Octanitropyrazolopyrazole: a gem-trinitromethyl based green high-density energetic oxidizer.

Environmental concerns demand the replacement of ammonium perchlorate (AP) by a green oxidizer in composite propellants. Herein, we report the synthesis and characterization of a novel green high-density energetic oxidizer octanitropyrazolopyrazole (ONPP). With its high specific impulse (256 s), high density (1.997 g cm-3) and good thermal stability (160 °C), ONPP can potentially replace AP.

Decomposition Mechanism of Hexanitrohexaazaisowurtzitane (CL-20) by Coupled Computational and Experimental Study.

A novel degradation pathway of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) was identified using computational and experimental methods. Density functional theory (DFT) calculations were employed to obtain its unimolecular degradation pathway, and ultrahigh-performance liquid chromatography-high-resolution mass spectrometry, thermogravimetry-Fourier transform infrared spectrometry, thermogravimetry, and differential scanning calorimetric experimental data were used to validate the computationally deduced degradation pathways. Based on the indications from computational and experimental results, the cleavage of the strained fragment from CL-20 was identified instead of NO2 or HONO elimination as in conventional high energy materials. This fragmentation results in the formation of two energetic species, dinitrodihydropyrazine and dinitroformimidamide, which makes CL-20 one of the most powerful energetic materials. This novel degradation pathway of CL-20 will be useful in understanding the decomposition of cage molecules, design of new practical energetic molecules, and development/improvement of thermokinetic codes used for energetic property calculations.

New High Pressure Phases of Energetic Material TEX: Evidence from Raman Spectroscopy, X-ray Diffraction, and First-Principles Calculations.

Samples of energetic material TEX (C6H6N4O8) are studied using Raman spectroscopy and X-ray diffraction (XRD) up to 27 GPa pressure. There are clear changes in the Raman spectra and XRD patterns around 2 GPa related to a conformational change in the TEX molecule, and a phase transformation above 11 GPa. The molecular structures and vibrational frequencies of TEX are calculated by density functional theory based Gaussian 09W and CASTEP programs. The computed frequencies compare well with Raman spectroscopic results. Mode assignments are carried out using the vibrational energy distribution analysis program and are also visualized in the Materials Studio package. Raman spectra of the high pressure phases indicate that the sensitivity of these phases is more than that of the ambient phase.

Dendritic Polynitrato Energetic Motifs: Development and Exploration of Physicochemical Behavior through Theoretical and Experimental Approach.

Considering the fundamental and most desirable characteristics of energetic materials, a series of 1,2,3-triazole-based heterocyclic energetic motifs nicely tuned with nitrato (-ONO2) functionality were synthesized by a microwave-assisted environmental friendly synthetic approach with good yields. Thermal stability and the nature of evolved gases on decomposition of structurally characterized energetic motifs were analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) analysis and Fourier transform infrared coupled with TGA-DSC. The explosiveness of these motifs was explored by calculation of enthalpy of formation and density employing density functional theory, and the detonation performances (detonation pressure and velocity) were explored using EXPLO5_V6.03. All of these compounds were calculated to have better oxygen balance (-36 to -52%) as compared to that of trinitrotoluene (-74%). Most of the nitrate ester derivatives were found to exhibit low impact sensitivities, high densities, good thermal stabilities, and promising detonation properties, and PN 3 was observed to be a superior candidate in terms of its energetic characteristics. Hence, the experimental and theoretical outcomes strongly reflect that the present approach of developing dendritic high energetic materials bearing green explosive characteristics might be a potential pathway for designing and synthesizing green explosives with desired characteristics.

Anatase-brookite mixed phase nano TiO2 catalyzed homolytic decomposition of ammonium nitrate.

Compared to the conventional ammonium perchlorate based solid rocket propellants, burning of ammonium nitrate (AN) based propellants produce environmentally innocuous combustion gases. Application of AN as propellant oxidizer is restricted due to low reactivity and low energetics besides its near room temperature polymorphic phase transition. In the present study, anatase-brookite mixed phase TiO(2) nanoparticles (~ 10 nm) are synthesized and used as catalyst to enhance the reactivity of the environmental friendly propellant oxidizer ammonium nitrate. The activation energy required for the decomposition reactions, computed by differential and non-linear integral isoconversional methods are used to establish the catalytic activity. Presumably, the removal of NH(3) and H(2)O, known inhibitors of ammonium nitrate decomposition reaction, due to the surface reactions on active surface of TiO(2) changes the decomposition pathway and thereby the reactivity.

Use of potassium ferrocyanide as habit modifier in the size reduction and phase modification of ammonium nitrate crystals in slurries.

Ammonium nitrate (AN) is an inorganic crystalline compound used as a solid propellant oxidizer and as a nitrogenous fertilizer. The practical use of AN as solid propellant oxidizer is restricted due to the near room temperature polymorphic phase transition and hygroscopicity. A good deal of effort has been expended for last many years to stabilize the polymorphic transitions of AN, so as to minimize the storage difficulties of AN based fertilizers and to achieve more environmentally benign propellant systems. Also, particles with aspect ratio nearer to one are a vital requirement in fertilizer and propellant industries. In the present study AN is crystallized in presence of trace amount of potassium ferrocyanide (K(4)Fe(CN)(6)) crystal habit modifier and kept for different time intervals. And the effect of K(4)Fe(CN)(6) on the habit and phase modification of AN was studied. Phase modified ammonium nitrate (PMAN) with a particle aspect ratio nearer to one was obtained by this method and the reasons for this modifications are discussed. The morphology changes were studied by SEM, the phase modifications were studied by DSC and the structural properties were studied by powder XRD.

Effect of method of crystallization on the IV-III and IV-II polymorphic transitions of ammonium nitrate.

A study has been undertaken on the effect of crystallization method on the IV<-->III transition of ammonium nitrate (AN). AN is crystallized in three different ways, viz. recrystallization, evaporative crystallization and melt crystallization. When the samples were crystallized from saturated aqueous solution, ideal crystals were formed, which behaved differently from the crystals formed from the other methods. The DTA examination of the crystals showed that the crystals have different transition behaviour. The moisture uptake of the samples determined were found to have influenced by the mode of crystallization. The samples were further analyzed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The present study showed that the parameters like thermal history, number of previous transformations and moisture content have a very negligible influence on the IV<-->III transition of AN as compared to the method of crystallization.