SCIENTIFIC PUBLICATIONS

Ph.DDOCTOR OF SCIENC

Crystal Structure and Improved Synthesis of 1-(2 H -Tetrazol-5-yl)guanidium Nitrate

Energetic derivatives of tetrazoles are one of the key areas of research focus in pursuit of novel high energy materials, useful as propellants and explosives. Herein, the crystal structure and an improved synthetic procedure of 1-(2H-tetrazol-5-yl)guanidine (1) and its nitrate salt (2) are reported. The compounds were structurally characterized by spectroscopic (FT-IR, 1H NMR, 13C NMR) and elemental analysis. The molecular structure of tetrazolyl guanidium nitrate (2) was solved using low temperature single-crystal X-ray diffraction. 2 crystallized as its hemihydrate in the orthorhombic space group Fdd2, with a crystal density of 1.69 g cm−3. Thermal behavior and decomposition of the molecules were studied with differential scanning calorimetry (DSC). Molar enthalpy of formation (ΔfHm) of compound 2 was back calculated from heat of combustion (ΔcH0) value obtained experimentally using bomb calorimetric measurements. Lattice enthalpy of 1-(2H-tetrazol-5-yl)guanidium nitrate was directly calculated from measured crystal density using Jenkins equation. Preliminary ballistic parameters of the compound were predicted and compared with reported high nitrogen tetrazole derivatives.Accepted versio

1-(2 H -Tetrazolyl)-1,2,4-triazole-5-amine(TzTA) : a thermally stable nitrogen rich energetic material : synthesis, characterization and thermo-chemical analysis

The targeted high nitrogen energetic material 1-(2H-tetrazol-5-yl)-1,2,4-triazol-5-amine (TzTA) was synthesized from 3-amino-1,2,4-triazole via a two-step procedure using cyanogen bromide and sodium azide. TzTA was prepared in good yields and characterized using analytical (elemental) and spectroscopic (IR, Raman, NMR) techniques. The crystal structure of sulfate salt of the molecule was solved by means of low temperature X-ray crystallography, which showed the co-planarity of the two rings. The sulfate salt of the molecule crystallized in monoclinic system P21/n, with a crystal density of 1.856 g cm−3. The thermal stability of the molecule was assessed by DSC. The molecule showed excellent thermal stability better than many known nitrogen rich energetic molecules and showed comparable thermal stability with HMX. Non-isothermal kinetics was performed on the molecule to derive the activation energy. Constant volume combustion energy was determined using oxygen bomb calorimeter and back calculated the heat of formation. Preliminary insight on the gas generating capability of the molecule was tested by measuring the dynamic pressure generated inside a closed bomb. Dynamic pressure of an oxygen balanced system (TzTA and ADN) was also measured using the Parr dynamic pressure measurement system

Vapor pressure of explosives : a critical review

A critical review of vapor pressure data for military, civilian, and homemade explosives, explosive precursors, and explosive taggants is presented. It gives reference to a large number of papers and reports presenting original vapor pressure measurements and additionally an overview of measurements techniques for vapor pressure measurements and data analysis of vapor pressure measurements. Vapor pressure data, including Clausius–Clapeyron parameters (A and B in: log10(p)=A−B/T), calculated vapor pressure at room temperature, and heat of sublimation or heat of vaporization are included. The following classes of compounds are treated; military explosives (TNT, RDX, HMX, PETN, HNS, TATB, AP), civilian explosives (NG, EGDN, AN), explosive taggants (EGDN, DNMB, 2-NT, 4-NT), home-made explosives (TATP, DADP, HMTD). and explosive precursors [HP(aq), NM, IPN, DNT]

Influence of passivation on ageing of nano-aluminum: Heat flux calorimetry and microstructural studies

Aluminum nanoparticles (n-Al) have been considered as promising fuel for incorporation in propellants and explosives to improve their performance. To prevent oxidation during storage, we investigate the effect of organic coatings on reducing oxidation of n-Al via accelerated ageing tests. The n-Al was modified with 3 different functional organic silanes. The presence of organic coatings on surface-modified n-Al was confirmed by X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). In the accelerated ageing tests, the pristine and surface-modified n-Al were kept at elevated humidity and temperatures. The ageing process was monitored via heat flow calorimeter. The effectiveness of the organosilane coatings as barrier to hydrolysis and oxidation of n-Al was evaluated from the heat released during ageing, as well as the analysis of active Al content of the aged samples. It is found that although the pristine n-Al possesses a natural Al2O3 passivation layer, it cannot prevent n-Al from fully getting oxidized under the conditions tested. Organosilane coatings act as excellent barrier against diffusion of moisture preventing n-Al inside from oxidation. This study shows that all 3 kinds of organosilane-modified n-Al have much better resistance to ageing than the pristine n-Al, therefore demonstrates surface-modification of n-Al is a promising technique to extend the shelf life of n-Al during storage.Accepted versio