ABSTRACT In this contribution, we propose an alternative reaction pathway for the formation of isowurtzitane cages. These cage products are the basis for the synthesis of CL‐20, a highly prized energetic material and propellant. Isowurtzitane cages are typically formed under acid‐catalysed conditions via the condensation reaction between glyoxal and certain amines. Here, we report the cage formation proceeds via a series of addition reactions from the previously established diimine intermediate. This reaction pathway has been investigated in detail with HRMS and NMR, as well as isolation of key intermediates providing a comprehensive alternative pathway for the cage formation.
ABSTRACT The mechanical behaviour of solid gun propellants has attracted significant interest in the field of ballistics over the past several decades, resulting in substantial research studies and publications. Previous investigations have primarily concentrated on uniaxial quasi‐static compression testing and dynamic characterization of large caliber gun propellants, attributed to their superior handling and machinability. However, there is a notable scarcity of publications addressing theoretical material modelling and finite element modelling (FEM) validated by experimental data. At Fraunhofer EMI, ongoing research focuses on characterizing medium and large caliber cylindrical gun propellants through uniaxial compression tests with strain rates in the range from 0.008 to 3 s −1 , alongside the development of finite element simulation models for predictive analysis of propellant behaviour. This paper presents a brief literature review of prior work on the mechanical characterization and material modelling of solid gun propellants, followed by experimental results from uniaxial compression tests conducted at Fraunhofer EMI on two common gun propellants: a reference triple base and JA2 as double base formulation. Additionally, preliminary results of finite element modelling of these compression tests using the commercial finite element code LS‐DYNA are reported.
ABSTRACT TKX‐50‐based explosives, owing to their high detonation performance and low sensitivity, are considered promising candidates for future warhead main charges. Existing studies have primarily focused on synthesis optimization, composite material design, thermal decomposition mechanisms, and basic detonation parameters, whereas investigations into the static blast pressure field of TKX‐50‐based explosives remain limited. In this work, a numerical simulation model of the static blast shock wave pressure field of TKX‐50‐based explosives was established using LS‐DYNA. The simulated overpressure results show good agreement with experimental data, with deviations within 6%, demonstrating the reliability of the proposed model. On this basis, the effects of key operating parameters—including scaled distance, burst height, length‐to‐diameter ratio, and initiation mode—on the shock wave pressure field of TKX‐50‐based explosives were systematically investigated. Furthermore, LS‐OPT was coupled with LS‐DYNA to conduct optimization analysis, through which a numerical prediction of the optimal blast height was determined within a selected range of parameters.
ABSTRACT As an important insensitive melt‐cast matrix, the energetic properties of DNAN are frequently enhanced by loading high‐energy components like HMX. However, the dissolution behavior in molten DNAN significantly influence the crystallization process and the ultimate security performance. In this study, DNAN was employed as melt‐cast matrix and HMX as the high‐energy filler. By utilizing the hot‐stage microscopy equipment for in‐situ observation and sensitivity testing, we investigated the dissolution‐precipitation behavior of HMX in DNAN and its effects on crystallization characteristics and mechanical sensitivity. The results indicate that HMX dissolution preferentially occurs in crystal edges, corners and protruding parts, and its dissolution kinetics follow a diffusion‐controlled mechanism: . The dissolution rate constant K negatively correlate with the local particle concentration. The presence of HMX dramatically influences the crystallization process of DNAN and slightly dissolved HMX molecules suppress the crystallization of DNAN system, leading to a decrease in crystallization temperature, an increase in supercooling, and grain refinement. Furthermore, crack defects are easily formed near HMX particles after solidification owing to uneven heat conduction and contraction stress. Simultaneously, the dissolution‐precipitation behavior of HMX significantly improves impact safety (with the H 50 of tablet increasing by approximately 1.8 times compared to powder), whereas the improvement of friction sensitivity is relatively limited. This study reveals the correlation between dissolution‐precipitation behavior of HMX and the structure‐performance of melt‐cast explosives, providing guidance for safety design and manufacturing of the insensitive melt‐cast explosive.
ABSTRACT Ammonium dinitramide (ADN)‐based liquid propellants are promising because of their high energy density. Electrical ignition offers a simple means of triggering combustion in such ionic liquids. However, the electrolysis behavior of ADN‐based formulations remains poorly investigated. This study aims to clarify the electrolysis of an equimolar mixture of ADN and hydroxyethylhydrazinium nitrate (HEHN). Herein, chronoamperometry combined with in situ Raman spectroscopy was conducted to analyze the liquid phase under an applied voltage, and in situ high‐resolution time‐of‐flight mass spectrometry (HRTOFMS) was used to characterize the evolved electrolysis gases at the anode and cathode. ADN/HEHN exhibited a higher chronoamperometric current density than neat HEHN, indicating that ADN acts as a charge carrier, thereby enhancing electrical conductivity. In situ Raman spectroscopy revealed a time‐dependent decay of bands assigned to ADN and HEHN, demonstrating that dinitramide and nitrate anions are the principal electroactive species at both electrodes. HRTOFMS revealed that nitrous oxide (N 2 O) and water (H 2 O) were the major gaseous products, with large amount of N 2 O produced at the cathode. Based on these observations and previous study findings, a possible electrolysis reaction mechanism is proposed: at the cathode, the reduction of dinitramide anions (DN − ), ADN, and nitrate anions leads to the formation of N 2 O, H 2 O, and NH 3 through subsequent reactions, whereas at the anode, the oxidation of DN − and nitrate anions produces N 2 O and H 2 O via follow‐up reactions. These results reveal that ADN/HEHN electrolysis directly produces oxidizing species such as N 2 O, which, together with fuel species produced by pyrolysis, facilitate ignition.
ABSTRACT High‐energy materials (HEMs) are critical for propulsion and defense domains, yet their discovery remains constrained by experimental data and restricted access to testing facilities. This work presents a novel approach toward high‐energy molecules by combining long short‐term memory (LSTM) networks for molecular generation and attentive graph neural networks (GNN) for property predictions. We propose a transformative embedding space construction strategy that integrates fixed SHA‐256 embeddings with partially trainable representations. Unlike conventional regularization techniques, this changes the representational basis itself, reshaping the molecular input space before learning begins. Without recourse to pretraining, one of the proposed models for low data regime achieves 74.3% validity and 47.1% novelty. The generated library exhibits a mean Tanimoto coefficient of 0.214 relative to the training set signifying the ability of framework to generate a diverse chemical space. We identified 37 promising candidates for further research, all exhibiting a predicted detonation velocity greater than 9 .
ABSTRACT Toxic fume formation, particularly carbon monoxide (CO), is a major concern in ammonium nitrate fuel oil (ANFO) and emulsion explosives, impacting both safety and operational costs. This study demonstrates that using ultra‐clean, synthetic gas‐to‐liquids (GTL) fuel phases used in an emulsion matrix can reduce CO emissions by 20% compared to conventional mineral oils. The reduction is attributed to the combination of chemical composition—primarily isoparaffins—and physical properties of GTL fuels. Tests were conducted in a controlled blasting chamber at the Swedish Blasting Research Centre (Swebrec), ensuring consistent and replicable results. Emulsions were manufactured and tested multiple times in two different campaigns, confirming lower CO emissions but varying NO x emissions. The findings highlight the importance of fuel phase selection in explosive performance and toxic emissions. A literature model was used to elaborate on the potential impact on re‐entry time. The study underscores the value of controlled testing environments for accurately assessing post‐blast gas emissions.
Lithium pentazolate (LiN5) is a novel nitrogen-rich energetic material that exhibits excellent detonation properties. However, it is difficult to control its crystal morphology after precipitating from a single solvent. Herein, various crystal morphologies were obtained by adjusting the solvents (NMP, DMA, DMF, and EtOH) and antisolvents (DCM, EA) combination. In contrast to the raw material with a cubic morphology, the LiN5 crystals derived from DMA-EA adopt a rod-like morphology, while the EtOH-EA and EtOH-DCM yield tetragonal block-like and quasi-ellipsoidal morphologies, respectively. Both cubic and tetragonal block-like crystals show higher thermal stability (159 degrees C-161 degrees C) than that of rod-like and quasi-ellipsoidal counterparts (148 degrees C-150 degrees C). The impact sensitivity (IS) of quasi-ellipsoidal crystals (IS = 25 J) is superior to that of rod-like (IS = 8 J) and tetragonal block-like (IS = 15 J) morphology. Unfortunately, the desired quasi-ellipsoidal crystals exhibit slightly higher hygroscopicity with a water content of 7.8% under the same conditions. Moreover, XRD analysis shows that the EtOH solvent leads to a significantly enhanced diffraction peak corresponding to the (430) plane of LiN5, whereas the EA antisolvent results in an additional distinct peak assigned to the (432) plane. Our results propose a general strategy for regulating the crystal morphology of LiN5, further revealing the connection between crystal morphology and physical-chemical properties.
ABSTRACT Creep is a core pathway for damage accumulation in solid propellants during long‐term storage and service, directly affecting the structural integrity of solid rocket motor grains. At present, there are bottlenecks in the research on creep damage of solid propellants, with no breakthroughs achieved in the laws of damage accumulation at various stages of creep, high‐precision constitutive models, research on mesoscopic creep damage evolution, and research on creep damage inhibition. This paper systematically reviews domestic and international research results on the mechanical response characteristics and constitutive models at various stages of macroscopic creep of solid propellants, analyzes the potential application of current mesoscopic observation technologies in the characterization of creep damage evolution, and summarizes the implementation effects and action mechanisms of inhibiting creep damage from the perspective of internal and external influencing factors. In view of the current bottlenecks, it points out the future research directions of solid propellants creep damage, providing theoretical support and technical reference for the evaluation of solid propellants creep damage and the optimization of model prediction under long‐term storage conditions.
This study employed a solvent evaporation method to coat ammonium nitrate (AN) particles with a mixture of stearic acid and arachidic acid to mitigate their hygroscopicity. Results indicate that the mixed coating layer outperforms coatings consisting of single surfactants. Optimal coating efficiency was achieved under the following conditions: a stearic acid-to-arachidic acid mass ratio of 1:3, a total mixed-solvent volume of 30 mL, an ether-to-acetonitrile volume ratio of 1:5, and a coating temperature of 40 degrees C. Under these conditions, moisture absorption was reduced by 40.26%. The coated samples were characterized by a variety of techniques. Scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), raman spectroscopy (Raman), and x-ray diffraction (XRD) confirmed that the coating agents were successfully introduced onto the surface of AN, while the crystal structure and polymorphic form of AN remained largely unchanged. Energy dispersive X-ray spectroscopy (EDS) indicated a surface coverage of 47.39%-47.58%, while X-ray photoelectron spectroscopy (XPS) showed an increase in the C1s/N1s ratio from 0.65 to 2.04. Furthermore, the coating did not significantly alter the decomposition temperature of AN, delayed moisture absorption by 6.64 h under identical conditions, and increased the water contact angle by 33.4 degrees.
To expand the application scope of coal-based materials and reduce the reliance of industrial explosives on conventional fossil fuels (diesel), this study replaces different proportions of diesel in site-mixed emulsion explosives with a coal-based slurry. The effects of the coal-based slurry on the microstructure, particle size distribution, rheological properties, and explosive performance of the explosives were systematically investigated. The results indicate that the addition of the coal-based slurry reduces the uniformity of the internal phase particle size distribution, widens the distribution range, and decreases the median particle size. Rheological analysis reveals that as the coal-based slurry content increases, the matrix viscosity rises while its temperature sensitivity decreases. A coal-based slurry content of 1% balances pumping viscosity requirements and operational safety. The emulsion matrix exhibits shear-thinning behavior, and increasing the coal-based slurry content expands the required shear rate range for pumping while enhancing the storage modulus, critical strain, and cohesion, thereby improving the structural stability of the matrix. Explosive performance tests show that at a coal-based slurry content of 0.5%, the average detonation velocity reaches its maximum, while at 1% coal-based slurry content, the brisance reaches its maximum. Detonation mechanism analysis demonstrates that the coal-based slurry acts not only as a combustible participant in the explosion reaction but also undergoes slight gasification during the process. This study opens new avenues for the application of coal-based materials and provides a viable strategy for reducing the dependency of industrial explosives on petroleum-based materials.
ABSTRACT Mechanical properties are a critical performance metric for many high explosive (HE) materials and tensile strength properties are particularly important. Direct tensile measurements using dogbone shaped samples are the gold standard but they have the disadvantage that they are fairly large and require samples machined from billets. Diametral compression, more commonly known as Brazil disk (BD) testing, is an indirect method for measuring tensile strength on smaller and more easily fabricated samples. A review of the BD literature is presented with an emphasis on tensile strength measurements in high explosive materials. BD literature is reviewed in three primary areas: (i) rocks and concrete, (ii) pharmaceutical materials, and (iii) high explosive materials. The literature for rocks/concrete is extensive and dates back over 80 years; despite this there is no consensus on the validity/accuracy of the BD technique or the optimal variant of the BD technique to employ. The pharmaceutical literature is the opposite, being limited in scope and quantity of studies. BD literature on high explosive materials falls in between, not as impressive as in the rocks/concrete community but more substantiative than in the pharmaceutical community. After the review of the literature practical parameters for HE BD testing and recommended future work is discussed.
ABSTRACT Furoxan‐based energetic salts have drawn particular attention among explosive and propellant researchers, owing to the tendency to form versatile combinations of this high‐oxygen–containing furoxan scaffold with other selected explosive and energetic N‐hetero rings, as well as feasible approaches to derivatize the already attached substituents, and the fine‐tunable energy and safety performance of the target salts. Focusing on the advancements and trends in this field, this systematic review aims to summarize the recent information concerning the synthetic approaches toward the functionalized furoxan‐based salts and for the furoxan ring construction and the corresponding physicochemical properties and energy performances, tries to investigate the improvement of hydrogen‐rich organic bases on density, energy level and sensitivities after forming salts with acidic furoxan parent compounds, and attempts to analyze the correlation of the crystal structures of the furoxan hybrids with the physicochemical properties and explosive/propellant performances. It is expected that the present digest could serve as a perspective platform facilitating a better understanding of the current state‐of‐the‐art in this important domain and guiding the further design and synthesis of the desired furoxan‐based salts, thereby achieving the aim of developing advanced energetic materials perfectly applicable for high‐value weapons.
Boron-based ionic liquids are a new generation of self-igniting propellants. The experiment obtained its basic combustion characteristics, but there is insufficient understanding of its detailed reaction mechanism. In this paper, the ReaxFF MD simulation method was adopted to explore the reaction mechanism of [AMIM]BH4 ionic liquid at the microscopic molecular level. The main reaction pathway of the [AMIM]BH4/HNO3 system was obtained. Research has found that the [AMIM]BH4/HNO3 system is dominated by the reaction between BH4 and HNO3. The proton transfer between BH4 and HNO3 in the system is the key to initiating the reaction, which generates the transient intermediates BH3 and H2NO3. Subsequently, the system is divided into two reaction pathways. Most of the BH3 will continue to dehydrogenate in the system to form BH2, while the other part will directly participate in the reaction in the system to generate H2BO intermediates. Both reaction pathways will eventually produce boron-containing oxides such as BO2. The decay of the [AMIM] cation begins with the attack of multiple HNO3, causing continuous reactions such as ring opening, oxygen uptake and chain breaking. In addition, a dynamic collision model was established to simulate the collision process between cations and anions and the oxidant in practical applications. The mean displacement curves (MSD) of [AMIM]BH4 to HNO3 and the diffusion coefficient D under different collision velocities were obtained. It was found that when the diffusion coefficient D was large, the initial chemical reaction in the subsequent system would be more intense under the corresponding conditions.
ABSTRACT BAMO (3,3‐bisazidomethyl oxetane)‐based polymers have emerged as a new generation of energetic binders, becoming a frontier research direction in solid propellants due to their high energy output and comparable safety properties. This review summarizes its advances from preparation, modification, and application perspectives. Starting from the synthesis of PBAMO, the relationships among synthesis‐structure‐property are first elaborated. Focusing on the crystallization issue, modification strategies are then categorized into copolymerization, chain extension, and hyperbranched for detailed discussion. Furthermore, a detailed assessment of BAMO‐based polymers in propellants is provided from application properties. The review concludes by summarizing the main bottlenecks currently faced and future directions, offering prospects from three aspects: developing continuous‐flow safe synthesis processes, rheology‐focused process intensification, and construction of process‐oriented simulation frameworks, accelerating the transition of BAMO‐based binders from laboratory research to industrial production.
Understanding the mechanisms of crack initiation and flame propagation in confined explosives under nonshock initiation accidents remains challenging due to the strong coupling between fracture and combustion. To address this, this work established a central-ignition crack propagation experimental technique with adjustable axial pre-load on the charge surface. In this setup, cracks are driven by high-pressure gases from burning black powder, decoupling the crack propagation from the bulk explosive reaction. High-speed photography was employed to capture crack evolution and flame propagation dynamics under different pre-loads and charge diameters. The results indicate the consistent formation of 3 to 4 radially distributed initial cracks. It is proposed to be determined by the effects of axisymmetric stress fields, system energy optimization, and crack-to-crack interaction. The number of these initial cracks is competitively regulated by the charge diameter and the pre-load. Furthermore, the propagation speed of the flame front within the cracks is quantified, revealing a distinct velocity jump (e.g., from 200 to 1000 m/s). This jump is attributed to a sharp decrease in flow resistance after the cracks fully penetrate the charge. This study provides novel experimental insights and data for understanding crack initiation and flame propagation behavior in nonshock initiation events.
ABSTRACT Aluminium oxide (Al 2 O 3 , alumina) is a widely studied metal oxide with applications in adsorption, sensing, and catalysis; however, many conventional synthesis routes are energy‐intensive and environmentally unfriendly. In this study, Al 2 O 3 nanoparticles were synthesized via a novel green route using lemon peel extract as a natural reducing and stabilizing agent. The obtained Al 2 O 3 nanoparticles were preliminarily evaluated as catalytic additives in the thermal decomposition of the insensitive energetic material 5‐nitro‐1,2,4‐triazol‐3‐one (NTO). Their effect was compared with that of commercially available micron‐sized Al 2 O 3 to assess the influence of particle size. Binary mixtures of NTO with nano‐ and micron‐sized alumina were prepared at selected weight ratios and examined by differential scanning calorimetry (DSC). The preliminary DSC results indicate a shift of the NTO decomposition peak toward lower temperatures in the presence of alumina, with a more pronounced effect observed for the Al 2 O 3 nanoparticles. These findings suggest that green‐synthesized Al 2 O 3 nanoparticles may influence the thermal decomposition behavior of NTO and suggest further systematic kinetic investigations.
ABSTRACT This review examines the ageing and service life of hydroxy‐terminated polybutadiene (HTPB)‐based polyurethane elastomers used as binders in solid composite propellants. Ageing is primarily governed by thermo‐oxidative degradation of the unsaturated polybutadiene backbone, which proceeds via a free‐radical oxidation mechanism and leads predominantly to additional crosslinking within the polymer network. As a consequence, the material progressively hardens, showing reduced elongation and loss of elasticity, with degradation initiating at relatively low temperatures (60–80°C). The ageing behavior is strongly influenced by formulation variables, including polymer microstructure, NCO/OH ratio, hydroxyl functionality, and curing chemistry. Accelerated ageing studies typically predict service lifetimes ranging from 5 to 15 years at room temperature, while the incorporation of antioxidants is essential to delay oxidative degradation. Despite these advances, existing research remains fragmented across individual studies, highlighting the need for integrated structure–property–ageing correlations. Future research should therefore focus on diffusion‐limited oxidation modeling and formulation strategies that combine controlled microstructure with optimized antioxidant systems to improve lifetime prediction accuracy. Although this review does not address full propellant systems, it is important to note that binder behavior may differ due to compatibility issues among propellant ingredients.
