combustion duration (50 ms), higher combustion temperature (3710 K), and stronger flame intensity (8630 a.u.).

Fabrication of Al@AIH@PVDF metastable composite film with enhanced laser ignition ability and combustion performance

Laser ignition technology has garnered significant attention for energetic materials in recent years, offering advantages over traditional electrical initiation methods, notably in mitigating issues related to stray currents and electromagnetic interference. Moreover, it can facilitate multi-point synchronous ignition. However, the persistent challenges of high ignition thresholds and delays in energetic materials necessitate effective resolutions. In this study, we address these challenges by converting the inert Al2O3 layer on the surface of aluminum powder into the active compound Aluminum Iodate Hexahydrate ([Al(H2O)6](IO3)3(HIO3)2, AIH) to prepare an Al@AIH@PVDF energetic composite film (ECF) with the aim of reducing the laser ignition threshold and delay of Al@PVDF ECF. The Al@AIH@PVDF ECF was synthesized through a simple wet chemistry method and a rapid evaporation process suing a simple, environmental-friendly, and cost-effective way. Differential scanning calorimetry-thermogravimetric analysis (DSC-TG) results demonstrate a lower exothermic reaction temperature (161 °C) and higher heat release (2900 J g−1) for Al@AIH@PVDF ECF. Laser ignition tests reveal a reduced laser ignition delay (11 ms) and threshold (1.59 J cm−2) for Al@AIH@PVDF ECF. Combustion experiments showcase elevated combustion flame temperature (3090 K), burning rate (4.11 cm s−1), and smaller condensed combustion products, while effectively igniting CL-20. Pressure tests indicate higher maximum combustion pressure (3.24 MPa) and pressure rise rate (4.05 GPa s−1) for Al@AIH@PVDF ECF. Finally, the reaction process and mechanism of Al@AIH@PVDF ECF was also investigated and proposed.

Bio-inspired design of PTFE/B energetic materials with high reactivity and flexibility

Although new-type energetic materials have been investigated extensively, there is a challenge on how to integrate energy density and mechanical properties of energetic materials simultaneously. Herein, a versatile approach was proposed to design energetic materials with high energy density, reactivity, and flexibility based on a bio-inspired strategy. By mimicking the “brick-and-mortar” structure within a natural nacre, the energetic film with alternative layers of polytetrafluoroethylene (PTFE) and boron (B) was successfully fabricated. The nacre-mimetic PTFE/B energetic film exhibited excellent reaction heat (4413.9 J⋅g−1) and bright combustion flame, which may originate from the exothermic reaction mechanism between fluorine (F) and B. Even more remarkably, such PTFE/B energetic film revealed prominent mechanical flexibility reported for the first time. These findings indicate that the nacre-mimetic strategy provides an effective route to engineer energetic materials with high energy density, reactivity, and flexibility.

Novel hydrophobic Ti-PVDF energetic thin films with excellent mechanical and ignition properties and their reaction mechanisms

With the development of traditional aluminum(Al)-based nanothermites, some problems on account of the metal Al powder gradually emerged. Therefore, extensive research is devoted to exploring novel metal fuels to achieve better energy release effects. Titanium (Ti) powder is a potential metal fuel theoretically considering of reducibility and calorific value, but it has rarely been reported in the field of nanothermites. This paper put forward the design strategy by selecting as the metal fuel and polyvinylidene fluoride (PVDF) as oxidant. According to the hydrophilicity of Ti powders, the PVDF film encapsulation can effectively improve hydrophobicity and storage stability. Another advantage of PVDF film state is that it imparts excellent mechanical properties (yield strength of 30.5 MPa and elongation at break of 202.8 %). According to the results of thermal analysis, Ti increased the thermal stability of PVDF while accelerated its thermal decomposition rate. In ignition properties, Ti-PVDF films have the shortest ignition delay time (217 ms) lower than results reported in the literature of other nanothermites under the same conditions. In addition, the energy release process of ignition combustion is analyzed and verified in this paper. Therefore, Ti-PVDF energetic ignition material with diverse properties is expected to be applied in more fields not limited to nanothermites.

Flexible conductive energetic film based on energetic ionic liquids and carbon nanotubes for information security transient electronics

Transient electronics is an emerging class of functional electronics designed to address problems such as potential data leakage and information theft. In order to meet the unification of transient technology and electronics, we prepared a flexible conductive energetic film by assembling energetic ionic liquids (EILs) loaded single-walled carbon nanotubes (SWNTs) and CuO functionalized multi-walled carbon nanotubes (MWNTs). It was found that the interaction between EILs and SWNTs maintains the high conductivity of SWNTs and strengthens the flexibility of the film. The introduce of CuO functional MWNTs enhance the detonation performance of the films by catalyzing EILs combustion. Therefore, obtained flexible conductive energetic film has good conductivity (63.67 S/cm), high energy release (8037 kJ/kg), and high flexibility (1000 bends). It is confirmed that flexible conductive energetic film can meet the requirement of low-voltage operation and high-voltage self-destruction by replacing traditional circuit in an electronic device. The prepared transient chip is able to ignited in 10 ms and completely self-destruct within 0.7 s.

Electrophoretic assembly of Al/CuBi2O4 based-energetic films and the effect of destructive behavior with fuel/oxidant ratio

Physical destruction of microchips for data security based on thermite cannot simultaneously fulfill the demands of energy release and pressure output. Here, we have successfully assembled microchips based on Al/bimetallic oxide (CuBi2O4) energetic films through electrophoretic deposition. Al/CuBi2O4exhibits excellent energy release and pressure output, the heat release of Al/CuBi2O4is more concentrated,as extensive heat released by Al/CuO triggered the reaction of Al and Bi2O3, which will be conducive to the destructive behavior. The effects of fuel and oxide with different ratios on exothermic performance were systematically investigated, including heat release, ignition threshold energy, ignition mass loss rate and pressure release. The best fuel/oxide ratio on Al/CuBi2O4 energetic films is found to be 5.06:1 through inductively coupled plasma atomic emission spectrometry. The distribution between Al fuel and CuBi2O4rods is the most uniform at this ratio, hence it possesses the maximum heat release (926.4 J/g), lower ignition threshold (0.25 mJ), and faster pressurization rate (179.80 MPa/s). Importantly, high-speed photography results show that the intense reaction destroyed the energetic microchip (the thickness is about 0.3 mm) in only 10 ms.

A novel fluorine-free design of superhydrophobic nano-Al/NiO (II) energetic film with promising exothermic performance

It is still a big challenge to design self-protected energetic films or coatings due to the performance degradation under wet conditions, even underwater using environmentally friendly techniques. Thus, this paper firstly proposed an environment-protecting method to fabricate a superhydrophobic nano-Al/NiO energetic film with uniformly distributed structures and high purity via an improved electrophoretic assembly and stearic acid modification. The nano-Al/NiO energetic film with a high contact angle (CA) of 166° displayed superior anti-wettability and self-cleaning ability, and the outstanding exothermic performance of product keeps almost stable even after 10 complete immersion cycles, demonstrating the promising practicality. Our design provide a novel strategy for substantially extending safety, flexibility and adaptability of functional energetic surfaces in real industrial applications.

Al/CuO@CNFs Conductive Flexible Energetic Films with High Electrical Safety.

The development of energetic materials with both high energy and high safety has always been the focus of the field of energetic materials. In this paper, a low-current-sensitivity flexible energetic film composed of carbon nanofibers (CNFs)-coated Al/CuO metastable intermolecular composites (MICs) was prepared by a blow-spinning combined with controlled heat treatment technique. Hotspots can hardly generate in this kind of energetic film due to the increased electrical and thermal conductivity, leading to low sensitivity of MICs. It evenly stays at a high voltage (60 V) for 24 h without raising the temperature significantly. The energetic films keep the high energy release of MICs due to the additional violent reactions between CuO and CNFs as well as the light weight of CNFs, showing the heat release of 2864 J/g. In addition, the obtained films exhibit good mechanical properties and can maintain the structural integrity after 1000 cycles of repeated bending to a 6 mm curvature radius. The above characteristics reveal that energetic films presented in this paper have certain safety, high energy, and flexibility and have potential applications in transient electronics with flexible requirements such as micro-electromechanical system.

Thermal decomposition behavior and kinetic study of nitrocellulose in presence of ternary nanothermites with different oxidizers

Nanothermites have recently attracted a great deal of interest in both military and civilian domains owing to their capability of igniting or exploding and releasing a significant quantity of heat via a redox reaction. In this study, three ternary nanothermites, which contain MgAl alloy as fuel and different metal oxides (MXOY = CuO, NiO, TiO2) as oxidizers, were prepared through the arrested reactive milling technique. These metastable intermolecular composites were introduced to nitrocellulose (NC), using a fast solution drying technique, to assess their catalytic behavior. The as-obtained energetic composites, namely, NC/MgAl-MXOY, were scrutinized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The ignition delay time of NC/MgAl-MXOY composite films was also determined, and the results revealed the positive effect of the introduction of nanothermite through the decrease of its value compared to pure NC. Using the isoconversional kinetic analysis, the Arrhenius parameters associated with the thermal decomposition of the as-obtained NC/MgAl-MXOY energetic composites films were also evaluated. The findings indicated that the choice of the oxidizer within the nanothermite composition significantly influences the decomposition behavior of the NC/MgAl-MXOY energetic composites. Based on the obtained results, the MgAl-CuO nanothermite provides better performance than MgAl-NiO and MgAl-TiO2 nanoparticles.

Self-destructive microchip: Support-free energetic film of BiOBr/Al/Bi2O3 nanothermites and its destructive performance

Private information protection of electronic chips which store large amounts of sensitive data, is a crucial issue in electromechanical systems nowadays. Here, a self-destructive microchip based on an instantaneous thermite reaction is designed to prevent the leakage of electronic information. The device is consisted of a silicon test wafer and an upper energetic film coated by a simple drop-casting technique. A series of Al/BiOX-based nanothermites have been prepared for decreasing the reaction sensitivity, meanwhile optimizing the destruction efficiency of the energetic film system. Among them, Al/Bi2O3 nanothermite containing 30 wt% BiOBr possesses a low sensitivity (45 J), the maximum pressure peak (1.93 MPa) and pressure effect duration due to multiple interactions of the three nano-scale energetic components. Besides, the energetic film prepared by this nanothermite fomula also exhibits a more effective destruction of the device. The high-speed photography results demonstrate that the violent reaction shatters the thick energetic microchip (∼1 mm) within merely 0.5 ms. Importantly, the efficient destruction of energetic microchips shows excellent reproducibility in different working scenes, including Air or Ar atmosphere. It is believed that this self-destructive device with environmentally friendly components and simple but adaptive design can be extensively used in various electric microcomponents.

In situ synthesis of [Cu(BODN)·5H2O]n@nano-Al composite energetic films with tunable properties in pyro-MEMS.

Integrating energetic materials with microelectromechanical systems (MEMS) to achieve miniaturized integrated smart energetic microchips has broad application prospects in miniaturized aerospace systems and civil explosive systems. In this work, MEMS compatible [Cu(BODN)·5H2O]n arrays and [Cu(BODN)·5H2O]n@nano-Al composite energetic films were successfully fabricated on copper substrates by the in situ reaction method and drop-coating method. Single crystal X-ray diffraction, powder X-ray diffraction, scanning electron microscopy, infrared spectroscopy, differential thermal analyses, and pulsed laser ignition were employed to characterize the prepared samples. The results show that [Cu(BODN)·5H2O]n arrays formed by the coordination reaction between the Cu(OH)2 template and the BODN ligand exhibit a porous supramolecular structure with excellent thermal and energy properties. Their morphology and composition on a copper substrate can be effectively regulated by adjusting the reaction time and solution concentration. In addition, adjustable energetic properties of [Cu(BODN)·5H2O]n@nano-Al composite films can be achieved after the encapsulation of nano-Al. Their heat release, flame height and ignition duration can reach as much as 1987.5 J g-1, 13.2 mm, and 5900 μs, respectively, indicating that [Cu(BODN)·5H2O]n@nano-Al can be used as an excellent pyrotechnic agent in MEMS ignition chips. Overall, this work provides a reference for the integration and application of energetic materials in MEMS systems.

Cryogel-Templated Fabrication of n-Al/PVDF Superhydrophobic Energetic Films with Exceptional Underwater Ignition Performance.

The rapid heat loss and corrosion of nano-aluminum limits the energy performance of metastable intermolecular composites (MICs) in aquatic conditions. In this work, superhydrophobic n-Al/PVDF films were fabricated by the cryogel-templated method. The underwater ignition performance of the energetic films was investigated. The preparation process of energetic materials is relatively simple, and avoids excessively high temperatures, ensuring the safety of the entire experimental process. The surface of the n-Al/PVDF energetic film exhibits super-hydrophobicity. Because the aluminum nanoparticles are uniformly encased in the hydrophobic energetic binder, the film is more waterproof and anti-aging. Laser-induced underwater ignition experiments show that the superhydrophobic modification can effectively induce the ignition of energetic films underwater. The results suggest that the cryogel-templated method provides a feasible route for underwater applications of energetic materials, especially nanoenergetics-on-a-chip in underwater micro-scale energy-demanding systems.

Selectively deposited MEMS-compatible DNTF/PDMS-EC based energetic film and its characterization

ABSTRACT In this work, a novel MEMS-compatible energetic film consisting of 3,4-bis(3-nitrofurazan-4-yl)furoxan(DNTF)/ polydimethylsiloxane(PDMS)-ethyl cellulose (EC) was prepared on an aluminum substrate by inkjet printing. The dense layered energetic film was prepared by stepwise layer-by-layer deposition and thermal curing, its maximum elastic modulus reached 9.865 GPa in the nanoindentation test, and the strong adhesion between the energetic film and the substrate was confirmed by drop experiments. Most importantly, the critical detonation thickness of the energetic film is 0.15 mm in a 1 mm width wedge-shaped groove.

Preparation and characterization of energetic composite films with mutual reactions based on B/PVDF mosaic structure

In this study, to solve the boron oxide (B2O3) formed on the boron (B) surface, which reduces the reactivity and energy release. The energetic composite films with mutual reactions of B as fuel and polyvinylidene fluoride (PVDF) as oxidant are designed, based on the mosaic structure. Then, samples with different contents of B are successfully prepared by the novel synergistic emulsification and transient freezing methods. The morphology and composition results show that B is embedded in PVDF films, which makes the energetic composite films have excellent hydrophobicity and oxidation resistance. Interesting, the thermal analysis results show that in the low-temperature stage, the addition of B advances the initial decomposition temperature of PVDF; in the high-temperature stage, the gas product hydrogen fluoride (HF) of PVDF decomposition has a pre-ignition reaction (PIR) with B2O3, which destroys the shell of B2O3 and accelerates the oxidation of internal active B. And the heat release of 50 % B content is the highest (3845.4 J/g). Furthermore, the ignition and combustion results show that all samples can be ignited smoothly and easily. But the combustion performance is greatly affected by the content of B. Finally, the reaction mechanism of samples is preliminarily obtained by molecular model through the characterization of combustion products. These results show that composite films with mutual reactions based on B/PVDF mosaic structure have an excellent prospect for application in thermite with fluoropolymer.

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.

Exploring the Interfacial Reaction of Nano Al/CuO Energetic Films through Thermal Analysis and Ab Initio Molecular Dynamics Simulation.

The effect of the interface layer on energy release in nanoenergetic composite films is important and challenging for the utilization of energy. Nano Al/CuO composite films with different modulation periods were prepared by magnetron sputtering and tested by differential scanning calorimetry. With the increase in the modulation period of the nano Al/CuO energetic composite films, the interface layer contained in the energetic composite film decreased meaningfully, increasing the total heat release meaningfully. Ab initio molecular dynamics (AIMD) simulation were carried out to study the preparation process changes and related properties of the nano Al/CuO energetic composite films under different configurations at 400 K. The results showed that the diffusion of oxygen atoms first occurred at the upper and lower interfaces of CuO and Al, forming AlOx and CuxAlyOz. The two-modulation-period structure changed more obviously than the one-modulation-period structure, and the reaction was faster. The propagation rate and reaction duration of the front end of the diffusion reaction fronts at the upper and lower interfaces were different. The Helmholtz free energy loss of the nano Al/CuO composite films with a two-modulation-period configuration was large, and the number of interfacial layers had a great influence on the Helmholtz free energy, which was consistent with the results of the thermal analysis. Current molecular dynamics studies may provide new insights into the nature and characteristics of fast thermite reactions in atomic detail.

Simultaneously Altering the Energy Release and Promoting the Adhesive Force of an Electrophoretic Energetic Film with a Fluoropolymer.

Energetic coatings have attracted a great deal of interest with respect to their compatibility and high energy and power density. However, their preparation by effective and inexpensive methods remains a challenge. In this work, electrophoretic deposition was investigated for the deposition of an Al/CuO thermite coating as a typical facile effective and controllable method. Given the poor adhesion of the deposited film and the native inert Al2O3 shell on Al limiting energy output, further treatment was conducted by soaking in a Nafion solution, which not only acted as a fluoropolymer binder but also introduced a strong F oxidizer. It is interesting to note that the adhesion level of Al/CuO films was improved greatly from 1B to 4B, which was attributed to Nafion organic network film formation, like a fishing net covering the loose particles in the film. Combustion and energy release were analyzed using a high-speed camera and a differential scanning calorimeter. A combustion rate of ≤3.3 m/s and a heat release of 2429 J/g for Al/NFs/CuO are far superior to those of pristine Al/CuO (1.3 m/s and 841 J/g, respectively). The results show that the excellent combustion and heat release properties of the energetic film system are facilitated by the good combustion-supporting properties of organic molecules and the increase in the film density after organic treatment. The prepared Al/NFs/CuO film was also employed as ignition material to fire B-KNO3 explosive successfully. This study provides a new way to prepare organic-inorganic hybrid energetic films, simultaneously altering the energy release and enhancing the adhesive force. In addition, the Al/NFs/CuO coating also showed considerable potential as an ignition material in microignitors.

Copper Azide Nanoparticle-Encapsulating MOF-Derived Porous Carbon: Electrochemical Preparation for High-Performance Primary Explosive Film.

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.