فصلنامه مواد پر انرژی
سال نهم شماره 3 (پیاپی 24، زمستان 1393)

Pyrolants are an important class of energetic materials which because of the high energy content and the solid fused residues، serve a remarkably wide range of military and civilian applications. Pyrolant incendiaries can be either fuel rich or provide a surplus of oxidizer to facilitate combustion of a target substrate. The requirements and characteristics of an incendiary pyrolant not clearly identified. However، the heat of reaction، thermal kinetic data and macroscopic combustion parameters are of the basic requirements for the designing of these compounds. In this work، for the first time، the multicomponent Al/MnO2/PTFE pyrolant is introduced as an incendiary charge. Thermal reaction kinetics (activation energy، frequency factor، critical temperature and self-accelerating decomposition temperature) were studied with differential scanning calorimetry (DSC). Also this work investigations the macroscopic combustion behaviors (such as flame speed and ignition delay time) along with experimental results focusing on open burn experimental setup. Results indicate that the incorporation of nano-Al higher than 30%، significantly reduces ignition temperatures and produces unique reaction behavior that can be attributed to a different chemical kinetic mechanism than observed with micron-Al particles.

Bonding agents are important components in solid propellants which affect processing, mechanical, ballistics, safety and aging properties of propellant. In this research, we have synthesized and characterized three types of new polymeric bonding agents by post functionalization of glycidyl azide polymers (GAP) via click chemistry. The interaction of new bonding agents with the surfaces of RDX particles have studied by IR spectroscopy that shown a 7/86 shift of nitro group absorption peak at 1593 cm-1. Also, The mechanical properties of a typical HTPB base propellant with new polymeric bonding agent are considerably improved. The value of maximum tensile strength is increased from 0/53 MPa to 0/85 MPa and the value of maximum strain at break is increased by % 147 at 25 °C. As well as, the results of DSC trace show that the thermal stability of the polymer bonding agents is acceptable for using in a propellant formulation.

Magnesium powder are used extensively in formulations of energetic materials. Of powdered can be used as metal fuel in explosives, Pyrotechnics and propellants. The main use of magnesium powder is in Flare Pyrotechnic magnesium,Teflon, Viton (MTV).While the basic problem in using this powder, its high reactivity against oxygen and moisture, this will result in the deactivation magnesium powder particles. So to avoid this, it is necessary that the particles are covered by a thin layer of a durable combination. In this study, magnesium powder particles covered with Viton polymer by solvent-Anti solvent method. In this study, were used SEM, FT-IR and EDX method to evaluate the coverage. So the coating effect Viton on thermal stability magnesium powder was investigated using thermal decomposition methods (Thermogravimetry‌ Analysis and Differential Scanning Calorimetry). In this research, for data analysis Qualitek-4 software was used.

This researchhas been conducted to perform a model for ballistics and propulsion specifications or characteristics of a monopropellant Propulsion system. The specifications such as total impulse, thrust, mass flow rate, specific impulse, characteristic velocity and total weight of consumed propellant are important in propulsion performance determination. Among 31th experimental hot tests of monopropellant thruster, the 20th number of tests are accepted. These experimental test data are recorded in the four environment constrains. By using the accepted experimental data, the important ballistic and propulsion characteristic can be derived. The variation of characteristic parameters versus the catalyst bed pressure, have been studied. Also, the variation of these parameters versus the Hydrogen peroxide concentrations, have been investigated. By analyzing the behaviors of characteristic parameter variations, the performance of the monopropellant propulsion system has been achieved.

In this study, the combustion characteristics and burning rate of RDX/AP/Al/HTPB composite solid propellant were studied experimentally. Five different RDX-based propellant compositions have been formulated and the burning rate and calorimetric value were evaluated. The burning rates of RDX composite solid propellants increased with increasing RDX content. The data obtained from experimental tests indicates that increasing weight percentage of RDX in the formulation increases the pressure exponent and decreases the burning rate constant. The mentioned parameters related to the propellant without RDX compared with other formulations including RDX. The results show that the burning rate of the propellant without RDX at the constant pressure of 800Psi was 7.2 mm/s and as RDX content increased by 13.6%, the burning rate decreased to 5.5 mm/s. The relationship between the burning rate and RDX content was not linear. It was also found that the pressure exponent increased by increasing RDX content. As a result, the pressure exponent belonged to the based propellant was 0.22 that by increasing the percent of RDX to 13.6%, the pressure exponent increases up to 0.3.

CL-20 is one of the well-known non-nuclear powerful energetic materials. TADB is an important intermediate in synthesis of CL-20. One of the significant steps in synthesis of CL-20 is application of palladium catalysis for debenzylation of TADB which has some disadvantages such as the high cost, need to special reactor and high cost and need to especial reactor, therefore scientists to find alternative catalyst to overcome these problems. Some of these reagents including cerium ammonium nitrate, cerium ammonium sulphate, potassium bromate, titanium thrichloride, and acidic reagent. It is notable that among these catalysts some of them such as cerium ammonium nitrate in pyrolidinium bisulphate ionic liquid, cerium ammonium nitrate in presence of oxidative reagents and titanium trichloride showed good results and the yield of tetraacetylhexaazaisowortzitane was desirable. The yield of 55% and the absence of organic solvent are the advantages in application of cerium ammonium nitrate in pyrolidinium bisulphate ionic liquid.

In this study, the impulses of explosion within an aluminum truncated cone cylinder shells, effective parameters in explosion of these structures and structure effect on blast wave have been investigated. The goals of this study have listed as follows: a) determining critical value of explosives or necessary dynamic pressure for structure failure, b) formability limit during dynamical deformation and c) proposition of a semi experimental equation that can predicts structure failure. In this paper, two states, tearing of structure and after tearing of structure for explosion of explosive within structure were considered. From tearing state of shell, the value of explosive for tearing of shell was extracted. In this state, we have used dimensionless groups of useful parameters and doing tests on scaled shells. Also failure behavior of structure and used metal in it for scaling samples was determined. For after tearing of structure state, the impulse of blast wave within defected shells measured at specified distances out of shells from defect and determined that obtained impulses are higher than impulses of blast wave in free space.