1,1'-azobis(tetrazole): a highly energetic nitrogen-rich compound with a N10 chain

The reaction of 1-aminotetrazole with acidic sodium dichloroisocyanurate allowed isolation of 1,1'-azobis(tetrazole). The rare chain of 10 nitrogen atoms in this compound was confirmed by X-ray crystallography, and the physical and explosive properties of the azo compound were characterized. The title compound possesses both exceedingly high explosive performance and sensitivity.     

Theoretical studies of furoxan-based energetic nitrogen-rich compounds

Density functional theory calculations were performed to study the effects of different substituents and nitrogen-containing heterocyclic rings on the heats of formation (HOFs), energetic properties, and thermal stability for a series of furoxan derivatives. The isodesmic reaction method was employed to calculate the HOFs of the derivatives using total energies obtained from electronic structure calculations. The detonation velocities and pressures were evaluated by using the semiempirical Kamlet–Jacobs equations, based on the theoretical densities and HOFs. The bond dissociation energies and bond orders for the weakest bonds were analyzed to investigate the thermal stability of the furoxan derivatives. These results provide basic information for the molecular design of novel high energy density materials.     

Theoretical studies of 1,2,4,5-tetrazine-based energetic nitrogen-rich compounds

Density functional theory calculations were performed to find the relationships between the structures and performance of a series of 1,2,4,5-tetrazine-based energetic derivatives. The isodesmic reaction method was employed to estimate the heats of formation (HOFs). The result shows that the azo or azoxy group is one of the most energetic functional groups known and its substitution can drastically increase HOFs of a molecule. The detonation properties were also evaluated by the Kamlet–Jacobs equations based on the theoretical densities and HOFs. Results show that NO₂ group is an effective substituent for enhancing the detonation performance. There exist better correlations between OB and detonation velocities and OB and detonation pressures. The energy gaps between the HOMO and LUMO of the studied compounds are also investigated, and from the data we estimated the relative thermal stability ordering of the title compounds.     

Simple, nitrogen-rich, energetic salts of 5-nitrotetrazole

A new family (ammonium, 1, hydrazinium, 2, guanidinium, 3, aminoguanidinium, 4, diamino-guanidinium, 5, and triaminoguanidinium, 6) of simple, nitrogen-rich energetic salts based on 5-nitro-2 H-tetrazole (HNT) were synthesized. In addition, the hemihydrate of 1 (1a) and the hydrate of 6 (6a) were also isolated. In all cases, stable salts were obtained and fully characterized by vibrational (IR, Raman) spectroscopy, multinuclear ((1)H, (13)C and (14)N) NMR spectroscopy, mass spectrometry, elemental analysis, and X-ray structure determination. Compounds 1and 2 crystallize in the monoclinic space group P2 1/c, 1a and 3 crystallize in C/2 c, 4 in P2 1/n, 5 in P2 1, 6 in orthorhombic P2 12 12 1, and 6a in triclinic P1. Initial safety testing (impact, friction, and electrostatic sensitivity) and thermal stability measurements (DSC) were also carried out. The NT salts all exhibit good thermal stabilities (decomposition above 150 degrees C). The constant volume energies of combustion (Delta c U(exp)) of 1-6 were experimentally determined by oxygen bomb calorimetry to be -1860(30) cal/g ( 1), -1770(30) cal/g ( 1a), -2110(150) cal/g (2), -2250(40) cal/g ( 3), -2470(30) cal/g (4), -2630(40) cal/g (5), -2690(50) cal/g (6), and -2520(50) cal/g (6a). Because of the significant experimental uncertainties obtained in these measurements, their validity was checked by way of quantum chemical calculation (MP2) of electronic energies and an approximation of lattice enthalpy. The predicted constant volume energies of combustion (Delta c U(pred)) calculated by this method were -2095.9 cal/g (1), -1975.7 cal/g ( 1a), -2362.4 cal/g (2), -2526.6 cal/g (3), -2654.6 cal/g (4), -2778.6 cal/g ( 5), -2924.0 cal/g (6), and -2741.4 cal/g ( 6a). From the experimentally determined density, chemical composition, and energies of formation (back calculated from the heats of combustion) the detonation pressures and velocities of 1 (7950 m/s, 23.9 GPa), 1a (7740 m/s, 22.5 GPa), 2(8750 m/s, 30.1 GPa), 3 (7500 m/s, 20.1 GPa) 4(8190 m/s, 24.7 GPa), 5(8230 m/s, 24.4 GPa), 6 (8480 m/s, 26.0 GPa) and 6a (7680 m/s, 20.7 GPa) were predicted using the EXPLO5 code.     

Amino-group excites vitality in nitrogen-rich energetic salts of triazolium

Incorporating amino groups is an efficient strategy for the tuning properties of energetic materials. However, there is no unanimous conclusion on the effect of the number of amino groups (−NH₂) on performance. Therefore, in this study, different number of −NH₂ of four energetic salts of triazolium based on oxadiazole and triazole were designed and synthesized. The structure features of energetic salts 4 – 6 were then investigated by single-crystal X-ray diffractions and Hirshfeld surfaces analyses. Afterward, the effects of −NH₂ were evaluated by thermal stability, impact sensitivity and detonation performance. All these energetic salts were insensitive to mechanical stimulation (IS >40 J), but the thermal decomposition temperatures of energetic salt 5 – 7 with −NH₂ are 24 °C to 54 °C higher than energetic salt 4 without −NH₂. Moreover, energetic salt 5 with one −NH₂ has the highest theoretical detonation properties compared to those without −NH₂ ( 4 ) and with two −NH₂ ( 6 , 7 ). These observations revealed that appropriate amount of −NH₂ can lead to desirable increase in the energetic properties, and this work can offer guidance for the design and synthesis of further energetic salts.     

A novel energetic nickel coordination compound based on carbohydrazide and dinitramide

Dinitramide was reacted with carbohydrazide to furnish the corresponding mono- and bis-susbtituted salts. The nickel salt of dinitramide when reacted with carbohydrazide produced the coordination compound, tris(carbohydrazide- N,O)nickel(ii) bis-dinitramide, whose crystal structure was characterized by X-ray diffraction.     

Thermal stability assessment of a new energetic Ca(II) compound with ZTO ligand by DSC and ARC

Journal of Thermal Analysis and Calorimetry - A new energetic Ca(H2O)6·(HZTO·2H2O)2 was crystallized in the monoclinic space group C2/c, and its thermal characteristics and kinetics were...     

Triaminoguanidinium dinitramide-calculations, synthesis and characterization of a promising energetic compound

The highly energetic compound 1,3,5-triaminoguanidinium dinitramide (1) was prepared in high yield (82%) according to a new synthesis by the reaction of potassium dinitramide and triaminoguanidinium perchlorate. The heat of formation was calculated in an extensive computational study (CBS-4M). With this the detonation parameters of compound were computed using the EXPLO5 software: D = 8796 m s(-1), p = 299 kbar. In addition, a full characterization of the chemical properties (single X-ray diffraction, IR and Raman spectroscopy, multinuclear NMR spectroscopy, mass spectrometry and elemental analysis) as well as of the energetic characteristics (differential scanning calorimetry, thermal safety calorimetry, impact, friction and electrostatic tests) is given in this work. Due to the high impact (2 J) and friction sensitivity (24 N) several attempts to reduce these sensitivities were performed by the addition of wax. The performance of was tested applying a "Koenen" steel sleeve test resulting in a critical diameter of > or =10 mm.     

Thermal degradation behaviors of a novel nanocomposite based on polypropylene and Co-Al layered double hydroxide

The thermal degradation behaviors of a novel nanocomposite based on polypropylene and organic Co/Al layered double hydroxide (PP/CoAl-LDH) were studied via thermogravimetric analysis (TGA) in the present work. The thermal degradation activation energies of the PP/CoAl-LDH nanocomposite were determined via Friedman and Flynn-Wall-Ozawa methods, and were compared with those of neat PP. The relationship between the organic CoAl-LDH concentration and the activation energies in PP/CoAl-LDH nanocomposite also has been investigated. An internal reason and an outer reason leading to high fire retardancy of PP/CoAl-LDH nanocomposite were proposed. The presence of CoAl-LDH tended to increase significantly the decomposition activation energy of nanocomposite at full-scale temperature and had an important influence on both of internal and outer reasons.     

Synthesis and structure of 2,5,8-triazido-s-heptazine: an energetic and luminescent precursor to nitrogen-rich carbon nitrides

Derivatized s-triazine (C3N3) precursors have seen significant recent use in the production of carbon nitride materials. Larger polycyclic molecular precursors, such as those containing an s-heptazine core (C6N7 or tri-s-triazine), may improve stability and order in carbon nitride products. In this Communication, we describe the synthesis and crystal structure of 2,5,8-triazido-s-heptazine (2). Synthesis of 2 was achieved from melon, an oligomeric s-heptazine synthesized by the pyrolysis of NH4SCN. Melon was converted to molecular 2,5,8-trichloro-s-heptazine, which was then transformed to the triazide upon reaction with (CH3)3SiN3. The crystal structure of 2 verifies that the s-heptazine is planar and the azides adopt a pinwheel-like C3h arrangement around the periphery. The s-heptazine core shows pi delocalization in the C-N bonds around the periphery (av. 1.33 A), while the internal planar C-N bonds are longer (1.40 A). The heptazine units pack into parallel, but offset, layered sheets in the crystal. The triazide 2 exhibits photoluminescence at 430 nm and rapidly and exothermically decomposes upon heating at 185 degrees C to produce a tan thermally stable carbon nitride powder with a formula near C3N4.     

Cocrystallization of energetic Mn(II) complex with nitrogen-rich ligand SCZ and oxygen-rich ligand TNR

Based on the advantages of energetic complexes and cocrystallization, a novel energetic complex cocrystal [Mn(SCZ)₃](TNR) (H₂O)?·?[Mn(SCZ)₂(H₂O)(TNR)](H₂O) (SCZ: semicarbazide, TNR: 2,4,6-trinitroresorcinol) was synthesized through a one-step reaction. This cocrystal contains equal units of [Mn(SCZ)₂(H₂O)(TNR)](H₂O) and [Mn(SCZ)₃]TNR(H₂O). The molecules of the two units arrange mutually crosswise in the cocrystal and the benzene rings of TNR can form one-dimensional self-assemblies through π-π stacking. The thermal decomposition of the cocrystal is complicated with one endothermic process and three exothermic processes in the DSC curve. The complex [Mn(SCZ)₂(H₂O)(TNR)]?·?3(H₂O) was synthesized and the temperature of the major exothermic peak of the cocrystal is higher than observed for this complex.     

Structural and chemical properties of the nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate under pressure

The structural and chemical properties of the bi-molecular, hydrogen-bonded, nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate C(3)H(12)N(12)O(2) (TAG-MNT) have been investigated at room pressure and under high pressure isothermal compression using powder x-ray diffraction and Raman and infrared spectroscopy. A stiffening of the equation of state and concomitant structural relaxation between 6 and 14 GPa are found to correlate with Raman mode disappearances, frequency discontinuities, and changes in the pressure dependence of modes. These observations manifest the occurrence of a reversible martensitic structural transformation to a new crystalline phase. The onset and vanishing of Fermi resonance in the nitrimine group correlate with the stiffening of the equation of state and phase transition, suggesting a possible connection between these phenomena. Beyond 15 GPa, pressure induces irreversible chemical reactions, culminating in the formation of a polymeric phase by 60 GPa.     

Thermal properties and combustion behaviors of a novel UV-curable flame retarded coating containing silicon and phosphorus

A silicon-based acrylate (SHEA) was synthesized via the reaction between 2-hydroxylethyl acrylate and dimethyldichlorosilane, and characterized by Fourier transform infrared (FTIR), ¹H NMR spectroscopy and ²⁹Si NMR spectroscopy. The SHEA was blended with phosphorus-containing tri(acryloyloxyethyl) phosphate (TAEP) at different ratios to obtain a series of UV-curable flame retarded resins. The final unsaturation conversion of the SHEA films was determined by FTIR. Their combustion behaviors were examined by microscale combustion calorimetry (MCC). The thermal degradations of TAEP/SHEA composites were characterized using thermogravimetric analysis/infrared spectrometry (TG–IR). The MCC results present that the addition of TAEP into SHEA was able to decrease the HRR, HRC, T_max and THC. Among the TAEP/SHEA resins, Si1 (TAEP:SHEA is 1:1) owns the highest initial decomposition temperature and leaves the most char residue at 800 °C. The change of chemical structure during the thermal degradation process was monitored by real-time FTIR analysis to study the condensed-phase flame retarded mechanism.     

Thermal stability and flame retardancy of novel phloroglucinol based organo phosphorus compound

A series of organo phosphorus flame retardants (FR) based on cyclic phosphates were synthesized in an attempt to find an efficient FR for polycarbonate (PC) and acrylonitrile-butadiene-styrene copolymer (ABS). The success of synthesis was confirmed by FT-IR and ¹H and ³¹P NMR. Their thermal stability and flame-retarding efficiency as a single component additive were investigated and compared with those of aromatic based phosphate, resorcinol bis(diphenyl phosphate) (RDP). Thermogravimetric analysis (TGA) results reveal that cyclic phosphates synthesized in this study show more than one-step degradation and act in the condensed phase mechanism rather than in the vapor phase mechanism. Flame-retarding efficiency was evaluated by UL-94 test method. V-0 rating was achieved at 3-5 wt% of FR loading for PC, which is better than the FR performance of RDP. The high P-OH generation tendency is responsible for the better FR performances of these compounds. The degradation path is also discussed.     

Thermal behaviors of soy biodiesel

Biodiesel is a prospective and promising fuel for diesel engines. However, some aspects need improvement, to develop into an ideal fuel, such as flow properties at low temperatures and storage stability at high temperatures with exposure to the air. Thermal analysis is an efficient tool for measuring properties, such as crystallization temperature, and thermal and oxidative stabilities. In this study, the thermal behaviors of biodiesel at low and high temperatures were investigated by using thermogravimetric analyzer, differential scanning calorimetry, pressurized differential scanning calorimetry (PDSC), and sorption analyzer (SA). The soy biodiesel was obtained through a transesterification reaction with a homogeneous catalyst. The constituents of the soy biodiesel as determined by gas chromatography show that methyl esters content was 99?% and of these 84?% were unsaturated fatty acids. TG results illustrate that the total weight loss of the biodiesel was 99?% below 300?°C under nitrogen flow, indicating a high purity biodiesel. The onset decomposition temperature and the peak temperatrue of the soy biodiesel were 193 and 225?°C, respectively, implying the biodiesel has good thermal stability. PDSC results show that the oxidation onset temperature of the soy biodiesel was 152?°C, and the oxidative induction time was 24?min. DSC results demonstrate that the onset crystallization temperature of the soy biodiesel was 1.0?°C. The SA results point out that with increasing temperature and humidity, the soy biodiesel absorbed more water, and in which humidity was the dominant factor. The water absorption and desorption of the soy biodiesel is a non-reversible process. The preferable storage conditions for soy biodiesel occur when humidity is less than 30?% and the temperature is less than 30?°C. In summary, thermal analysis is a faster alternative for thermal behavior studies as compared with conventional standard methods.     

Thermal analysis of high-temperature fast reactions in energetic materials

To get round two main difficulties of the kinetic study of fast reactions of high-temperature decomposition of energetic materials (EM) (spatial non-isothermality and self-inflammation) two new methods for sample preparation called “mechanical dilution” and “thermal dilution” were applied. In the first part of the presentation, some experimental and theoretical data on kinetics of fast high-temperature decomposition of some typical homogeneous and heterogeneous energetic materials (including pyroxylin, ammonia copper chromate, ammonium perchlorate, solid rocket propellants, and others) are given. In a number of cases, kinetic constants of fast reactions dominating at high temperatures were shown to significantly differ from those of low-temperature reactions. The second part of the presentation deals with a new method of thermal analysis—electrothermal analysis (ETA). By using a multi-channel high-speed optical pyrometer, variation of the temperature field in an electrically heated sample of conductive energetic material (or its mixture with metal powder) during its heating followed by thermal explosion is registered. Due to application of this method in the ETA-100 (allowing one to measure kinetic data at the temperature up to 3800 K with a time step as short as 0.1 ms, i.e., for full conversion times as short as 10⁻³ s) some important patterns of mechanisms of gasless combustion and explosion in SHS-mixtures (Si + C, Ni + Al, and Ti + C) were identified. More details regarding these and some additional important aspects can be found in [1, 2].     

Thermal and photoinduced valence tautomerism of a chain compound

Herein reported is an example of one-dimensional coordination polymer [CoII(3,5-DBsq)2(dpg)]·(3,5-H2DBcat)2 (1) (3,5-DBsq = 3,5-di-tert-butylsemiquinonate, 3,5-H2DBcat = 3,5-di-tert-butyl-benzene-1,2-diol, dpg = meso-alpha,beta-di(4-pyridyl)glycol) capable of undergoing thermal and photoinduced valence tautomeric transitions.     

Syntheses,crystal structures and thermodecomposition behaviors of three energetic compounds

Three new energetic compounds, nickel(II) 3,5-dinitro-2-pyridonate (Ni(2DNPO)₂(H₂O)₄, 1), copper(II) 3,5-dinitro-4-pyridonate (Cu(4DNPO)₂(H₂O)₄, 2) and cobalt(II) 3,5-dinitro-4-pyridone-N-hydroxylate ([Co(4DNPOH)₂(H₂O)₄] · 2DMF, 3 · 2DMF), were characterized by elemental analysis, FT–IR, TG-DSC and X-ray single crystal diffraction analysis. Complexes 1 and 2 are similar in structure with the metal ion coordinated by oxygen donors of four water molecules on the equatorial position and two nitrogen donors of the pyridone rings of two ligands in the axial positions. The cobalt(II) complex 3 · 2DMF is a heavily distorted octahedral geometry. The Co(II) has equatorial positions defined by oxygens of four water molecules. Its axial positions are filled with two oxygen atoms of the pyridone-N-hydroxylate of two ligands. The TG-DSC results reveal that 1 is the most stable, with higher initial thermal decomposition temperature and enthalpy. Based on the thermoanalyses, the nickel compound is a promising candidate as a component in catalyzed RDX-CMDB propellants in comparison with our earlier lead(II) analogs.