Excellent Detonation Performance Research Articles

A π-Stacked Highly Stable, Insensitive, Energy-Containing Material with a Useful Planar Structure

Abstractπ-Stacking is common in materials, but different π–π stacking modes remarkably affect the properties and performances of materials. In particular, weak interactions, π-stacking and hydrogen bonding often have a significant impact on the stability and sensitivity of high-energetic compounds. A fused [5,7,5]-tricyclic energetic compound with a conjugated structure has been designed and synthesized. 4H-[1,2,5]Oxadiazolo[3,4-e][1,2,4]triazolo[3,4-g][1,2,4]triazepin-8-amine is obtained in 48% yield from 3-amino-4-carboxy-1,2,5-oxadiazole through an efficient two-step reaction. Owing to its layered planar structure and weak π interactions between layers, 4H-[1,2,5]oxadiazolo[3,4-e][1,2,4]triazolo[3,4-g][1,2,4]triazepin-8-amine exhibits high thermal stability (T d = 318 °C), low sensitivity (IS = 40 J, FS = 360 N), and relatively excellent detonation performance (D = 7059 ms–1, P = 20.2 GPa). This detonation performance is superior to that of the conventional explosive TNT. The developed procedure provides a new method for the synthesis of fused ring compounds.

Theoretical study on different substituent-modified derivatives of 6-dinitrophenyl-5,6,7,8-tetrahydro-4-imidazo [4,5-e]furazano[3,4-b] pyrazine.

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 2.17g/cm3, the detonation velocity ranges from 8.01 to 10.26km/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 = 10.1km/s, P = 47.72 GPa), H8 (D = 10.11km/s, P = 47.92 GPa), and I8 (D = 10.26km/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. 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.

Regioisomeric functionalization of azo-bridged nitropyrazoles: Pushing the density limit of catenated nitrogen systems

Fully energetic functionalization of catenated nitrogen systems is highly challenging due to the lack of incorporation methodology. In this work, two catenated nitrogen N6 structures containing six nitro groups, i.e., (E)-1,1′-bis [5-Nitroamide-3,4-dinitro-1H-pyrazole] diazene (N-N6A) and its regioisomer (E)-1,1′-bis [4-Nitroamide-3,5-dinitro-1H-pyrazole] diazene(N-N6B) were designed and synthesized. Despite the same chemical formula and azo functionality, N-N6B exhibits better overall performance than N-N6A. Meanwhile, N-N6B has the highest density with excellent detonation performance (d = 1.94 g cm−3, Dv = 9440 m s−1, and P = 39.6 GPa) among the reported long-catenated nitrogen atom chains, indicating the potential for high energy materials. Particularly, as the precursors of N-N6A and N-N6B, the mechanical sensitivities of N6A and N6B (N6A, IS = 11 J, FS = 160 N; N6B, IS = 14 J, FS = 240 N) are apparently superior to that of literature long nitrogen-chains energetic material. The different performance of these compounds highlights the effect of the regioisomeric functionalization on designing advanced energetic materials.

Electrochemical Efficient Synthesis of Two Azo Energetic Compounds

AbstractAzo compounds with a high density, high enthalpy, and excellent detonation performance have received increasing research attention. The conventional method of chemical dehydrogenation that is used to form azo compounds involves the use of strong oxidants, resulting in environmental pollution. Electrochemical organic synthesis is considered an old method and a new technology. In this work, azofurazan tetrazole {H2AzFT; 5,5′-[diazene-1,2-diylbis(1,2,5-oxadiazole-4,3-diyl)]bis-1H-tetrazole} and azofurazan hydroxytetrazole (H2AzFTO) were synthesized by a green and efficient electrochemical dehydrogenation coupling of 5-(4-aminofurazan-3-yl)-1H-tetrazole and 5-(4-aminofurazan-3-yl)-1-hydroxytetrazole, respectively. The structures of H2AzFT and (NH4)2AzFTO were fully characterized by infrared spectroscopy, nuclear magnetic resonance, and elemental analysis, and their thermal stabilities were determined by differential thermal analysis.

Enhancing Conjugation Effect to Develop Nitrogen-Rich Energetic Materials with Higher Energy and Stability.

This work reports a strategy by enhancing conjugation effect and synthesizes a symmetrical and planar compound, 1,2-bis (4,5-di(1H-tetrazol-5-yl)-2H-1,2,3-triazol-2-yl)diazene (NL24). The incorporation of azo and 1,2,3-triazole moieties manifests a synergistic effect, amplifying the conjugation effect of the azo bridge and thereby elevating the stability of NL24 (Td: 263 °C, IS: 7 J). Notably, NL24, possessing a structural configuration comprising four tetrazoles harboring a total of 24 nitrogen atoms, exhibits excellent detonation performances (ΔHf: 6.06 kJ g-1, VD: 9002 m s-1). This strategy achieves the balance of energy and stability of polycyclic tetrazoles and provides a direction for high-performance energetic materials.

Intramolecular assembly of dinitromethyl and bistetrazole: a strategy for constructing advanced and environmentally friendly high-energy density materials

Target compound BDNBT exhibits excellent detonation performance, indicating its potential as a novel type of high-energy density material (HEDM).

The new dual anion solvent-free nickel complex based on the pyridine-4-carbohydrazide ligand

The first dual anion nickel complex has been prepared, and its structure and properties were studied. This complex possessed excellent detonation performance (D = 6350 m s−1 and P = 16.7 GPa) and insensitivity (IS = 40 J and FS = 360 N).

Study on the Crystal Structure and Properties of a New Crystal Form of 3-nitro-1,2,4-triazole-5-one (NTO)

3-nitro-1,2,4-triazole-5-one (NTO) has obtained wide attention and application for excellent detonation performance and low sensitivity. A new crystal form of NTO was prepared via the solvent evaporation method, which was...

Properties of Mixed Crystal Coprecipitation Substances of Ammonium Nitrate and Potassium Perchlorate Prepared by the Evaporative Solvent Method.

Ammonium perchlorate (AP) has been widely used as an oxidizer in propellants and military mixed explosives in recent years. However, its high characteristic signal, environmental pollution, and poor detonation performance have prompted the industry to seek alternatives to AP. Ammonium nitrate (AN) is a suitable substitute due to its low characteristic signal, lack of pollution, and excellent detonation performance. However, its room-temperature phase transition and hygroscopicity affect its practical use. In this work, we prepared mixed crystal coprecipitation (MCC) materials of AN and potassium perchlorate (KP) using the evaporative solvent method. The characterization of AN/KP MCCs was carried out by combining TG-DSC, XRD, FT-IR, and SEM analysis, revealing that the formation of MCCs by AN and KP is due to ion exchange between the two components. AN/KP MCCs not only solve the problem of room-temperature phase transition in AN but also reduce its hygroscopicity. Furthermore, AN/KP MCCs have mechanical sensitivity, explosive performance, and specific impulse similar to pure AN, but compared to AN, AN/KP MCCs have higher density, effective oxygen content, and thermal stability. Compared with existing oxidizers AN, AP, and KP, AN/KP MCCs with high density, low sensitivity, high oxygen content, and high safety have obvious advantages and have good prospects in the application of oxidizers in solid propellants and military mixed explosives.

Theoretical study about the thermal stability and detonation performance of the nitro-substituted derivatives of 4-(1H-1,2,4-triazol-1-yl) pyrimidine

The nitro groups are introduced into 4-(1H-1,2,4-triazol-1-yl) pyrimidine to substitute the hydrogen atoms successively, through which a total of 31 derivatives are constructed to look for high energy density compounds (HEDCs). To probe the thermal stabilities, the heats of formation (HOFs) are calculated by using the G3MP2 method. To explore the dynamic stability, the natural bond orbital (NBO) analysis is performed to confirm the trigger bond, for which the bond dissociation energy is calculated using the B3PW91 method with the 6-311 + G(d,p) basis set. Furthermore, the detonation velocity (D), the detonation pressure (P), the molecular density (ρ), the explosive heat (Q), and character height (H50) are also predicted. Based on our calculation, it is confirmed that D1, D2, D5, and E are potential high-energy-density compounds with sufficient stability and excellent detonation performance.

Preparation of flame-retardant HNS/DAAF energetic composite microspheres using droplet microfluidic technology

2,2′,4,4′,6,6′-Hexanitrostilbene (HNS) exhibits excellent detonation performance and has the potential to play a significant role in aerospace technology. However, its application is limited by the extreme space environment. In this study, glycidyl azide polymer/nitrocellulose (GAP/NC) was used as a binder to prepare HNS/DAAF energetic composite microspheres with different mass ratios using droplet microfluidic technology. The morphology, particle size, crystal structure, thermal decomposition, bulk density, mechanical sensitivity, and combustion behavior of the microspheres were characterized and tested. The results showed that the HNS/DAAF composite microspheres exhibited high sphericity and narrow particle size distribution while preserving the crystal structure of HNS. Compared to raw HNS, the HNS/DAAF composite microspheres demonstrated improved thermal stability and enhanced safety performance. Additionally, ignition experiments revealed that the addition of DAAF effectively suppressed the combustion of HNS. These findings provide valuable insights for the safe utilization of HNS in high-temperature environments.

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.

Design and Synthesis of Energetic Melt-Castable Materials by Substituent-Specific Modification.

With the increase in the demand for high-performance composite explosives, the search for advanced energetic melt-castable compounds has attracted increasing attention in the field of energetic materials. Herein, two new energetic materials with nitromethyl and azidomethyl substituents (1-(nitromethyl)-3,4-dinitro-1H-pyrazole (NMDNP) and 1-(azidomethyl)-3,4-dinitro-1H-pyrazole (AMDNP) were prepared by the substituent modification of a potential melt-castable molecule ((3,4-dinitro-1H-pyrazol-1-yl) methyl nitrate, MC-4), respectively. NMDNP exhibited a suitable melting point (90 °C), good thermal stability (Td : 185 °C) and excellent detonation performance (8484 m s-1 ) and impact sensitivity (25 J), thereby demonstrating promise as an energetic melt-castable material. Simultaneously, compared with the nitrato-methyl and azidomethyl substituents, the nitromethyl substituent exhibited greater advantages in regulating performance.

2,2'-Azobis(1,5'-bitetrazole) with a N10 Chain and 1,5'-Bitetrazolate-2N-oxides: Construction of Highly Energetic Nitrogen-Rich Materials Based on C-N-Linked Tetrazoles.

A series of high-nitrogen compounds, including a unique molecule 2,2'-azobis(1,5'-bitetrazole) with a branched N10 chain and 1,5'-bitetrazolate-2N-oxides, were synthesized successfully based on C-N-linked 1,5'-bistetrazoles using azo coupling of N-amine bonds and N-oxide introduction strategies. All compounds were characterized by NMR spectroscopy, IR spectroscopy, elemental analysis, and differential scanning calorimetry, in which the structures of five compounds were further determined by single-crystal X-ray diffraction analysis (2, T-N10B, 3a, 3b, and THX). The nitrogen contents of these five compounds range from 63.62 (THX) to 83.43% (T-N10B), which are much higher than that of CL-20 (38.34%). The heat of formation for the prepared compounds was calculated by using the Gaussian 09 program, with T-N10B having the highest value of 5.13 kJ g-1, about 6 times higher than that of CL-20 (0.83 kJ g-1). The calculated detonation performances by EXPLO5 v6.05.04 show that THX has excellent detonation performance (D = 9581 m s-1, P = 35.93 GPa) and a remarkable specific impulse (Isp = 284.9 s).

Discovery of high energy and stable prismane derivatives by the high-throughput computation and machine learning combined strategy

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.

Preparation of Primary Explosive by Self-assembly of Combustible and Oxidizing Agents under Acid.

In order to further explore the effect of ligands on the performance of primary explosives and gain a deeper understanding of the coordination mechanism, we designed furan-2-carbohydrazide (FRCA), a ligand, by using oxygen-containing heterocycles and carbohydrazide. Then, FRCA and Cu(ClO4)2 were used to synthesize coordination compounds [Cu(FRCA)2(H2O)(ClO4)2]·CH3OH (ECCs-1·CH3OH) and Cu(FRCA)2(H2O)(ClO4)2 (ECCs-1). The structure of the ECCs-1 was confirmed by single-crystal X-ray diffraction, IR and EA characterization. Further experiments on ECCs-1 show that ECCs-1 has good thermal stability, but is sensitive to mechanical stimuli (impact sensitivity = IS = 8 J, friction sensitivity = FS = 20 N). The predicted value of the detonation parameter is DEXPLO5 = 6.6 km s-1, PEXPLO5 = 18.8 GPa, but the ignition test, laser test, and lead plate detonation experiment show that ECCs-1 has excellent detonation performance, which is very worthy of attention.

Site-Selective Oxidative Coupling Reaction of Diamines toward Aminoazo Compounds

A selective oxidative coupling reaction of a diamine containing both C- and N-NH2 was achieved using acidic potassium permanganate as the coupling reagent. The reaction conditions were optimized, and the reaction selectivity was illustrated by quantum calculations. Furthermore, the azo-coupled product was derivatized to four nitroamine energetic materials with excellent detonation performances.

Theoretical exploration of polynitrogen compounds N6, N8, N10, and N6 ions based on N3 − and cyclo-N5 −

ABSTRACT Polynitrogen energetic materials have become an important branch of high-energy-density materials. In this work, a thorough theoretical exploration of polynitrogen compounds N6, N8, N10, and N6 ions was conducted based on N3 − and pentazolate anion (cyclo-N5 −). Based on quantum chemistry calculations and wavefunction analyses, the equilibrium geometry, bond orders, atoms-in-molecules analysis, atomic charges, electrostatic potential distribution, frontier molecular orbitals, and many indices to represent aromaticity were determined and represented. In addition, their densities, heat of formation, detonation properties, and impact sensitivities were calculated using thermodynamics methods. These polynitrogen compounds could exhibit good density (1.578–1.814 g cm−3); high heat of formation (7.45–8.05 kJ g−1); excellent detonation performance (D: 9206–10413 m s−1, P: 34.8–44.7 GPa). The detonation performance demonstrates that polynitrogen compounds are promising energetic materials.

Efficient Synthesis of Nanoscale Cadmium Azide from Intercalated Cadmium Hydroxide for Nanoexplosive Applications

Due to its good sensitivity, detonation ability, and high-temperature resistance, cadmium azide is expected to be applied to microinitiating systems. Here we demonstrate an effective synthetic methodology (GAF-IH) to prepare nanoscale cadmium azide. A nanoscale mesoporous configuration is designed to construct azide precursor utilizing controlled self-assembly of inorganic and organic molecules followed by in situ carbonization crystallization. The nanoscale porous precursors can react with HN3 gas to form nanoscale cadmium azide composites (CdA/SA and CdA/C) in just 3 h, which takes much less time than traditional preparation methods of cadmium azide. The organic molecules and their carbonized skeletons can act as the carriers of nanoscale cadmium compounds to avoid agglomeration, as supporting materials for building HN3 azide gas channels, and as functional components in the nanoscale cadmium azide composites to influence their performance. CdA/C prepared by this route has favorable comprehensive properties, which not only has a high content of CdA (93.8%), indicating excellent detonation performance (tID < 10 μs), but also has good high-temperature resistance (Tp = 365 °C) and low electrostatic sensitivity (E50 = 1.76 J). Thanks to its nanoscale characteristics and outstanding performance, CdA/C has the potential to replace CA and modified CA in the application of microinitiating devices.

Pushing the limits of the heat of detonation via the construction of polynitro bipyrazole.

The trinitromethyl group is a highly oxidized group that is found as an active functionality in many high-energy-density materials. The most frequently used previous synthetic method for the introduction of the trinitromethyl group is the nitration of heterocyclic compounds containing an acetonyl/ethyl acetate/chloroxime group. Now a novel strategy for constructing a trinitromethyl group (5) via nitration of an ethylene bridged compound, dipyrazolo[1,5-a:5',1'-c]pyrazine (2), is reported. In addition, the other two nitrated products (3 and 4) were obtained under different nitrating conditions. Compound 5 has excellent detonation performance (Dv = 9047 m s-1, P = 35.6 GPa), and a low mechanical sensitivity (IS = 10 J, FS = 216 N), with an especially attractive heat of detonation of 6921 kJ kg-1, which significantly exceeds that of the state-of-the-art explosive CL-20 (Q: 6162 kJ kg-1).