Muhamed Sućeska

Evaluation of Detonation Energy from EXPLO5 Computer Code Results

The detonation energies of several high explosives are evaluated from the results of chemical-equilibrium computer code named EXPLO5. Two methods of the evaluation of detonation energy are applied: (a) direct evaluation from the internal energy of detonation products at the CJ point and the energy of shock compression of the detonation products, i.e. by equated the detonation energy and the heat of detonation, and (b) evaluation from the expansion isentrope of detonation products, applying the JWL model. These energies are compared to the energies computed from cylinder test derived JWL coefficients. It is found out that the detonation energies obtained directly from the energy of detonation products at the CJ point are uniformly to high (0.9445?0.577 kJ/cm3), while the detonation energies evaluated from the expansion isentrope, are in a considerable agreement (0.2072?0.396 kJ/cm3) with the energies calculated from cylinder test derived JWL coefficients

Calculation of Detonation Parameters by EXPLO5 Computer Program

Detonation parameters of several high explosives were calculated using own chemicalequilibrium computer program named EXPLO5. The program is based on the chemical equilibrium, steady-state model of detonation. It uses the Becker-Kistiakowsky-Wilson’s equation of state (BKW EOS) for gaseous detonation products and Cowan-Fickett’s equation of state for solid carbon. The calculation of equilibrium composition of detonation products is done in the program by applying modified White, Johnson, and Dantzig’s free energy minimisation technique. The program is designed so that it enables the calculation of detonation parameters at the CJ point, as well as parameters of state along the expansion isentrope. The paper summarises results of the calculation of the detonation parameters of several standard high explosives by EXPLO5 program, using own set of constants in the BKW equation of state, socalled BKWN set (α = 0.5, β = 0.176, κ = 14.71, and θ = 6620). It was shown in the paper that the program can be used for the calculation of detonation velocity, pressure, temperature, heat, and detonation energy with reasonable accuracy – these detonation parameters can be calculated with the error less than 10 %.

THERMAL ANALYSIS OF LOW ALLOY Cr-Mo STEEL

The paper deals with results of thermal analysis of low-alloyed chromium-molybdenum steel. The methods of analysis were dilatometry, differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The Ac1 and Ac3 temperatures of the steel samples measured by dilatometry and DTA during the heating period were in good agreement. Generated by cooling a martensitic structure first became apparent at 503 K. Tempering of the as-quenched samples showed the presence of the second tempering stage in the region between 473 and 573 K. At that stage heat capacity decreased from 0.48 to 0.32 J g-1 K-1, as a result of conversion of transition carbide due to heat consumption. After normalization of the as-quenched samples the heat capacity values were restored to between 0.42 and 0.47 J g-1 K-1 in the temperature range from 373 to 673 K.

1,3,3-trinitroazetidine (TNAZ). Part I. Syntheses and properties

Abstract Review of more than sixteen routes for TNAZ synthesis is presented. The total yields of the most technologically attractive of thees does not exceed 30% of theory. It is stated that TNAZ is highly energetic material more powerful than RDX, which may be less vulnerable than most other nitramines, and which is suitable for applications as a castable explosive as well as a plasticizer. However, a relatively high vapour pressure, volume contraction and formation of shrinkage cavities in the solidification of its melt can be a minor disadvantage of TNAZ.

1,3,3-trinitroazetidine (TNAZ). Study of thermal behaviour. Part II

Abstract Thermal behavior of TNAZ (1,3,3 - trinitroazetidine) was studied by using differential scanning calorimetry (DSC), differential thermal analysis (DTA), and thermogravimetryc analysis (TGA). It was found out that TNAZ is thermally more stable than RDX, but less stable than HMX and TNT. The reaction of intensive thermal decomposition starts at 183–230 °C, depending on heating rate, while the first exothermic reaction was observed at 178 °C at the heating rate of 1 °C/min. By applying multiple heating rate DSC measurements and Ozawas method the activation energy of 161.3 kJ/mol and pre-exponential factor of 8.27·1013 1/s were calculated from DSC peak maximum temperature-heating rate relationship. By the same method the activation energy of 157.5 kJ/mol and pre-exponential factor of 4.55·1013 1/s were calculated from DTA peak maximum temperature. By applying Flynn-Wall isoconversional method it was calculated from DSC measurements that the activation energy equals between 140 and 155.6 kJ/mol at degrees of conversion ranging between 0.3 and 0.7, while pre-exponential factor ranges between 7.8·1012 and 1.92·1013 1/s.

Modification of BKW EOS Introducing Density-Dependent Molecular Covolumes Concept

One of the most important tasks of thermochemical codes for the calculation of detonation properties is the accurate description of the state of gaseous products within a rather wide range of pressures and temperatures – from several hundreds of kbar and several thousands of K to atmospheric pressure and temperature. Due to its simplicity and convenience, the Becker-Kistiakowski-Wilson (BKW) equation of state is used in many practical applications in the explosives field, despite its lack of rigorous theoretical background. The BKW EOS gives good agreement between calculated and experimentally obtained detonation parameters for many standard high explosives having densities in the range 1.2 – 2 g/cm3. However, it fails to predict accurately detonation properties at lower densities. To overcome this problem, we introduced the concept of density dependent molecular covolumes in the BKW EOS instead of invariant. The applicability of the approach is verified by comparing experimental and calculated values of detonation parameters for a series of explosives having different formulations and densities. It was found that by applying this approach the accuracy of the calculations for lower densities can be significantly improved.

Fluorodinitroethyl Ortho-carbonate and -formate as Potential High Energy Dense Oxidizers

Tetrakis(2-fluoro-2,2-dinitroethyl) ortho-carbonate (1) and tris(2-fluoro-2,2-dinitroethyl) orthoformate (2) were synthesized by the reaction of carbon tetrachloride, respectively chloroform, with 2-fluoro-2,2-dinitroethanol and catalytic amounts of anhydrous iron(III) chloride. The compounds were characterized by single-crystal X-ray diffraction, vibrational spectroscopy (IR and Raman), multinuclear NMR spectroscopy, elemental analysis, and multi-temperature DSC measurements. The suitability of the compounds as potential oxidizers in energetic formulations has been investigated and discussed. The heats of formation of the products were determined experimentally using bomb calorimetric methods. With this value and the experimental (X-ray) density, several detonation parameters such as the detonation pressure, velocity, energy, and temperature were computed using the EXPLO5 code. The sensitivity towards impact, friction and electrostatic discharge was tested using the BAM drop hammer, a friction tester and a small-scale electrostatic discharge device. Graphical Abstract Fluorodinitroethyl Ortho-carbonate and -formate as Potential High Energy Dense Oxidizers

Chemistry and Structures of Hexakis(halogenomethyl)‐, Hexakis(azidomethyl)‐, and Hexakis(nitratomethyl)disiloxanes

An investigation of the structures and chemistry of substituted hexamethyl disiloxanes ((XCH2)3Si)2O; X=F, Cl, Br, I, N3 , and ONO2) is reported. New synthetic routes to the precursor hexakis(chloromethyl)disiloxane are presented. The products with X=Cl, Br, I, and N3 were characterized by NMR, IR, and Raman spectroscopy. In addition, the single-crystal structures of the products with X=Cl, Br, and I are discussed in detail. The compounds with X=F and ONO2 were not obtained in their pure form; instead investigations of the decomposition products revealed their conversion into intermediates. Theoretical calculations of the gas-phase structures at the B3LYP/cc-pVDZ, B3LYP/3-21G, MP2/6-31G*, and MP2/3-21G levels of theory are used to explain the chemical and physical behavior of the compounds with X=Cl, Br, I, N3, and ONO2. A new decomposition pathway of hexakis(nitratomethyl)disiloxane is presented and is used to explain their remarkable instability. The energetic properties and values of the nitrate and azide derivatives were calculated at the CBS-4M level of theory by using the improved EXPLO5 computer code version 6.01.

Numerical Prediction on Cookoff Explosion of Explosive under Strong Confinement

The cookoff of explosives is of great concern for the safety assurance of explosive devices in storage, transportation and handling. It may occur in the situation that explosive devices are subjected to the external heating stimuli such as fire or high-temperature surrounding. In order to gain ever-increasing knowledge toward the cookoff explosion of explosives, we establish numerical program to predict the cookoff explosion of explosive in a metal container. The computational formulation and methods are given in detail. The thermal decomposition and temperature variation in the interior of explosive were found corresponding to several typical external heating conditions. The results demonstrate that the method is beneficial to the future study on this subject.

Testing Adsorbents For Heat Treatment of Pipes

Heat treatment of pipes was performed under industrial conditions at 580°C in a dry protective gas containing a CO2–CO–H2–N2 mixture. A commercial adsorbent (733 kg) used for production ofthe gas removed 52.7 l of water in five h and 22.5 min. During the annealing of pipesoxidation and decarburization were not observed. The results were confirmed bymetallographic analysis. The values of enthalpy of water desorption (36.4–40.5 kJ mol–1) obtained by DSC and TG measurements were close to those of water evaporation(44.1 kJ mol–1). This suggests that the bonds between the water molecules andadsorbents were not of chemical but of physical nature.