Abstract:

Abstract:

Abstract:

Abstract:Two energetic salts based on the pyrazolo［1，5-d］tetrazole fused skeleton， namely 6-azido-7-nitropyrazolo［1，5-d］tetrazolium ammonium salt （4） and 6-amino-7-nitropyrazolo［1，5-d］tetrazolium hydrazinium salt （5）， were synthesized via a three-step reaction using 4，6-dichloro-5-nitropyrimidine as the starting material. Their chemical structures were fully confirmed by Fourier transform infrared （FT-IR） spectroscopy， nuclear magnetic resonance （¹H NMR， ¹³C NMR） spectroscopy， elemental analysis， and X-ray single-crystal diffraction. The results indicate that the addition of aqueous ammonia and hydrazine hydrate promotes the in-situ cyclization of the ortho-azido group in 3，5-diazido-4-nitropyrazole （3）， thereby constructing the pyrazolo-tetrazole fused skeleton. Concurrently， hydrazine hydrate reduces the azido group not involved in the cyclization to an amino group. Based on calculations using the Gaussian 16 program， the formation enthalpies of compounds 4 and 5 are 666.0 kJ·mol^-1 and 461.9 kJ·mol^-1， respectively. The detonation velocities （D） and detonation pressures （p） calculated by the EXPLO 5 software are 8617 m·s^-1 and 28.8 GPa for compound 4， and 8789 m·s^-1 and 28.4 GPa for compound 5. According to the BAM standard test methods， the impact sensitivities （IS） of compounds 4 and 5 are determined to be 1 J and 10 J， while their friction sensitivities （FS） are 5 N and 120 N， respectively.

Abstract:Bistetrazole has become a research focus in the field of energetic materials due to its 80% nitrogen content and excellent detonation performance. However， its poor stability seriously restricts practical engineering applications. In this work， 5，5''-bistetrazole diammonium salt was used as the starting material， and bromonitromethane was grafted onto the bistetrazole skeleton via nucleophilic substitution reaction. A novel nitromethyl-substituted bistetrazole energetic compound 1 with significantly improved stability， which can be potentially used in eutectic systems， was successfully synthesized. The structure of compound 1 was characterized by nuclear magnetic resonance spectroscopy（NMR）， elemental analysis（EA）， and infrared spectroscopy （IR）. Its precise crystal structure was further determined by single-crystal X-ray diffraction： the compound crystallizes in the monoclinic system， space group C2/c， with cell parameter Z = 8 and crystal density 1.683 g·cm^-3. Performance test results show that compound 1 exhibits an impact sensitivity of 15 J， friction sensitivity of 324 N， detonation velocity of 8325 m·s^-1， and detonation pressure of 28.4 GPa， demonstrating superior overall performance compared to TNT （D_v = 6881 m·s^-1， p = 19.5 GPa， IS = 15 J， FS = 353 N）.

Abstract:High-nitrogen polycyclic frameworks， owing to their high nitrogen content and favorable oxygen balance， have attracted considerable attention as promising scaffolds for the development of novel high-energy energetic compounds. A novel high-nitrogen polycyclic nitramine energetic compound， 3-（4-nitropyrazol-1-yl）-7-（N-methylnitramino）-［1，2，4］triazolo［1，5-b］［1，2，4，5］tetrazine （compound 4）， was synthesized via a three-step reaction based on the ［1，2，4］triazolo［1，5-b］［1，2，4，5］tetrazine scaffold. The chemical structure of compound 4 was fully characterized by nuclear magnetic resonance spectroscopy （NMR）， high-resolution mass spectrometry （HRMS）， and infrared spectroscopy （IR）. Single crystals suitable for X-ray diffraction were obtained by slow solvent evaporation， and the crystal structure was determined by single-crystal X-ray diffraction. Results show that compound 4 crystallizes in the orthorhombic crystal system with the Pbca space group and exhibits a layered stacking structure with a room-temperature density of 1.701 g·cm^-3. Thermogravimetry-differential scanning calorimetry （TG-DSC） analysis reveals that the compound possesses a thermal decomposition temperature of 167 ℃. Calculations using the EXPLO5 software demonstrate that its theoretical detonation velocity and detonation pressure reach 8078 m·s^-1 and 25.2 GPa， respectively. Additionally， the impact and friction sensitivities of compound 4， determined by the BAM standard method， are 9 J and 180 N， respectively.

Abstract:Furoxan has been extensively studied due to its high energy provided by potential “nitro” fragment， but the relatively poor stability limits its practical applications. A novel energetic compound， 3，3''-（1，2，5-oxadiazole-3，4-diyl）bis（1，2，4-oxadiazol-5-amine）（1）， was synthesized from dicyanofuroxan via a three-step procedure involving reduction， oximation， and cyclization-dehydration reactions. Subsequent nitration of 1 afforded 3-（4-（5-amino-1，2，4-oxadiazol-3-yl）-1，2，5-oxadiazol-3-yl）-1，2，4-oxadiazol-5（4H）-one（2）. The structures of both compounds were characterized by nuclear magnetic resonance （NMR） spectroscopy， elemental analysis （EA）， infrared （IR） spectroscopy， and single crystal X-ray diffraction analyses. Results show that compound 1 crystallizes in orthorhombic crystal system， space group Pbcn， Z = 4， with a crystal density of 1.825 g·cm⁻³. The trihydrate of compound 2·3H₂O crystallizes in triclinic crystal system， space group P1， Z = 2， with a crystal density of 1.641 g·cm^-3 Both compounds exhibit high insensitivity to mechanical stimuli， with impact sensitivity >40 J and friction sensitivity >360 N. Their calculated detonation velocity （7921 m·s^-1 for 1 and 7660 m·s^-1 for 2） and detonation pressure （22.4 GPa for 1 and 20.5 GPa for 2） are superior to those of TNT （6881 m·s^-1， 19.5 GPa）.

Abstract:Nitrogen-rich fused-ring energetic molecules have gained extensive attention in the field of energetic material due to their high nitrogen content， high enthalpy of formation， and extensive conjugated structures， which enable a better balance between energy and safety. Nevertheless， their synthetic routes are often relatively cumbersome， involving skeleton construction and functional group introduction. In this work， starting from commercially available 4-nitro-1H-pyrazole-3，5-diamine and sodium nitromalonaldehyde， the fused bicyclic energetic molecule 2-amino-3，6-dinitropyrazolo［1，5-a］pyrimidine （1） was synthesized in a one-step reaction with a high yield of 89.3%. The target compound was characterized by nuclear magnetic resonance， infrared spectroscopy， and single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic space group C2/c with a measured density of 1.774 g·cm^-3 at room temperature. Its detonation performance was calculated by EXPLO5 software， its thermal decomposition temperature and mechanical sensitivity were evaluated by thermogravimetry-differential scanning calorimetry and impact/friction sensitivity tests. The results indicates that compound 1 possesses an onset decomposition temperature of 303 ℃， based on measured density， a calculated detonation velocity of 7680 m·s^-1， and a detonation pressure of 22.7 GPa. Its impact sensitivity is better than 60 J， and friction sensitivity is greater than 360 N， demonstrating that it is a thermally stable and insensitive explosive molecule with potential application value.

Abstract:Two neutral energetic compounds， 3-nitro-7-amino-6-（1H-tetrazol-5-yl）pyrazolo［1，5-a］pyrimidine （3） and 2-nitramino-7-amino-6-（1H-tetrazol-5-yl）-［1，2，4］triazolo［1，5-a］pyrimidine （4）， were synthesized via nitration of tetrazole combined fused-ring pyrazolo-pyrimidine and tetrazole combined fused-ring triazolo-pyrimidine. By exploiting the basicity of nitrogen atoms in the pyrimidine ring， nitrate （5， 7） and perchlorate （6， 8） salts were subsequently obtained through proton transfer reactions. The structures of the compounds were characterized by nuclear magnetic resonance spectroscopy （¹H and ¹³C NMR）， Fourier transform infrared spectroscopy （FT-IR）， and elemental analysis （EA）. Single crystals of compounds 5 and 7 were obtained by solvent evaporation， and their crystal structures characterized confirmed by X-ray single-crystal diffraction. Furthermore， their physicochemical properties and mechanical sensitivity were assessed through gas pycnometer， differential scanning calorimetry （DSC）， impact sensitivity/friction sensitivity tests， alongside theoretical calculations of their heat of formation and detonation performance. The results indicate that compounds 4-8 exhibit detonation velocities ranging from 7870 to 8471 m‧s^-1， and detonation pressures from 23.1 to 30.7 GPa， which are superior to that of TNT （D_v： 6881 m‧s^-1， p： 19.5 GPa）. The detonation performance of the nitrate （5， 7） and perchlorate （6， 8） salts surpasses that of their corresponding neutral compounds 3 and 4. Notably， the perchlorate salt （compound 8： D_v： 8471 m‧s^-1， p： 30.7 GPa） exhibits the most outstanding detonation performance. This study demonstrates that constructing tetrazole-fused structures containing basic nitrogen sites， followed by introducing oxygen-rich energetic anions through proton transfer， is an effective strategy for tuning the detonation properties of energetic materials.

Abstract:To address the issues of incomplete amination and difficult removal of acidic impurities in the existing synthetic methods of 4，6-dinitro-5，7-diaminobenzofuroxan （CL-14）， a novel synthetic route for CL-14 was developed. Starting from 1-chloro-3，5-dimethoxybenzene （1）， CL-14 was synthesized via a three-step process involving nitration， azidation/dediazotization， and amination. The effects of molar ratio， reaction temperature， reaction time， and solvent type on the yields of 1-chloro-3，5-dimethoxy-2，4，6-trinitrobenzene （2）， 5，7-dimethoxy-4，6-dinitrobenzofuroxan （3）， and CL-14 were investigated. Meanwhile， CL-14·DMSO single crystals were successfully cultivated by temperature-programmed crystallization. The crystal belongs to the monoclinic system with the P2₁/n space group. The short-pulse shock initiation performance of CL-14 was tested using the Neyer D-optimality method， and the initiation threshold voltage was 1223 V， indicating a favorable shock initiation sensitivity. Under the optimized reaction conditions， the overall yield of CL-14 synthesized from starting material 1 via the three-step route was 45%， with a purity of ≥97%.

Abstract:To address the issue of the strong hygroscopicity of green high-energy oxidant ammonium dinitramide （ADN） limiting its engineering application， an ADN/hexamethylenetetramine （HMTA） cocrystal was prepared and its properties were studied. The cocrystal was synthesized using the solvent evaporation method. Its crystal structure， purity， thermal properties， energetic performance， mechanical sensitivity， and hygroscopicity were systematically characterized by single crystal X-ray diffraction （SC-XRD）， powder X-ray diffraction （PXRD）， Fourier transform infrared spectroscopy （FT-IR）， elemental analysis （EA）， simultaneous thermal analysis （TG-DSC）， oxygen bomb calorimetry， BAM impact/friction sensitivity tests and hygroscopicity tests. The 2D fingerprint was constructed with Crystalexplorer to study its intermolecular interactions. Results show that the asymmetric unit of the cocrystal contains two ADN molecules and one HMTA molecule， belonging to monoclinic crystal system with C2/c space group， and has a density of 1.564 g·cm^-3. The analysis of intermolecular interactions confirms the formation of N─H…N hydrogen bonds with shorter bond length and greater strength in the cocrystal. The cocrystal is a pure phase with a molar ratio of ADN and HMTA of 2∶1 from XRD and EA analysis. The melting point and initial decomposition temperature of the cocrystal are 130.2 ℃ and 168.5 ℃， which are 38.8 ℃ and 14.3 ℃ higher than that of ADN. The formation enthalpy of the cocrystal is -492.55 kJ·mol^-1， the theoretical specific impulse value is 201.07 s， the detonation velocity and pressure are 7854 m·s^-1 and 20.72 GPa， respectively. The friction and impact sensitivity of the cocrystal are 288 N and above 50 J， both higher than those of ADN. The hygroscopicity rate of the cocrystal is 0 after 153 h at 25 ℃ and 70% relative humidity， for ADN the hygroscopicity rate reaches to 20.95% after 48 h. The preparation of ADN/HMTA cocrystal effectively solves the problem of strong hygroscopicity of ADN.

Abstract:A novel cage-like compound tricyclo［3.3.1.0³^，⁷］nonane-2，6-dione was synthesized from bicyclic［3.3.1］non-2，6-dione through bromination， cyclization and reductive debromination. Its energetic derivative 2，2，6，6-tetranitrotricyclo［3.3.1.0³^，⁷］nonane was prepared via oximation and gem-dinitration. The structure of target compound was characterized by Fourier transform infrared spectroscopy （FT-IR）， nuclear magnetic resonance （NMR）， elemental analysis （EA）， and single crystal X-ray diffraction （SC-XRD）. The thermal stability was studied by differential scanning calorimetry （DSC） and thermogravimetric analysis （TG）. The detonation performances were predicted by EXPLO5. Results show that 2，2，6，6-tetranitrotrycyclo［3.3.1.0³^，⁷］nonane crystallizes in the monoclinic crystal system， space group P2/n with a crystal density of 1.691 g∙cm^-3. Its onset thermal decomposition temperature is 186 ℃. The theoretical detonation velocity and detonation pressure are 7319 m·s^-1 and 21.57 GPa， respectively， which are much higher than that of its adamantane-based homologue 2，2，6，6-tetranitroadamantane.

Abstract:In this study， two ferrocene-based catalysts， ［FcCH₂N（CH₃）₃⁺］［PbCl₃^-］·CH₃CN （1） and ［FcCH₂N（CH₃）₃⁺］₅［BF₄^-］₄［I^-］ （2） （where Fc= Ferrocene）， were selected as the research objects to systematically investigate and evaluate their regulatory effects on the combustion performance of solid propellants.TG-DSC tests revealed that both catalysts exhibit excellent thermal stability， with decomposition temperatures of 433.3 ℃ and 481.6 ℃， respectively. The catalytic effect of the two compounds on the thermal decomposition of ammonium perchlorate （AP） was studied via DSC. When the mass fraction of the added catalyst was 3%， compounds 1 and 2 reduced the thermal decomposition temperature of AP by 48.9 ℃ and 61.1 ℃， respectively. To further verify the practical application efficiency of the catalysts， their catalytic performance was evaluated based on a hydroxyl-terminated polybutadiene （HTPB） solid propellant formulation. When compounds 1 and 2 were incorporated into the formulation as combustion catalysts at a mass fraction of 2.5% respectively， the burning rate of the propellant increased from 4.06 mm·s^-1 to 8.99 mm·s^-1 and 9.06 mm·s^-1 under a combustion chamber pressure of 3 MPa. Within the pressure range of 3-10 MPa， the pressure exponent of the propellant decreased from 0.32 to 0.24 and 0.16， respectively.In summary， compound 2 possesses outstanding combustion catalytic performance and holds potential application prospects in high-performance solid propellant systems.

Abstract:A novel energetic material， 2，7-bis（nitroamino）bis（［1，2，4］triazolo）［1，5-b：1′，5′-e］［1，2，4，5］tetrazine-5，10-diium-3，8-diide （TYX-2）， has attracted considerable interest due to its potential for combining high energy output with low sensitivity. However， the authentic crystal structure of its neutral form remained unknown， which has hindered a thorough understanding of its intrinsic properties. High-quality single crystals of the neutral solvate TYX-2·2（C₃H₆O） were successfully obtained using an acetone/n-hexane anti-solvent method. Its crystal structure was determined by single-crystal X-ray diffractometry （SC-XRD）， and its thermal decomposition behavior was analyzed using differential scanning calorimetry （DSC） and thermogravimetry-mass spectrometry-Fourier transform infrared spectroscopy （TG-MS-FTIR）. Crystal structure analysis reveals that TYX-2·2（C₃H₆O） crystal belongs to the monoclinic system， with space group P2₁/n. The unit cell parameters are a = 10.6102（6） Å， b = 6.7134（4） Å， c = 12.3101（7） Å， and the crystal density is 1.509 g·cm^-3. TYX-2 molecules construct a stable three-dimensional supramolecular framework through extensive hydrogen bonds and significant π-π stacking interactions. Thermal analysis results indicate that the thermal decomposition peak temperature of TYX-2 is 217.5 ℃ at a heating rate of 10.0 ℃·min^-1. Its decomposition process exhibits typical autocatalytic behavior. The main gaseous decomposition products are CO₂， N₂O， HCNO， CO， and NO₂. The apparent activation energies calculated by the Kissinger method and the combined kinetic analysis method are 380.04 kJ·mol^-1 and 302.40 kJ·mol^-1， respectively. The initial stage of its solid-state thermal decomposition conforms to a two-dimensional diffusion （D2） model， which subsequently transitions to chemical reaction control.

Abstract:Under extreme high-pressure conditions， the state， crystal phase， and microstructure of explosives may undergo transformations upon impact， thereby affecting the stability and safety of weapon systems. This work focuses on the structural evolution and stability of primary explosives under extreme high pressure， with α-lead azide as the research object. Static high-pressure structural evolution was investigated by diamond anvil cell technique， in situ high-pressure synchrotron X-ray diffraction， and in situ high-pressure Raman scattering spectroscopy. The experimental results show that within the pressure range from ambient pressure to 26.6 GPa， no new diffraction or Raman peaks emerge， confirming that α-lead azide undergoes no structural phase transition. With increasing pressure， however， the spectral peaks gradually broaden and eventually disappear， indicating pressure-induced amorphization of α-lead azide. Further analysis demonstrates that α-lead azide exhibits anisotropic compression. The a- and b-axes show similar and relatively small compressibility， whereas the compression rate along the c-axis is significantly higher. The enhanced dense packing under high pressure is mainly attributed to compression along the c-axis. After full pressure quenching， the spectra do not recover to the initial state， indicating that the pressure-induced amorphization is irreversible. Such irreversible amorphization is attributed to the deformation of azide anions.

Abstract:The thermal decomposition of polymer-bonded explosives （PBX） under complex service environments represents a quintessential multiscale， multiphysics challenge. While progress has been made at individual scales， current research remains fragmented， lacking a cohesive framework that integrates molecular chemistry， mesoscopic damage evolution， and macroscopic thermo-mechanical response. This review systematically synthesizes the state-of-the-art in PBX thermal decomposition， covering methodologies， applications， and critical influencing factors. The key frontiers for future research were identified， including high-spatiotemporal-resolution in situ characterization， multiscale predictive modeling， and decomposition kinetics under confinement. Ultimately， developing physics-based life prediction models is pivotal for accurately assessing munition health and guiding the design of robust， aging-resistant formulations.