Hasil untuk "Explosives and pyrotechnics"

Qifu ZENG, Erdi ABI, Mingwei LIU et al.

Supercritical CO2 phase transition rock-breaking is a dynamic destruction process under the combined action of shock waves and high-pressure gas. To deeply investigate the rock-breaking mechanisms of supercritical CO2 phase transition under multi-hole synchronous initiation and in-situ stress coupling conditions, targeting the actual working conditions of CO2 field rock-breaking, the initial rock-breaking pressure of a single hole was analyzed based on the thin-walled cylinder theory. A predictive model for the joint rock-breaking radius of multi-hole shock waves and high-pressure gas under in-situ stress was developed by integrating the one-dimensional detonation gas expansion theory. Field experiments on multi-hole CO2 phase transition rock-breaking were subsequently conducted for comparative validation. The results show that when the fracturing pipe is buried shallowly, the influence of in-situ stress on the stress distribution of the rock mass is relatively weak. When the pressure of a single hole is consistent, the more fracturing holes there are, the greater the superposed peak stress of each hole. In the direction perpendicular to the layout of the test hole, the peak stress of each hole shows a U-shaped parabolic distribution. The superposed stress of the fracturing holes at both ends is the largest. In the direction parallel to the layout of the test hole, the peak stress of each hole shows an inverted U-shaped parabolic distribution, and the superposed stress of the middle fracturing hole is the largest. In addition, the rock mass damage and fracture range under multi-pore impact obtained by acoustic wave testing in the field is in the shape of a three-dimensional funnel. The vertical damage and fracture range is between 5.05 and 5.73 m, and the planar damage and fracture range is between 4.3 and 5.6 m. The error between the measured value of the planar damage and fracture range and the theoretically calculated value is between 5.0% and 18.7%. The calculation error mainly comes from the uneven superposition stress of each fracturing hole. Further analysis shows that the radius of supercritical CO2 phase transition rock-breaking increases semi-parabolically with the superposed stress of the fracturing hole and increases logarithmically with the depth of the fracturing hole. As the compressive strength of the rock mass increases, the rock fracture toughness increases nearly linearly, and the corresponding rock-breaking radius decreases nearly linearly. The research results can provide a quantitative design basis for optimizing engineering parameters in the multi-pore supercritical CO2 phase transition for rock-breaking.

Tianzhao WANG, Yuanxiang SUN, Yanwu CHEN

Contact explosion is an important condition in the damage and protection of underwater structures, and the pulsating bubbles generated by explosive underwater explosion are an important damage source. The current research on underwater explosion bubbles mainly focuses on the pulsating characteristics of spherical bubbles under free-field and typical boundary conditions, while there is a notable lack of research on non-spherical bubbles under contact explosion conditions. The pulsation characteristics of underwater contact explosion bubbles were systematically investigated through theoretical modeling, numerical simulations, and experiments. To address the theoretical gap in contact explosion dynamics, a hemispherical bubble dynamics model under rigid wall contact conditions was established based on incompressible and inviscid fluid assumptions. By comparing present model with the spherical bubble pulsation model in an incompressible flow field, quantitative relationships between parameters such as the maximum bubble radius, initial radius, pulsation period were obtained. Theoretical analysis reveals that the maximum radius, initial radius, and pulsation period of contact explosion bubbles are 1.26 times (theoretical scaling factor) those of free-field conditions. An error analysis was conducted to account for factors such as fluid compressibility, unstable bubble deformation, and energy dissipation induced by bubble-rigid wall interactions. Numerical simulations using LS-DYNA for underwater explosions with 0.300 g, 0.233 g, and 5.000 g TNT charges under varying water depths reveal that the scaling factors for maximum radius and pulsation period under contact explosion conditions range from 1.22 to 1.24 and 1.20 to 1.21 times those of free-field results, respectively, with simulation errors below 5% compared to theoretical predictions. Experimental validation in a water tank shows that the maximum radius and period of contact explosion bubbles are 1.10 and 1.06 times those of free-field conditions. During the experiments, plate vibrations were observed upon explosion, which significantly contributed to experimental errors. This work addresses the theoretical gap in contact explosion bubble dynamics, enhances the understanding of boundary effects in underwater explosion phenomena.

Junrun LI, Yonggang LU, Xiaowei FENG et al.

In a reinforced concrete (RC) box structure, the dissipation of blast waves is restricted, and damage to the structure can be intensified due to multiple reflections. To thoroughly investigate the load characteristics and dynamic behavior of internal explosions in an RC box structure, the applicability of the finite element method was verified by replicating internal explosion tests on fully enclosed and semi-enclosed (with venting openings) RC box structures. Based on this, numerical simulations of internal explosions were conducted for the prototypical RC box structure and the type of terrorist bombing attacks specified by the Federal Emergency Management Agency under three explosion scenarios and four venting areas. The influence of venting area on the load characteristics at the inner surfaces and corners, the load distribution on the inner surfaces, and the time histories of displacement and velocity at the centers of the inner surfaces under internal explosion loads were explored. Additionally, a formula for calculating the total impulse of the structure’s inner surface was proposed, considering both the venting area and the spatial distribution of the impulse. The results show that the venting area has a negligible effect on the overpressure, while the impulse decreases exponentially with increasing venting area. The load distribution characteristics on the structure’s inner surface are significantly influenced by the structural dimensions, exhibiting an indented or W pattern. The maximum displacement at the centers of walls and slabs is reduced by about 50% as the venting coefficient changes from 0.457 to 1.220. Finally, based on the total impulse and maximum displacement response of each component under free-field explosion loads, a calculation method for the impulse and damage enhancement coefficient was proposed based on the venting area, effectively predicting the internal explosion load and the structure’s dynamic behavior at various venting coefficients.

Amar Aryan, Erin Higgins, Matt Nicholl et al.

Supernova (SN) 2024ggi is a nearby Type II SN discovered by ATLAS, showing early flash-ionization features. The pre-explosion images reveal a red supergiant (RSG) progenitor with an initial mass of 10-17 M$_\odot$. In the present work, we perform detailed hydrodynamic modeling to refine and put robust constraints on the progenitor and explosion parameters of SN 2024ggi. Among the progenitor models in our study, the pre-SN properties of the 11 M$_{\odot}$ match the pre-explosion detected progenitor well. However, we find it difficult to completely rule out the 10 M$_{\odot}$ and 12 M$_{\odot}$ models. Thus, we provide a constraint of 11$^{+1}_{-1}$ M$_{\odot}$ on the initial mass of the progenitor. To match the observed bolometric light curve and velocity evolution of SN 2024ggi, the favored model with an initial mass of 11 M$_{\odot}$ has a pre-SN radius of 800 R$_{\odot}$. This model requires an explosion energy of [0.7-0.8]$\times$10$^{51}$ erg, nickel mass of 0.049 M$_{\odot}$, ejecta mass of 9.1 M$_{\odot}$, and an amount of $\sim$ 0.5 M$_{\odot}$ of steady-wind CSM extended up to $\sim1.2\times10^{14}$ cm resulting from an eruptive mass-loss rate of 1.0 M$_{\odot}$ yr$^{-1}$. We also incorporate the accelerated-wind CSM scenario, which suggests a mass-loss rate of 1.0$\times10^{-2}$ M$_{\odot}$ yr$^{-1}$ and a CSM mass of $\sim$ 0.7 M$_{\odot}$ extended up to $\sim1.1\times10^{14}$ cm. This mass-loss rate falls within the range constrained observationally. Additionally, due to the constraint of 11$^{+1}_{-1}$ M$_{\odot}$ on the initial mass, the range of pre-SN radius and ejecta mass would be [690-900] R$_{\odot}$, and [8.2-9.6] M$_{\odot}$, respectively.

Liliya Imasheva, H. -Thomas Janka, Achim Weiss

Despite the three-dimensional nature of core-collapse supernovae (CCSNe), simulations in spherical symmetry (1D) play an important role to study large model sets for the progenitor-remnant connection, explosion properties, remnant masses, and CCSN nucleosynthesis. To trigger explosions in 1D, various numerical recipes have been applied, mostly with gross simplifications of the complex microphysics governing stellar core collapse, the formation of the compact remnant, and the mechanism of the explosion. Here we investigate the two most popular treatments, piston-driven and thermal-bomb explosions, in comparison to 1D explosions powered by a parametric neutrino engine in the P-HOTB code. For this comparison we calculate CCSNe for eight stars and evolution times up to 10,000 s, targeting the same progenitor-specific explosion energies as obtained by the neutrino-engine results. Otherwise we employ widely-used ("classic") modelling assumptions, and alternatively to the standard contraction-expansion trajectory for pistons, we also test suitably selected Lagrangian mass shells adopted from the neutrino-driven explosions as "special trajectories." Although the 56Ni production agrees within roughly a factor of two between the different explosion triggers, neither piston nor thermal bombs can reproduce the correlation of 56Ni yields and explosion energies found in neutrino-driven explosions. This shortcoming as well as the problem of massive fallback witnessed in classical piston models, which diminishes or extinguishes the ejected nickel, can be largely cured by the special trajectories. These and the choice of the explosion energies, however, make the modelling dependent on pre-existing neutrino-driven explosion results.

Gerold Alsmeyer, Konrad Kolesko, Matthias Meiners et al.

We study the phenomenon of explosion in general (Crump-Mode-Jagers) branching processes, which refers to the event where an infinite number of individuals are born in finite time. In a critical setting where the expected number of immediate offspring per individual is exactly one, whether or not explosion occurs depends on the fine properties of the reproduction point process. We provide two sufficient conditions for explosion in these CMJ processes. The first uses a comparison with Galton-Watson processes in varying environments, while the second relies on a comparison with Bellman-Harris branching processes. Our main result is an equivalent characterization of explosion, expressed as an integral test, in the case where the reproduction point process is Poisson. For the derivation, we also study the fixed-point equation associated with a smoothing transform, which is known to describe the distribution of the explosion time. We use multiplicative martingales to show that this distribution is an attractive fixed point of the smoothing transform, which in particular implies its uniqueness modulo an additive shift.

Runzhi LI, Mingshuai LIU, Zichao HUANG et al.

In order to ensure the safe transportation and storage of highly flammable and combustible gases, it is essential to implement effective prevention and control measures. Explosion venting is an effective way to prevent and control its explosion hazards. In order to improve the efficiency and safety of explosion venting means and to promote the further study of secondary explosion in the external flow field of explosion venting, the research status of combustible gas explosion and explosion venting at home and abroad is analyzed, and meanwhile, the theory and achievements of combustible gas explosion venting in recent 20 years are summarized. Existing researches have shown that the explosion characteristics of combustible gases has been studied systematically, providing underpinning data for the study of combustible gas venting characteristics. A comprehensive examination of the explosion parameters and flame development alterations was performed in the internal and external flow fields resulting from deflagration. The hazard of deflagration was found to be exacerbated by the coupling between pressure waves and flame waves in the internal and external flow fields. The effectiveness of deflagration was evaluated based on the results of the study. It is difficult to define the initiation of the secondary explosion because the secondary explosion in the vent outflow field is limited by the poorly recognized evolutionary mechanism of blast-flame coupling. A preliminary study of the effect of the secondary explosion on the variation of the deflagration parameters has been carried out. In the explosion venting research, it is still necessary to narrow the span of influencing factors in the experimental aspect and improve the explosion venting equipment. In the numerical simulation research, it is necessary to carry out the study of complex models, the prediction of explosion venting hazards and the evaluation of the effect of explosion venting, which still need a lot of data and good models. Accordingly, the safe transportation and storage of flammable gases can be realized and the applications of flammable gases can be broadened.

Yi Wang, Huifang Ren, Xiaolan Song et al.

Aluminum (Al) is often used as a metal fuel in solid propellants, whereas Co, Fe and Ni are used as combustion rate catalysts in solid propellants. However, owing to the oxide layer on the surface of Al powder, which hinders its energy release, and Co, Fe, and Ni, the nanometal particle catalysts are prone to agglomeration because of their high surface energy and magnetic properties. Therefore, in this study, a new composite material [Ternary]/µAl was formed by coating Al particles with Co, Fe and Ni by a displacement reaction. On the one hand, the nanoparticle interfacial layer reduces agglomeration between Al particles, and on the other hand, the nanoparticle interfacial layer facilitates oxygen transport through the established oxygen transport channels. As a result, [Ternary]/µAl has superior heat release and catalytic properties. The experimental results showed that [Ternary]/µAl, as a novel catalytic material, significantly reduced the main thermal decomposition temperature of the binary oxidant AN/NP-1, with an activation energy required for the reaction of 120.1 kJ/mol, and led to intense combustion, resulting in a combustion pressure of 1.29 MPa and a combustion rate of 2.86 MPa/s, releasing more combustion heat than the sample. The theoretical calculation results show that the propulsion efficiency of [Ternary]/µAl + AN/NP-1 is relatively high, and the proportion of the main thrust sources H2 and CO is increased to 67.8%. Based on the results of the thermal analyses and combustion tests, a possible combustion mechanism for [Ternary]/µAl + AN/NP-1 composites was proposed. In conclusion, improving the overall performance of metal fuel/oxidizer composites by the formation of interfacial layers through substitution reactions is expected to have wider applications in solid propellants.

Min LI, Huahua XIAO

Study on gas deflagration-to-detonation transition (DDT) is of great significance for the research and development of industrial explosion prevention and detonation propulsion technology. Staggered array of obstacles is a typical obstacle layout that may be involved in the gas ignition and explosion scenario. Its existence usually significantly promotes the occurrence of DDT. In view of the lack of understanding of DDT in staggered array of obstacles, high-precision algorithm and dynamic adaptive grid were applied to solve the two-dimensional, fully compressible reactivity Navier-Stokes equations coupled with a calibrated chemical-diffusive model. Numerical investigation on the initiation process of DDT of premixed hydrogen and air in staggered array of square obstacles under different obstacle spacings was carried out. The results showed that decreasing obstacle spacing is beneficial to increase flame surface area in the early stage of flame acceleration and enhance compression of unburned gas by shock wave in the later stage, thus shortening DDT run-up time and distance. However, when the obstacle spacing is reduced to a threshold value, stuttering detonation occurs and the DDT run-up distance increases. The occurrence of DDT is mainly caused by the interaction between the flame and the shock wave reflected from the front wall of obstacle. The detonation partially decouples when it diffracts around an obstacle. Detonation re-initiation may be triggered when the decoupled detonation collides with a wall or with the shock wave or failure detonation wave from the other side of the obstacle. If the obstacle spacing is too small, the shock wave intensity decays significantly during detonation decoupling. This can easily lead to detonation failure. In addition, shock waves can be reflected off the staggered array of square obstacles in the vertical and parallel directions to the flame propagation direction, which help shock waves to act on the flame and unburned gas mixture. Therefore, DDT is more likely to be initiated in the staggered array of square obstacles than that of circular obstacles.

Shanyu XIAO, Xiaowang SUN, Weiwei QIN et al.

In order to address the needs of modern combat vehicles for both personnel protection and lightweight design, optimizing their blast-resistant structures is necessary. Due to the high cost of physical experiments, finite element simulation has been commonly used instead. However, simulations of explosion and vehicle responses require extensive computational resources and incur high computational costs, leading to limited data availability for the optimization of explosion-proof structures. Since structural optimization demands sufficient data support, larger amount of valid data can improve the accuracy of the surrogate model and the precision of the optimal solution, yielding better optimization results. To overcome these challenges, a data-driven optimization method for vehicle’s explosion-proof structures was proposed, integrating data augmentation and semi-supervised regression. To address the limitations of generative adversarial networks (GANs) in handling numerical data, an improved model, a Gaussian density estimation-Wasserstein generative adversarial network (GDE-WGAN), was developed by modifying both the generator and discriminator of the WGAN model, a variant of the GANs. The feasibility of the proposed method was demonstrated based on the principle of information gain. The data generated by the GDE-WGAN were incorporated into a self-training framework, where an adaptive confidence assessment mechanism dynamically adjusted the way that the semi-supervised support vector regression model utilizes the generated data. The feasibility and superiority of the method were validated by comparing the enhanced performance of the semi-supervised regression model using different numerical data expansion techniques. Finally, multi-objective optimization was performed to obtain the optimal solutions of the data-augmented semi-supervised regression model and the initial model, followed by verification and comparison with finite element simulation results. It shows that the GDE-WGAN significantly enhances the performance of the semi-supervised regression model, and the generated data exhibit greater randomness and diversity through the network structure of the GANs, which benefits semi-supervised learning. When handling semi-supervised regression for high-dimensional nonlinear numerical data, both global and local data distribution similarities play a crucial role. Furthermore, finite element simulations indicate that the improved model predicts results more accurately than the initial model and achieves superior optimization outcomes.

Qiushi HU, Yang HE, Suyang ZHONG et al.

Modeling powder is used to simulate the highly fragmented state of pressed explosives resulting from collisions, and the gap extrusion ignition behavior of PBX modeling powder is studied. Experiments were designed based on the way of projectile impact method. To ensure that no flow space exists except the designed gap, the surface of the sample was covered with cushion and coated with grease for sealing. The movement and reaction of molding powder squeezing into the gap were recorded by high-speed photography. By changing the ratio of gap area to sample cross-sectional area, the influence of compaction on ignition was studied. The results show that in the absence of grease seal, PBX molding powder undergoes particle crushing and compaction, and then the compacted molding powder is extruded from the clearance near the cushion, and ignition occurs in the extrusion process. The ignition position is at the interface between explosive and cushion. In the case of grease seal, PBX molding powder does not ignite for a period of time after compaction. When the indenter moves halfway, a wedge-shaped slip zone is formed, and a slip-dead zone interface could be seen in high-speed camera photos. Then the deformation mode evolves from single-wedge slip zone to double-wedge slip zone, and the shear effect of slip-dead zone interface does not cause ignition. At the later stage of loading, the indenter travels close to the gap surface, and the wedge-shaped slip zone disappears. Before and after the collision between the indenter and the gap, the explosive ignites once in each instance. Compaction effect has an important influence on ignition behavior. After compaction, the threshold value of ignition speed is obviously reduced, with the impact speed required to cause ignition being merely 4.5 m/s.

Nassima Sahnoun, Amir Abdelaziz, Memdouh Chebbah et al.

Double-base energetic composites have garnered substantial attention, particularly in aerospace, rocket, and missile applications. This class of materials offers diverse burning rates, high specific impulses, exceptional operational performance, and robust mechanical properties. In this study, we present a novel energetic composite produced by integrating ammonium perchlorate (AP) into a double-base energetic matrix composed of potato nitrostarch (NPS) and diethylene glycol dinitrate (DEGDN). The optimal composition of AP@NPS-DEGDN was determined through theoretical performance calculations using CEA-NASA program. The structural and morphological properties of the obtained composite were analyzed using FTIR and SEM techniques. The results indicated that the addition of AP did not modify the chemical structure of the baseline composite NPS-DEGDN. The thermal analysis by TGA revealed that the incorporation of 50 wt.% of AP enhanced the decomposition of the NPS-DEGDN matrix, while the NPS-DEGDN matrix simultaneously promoted the decomposition of AP. The DSC results indicated that the decomposition peak temperatures of the AP@NPS-DEGDN composite shifted to lower values, compared to the NPS-DEGDN matrix, highlighting the synergistic catalytic effect between the ingredients with an increase in heat release during the decomposition. Finally, the impact of various compounds on the thermal decomposition kinetics of AP@NPS-DEGDN was investigated using advanced model-free kinetic approaches, which revealed a significant reduction in the activation energy barrier, confirming the pronounced catalytic effect across the different decomposition stages of AP@NPS-DEGDN. These findings underscore the potential of the developed AP@NPS-DEGDN composite as a promising candidate for advanced energetic applications.

Vladica S Bozic

Composite propellants are widely used in applications ranging from gas generators and small rockets to large rocket systems in space programs. This study presents a novel thermoplastic elastomer (TPE) binder system based on oxygen-enriched polyether-block-amide (PEBA) copolymer, designed to enhance the performance of composite propellants while reducing waste and environmental impact. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) were used to characterize the TPE binder, revealing favorable thermal and structural properties. The burning rate of propellants incorporating this binder was evaluated using ammonium perchlorate (AP) oxidizer of varying particle sizes and aluminum (Al), with and without the addition of lithium fluoride as a burning-rate modifier. Results demonstrate that the oxidizer particle size significantly affects the burning rate, and lithium fluoride effectively reduces it, depending on its concentration in the propellant formulation. Compared to traditional hydroxyl‑terminated polybutadiene (HTPB)-based systems, propellants formulated with the PEBA-based binder exhibit improved energy performance, comparable burning rates, and advantageous processing and aging characteristics, all at a reduced cost.

Sri Nithya Mahottamananda, Yash Pal, Narendra Yadav et al.

The performance of hybrid rocket propulsion systems can be significantly enhanced by incorporating metal additives in solid fuels. This study investigates the ignition, combustion, and regression rate of hydroxyl‑terminated polybutadiene (HTPB)-based solid fuels supplemented with Boron (B) and Viton. The investigated fuel compositions comprise pure HTPB, HTPB with 10 wt.% and 15 wt.% B (designated H-B10 and H-B15), and HTPB containing B@Viton composites with 10 wt.% and 15 wt.% B@Viton (denoted as H-B10V10 and H-B15V10). Ignition and combustion experiments were conducted using a counterflow burner to assess the influence of B@Viton additives on HTPB-based solid fuels under varying oxygen mass flux conditions. To understand the thermal decomposition and oxidation behavior of B@Viton additives, thermogravimetric-differential scanning calorimetry (TG-DSC) was conducted, followed by an analysis of their oxidation behavior within the HTPB matrix. Results revealed that the addition of Viton altered the oxidation kinetics of B, leading to faster decomposition and gasification. Incorporating 10 wt.% B@Viton in HTPB (H-B10V10) resulted in a 52% regression rate increase compared to pure HTPB at an oxidizer mass flux of 74 kg/(m2·s). Pure HTPB had the shortest ignition delay time with 227 ms, the ignition delay time increases with an increase in the weight percentage of B, except for Viton-coated samples H-B10V10 (232 ms) and H-B15V10 (241 ms). A proposed combustion mechanism suggested that Viton enhances B combustion by facilitating oxide layer removal and promoting gas-phase reactions.

Bo Li, Clément Foucart, Xiaowen Zhou

We study the explosion phenomenon of nonlinear continuous-state branching processes (nonlinear CSBPs). First an explicit integral test for explosion is designed when the rate function does not increase too fast. We then exhibit three different regimes of explosion when the branching mechanism and the rate function are regularly varying respectively at $0$ and $\infty$ with indices $α$ and $β$ such that $0\leqα\leq β$ and $β>0$. If $α>0$ then the renormalisation of the process before its explosion is linear. When moreover $α\neq β$, the limiting distribution is that of a ratio of two independent random variables whose laws are identified. When $α=β$, the limiting random variable shrinks to a constant. Last, when $α=0$, i.e. the branching mechanism is slowly varying at $0$, the process is studied with the help of a nonlinear renormalisation. The limiting distribution becomes the inverse uniform distribution. This complements results known in the case of finite mean and provides new insight for the classical explosive continuous-state branching processes (for which $β=1$).

Santhosh G, J. Anju, Supriya N et al.

Propellant formulations containing a novel high nitrogen azotetrazole salt viz., diammonium 5,5′-azotetrazolate (DAAzT) along with two different binders viz., hydroxyl terminated polybutadiene (HTPB) and glycidyl azide polymer (GAP) were realized as potential pyrogen-based gas generators for use in inflatable structures. The DAAzT-GAP and DAAzT-HTPB propellant systems were investigated for their gas generating capabilities and it was found that the GAP based system offers enhanced gas yield of ∼430 mL/g against ∼320 mL/g for the HTPB based propellant at standard operating pressure of 1 bar and temperature of 298 K. Combustion product analyses of the propellant were undertaken by pyro GC–MS and it was found that the combustion products are benign and constitutes 62% and 53% N2 (mass fraction) as major combustion products from GAP and HTPB propellant respectively. A detailed thermal analysis of DAAzT by isoconversional method of Vzayovkin was undertaken and the dependence of activation energy with conversion was evaluated. The activation energy was also determined using a classical Kissinger method. The impact and friction sensitivity of the promising GAP-DAAzT propellant was found to be 3 Nm and 360 N respectively and the auto ignition temperature is 177.0 °C. Functional evaluation and gas generating capability of DAAzT-GAP propellant were successfully demonstrated in a sub-scale inflation test in a stand-alone configuration.

Nawel Matmat, Amir Abdelaziz, Djalal Trache et al.

The current study presents a successful elaboration and characterization of an innovative energetic composite based on nitrocellulose and nitrostarch (NCNPS) dual-biopolymers, and ammonium perchlorate (AP). A pre-establishment of the optimal formulation of the AP@NCNPS composite has been determined through a theoretical estimation of the ballistic performance via CEA-NASA software. The obtained composites were then fully characterized by FTIR, DSC, and TGA analyses. The IR-spectroscopy depicted the presence of all the characteristic groups of ester nitrates, revealing that the incorporation of AP did not alter the chemical structure of the dual-biopolymers. The thermal analysis demonstrated a mutual catalytic effect between AP and NCNPS biopolymeric matrix supported by the decrease of the maximum degradation temperatures observed for all the decomposition stages of AP@NCNPS composite after the incorporation of the oxidizer. The thermo-kinetic investigation, carried out using linear and non-linear isoconversional approaches (TAS, VYA/CE) demonstrated a considerable reduction in the activation energy values, highlighting, once again the role of AP in the improvement of the thermolysis process of the prepared AP@NCNPS energetic composite.

Ryo Sawada, Yudai Suwa

Details of the core-collapse supernova (CCSN) explosion mechanism still need to be fully understood. There is an increasing number of successful examples of reproducing explosions in multidimensional hydrodynamic simulations, but subsequent studies pointed out that the growth rates of the explosion energy $\dot{E}_\mathrm{expl}$ of these simulations are insufficient to produce enough $^{56}$Ni to match observations. This issue is known as the `$^{56}$Ni problem' in CCSNe. Recently, however, some studies have suggested that this $^{56}$Ni problem is derived from the simplicity of the explosion model. In response, we investigate the effect of the explosion energy growth rate $\dot{E}_\mathrm{expl}$ on the behavior of nucleosynthesis in CCSNe in a more realistic model. We employ the 1D Lagrangian hydrodynamic code, in which we take neutrino heating and cooling terms into account with the light-bulb approximation. We reiterate that, consistent with previous rebuttal studies, there is the $^{56}$Ni problem: Although $^{56}$Ni is synthesized to almost the same mass coordinate independent of $\dot{E}_\mathrm{expl}$, some of the innermost material in the low-$\dot{E}_\mathrm{expl}$ model failed to escape, leading to a shift in the innermost mass coordinate of the ejecta to the outer positions. Comparing our results with observations, we find that while modern slow explosions can, in principle, reproduce observations of standard Type II SNe, this is not possible with stripped-envelope SNe. Our finding places a strong constraint on the explosion mechanism. There are significant differences in the progenitor structures and the explosion mechanism between Type II and stripped-envelope SNe.

Justin Darku Quansah, Xuexue Zhang, Qazi Wasiullah et al.

The mechanical properties of energetic crystals (ECs) are relevant to the safety and performance of ammunitions and propellants. Several experimental and theoretical investigations have been conducted on different ECs to study their mechanical properties and effects on sensitivity and stability. Using evaluation methods such as nanoindentation, Raman spectroscopy, and molecular dynamic simulations, a significant amount of helpful information on this topic has emerged, some of which are summarized herein. The overall safety and performance of energetic materials depend on the properties of the energetic crystalline ingredients. Properties such as the thermostability and sensitivity of such crystals have been greatly improved using methods such as cocrystallization, recrystallization, coating, and intercalation. The overall strength and, thus, the safety of formulations largely depend on the quality and mechanical strength of included ECs. Therefore, it is essential to investigate the mechanical strengths of the modified ECs. This review also summarizes various theoretical and experimental methods to study the mechanical properties of pure ECs. As a proposal, additional research on the mechanical strength of modified hybrid ECs with improved energy density and sensitivity is necessary to ascribe the inherent mechanisms.

Leonid L. Fershtat

In recent years, the development of novel advanced energetic materials has significantly shifted toward nitrogen heterocyclic derivatives, which demonstrate a great potential for multipurpose application patterns. Among known heterocycles tetrazine ring is a well-known structural scaffold used in a preparation of various high-energy materials. The majority of energy-rich substances incorporating the tetrazine subunit exhibit high thermal stability, good detonation performance and low sensitivity to mechanical stimuli which defines their practical usability. In this review, the main achievements on the synthesis and performance of tetrazine-based energetic materials reported in last decade are summarized. Potential applications of the presented high-energy compounds are especially emphasized.