Laser-driven flyers (LDF), which can launch the flyer on the interaction of a laser pulse with a thin film of metal, have been widely used in many fields, such as ignition, space scrap metal science, and dynamic high-pressure physics. However, at present, further development of LDF is being hindered by the high reflectivity of the ablation layer and low energy utilization efficiency of LDF on the fiber end face. Herein, improved LDFs were designed and fabricated by mask plate and magnetron sputtering. Improved LDF incorporates a Ti/Al composite film as the ablation layer, while the flyer layer features a smaller diameter round platform design. Reflectivity of samples under static and dynamic conditions and driving characteristics of samples were tested using an optical isolator and photonic doppler velocimetry system. The velocity of the improved LDFs reaches 1.7 km/s with a peak acceleration of 8.7 × 1010 m/s2. LDF with a Ti/Al composite film as the ablation layer demonstrates a static absorption rate of 59%, which gradually increases to 65% under laser irradiation. This absorption rate is notably higher compared with the static absorption rate (20%) and the peak absorption rate under laser irradiation (40%) of an Al layer. Consequently, there is a substantial improvement of about 35% in the flyer velocity. In contrast to the plane-shaped LDF, the velocity profile of the flyer and impact crater morphology suggest that the step-shaped LDF offers a 15% improvement in velocity and a 50% increase in acceleration, with better flyer integrity observed.
The interest in development of non-graphitic polymeric carbon nitrides (PCNs), with various C-to-N ratios, having tunable electronic, optical, and chemical properties is rapidly increasing. Here the first self-propagating combustion synthesis methodology for the facile preparation of novel porous PCN materials (PCN3-PCN7) using new nitrogen-rich triazene-based precursors is reported. This methodology is found to be highly precursor dependent, where variations in the terminal functional groups in the newly designed precursors (compounds 3-7) lead to different combustion behaviors, and morphologies of the resulted PCNs. The foam-type highly porous PCN5, generated from self-propagating combustion of 5 is comprehensively characterized and shows a C-to-N ratio of 0.67 (C3 N4.45 ). Thermal analyses of PCN5 formulations with ammonium perchlorate (AP) reveal that PCN5 has an excellent catalytic activity in the thermal decomposition of AP. This catalytic activity of PCN5 is further evaluated in a closer-to-application scenario, showing an increase of 18% in the burn rate of AP-Al-HTPB (with 2 wt% of PCN5) solid composite propellant. The newly developed template- and additive-free self-propagating combustion synthetic methodology using specially designed nitrogen-rich precursors should provide a novel platform for the preparation of non-graphitic PCNs with a variety of building block chemistries, morphologies, and properties suitable for a broad range of technologies.
Metastable intermixed composites (MICs) have received increasing attention in the field of energy materials in recent years due to their high energy and good combustion performance. The exploration of ways of improving their potential release of heat is still underway. In this study, Al-CuO/graphene oxide (GO) nanocomposites were prepared using a combination of the self-assembly and in-suit synthesis methods. The formulation and experimental conditions were also optimized to maximize the exothermic heat. The DSC analysis shows that the addition of the GO made a significant contribution to the exothermic effect of the nanothermite. Compared with the Al-CuO nanothermite, the exothermic heat of the Al-CuO/GO nanocomposites increase by 306.9-1166.3 J/g and the peak temperatures dropped by 7.9-26.4 °C with different GO content. The reaction mechanism of the nanocomposite was investigated using a DSC and thermal reaction kinetics analysis. It was found that, compared with typical thermite reactions, the addition of the GO changed the reaction pathway of the nanothermite. The reaction products included CuAlO2. Moreover, the combustion properties of nanocomposite were investigated. This work reveals the unique mechanism of GO in thermite reactions, which may promote the application of carbon materials in nanothermite.
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.
Pyrotechnic systems, also termed pyrotechnics, refer to a broad family of sophisticated single-use devices that are able to produce heat, light, smoke, sound, motion, and/or a combination of these thanks to the reaction of an energetic material (primary and secondary explosives, powders/propellants, and other pyrotechnic substances) [...].
Lead azide (LA) is a commonly used primary explosive, the detonation growth of which is difficult to study because it is so sensitive and usually has a small charge size in applications. We used photon Doppler velocimetry (PDV) and calibrated polyvinylidene fluoride (PVDF) gauges to reveal the detonation growth in LA, which was pressed in the confinements with controlled heights. The particle-velocity profiles, output pressure, unsteady detonation velocity, reaction time, and reaction-zone width were obtained and analyzed. Three phases of detonation propagation of LA microcharges are discussed. The volume reactions occur at the beginning of detonation in LA microcharges without forming complete shock profiles. Then the shock front is fast with a slow chemistry reaction zone, which is compressed continuously between the height of 0.8 mm and 2.5 mm. Finally, the steady detonation is built at a height of 2.5 mm. The stable detonation velocity and CJ pressure are 4726 ± 8 m/s and 17.12 ± 0.22 GPa. Additionally, the stable reaction zone time and width are 44 ± 7 ns and 148 ± 11 µm. The detailed detonation process has not previously been quantified in such a small geometry.
Energetic materials (EMs) are the core materials of weapons and equipment. Achieving precise molecular design and efficient green synthesis of EMs has long been one of the primary concerns of researchers around the world. Traditionally, advanced materials were discovered through a trial-and-error processes, which required long research and development (R&D) cycles and high costs. In recent years, the machine learning (ML) method has matured into a tool that compliments and aids experimental studies for predicting and designing advanced EMs. This paper reviews the critical process of ML methods to discover and predict EMs, including data preparation, feature extraction, model construction, and model performance evaluation. The main ideas and basic steps of applying ML methods are analyzed and outlined. The state-of-the-art research about ML applications in property prediction and inverse material design of EMs is further summarized. Finally, the existing challenges and the strategies for coping with challenges in the further applications of the ML methods are proposed.
Hydrolases , Machine Learning
Integrating energetic materials with a microelectromechanical system (MEMS) to achieve miniaturized integrated smart energetic microchips is promising. The potential applications include actuation in lab-on-a-chip devices, ignition in automobile airbags, propulsion and attitude control of micro-/nano-satellites, and miniaturized electro-explosive devices. In this work, a new type of MEMS-compatible energetic arrays was in situ realized on a copper substrate, which comprised a new energetic coordination polymer (ECP; Cu1.5C2N8O2·H2O) with tunable nanostructures and a nano-aluminum (nano-Al) covering layer. The composition, morphology, and energetic characteristics of the energetic arrays can be easily tuned by adjusting the reaction time. The maximum heat release of 1850.2 J/g in thermal analysis and the intense flame in open burning experiment proved its excellent exothermic and combustion performance. A closed-bomb experiment further revealed that the ECP@nano-Al energetic arrays supported on Cu(OH)2 nanorods had a peak pressure (5.5 MPa) and a pressure duration (0.5 s) more than twice those of nanoscale Al/CuO powder because of the introduction of gas elements (e.g., C, H, and N). A preliminary impulse experiment was also conducted through the torsion pendulum method. The displacement of the torsion pendulum in the micrometer scale proved the potential application of the energetic arrays in micropropulsion systems. Overall, this work can serve as a reference for the synthesis and applications of ECPs.
Energetic materials, including explosives, pyrotechnics, and propellants, are widely used in mining, demolition, automobile airbags, fireworks, ordnance, and space technology. Nanoenergetic materials (nEMs) have a high reaction rate and high energy density, which are both adjustable to a large extent. Structural control over nEMs to achieve improved performance and multifunctionality leads to a fascinating research area, namely, nanostructured energetic materials. Among them, core-shell structured nEMs have gained considerable attention due to their improved material properties and combined multiple functionalities. Various nEMs with core-shell structures have been developed through diverse synthesis routes, among which core-shell structured nEMs associated with explosives and metastable intermolecular composites (MICs) are extensively studied due to their good tunability and wide applications, as well as excellent energetic (e.g., enhanced heat release and combustion) and/or mechanical properties. Herein, the preparation methods and fundamental properties of the abovementioned kinds of core-shell structured nEMs are summarized and the reasons behind the satisfactory performance clarified, based on which suggestions regarding possible future research directions are proposed.
In this paper, microchip exploding foil initiators were fabricated by micro-electro-mechanical system scale fabrication methods, such as magnetron sputtering, photolithography, and chemical vapor deposition. A small-scale capacitor discharge unit based on the metal-oxide-semiconductor controlled thyristor was designed and produced to study the performance of the microchip exploding foil initiator. The discharge performance of the capacitor discharge unit without load and the effect of protection devices on the metal-oxide-semiconductor controlled thyristor were studied by the short-circuit discharge test. Then, the electric explosion characteristic of the microchip exploding foil initiator was also conducted to study the circuit current, peak power, deposited energy, and other parameters. Hexanitrostilbene refined by ball-milling and microfluidic technology was adopted to verify the initiation capability of the microchip exploding foil initiator triggered by the metal-oxide-semiconductor controlled thyristor. The results showed that the average inductance and resistance of the capacitor discharge circuit were 22.07 nH and 72.55 mΩ, respectively. The circuit peak current reached 1.96 kA with a rise time of 143.96 ns at 1200 V/0.22 µF. Hexanitrostilbene fabricated by ball-milling and microfluidic technology was successfully initiated at 1200 V/0.22 µF and 1100 V/0.22 µF, respectively.
Since copper azide (Cu(N3)2) has high electrostatic sensitivity and is difficult to be practically applied, silicon-based Cu(N3)2@carbon nanotubes (CNTs) composite energetic films with higher electrostatic safety were fabricated, which can be compatible with micro-electro mechanical systems (MEMS). First, a silicon-based porous alumina film was prepared by a modified two-step anodic oxidation method. Next, CNTs were grown in pores of the silicon-based porous alumina film by chemical vapor deposition. Then, copper nanoparticles were deposited in CNTs by electrochemical deposition and oxidized to Cu(N3)2 by gaseous hydrogen azide. The morphology and composition of the prepared silicon-based Cu(N3)2@CNTs energetic films were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The electrostatic sensitivity of the composite energetic film was tested by the Bruceton method. The thermal decomposition kinetics of the composite energetic films were studied by differential scanning calorimetry (DSC). The results show that the exothermic peak of the silicon-based Cu(N3)2@CNTs composite energetic film is at the temperature of 210.95 °C, its electrostatic sensitivity is significantly less than that of Cu(N3)2 and its 50% ignition energy is about 4.0 mJ. The energetic film shows good electric explosion characteristics and is successfully ignited by laser.
The oxide shell of Al nanoparticles (Al NPs) prevents further reaction of Al/CuO nanothermites which reduces Al utilization efficiency and the performance of the nanothermites. However, the performance of Al/CuO nanothermites can be improved by adding ammonium perchlorate (AP). In this work, in order to confirm and explain the enhancement mechanism of AP on Al/CuO nanothermites, Al/CuO/NC and Al/CuO/NC/AP composites were prepared using the electrospray method. The composites were characterized by differential scanning calorimetry/thermogravimetric, x-ray diffraction, scanning electron microscope and transmission electron microscopy. Meanwhile, the ignition temperature and the time-resolved analysis of the rapid pyrolysis chemistry of the composites were tested using T-jump and time-of-flight mass spectrometry, respectively. The results show that Al NPs of Al/CuO/NC/AP composite are hollow compared to Al/CuO/NC composite after reaction. Al NPs and CuO NPs reduce the decomposition temperature and facilitate the rapid decomposition of the AP, and the decomposition products of the AP can destroy the oxidation layer of Al NPs. This result facilitates the further conduct of the thermite reaction. A mutually reinforcing relationship exists between the Al/CuO/NC composites and AP.
Nanothermites composed of nano-fuels and oxidants are attractive energetic materials, which have potential applications in microscale energy-demanding systems. Herein, nano-Al/CuO with nitrocellulose (NC) binder have been bottom-up assembled on semiconductor bridge (SCB) chip by electrospray, from nanoparticles to three-dimensional (3D) deposited structure. The morphological and compositional characterization confirms the constituents in Al/CuO@NC are homogeneously mixed at nano scale and the 3D structure at micro scale is tunable. The as-deposited Al/CuO@NC exhibits excellent energy output and superior chemical reactivity. Specifically, the heat release of Al/CuO@NC (1179.5 J g-1) is higher than that of random mixed Al/CuO (730.9 J g-1). Benefiting from outstanding exothermic properties, the material integrated with SCB initiator chip (Al/CuO@NC-SCB) for potential ignition application was investigated. The Al/CuO@NC-SCB micro energetic initiator can be functioned rapidly (with delay time of 2.8 µs) and exhibits superb ignition performances with violent explosion process, high combustion temperature (4636 °C) and successful ignition of B/KNO3 propellant, in comparison to SCB initiator. The strategy provides promising route to introduce nano reactive particles into various functional energy-demanding systems for potential energetic applications.
A green primary explosive with high energy density and electrostatic safety was synthesized in this work. A precursor consisting of wrinkled reduced graphene oxide sheets wrapped around copper nanowires (CuNWs@rGO) was fabricated through a facile one-pot hydrothermal approach. The as-prepared precursor was deposited on a silicon wafer by electrophoretic deposition technology, which significantly reduced the safety risks of directly handling the powder sample in the azide reaction. Wrinkled rGO sheets wrapped around copper azide nanowires (CANWs@rGO) were prepared in situ by reaction of the precursor with HN3 gas. The initiation capability was tested by using it to detonate hexogen (RDX) against a lead plate with a thickness of 5 mm, and its detonation performance was found to be better than that of commercial diazodinitrophenol (DDNP). The electrostatic sensitivity of the CANWs@rGO composite was investigated, and the result shows that the discharge energy at 50% (E 50%) of CANWs@rGO was 0.96 mJ, which indicates that it has a much higher electrostatic safety than that of pure copper azide (0.05 mJ).
Three types of reactive multilayer films (RMFs) were integrated to the energetic flyer plates (EFPs) by depositing TiO2, MnO2, and CuO onto aluminum films with different modulation periods using magnetron sputtering technology in this study. The effects of the laser ignition property and laser reflectivity on the RMFs and the thermal behavior of the RMFs were analyzed and compared with those of a single-layer Al film. A high-speed video, photonic Doppler velocimetry (PDV), and a thermal analysis were utilized to characterize the flame morphology, EFP velocity, and chemical thermal behavior, respectively. The surface reflectivities of the TiO2/Al, MnO2/Al, and CuO/Al layers were measured using laser reflectivity spectrometers. The results showed that RMFs with smaller modulation periods exhibited excellent laser ignition performances, and EFP with MnO2/Al had the best performance. These RMFs achieved flame durations of 120-220 µs, maximum flame areas of 7.523-11.476 mm2, and reaction areas of 0.153-0.434 mm2 (laser-induced with 32.20 J/cm2). Flyer velocities of 3972-5522 m/s were obtained in the EFPs by changing the material and modulation period of the RMFs. Furthermore, the rate of the chemical reaction and laser energy utilization were also enhanced by reducing the modulation period and using different material. This behavior was consistent with a one-dimensional nanosecond-laser-induced plasma model. The RMFs of MnO2/Al exhibited the highest level of energy release and promoted laser energy utilization, which could better improve the performance of laser ignition for practical application.
Although the motivation of AlH3 enhancing combustion were recognized in many research, the promotion mechanism have been rarely explored. Herein, a previously unreported porous layer mechanism when combustion were determined in HTPB/AlH3 fuels by SEM, thermo-analysis and a new simplified calculation method, owing to rapidly released gas phase H2 from AlH3 dehydrogenation exposing in melting layer. 5/10% 40-80 µm and 10% 80-200 µm AlH3-HTPB formulas show the regression rate increase by, 25.7%, 29.0% and 43.0% at Gox = 350 kg/m2·s, while by 57.2%, 42.0% and 44.2% enhancement at Gox = 150 kg/m2·s. The low AlH3 content (≤ 10%) promotes the regression rate obviously, while excess AlH3 content (≥ 20%) promotes slightly as a result of comprehensive factors combined by energy release, a certain porous layer mechanism, aggregated Al2O3 attached on the burning surface and the blocking effect of the gaseous released H2. A new model predicting the overlapping process of AlH3 dehydrogenation and Al oxidation in air atmosphere was developed by superimposing AlH3 dehydrogenation simulation and corresponding separated Al oxidation simulation. A 1.5th Avrami-Erofeev (A-E) simulation was proposed for Al passivation weight gain between 420 and 520 K with an activation energy of 124.92 kJ/mol and the pre-exponential of 10^12.35.
Trace detection of explosives has been an ongoing challenge for decades and has become one of several critical problems in defense science; public safety; and global counter-terrorism. As a result, there is a growing interest in employing a wide variety of approaches to detect trace explosive residues. Spectroscopy-based techniques play an irreplaceable role for the detection of energetic substances due to the advantages of rapid, automatic, and non-contact. The present work provides a comprehensive review of the advances made over the past few years in the fields of the applications of terahertz (THz) spectroscopy; laser-induced breakdown spectroscopy (LIBS), Raman spectroscopy; and ion mobility spectrometry (IMS) for trace explosives detection. Furthermore, the advantages and limitations of various spectroscopy-based detection techniques are summarized. Finally, the future development for the detection of explosives is discussed.
Reactive multilayer films (RMFs) can be integrated into semiconducting electronic structures with the use of microelectromechanical systems (MEMS) technology and represent potential applications in the advancement of microscale energy-demanding systems. In this study, aluminum/molybdenum trioxide (Al/MoO3)-based RMFs with different modulation periods were integrated on a semiconductor bridge (SCB) using a combination of an image reversal lift-off process and magnetron sputtering technology. This produced an energetic semiconductor bridge (ESCB)-chip initiator with controlled ignition performance. The effects of the Al/MoO3 RMFs with different modulation periods on ignition properties of the ESCB initiator were then systematically investigated in terms of flame duration, maximum flame area, and the reaction ratio of the RMFs. These microchip initiators achieved flame durations of 60-600 µs, maximum flame areas of 2.85-17.61 mm2, and reaction ratios of â¼14-100% (discharged with 47 µF/30 V) by simply changing the modulation periods of the Al/MoO3 RMFs. This behavior was also consistent with a one-dimensional diffusion reaction model. The microchip initiator exhibited a high level of integration and proved to have tuned ignition performance, which can potentially be used in civilian and military applications.
Mn2O3 has been selected to realize nanothermite membrane for the first time in the literature. Mn2O3/Al nanothermite has been synthesized by magnetron sputtering a layer of Al film onto three-dimensionally ordered macroporous (3DOM) Mn2O3 skeleton. The energy release is significantly enhanced owing to the unusual 3DOM structure, which ensures Al and Mn2O3 to integrate compactly in nanoscale and greatly increase effective contact area. The morphology and DSC curve of the nanothermite membrane have been investigated at various aluminizing times. At the optimized aluminizing time of 30 min, energy release reaches a maximum of 2.09 kJâg(-1), where the Al layer thickness plays a decisive role in the total energy release. This method possesses advantages of high compatibility with MEMS and can be applied to other nanothermite systems easily, which will make great contribution to little-known nanothermite research.
To analysis and separate glycoproteins, a simple strategy to prepare regenerated bacterial cellulose (RBC) column with concanavalin A (Con A) lectin immobilized in microfluidic system was applied. RBC was filled into microchannel to fabricate RBC microcolumn after bacterial cellulose dissolved in NaOH-sulfourea water solution. Lectin Con A was covalently connected onto RBC matrix surface via Schiff-base formation. Lysozyme (non-glycoprotein) and transferrin (glycoprotein) were successfully separated based on their different affinities toward the immobilized Con A. Overall, the RBC microfluidic system presents great potential application in affinity chromatography of glycoproteins analysis, and this research represents a significant step to prepare bacterial cellulose (BC) as column packing material in microfluidic system. What is more, troublesome operations for lectin affinity chromatography were simplified by integrating the microfluidic chip onto a HPLC (High Performance Liquid Chromatography) system.
Cellulose/chemistry , Glycoproteins/chemistry , Microfluidics/methods , Chromatography, High Pressure Liquid , Concanavalin A/chemistry , Muramidase/chemistry , Transferrin/chemistry
