Potential Energetic Materials Research Articles

Thermal properties and decomposition of perovskite energetic materials (C6H14N2) NH4 (ClO4)3

(C6N2H14) NH4 (ClO4)3 (DAP-4) have attracted an increasing focus recently as an ammoniumperchlorate-based molecular perovskite energetic material with outstanding features. Microscopy, variable temperature X-ray diffraction, in situ infrared spectroscopy, differential scanning calorimetry-thermogravimetry simultaneous thermal analysis coupled with infrared spectroscopy and mass spectrometry (DSC-TG/FTIR/MS) techniques were used to systematically investigate DAP-4 thermal properties from -40 °C to 550 °C. The results revealed that DAP-4 have two solid-solid crystallization phase transitions with a non-characteristic melting process. The generated activation energies of HCN, CO, CH2NH2, CO2 and NO2 gas products are all lower than the macroscopic decomposition's of DAP-4. This finding strongly proves that DAP-4 is easy to form these gas products during thermal stimulus. The two stages decomposition mechanism accompanying a large of CH2NH2 and NH2C2H4 gases and kinetic model of DAP-4 were proposed under the condition of high-purity argon gas. This study provides new insight into the in-depth and accurate description thermal decomposition mechanism of DAP-4 as a potential energetic material.

Theoretical investigation of potential energetic material CL-20/TNBP co-crystal explosive based on molecular dynamics method.

The exploration of CL-20 eutectic has been a subject of fervent interest within the realm of high-energy material modification. Through the utilization of density functional and molecular dynamics methods, an investigation into the characteristics of hexanitrohexaazaisowurtzitane (CL-20)/4,4',5,5'-tetranitro-2H,2'H-3,3'-bipyrazole (TNBP)within the molar ratio range of 4:1-1:4 was conducted. This inquiry encompassed the scrutiny of molecular interaction pathways, attachment force, initiating molecular distance, unified energy concentration, and physical characteristics. Furthermore, the EXPLO-5 was harnessed to prognosticate the explosion features and byproducts of unadulterated CL-20, TNBP, and CL-20/TNBP frameworks. The findings delineate a substantial differentiation in the electrostatic charge distribution on the surface between CL-20 and TNBP particles, signifying the preeminence of intermolecular interactions between disparate entities over those within similar entities, thus intimating the plausibility of the eutectic constitution. Remarkably, the identification of maximal attachment force at a molar ratio of 1:1 suggests the heightened likelihood of eutectic formation, propelled primarily by electrostatic and van der Waals forces. The resultant eutectic explosive evinces intermediate reactivity and exemplary mechanical attributes. Moreover, the detonation achievement of the eutectic with a molar proportion of 1:1 straddles that of CL-20 and TNBP, representing a new type of insensitive high-energy material. The testing method employs the Materials Studio software and utilizes the molecular dynamics (MD) method to predict the properties of CL-20/TNBP cocrystals with different ratios and crystal faces. The MD simulation time step is set to 1fs, and the total MD simulation time is 2ns. An isothermal-isobaric (NPT) ensemble is used for the 2ns MD simulation. The COMPASS force field is employed, with the temperature set to 295K. The prediction of detonation characteristics and products is conducted using the EXPLO-5 software.

Theoretical study of potential energetic material CL-20/DNAN eutectic explosive based on molecular dynamics method.

The exploration of CL-20 eutectic has been a subject of fervent interest within the realm of high-energy material modification. Through the utilization of density functional and molecular dynamics methods, an investigation into the characteristics of hexanitrohexaazaisowurtzitane (CL-20)/2,4-dinitroanisole (DNAN) within the molar ratio range of 9:1-1:9 was conducted. This inquiry encompassed the scrutiny of molecular interaction pathway, attachment force, initiating molecular distance, unified energy concentration, and physical characteristics. Furthermore, EXPLO-5 was harnessed to prognosticate the explosion features and byproducts of unadulterated CL-20, DNAN, and CL-20/DNAN frameworks. The findings delineate a substantial differentiation in the electrostatic charge distribution on the surface between CL-20 and DNAN particles, signifying the preeminence of intermolecular interactions between disparate entities over those within similar entities, thus intimating the plausibility of eutectic constitution. Remarkably, the identification of maximal attachment force at a molar ratio of 4:6 suggests the heightened likelihood of eutectic formation, propelled primarily by electrostatic and van der Waals forces. The resultant eutectic explosive evinces intermediate reactivity and exemplary mechanical attributes. Moreover, the detonation achievement of the eutectic with a molar proportion of 4:6 straddles that of CL-20 and DNAN, representing a new type of insensitive high-energy material. The testing method employs the Materials Studio software and utilizes the molecular dynamics (MD) method to predict the properties of CL-20/DNAN co-crystals with different ratios and crystal faces. The MD simulation time step is set to 1 fs, and the total MD simulation time is 2 ns. An isothermal-isobaric (NPT) ensemble is used for the 2-ns MD simulation. The COMPASS force field is employed, with the temperature set to 295 K. The prediction of detonation characteristics and products is conducted using the EXPLO-5 software.

Azo Pyrazole Carboxylic Derivatives for Potential Energetic Materials

Azo Pyrazole Carboxylic Derivatives for Potential Energetic Materials

DFT investigation on detonation properties and sensitivities of bridged triazolo[4,5‐d]pyridazine based energetic materials

AbstractA series of bridged triazolo[4,5‐d]pyridazine based energetic materials were optimized at B3LYP/6‐311G(d, p) level of density functional theory (DFT), and their detonation properties and sensitivities were calculated. The results show that the NN bridge/N3 group were beneficial to improve values of heats of formation while NN bridge/C(NO2)3 group can improve detonation properties remarkably. In view of the sensitivities, compound F2 possesses the minimum values of impact sensitivity which reveals that NHNH bridge/C(NO2)3 group will decrease the stability of the designed compounds. Take both of detonation properties and sensitivities into consideration, compounds C8, E7, E8, F8 were screened as candidates of potential energetic materials since these compounds possess similar detonation properties and sensitivities values to those of RDX. All the calculated results were except to shine lights on the design and synthesis of novel high energy density materials.

4-Amino-3-Hydrazino-1,2,4-Triazolium 5-Nitrotetrazolate: A High-Density Energetic Materials

4-Amino-3-hydrazino-1,2,4-triazolium 5-nitrotetrazolate (AHT·NT): an energetic nitrogen-rich salt was preparedand fully characterized by1H,13C NMR, and IR spectroscopy, differential scanning calorimetry (DSC), andelemental analysis. AHT·NT crystallizes in the triclinic crystal system in Monoclinic crystal system P2 (1) /c group. By including two molecular moieties in the unit cell, the calculated density is 1.789 g·cm-3. There are extensive hydrogen bonding interactions between the cation and the anion form acomplex 3D network.The heat of formationwas calculated with the Gaussian 03suite of programs. AHT·NT exhibit promising detonation performances (pressure: 31.0 GPa; velocity:8831 m·s-1; EXPLO 5.05) that exceedthose of conventional TNT. Impactsensitivity was also determined byhammer tests and resulted at4.5 J. AHT·NT exhibit reasonablephysical properties, such as good thermal (Td = 164.9°C), and reasonable impact sensitivities, making this salt potential energetic material.

Thermal pyrolysis properties and security performance of molecular perovskite energetic crystal (C6N2H14) (NH4) (ClO4)3 (DAP-4)

DAP-4 (C6N2H14) (NH4) (ClO4)3 has been synthesized recently as an ammonium perchlorate-based molecular perovskite energetic material with higher stability and outstanding performances. In this study, rapid thermal cracking infrared spectroscopy is applied to study the thermal pyrolysis properties and combustion process of DAP-4. Under different temperatures and pressure with a heating rate of 1000℃·s-1, the gaseous products in the rapid pyrolysis process are mainly CO, CO2, H2CO, HCN, and HCl. Above 700ºC, the pressure affects the ratio of the gas products, but the temperature does not. Based on the relative ratio of the different gas products, a thermal pyrolysis mechanism was proposed. The heat of explosion (ΔHdet), enthalpy of combustion(ΔcHθ), and standard enthalpies of formation (ΔfHθ) are determined to be -2527.39kJ·mol-1, -2492.06kJ·mol-1 and -483.96kJ·mol-1, respectively. The self-catalytic heating time is 99.5min, the temperature at the initial detection point is 280.1 ℃, and the maximum temperature rise rate is 49.1 ℃·min-1. The thermal safety experimental results showed that DAP-4 has a relatively good security performance. This study provides new insight into the mechanism of pyrolysis of DAP-4 as a potential energetic material.

Functionalization of fused imidazole-oxadiazole, triazole-oxadiazole and tetrazole-oxadiazole skeletons: Search for stable and potential energetic materials

In this study, 21 energetic molecules were designed based on imidazo[2,1-b][1,3,4]oxadiazole, [1,2,4]triazolo[3,4-b][1,3,4]oxadiazole, and [1,3,4]oxadiazolo[3,2-d]tetrazole fused heterocyclic backbones by inserting NH2, N3, NO2, NHNO2, ONO2, CH(NO2)2, and C(NO2)3 functional groups. These compounds have high densities and excellent detonation performance. Among them, compounds with NO2, NHNO2, ONO2, CH(NO2)2, and C(NO2)3 substituents showed satisfactory detonation velocities (D > 8.70 km/s) and pressures (P > 35.2 GPa), which are equivalent to the performance of RDX and HMX. The analysis of energy gap (ΔE) in frontier molecular orbitals, free volume (ΔV) in a crystalline unit cell, maximum heat of detonation (Q), and percentage positive electrostatic potential reveal their moderate sensitivity. Combined with high nitrogen content, good density, energy content, and stability, imidazole-oxadiazole, triazole-oxadiazole, and tetrazole-oxadiazole [5 + 5] fused heterocyclic backbones will facilitate the preparation and development of new energetic materials.

Force field-inspired transformer network assisted crystal density prediction for energetic materials

Machine learning has great potential in predicting chemical information with greater precision than traditional methods. Graph neural networks (GNNs) have become increasingly popular in recent years, as they can automatically learn the features of the molecule from the graph, significantly reducing the time needed to find and build molecular descriptors. However, the application of machine learning to energetic materials property prediction is still in the initial stage due to insufficient data. In this work, we first curated a dataset of 12,072 compounds containing CHON elements, which are traditionally regarded as main composition elements of energetic materials, from the Cambridge Structural Database, then we implemented a refinement to our force field-inspired neural network (FFiNet), through the adoption of a Transformer encoder, resulting in force field-inspired Transformer network (FFiTrNet). After the improvement, our model outperforms other machine learning-based and GNNs-based models and shows its powerful predictive capabilities especially for high-density materials. Our model also shows its capability in predicting the crystal density of potential energetic materials dataset (i.e. Huang & Massa dataset), which will be helpful in practical high-throughput screening of energetic materials.

Synthesis and Crystal Structures of 4‐Methoxyphenyl‐ N‐phenylhydrazine‐1‐carbothioamide isomers and 2,2’‐(1,2,4,5‐tetrazine‐3,6‐diyl) bis (N‐phenylhydrazine‐1‐carbothioamide)

AbstractThe synthesis of several semithiocarbazides, relevant as a precursor material for the synthesis of the tetrazole azasydnone, a potential energetic material, was explored. In this work, the treatment of 4‐methoxy phenylhydrazine hydrochloride with phenyl isothiocyanate results in 2‐ and 1‐ isomers of (4‐methoxyphenyl)‐N‐phenylhydrazine‐1‐carbothioamide. Similar treatment of 3,6,–dihydrazino‐1,2,4,5‐tetrazine with phenyl isothiocyanate yielded 2,2’‐(1,2,4,5‐tetrazine‐3,6‐diyl) bis (N‐phenylhydrazine‐1‐carbothioamide). Crystallographic information for all novel compounds was obtained via single crystal X‐ray diffraction.

One-step synthesis of 6-amino-5-nitro-2-(trinitromethyl)-pyrimidin-4(3H)-one as potential energetic material

One-step synthesis of 6-amino-5-nitro-2-(trinitromethyl)-pyrimidin-4(3H)-one as potential energetic material

Thermal analysis study of ammonium nitrate in the presence of NiCuCr2O4 additive

Nickel-copper chromite (NiCuCr2O4) was synthesized by the co-precipitation method using sodium hydroxide as a precipitating agent. The composition of ammonium nitrate (AN):NiCuCr2O4 (mass ratio 98:2) was used for the comparative thermal analysis study. The results suggested that ammonium nitrate containing nickel-copper chromite (AN + NiCuCr2O4) can act as a potential energetic material to replace AN in energetic applications. The activation energy of AN + NiCuCr2O4 was decreased by 85.7 kJ mol−1 compared to pure AN along with a reduction in the peak decomposition temperature. The lower activation energy and low pre-exponential factor can fasten AN + NiCuCr2O4’s decomposition at a lower temperature.

Design and computational studies on energetic compounds composing bridged bis triazolo-triazine framework

Density functional theory was used to design a new series of bridged (directly connected, –CH = CH–, –CH2–, –CH2–CH2–, –O–, –NH–, –NH–NH–, –N=N–) energetic compounds based on bis[1,2,4] triazolo[4,3-b:4′,3′-d][1,2,4]triazine (bis triazolo-triazine) backbone with explosophoric functionalities (–NO2, –NHNO2, and –NH2 groups). Using the predicted densities and heats of formation in Kamlet-Jacobs equations, detonation performance was assessed, which specify that the –NO2 group is a suitable explosophore for enhancing performance. Comparing the influence of different linkages on detonation properties it is observed that –O–, –NH–, and –N=N– linkages are more beneficial for enhancing performance. The bond dissociation energy (BDE), heat of detonation (Q), balance parameter (ν), and impact sensitivity (h50) values were utilized to determine stability and sensitivity. Some designed bis triazolo-triazine molecules have high densities (>1.85 g/cm3) and good detonation performance (VOD > 8.40 km/s and DP > 32 GPa), may be considered as the potential energetic material candidates.

Tricyclic compounds with 1,4,2,5-dioxadiazine bridged triazoles and pyrazoles as potential energetic materials

In this study, two energetic molecules with 1,4,2,5-dioxadiazine as a bridge were created by adding triazoles and pyrazoles to the oxazine skeleton. The structural characteristics, thermal behavior, and explosive properties of the obtained compounds 3,6-bis(1-nitro-1H-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (4a) and 3,6-bis(1-nitro-1H-pyrazol-3-yl)-1,4,2,5-dioxadiazine (4b) were investigated using experimental and theoretical techniques. To further elucidate the structure-property relationship, this study conducted calculations and analyses of quantum chemistry, such as the Hirshfeld surface analysis, the electrostatic potential (ESP) surface analysis, and the localized orbital locator (LOL) calculation. Compounds 4a and 4b have higher detonation velocities (4a: Dv ​= ​8328 ​m ​s−1; 4b: Dv ​= ​7681 ​m ​s−1) than the conventional explosive 2,4,6-trinitrotoluene (TNT; Dv ​= ​6881 ​m ​s−1) according to an energetic evaluation. Moreover, the thermal properties and sensitivities of 4a (Td ​= ​155 ​°C, IS ​= ​15 ​J, FS ​= ​288 ​N) and 4b (Td ​= ​192 ​°C, IS ​= ​20 ​J, FS ​= ​216 ​N) were greatly improved compared with the previously reported energetic furazan-1,4,2,5-dioxadiazine derivatives N,N'-((1,4,2,5-dioxadiazine-3,6-diyl)bis(1,2,5-oxadiazole-4,3-diyl))dinitramide (i; Td ​= ​106 ​°C, IS ​= ​4.5 ​J, FS ​= ​100 ​N) and 3,6-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazine (ii; Td ​= ​148 ​°C, IS ​= ​2.2 ​J, FS ​= ​116 ​N). The excellent sensitivities and acceptable detonation velocities of compounds 4a and 4b make them good candidates for potential mechanically low-sensitive explosives. These findings will enrich the further application of nitrogen heterocycle 1,4,2,5-dioxadiazine in the field of energetic materials.

Syntheses, crystal structures and thermal behavior of two new Sr(II) complexes derived from tetrazole-based carboxylic acids

Metal-organic frameworks(MOFs) derived from high-energy ligands such as nitrogen-rich heterocycles bridging metal ions have been demonstrated to be the strategies to construct safety energetic materials. Here we chose two tetrazole-based carboxylic acids, 5-(2-pyrazinyl) tetrazole-2(1-methyl) acetic acid (HL1) and 3,3-di(1H-tetrazol-5-yl) pentanedioic acid (H4L2), as ligands to build two new Sr(II) complexes: [Sr(L1)2(H2O)2] (1) and [Sr8(L2)4(CH3CH2OH)2(H2O)19]·2(H2O) (2). These complexes have been characterized by elemental analysis, FT-IR and single crystal X-ray diffraction. Complex 1 displays a 1D chain, while complex 2 shows a novel 2D framework. The differential scanning calorimetry and thermogravimetric-differential thermogravimetric analyses were adopted to investigate the thermal decomposition processes of the complexes 1–2 and the thermodynamic parameters (ΔH, ΔS and ΔG) were obtained. The results show that both 1–2 may be the potential energetic materials.

A DFT approach towards understanding the thermal stability of TKX-50 and their key precursors through band gaps and MESP.

TKX-50 (dihydroxylammonium 5,5'-bistetrazolate-1,1'-dioxide) is a recent time invention by Klapotke et. al. in the field of high energy materials, and it outperforms all the existing materials by means of performance parameters. It is rising as potential energetic material due to favorable thermal insensitivity, low toxicity and safe handling. The decomposition temperature (Tmax) values of precursors such as glyoxime (I), 1,2-dichloroglyoxime (II), 1,2-diazidoglyoxime (III), and bistetrazoledihydroxide (IV) and ending products TKX-50 (V) and ABTOX (VI) have been attempted to correlate with the results obtained from molecular electrostatic potentials and band gaps calculated from the difference of ionization potential and electron affinity. The molecular electrostatic potential values of azido attached -NO group of III are much less than that of hydro/chloro attached -NO group of I/II and that of tetrazole groups IV, V, and VI. The band gaps calculated from stability trend in the increasing order of III < II < I < IV < V < VI are well corroborated with stability trend drawn from experimentally determined decomposition temperatures. Further, employing conceptual density functional theory (DFT) molecular descriptors, band gap values were calculated via the difference of ionization potential and electron affinity to understand the thermal stability of TKX-50, ABTOX, and its precursors.

Energy-releasing properties of metal hydrides (MgH2, TiH2 and ZrH2) with molecular perovskite energetic material DAP-4 as a novel oxidant

Metal hydride has been used as a potential energetic material due to its high hydrogen storage density, high reactivity, high mass calorific value and large gas production. But it was still a great challenge towards optimizing and enhancing the energy-releasing properties of metal hydride. In this work, a novel molecular perovskite energetic material (H2dabco)[NH4(ClO4)3] (DAP-4) was introduced as a high energy oxidant to fabricate metal hydride (MH2, M=Mg, Ti, and Zr) based energetic composites. The thermal decomposition, ignition and combustion characteristics of MH2-based energetic composites were studied. The results showed that molecular perovskite energetic material DAP-4 was beneficial as oxidant in MH2-based high-energy solid composites, which were originated from its high energy properties and strong oxidation capacity. The ignition and combustion reaction mechanisms of MH2 with DAP-4 as oxidant were provided. This work offered an effective way to realize energy-releasing performance of MH2 by molecular perovskite energetic materials introduced for their potential application.

Energetic Salts of Sensitive N,N'-(3,5-Dinitropyrazine-2,6-diyl)dinitramide Stabilized through Three-Dimensional Intermolecular Interactions.

N-nitration of 2,6-diamino-3,5-dinitropyrazine (ANPZ) leads to a sensitive energetic compound N,N'-(3,5-dinitropyrazine-2,6-diyl)dinitramide. This nitro(nitroamino) compound was stabilized by synthesizing energetic salts, dipotassium (3,5-dinitropyrazine-2,6-diyl)bis(nitroamide) (3) and diammonium (3,5-dinitropyrazine-2,6-diyl)bis(nitroamide) (4). Compounds 3 and 4 are fully characterized by single-crystal X-ray diffraction. Compound 3 exhibits a three-dimensional energetic metal-organic framework (3D EMOF) structure and an outstanding overall performance by combining high experimental density (2.10 g cm-3), good thermal stability (Td(onset) = 220 °C), and good calculated performance of detonation (D = 8300 m s-1, P = 29.9 GPa). Compound 4 has acceptable thermal stability (155 °C), moderate experimental density (1.73 g cm-3), and good calculated performance of detonation (D = 8624 m s-1, P = 30.8 GPa). The sensitivities of compounds 3 and 4 toward impact and friction were determined following standard methods (BAM). The energetic character of compounds 3 and 4 was determined using red-hot needle and heated plate tests. The results highlight a 3D EMOF (3) based on a six-membered heterocycle as a potential energetic material.

Assembling high nitrogen isomeric energetic molecules via a lithium-mediated concerted [2 + 3] reaction of two diazo compounds

The search for high nitrogen isomeric energetic molecules and comparison of their structure–property relationship are always attractive in the field of energetic materials. In this paper, a novel lithium-mediated concerted [2 + 3] reaction with two diazo compounds has been accomplished which leads to the simultaneous formation of two isomeric cyanotetrazoles (2a and 2b). The cyano group in cyanotetrazoles was further converted to tetrazole or tetrazole N-oxide to form tricyclic heterocyclic products (3a, 3b, 7a, and 7b). The energetic properties of the compounds were studied. A representative compound 3a (Td = 220 °C, D = 9052 m s−1, IS = 13 J, FS = 200 N) has better detonation performances, higher thermal stability and lower mechanical sensitivities than RDX, which is expected to serve as a potential energetic material.

Unexpected Synthesis of Oxadiazole Analogues: Characterization and Energetic Properties

AbstractAn attractive synthetic route was devaluped for making N‐(4‐(1,2,4‐oxadiazol‐3‐yl)‐1,2,5‐oxadiazol‐3‐yl) formamide (4) and di(1,2,4‐oxadiazol‐3‐yl) methanone O‐(nitrodi(1,2,4‐oxadiazol‐3‐yl)methyl) oxime (6) from commercially available inexpensive malononitrile starting material with easy purification, short experimental time and high yields at room temperature. The chemical structures of 4 and 6 were identified by NMR, IR, EA and verified by single‐crystal X‐ray studies. A plausible mechanism is proposed for the conversion of 4 to 6. Furthermore, both compounds have been evaluated for energetic applications. Based on their insensitive nature and good detonation performance, they are potential energetic materials.