Yuchuan Li

A novel stable high-nitrogen energetic material: 4,4′-azobis(1,2,4-triazole)

A novel high-nitrogen compound with an N,N′-azo linkage, 4,4′-azobis(1,2,4-triazole), has been synthesized and well characterized. The solid-state structure was determined by X-ray diffraction. The experimentally determined density and enthalpy of formation matched with theoretically computed values based on the B3LYP method. The DSC result suggests that 4,4′-azobis(1,2,4-triazole) decomposes at a relatively high temperature (313.36 °C). By comparison with 3,3′-azobis(1,2,4-triazole), containing a C,C′-azo linkage, the N,N′-azo linkage was found to provide compounds with a relatively high density and high energy.

Energetic salts based on 1-amino-1,2,3-triazole and 3-methyl-1-amino-1,2,3-triazole

High-density energetic salts that contain nitrogen-rich anions and the 1-amino-1,2,3-triazole (ATZ) or 3-methyl-1-amino-1,2,3-triazole (MAT) cation were synthesized. All salts were fully characterized by IR spectroscopy, multinuclear (1H, 13C) NMR spectroscopy, differential scanning calorimetry (DSC), and impact sensitivity. 1-Amino-1,2,3-triazolium 5-nitrotetrazolate, 3-methyl-1-amino-1,2,3-triazolium 5-nitrotetrazolate, and 3-methyl-1-amino-1,2,3-triazolium azotetrazolate crystallize in the triclinic space group P, as determined by single-crystal X-ray diffraction. Their densities are 1.688, 1.588, and 1.550 g cm−3, respectively. The measured densities of the other organic energetic salts range between 1.56 and 1.86 g cm−3. The detonation pressure (P) values calculated for these salts range from 21.2 to 37.3 GPa, and the detonation velocities (D) range from 7239 to 9082 m s−1, making the salts potentially energetic materials.

Nitrogen-rich salts based on 5-hydrazino-1H-tetrazole: a new family of high-density energetic materials

High-density energetic salts that contain nitrogen-rich anions and the 5-hydrazino-1H-tetrazolium cation were synthesized. All salts were fully characterized by vibrational spectroscopy (IR), multinuclear (1H, 13C) NMR spectroscopy, elemental analysis, differential scanning calorimetry (DSC), and impact sensitivity. Four compounds were characterized by single X-ray diffraction. The results show that the extensive hydrogen bonding interactions between the cations and anions form a complex 3D network, which contributes greatly to the high density of the 5-hydrazinotetrazolium salts. It was also found that the incorporation of hydrazino groups into a heterocyclic ring increases the heat of formation and overall nitrogen content of the entire molecule. Some of these salts exhibit reasonable physical properties, such as good thermal stability (Td = 173.7–198.6 °C), reasonable impact sensitivities (IS = 4–40 J), and excellent specific impulses (Isp = 196.1–288.7 s). In addition, detonation properties of the energetic salts obtained with EXPLO 5.05 identify them as competitively energetic compounds, and in some cases are superior to those of HMX.

Nitrogen-rich salts based on polyamino substituted N,N′-azo-1,2,4-triazole: a new family of high-performance energetic materials

A new family of nitrogen-rich energetic salts based on 3,3′-diamino-4,4′-azo-1,2,4-triazole containing an N,N′-azo linkage has been synthesized and fully characterized by IR, 1H and 13C NMR spectrum, elemental analysis, differential scanning calorimetry (DSC) and sensitivities toward impact, friction and electrostatics. The crystal structures of chloride 2, nitrate 3, perchlorate 4 and isomerization product 10 have been determined by single-crystal X-ray diffraction analysis. All the salts exhibit high thermal stabilities with decomposition temperatures of over 200 °C, except for nitroformate 6. The measured densities of salts 2–7 fall in the range of 1.71 to 1.99 g cm−1. Theoretical performance calculations (Gaussian 03 and EXPLO5) provided detonation pressures and velocities for energetic salts in the ranges 26.3 to 45.7 GPa and 8042 to 9580 m s−1, respectively. Moreover, these salts exhibit reasonable impact sensitivities (IS = 8–40 J) and friction sensitivities (FS = 90–360 N); these salts also exhibit excellent thermal stabilities, high detonation properties and reasonable sensitivities, which, in some cases, are superior to those of TNT, TATB and HMX, and present a favorable balance between the energy and stability of energetic materials. In addition, these salts exhibit excellent specific impulses (265 to 301 s), which make them competitive energetic materials.

Energetic Salts Based on an Oxygen-Containing Cation: 2,4-Diamino-1,3,5- triazine-6-one

A family of energetic salts with high thermal stability and low impact sensitivity based on an oxygen-containing cation, 2,4-diamino-1,3,5-triazine-6-one, were synthesized and fully characterized by IR and multinuclear ((1)H, (13)C) NMR spectroscopy, elemental analysis, and differential scanning calorimetry. Insights into their sensitivities towards impact, friction, and electrostatics were gained by submitting the materials to standard tests. The structures of 2,4-diamino-1,3,5-triazine-6-one nitrate, 2,4-diamino-1,3,5-triazine-6-one sulfate, 2,4-diamino-1,3,5-triazine-6-one perchlorate, 2,4-diamino-1,3,5-triazine-6-one 5-nitrotetrazolate were determined by single-crystal X-ray diffraction; their densities are 1.691, 1.776, 1.854, and 1.636 g cm(-3), respectively. Most of the salts decompose at temperatures over 180 °C; in particular, the salts 2,4-diamino-1,3,5-triazine-6-one nitrate and 2,4-diamino-1,3,5-triazine-6-one perchlorate, which decompose at 303.3 and 336.4 °C, respectively, are fairly stable. Furthermore, most of the salts exhibit excellent impact sensitivities (>40 J), friction sensitivities (>360 N), and are insensitive to electrostatics. The measured densities of these energetic salts range from 1.64 to 2.01 g cm(-3) . The detonation pressure values calculated for these salts range from 14.6 to 29.2 GPa, and the detonation velocities range from 6536 to 8275 m s(-1) ; these values make the salts potential candidates for thermally stable and insensitive energetic materials.

Synthesis and Characterization of 5-Nitro-2-nitratomethyl- 1,2,3,4-tetrazole: A High Nitrogen Energetic Compound with Good Oxygen Balance

The synthesis of 5-nitro-2-nitratomethyl-1,2,3,4-tetrazole (4) and its full characterization are given here. Compound 4 was synthesized through the nitration of 5-nitro-2-hydroxymethyl-tetrazole (3) with fuming nitric acid and acetic anhydride and its structure was characterized by MS, FT-IR, 1H-NMR and 13C-NMR techniques. The crystal structure of 4 was determined by X-ray single crystal diffraction analysis. The compound belongs to the orthorhombic system with space group Pna2(1), and its crystal parameters were a = 2.121(8) nm, b = 0.5281(19) nm, c = 0.6246(2) nm, Z = 4, V = 0.6995(4) nm3, Dc = 1.805 g/cm3, F(000) = 384, μ = 0.174 mm−1. A theoretical study of 4 has been performed, using quantum computational density functional theory (B3LYP methods) with 6-31G* basis sets as implemented in the Gaussian 03 program suite. The obtained heat of formation (HOF) for 4 was 228.07 kJ·mol−1, the detonation pressure (P) values calculated for 4 was 37.92 GPa, the detonation velocity (D) can reach 9260 m·s−1, and the oxygen balance was zero (Q), making 4 a competitive energetic compound.

A comparative study of the structure, energetic performance and stability of nitro-NNO-azoxy substituted explosives

2,4-Dinitro-NNO-azoxytoluene and 2,6-dinitro-4-nitro-NNO-azoxytoluene were synthesized as energetic compounds. Their structures and properties were studied by X-ray diffractometry, nuclear magnetic resonance and infrared spectroscopy. The differences between the nitro-NNO-azoxy and nitro groups are discussed. The detonation properties, as predicted using EXPLO5, indicate that the detonation velocity and pressure of 2,4-dinitro-NNO-azoxytoluene were greater by 21.7% and 74.3%, respectively, than those of 2,4-dinitrotoluene. Nucleus independent chemical shift analysis was used to investigate skeleton aromaticity and the effect of the nitro-NNO-azoxy and nitro groups on ring aromaticity. Electrostatic potential, bond dissociation energy, Mulliken charges and Wiberg bond order were estimated by density functional theory to establish the molecular electron distribution and stabilities of the compounds. The nitro-NNO-azoxy group has a stronger electron-withdrawing property than that of the nitro group.

A flexible conductive film prepared by the oriented stacking of Ag and Au/Ag alloy nanoplates and its chemically roughened surface for explosive SERS detection and cell adhesion

A large-scale assembly of nanostructured building blocks into bulk flexible film with multifunctional applications is the key point in colloidal nanomaterials research. In this study, a centimeter-scale flexible conductive film was prepared by the oriented stacking of Ag nanoplates on a polyethylene glycol terephthalate (PET) flexible substrate and it displayed an ideal ohmic contact and low resistance (112 Ω cm−1). Via a solid–liquid interface galvanic replacement reaction with HAuCl4, a Au–Ag alloy nanoplate film was obtained with an enhanced conductivity (10.2 Ω cm−1) and controllable surface roughness. The optimized surface roughness of this flexible conductive film enabled the ultrasensitive surface-enhanced Raman spectroscopy (SERS) detection of explosives (TNT and RDX) and their differentiation at low concentrations (10 nM). Moreover, the synergistic nanoscale and microscale surface roughness of this Au–Ag alloy nanoplate film endowed good biocompatibility and demonstrated applicable biological cell adhesion performance.

Thermal stability of p-dimethylaminophenylpentazole

The thermal stability of p-dimethylaminophenylpentazole (1) in the solid phase has been thoroughly investigated. The decomposition process of 1 has been verified by a combination of differential scanning calorimetry (DSC), thin-layer chromatography (TLC), temperature-programmed FTIR, and Raman spectroscopy. FTIR and Raman spectra were also calculated to corroborate the results. It was found that 1 could be handled below 20 °C without any obvious deterioration, but it decomposed sharply at 56 °C. The calculated FTIR and Raman vibrational frequencies were in accord with the experimental values.

Novel [NF2O]+ and [N3NFO]+-based energetic oxidizers for solid propellants with super high specific impulse

Novel [NF2O]+ and [N3NFO]+-based energetic oxidizers were designed, and their structures, thermal stabilities, and energetic properties were investigated via density functional theory (DFT). The analysis of the bond dissociation energies (from 93.4 to 120.8 kcal mol−1) for the screened salts suggests that they possess better thermal stabilities than the reported [NF2O]+SbF6− (89.8 kcal mol−1), and compound 5 was the most stable energetic salt. All the screened salts possess a positive oxygen balance ranging from 13% to 50%. Due to a positive oxygen balance, the specific impulses of the compounds 5, 11–14 (>300 s) were superior to those of ammonium perchlorate (AP) and ammonium dinitramide (ADN) when the optimized ratio of oxidizer/aluminium/PBAN (%) was 76 : 10 : 14. Considering their thermal stability and chemical reactivity, compounds 5 and 11 with super high specific impulses can be regarded as excellent candidates for novel potential solid propellants.