فصلنامه مواد پر انرژی
سال سوم شماره 2 (پیاپی 6، پاییز و زمستان 1387)

A simple and sensitive derivative spectrophotometric method was proposed for the simultaneous determination of magnesium and strontium in mixture. The method was based on the color reaction of magnesium and strontium with 1, 8-dihydroxy anthrone as a new chromogenic reagent in cationic surfactant cetylpyridinium chloride (CPC) micellar media. The chemical variables affecting the maximum sensitivity of both ions (e.g. pH, reagent and surfactant concentrations, temperature and instrumental parameters) were evaluated and optimized. Under the optimum experimental conditions, calibration graph was linear in the range of 0.05-1.80 and 0.10–1.60 of magnesium and strontium at 515 and 565 nm (the zero crossing point of Mg and Sr complexes in the first order derivative mode) respectively. The reproducibility for 5 replicate determinations at 0.5 μg ml-1 of Mg(ΙΙ) and Sr(ІІ) were 0.98% and 1.34% respectively. The interference effect of some cations and anions was also studied and elevated using appropriate masking agents. The proposed method was successfully applied for the simultaneous determination of these ions in solid-base propellants and the obvious data were compared with ICP-AES results.

Explosive welding is produced by the high velocity oblique impact of the flyer plate to the base plate. This high oblique impact produces the localized plastic deformation at the collision point. In this process, the bonding between two metals is obtained by use of impact force produced by the explosive charge. The impact force has to be applied with sufficient magnitude and with a proper impact angle to produce the sound joints. Therefore, the selections of optimum welding parameters are more important than other welding process. Two of these welding variables are the explosive charge and stand-off distance. In this study, the effects of explosive charge and stand-off distance between the Al5083/Al1250/Sea Grade steel on the interface properties of three layer composites are considered. The optical and scanning electron microscopes were also performed on the interface of various samples. The optimum stand-off distance was determined. The results show that the shapes of the interface changes from the straight interface to the wavy interface by the explosive load. The EDS analysis show that at high explosive load, the vortices are formed in the interface and the layers of melts and intermetallic phases are produced in the vortices.

In this paper, chemical safe life of double base solid propellants with two kinds of stabilizers, i.e. Acardite II and Centralite I, was investigated by Bergman junk and high performance liquid chromatography(HPLC) methods at normal storage temperature (e.g. 40 oC). Then the rate of stabilizer consumption was considered. In the Bergman junk method, a certain amount of propellant was aged at different temperatures between 90-120 oC and graphs of the volume of evolved gases versus aging time were drawn. Then auto catalytic point was assigned from this curves and the graph of heating temperature against the time of auto catalytic point was plotted. By extrapolation of the obtained straight line up to normal storage temperature, safe life of the propellant was predicted. In the HPLC method, propellant was sampled from aged specimen at Bergman junkmethod and several new samples which were aged at different temperatures between 65.5-120 oC and the amount of remaining stabilizers were determined after soxhlet extraction by dichloromethane. Diagrams of stabilizers depletion in solid propellant versus aging time were drawn at different temperatures and the time at which stabilizer content approached zero (auto catalytic point) was determined. It is to note that the rate of depletion of Acardite II is faster than Centralite I, thus, calculation of chemical safe life of the double base solid propellant was accomplished on the basis of HPLC data obtained from Acardite II, and safe life of propellant was calculated by Berthelot’s equation. Kinetic of stabilizer depletion in propellant was considered as Zero, first order and also shifting order reaction and suitable kinetic model for consumption of stabilizer at high and low temperature was suggested. Using shifting order kinetic, the time of auto catalytic point was calculated and compared with experimental time of auto catalytic point.

Analysis of porous structures, specifically honeycombs is of great importance; according to their two remarkable characteristics: excellent strength to weight ratio and noticeable energy absorption. In this survey, the experimental analysis of folding and densification of honeycombs subjected to blast loading is the main objective. To do so, ninety experiments were conducted on four different kinds of honeycombs. Afterwards, the results were compared to the analytical analysis of honeycombs under dynamic loading and also experimental analysis of honeycombs under quasi-static loading which have been reported by other researchers. A good agreement was observed between experimental results and analytical predictions. Moreover, comparing to static loading, the strength of honeycomb structures was improved under blast loading.

Explosive compounds are known to release a significant plume containing toxic levels (μgL-1 to mgL-1 range) and environmental pollution of military munitions sites are hazardous to agricultural crops and humans. HMX, RDX and TNT are major ingredients in nearly every ammunition formulation and are the secondary explosives used in greatest quantities. Since the explosives are found at ultra trace levels in environment samples, so priorto their determination an enrichment process is required and afterwards rapid and sensitive techniques for their monitoring are needed. In this work, an analytical method was developed to the preconcentration of the explosive compounds (HMX,RDX and TNT) in water samples based on the cloud point extraction, and after extraction, the extracted compounds were analysed by high performance liquid chromatography. The parameters affecting extraction efficiency (such as concentrations of Triton X-114 and Cetyl-trimethylammonium bromide, electrolyte and its amount, temperature, incubation time, and centrifuge time) and chromatographic conditions (such as selected wavelength, nature of mobile phase and gradient program) were evaluated and optimized. Under the optimum conditions, the improvement factors of 34, 29, 61 and detection limits of 0.1, 0.14, and 0.08 μgL−1 were obtained for HMX, RDX and TNT respectively. This method was successfully applied for the determination oftrace amounts of these compounds in water samples.

In this paper, the principals and considerations of sabot design of APFSDS Projectiles including projectile diameter to sabot diameter ratio, the minimum sabot length allowed (based on projectile strength and allowable shear stress between sabot and projectile), and behind curve profile of sabot for smoot shear stress have been discussed. Also, a sabot model for a given projectile has been designed and stress analysis of two types of sabot geometry (saddle and the designed models), has been done by ABAQUS/Explicit code. Shear stress distribution between sabot and projectile, from the two models has been compared, and preference of “the designed model”in terms of more smooth distribution has been shown.

FOX-7 (1,1-diamino-2,2-dinitroethylene) recently is expected as a relatively new energetic material with highperformance and low sensitivity. The RHF and MP2 levels and DFT method with B3LYP functional with aug-cc-pVDZ basis set have been used to obtain optimized geometries and Rho functions (electron density distributions). Via fundamental physical theorems implemented in Quantum Theory of Atoms in Molecules (QTAIM), the structures, the physical nature of chemical bonds and all Bond Critical Points (BCPs) properties have been determined for cited species at the mentioned theoretical levels. In the present study, existence of intra-molecular hydrogen bonding and resonance due to "electron-withdrawing" nitro groups and "electrondonating" amine groups in ethene backbone is shown with AIM analysis and the resonance structures of FOX-7are obtained. In addition, the calculated wave numbers of vibrational normal modes (in gas phase) are compared with experimental IR spectrum of FOX-7.