Krishnamurthi Muralidharan

Tetraanionic Nitrogen‐Rich Tetrazole‐Based Energetic Salts

1,1,3,3-Tetra(1H-tetrazol-5-yl)propane-based energetic salts were synthesized in a simple and straightforward manner. The structures of these new salts were determined by (1)H and (13)C NMR spectroscopy, IR spectroscopy, MS, and elemental analysis. All of these compounds showed good thermal stabilities above 180 °C, as confirmed by thermogravimetric-differential thermal analysis (TG-DTA) measurements. Moreover, these salts also exhibited high positive enthalpies of formation, high nitrogen content, good thermal stabilities, and moderate detonation properties.

Synthesis of nitrogen-rich imidazole, 1,2,4-triazole and tetrazole-based compounds

Imidazole, 1,2,4-triazole and tetrazole based molecules were prepared for their possible applications in nitrogen-rich gas generators. The energetic salts of 1-(1H-1,2,4-triazol-3-yl)-1H-tetrazole (9), 5-(1H-tetrazol-1-yl)-1H-1,2,4-triazol-3-amine (10), 1-(3-azido-1H-1,2,4-triazol-5-yl)-1H-tetrazole (11) and 3-azido-1H-1,2,4-triazol-5-amine (12) were prepared with various cationic moieties. Their densities, heats of formation, chemical energy of detonation, detonation velocities and pressures were calculated. All of the compounds possessed high positive heats of formation due to high energy contribution from the molecular backbone of the corresponding compounds. The effect of the azole rings and nitro, amino, and azido groups on their physicochemical properties was examined and discussed.

Synthesis of amino, azido, nitro, and nitrogen-rich azole-substituted derivatives of 1H-benzotriazole for high-energy materials applications.

The amino, azido, nitro, and nitrogen-rich azole substituted derivatives of 1H-benzotriazole have been synthesized for energetic material applications. The synthesized compounds were fully characterized by (1)H and (13)C NMR spectroscopy, IR, MS, and elemental analysis. 5-Chloro-4-nitro-1H-benzo[1,2,3]triazole (2) and 5-azido-4,6-dinitro-1H-benzo[1,2,3]triazole (7) crystallize in the Pca2(1) (orthorhombic) and P2(1)/c (monoclinic) space group, respectively, as determined by single-crystal X-ray diffraction. Their densities are 1.71 and 1.77 g cm(-3), respectively. The calculated densities of the other compounds range between 1.61 and 1.98 g cm(-3). The detonation velocity (D) values calculated for these synthesized compounds range from 5.45 to 8.06 km s(-1), and the detonation pressure (P) ranges from 12.35 to 28 GPa.

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.

Hexamethyldisilazane-assisted synthesis of indium sulfide nanoparticles

We report the synthesis of tetragonal β-In2S3 nanoparticles (NPs). The present approach is intended to produce volatile side products to achieve organic molecule-free NPs for better optoelectronic applications. The obtained NPs possess a bulk tetragonal structure with an average size of 8.08 ± 3.76 nm. The expected quantum confinement was observed in a spectrochemically determined band gap (2.45 eV). A surprising finding is that these NPs showed a broad solid state emission (500–800 nm) with a FWHM of 197 nm.

Energetic salts prepared from phenolate derivatives

Several organic salts with 1 : 1, 2 : 1, and 3 : 1 charge ratios (cation : anion) based on various cations and phenolate anions have been prepared. Their structures were characterized and confirmed by 1H, 13C NMR, DEPT spectroscopy, IR spectroscopy, MS and elemental analysis. Picric acid, 2,4,6-trinitro-m-cresol, 3-azido-2,4,6-trinitrophenol, styphnic acid, 2,4,6-trinitro-1,3,5-benzenetriol, and their salts were synthesized by a straightforward and simple method. Thermal stabilities were determined from thermogravimetric differential thermal analysis (TG-DTA) measurements. Molecular structures of nitrophenols and their salts were investigated at the B3PW91/6-31G(d,p) level, and isodesmic reactions were designed for calculating the gas phase heats of formation. The solid state heats of formation for nitrophenols and selective nitrogen-rich heterocyclic compounds were calculated by the Politzer approach using heats of sublimation. Lattice potential energies and lattice energies of salts were predicted using the Jenkins approach. Finally, the influence of nitrophenols, nitrogen-rich heterocyclic compounds and their salts on the energetic properties has been discussed.

Effect of Copper Oxide, Titanium Dioxide, and Lithium Fluoride on the Thermal Behavior and Decomposition Kinetics of Ammonium Nitrate

Ammonium nitrate (AN) is crystallized along with copper oxide, titanium dioxide, and lithium fluoride. Thermal kinetic constants for the decomposition reaction of the samples were calculated by model-free (Friedmans differential and Vyzovkins nonlinear integral) and model-fitting (Coats-Redfern) methods. To determine the decomposition mechanisms, 12 solid-state mechanisms were tested using the Coats-Redfern method. The results of the Coats-Redfern method show that the decomposition mechanism for all samples is the contracting cylinder mechanism. The phase behavior of the obtained samples was evaluated by differential scanning calorimetry (DSC), and structural properties were determined by X-ray powder diffraction (XRPD). The results indicate that copper oxide modifies the phase transition behavior and can catalyze AN decomposition, whereas LiF inhibits AN decomposition, and TiO2 shows no influence on the rate of decomposition. Possible explanations for these results are discussed. Supplementary materials are available for this article. Go to the publishers online edition of the Journal of Energetic Materials to view the free supplemental file.

S4N4 as an intermediate in Ag2S nanoparticle synthesis

In the present work, hexamethyldisilazane assisted synthesis of Ag2S nanoparticles is demonstrated. Classical chemical investigations and nano investigations were utilized to explain the formation of nanoparticles. Controlled reactions were performed to explain the reaction mechanism. While establishing the reaction mechanism, the formation of Ag nanoparticles and tetrasulfur tetranitride (S4N4) was identified. Observations of a controlled reaction explained that sulfur reduction occurred through a S–N polymeric intermediate. Then, the polymeric intermediate was decomposed to tetrasulfur tetranitride. The formation of S4N4 was unambiguously confirmed by single crystal X-ray diffraction measurements. The formation of S4N4 also confirmed the role of hexamethyldisilazane as a reductant. Obtained nanoparticles were characterised by PXRD, EDAX, FTIR, FESEM, TEM, HRTEM and UV measurements.

High energy density materials from azido cyclophosphazenes

Azido substituted cyclophosphazenes were prepared and their standard heats of formation were calculated based on experimentally determined heats of combustion.

Versatile metal complexes of 2,5-bis{N-(2,6-di isopropylphenyl)iminomethyl}pyrrole for epoxide–CO2 coupling and ring opening polymerization of ε-caprolactone

The catalytic activities of metal complexes of 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrole 1 for epoxide–CO2 coupling and ring opening polymerization (ROP) of e-caprolactone (CL) were explored. The Zn(II) 2, Cd(II) 3,4 and Cu(II) 5 complexes of 1, in the presence of tetrabutylammonium bromide (TBAB) as co-catalyst, effectively catalyzed the epoxide–CO2 coupling reaction at 1 atm of CO2 to produce cyclic carbonates. In addition, the catalytic activities of these complexes (2–5) were investigated for the ROP of CL in the presence and absence of benzyl alcohol (BnOH). All these complexes were active for ROP of CL at mild temperature. In particular, the complexes 2 and 5 exhibited remarkable catalytic activities for ROP of CL at 25 °C in toluene in the presence of BnOH. The ROP of CL catalyzed by 2 and 5 complexes, not only proceeded through living polymerization but also immortal.