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Introducing additional oxidizers in aluminized explosives is an effective way to improve energy performance by enhancing the secondary combustion reaction. In this work, perfluorocarbon as oxidizer has been introduced into TATB/Al based energetic materials to improve combustion reaction and energy output performance. The uniform TATB/Al/perfluorocarbon composites are prepared through acoustic resonance mixed technology, and the energy and pressure output performance are fully studied in air blast and underwater explosion. A significantly exothermic peak derived from the reaction between fluorine and Al is observed between 540 ℃ and 580 ℃ for TATB/Al/perfluorocarbon. The heat of explosion of TATB/Al/perfluorocarbon is increased first and then decreased with F/Al ratio from 0 to 0.608. The highest heat of explosion is 6021 J/g for TATB/Al/perfluorocarbon with F/Al ratio of 0.274. Furthermore, the enhanced working capacity, the significantly enlarged fireball and relatively high overpressure are obtained for TATB/Al/perfluorocarbon. More importantly, the shock impulse and first bubble oscillation time of TATB/Al/perfluorocarbon have been increased by 23.2% and 21.18% during underwater explosion, respectively. The results further illustrate that adding perfluorocarbon is a feasible approach to enhance energy output due to combustion reaction between fluorine and Al, which can be applied in explosives and propellants.

In the field of energetic materials, traditional materials with high toxicity or other disadvantages are mostly used. There is an urgent need for trinitrotoluene replacements (TNT), which itself is toxic and its production is problematic due to red wastewater. New materials should be safe to handle, have good performance, and be inexpensive to synthesize. Nitratoalkylazoles are known to have low melting points and good energetic properties compared to TNT. In this paper, seven energetic compounds are synthesized starting from 5-methyltetrazole, 5-hydroxymethyltetrazole and 4,5-bishydroxymethyltriazole. The nitrates are characterized in terms of their physical, chemical, and energetic properties. Of those seven compounds, five are solid, melting between 27 °C and 110 °C, and two are liquid. Methylation and hydroxyalkylation were performed and discussed extensively. The organic nitrate is introduced in the last step so that the synthesis remains safe and scalable. Correlations between the molecular geometry and the melting points are explained. Calculations indicate detonation velocities that are 6%–11% higher than those of TNT. A discussion of the effect of isomerism on the properties leads to surprising insights and should help focus and accelerate research on the replacement of TNT.

Boron, a high-energy metalloid has been recognized as a potential secondary energy source for liquid hydrocarbon fuel to power volume-limited propulsion devices such as ramjet and scramjet. The higher volumetric and gravimetric energetic content makes boron a more suitable candidate than other energetic particles. The stability of the particle is one of the significant drawbacks of adopting metal particles in liquid fuel, which gel fuels can overshoot. Though several works have been published on metalized and non-metalized gel fuels, studies focusing on boron-loaded gel fuels are scarce. The present work comprehensively reviews recent advancements and challenges in adopting boron-loaded gel fuel for practical ramjet and scramjet propulsion devices. It mainly encompasses the formulation of boron-loaded gel fuel, rheological behavior and its influencing factors, single droplet combustion characteristic, spray characteristics, spray combustion characteristics, and the effect of boron-loaded gel fuel on the performance of practical ramjet and scramjet combustors.

This study conducted a detailed examination of the characteristics of hydroxyl‑terminated polybutadiene (HTPB) doped with potato starch nitrate (NPS) as a high-energy-density binder. The investigation specifically focused on evaluating the impact of NPS doping on the chemical structure, energetic attributes, and thermokinetic behavior of HTPB-NC binder systems. The findings demonstrated advantageous features, including favorable chemical compatibility, improved material density accompanied by remarkable thermal stability, substantial energy release, and high chemical reactivity. These findings contribute to the understanding of HTPB-NPS composite and offer evidence for its remarkable features, indicating promising prospects for its utilization in the development of advanced formulations for high-energy-density propellants in future applications.

The present work aims to study the effect of environmental hazards, namely, temperature and humidity, on the performance and sensitivity of tracer pyrotechnic composition. The experiments showed that the different pyrotechnic compositions, aged under different conditions, are prone to become more sensitive to impact and friction. It is also revealed that aging has a negative impact on luminous intensity for which the thermal aging declined the light intensity by 38.5%, while the moisture deteriorated it by 66%, compared to the pristine composition. The thermal analysis of the aged pyrotechnic compositions demonstrated a direct correlation between the heat of reactions and the magnesium content, the primary heat source, which decreases due to the formation of metal oxides (Mg(OH)2 and MgO) during the aging process. This investigation will certainly contribute to comprehensively understanding the degradation mechanism of tracer pyrotechnic compositions, and provide information on how the physical status of materials influences the luminosity, the sensitivity, and the heat of combustion reaction.

The results of modeling the accumulation of slag residue in the combustion chamber of a propulsion system on pasty propellant obtained using a multiphase flow evolution model are presented. The influence of composition solutions on the process of slag formation is established; the significance of this process for the quality of such engines is shown. The nature of the influence of the parameters of the burning process for propellants of the type under consideration on the intensity of slag formation is determined. It is shown that the degree of involvement of metallic fuel in the agglomeration process has the greatest influence on slag formation. It has been established that the most effective ''tool'' for suppressing slag formation in the combustion chambers of paste propulsion is to change the regularities of the burning process, mainly associated with the formation of condensed products at the surface of the burning propellant.

Perchlorate compounds are well-known for their explosive and hazardous nature. Considering previously reported perchlorate crystals of salen-type manganese (III) complexes, our study aimed to identify the specific molecular/crystal structure responsible for their explosive properties. Employing deep learning, we conducted an analysis of the Hirschfeld surface for salen-type metal complexes within a crystal structure database. The results indicate that the salen-type complex site lacks distinctive structural features, attributing its explosive potential to the chemical bonding of the perchlorate ion and the surrounding intermolecular interactions.

Metal fuels, such as aluminum (Al) and iron (Fe), can be added to composite solid propellants to improve their performance, such as specific impulse, density, and burning rate. In comparison to aluminum, iron can theoretically provide improved density specific impulse and higher flame temperatures; reduce condensed combustion product (CCP) concentration and the associated two-phase flow losses; and eliminate hydrochloric acid (HCl) in the exhaust products. A fundamental and quantitative understanding of metal particle aggregation and agglomeration processes in solid propellants is required to understand the underlying combustion mechanisms in these systems. In the current study, composite strand and laminate AP/HTPB/AP propellant samples loaded with Fe microparticles (∼45 μm in diameter) were burned at elevated pressures in an optically accessible strand bomb. Combustion processes were monitored with transient pressure diagnostics and a high-speed camera fitted with a high-magnification lens system (3.83 μm/pixel resolution) for the laminate propellant experiments. An automated image processing algorithm was developed to measure burning rates and ejected particle/agglomerate sizes and velocities. Time-resolved statistical distributions of both particle size and velocity are presented at elevated pressure for multiple laminate propellant experiments with a high degree of repeatability and low measurement error estimated as < ±5% and < ±1.5% for particle size and velocity, respectively. The incorporation of iron microparticles into the composite strand propellants yielded over a 20% increase in the global burning rate over the range of pressures evaluated (3.45–13.8 MPa). Similarly, the addition of iron to the fuel lamina in laminate propellant samples led to an approximately 30% increase in the global burning rate at the evaluated pressure (3.45 MPa). Additive particles were observed to eject near the oxidizer/fuel interface, or to melt, aggregate, coalesce, and agglomerate on the fuel lamina surface prior to ejection. Particle velocities are controlled by a balance of gravitational forces, drag forces imparted by expanding combustion product gases, and particle inertia. The observed combustion enhancements are attributed to the combined effects of catalytic mechanisms, increased radiation heat transfer, and local energy release from reacting iron particles. In addition, discussions on the image processing methods developed in the current study, corresponding potential sources of error, and prospective areas of improvement are provided. The experimental approach developed enables high-speed and high-magnification visualization of propellant combustion at high pressures and can be utilized to better understand the fundamental combustion behavior of energetic systems.

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.

Nowadays, porous structures have exhibited many novel characteristics in the microstructure design of energetic materials, which possesses a unique impact on the macroscopic properties of energetic materials, and thus have exhibited a wide range of application prospects. In this review, several typical porous structures were introduced from the aspects of synthesis, performance and structure, and the main research progress of porous structures applied to the design of energetic materials in recent years was reviewed. Specifically, this article discussed the impact of nanopores, ordered structures and high specific surface areas on the safety and energy release of typical energetic materials, and focused on research area including the explosive adsorption and detection, new host-guest explosives, and new porous energetic materials. At the end of the review, an outlook and discussion were provided on the development trend of the combination of porous structure and explosives.

Microscale energetic materials have garnered considerable attention because they can be integrated in microelectromechanical systems for several potential applications. Hexanitrostilbene (HNS) has been widely utilized in ignition and initiation devices owing to its excellent thermal and shock stability and high sensitivity to short pulse shock waves. To meet the energy release requirements of micro-detonation devices, HNS sticks were prepared using direct ink writing and their reaction and flame propagation properties were studied. HNS particles sized 17.5 µm to 5 µm and ∼500 nm was prepared. Then, the viscosity of HNS-based inks prepared via acoustic resonance technology decreased when the particle size decreased or when the HNS content reduced from 97 wt.%, 95 wt.%, and 92 wt.%, to 90 wt.%. Additionally, the HNS-based inks with different binders exhibited different viscosity. The effect of the inner diameter of needle (0.4 mm, 0.6 mm, and 0.9 mm), printing rate (13 mm/s, 15 mm/s, 17 mm/s, 19 mm/s), and pressure (0.05 MPa, 0.1 MPa, 0.15 MPa, 0.2 MPa) on the width of HNS sticks was also elucidated. HNS-based sticks with a diameter of 0.9 mm underwent self-sustaining combustion reactions, and the burning rate increased from 5.1 mm/s to 6.8 mm/s as the particle size decreased from 17.5 µm to 500 nm. Overall, this work provides an effective approach to prepare microscale HNS for integration into micro-energetic devices.

Combustion of dispersed metals in an oxidizing environment is of practical interest, which is related to the prediction of characteristics of high-energy compositions (HECs) containing metal powders, as well as the characteristics of various propulsion systems and gas generators. The research studies peculiarities of ignition and combustion of dispersed systems of Al, B and Al-B mixture in gas products formed during thermal decomposition and combustion of HEC components. In the study of the characteristics of ignition and combustion, the development of flame processes, a continuous CO2 laser (high-speed radiant heating) and a continuous-pressure flow bomb (stationary combustion), including the filter system for the capture of condensed combustion products (CCPs) were applied. It was found that the high reactivity of dispersed Al reduces the ignition time and increases the burning rate of HECs, and increases the volume fraction of fine condensed particles. The use of amorphous B or Al-B mixture (17.2/82.8 mass ratio) increases the ignition time (up to 62%) and significantly reduces the burning rate of HECs, at the same time, the volume share of large CCPs increases due to the melting of the oxide layer on the surface of B particles and their increased cohesion. Analysis of CCPs showed that fine and large agglomerate particles were formed on the surface of the reactive HEC layer, which contain oxides of the metals used. When Al particles are burned together with B particles, complex oxides (aluminum borates) can be formed.

This study demonstrates the thrust modulation capabilities of a hybrid rocket motor employing a Multi-Layered Tubular (MLT) fuel grain. The MLT configuration involves arranging the fuel grains with distinct regression rates as layers. As combustion progresses, the regression rate changes based on the burning of each fuel layer, leading to variable thrust while maintaining a constant oxidizer flow rate. Variable-thrust fuel grains are suitable for diverse mission types, including employment in sounding rockets and cruise missiles, particularly those designed for anti-ship operations and missions wherein a boost-sustain thrust profile is required. The MLT fuel grains were designed for a boost-sustain phase thrust profile generally observed in missiles. Wax was used as a booster fuel, and wax with 20%EVA was used as a sustainer fuel. Two MLT configurations with different durations for the boost phase were demonstrated. During the tests, the boost-sustain phase was achieved successfully. However, a transition phase was observed while shifting from the boost to the sustain phase. The delay of the transition phase was observed to increase when the duration of the boost phase increased. The combined effect of axial variation of fuel regression rate and local mass flux is the reason for the transition phase. The Thrust Turn-Down Ratio (TDR) for Multi-Layered Tubular (MLT) fuel grains was calculated. At a web thickness (for booster fuel) of 4 mm, the TDR was approximately 1.23:1, and at a 5.5 mm web thickness, it was 1.28:1. Further, 20%Mg was added to the wax to increase the regression rate of booster fuel. The Wax/20%Mg fuel showed 41% and 14% improvement in regression rate and thrust, respectively. The TDR was improved marginally compared to pure wax-based MLT grain.

This work details the study conducted on composite solid propellants with activated copper chromite (ACR) as burn catalyst for its burn rate change with time due to the interaction of ammonium perchlorate (AP) with ACR. One of the hypotheses cited for burn rate reduction is the conversion of chromite in ACR to chromate by an electrolytic reaction with moisture in the presence of ammonium perchlorate. This hypothesis was studied by a design of experiments which includes blending ammonium perchlorate and ACR, Aluminum and ACR, stand alone ACR in raw material stage and the blends storage with time. The effect of moisture in AP is addressed by comparing undried and dried AP in the blends. The blended raw materials were characterized by Thermo-gravimetric analysis, Particle Size Distribution, surface area measurement, Scanning Electron Microscopy and chromium estimation. Results show that the conversion of chromium from chromite to chromate is very minimum in the presence of AP. Propellant samples are prepared with these blends at different time intervals to understand viscosity, mechanical properties and burn rate behavior with raw material storage. Experimental results show burn rate shows an opposite trend of increase with blend storage of 6 months. A plausible explanation for this observation is presented in the paper correlating the experimental conditions.

The present study aims to elucidate the decomposition mechanism and gas evolution characteristics of a promising energy-rich carbamated microcrystalline cellulose nitrate (M3CN). The molecular structure and morphological characteristics of starting microcrystalline cellulose carbamate (MCCC) and its nitrated derivative were examined using FTIR and SEM techniques. Thermal analysis using TGA and DSC revealed distinct decomposition behaviors for MCCC and M3CN. MCCC exhibited endothermic decomposition linked to the degradation of the cellulosic structure. In contrast, an exothermic decomposition event was observed for M3CN, attributed to the cleavage of energetic groups within the nitrated cellulosic chains. Furthermore, the hyphenated TG-FTIR analysis confirmed that the primary gaseous products emitted during the pyrolysis of M3CN included NO, N2O, NO2, CO2, H2O, CH4, HCHO, HCN, and CHNO. The findings of this study enhance our understanding of the pyrolysis mechanism in cellulose-based energetic materials, providing a significant reference for forthcoming research and explorations in this field.

Due to the high dispersion of solid powder, it is very easy to form a powder/gas hybrid system, which greatly increases the probability and severity of explosion accidents. The researchers both domestically and internationally have conducted extensive research on the hybrids explosion systems. This paper reviews the combustion characteristics, explosion mechanisms, and explosion prevention experiments of hybrids. Current research results on explosion prevention technology are organized, and the current challenges in experimental studies of hybrids explosions are summarized, providing references for future experimental studies.

In light of the challenges posed by the low density, diminished energy levels, and shrinkage holes in the loading arise of the current cast-cured explosive liquid vehicle, TNT, the investigation of low-melting eutectic materials as potential substitutes for TNT has emerged as a focal point of research. By employing the solvent-nonsolvent method, the lowest eutectic mixture of TNBA(2,4,6-trinitro-3-bromoanisole)/MTNP(1-methyl-3,4,5-trinitropyrazole) was synthesized, distinguished by a moderate melting point and markedly elevated energy levels as compared to TNT. Comprehensive SEM, EDS, IR, XRD, and XPS analyses were conducted on the lowest eutectic mixture, substantiating the absence of any chemical interaction between TNBA and MTNP and affirming their exceptional compatibility. Moreover, an exploration into the thermal decomposition behavior and mechanism of the lowest eutectic mixture was undertaken, its mechanical sensitivity was tested, and its detonation performance was evaluated by EXPLO-5 software. The thermal decomposition parameters of the lowest eutectic mixture closely paralleled those of the precursor materials, with the thermal decomposition kinetics model function being identified as the Jander function. The impact sensitivity of the lowest eutectic was 48.1 cm and the friction sensitivity was 12%. Furthermore, the density of the lowest eutectic mixture surpassed 1.8 g/cm3, and its detonation velocity approached 8000 m/s, markedly surpassing the explosive performance of TNT.

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.

Co-agglomeration unique crystal engineering approach; in which the co-precipitated micro-particles of nitramines with other energetic materials co-agglomerated by the slurry method; to modify the energetic properties of attractive nitramines like CL20, HMX, BCHMX, and RDX etc. The interesting properties and structural modifications in newly prepared co-agglomerated crystals (CACs) interesting one are discussed here. There are notable variations in the crystal morphologies and packing of crystals, including key properties like relatively high density, melting point, impact sensitivity, and detonation properties. These CACs are in the overwhelming and majority showing properties like co-crystals. Apart from these aspects, co-agglomeration provides a huge opportunity to tune the key properties and performance of existing energetic materials and is easy to scale-up for the industrial level. These preliminary results also suggest that chemical engineering factors are involved in the preparation of CACs and have tremendous improvements than the conventional crystallization. With technological optimization this method can be employable industrial scale production.

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.

Aluminum (Al) holds a pivotal role in augmenting the energetic potential of solid fuel formulations. Its incorporation can notably amplify the energy yield upon combustion. Nevertheless, challenges such as ignition delay and incomplete combustion have hindered its optimal utilization. In the context of hybrid rocket propulsion, where reignition and high regression rates are sought, a promising solution lies in harnessing the potential of metal-fluoropolymer combinations. This paper explores the influence of polytetrafluoroethylene (PTFE) and Viton fluoropolymer additives on the combustion and regression rates of hydroxyl‑terminated polybutadiene (HTPB)-based solid fuels loaded with nano-aluminum (nAl). To comprehensively address these objectives, binary composites of nAl-PTFE and nAl-Viton were prepared using high-energy ball-milling, and the resulting mixtures were incorporated into hydroxyl‑terminated polybutadiene (HTPB)-based fuel through a vacuum-casting technique. The ignition and combustion characteristics of the solid fuels, as well as the post-combustion products, were examined using an opposed flow burner setup to gain insights into their oxidation and combustion mechanisms. The findings demonstrate that the inclusion of PTFE and Viton in nAl has a positive impact on the ignition delay time, combustion behavior, and regression rates of the solid fuels. The HTPB-nAl-PTFE(S3) sample exhibited the shortest ignition delay time of 108 ms, outperforming the other tested samples (S1: 227 ms, S2: 182 ms, S4: 122 ms). Furthermore, the addition of nAl to pure HTPB resulted in an average regression rate of 0.3–0.6 mm/s for HTPB-nAl (S2), representing a two fold improvement compared to pure HTPB-based samples. Compared to the baseline HTPB fuel, HTPB-nAl-PTFE(S3) demonstrated a significant increase in regression rate by approximately 178%, while HTPB-nAl-Viton(S4) exhibited an increased regression rate of 122%. These results highlight the positive influence of fluoropolymers on combustion behavior, ultimately enhancing the overall performance of the fuel. Additionally, the study observed gas-phase reactions during the combustion process, including the reaction between nano-aluminum (nAl) and fluoride, the intermediate product of Al oxidation, and the decomposition products of fluoride. These reactions resulted in the faster fracture of the alumina (Al2O3) shell, leading to improved heat release and regression rate performance.

Over the past few years, there has been a growing recognition of the importance of multi-spacecraft missions for a variety of purposes, including Earth observation, navigation, guidance, climate monitoring, and environmental monitoring. The trend amongst agencies is to favour constellations of smaller satellites, which can aggregate data from various sources, rather than relying on larger satellites. The numerous benefits of multi-spacecraft formation flying missions have led to an increasingly growing interest to explore its propulsion technologies, i.e., micro propulsion. Thoroughly characterising and studying the behaviour of the energetic materials is essential to ensure the safe and effective use of these micro-thrusters. Through the optimisation of micro-thruster design, the current research aims to generate outcomes that can be utilised to enhance the design and optimisation processes. Consequently, this will facilitate the widespread utilisation of micro-thrusters in multi-spacecraft missions. To optimise the performance of pyrotechnic micro-electromechanical systems, an efficient heater design, appropriate base material, channel dimensions, and electrical resistance must be considered based on available power and heat transfer requirements. A unique firing and monitoring test setup has been developed to produce a current-time plot for the device. Additionally, different micro-heater configurations, including spiral, loop, and meander types, were designed for the igniter. Experimental observations indicate that the spiral micro-heater design resulted in the lowest ignition delay and produced highly reliable combustion. The proposed microthruster design demonstrated efficient combustion and yielded promising results when tested with energetic materials such as Zirconium Potassium Perchlorate (ZPP) and Boron Potassium Perchlorate (BPN).

Access to space for small private companies requires to improve the ability to bring low-cost satellites into orbit. CubeSats offer a unique opportunity to meet these needs thanks to their reduced production times, the low manufacturing costs and ease of use. In order to be able to communicate with each other, exchange information and interact, it is necessary to place CubeSats in formation: in this context, miniature propulsion technologies, including chemical and electric propulsion, play a critical role in achieving mission requirements and maintaining satellites position. In this article, the feasibility of solid propellant micro rockets, fully integrated in an opposing array of printed thrust chambers is examined: each rocket can be fired together with the others or separately to modulate thrust. Theoretical and experimental results show that the microthruster, made of nylon and carbon fiber, have good mechanical and thermal resistance and simultaneously good performance is achieved. In particular, a microthruster with a diameter of 4 mm and a length of 6 mm, with 55 g of black powder propellant, achieves a thrust of about 3.5 N for about 7 ms.

With the development of micro-spacecraft technology, micro-nano satellites have the advantages of small size, low power consumption, short development cycle, formation networking, etc., and can complete many complex space tasks at a lower cost. Micro-nano satellites require a micropropulsion system with the capability of performing precise total impulse and thrust to execute maneuvers, such as attitude control, orbital transfer, and gravitation compensation. In contrast to other micropropulsion systems, solid propellant microthrusters (SPM) arrays based on micro-electromechanical system (MEMS) technology possess a simple structure and quick response, which is a potential micropropulsion system. In recent years, many research groups have done a lot of research on SPM arrays. In this paper, the latest progress of SPM arrays is summarized from the aspects of structure design, propellant selection, bonding technology, ignition unit type and micro-thrust test, and some suggestions for the future development direction are given.

Burning rate plays a crucial role in determining the performance of solid rocket motors (SRMs). In the traditional approach for solid propellant propulsion, technical activities regarding burning rates are developed at three different operational levels: (i) Strand burners or laboratory-scale devices in general; (ii) Small-scale motors (SSMs); And (iii) full-size or end-item rocket motors. While strand burners are extensively used for propellant development (formulation exploration, ingredients screening, performance verification, and production control) and relatively little is done experimentally at the full-size motor level (being large-scale experimentation too expensive and dangerous), a lot is usually carried out at SSM level to obtain burning rate information under motor operating conditions. In the introductory part of this work, burning rate fundamentals are recalled and burning rate measurement devices are quickly summarized. Then, a survey of subscale motors is conducted and several automated procedures to deduce burning rate from SSM testing are analyzed. Data reduction methods commonly used by leading European companies are based on the thickness-over-time (TOT) definition. Attention is dedicated to procedures used in Italy and France for quality control of the European space launchers (solid propellant boosters of Ariane family and core solid rocket motors of VEGA family). In addition, automated data reduction methods based on mass balance (MB) and often used in USA are investigated. Specific features and general trends of the tested industrial procedures are pointed out. Since for any tests the actual burning rates are unknown, results can only be compared based on the statistical quality of the deduced ballistic data. Mainly reproducibility, ease of application, and suitability for automated computer implementation are of interest to industrial users. The effects of test variability, input data quality, and data reduction methods on result reproducibility are discussed with reference to fire tests of the successful Ariane-5 solid boosters. The systematic analysis of industrial data conducted in this work suggests that improving the actual mix reproducibility and quality of experimental data is more important than perfecting the current data reduction methods. Moreover, the international trends suggest that the fundamental TOT procedures are being replaced by MB procedures or advanced TOT procedures with burning times evaluated using pressure integrals.

The ignition characteristics of nano-aluminum (nano-Al) in oxygen and steam environments were numerically studied in this work. A detailed kinetic mechanism of nano-Al combustion was developed, and the effects of initial reaction temperature, ignition pressure, the phase of reactant, and the ratio of O2 and H2O in the oxidizer on the oxidation performance of aluminum (Al) were analyzed in detail. Numerical results show that increasing the initial temperature promotes the ignition of liquid-phase Al, while the promotion is not significant for gas-phase Al ignition. The oxidation of liquid-phase Al is significantly slower than that of gas-phase Al, and the phase transition reaction of liquid-phase Al exhibits a typical endothermic process, which results in a temperature drop before ignition. The increase of initial reaction pressure can accelerate the consumption of both liquid-phase Al and gas-phase Al in the ignition process. The oxidizability of O2 is much larger than that of H2O, and the oxidation of Al becomes slower by adding H2O in the oxidizer. The rate of production (ROP) was performed to deeply realize the reaction pathways of Al consumption and main products formation. The reaction Al + O2 = AlO + O is the key reaction pathway in the Al-O2 ignition process, while the reaction Al + H2O = AlOH + O plays a more important role in the Al-H2O ignition process. In the all ignition cases, Al2O2 is a key intermediate species since it is the main precursor of gaseous Al2O3, and liquid-phase Al2O3 formed by the phase transition reaction of gaseous Al2O3 is the dominant final product.

The advent of various additive manufacturing technologies, such as 3D printing, has changed the structural design and preparation process of rocket fuels. In order to investigate the combustion properties of various common polymer materials that can be additively manufactured by fused deposition, the combustion tests of hybrid rocket fuels prepared by 3D printing were carried out. These materials include polylactic acid (PLA), wood-like polylactic acid (Wood), acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylate (ASA), copolymers of nylon 6 and nylon 6,6 (CoPA), polycarbonate-polybutylene terephthalate (PC-PBT), flame retardant polycarbonate (PC-FR) and polyethylene terephthalateco-1,4-cylclohexylenedimethylene terephthalate (PETG). Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis was carried out on these materials, the printing effect of the fuel grains was observed by three-dimensional X-ray microscopy (µCT) and the combustion performance of these fuels in gaseous oxygen flow (GOX) was recorded by high-speed photography at a constant pressure of 1 MPa. The results show that ASA and ABS exhibit good printing results. The regression rates of PC-PBT, PETG, ABS, ASA, CoPA and PLA are 0.792 mm/s, 0.592 mm/s, 0.536 mm/s and 0.477 mm/s, 0.368 mm/s, 0.339 mm/s (AtGOX=220kg/(m2·s)), respectively.

For aerospace vehicles, notably missiles or satellites for attitude and divert control, impulsive thrusters are most desirable if they are quantized as exact instantaneous pulses available over and after extended periods of inactive storage. These thrusters operate for a few milliseconds (ms), typically between 10 ms to 100 ms duration. Compared to its liquid or gaseous counterpart, an impulsive thruster powered by solid propellants is a simple, and reliable solution. Therefore, they are suitable as reaction control systems and divert thrusters for satellite and unmanned aerial vehicle applications.A typical solid propellant would need an extremely thin web thickness for port burning arrangement due to its brief burn duration, which makes propellant manufacturing and its structural anchoring in motor challenging. A high burn rate and high-density propellant based on ammonium perchlorate, aluminum, and Teflon is processed to enable end-burning configuration thus solving the problems, simplifying propellant manufacturing, structural design and integration. It also permits stacking propellants for multi-pulse applications. The high burn rate (40 mm/s at 120 bar pressure) propellant is formulated and tested for ballistic performance evaluation in proof motor configuration, and evaluation of its advantages over conventional propellant. A case of identical design requirements with both double base propellant and high burn rate pressed propellant is compared, tested and evaluated to compare the relative performance merits. The volumetric load is increased from 47% to 82% due to the development and adoption of high burn rate propellant. The overall weight of the thruster is also reduced by 20%.

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.

This paper presents a plume divergence angle prediction model for ion thruster. Firstly, an analytical model using Gaussian distribution for single grid hole plume is proposed. The parameters of this single hole model are obtained from the particle simulation results of ion optics which utilizes the immersed finite element Particle-in-cell Monte Carlo collision (IFE-PIC-MCC) method. Then, by the extension of the single hole model, a three-dimensional plume model for the whole ion optics is proposed. This plume model can be used to predict the divergence angle of ion thruster plume. Finally, a numerical example with the simulation of a 217-hole ion optics is provided to demonstrate the features of the proposed method.

3,3‘,5,5‘-Tetranitro-4,4‘-bipyrazole monohydrate (TNBPz, 1⋅H2O) is an excellent precursor for the synthesis of new energetic materials (2–12). Several nitrogen-rich salts (e.g. guanidinium, aminoguanidinium, hydrazinium, ammonium and hydroxylammonium) were prepared from 1⋅H2O by neutralization reactions. In addition, the N-methylation and N-amination of compound TNBPz was investigated and is reported. All new synthesized energetic materials were fully characterized by NMR (1H, 13C, 14N, and 15N) spectroscopy, infrared spectroscopy, differential thermal analysis (DTA) and elemental analysis. Compounds 2, 4–8 and 10 were characterized with single crystal X-ray diffraction. The heats of formation for compounds 2, 4–6, 8, 11 and 12 were calculated using the atomization method based on CBS-4 M enthalpies. Several detonation parameters, such as detonation pressure, velocity and energy, were calculated by using the X-ray densities and the calculated standard molar enthalpies of formation. The sensitivities of all energetic materials toward external stimuli were tested according to the BAM standards. In addition, the toxicity toward vibrio fischeri bacteria of few energetic salts (3 and 4) is reported.

In order to discover of high-energy materials with characteristics that surpass modern benchmarks, it is necessary to study the widest range of potential structures. The design of energetic compounds using high-nitrogen cage scaffolds provides new opportunities. One of the promising representatives of polycyclic multinitragen cages is the hexaazaisowurtzitane, since the most powerful explosive CL-20 is based on it. In recent years, the synthesis of CL-20 analogues has been actively developed. This review presents progress in the synthesis, performance and study of the structure-property relationship for energetic polynitro hexaazaisowurtzitanes over the past decade.

Plasticizers are functional additives that have been widely utilized to enhance the mechanical properties and processing technology of explosive systems. However, due to the increasing demand for energetic formulations of explosives and propellants, traditional plasticizers are gradually being replaced by energetic plasticizers. Azido plasticizer, a type of energetic plasticizer, possesses excellent thermal stability and low glass transition temperature. However, the incorporation of a single azido group can lead to issues such as decreased oxygen balance and reduced density. In recent years, novel azido plasticizers containing various energetic groups have been developed. Among these, the introduction of a nitramine group into the azido plasticizer has shown significant improvements in oxygen balance, density, and sensitivity compatibility. This makes azidonitramine plasticizers a promising research direction in the development of energetic plasticizers. Despite the existence of approximately twenty different types of azidonitramine plasticizers over the past few decades, a comprehensive review of these compounds is lacking in the literature. Therefore, this paper provides an inductive review of the synthesis, application, and performance characterization of azidonitramine plasticizers with the aim of inspiring further research in this field.

The rheology of melt-cast explosives is vital for the fused deposition modeling (FDM) manufacturing process. To address this problem, the rheological behavior of 2,4,6-trinitrotoluene/1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (TNT/HMX) melt-cast explosives were systematically investigated by a rotational rheometer. The results indicated that the rheological behavior of TNT/HMX melt-cast explosives was strongly influenced by the solid content and temperature. Through the printing experiment, the range of printing parameters that can be applied to fabricate desired explosive grain structures was determined. Besides, the computational fluid dynamic (CFD) and Hagan-Poiseuille formula were used to explore and quantify the printable zone of 3D printing melt-cast explosives. This work could expand the application of 3D printing technology in the field of explosives, propellants, and projectile penetration.

4,4′-azobis(1,2,4-triazole) (Atrz) is an excellent thermally stable explosive that is widely used to synthesize high-energy nitrogen-rich compounds. However, current methods for synthesizing this compound are low-yield and exothermic. In order to overcome these limitations, in this study, a continuous method based on the use of continuous stirred tank reactor (CSTR) was used to prepare Atrz for the first time, and the optimal experimental conditions were obtained by single factor experimental method and orthogonal experimental method. The yield of Atrz increased from 20%-30% to 71.84%, and the purity reached 98.54%. The use of CSTR enables materials to be mixed efficiently, making the reaction process efficient and environmentally friendly. At the same time, this method has the advantages of simple reaction process, easy large-scale continuous production, and high yield.

The results of modeling the structure of compounds 2,4,7,9-tetranitrobenzo[c]cinnoline (1) and 1,2,3,4-tetrazino[5,6-f]pyridazino-1,2,3,4-tetrazine 1,3,7,9-tetra-N-oxides (2) containing a pyridazine core are presented. The structure in the gas phase was estimated by quantum chemistry methods (DFT, B3LYP), on the basis of which the Atom-Atom Potentials method was used to model crystal packings in 35 most common space symmetry groups, which made it possible to identify the optimal packings and structural classes corresponding to them. Some physicochemical properties of the compounds have been calculated. It has been determined that the compounds under consideration have a molecular-crystal density of 2 g/cm3 and a high enthalpy of formation, which indicates the prospects for their use as high-energy-density materials.

Photothermal dual-curing adhesive is not only required to realize the basic curing function, but also has the characteristics of rapid setting and strong curing, which possesses a vital role in the molding speed, stability and structure integrity for 3D-printed propellants and explosives. Herein, the acrylate hydroxyl terminated polybutadiene, as novel photothermal dual-curing binders, were designed and synthesized utilizing cationic ring opening polymerization and active monomer mechanism as the strategy of photothermal dual-curing reaction. The mechanical properties and thermal stability of the photothermal dual-curing elastomers were systematically investigated. The results suggested that the target MAHTPB(Acrylate hydroxy‑terminated polybutadiene)-based adhesives could be cured rapidly within 5 s under UV light irradiation and completely cured in 1.5 h under heating conditions. Specifically, the elastomer film formed by MAHTPB-based photothermal dual-curing has a tensile strength of 4.63 MPa and an elongation of 386%, which exhibits stronger mechanical properties than the elastomer film formed by single photo- or thermal-curing. As a result, the synthesized photothermally cured adhesives have performed 3D printing experiments and achieved relatively satisfactory printing effects. Our study aims to solve the problems of short photocuring time, slow curing rate and incomplete curing for traditional photocuring, which lays a solid foundation to achieve rapid prototyping and precise performance control in 3D printing of propellants and explosives.

To reduce the mechanical sensitivity of CL-20, this study is based on the surface modification of CL-20, and explores the effects of two preparation processes, the water solution-suspension method and the phase separation method, on the coating process of CL-20. Based on the structural characteristics of surfactants, a formulation was devised, using 2-cyanoethyltriethoxysilane (SCA2) as the surfactant and microcrystalline wax as the desensitizer. The samples underwent comprehensive characterization employing SEM, XPS, DSC, XRD, friction sensitivity testing, and impact sensitivity testing to evaluate both their structural composition and inherent properties. The results showed that the composite particles prepared using the phase separation method displayed a compact coating layer on CL-20 surfaces. Specifically, the composite particle CL-20@SCA2/Wax-P, which contained the surfactant, exhibited a thin and dense film on its surface. The proportion of -NO2 groups on the surface of the composite particles experienced a reduction of 13.12% compared with CL-20. The crystal form of CL-20 remained unchanged in four composite particles. The decomposition peak temperatures and activation energy of all four composite particles were decreased, resulting in reduced thermal stability. The critical friction sensitivity load for composite particles produced via the aqueous suspension method is 252 N, whereas for those prepared using the phase separation method, it elevates to 360 N. The characteristic drop height (H50) of composite particles prepared by the phase separation method increased significantly, 34 cm for CL-20/W-P composite particles and 55 cm for CL-20@SCA2/W-P composite particles, compared with the raw CL-20. These results suggest that the utilization of SCA2 effectively modified the surface of CL-20, and the composite particles prepared using the phase separation method demonstrated a considerable reduction in mechanical sensitivity.

Motivated by the excellent detonation performance of octanitrocubane, prismane is another potential backbone with high strain energy in energetic molecule design. In this work, we aim to screen out candidates of highly energetic molecules from the space of prismane derivatives. The high-throughput computation (HTC) is performed based on 200 molecules derived from the molecule space of 1503 prismane derivatives with four substituents. Based on the calculated results, the machine learning (ML) models of density, detonation velocity, detonation pressure, heat of formation and detonation heat are established, and thereby the performances of the remaining 1303 samples are predicted. It is found that the –NHNO2 group increases density, while both –NO2 and –C(NO2)3 groups promote detonation performances. Based on the detonation velocity and bond dissociation energy as criteria representing energy and molecular stability, four molecules were screened out with good detonation performance and acceptable thermal stability. This work demonstrates the efficiency of HTC and ML combined strategy for screening high-quality energetic molecules.

The rheological properties and isothermal curing kinetics of the GAP/AN/HMX propellant slurries were investigated by steady rheological measurements and isothermal rheological measurements, and subsequently, the rheological model and the curing kinetics equation of the slurries were constructed, respectively. The results indicate that the GAP/AN/HMX propellant slurries are Carreau–Yasuda fluids, and the apparent viscosity of the slurries gradually decreases with the increase in shear rate and temperature. The storage modulus and loss modulus of the slurries show an ''S'' growth with the curing reaction, and the higher temperature causes a significant reduction in the time required for complete curing of the slurries. The pot-lifes of the slurries at 55 °C, 60 °C and 65 °C are 52590 s, 19820 s, 18150 s, respectively, with a noticible decrease with increasing temperature. Furthermore, the curing reaction of the slurries is viewed as an autocatalytic reaction, and the corresponding curing degrees (αmax) at the maximum curing rate are 0.3481 (55 °C), 0.3536 (60 °C), and 0.4420 (65 °C), respectively.

To investigate the characteristics of rotating detonation waves fueled by liquid kerosene with increasing equivalence ratios, the experiments were performed through increasing the supply of liquid kerosene under three different mass flow rates of oxidizer. Various mode transitions were realized, including transition from unstable detonation to stable single-wave mode, transition from unstable detonation to stable double-wave mode and transition from double-wave mode to single-wave & double-wave hybrid mode. The results demonstrate that the increase of equivalence ratios leads to the improvement of mixture reactivity under lean-fuel limit, which enhances the propagation stability and pressure peak of rotating detonation waves, and then results in the transition from unstable detonation to a stable propagation mode. In addition, when the mass flow rate of oxidizer is approximately 1100 g/s, the transition from double-wave mode to single-wave & double-wave hybrid mode is observed by increasing the equivalence ratio from 0.6 to 0.93. It is concluded that the mutation of dynamic balance between the RDW and injection plenum caused by the increasing of equivalence ratio is one of the reasons inducing the mode transition. This work illustrates the feasibility of modulating the propagation mode in rotating detonation waves fueled by liquid kerosene, and promotes the application of rotating detonation engine.

This review discusses conventional flame retardants for polymers and the possibility of using endothermal materials as flame retardants. Halogen-based, phosphorus-based, inorganic compounds, and their combinations are generally used as flame retardants for polymeric materials. The mechanism of action involves the trapping of radicals in the gas phase, an endothermic dehydration reaction, the blocking of oxygen, and a heat insulation effect by char in the solid phase. We discuss the possibility of using low-molecular-weight organic (or inorganic) metal complexes, exhibiting unique endothermic phenomena, such as phase transitions and cold crystallization, as flame retardants or thermal stabilizers at lower temperatures. In addition, this review provides an outlook on state-of-the-art) polymer flame-retardant technology.

The Gurney velocity is an important performance parameter that characterizes the metal pushing capability of conventional chemical explosives. Herein, this study proposes a mathematical model that aims to provide a simple and effective means by which the Gurney velocity of pure and mixed CHNO-based explosives can be accurately determined using as input information the volumetric heat of detonation, the parameter psi (Ψ) and an adjustable parameter (λ) that accounts for the type of the explosive being studied. The new model proved adequate for evaluating the Gurney velocity of sensitive and insensitive explosives of military interest, including melt-castable and plastic-bonded explosives (PBXs) and showed superior predicting performance compared to benchmark models. It is believed that the Gurney velocity obtained by the new method along with the Gurney-type equations would be very helpful for ordnance engineers for calculating the peak fragment deployment velocity from various warhead geometries, including omnidirectional and directed energy warheads for use in various weapons systems.

Regioisomeric energetic materials displayed different properties and performances. Understanding the regioisomerism in energetic materials and how it impacts the properties of energetic materials could provide insights into their improvements and designs. The present study explored the electrostatic properties for two regioisomers of energetic material, 3,4-bis(3-fluorodinitromethylfuroxan-4-yl)furoxan (BFTF-1) and 3,4-bis(4-fluorodinitromethylfuroxan-3-yl)furoxan (BFTF-2), which differ in the orientations of N-oxides in the furoxan rings on both sides. The strengths for corresponding covalent bonds in both isomers appeared to be similar, while the intramolecular interactions were distinctively different due to regioisomerism. The proposed decomposition pathways predicted from quantum mechanics (QM) calculations showed that BFTF-1 and BFTF-2 shared similar decompositions of nitro moieties in fluorodinitromethyl groups and furoxan ring openings followed by CC bond breakage. Both isomers also displayed different furoxan ring opening involving neighboring groups due to regioisomerism. The reactive molecular dynamics simulations confirmed that NO2 would be the initial products for both isomers and the species of molecules in their final products are similar. The present study provided insights into understanding the regioisomerism affecting the thermal decompositions of isomeric energetic materials and laid the ground for further improvements and designs.

Excessive plasticizer migration to the insulation will have a serious impact on the safety of solid propellants. In this paper, the anti-migration EPDM insulation was prepared by introducing vinyl triethoxysilane functionalized GO (GS) as modifiers to prevent the migration of energetic plasticizers. The anti-migration performance at different temperatures was evaluated by immersion tests. The concentration of mixed plasticizers that migrated into the EPDM/GS-3 at 30 °C was decreased from 24.7% to 20.4% (17.4% decrease). The results confirmed that the introduction of GS prevented the migration of plasticizers to the EPDM insulation. The SEM results showed that GS was well-dispersed in the insulation, and there is strong interfacial interaction between GS and EPDM chains. Our research provided a new method to prepare EPDM insulation with excellent anti-migration performance.

The interaction between cis-2 bis(benzofuro)[60]fullerene derivative and NO dominated double gas molecule was studied at the 6–311G(d,p) basis set level by density functional theory B3LYP-D3 method. The geometric structures of six interaction systems were optimized, and the optimized configurations were analyzed by electronic properties, infrared chromatography and independent gradient model to reveal the essence of intermolecular interaction. The results shows that NONO2, NON2, NOCO, NOCO2 and NOHCN are co-adsorbed on the surface of the compound in physical form, and the binding energies are −77.62 kJ/mol, −24.24 kJ/mol, −27.43 kJ/mol, −39.28 kJ/mol and −36.29 kJ/mol, respectively. The van der Waals interaction between gas molecules makes the three molecular interaction system have synergistic adsorption or competitive adsorption effect. Among them, the synergistic effect of NONO2 co-adsorption system is the biggest, and there is a strong attraction between NO and NO2 molecules. Compared with the interaction system of single gas molecule with cis-2 bis(benzofuro) [60]fullerene derivative, the interaction intensity of double gas molecule with the derivative is significantly improved.

1,1-dinitro-2,2-diamino ethylene (FOX-7) is typically representative of low sensitivity and high energy compound. In this work, analogues of FOX-7 are screened using a combined method of high-throughput computation (HTC) and machine learning (ML). The molecules are generated with typical unsaturated hydrocarbons backbones and random combination of substituents -H, -NH2 and -NO2, then HTC is performed based on 200 sample molecules. ML models are established based on the HTC results, with detonation parameters predicted using the most accurate model of extreme gradient boosting (XGB). Finally, stability of the filtered high energy molecules are confirmed by quantum chemistry calculations, and besides FOX-7, 8 more energetic molecules with high energy as well as high stability (detonation velocity ≥ 8841.1 m/s, detonation pressure ≥ 34.6 GPa and stability parameter bond dissociation energy ≥ 201.7 kJ/mol) are achieved. This work has shown the efficiency of HTC and ML methods in searching new target molecules.

The two directly substituted pentazoles, N5NH2 and N5COOH, were designed to theoretically study the relationships between substituents, aromaticity and kinetic stability thereof. Analysis shows their kinetic stability order described by the energy separations between the highest occupied molecule orbital (HOMO) and the lowest unoccupied molecule orbital (LUMO), viz. HOMO-LUMO gap, is line with the aromaticity orders obtained from nucleus-independent chemical shift (NICS), harmonic oscillator measure of aromaticity (HOMA), Bird aromaticity index (I) and isochemical shielding surface (ICSS), which is N5NH2 > N5COOH. But this order is contrary to the heat stability order according to Ref [1] The inconsistency between heat stability and kinetic stability reveals the fact that stability of compounds is a complex character and different according to the compound property of the study. The consistency of kinetic stability order with the aromaticity orders described by NICS, NICSSZZ, HOMA, I and ICSS indicates these widely accepted methods for aromaticity estimating are reliable for the two given compounds. As for the effect on aromaticity of pentazole ring from substituent, electron-donating substituent have stronger effect than electron-withdrawing substituent.

1- and 2-Propargyl-tetrazole (1- and 2-PryTz) were synthesized by reaction of propargyl bromide with sodium tetrazolate and used as ligands in energetic coordination compounds (ECCs) and evaluated concerning their thermal and mechanical sensitivities. Furthermore, the two nitrogen-rich compounds 1-((1H-1,2,3-triazol-4-yl)methyl)-1H-tetrazole (TriMT, 3) and 1-((1-(2-(1H-tetrazol-1-yl)ethyl)-1H-1,2,3-triazol-4-yl)methyl)-1H-tetrazole (TriMTET, 4) were prepared. Both were characterized by IR spectroscopy, NMR measurements, and low-temperature X-Ray diffraction analysis. Due to the highly endothermic enthalpy of formation of the propargyl-tetrazole ligands, powerful, yet relatively safe to handle, laser-ignitable ECCs were obtained.