New technology for preparing energetic materials by nanofiltration membrane (NF): rapid and efficient preparation of high-purity ammonium dinitramide (ADN).

The development of environment-friendly and non-toxic green energetic materials and their safe, environmentally friendly, and economical production is very important to the national economy and national security. As an innovative, efficient, and environmentally friendly energetic material, the preferred preparation method of ammonium dinitramide (ADN) is the nitro-sulfur mixed acid method, which has the advantages of high yield, simple method, and easy access to raw materials. However, the large number of inorganic salt ions introduced by this method limits the large-scale production of ADN. Nanofiltration (NF) has been widely used in various industrial processes as a separation method with high separation efficiency and simple operation. In this study, NF was used for the desalination and purification of ADN synthesized by the mixed acid method. The effects of NF types, operation process (pressure, temperature, and feed solution concentration) on desalination efficiency, and membrane flux during purification were examined. The results showed that 600D NF could achieve the efficient desalination and purification of ADN. It was verified that the highest desalination and purification efficiency was achieved at 2 MPa pressure, 25 °C, and 1 time dilution of the feed solution, and the membrane flux of the desalination and purification process was stable. Under the optimized process conditions, the removal rate of inorganic salts and other impurities reached 99% (which can be recycled), the purity of ADN reached 99.8%, and the recovery rate reached 99%. This process has the potential for the large-scale production of ADN and provides a new process for the safe, efficient, and cheap preparation of energetic materials.

Synthesis and characterization of potential polycyclic energetic materials using bicyclic triazole and azetidine structures as building blocks.

Exploring the design strategy of new energetic materials is crucial to promote the development of energetic materials. In this study, a method for designing polycyclic energetic materials is proposed by combining the azetidine structure with azobis-1,2,4-triazole or bi-1,2,4-triazole. A series of typical triazolyl polycyclic compounds were designed and synthesized by simple nucleophilic reaction, which included 5,5'-dichloro-3,3'-bis(3,3'-difluoroazetidine)-4,4'-azobis-1,2,4-triazole (1), 5,5'-dichloro-3,3'-bis(3,3'-difluoroazetidine)-4,4'-bi-1,2,4-triazole (2), 5,5'-dichloro-3-(N,N-dimethyl)-3'-(3,3'-difluoroazetidine)-4,4'-bi-1,2,4-triazole (3) 5,5'-dichloro-3,3'-bis(3,3'-dinitroazetidine)-4,4'-bi-1,2,4-triazole (4), 5,5'-dichloro-3-(N,N-dimethyl)-3'-(3,3'-dinitroazetidine)-4,4'-bi-1,2,4-triazole (5), and 5,5'-diazido-3,3'-bis(3,3'-difluoroazetidine)-4,4'-azo-1,2,4-triazole (6). These designed and synthesized polycyclic compounds (1, 2, 3) have high decomposition temperatures (>200 °C). The molecular van der Waals surface electrostatic potentials suggested the reactivity of compounds 1, 2, and 3 when attacked by nucleophiles. The natural bond orbital and Hirshfeld surface analysis proved the essential reason for the stability of these compounds in theory. The formula design example suggests that some triazolyl polycyclic compounds (4, 5, and 6) are potentially explosives, suggesting that this strategy is feasible for constructing the triazolyl polycyclic energetic compounds.

Joint experimental and theoretical studies of the surprising stability of the aryl pentazole upon noncovalent binding to ß-cyclodextrin.

Herein, binding of the ß-cyclodextrin (ß-CD) host to the unstable aryl pentazole guest has been confirmed experimentally and theoretically. After the confinement of aryl pentazole, electron density reorganization was studied by M06-2X dispersion-corrected DFT and further reflected in the characteristic shift in the NMR spectra. Among the host-guest complexes, the inclusion complex is favored with the phenyl ring expectedly encapsulated within the cavity through noncovalent interactions such as hydrogen bonding, C-Hπ, and the special Csp2-HH-Csp3 bonding discovered by the NBO, QTAIM, and NCI-RDG theories. The host-guest binding renders the enhancement of the nitrogen-ring aromatic character; this has been analyzed by employing nucleus-independent chemical shift (NICS)-based profiles. The non-covalent interaction largely enhances the thermal stability of the guest through a change of the decomposition reaction path whether the guest is encapsulated or not by the host. By comparison of the structures of B1-B4, the enhancement could be assigned to the ion-type transition structure stabilized by the C-H bonds of the host.

Highly energetic compositions based on functionalized carbon nanomaterials.

In recent years, research in the field of carbon nanomaterials (CNMs), such as fullerenes, expanded graphite (EG), carbon nanotubes (CNTs), graphene, and graphene oxide (GO), has been widely used in energy storage, electronics, catalysts, and biomaterials, as well as medical applications. Regarding energy storage, one of the most important research directions is the development of CNMs as carriers of energetic components by coating or encapsulation, thus forming safer advanced nanostructures with better performances. Moreover, some CNMs can also be functionalized to become energetic additives. This review article covers updated preparation methods for the aforementioned CNMs, with a more specific orientation towards the use of these nanomaterials in energetic compositions. The effects of these functionalized CNMs on thermal decomposition, ignition, combustion and the reactivity properties of energetic compositions are significant and are discussed in detail. It has been shown that the use of functionalized CNMs in energetic compositions greatly improves their combustion performances, thermal stability and sensitivity. In particular, functionalized fullerenes, CNTs and GO are the most appropriate candidate components in nanothermites, solid propellants and gas generators, due to their superior catalytic properties as well as facile preparation methods.

Solid-state Reaction of Azolium Hydrohalogen Salts with Silver Dicyanamide--Unexpected Formation of Cyanoguanidine-azoles, Reaction Mechanism and Their Hypergolic Properties.

Cyanoguanidines as well as azoles are important bioactive groups, which play an important role in the medical application; meanwhile, the high nitrogen content makes them excellent backbones for energetic materials. A Novel and simple method that combined these two fragments into one molecular compound was developed through the transformation of dicyanamide ionic salts. In return, compounds 4-11 were synthesized, and fully characterized by IR, MS, NMR and elemental analysis. Meanwhile, the structures of compounds 4, 8 and 11 were confirmed by X-ray crystal diffraction. Detailed reaction mechanisms were studied through accurate calculations on the reaction energy profiles of the azolium cations and DCA anion, which revealed the essence of the transformation proceeding. Meanwhile, compound 8 exhibits excellent hypergolic property, which could be potentially novel molecular hypergolic fuel.

A Highly Energetic N-Rich Zeolite-Like Metal-Organic Framework with Excellent Air Stability and Insensitivity.

A stable N-rich aromatic ligand is employed to prepare energetic zeolite-like metal-organic frameworks. IFMC-1 shows excellent air stability, and the lowest sensitivity toward impact, friction, and electrostatic discharge and the highest predicted heat of detonation among the reported coordination polymers, and even commercial materials (such as trinitrotoluene (TNT)).

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.

Trinitromethyl/trinitroethyl substituted CL-20 derivatives: structurally interesting and remarkably high energy.

A series of trinitromethyl/trinitroethyl substituted derivatives of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5,5,0, 0(3.11),0(5.9)] dodecane (CL-20) were designed and investigated by theoretical methods. Intramolecular interactions between the trinitromethyl/trinitroethyl and the cage were investigated. The effects of trinitromethyl/trinitroethyl groups on stability of the parent compound are discussed. The results reveal a mutual influence of bond length and dihedral angle between the trinitromethyl and the cage. Compared to CL-20, the sensitivity of derivatives is barely affected. Properties such as density, heat of formation and detonation performance of these novel compounds were also predicted. The introduction of the trinitromethyl group can significantly enhance the oxygen balance, density and detonation properties of the parent compound. The remarkable energy properties make these novel cage compounds competitive high energy density materials.

Synthesis and promising properties of a new family of high-nitrogen compounds: polyazido- and polyamino-substituted N,N'-azo-1,2,4-triazoles.

A new family of high-nitrogen compounds, that is, polyazido- and polyamino-substituted N,N'-azo-1,2,4-triazoles, were synthesized in a safe and convenient manner and fully characterized. The structures of 3,3',5,5'-tetra(azido)-4,4'-azo-1,2,4-triazole (15) and 3,3',5,5'-tetra(amino)-4,4'-azo-1,2,4-triazole (23) were also confirmed by X-ray diffraction. Differential scanning calorimetry (DSC) was performed to determine their thermal stability. Their heats of formation and density, which were calculated by using Gaussian 03, were used to determine the detonation performances of the related compounds (EXPLO 5.05). The heats of formation of the polyazido compounds were also derived by using an additive method. Compound 15 has the highest heat of formation (6933 kJ kg(-1)) reported so far for energetic compounds and a detonation performance that is comparable to that of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), while compound 23 has a decomposition temperature of up to 290 °C.

Theoretical investigation of 4,4',6,6'-tetra(azido)azo-1,3,5-triazine-N-oxides and the effects of N→O bonding on organic azides.

A family of 4,4',6,6'-tetra(azido)azo-1,3,5-triazine-N-oxides was designed and investigated by theoretical method. The effects of the N→O bond on the properties of TAAT-N-oxides, such as density, heat of formation, and detonation performance, were discussed. By comparison with the bond-dissociation energy of the weakest bond and the electrostatic potentials, the effects of the N→O bond on the stability and impact sensitivity of organic azides were also discussed. The results show that the introduction of N→O bonds at the appropriate positions increases the oxygen balance and density of the compounds, while it has little effect on the stability and impact sensitivity. Consequently, their introduction results in energetic compounds with improved detonation performances.

1,1'-Azobis-1,2,3-triazole: a high-nitrogen compound with stable N8 structure and photochromism.

Treatment of 1-amino-1,2,3-triazole with sodium dichloroisocyanurate led to isolation of 1,1'-azobis-1,2,3-triazole, which was well characterized. Its structure was determined by X-ray crystallographic analysis, and its thermal stability and photochromic properties were investigated.