Hasil untuk "Explosives and pyrotechnics"

Yao LI, Dongjun ZHANG, Tiezhi SUN et al.

To understand the multiple tail-slapping the trans-media vehicle going through during the high-speed water entry, which may cause damage to the main structure and its accessories. The study was conducted to investigate the load characteristics of the main body of the trans-media vehicle and its accessories in the stages of the generation, development, and collapse of cavities under the condition of inclined water-entering with an attack angle, based on the VOF multiphase flow method. The influence of the water entry inclination angle on the tail-slapping load, cavity collapse load and the trajectory stability are revealed. The results show that the cavity collapse stage is the most dangerous working condition during the water entry process. As the water entry inclination angle increases, the axial and normal forces on the structure increase in the cavitation collapse stage, while the normal overload coefficient approaches a constant. When the inclination angle into the water increased from 60° to 90°, the pitch moment coefficient of the structure increased by 47.1%. A larger inclination angle can reduce the axial and normal loads of the horizontal rudders during the cavity collapse stage, and also improve the trajectory stability of the vehicle. However, it will increase the axial loads of the vertical rudders at the same time. When the cavity wall impacts the tail of the trans-media vehicle during the cavity collapse stage, the three-directional rotation of the body is suppressed, causing it to be in a brief state of rest.

Ruipeng Liu, Linjing Tang, Xianzhen Jia et al.

The Jones-Wilkins-Lee (JWL) equation of state (EOS) is widely used for interpreting the energy release during explosive detonation. Focused on the ideal detonation of high explosives, an artificial neural network (ANN) model was developed in this study for predicting the parameters of JWL EOS. During model establishment, the chemical composition, charge density and enthalpy of formation of high explosives were used as input data. The output results comprised the JWL EOS coefficients. For model training, a dataset of 66 publicly available samples was used, and normalization preprocessing was applied to these data. Using the isentropic expansion curve of detonation products as references, the validation of ANN model was conducted through a comprehensive comparison method incorporating public data, theoretical derivation and model predictions. The results demonstrate that isentropic expansion curves obtained from literature data, theoretical derivation and model prediction exhibit a high degree of coincidence for HMX, LX-19 and PBX9701 high explosives. This agreement is evidenced by discrepancies of error metrics remained below 5%, correlation coefficients exceeding 0.99, similarity index surpassing 0.97 and statistical test hypothesis being satisfied. This ANN model achieves accurate prediction of JWL EOS parameters for ideal detonation. This study can provide a novel approach for predicting JWL EOS parameters of high explosives.

Tianyu LI, Xiaowei FENG, Yaolu LIU et al.

In response to the research demand for the impact resistance of carbon fiber-reinforced polymer (CFRP) laminates commonly used in aircraft, spherical fragment penetration and static blast tests were conducted on T800/3200 CFRP laminates, with CT scanning technology and damage assessment theories employed for further analysis. The damage characteristics and performance of T800/3200 CFRP laminates under two typical loads-fragment penetration and explosive shock waves-were investigated and compared with 2024-T3 aluminum, a material widely used in the aviation manufacturing industry. Two control groups were established: tungsten fragments impacting aerospace aluminum plates and tungsten steel fragments striking CFRP laminates. Impact velocities and residual velocities were precisely measured using high-speed photography. During fragment penetration tests, relationships among incident velocity, residual velocity, and energy absorption were analyzed based on the Recht–Ipson ballistic limit model. The internal damage morphology of CFRP targets was examined in detail using high-resolution CT scanning technology to characterize delamination patterns and progressive failure across different depths and plies. In blast tests, the damage morphology and maximum deflection of target plates were systematically observed and recorded. The blast resistance of CFRP laminates and aluminum plates was quantitatively compared using advanced mathematical methods incorporating boundary condition equivalence and overpressure equivalence principles to ensure a fair and accurate comparison. The results show that, after spherical fragment penetration, the T800/3200 CFRP laminate generates a delamination damage zone resembling a truncated cone, with the volume of the cone decreasing as the penetration velocity of fragments increases. The T800/3200 CFRP laminate exhibits inferior performance against fragment penetration compared with aerospace aluminum but offers significantly enhanced blast resistance. This characteristic makes it more effective in maintaining structural safety and aerodynamic stability during flight missions under explosive threats. The findings provide theoretical and empirical support for improving the safety and reliability of aerospace vehicles through optimized material selection and structural design.

Fateh Chalghoum, Mohammed Jouini, Amir Abdelaziz et al.

In the present work, a study was carried out on the effect of the accelerated aging process on the thermal decomposition of two composite solid propellants based on ammonium perchlorate (AP) and hydroxy‑terminated polybutadiene (HTPB). The first one (CP1) was enriched with aluminum (Al) powders, while the second (CP2) contained a mixture of aluminum and lithium alanate (LiAlH4) as a high-energy fuel additive. The thermal properties of the investigated propellant samples were determined using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The obtained results clearly demonstrated the effect of the aging process on the thermal degradation of the aged samples compared to the unaged ones, by shifting the temperature peaks of their main decomposition step to lower temperatures with a decrease in their DSC heat release. In addition, the residual unburnt propellant was increased, particularly for the complex metal hydride-based propellant. Kinetic modeling of the main thermal degradation phase, applying two advanced isoconversional methods, revealed a significant decrease in activation energy for the aged samples. Furthermore, the three-dimensional diffusion model involved during the investigated decomposition phase of the unaged samples was changed to a random nucleation model after 60 days of aging time.

Zhenggang Li, Xiaoxue Tan, M.A. Yarmolenko et al.

Hydroxyethyl cellulose (HEC) is a multifunctional polymer whose reticular structure and water retention capacity give it a great advantage in medical materials. Beyond biomedical applications, HEC-based coatings share fundamental features with polymeric binders and matrices used in energetic materials, where material stability play a crucial role in performance optimization. In this study, a three-layer composite coating containing hydroxyethyl cellulose, polycaprolactone (PCL), norfloxacin (NFX), and curcumin (CUR) was prepared using low-power electron-beam technology. The molecular structure, chemical composition, and morphology of the film samples were investigated by FTIR, XPS, and SEM. The results show that the materials used have excellent film-forming ability, and the composite layer has a uniform surface with a thickness of up to micrometers. The contact angle test confirmed the film's good hydrophilicity. The release kinetics of norfloxacin (NFX) from the composite layer into the aqueous environment was studied, showing sustained release for over 21 days. This was attributed to the loading of HEC and the fact that the upper layer of the CUR film acted as a sealing layer which helped to achieve a slow release of the drug. The researchers characterized the coatings and observed that the coatings exhibited excellent antibacterial activity against both Escherichia coli and Staphylococcus aureus strains tested, with better antibacterial efficacy against E. coli. The sustained release behavior observed in the composite coatings is analogous to the controlled decomposition and energy release mechanisms in energetic binder systems, where polymeric networks regulate the release of active components. In conclusion, the composite coatings prepared using the low-power electron beam deposition technique not only demonstrate superior antibacterial performance but also highlight potential interdisciplinary applications in the design of polymeric matrices for energetic material formulations.

Dmitry B. Vinogradov, Pavel V. Bulatov, Evgeny Yu. Petrov et al.

A number of functionalized (1-N-alkylnitramino)methoxy‑substituted oxetane derivatives have been synthesized using N-chloromethyl-N-alkylnitramines. The compounds were characterized using 1H,13C and IR spectroscopy as well as elemental analysis of C, H, and N. The thermal behavior of the compounds was analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Based on individual representatives, a number of oligomers were synthesized and described to initially evaluate their potential. The oligomers were extensively characterized and common structural features were elucidated. These can be used to prepare useful energetic binders through cationic ring-opening polymerization.

Salam Mohammed, Edward B. Ogugu, Ramakant Sharma et al.

This work investigates the molecular-level interactions of a fluorescent microporous polymer (PIM-1) with nitroaromatic explosives, in the context of thin film explosive sensors. Thin films of the PIM-1 were exposed to 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), and their steady-state absorption and emission spectra measured. For comparison, the response of PIM-1 to non-explosive molecules such as benzene (BN) was also explored. Complementary electronic-structure calculations were used to predict absorption and emission spectra and to determine binding energies for the PIM-1-analyte complexes. The calculations agree well with experiment and reveal that association of nitroaromatic analyte molecules with PIM-1 alters the energy levels and the arrangements of frontier orbitals, indicating significant molecular interactions. Calculations show that the electronic properties and photo-excited electron transfer can be described by interaction with a single repeat unit of the polymer. The molecular binding, however, involves interaction with at least three repeat units, with the DNT or TNT molecule binding into a pocket in the contorted structure of the microporous polymer. Together, the experimental and theoretical results demonstrate that PIM-1 is a promising platform for selective nitroaromatic detection and provide molecular design principles that could improve sensitivity and selectivity in future sensor materials.

Houpeng Zhang, Zhen Lu, Tianyou Wang et al.

The micro-explosion of emulsion droplets plays an important role in promoting atomization, improving combustion efficiency, and reducing pollutant emissions. In this experimental study of the micro-explosion of emulsion droplets, we find that mist can be generated during the heating of emulsion droplets, and the mist generation is closely related to the micro-explosion process. Combined analysis from high-speed images, gas chromatography, and droplet temperature variation shows that the mist generation is due to the condensation of vapor into small droplets as the temperature decreases. Two micro-explosion modes are observed, intense micro-explosion with a large amount of mist and weak micro-explosion with a small amount of mist. Different emulsified fuels are tested, and mist can be produced for all the emulsified fuels. The mist is quantitatively analyzed via digital image processing. According to the mist concentration curve in the micro-explosion process, the micro-explosion mode can be distinguished. The effects of the water and surfactant contents in the emulsion droplets are studied, and the mists are used to characterize the micro-explosion. Increasing the water content can promote the vaporization of the water phase, increase the strength of micro-explosion, and result in a large amount of mist. Increasing the surfactant content can improve the stability of the emulsion droplet, reduce the probability of intense micro-explosion, and hence reduce the mist concentration.

Qing-Xia Li, Er-Hai An, Qing-Feng Qin et al.

In this paper, we investigated the potential use of a new organic-inorganic hybrid crystal structure based on KNO3 in ignition compositions. H2dabco[K(NO3)3] (DAN-2) with organic-inorganic hybrid crystal structure is synthesized through intermolecular assembly technology. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to detect the crystal morphology, structure and molecular structure of DAN-2, which has a regular cubic structure. Experimental data were obtained using thermogravimetric/differential scanning calorimetry (TG-DSC), closed bomb test and high-speed photography, which were then used to study and analyze the thermal decomposition properties and combustion properties of DAN-2. The initial thermal decomposition temperature of DAN-2 was low (194 °C) and the activation energy of the thermal decomposition was 154 kJ/mol. Possible thermal decomposition mechanisms are further discussed and proposed. This research pushed forward the application of organic-inorganic hybrid crystal structure oxidant DAN-2 in ignition system.

Li Yu, Yupeng Hu, Guangmei Shi et al.

Solid propellant fires, characterized by uncontrolled combustion behaviors, are a common occurrence in industries that utilize solid propellants and can lead to significant consequences. However, there has been a lack of comprehensive studies on modeling and simulating the flame characteristics of NEPE solid propellant fires. This research aims to investigate the flame behaviors of large NEPE solid propellants at different altitudes using computational fluid dynamics (CFD). The flame's shape and temperature were examined based on experimental data under atmospheric conditions to validate the numerical model. The findings reveal that the simulated flame temperature slightly surpasses the experimental values, while the simulated flame length and width align well with the experimental measurements. Morewover, increasing altitudes result in shorter flame lengths and lower combustion temperatures. Furthermore, the study scrutinizes the influence of turbulence models on the flame behavior of NEPE propellant fires.

Luca Boccioli, Mariam Gogilashvili, Jeremiah Murphy et al.

The explosion mechanism of a core-collapse supernova is a complex interplay between neutrino heating and cooling (including the effects of neutrino-driven convection), the gravitational potential, and the ram pressure of the infalling material. To analyze the post-bounce phase of a supernova, one can use the generalized Force Explosion Condition (FEC+), which succinctly formalizes the interplay among these four phenomena in an analytical condition, consistent with realistic simulations. In this paper, we use the FEC+ to study the post-bounce phase of 341 spherically symmetric simulations, where convection is included through a time-dependent mixing length approach. We find that the accretion of the Si/O interface through the expanding shock can significantly change the outcome of the supernova by driving the FEC+ above the explosion threshold. We systematically explore this by (i) artificially smoothing the pre-supernova density profile, and (ii) artificially varying the mixing length. In both cases, we find that large-enough density contrasts at the Si/O interface lead to successful shock revival only if the FEC+ is already close to the explosion threshold. Furthermore, we find that the accretion of the Si/O interface has a substantial effect on the critical condition for supernova explosions, contributing between 5\% and 15\%, depending on how pronounced the density contrast at the interface is. Earlier studies showed that convection affects the critical condition by 25--30\%, which demonstrates that the accretion of the Si/O interface through the shock can play a nearly comparable role in influencing shock dynamics.

Natalie Smith, Meagan R Phister, Ashley M. Conley et al.

The development of high performing and stable energetic materials (EMs) is a focus for a variety of applications including explosives, propellants, and pyrotechnics. To enhance stability, energetic crystals are often...

Jared Estevanes, P. Buzzini, Geraldine Monjardez

This study aimed to evaluate the advantages and challenges of analyzing post-blast pyrotechnic pipe bombs using a combination of light microscopy and micro-Raman spectroscopy. Two simulated improvised explosive devices (IEDs) were constructed and exploded using pyrotechnics as the main charge and consisted of several different components to simulate common materials that might be found in authentic bombing scenarios. In order to develop a rapid explosives residue recovery technique, a wet and dry swabbing process was compared to determine the most efficient swabbing method of recovery for inorganic oxidizers in post-blast debris. Samples were recrystallized using a water recrystallization method followed by in situ analysis using polarized light microscopy (PLM) and micro-Raman spectroscopy, targeting euhedral and subhedral crystals. While the water recrystallization had effects on the resulting Raman spectrum, such as peak intensity reduction, ultimately, the final salt identifications were not affected. The detection of several inorganic oxidizers post-blast included the identification of potassium perchlorate (KClO4), potassium nitrate (KNO3), and barium nitrate (Ba(NO3)2). The detection of KNO3 using microscopy alone was more challenging due to its relatively low abundance compared to KClO4 but was achieved with micro-Raman spectroscopy. Additionally, the mixing of inorganic oxidizers within single crystals was also observed. The results indicated that the combined approach of microscopy and micro-Raman spectroscopy enabled the successful detection of inorganic oxidizing salts in a post-blast scenario, as well as describing the advantages and limitations of this combination of techniques.

M. Tagawa, R. Matyáš, J. Kucera et al.

Abstract   Potassium chlorate has long been utilized as an excellent oxidizing agent in pyrotechnics and explosives. As mixtures of potassium chlorate and any type of combustible material can be explosive, there is a potential risk of misuse in homemade explosives. Unlike commercial explosives, homemade chlorate and oil mixtures do not have a constant composition, which limits their understanding. This study reports the effects of two types of oil (motor oil and cooking oil) and their ratios (ranging from 2.5% to 40.0% (w/w)) on the explosive properties of such mixtures. The impact sensitivity was highest at a motor oil ratio of 5%. The friction sensitivity increased with an increasing oil ratio, reaching a maximum at an oil ratio of ~22.5%, and was close to those of primary explosives. The motor oil mixtures exhibited higher sensitivity than the cooking oil mixtures at oil ratios of 25.0% or less. A 10% oil mixture, which was close to the ratio of oxygen balance equal to zero, detonated in weak confinement, such as a paper cylinder. The highest detonation velocities in a polypropylene tube were ~2 300 and 2 550 m/s at a 10% ratio of motor oil and cooking oil, respectively. The velocities of the metal case wall, measured by photonic Doppler velocimetry, reached ~1 100 m/s near the end of acceleration. These results show that homemade chlorate and oil mixtures are capable of detonation and quite sensitive over a wide range of oil ratios, with sufficient power to cause damage in the vicinity. Key points Simple mixtures of potassium chlorate and oil can be used as a homemade explosives. Oil types and ratios considerably affect the sensitivity and detonation velocity. Mixtures are sufficiently potent to generate hazardous fragments. Long-term storage causes an internal oil gradient. Mixtures with wide-ranging oil ratios can have highly sensitive points.

Sehyun Chun, Sidhartha Sankar Roy, Y. Nguyen et al.

The sensitivity of heterogeneous energetic (HE) materials (propellants, explosives, and pyrotechnics) is critically dependent on their microstructure. Initiation of chemical reactions occurs at hot spots due to energy localization at sites of porosities and other defects. Emerging multi-scale predictive models of HE response to loads account for the physics at the meso-scale, i.e. at the scale of statistically representative clusters of particles and other features in the microstructure. Meso-scale physics is infused in machine-learned closure models informed by resolved meso-scale simulations. Since microstructures are stochastic, ensembles of meso-scale simulations are required to quantify hot spot ignition and growth and to develop models for microstructure-dependent energy deposition rates. We propose utilizing generative adversarial networks (GAN) to spawn ensembles of synthetic heterogeneous energetic material microstructures. The method generates qualitatively and quantitatively realistic microstructures by learning from images of HE microstructures. We show that the proposed GAN method also permits the generation of new morphologies, where the porosity distribution can be controlled and spatially manipulated. Such control paves the way for the design of novel microstructures to engineer HE materials for targeted performance in a materials-by-design framework.

Brandon Wagner, Minseok Kim, M.W. Chowdhury et al.

The hydrogenation of metal nanoparticles provides a pathway toward tuning their combustion characteristics. Metal hydrides have been employed as solid-fuel additives for rocket propellants, pyrotechnics, and explosives. Gas generation during combustion is beneficial to prevent aggregation and sintering of particles, enabling a more complete fuel utilization. Here, we discuss a novel approach for the synthesis of magnesium hydride nanoparticles based on a two-step aerosol process. Mg particles are first nucleated and grown via thermal evaporation, followed immediately by in-flight exposure to a hydrogen-rich low-temperature plasma. During the second step, atomic hydrogen generated by the plasma rapidly diffuses into the Mg lattice, forming particles with a significant fraction of MgH2. We find that hydrogenated Mg nanoparticles have an ignition temperature that is reduced by ∼200 °C when combusted with potassium perchlorate as an oxidizer, compared to the non-hydrogenated Mg material. This is due to the release of hydrogen from the fuel, jumpstarting its combustion. In addition, characterization of the plasma processes suggests that a careful balance between the dissociation of molecular hydrogen and heating of the nanoparticles must be achieved to avoid hydrogen desorption during production and achieve a significant degree of hydrogenation.

Song Zhang, Lewu Zhan, Yifan Zhang et al.

Recently, microfluidic technology has been widely applied to the preparation of nano-energetic materials. The mixing efficiency of fluid is one of the significant factors which could affect the particle size and particle size distribution (PSD) of products. In this report, a novel strategy to enhance the mixing performance of fluid is developed by combining continuous flow microfluidic and resonant acoustic mixing (RAM) technologies. The results of the fluid visualization and 3D-Computational fluid dynamics (CFD) simulation showed that the new continuous flow resonance acoustic mixing (CFRAM) technology has better mixing efficiency than the traditional microfluidic approach. To demonstrate the utility of this CFRAM technology, it was implemented in the continuous preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) nanoparticles. Compared with previous reported results, nano TATB prepared by CFRAM technology has a smaller average particle size (D50 = 50.8 nm) and a narrower particle size distribution (D10 = 33.0 nm; D90 = 69.6 nm). The XRD spectrum shows that the crystal structure of nano TATB has not changed. DSC test results show that the apparent activation energy of nano TATB is 177.8 kJ/mol, which is 6.5 kJ/mol lower than the raw TATB, and has good thermal stability. We expect that this strategy may open a new avenue for the efficient preparation of nano energetic materials with narrow PSD.

Yash Pal, Sri Nithya Mahottamananda, Subha S et al.

In recent years, significant developments have been made in solid-fuel combustion. Paraffin-based fuels could be a potential solid fuel for hybrid and ramjet applications due to their high regression rate, low cost, and minimal environmental impact. This study examines the thermal and combustion performance of paraffin-based fuels loaded with CeO2 combustion catalysts and Al additive. A typical melt-cast technique was used to prepare three different fuel formulations, which are paraffin/10 wt.% of Al (S2), paraffin/10 wt.% of CeO2 (S3), and CeO2-Al (10:10 wt.%) binary composite (S4). The pure paraffin (S1) fuel was manufactured as a reference formulation. The CeO2-Al binary composite powder was prepared by ball-milling of CeO2 and Al powders. The CeO2 and Al nanoparticles were characterized by X-ray diffraction (XRD), particle size distribution (PSD), and scanning electron microscope (SEM). The PSD study revealed that the majority of CeO2, Al, and CeO2-Al binary composite particles are 29 nm, 34 nm, and 26 nm in size, respectively. The thermogravimetric analysis (TGA) was used to investigate the effect of CeO2 and Al on the thermal decomposition of paraffin. The results indicate that the paraffin decomposes faster and at a higher rate when CeO2 and CeO2-Al binary composite additives were added. The activation energy of paraffin-based fuel (S4) was reduced from 254 kJ/mol to 214 kJ/mol when a CeO2-Al combustion catalyst was added. The lab-scale ballistic tests showed that the average regression rate of paraffin-Al (S2) and paraffin-CeO2(S3) samples increased in the range of 1.1-1.4 mm/s and 1.12-1.38 mm/s, respectively, whereas, with the CeO2-Al binary composite (S4) sample, a reasonable improvement of 1.15 mm/s to 1.49 mm/s was reported.

Manuel Miranda, Mattia Frasca, Ernesto Estrada

Nowadays, explosive synchronization is a well documented phenomenon occurring in networks when the node frequency and its degree are correlated. This first-order transition, which may coexists with classical synchronization, has been recently causally linked to some pathological brain states like epilepsy and fibromyalgia. It is then intriguing how most of neuronal systems can operate in normal conditions avoiding explosive synchronization. Here, we have discovered that synchronization in networks where the oscillators are coupled via degree-biased Laplacian operators, naturally controls the transition from explosive to standard synchronization in neuronal-like systems. We prove analytically that explosive synchronization emerges when using this theoretical setting in star-like (neuronal) networks. As soon as this star-like network is topologically converted to a network containing cycles, e.g., via synaptic connections to other neurons, the explosive synchronization gives rise to classical synchronization. This allows us to hypothesize that such topological control of explosive synchronization could be a mechanism for the brain to naturally work in normal, non-pathological, conditions.

Mariam Gogilashvili, Jeremiah W. Murphy, Evan P. O'Connor

One of the major challenges in Core-collapse Supernova (CCSN) theory is to predict which stars explode and which collapse to black holes. Gogilashvili and Murphy (2022) derived an analytic force explosion condition (FEC) and showed that the FEC is consistent with CCSN simulations that use the light-bulb approximation for neutrino heating and cooling. In this follow-up manuscript, we show that the FEC is consistent with the explosion condition when using actual neutrino transport in GR1D simulations (O'CONNOR 2015). Since most 1D simulations do not explode, to facilitate this test, we enhance the heating efficiency within the gain region. To compare the analytic FEC and radiation-hydrodynamic simulations, this manuscript also presents a practical translation of the physical parameters. For example: we replace the neutrino power deposited in the gain region, $L_ντ_g$, with the net neutrino heating in the gain region; rather than assuming that $\dot{M}$ is the same everywhere, we calculate $\dot{M}$ within the gain region; and we use the neutrino opacity at the gain radius. With small, yet practical modifications, we show that the FEC predicts the explosion conditions in spherically symmetric CCSN simulations that use neutrino transport.