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The energy and stability properties of energetic materials are often contradictory to each other (e.g., high energy vs low thermal stability). There is no doubt that it is still challenging to explore the effective balance between energetic performance and molecular stability, especially for melt-castable materials. In this study, we selected the 4-methoxy-3,5-dinitropyrazole framework and a stable nitro group to design a new energetic melt-castable compound, namely 4-methoxy-3,5-dinitro-1-(nitromethyl)-1 H -pyrazole (MDNNMP). Compared with the N -methylation product DMDNP and the nitrato-substituted derivative MC-7, MDNNMP exhibits a better balanced performance, including good thermal stability (Td : 203.7 °C), detonation velocity (Dv : 8099 m s–1) and impact sensitivity (20 J). The favorable balanced performance of MDNNMP suggests that it is a suitable candidate as a high-performance melt-castable material. Additionally, compared with the nitratomethyl group, the nitromethyl group demonstrates superior advantages in performance regulation. [ABSTRACT FROM AUTHOR]

Most nanothermite compositions utilise Al as a fuel, due to its low cost, high reactivity and availability. Nevertheless, aluminothermites exhibit high ignition temperature and low active metal content. In this paper, the combustion behaviour of Ti/CuO and Ti/CuO/NC systems is discussed. The compositions were prepared with a wet-mixing/sonication process followed by an electrospray technique and were examined in terms of their mechanical and radiation sensitivity, energetic parameters and morphology. The results exhibited a strong correlation between equivalence ratio and energetic parameters. The performed tests showed the crucial impact the addiction of the chosen energetic binder on the morphology and performance of the compositions. The results of our experiments indicate the occurrence of a different combustion mechanism than the one observed for Al-based nanothermites. In our case, the combustion mechanism involves a limitation by the diffusion of the oxidising agent and its decomposition products into the reactive fuel core. [ABSTRACT FROM AUTHOR]

The microwave ignition holds potential in the ignition of weapons due to its simple structure, non-contact property, and simultaneous ignitions of large area. However, the long ignition delay time of the current ignition agents cannot meet the microwave weaponry advancements. To address the issues, a microwave sensitive oxide-CuFe 2 O 4 (CUFO) which was firstly discovered to be easily ignited by microwaves compared many ferrites, was coupled with Ti nanoparticles (n-Ti) to form Ti/CUFO microwave ignition agents by electrostatic spray granulation. The characterization of microwave ignition, volumetric combustion, burning rate and DSC were used to determine its ignition delay time and the energy release properties. It indicates that the microwave sensitivity, maximum peak pressure and pressure pressurization rate of Ti/CUFO first increases and then decreases with the promoting content of n-Ti. The Ti/CUFO at Φ = 3.5 exhibits the lowest ignition delay time by 79.24 ms compared to the 98.7 ms of n-Ti, meanwhile, its maximum peak pressure and pressurization rate reach the highest by 338.54 kPa and 8.57 kPa/ms, respectively. The DSC results indicate that Ti/CUFO exhibits much lower reaction peak temperature by 320–335 °C compared to 488 °C of n-Ti, which suggests Ti-CUFO reaction maybe much easier be activated. The dielectric loss of n-Ti and CUFO under strong electric field transfer the energy of microwaves to heat, reaching to its reaction temperature. The XPS and XRD results of CUFO after microwave radiation disclosing the crystal transition, formation of divalent iron and oxygen vacancies, as well as the released bright light under microwave radiation, suggest the thermal breakdown mechanism of CUFO. When Ti/CUFO exposes into microwaves, CUFO generates oxygen vacancies due to heat loss and n-Ti is dielectric heated, followed by the generated oxygen reacting with n-Ti, improving the combustion performance of n-Ti. This result provides new insight for the designing of microwave ignition. [Display omitted] [ABSTRACT FROM AUTHOR]

The heat-resistant energetic compounds with thermal decomposition temperature higher than 300°C reported in the past ten years from the aspects of molecular design, synthesis route and performance evaluation were briefly reviewed. From the perspective of molecular framework, these heat-resistant energetic molecules mainly include monocyclic, fused heterocy-clic, linked heterocyclic and ionic salts. Among them, the fused heterocyclic and linked heterocyclic are the basic characteris¬tics and main directions of the current development of heat-resistant energetic materials. Based on the summary and analysis of the structure and properties of energetic molecules, the construction of large conjugation and hydrogen bonding systems is an effective strategy to improve the thermal stability of molecules. The rational design and layout of conjugated fused heterocyclic and linked heterocyclic skeleton, the introduction of hydrogen bonding system and the further expansion of conjugated structures are expected to realize the construction of ultra-high heat-resistant energetic molecules. [ABSTRACT FROM AUTHOR]

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.

A study of the combustion processes of Ti/CuO and Ti/CuO/NC nanothermites prepared via electrospraying was conducted in this work. For this purpose, the compositions were thermally conditioned at 350, 550 and 750 °C, as selected based on our initial differential scanning calorimetry-thermogravimetry (DSC/TG) investigations. The tested compositions were analysed for chemical composition and morphology using SEM-EDS, Raman spectroscopy and XRD measurements. Additionally, the thermal behaviour and decomposition kinetics of compositions were explored by means of DSC/TG. The Kissinger and Ozawa methods were applied to the DSC curves to calculate the reaction activation energy. SEM-EDS analyses indicated that sintering accelerated with increasing equivalence ratio and there was a strong effect on the sintering process due to cellulose nitrate (NC) addition. The main combustion reaction was found to start at 420–450 °C, as confirmed by XRD and Raman study of samples annealed at 350 °C and 550 °C. Moreover, increasing the fuel content in the composition led to lower Ea, higher reaction heats and a more violent combustion process. Conversely, the addition of NC had an ambiguous effect on Ea. Finally, a multi-step combustion mechanism was proposed and is to some extent in line with the more general reactive sintering (RS) mechanism. However, unusual mass transfer was observed, i.e., to the fuel core, rather than the opposite, which is typically observed for Al-based nanothermites. [ABSTRACT FROM AUTHOR]

Modern energetic materials (EMs), e.g., nanothermite and NSTEX (Nanostructured Thermites and Explosive) compositions are attracting increasing research interest. In this work, we present the results of our investigation on the properties of a novel Ti/CuO nanothermite system doped with cellulose nitrate (NC) and 5-Nitro-1,2-dihydro-3H-1,2,4-triazin-3-one (NTO). In terms of safety parameters, the friction (40–>360 N), impact (40–>50 J) and laser irradiation sensitivity were determined for tested systems, which indicated tunable properties. The combustion velocity (up to 735 m/s), pressure parameters for combustion in closed vessel, thrust parameters and open-air combustion behaviour were measured. Moreover, in order to deeply study the impact of NTO on the combustion mechanism, SEM, DSC/TG and XRD analyses were conducted. The obtained results indicate that the Ti/CuO/NC/NTO system is extremely promising for future applications. [ABSTRACT FROM AUTHOR]

Nanothermites have found broad applications; however, due to being systems largely reacting in condensed phases, their performance is somewhat limited by heat and mass transfer. In order to alleviate this issue, nanothermites doped with gas-generating energetic materials have been developed. In this work, we present an investigation of a model Ti/CuO nanothermite doped by four classical energetic materials and investigate their properties and combustion performance. Mechanical and laser irradiation sensitivity, as well as ignition/explosion temperatures have been determined for the studied systems to establish their safety features. In terms of combustion performance, thrust force parameters and linear combustion velocity have been determined and the structure of the evolving flame front was recorded during open-air combustion experiments. The obtained results indicate that the developed doped nanothermite formulations are extremely promising materials for future applications. [ABSTRACT FROM AUTHOR]

Context: To explore the influence of the external electric field (EEF) on ε-CL-20. The molecular structure, frontier molecular orbitals (FMOs), global reactivity parameters (GRP), surface electrostatic potential, nitro charge, and UV–Vis spectra of ε-CL-20 under EEF were studied using density functional theory (DFT). The calculation results show that the electric field applied along N16-N24 has a significant effect on the structure of ε-CL-20. With an increase in the positive EEF, the bond length of the initiating bond decreases, and the bond order and bond dissociation energy increase, which increases the thermal stability of ε-CL-20 to a certain extent. In addition, with an increase in the positive EEF intensity, the LUMO migrates from both sides of the positive electric field to one side of the nitro group, and the HOMO migrates from the skeleton to the nitro group. It is worth noting that in the negative EEF, when the electric field strength changed from 0 to 0.016 a.u., the negative charge of the total nitro group gradually decreased. When the electric field strength becomes 0.02 a.u., the negative charge of the total nitro group suddenly increases, and ε-CL-20 is significantly polarized. When the electric field strength is sufficiently strong, the occupied and unoccupied orbitals of the ε-CL-20 molecule change, resulting in a change in the energy level difference between the occupied and unoccupied orbitals, which further excites the corresponding excited state, resulting in a new UV–Vis absorption peak. Methods: Based on the density functional theory (DFT), the structural optimization and energy calculation were carried out by using B3LYP/6–311 + G(d, p) and B3LYP/def2-TZVPP methods, respectively. After optimization convergence, vibration analysis was performed without imaginary frequencies to obtain stable configurations. Then the molecular structure, frontier molecular orbitals (FMOs), global reactivity parameters (GRP), surface electrostatic potential, nitro charge, and UV–Vis spectra were analyzed. [ABSTRACT FROM AUTHOR]

During the research process, it was found that compounds with the "565" ring structure exhibited excellent detonation performance, which led to further investigation. TIOP (4a,5,7a, 8-tetrahydro-4H-imidazolo [4,5-b][1,2,5] oxadiazolo [3,4-e] pyrazine-6 (7H) -ketone) energetic compound has been designed. This article uses TIOP as the precursor and designs 54 "TIOP-based energetic derivatives" by introducing energetic groups such as –ONO2, –NHNH2, and –NH2. Among these energetic compounds, their maximum density, maximum detonation velocity, and maximum detonation pressure can reach 2.09 g/cm (D6), 10.07 km/s (D4), and 46.58 GPa (D7). Comprehensive analysis shows that energetic compounds A7, D4, D7, and F7 can reach a good equilibrium among high energy and low sensitivity, and can be further studied as potential High Energy Density Compounds. Using Gaussian16 software and the Multiwfn 3.8 software package, the B3LYP method in density functional theory was used to optimize the structure of 54 derivatives, calculate their heat of formation, and further analyze the intermolecular interactions. [ABSTRACT FROM AUTHOR]

Context: The compounds of the "565" parent ring structure have received much attention from researchers because of their excellent detonation performance. In the present study, 81 derivatives were designed by introducing different substituents based on 6-dinitrophenyl-5,6,7,8-tetrahydro-4-imidazo[4,5-e]furazano[3,4-b] pyrazine (DIOP), which is a compound of the parent ring structure of 565, and the performance of these derivatives, such as the electronic structure, energy gap, heat of formation, and detonation performance, were investigated. Among these energy-containing derivatives, the density ranges from 1.70 to 2.17 g/cm3, the detonation velocity ranges from 8.01 to 10.26 km/s, and the detonation pressure ranges from 27.99 to 49.88 GPa. Through comprehensive analysis of several properties of DIOP derivatives, it was found that the oxygen balance of derivatives with the -ONO2 group was greater than zero and close to zero, while the oxygen balance of derivatives with other groups was almost all less than zero. Among them, G8 (D = 10.1 km/s, P = 47.72 GPa), H8 (D = 10.11 km/s, P = 47.92 GPa), and I8 (D = 10.26 km/s, P = 49.88 GPa) had higher detonation velocity and pressure among all derivatives, and their impact sensitivity was better than RDX. Therefore, three potential high-energy and less sensitive energy-containing derivatives, G8, H8, and I8, were screened out. The intramolecular interactions of the three derivatives were further analyzed, and it was found that there were intensive van der Waals interactions and significant spatial steric effects within the molecules, which had a positive effect on reducing the shock sensitivity of the compounds. Moreover, the three derivatives have a large degree of stacking, which leads to a high density. Methods: All calculations in this paper are performed using Gaussian16 based on density functional theory. Firstly, the structures of the derivatives were optimized at the level of B3LYP-D3/6-311G**, and then single-site energy calculations were carried out at the level of M06-2X-D3/def2-TZVPP, to reveal the effects of single substituents versus multiple substituents and isomerism on the properties of the DIOP-based energetic derivatives. Multiwfn was used to plot the density of states (DOS) of the derivatives and to calculate the molecular surface electrostatic potential at 0.001 e/Bohr3 electron density, 0.25 Bohr lattice spacing surface. [ABSTRACT FROM AUTHOR]

Crystalline frameworks represent a cutting‐edge frontier in material science, and recently, there has been a surge of interest in energetic crystalline frameworks. However, the well‐established porosity often leads to diminished output energy, necessitating a novel approach for performance enhancement. Thiol‐yne coupling, a versatile metal‐free click reaction, has been underutilized in crystalline frameworks. As a proof of concept, we herein demonstrate the potential of this approach by introducing the energy‐rich, size‐matched, and reductive 1,2‐dicarbadodecaborane‐1‐thiol (CB−SH) into an acetylene‐functionalized framework, Zn(AIm)2, via thiol‐yne click reaction. This innovative decoration strategy resulted in a remarkable 46.6 % increase in energy density, a six‐fold reduction in ignition delay time (4 ms) with red fuming nitric acid as the oxidizer, and impressive enhancement of stability. Density functional theory calculations were employed to elucidate the mechanism by which CB−SH promotes hypergolic ignition. The thiol‐yne click modification strategy presented here permits engineering of crystalline frameworks for the design of advanced energetic materials. [ABSTRACT FROM AUTHOR]

This study demonstrates, for the first time ever, the ability to grow, in an on‐command fashion, porosity within a granular composite energetic material to effect a change in energy output rate. Specifically, the study investigates the change in burning rates of ammonium perchlorate composite propellants as a result of porosity created in situ via microwave field‐driven volatilization of the low boiling point binder additive, ethylene glycol. Theoretical mass densities were measured before and after microwave irradiation finding that the maximum observed %TMD change for tested propellants is 6 %. Propellants were burned at 1.72 MPa to 6.89 MPa pressures, finding that for all propellants, microwave irradiation produced a change in ballistic characteristics. Most propellant formulations demonstrate acceptable burning rate parameters for use within rocket motors; some exhibited a large change in their pressure exponent as well as slope breaks attributed to the onset of convective burning, while microwave irradiation produced no change in burning rate or density in reference propellants without the additive. Microwave heating simulation results are presented to gain insight into the thermal environment of the propellant during microwave irradiation. These results provide valuable insight into propellant formulations that can have their burning rates (and thus the thrust profile for motor grains) altered after casting via microwave irradiation. [ABSTRACT FROM AUTHOR]

This study addresses the issue of quality consistency in the extrusion process of energetic materials using multi-channel dies. To improve the extrusion efficiency of single-base energetic materials, a multi-channel die approach is utilized to yield more products in one extrusion. However, this method may compromise quality consistency during the process. Consequently, the finite element method (FEM) was employed for dynamics simulation of the extrusion process in the multi-channel die and further analysed the impact of critical parameters, such as extrusion speed and channel position, on product quality consistency. A strong linear relationship between flow parameters and d c , the average distance from each channel to the center of the die outlet plane, was reveal from simulation results. An optimization method based on channel distribution was proposed, and the product quality consistency ratio was calculated by averaging the shape consistency ratio, surface quality consistency ratio, and density consistency ratio. Simulation results indicate that this method effectively improves product quality consistency without significantly compromising extrusion efficiency. However, while increasing piston speed can also enhance product quality consistency, it will raise the extrusion pressure, thus increasing the risk of energetic material burning. Overall, this research provides new theoretical underpinnings and practical methods for optimizing the extrusion process of energetic materials. The basic theory, formula, algorithm, and simulation will be presented to validate the correctness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Three 4-(1H-tetrazole-5-yl-amino)-1,2,4,5-tetrazine-1-one (TATzO) metal salts, K2(TATzO)(H2O) (1) and Mg(TATzO)(H2O)6·2H2O (2) and Sr(TATzO)(H2O)4 (3), were synthesized and characterized using Fourier transform infrared (FTIR), elemental analysis, single-crystal X-ray diffraction, and powder X-ray diffraction patterns. The crystal structure and hydrogen bonding interactions have been analyzed. It turns out that 1 and 3 crystallize into a three-dimensional topological network and have strong π–π stacking and hydrogen bonding interactions. Furthermore, the geometric optimization of 1–3 was performed using B3LYP-D3/def2svp in Gaussian 16 software package and then analyzed by reduced density gradient. The thermal behavior was conducted using differential scanning calorimetry and thermogravimetric (TG). The decomposition temperature of the three complexes exceeds 250 °C, much higher than that of TATzO (230 °C). The thermal decomposition products of 1 were further studied using thermogravimetric-Fourier transform infrared-mass spectrometry (TG/FTIR/MS). The impact sensitivity test indicated that making complexes can help decrease the sensitivity of the original energetic ligand. [ABSTRACT FROM AUTHOR]

Context: The influence of external electric fields (EEFs) on chemical substances has always been a hot topic in the field of theoretical chemistry research. 2,6-Diamino-3,5-dinitropyrazine-1-oxide (LLM-105) is an energetic material with excellent comprehensive properties and enormous potential for application. This article explores the molecular structure, electronic structure, energy change, frontier molecular orbitals (FMOs) and density of states (DOS), UV–Vis spectra, and infrared spectra of LLM-105 under various electric field conditions. The results indicate that negative EEF can improve the stability of LLM-105, reflected in the initiation of changes in bond length and HOMO-LOMO gap. EEF has a significant impact on the electronic structure of LLM-105. The polarization of the electronic structure brings about a change in total energy, which is reflected in the analysis of energy changes. In addition, the external electric field will cause the frequency of the infrared spectra and the UV–Vis spectra to have different degrees of blue shift. The results of the analysis are helpful to understand the changes of energetic materials under the applied electric field. Methods: Based on the density functional theory (DFT), the structural optimization and energy calculation were carried out by using B3LYP/6-311G(d, p) and B3LYP/def2-TZVPP methods, respectively. After optimization convergence, vibration analysis was performed without imaginary frequencies to obtain stable configurations. Then, the molecular structure, electronic structure, energy changes, molecular orbital and density of states, UV–Vis spectra, and infrared spectra were analyzed. [ABSTRACT FROM AUTHOR]

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.

A novel ternary energetic cocrystal composed of 3,4-diamino-furazan (DAF), 3,4-dinitropyrazole (DNP), and H2O in a 1:1:1 stoichiometry with low impact sensitivity is reported. This cocrystal has a predicted detonation velocity higher than DAF and TNT. Preliminary attempts are reported to obtain the even more energetic cocrystals DAF/DNP and DAF/DNP/H2O22 For the latter, an original approach based on the urea/H2O2 cocrystal as a source of H2O2 is described. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The magnesium oxalate (MgC2O4) cathode material was synthesized via a dissolution route. This material exhibited higher electrochemical performance in Mg2+/Li+ hybrid ion batteries (MLIBs) compared with magnesium ion rechargeable batteries (MIBs) that were prepared. In MLIBs, this material showed a discharge capacity of 292, 226, 186, 134, 99, 71, and 32 mAh g−1 after 65 cycles at 2, 10, 20, 50, 100, 200, and 400 mA g−1, respectively. Then, the MgC2O4 material has the potential to be applied as a cathode in energy storage and conversion devices, such as MLIBs. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Most nanothermite compositions utilise Al as a fuel, due to its low cost, high reactivity and availability. Nevertheless, aluminothermites exhibit high ignition temperature and low active metal content. In this paper, the combustion behaviour of Ti/CuO and Ti/CuO/NC systems is discussed. The compositions were prepared with a wet-mixing/sonication process followed by an electrospray technique and were examined in terms of their mechanical and radiation sensitivity, energetic parameters and morphology. The results exhibited a strong correlation between equivalence ratio and energetic parameters. The performed tests showed the crucial impact the addiction of the chosen energetic binder on the morphology and performance of the compositions. The results of our experiments indicate the occurrence of a different combustion mechanism than the one observed for Al-based nanothermites. In our case, the combustion mechanism involves a limitation by the diffusion of the oxidising agent and its decomposition products into the reactive fuel core.

A study of the combustion processes of Ti/CuO and Ti/CuO/NC nanothermites prepared via electrospraying was conducted in this work. For this purpose, the compositions were thermally conditioned at 350, 550 and 750 °C, as selected based on our initial differential scanning calorimetry-thermogravimetry (DSC/TG) investigations. The tested compositions were analysed for chemical composition and morphology using SEM-EDS, Raman spectroscopy and XRD measurements. Additionally, the thermal behaviour and decomposition kinetics of compositions were explored by means of DSC/TG. The Kissinger and Ozawa methods were applied to the DSC curves to calculate the reaction activation energy. SEM-EDS analyses indicated that sintering accelerated with increasing equivalence ratio and there was a strong effect on the sintering process due to cellulose nitrate (NC) addition. The main combustion reaction was found to start at 420–450 °C, as confirmed by XRD and Raman study of samples annealed at 350 °C and 550 °C. Moreover, increasing the fuel content in the composition led to lower Ea, higher reaction heats and a more violent combustion process. Conversely, the addition of NC had an ambiguous effect on Ea. Finally, a multi-step combustion mechanism was proposed and is to some extent in line with the more general reactive sintering (RS) mechanism. However, unusual mass transfer was observed, i.e., to the fuel core, rather than the opposite, which is typically observed for Al-based nanothermites.

Nanothermites have found broad applications; however, due to being systems largely reacting in condensed phases, their performance is somewhat limited by heat and mass transfer. In order to alleviate this issue, nanothermites doped with gas-generating energetic materials have been developed. In this work, we present an investigation of a model Ti/CuO nanothermite doped by four classical energetic materials and investigate their properties and combustion performance. Mechanical and laser irradiation sensitivity, as well as ignition/explosion temperatures have been determined for the studied systems to establish their safety features. In terms of combustion performance, thrust force parameters and linear combustion velocity have been determined and the structure of the evolving flame front was recorded during open-air combustion experiments. The obtained results indicate that the developed doped nanothermite formulations are extremely promising materials for future applications.

Modern energetic materials (EMs), e.g., nanothermite and NSTEX (Nanostructured Thermites and Explosive) compositions are attracting increasing research interest. In this work, we present the results of our investigation on the properties of a novel Ti/CuO nanothermite system doped with cellulose nitrate (NC) and 5-Nitro-1,2-dihydro-3H-1,2,4-triazin-3-one (NTO). In terms of safety parameters, the friction (40–>360 N), impact (40–>50 J) and laser irradiation sensitivity were determined for tested systems, which indicated tunable properties. The combustion velocity (up to 735 m/s), pressure parameters for combustion in closed vessel, thrust parameters and open-air combustion behaviour were measured. Moreover, in order to deeply study the impact of NTO on the combustion mechanism, SEM, DSC/TG and XRD analyses were conducted. The obtained results indicate that the Ti/CuO/NC/NTO system is extremely promising for future applications.

The thermal damage process of the energetic material sample D-RDX was simulated by the thermal accelerated aging test, and the physical and explosive properties of the thermally damaged D-RDX energetic material were measured. The results showed that the physical properties of D-RDX did not change significantly under the test conditions, but the impact safety was significantly different, and the safety of the thermally damaged D-RDX sample showed greater dispersion. [ABSTRACT FROM AUTHOR]

In this paper, the synthesis of 2,4,6-trinitrophenol from phenol was improved in the range of 0–65°C, and the yield was 79.4%. The effectiveness of the synthesis process was confirmed by Nuclear Magnetic Resonance, Fourier Transform Infrared Spectrometer, and Scanning Electron Microscope. The thermal stability of the product was further studied by differential scanning calorimetry and accelerating rate calorimeter. The kinetic model established by combining linear regression and nonlinear regression methods shows that the apparent activation energy of the energetic material synthesized under the green process is about 130 kJ/mol. [ABSTRACT FROM AUTHOR]

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using commercially available raw materials, novel pyrimidine-based energetic compounds were synthesized, namely N-(7-oxo-6,7-dihydro-[1,2,5]oxadiazolo[3,4-d]pyrimidin-5-yl)nitramide (1), 2,4,6-triamino-5-nitropyrimidin-1-ium nitrate (2), and 4,6-diamino-5-nitro-2-oxo-2,3-dihydropyrimidin-1-ium nitrate (3). They were fully characterized using NMR (1H and 13C), IR spectroscopy, and elemental analysis. The crystal structures of compounds 1 and 3 were determined using single-crystal X-ray diffraction. The decomposition temperatures of compounds 1–3 were measured to be 190.2 ​°C, 156.8 ​°C, and 234.6 ​°C, respectively. Their densities were tested to be 1.84, 1.85 ​g ​cm−3, and 1.81 ​g ​cm−3, respectively. They exhibited desirable insensitive properties, with impact sensitivity ≥15 ​J and friction sensitivity >360 ​N. In addition, the detonation performances of compounds 1–3 were calculated with detonation pressure of 26.9, 29.6 ​GPa, and 26.0 ​GPa, respectively; detonation velocity of 8089, 8644 ​m ​s−1, and 7996 ​m ​s−1, respectively). Simple synthetic processes and high performance make them potential candidates for low-sensitivity energetic materials.

ABSTRACT: The first attempt to use genetic function approximation (GFA) for prediction of aquatic toxicity of soluble energetic materials is reported in this paper. The prediction is based on the estimation of the luminescent bacteria Aliivibrio fischeri inhibition in water according to the recently reported experimental results. Thus, two quantitative structure-activity relationship (QSAR) models for 15 min and 30 min exposure were obtained, which include five and six essential descriptors, respectively. Most of them are so-called “fast descriptors” assuming there is no need for quantum-chemical calculations. The rest descriptors are obtained in terms of semi-empirical approach allowing the prediction to be rapidly complete. The developed QSAR models provide relatively high correlation coefficients, namely, R2 = 0.81 and 0.82 for 15 min and 30 min datasets, respectively. The experimental datasets included a number of values, which were presented ambiguously (< or > than certain values). Thus, these have not been included (13 for 15 min and 10 for 30 min datasets) in the training sets and used them as the corresponding test sets. As a result, the developed models accurately indicate what exactly the higher and lower values should be applied instead of ones presented with ambiguity. Thus, the results may be useful for predicting the aquatic toxicity of new nitrogen-rich energetic materials, both molecular and ionic, bearing nitro, nitramino, azido groups and other commonly used explosophores.

This study effectively synthesized N,N'-(diazene-1,2-diylbis(5-amino-[1,2,4]triazolo[1,5-a][1,3,5]triazine-2,7-diyl)) dinitramide (3) by using 3,5-diamino-1,2,4-triazole as a starting material combining hydrogen bonds (HBs) and strong π-π stacking interaction between layers. Moreover, two fused rings were linked by an azo group to expand the conjugated compound, resulting in a shorter interlayer distance. The new compound and its energetic salts (4–6) were fully characterized through elemental analysis, IR spectroscopy, 1H and 13C NMR spectroscopy, and thermal analysis. The heats of formation and detonation properties of these compounds were calculated using Gaussian 09 and EXPLO5, respectively. The calculated results show that compounds 3–6 have both low impact and friction sensitivities (IS ​> ​40 ​J; FS ​> ​360 ​N) and favorable densities and detonation properties (ρ: 1.81–1.96 ​g·cm−3; vD: 7965–8248 ​m·s−1; p: 24.9–31.4 ​GPa). Therefore, they are promising candidates for high-energy and insensitive explosives.

Research on the structural responses to thermal stimuli for crystalline energetic materials is crucial to their practical applications. DAP-4 is a metal-free molecular perovskite high-energetic material attracting increasing attentions on its application potential as heat-resistant explosive. In order to reveal its structural responses to thermal stimuli, herein we investigated the structural phase transitions and thermal expansion of DAP-4 by DSC, single-crystal X-ray diffraction, and variable-temperature capillary powder X-ray diffraction. The results show that DAP-4 undergoes two-step reversible phase transitions at 300.4/298.9 K and 548.4/547.7 K, respectively, which are caused by two-step order-disorder transition of the molecular components during a heating/cooling cycle. The axial and the volumetric expansion coefficients of DAP-4 are estimated based on the temperature-dependent cell parameters obtained by Pawley refinement in a large temperature range of 173–353 K, and they are close to those estimated for β-HMX. Notably, although a volume change of 0.77% occur in the near-room-temperature phase transition, all the crystalline phases of DAP-4 possess cubic structures with isotropic expansibility, rather than the commonly-observed anisotropic one in the most of known energetic crystals, which may be propitious to reduce the adverse effect of its volume change on the formulation design.

In this paper, we report a quantitative structure-property relationship (QSPR) model development for friction sensitivity prediction of nitramine energetic materials. The model is obtained by means of a sophisticated method, namely, genetic function approximation and consists of 10 descriptors. As a training set, we have applied 80 nitramine energetic materials of a few families, both molecular and salt-like. The corresponding test set included 30 compounds. As a result, we have obtained a good correlation with R2 = 0.90. Only two descriptors, the heat of formation and quadrupole components, need semi-empirical quantum-chemical calculations, while the rest ones are so-called “fast descriptors” meaning the relatively short time of the prediction. Using the obtained QSPR model along with our recent method for fast crude estimation of the detonation properties based on empirical formulas we have modified a few energetic salts in order to obtain materials with better friction sensitivity and detonation performance. This was mainly done by changing the constituting ions: thus, 10 nitramine energetic materials with improved characteristics were proposed.

Information self-destruction devices represent the last protective net available to realize information security. The self-destruction device proposed here can generate GPa-level detonation waves through the explosion of energetic materials and these waves can cause irreversible damage to information storage chips. A self-destruction model consisting of three types of nichrome (Ni-Cr) bridge initiators with copper azide explosive elements was first established. The output energy of the self-destruction device and the electrical explosion delay time were obtained using an electrical explosion test system. The relationships between the different copper azide dosages and the assembly gap between the explosive and the target chip with the detonation wave pressure were obtained using LS-DYNA software. The detonation wave pressure can reach 3.4 GPa when the dosage is 0.4 mg and the assembly gap is 0.1 mm, and this pressure can cause damage to the target chip. The response time of the energetic micro self-destruction device was subsequently measured to be 23.65 μs using an optical probe. In summary, the micro-self-destruction device proposed in this paper offers advantages that include low structural size, fast self-destruction response times, and high energy-conversion ability, and it has strong application prospects in the information security protection field. [ABSTRACT FROM AUTHOR]

In this review we detail the expansion of laser-induced shock waves into the air following nanosecond-pulsed laser ablation of energetic materials for comparison of the microsecond-timescale energy release among different samples; subsequent self-sustained combustion reactions provide information about the millisecond-timescale energy release. This technique is called laser-induced air shock from energetic materials (LASEM). A detailed description of the processes involved in LASEM is presented, along with the experimental conditions for successfully differentiating similar energetic materials. The influence of material properties and sample preparation, laser properties, high-speed imaging parameters, and data fitting methodology on the characteristic laser-induced shock velocities is reviewed with relevant examples. Related work by other groups is also discussed, demonstrating the increasing usage of laser-induced plasmas and their subsequent effects for energetic material characterization on a laboratory scale. We provide examples of recent capability upgrades. Finally, we enumerate the open questions relating to LASEM experimental results and their relationship to detonation chemistry. [ABSTRACT FROM AUTHOR]

Time‐resolved Raman spectroscopy has been used to simultaneously measure temperature and pressure in the TATB‐based plastic‐bonded explosive (PBX) sample under laser‐driven shock wave. Temperature and pressure have been confirmed according to the ratio of anti‐Stokes to Stokes Raman intensities and the variation of the center wavenumber of the Raman peak under shock loading, respectively. The location of the shock front has been determined according to the ratio of the spectral height of the shifted Raman peak under shock loading to that of the original Raman peak, and the velocity of the shock front has been estimated by linear fit for the locations of the shock front versus delay times. Therefore, the shock propagation in this PBX sample is characterized according to the measured temperature, pressure, and shock velocity. In addition, the correlation between the pressure and the temperature under shock waves is established, and the pressure‐dependence temperature gradient is 10.06 ± 0.67 K/GPa. [ABSTRACT FROM AUTHOR]

Artificial intelligence (AI) is rapidly emerging as a enabling tool for solving complex materials design problems. This paper aims to review recent advances in AI‐driven materials‐by‐design and their applications to energetic materials (EM). Trained with data from numerical simulations and/or physical experiments, AI models can assimilate trends and patterns within the design parameter space, identify optimal material designs (micro‐morphologies, combinations of materials in composites, etc.), and point to designs with superior/targeted property and performance metrics. We review approaches focusing on such capabilities with respect to the three main stages of materials‐by‐design, namely representation learning of microstructure morphology (i. e., shape descriptors), structure‐property‐performance (S−P−P) linkage estimation, and optimization/design exploration. We leave out "process" as much work remains to be done to establish the connectivity between process and structure. We provide a perspective view of these methods in terms of their potential, practicality, and efficacy towards the realization of materials‐by‐design. Specifically, methods in the literature are evaluated in terms of their capacity to learn from a small/limited number of data, computational complexity, generalizability/scalability to other material species and operating conditions, interpretability of the model predictions, and the burden of supervision/data annotation. Finally, we suggest a few promising future research directions for EM materials‐by‐design, such as meta‐learning, active learning, Bayesian learning, and semi‐/weakly‐supervised learning, to bridge the gap between machine learning research and EM research. [ABSTRACT FROM AUTHOR]

Sequential ultra-small-angle and small-angle and X-ray scattering (USAXS and SAXS) measurements of hierarchical microstructure of a common energetic material, the high explosive 2,4,6-Triamino-1,3,5-trinitrobenzene (TATB), were performed to follow the microstructure evolution upon applied pressure. The pellets were prepared by two different routes—die pressed from a nanoparticle form and a nano-network form of TATB powder. The derived structural parameters, such as void size, porosity, and the interface area, reflected the response of TATB under compaction. Three populations of voids were observed in the probed q range from 0.007 to 7 nm−1. The inter-granular voids with size larger than 50 nm were sensitive to low pressures and had a smooth interface with the TATB matrix. The inter-granular voids with size of ~10 nm exhibited a less volume-filling ratio at high pressures (>15 kN) as indicated by a decrease of the volume fractal exponent. The response of these structural parameters to external pressures implied that the main densification mechanisms under die compaction were the flow, fracture, and plastic deformation of the TATB granules. Compared to the nanoparticle TATB, the applied pressure strongly influenced the nano-network TATB due to its more uniform structure. The findings and research methods of this work provide insights into the structural evolution of TATB during densification. [ABSTRACT FROM AUTHOR]

Nanoscale composite energetic materials (CEMs) based on oxidizer and fuel have potential advantages in energy adjustment and regulation through oxygen balance (OB) change. The micro- and nanosized fibers based on nano nitrocellulose (NC)-ammonium dinitramide (ADN) were prepared by the electrospinning technique, and the morphology, thermal stability, combustion behaviors, and mechanical sensitivity of the fibers were characterized by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), gas pressure measurement of thermostatic decomposition, laser ignition, and sensitivity tests. The results showed that the prepared fibers with fluffy 3D macrostructure were constructed by the overlap of micro/nanofibers with the energetic particles embedded in the NC matrix. The first exothermic peak temperature (Tp) of the samples containing ADN decreased by 10.1 °C at most compared to that of ADN, and the pressure rise time of all the samples containing ADN moved forward compared to that of the sample containing NC only. Furthermore, ADN can decrease the ignition delay time of NC-based fibers under atmosphere at room temperature from 33 ms to 9 ms and can enhance the burning intensity of NC-based fibers under normal pressure. In addition, compared to the single high explosive CL-20 or RDX, the mechanical sensitivities of the composite materials containing high explosive CL-20 or RDX were much decreased. The positive oxygen balance of ADN and the intensive interactions between ADN and NC can reduce the ignition delay time and promote the burning reaction intensity of NC-based composite fibers, while the mechanical sensitivities of composite fibers could be improved. [ABSTRACT FROM AUTHOR]

The shock initiation randomness problem of energetic materials (SIREM) is an important problem in the research field of energetic material safety. With the purposes of solving SIREM on a macroscopic scale and obtaining the statistics, such as the initiation probabilities of energetic materials and the statistical characteristics of the detonation pressure, this paper considers the effect of the randomness of the parameters of the Lee–Tarver equation of reaction rate and the JWL equation of state of energetic materials and the randomness of load intensity parameters—such as fragment shock velocity—on the randomness of the shock initiations of energetic materials. It then decomposes SIREM into an initiation probability problem (IP) and a detonation pressure randomness problem (DPR). Further, with the Back Propagation Neural Networks optimized by the Genetic Algorithm (GABPNN) as the surrogate models of the numerical models of two-phase reactive flow, this paper proposes the approach of solving IP and DPR in turn, adopting Monte Carlo Simulations, which use the calculations of GABPNNs as repeated sampling tests (GABP-MCSs). Finally, by taking the shock initiation randomness problem of Composition B as an applied example, this paper adopts GABP-MCS under the randomness conditions that the means of fragment shock velocities are 1050 m/s and 1000 m/s and that the coefficients of variation (CVs) of BRVs are 0.005, 0.01, 0.015, and 0.02 in order to obtain the initiation probabilities of Composition B and the statistical characteristics, such as the means and CVs of the detonation pressure. It further observes the variation tendencies that these statistics show under various randomness conditions, so as to prove the effectiveness of GABP-MCS in solving SIREM. Therefore, this paper investigates SIREM on a macroscopic scale and proposes a universal technique for solving SIREM by GABP-MCS, in the hope of shedding some light on the SIREM study. [ABSTRACT FROM AUTHOR]

The crystal structure has a great influence on mechanical sensitivity and detonation performance of energetic materials. An efficient microfluidic platform was applied for size, morphology, and crystallinity controllable preparation of ultrafine HMX. The microfluidic platform has good mixing performance, quick response, and less reagent consumption. The ultrafine γ-HMX was first prepared at room temperature by microfluidic strategy, and the crystal type can be controlled accurately by adjusting the process parameters. With the increase in flow ratio, the particle size decreases gradually, and the crystal type changed from β-HMX to γ-HMX. Thermal behavior of ultrafine HMX shows that γ→δ is easier than β→δ, and the phase stability of HMX is β > γ > δ. Furthermore, the ultrafine β-HMX has higher thermal stability and energy release efficiency than that of raw HMX. The ultrafine HMX prepared by microfluidic not only has uniform morphology and narrow particle size distribution, but also exhibits high density and low sensitivity. This study provides a safe, facile, and efficient way of controlling particle size, morphology, and crystallinity of ultrafine HMX. [ABSTRACT FROM AUTHOR]

The compatibility of erythritol tetranitrate (ETN) with RDX, CL-20, PETN, TNT, HMX, Picric acid was studied by differential scanning calorimetry (DSC). Two methods for judging the compatibility level of ETN and conventional explosives are introduced. One method is using the decomposition temperature (Tp) and apparent activation energy (Eo) of the thermal decomposition curve at the heating rate, the compatibility levels of the two explosives can be obtained. The results show that ETN with RDX have good compatibility, level 1; ETN with HMX, CL-20 are fair compatibility, level 2; ETN with PETN, TNT and Picric acid are poor compatibility, level 3. Another method is when apparent activation energy (Eo) is not added, the compatibility levels are different when just used the decomposition temperature (Tp). [ABSTRACT FROM AUTHOR]

To explore particulate movement near the plasma of chemical explosions, rugged tracer particles were placed within and on the exterior of metal charges and electrically detonated. The particles were collected on/in the porous walls of plastic cylinders at diameters that correlated to the plasma width during different phases of the explosion. The particles' positions were determined by Boolean logic analysis of their luminescent intensity. The cylinders which caught particles from the initial phases of the explosion retained placement information, while wider cylinders showed uniform mixing. These results/analysis methodology can help improve the understanding of particulate mixing in harsh environments. [ABSTRACT FROM AUTHOR]

A critical survey concerning biocidal energetics is proposed according to a classification depending on their chemical structure. The need of optimizing the performances of such compounds is an important target for the inertization of biological weapons, requiring a synergy between the thermal effects of combustion/detonation with the biocidal effects of reaction products released into the environment. The main physicochemical aspects related to the synthesis technique, the thermodynamic variables and the antimicrobial activity have been discussed and compared. In particular, different kinds of biocides have been taken into account, with particular attention to the role of iodine as one of the most promising and eco-friendly chemical species to this purpose, in line with the paradigms of environmental protection and the rational utilization of chemicals. Furthermore, the protocols adopted to assess the effectiveness of biocidal agents have been thoroughly examined according to the recent studies proposed by some of the most reputable research groups in the field. Finally, some insights for future investigations are proposed. [ABSTRACT FROM AUTHOR]

Energetic materials (EMs) are the core materials of weapons and equipment. Achieving precise molecular design and efficient green synthesis of EMs has long been one of the primary concerns of researchers around the world. Traditionally, advanced materials were discovered through a trial-and-error processes, which required long research and development (R&D) cycles and high costs. In recent years, the machine learning (ML) method has matured into a tool that compliments and aids experimental studies for predicting and designing advanced EMs. This paper reviews the critical process of ML methods to discover and predict EMs, including data preparation, feature extraction, model construction, and model performance evaluation. The main ideas and basic steps of applying ML methods are analyzed and outlined. The state-of-the-art research about ML applications in property prediction and inverse material design of EMs is further summarized. Finally, the existing challenges and the strategies for coping with challenges in the further applications of the ML methods are proposed. [ABSTRACT FROM AUTHOR]