Anuj A. Vargeese

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.

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.

Pressure effects on thermal decomposition reactions: a thermo-kinetic investigation

The rate of chemical reactions is largely governed by three parameters namely, temperature, extent of the reaction/reaction model and pressure. Usually, the pressure is assumed to be constant and experiments are carried out at 0.101 MPa (1 atm) pressure. Ammonium perchlorate (AP) is an extensively used solid propellant oxidizer and its decomposition kinetics have been attracting significant research interest for quite some time. In the present study, the influence of pressure on the decomposition reaction and kinetics of AP is investigated. As well, we have synthesized CuO nanorods, characterized with (scanning electron microscopy) SEM, (high-resolution transmission electron microscope) HRTEM, (selected area diffraction) SAED and (powder X-ray diffraction) PXRD and added to AP as a catalyst and then the influence of pressure on the catalyzed decompositions are investigated. The decomposition behavior and kinetics were studied at three different pressures, 0.2, 0.6 and 1.2 MPa. The thermogravimetric analyzer and a high pressure differential scanning calorimeter were used for the studies. The studies reveal two different behaviors of catalyzed and non-catalyzed decomposition of AP under different pressure conditions. Promotion of secondary gas phase reactions by nitrogen and surface reactions on the nanocatalyst, promoting the oxidation reactions presumably lead to different decomposition behaviors of AP under different pressure conditions.

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.

A Kinetics Investigation on the Nitro-Nitrite Rearrangement Mediated Thermal Decomposition of High Temperature Monoclinic Phase of 1,1-Diamino-2,2-Dinitroethylene ( γ -Fox-7)

Abstract1,1-Diamino-2,2-dinitroethylene (DADNE), commonly known as FOX-7, is one of the novel high energy density molecules recently developed along with CL-20, TNAZ and ADN. DADNE is well-known for its insensitive nature and this has motivated the research in understanding the thermal and explosive decomposition behaviour of DADNE. We have studied the thermal decomposition kinetics of DADNE employing two isoconversional methods viz., Friedman’s differential method and Vyazovkin’s non-linear integral method. For the study, Differential Scanning Calorimetry as well as Thermogravimetry data collected at lower heating rates (<5°C/min) were used. This study indicated a four stage decomposition behaviour of DADNE, where each stage is characterised by different activation energy. Computed activation energy values have been used to understand the thermal decomposition mechanism of DADNE. Graphical AbstractExperimental investigations of thermal decomposition kinetics of 1,1-Diamino-2,2-Dinitroethylene (γ-Fox-7), DADNE at a lower heating rate was studied using Differential Scanning Calorimetry and Thermogravimetry. The results suggest that DADNE exhibits two different decomposition pathways. During thermogravimetric analysis it undergoes nitronitrite rearrangement-mediated decomposition leading to the formation of CO, H2O and N2.