JOURNAL OF ENERGETIC MATERIALS
Year:2012 | Volume:7 | Issue:3 (16)|Papers Count:9

Hexanitrohexaazaisowurtzitane (HNIW or Cl-20) is a high-energetic material with a cage structure. It is considered as the most powerful explosive. It is usually prepared via nitration of precursors with concentrated nitric and sulfuric acids. Herein, the usage of an efficient catalyst affording mild reaction condition for nitration of 2, 6, 8, 12-tetraacetyl-4, 10-diformyl-2, 4, 6, 8, 10, 12-hexaazaisowurtzitane (TADFIW) is reported. It has been well documented that heteropolyacids (HPAs) are an efficient and green catalysts. So here it is used as nitric acid activator. This strategy gave a milder condition for nitration reaction. Also the reactions can be carry out in a reasonably lower temperature. Using a new nitrating agents, concentrated sulfuric acid was eliminated from the reaction conditions. Meanwhile, the effect of the reaction temperature, time and other factors on the yield was investigated. The structure and purity of the compounds were characterized by elemental analysis, HPLC, IR and 1HNMR.

Dimethyl amino ethyl azide (DMAZ) is a good candidate fuel for hydrazine derivatives in aerospace industries. Due to thermal sensitivity of DMAZ, vacuum distillation is used as a preferred method for purification of the fuel. In this article, equilibrium behavior of binary solution of DMAZ and water at 4 kPa is investigated. The experimental equilibrium data were compared with different states equation (such as NRTL, WILSON, UNIQUAC and etc.) and with activity coefficient obtained from software simulations. Experimental results were in good agreement with UNIQUAC equation. Excess Gibbs energy was calculated using the data. Finally, it was concluded that the solution has positive deviation from ideal state. Results showed that the binary solution has an azeotrope at about 96 mole percent when total pressure is 4 kPa.

2-methylaziridine (propylene imine) is widely used in the production of binding agents in the defence industry. Despite its importance, it is a highly volatile and toxic and can be easily released into the atmosphere during the production and usage causing environmental pollution. The International Agency for Research on Cancer (IARC) has classified it as a Group 2B, possible human carcinogen. So, regarding to the application of 2-methylaziridine in military industry and its toxicity, the determination of its trace amounts is very important in environment samples and industrial wastewater. In this paper, a novel method for preconcentration and spectrophotometric determination of trace amounts of 2-methylaziridine using dispersive liquid-liquid microextraction (DLLME) technique has been developed. This method is based on derivatization of 2-methylaziridine with Folin’s reagent (1,2-naphthoquione-4-sulphonic acid) and preparation of a hydrophobic product with a high molar absorption coefficient which can be preconcentrated and extracted with DLLME technique. Some important parameters of derivatization and microextraction were studied and optimized. Under the optimum conditions, the calibration graph was linear in the range of 10-800 ng mL-1 with detection limit of 5.0 ng mL-1 and relative standard deviation for seven replicate determinations of 2-methylaziridine at 100 ng mL−1 concentration level was calculated to be 1.92%. The proposed method was applied for the determination of 2-methylaziridine in natural water and wastewater samples. In addition, excellent agreement was observed between this proposed method and the standard method.

Numerical simulation of grain burn back has been done in three dimensions. For numerical grain burn back analysis, a numerical code based on level set method has been developed and in order to increase accuracy, cut cell method was implemented for elements which capture interfaces. The accuracy of the code was validated by grains which have analytical solutions. It was seen that the code has acceptable accuracy. Then, the results of burn back analysis for some grain configuration were depicted. Also, an internal ballistic code in zero dimensional was generated to predict the pressure inside the motor, and was linked by burn back analysis code. The simulation results were compared with experimental ones and high accuracy was achieved.

In this paper, an analytical method for prediction of residual velocity and exiting angle of a rigid projectile with different nose shapes impacting a thick metallic target is presented. In this method, penetration of the projectile is investigated in three stages of entrance, tunneling and exiting of the projectile from the target. The first and second stages of this method are based on Energy Method and Spherical Cavity Expansion Method and the exiting phase of the projectile is modeled by the Shear Plugging. This method is capable of analyzing penetration of projectiles in semi-finite targets and also normal impact conditions. Also the LS-DYNA finite element code was used for 3D simulation of the penetration process and the results were compared to numerical and experimental data which showed desirable conformity between outputs of these results.

Two dimensional numerical simulation of detonation diffraction is done in the mixture with the activation energy of 15 which has regular cellular structure, from a small cannel to a larger one with aspect ratio of two. Modeling is based on reactive Euler equations and One-step Arrhenius rate law. The width of the small cannel size is considered enough that at least 5 cells are in the width. The results obtained from detonation cell structure are shown that during the detonation transition from small cannel to larger one, firstly cell structures disappear in up and down of the front. With more detonation front going forward in the large cannel, all of the five cells are deleted and maximum local march of detonation is on the center line of the cannel. Study of detonation front during diffraction also showed that the local separation of the reaction zone from precursor shock waves occurs at upper and lower part of the detonation front. These results -that are in agreement with experiment- are due to the gas dynamic effect and effect of cooling of detonation front by expansion waves. Interaction between weakening of detonation by expansion waves and amplification of it by perturbation, triple points and corresponding transverse waves, has led to unstable behavior of detonation. The present results have shown that amplification of triple points and corresponding transverse waves, after the collision with the wall, are essential role in the reinitiating of detonation.

In this paper, an analytical model for impact of flat-ended projectiles onto the composite – foam sandwich panel is presented. The panels consist of foam core sandwiched between two composite skins. In the quasi-static loading, by using the springs-mass model, the load at failure of top composite skin and the energy absorbed due to failure of the top skin have been determined. The absorbed energy during the perforation of the sandwich panel is calculated and the energy balancing equation has been employed for determination the ballistic limit and residual velocity of projectiles. The load at failure of top composite skin, energy absorbed due to the top skin failure, ballistic limit and residual velocity have been compared with the available experimental results. The good agreement between analytical model and experimental results has been observed.