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Abstract:

Abstract:To further balance the energy and safety of 5-nitro-3-（trinitromethyl）-1H-1，2，4-triazole， four nitrogen-rich energetic ionic salts were synthesized using 2-（5-amino-1H-1，2，4-triazole-3-yl） acetic acid as a starting material through a silver salt substitution reaction. The structures of all new compounds were characterized using nuclear magnetic resonance， Fourier transform infrared spectroscopy， differential scanning calorimetry， thermogravimetric analysis， and single crystal X-ray diffraction. The results indicate that the ammonium salt， hydrazine salt， and guanidine salt of 5-nitro-3-（trinitromethyl）-1H-1，2，4-triazole exhibit higher initial decomposition temperature than that of the precursor. Moreover， the hydrazine salt， guanidine salt and triaminoguanidine salt belong to the different crystal systems with distinct crystal packing arrangements and densities. However， they share consistent characteristics in terms of intermolecular weak interactions， with the H…O interaction being the predominant contributor. With the decreasing of the ratios of N…O and O…O interactions， the sensitivity of the nitrogen-rich energetic ionic salts to mechanical stimuli decreases. Finally， the analysis of the distribution of molecular electrostatic potential supplements the explanation for the change in impact sensitivity of 5-nitro-3-（trinitromethyl）-1H-1，2，4-triazole after salt formation. Among the four ionic compounds， the hydrazine salt exhibits outstanding detonation performance （D=8634 m·s^-1， p=30.2 GPa， I_sp=263.5 s） with relative high sensitivity. In contrast， the triaminoguanidine salt demonstrates excellent overall performance. It has a detonation velocity comparable to that of the hydrazine salt （D=8627 m·s^-1）， a heat of formation nearly 1.4 times greater than that of the precursor （ΔH_f=0.644 kJ·g^-¹）， and a low mechanical sensitivity （IS=10.3 J， FS=150 N）.

Abstract:5，7-Diamino-8-nitrotetrazolo［1，5-c］pyrimidine （3） was synthesized by a two-step reaction of nitration and cycloaddition using 2，4-diamino-6-chloropyrimidine （1） as raw material. The structure of 3 was characterized by nuclear magnetic resonance spectrometer （NMR）， Fourier transform infrared spectrometer （FT-IR）， elemental analyzer （EA） and single crystal X-ray diffractometer （SC-XRD）. The thermal behavior of 3 was analyzed by differential scanning calorimeter （DSC） and thermogravimetric （TG）. The detonation properties were calculated by Gaussian and Explo5. The sensitivities were measured using BAM impact and friction sensitivity testers. The results show that the crystal of compound 3·DMSO belongs to monoclinic system， space group P2₁/c， and the cell parameters are a=4.7331（3） Å， b=22.8991（13） Å， c=10.6580（6） Å， α=90°， β=99.758（2）°， γ=90°， V=1138.44（12） ų， Z=4. The crystal density is 1.600 g·cm^-3 （296 K）. The theoretical detonation velocity and pressure of 3 are 8570 m·s^-1 and 28.2 GPa， respectively. The impact and friction sensitivities of 3 are 22 J and 305 N， respectively.

Abstract:To promote the green development of energetic materials and improve their thermal stability and energy performance， the electrochemical synthesis of tetrazole-1，3，4-oxadiazole azo energetic compounds （H₂AzAOT） and its metal salts （Mn-AzAOT， Zn-AzAOT， Pb-AzAOT） were studied by inserting the azoxadiazole ring block into the molecule. The structures of H₂AzAOT and its metal salts were characterized by single crystal X-ray diffraction， infrared spectroscopy and nuclear magnetic resonance. The thermal stability， impact sensitivity and friction sensitivity were studied by differential scanning calorimetry and standard BAM method. The detonation performances were calculated by EXPLO5 program. The results indicate that H₂AzAOT and its metal salts have excellent physicochemical properties. Among them， the theoretical detonation velocity （D） and detonation pressure （p） of H₂AzAOT are 8511 m·s^-1 and 28.9 GPa， respectively. The D and p of Pb-AzAOT are 8934 m·s^-1 and 29.7 GPa， respectively. The detonation performances of both compounds are significantly better than that of the traditional heat-resistant and insensitive energetic material hexanitrostibene （HNS） （D=7612 m·s^-1， p=24.7 GPa）.

Abstract:A novel high-energy compound， 6-Amino-4-（trinitromethyl）-2-carbonyl-1H-1，3，5-triazine， was synthesized in one step. The crystal structure of this compound was characterized by X-ray single crystal diffraction. Its structure and properties were characterized by ¹H and ¹³C NMR， FT-IR and DSC. The detonation performance was calculated by EXPLO5. The sensitivity testing was performed according to the BAM standard method.The compound crystallizes in orthorhombic space group C 2/c， a=10.183（4） Å， b=9.388（3） Å， c=21.324（8） Å， V=2005.9（13） ų， α=90°， β=100.246（10）°， γ=90°， Z=8. The calculated detonation velocity and pressure for compound 1 are 8167 m·s^-1 and 27.6 GPa， respectively， with measured impact sensitivity of 6 J and friction sensitivity of 210 N.

Abstract:A pyridine energetic molecule， N²，N⁶-dimethyl-N²，N⁴，N⁶，3，5-pentanitro-2，4，6-pyridinetriamine （NNDP）， has been synthesized in two steps from 4-amino-2，6-dichloropyridine. The process was found to be effective and simple. The structure of this compound is characterized by ¹H and ¹³C NMR， FT-IR and DSC. The crystal structure of this compound is characterized by X-ray single crystal diffraction. Results shows that compound NNDP belongs to the monoclinic space group P 2₁/c， a=16.3215（17） Å， b=7.9819（8） Å， c=13.1954（13） Å， V=1712.3（3） ų， α=90（6）^o， β=95.093（3）^o， γ=90（7）^o， Z=4. The presence of multiple nitro and nitramine groups contributes to a low decomposition temperature. Its detonation performance was predicted using EXPLO5， and sensitivity testing was conducted using the BAM standard method.It was found that the detonation performance and impact sensitivity of NNDP（D=8762 m·s^-1， p=34.5 GPa， IS=7.7 J） are comparable to those of RDX.

Abstract:To understand the properties of the novel polynitrogen compound hexazine anion ［N₆］^4-， computational chemical methods were used to study the electronic structure， bonding properties and aromaticity of N₆， ［N₆］^2- and ［N₆］^4-. The M06-2X method combined with the def2-TZVP basis set was used to optimized the structures and calculated the electronic structure features， such as bond length， bond angle， dihedral angle， molecular size and so on. Subsequently， multiple bond orders were calculated， using the atoms-in-molecules （AIM） theory to calculate multiple bond properties， and drawing the electron deformation density map to directly show the bond behavior. Finally， various aromatic indices were calculated to show the aromatic characteristics of three hexazine rings. The calculation results show that by comparing with the electronic structure optimized by CCSD， the M06-2X method in the common DFT method is suitable for studying the current system. Mayer bond order shows that the N—N bond has a certain degree of σ bond characteristics. The aromaticity study shows that the［N₆］^4- is aromatic， with the aromatic harmonic oscillator model （HOMA） value at 0.96 and the nuclear independent chemical shift （NICS_ZZ（1）） at -18.97. The IR， Raman and UV-Visible spectra of ［N₆］^4- were simulated to provide reference for experimental detection.

Abstract:By using 5-amino-3-nitro-1，2，4-triazole （ANTA） as raw material， a new methyl-bridged nitrogen-oxygen heterocyclic energetic compound 3-（（5-amino-3-nitro-1H-1，2，4-triazol-1-yl）methyl）-1，2，4-oxadiazol-5-amine （3） was synthesized through a three-step reaction. The reaction conditions， including solvent， reaction temperature， and reaction time， were thoroughly investigated. Compounds 1-3 were characterized by nuclear magnetic resonance （NMR）， fourier-transform infrared spectroscopy （FT-IR） and elemental analysis （EA）. Single crystal X-ray diffraction analysis was also performed on compound 3. The properties of compound 3 were studied by vacuum densitometer， thermogravimetric differential scanning meter and impact/friction sensitivity meter. The theoretical detonation performances of compound 3 were calculated by Gaussian software. Results show that the total yield of compound 3 is 35.4% based on ANTA. The crystal packing of compound 3 belongs to the monoclinic system， space group P2₁/c， and each cell contains four molecules （Z=4） with a large number of intramolecular and intermolecular hydrogen bonds. The density of compound 3 is 1.68 g·cm^-3， the decomposition temperature is 232.2 ℃， the friction sensitivity is above 360 N， and the impact sensitivity is above 40 J. The theoretical detonation velocity and pressure of compound 3 are 7196 m·s^-1 and 22 GPa， respectively， which are better than that of the traditional explosive TNT（D， 6881 m·s^-1； P， 21.3 GPa）.

Abstract:To study the thermal decomposition behavior of 2，2-azobi［4， 5-bis（tetrazole-5-yl）］-1，2，3-triazole （NL24）， the structure， morphology and thermal decomposition characteristics of NL24 were studied by means of scanning electron microscopy， thermogravimetric analyzer， differential scanning calorimeter and thermogravimetric infrared mass spectrometry. The kinetic parameters such as apparent activation energy and pre-exponential factor were calculated by Kissinger， Ozawa and Šatava-Šesták method， and the thermal decomposition mechanism of NL24 was speculated. Results show that NL24 has two main weight loss stages at the heating rate of 10 ℃·min^-1. The first weight loss stage occurs at about 180 ℃， which belongs to the volatile endothermal process of dimethyl sulfoxide. The violent thermal decomposition of NL24 occurs at the second weight loss stage between 270 ℃ and 300 ℃， which has not only rapid gas generation rate， but also belongs to autocatalytic reaction. The main gaseous products are N₂， HCN， HN₃， etc. The apparent activation energy and pre-exponential factor of the decomposition process are 174.69 kJ·mol^-1 and 10^16.60 s^-1， respectively. The reaction model of thermal decomposition stage of NL24 is random nucleation and subsequent growth.

Abstract:To improve the safety and reduce the toxicity of the synthesis process for 3，4-bis（4-nitro-1，2，5-oxadiazol-3-yl）-1，2，5-oxadiazole-2-oxide （DNTF）， a four-step route was developed starting from 1，3-acetonedicarboxylic acid， involving oximation， cyclization， oxidation， and nitration. The synthesis employed two critical intermediates： 3-amino-4-（carboxymethyl）furazan （formed after cyclization） and 3-nitro-4-（carboxymethyl）furazan （generated during nitration）. The process achieved an overall yield of 22% with the final product purity exceeding 98%. The structures of key intermediates and products were characterized by single-crystal X-ray diffraction， nuclear magnetic resonance， and infrared spectroscopy. The optimal synthesis process was determined through single-factor experiments， with an oxidation reaction yield of 97% and a nitration reaction yield of 56.5%. The process safety risks of oxidation and nitration reactions were studied by DSC， ARC， and RC1. The results showed that the oxidation reaction process had a high hazard level， while the nitration reaction process was classified as level 2. This synthesis route has promising potential for industrial-scale application.

Abstract:Sodium pentazolate （NaN₅） is a nitrogen-rich compound with high energy density and rapid energy release rate. However， its combustion suffers from slow burning rate， high sensitivity， and poor self-sustaining combustion. In this study， by using a coordination complex strategy based on NaN₅ with graphene oxide （GO） and polydopamine （PDA）， a series of NaN₅-based composite energetic materials were synthesized via solvent evaporation and co-precipitation. The morphology and structure of the composites were characterized by scanning electron microscopy （SEM）， Fourier-transform infrared spectroscopy （FT-IR）， and X-ray photoelectron spectroscopy （XPS）. The thermal decomposition behavior and mechanism were investigated using synchronous thermal analysis （TG-DSC） and reaction kinetics simulations. The combustion and detonation performances were evaluated via hot-wire ignition tests. Results demonstrate that after GO/PDA modification， the structure of NaN₅-3%GO-1%PDA is optimized from cubic crystal to porous folded layer with strong interfacial bonding. Compared with pristine NaN₅， the stepwise decomposition temperature difference of NaN₅-3%GO-1%PDA is reduced by 61.1 ℃， the activation energy decreases by 30.7 kJ·mol^-1， and the detonation growth time is reduced from 33.33 μs to 16.67 μs ， proving that NaN₅-3%GO-1%PDA has a faster energy release rate.

Abstract:As a typical energetic substituent， N-NO₂ group exhibits high work capacity and is fundamental to the energy release of typical explosives such as RDX， HMX， and CL-20. Nitrogen-rich heterocyclic energetic compounds have garnered extensive research interest due to their high enthalpy of formation， high density， and environmental compatibility. However， the introduction of N-NO₂ is significant challenging due to the varying electrophilic reactivity of the NH sites in nitrogen-rich frameworks and the metastable structures of the energetic molecules. Therefore， summarizing the synthesis reactions and properties of various nitrogen-rich frameworks containing N-NO₂ is of great importance for the development of novel energetic materials with practical applications. This review categorizes nitrogen-rich energetic frameworks and summarizes the synthesis and properties of N-NO₂ in imidazole， pyrazole， triazole， and six-membered nitrogen-rich energetic heterocyclic compounds. The future development potential and research trend of nitrogen-rich energetic compounds with N-NO₂ nitration of heterocyclic NH groups are also prospected， so as to provide a valuable reference and guidance for the skeleton design， multi-functional group synergistic effect and synthesis of new N-NO₂ based energetic materials.

Abstract:Nitrogen-rich energetic compounds have attracted a great attention due to the high nitrogen content， high energy density， good thermal stability， low sensitivity， and environmental friendliness. Among the stable azoles， tetrazole has the highest nitrogen content and energy level. Introducing diverse energetic rings or substituent groups into the tetrazole backbone offers a promising strategy for designing nitrogen-rich energetic materials with outstanding energetic performance and appropriate sensitivity. This review systematically summarizes the synthetic methods of nearly 200 tetrazole-based nitrogen-rich energetic compounds， categorizes these compounds based on the number of rings and connection modes， and highlights the physicochemical and detonation properties of representative energetic compounds. Finally， the future developments for these materials are prospected： creating tetrazole-based energetic compounds with new structures， promoting the engineering process of materials with promising applications， and conducting research on the application of compound 52（TKX-50）.