Arun K. Sikder

Environmentally compatible next generation green energetic materials (GEMs).

This paper briefly reviews the literature work reported on the environmentally compatible green energetic materials (GEMs) for defence and space applications. Currently, great emphasis is laid in the field of high-energy materials (HEMs) to increase the environmental stewardship along with the deliverance of improved performance. This emphasis is especially strong in the areas of energetic materials, weapon development, processing, and disposal operations. Therefore, efforts are on to develop energetic materials systems under the broad concept of green energetic materials (GEMs) in different schools all over the globe. The GEMs program initiated globally by different schools addresses these challenges and establishes the framework for advances in energetic materials processing and production that promote compliance with environmental regulations. This review also briefs the principles of green chemistry pertaining to HEMs, followed by the work carried out globally on environmentally compatible green energetic materials and allied ingredients.

Important aspects of behaviour of organic energetic compounds: a review.

The importance of a prediction tool increases with greater relevance for synthesis, performance and vulnerability predictions. Some important aspects of performance behaviour and their theoretical calculations, which are indispensable in recognising energetic molecules of interest, are described here. This review also discusses on factors influencing sensitivity and overall stabilities of organic energetic compounds especially on nitroaromatics and nitramines, and exceptions to this relationship suggest other factors playing roles in specific instances.

Synthesis and characterization of 3,6-bis(1H-1,2,3,4-tetrazol-5-ylamino)-1,2,4,5-tetrazine (BTATz): Novel high-nitrogen content insensitive high energy material

This paper reports the synthesis, characterization and thermolysis studies of 3,6-bis(1H-1,2,3,4-tetrazol-5-ylamino)-1,2,4,5-tetrazine (BTATz) and 3-(1H-1,2,3,4-tetrazol-5-ylamino)-6-(3,5-dimethyl-pyrazol-1-yl)-s-tetrazine monohydrate (TADPTz). The synthesized BTATz and TADPTz have been characterized by spectroscopic techniques and the data obtained confirm their structure. TGA and DSC results suggested that BTATz decomposes in the range 265-350 degrees C and TADPTz in the range 245-275 degrees C respectively. The calculated energy of activation of BTATz and TADPTz is 212.69 and 257.29kJ/mol respectively. The experimentally determined DeltaH(f) value matches with theoretically computed heat of explosion. The computed volume of gases indicates that they can find application in gas generating compositions.

Graphene-iron oxide nanocomposite (GINC): an efficient catalyst for ammonium perchlorate (AP) decomposition and burn rate enhancer for AP based composite propellant

A facile and ecofriendly method for the synthesis of nano-sized iron oxide (Fe2O3) decorated graphene (GINC) hybrid by ultrasonication via microwave irradiation has been developed. During this process, nano-sized Fe2O3 particles with a size of approximately 20–30 nm were uniformly decorated over a graphene sheet. The nanohybrid was characterized by XRD, HRTEM, Raman spectroscopy and Raman mapping. To study the enhancement of catalytic activity of iron oxide by preparing GINC, several AP based compositions containing 1–5 weight% GINC were made and characterized through simultaneous thermal analysis (STA). Along with this, formulations with other catalysts with 1–5 weight% concentrations were also prepared and evaluated. Experimental results showed that GINC with 5 weight% concentration was considerably more effective as compared to other compositions. To further extend this application as a burn rate enhancer in composite propellants, several formulations of composite propellants containing 1 part of different burn rate enhancers, such as Fe2O3, nano-sized Fe2O3 and GINC, were prepared and evaluated using theoretical prediction, viscosity, ballistic properties, sensitivity parameter and thermophysical properties. To quantify the burn rate enhancement in the presence of GINC, burn rate measurement, STA, DSC and activation energy calculation were performed. The results show that the burn rate of propellant increases from micron-sized Fe2O3 (30% increases) to nano-sized Fe2O3 (37% increase). In the presence of GINC, a significant increase (52%) in burn rate is achieved. In GINC, effective iron content is about 50% as compared to nano- and micron-sized Fe2O3. Hence, GINC was found to be an excellent burn rate modifier for an advanced AP based propellant system.

Theoretical studies on the structure and detonation properties of amino-, methyl-, and nitro-substituted 3,4,5-trinitro-1H-pyrazoles

In this study, 3,4,5-trinitro-1H-pyrazole (R20), 3,4,5-trinitro-1H-pyrazol-1-amine (R21), 1-methyl-3,4,5-trinitro-1H-pyrazole (R22), and 1,3,4,5-tetranitro-1H-pyrazole (R23) have been considered as potential candidates for high-energy density materials by quantum chemical treatment. The geometric and electronic structures, band gap, thermodynamic properties, crystal density and detonation properties were studied using density functional theory at the B3LYP/aug-cc-pVDZ level. The calculated energy of explosion, density, and detonation performance of model compounds are comparable to 1,3,5-trinitro-1,3,5-triazinane (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). Atoms-in-molecules (AIM) analyses have also been carried to understand the nature of intramolecular interactions and the strength of trigger bonds.

Studies on characterisation and thermal behaviour of 3-amino-5-nitro-1,2,4-triazole and its derivatives

3-Amino-5-nitro-1,2,4-triazole (ANTA) and its derivatives have been prepared in order to carry out the systematic studies on structural aspects, explosive and thermal behaviour. Thermal studies were carried out for ANTA and 4,6-bis-(3-amino-5-nitro-1H-1,2,4-triazole-1-yl)-5-nitropyrimidine (DANTNP) by thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimeter (DSC) and manometric thermal analysis. The results show that (DANTNP) is more thermally stable than ANTA when compared in terms of activation energy.

Synthesis, characterisation, thermal and explosive properties of 4,6-dinitrobenzofuroxan salts

Two new initiatory molecules, e.g. rubidium and cesium salts of 4,6-dinitrobenzofuroxan (DNBF) have been prepared by reacting sodium salt of 4,6-dinitrobenzofuroxan (DNBF) with rubidium nitrate and cesium nitrate, respectively, at 60 degrees C in aqueous medium. The characterisation of compounds by IR, (1)H-NMR, elemental analysis and metal content is described along with some of the evaluated thermal and explosive properties. The results indicate that cesium salt of DNBF (Cs-DNBF) appears promising initiatory and may suitably replace potassium salt of DNBF (K-DNBF), being used currently in initiatory compositions.

One pot green synthesis of graphene–iron oxide nanocomposite (GINC): an efficient material for enhancement of thermoelectric performance

We report for the first time, a green method for graphene–iron oxide nanocomposite (GINC) synthesis by dispersing graphene and nano iron oxide (Fe2O3) in ethanol via ultrasonication followed by micro-wave irradiation. This is a simple method of making a broader range of graphene–metal oxide nanocomposites with excellent dispersion of 3D nanoparticles over 2D graphene. In addition, we have also demonstrated the synthesis of highly conductive PVAc–GINC and PVAc–graphene composites by ultrasonication followed by hot compaction for thermoelectric application. Graphene and GINC concentration were judiciously varied and optimized for the sake of high electrical conductivity and Seebeck coefficient. The fabricated PVAc–GINC film exhibited a conductivity of 2.18 × 104 S m−1 with a Seebeck coefficient of 38.8 μV K−1. Hence, the power factor (PF) reaches 32.90 μW m−1 K−2, which is 27 fold higher than the thermoelectric material based on PVAc–graphene composite. This PF value is found to be the maximal ever reported without using conducting polymer.

A graphene titanium dioxide nanocomposite (GTNC): one pot green synthesis and its application in a solid rocket propellant

A green process was developed for a graphene–titanium dioxide nanocomposite (GTNC) synthesis by dispersing titanium dioxide (TiO2) nanoparticles and graphene nano-sheets (GNSs) in ethanol via ultrasonication followed by microwave irradiation. The synthesized GTNC was well characterized by various tools: viz. XRD, HRTEM, FTIR and Raman spectroscopy. Also, Simultaneous Thermal Analysis (STA) and Differential Scanning Calorimetry (DSC) techniques have been employed to study the enhancement of the catalytic activity of the GTNC for the decomposition of Ammonium perchlroate (AP). The GTNC with 5 wt% in AP was found to be a highly effective catalyst for the AP decomposition. The decomposition temperature decreases from 412.87 °C to 372.50 °C and ΔH increases from 2053 to 3903 J g−1. Furthermore, the GTNC was identified as an effective burn rate enhancer (i.e. combustion catalyst) for an AP based composite propellant for solid rocket propellants as confirmed by STA, DSC, activation energy calculations and burn rate measurements. The results show that the burn rate of the propellant increases by 24% for the TiO2 nanoparticle based composition compared to the base composition, whereas a significant increase of 50% is achieved in the presence of the GTNC. Hence, the performance is improved significantly for the solid rocket propellant.

Studies on thermal decomposition mechanism of CL-20 by pyrolysis gas chromatography–mass spectrometry (Py-GC/MS)

The thermal decomposition study of CL-20 (hexanitrohexaazaisowurtzitane) using pyrolysis GC/MS was carried out mainly by electron impact (EI) mode. Chemical ionization (CI) mode was used for further confirmation of identified species. Mass spectrum of CL-20 decomposition products predominantly revealed fragments with m/z 81 and 96 corresponding to C(4)H(5)N(2)(+) and C(4)H(4)N(2)O(+) ions, respectively. The total ion chromatogram (TIC) of CL-20 pyrolysis shows peak within first 2 min due to the presence of low molecular weight gases. Peaks corresponding to several other products were also observed including the atmospheric gases. Cyanogen formation (C(2)N(2), m/z 52) observed to be enriched at the scan number 300-500. The low molecular mass range decomposition products formed by cleavage of C-N ring structure were found in majority. Additional structural information was sought by employing chemical ionization mode. The data generated during this study was instrumented in determining decomposition pathways of CL-20.