فصلنامه مواد پر انرژی
سال هفتم شماره 1 (پیاپی 14، بهار 1391)

Electrochemical behavior of a Prussian blue -modified carbon paste electrode and their applications to electrocatalytic activity for hydrazine oxidation. The electrochemical behavior and stability of the modified electrodes as well as electro-oxidation of hydrazine at the electrode were investigated using cyclic voltammetry method. At the modified electrode, the oxidation of hydrazine occurs at potentials where it is not observed at a bare carbon paste electrode. The modified electrodes exhibited potent and persistent electrocatalysis for hydrazine oxidation in 0.1M phosphate buffer (pH=¬7.4). The electrocatalytic current increased linearly with the hydrazine concentration in the range of 0.02-2.4 mM. The detection limit for hydrazine was estimated 1.7 10 5 M. The method was successfully applied for determination of hydrazine in water samples.

The friction sensitivity (FS) of five aliphatic linear and eight cyclic nitramines has been determined and was correlated with their impact sensitivity (IS) and 15N NMR chemical shits of the nitrogen of nitramino groups (which primarily react in initiation step of these polynitro compounds). A mutual comparison of the friction and impact sensitivities resulted in a series of partial relationships, which are determined from the molecular structure of these substances. The character of relationship between FS and 15N chemical shits of nitrogen atoms in nitro groups corresponds best with the relationships that are common in physical organic chemistry. In this respect it differs from the analogous relationship of impact sensitivity which is best interpreted by the application of 15N shifts of aza atoms in the most reactive nitramino groups. Both these sensitivities mutually differ in mechanisms of transfer of the primary impulse into the reaction centre of molecule.

Excessive heat transfer causes major defects on the rocket motors. For example, it will reduce mechanical properties of materials or causes melting of internal wall layers when temperature rises. In the other hand, non-uniform distribution of temperature in solid propellant motor shells, in addition to thermal stresses will develop mechanical stresses. Calculating the temperature distribution and thermal and mechanical stresses on the solid rocket motors were interested by the designers. In this paper, the manner of calculating the mechanical and thermal wall stresses on solid propellant rocket motors using dynamic coupled thermoelasticity equations relationships are presented. For this purpose, firstly differential equations governing the issue are resolved using the finite element method. The presented approach is applied and tested on a real rocket and the effect of thermal insulation in wall temperatures and mechanical stresses is shown.

Use of antioxidants in composite propellants formulation to import stability to the propellants during storage time is unavoidable. In this paper, the synthesis of 2-t-butyl p-cresol intermediate for the preparation of A.O.2246 using of nanospinels as catalyst is investigated. Tertiary butylation of p-cresol using of alkylating agents as methyl-tert-butyl ether and t-butyl alcohol is reconsidered using Cu1-xCoxFe2O4 (x = 0 to 1) nanospinels as a function of temperature, mole ratio, type and catalyst composition, time and solvent. These catalysts were synthesized using hydrothermal method. Tertiary butylation of p-cresol gives two products, namely, 2-tert-butyl p-cresol and 2,6-di-tert-butyl p-cresol. A good correlation was found between the activity, in terms of p-cresol conversion and various reaction product selectivity and the acid–base properties of catalysts. Cu0.5Co0.5Fe2O4, irrespective of the alkylating agents is most active catalyst. The only product of this reaction is 2-t-butyl p-cresol with selectivity of 100% and p-cresol conversion is 70%. These results illustrate the importance of a 1:1 combination of Cu and Co and the necessity for optimum concentrations of acid–base centers for this reaction. The characterization of these catalysts was investigated via X-ray diffraction (XRD).

Gel propellants possess some of the advantageous properties of both liquid and solid propellants. They are generally less sensitive to impact, friction and electrostatic discharge compared to solid propellants. The gel propellants are as non-Newtonian fluids, rheological properties of which affect the processes of atomization and combustion. The amount of gelling agent, the mixing speed and time are the main factors in production process which affect the gel properties. In this paper, the effective parameters on rheological properties of non-metallized nitromethane gel were investigated. The results showed that the amount of the gelling agent of about 5% of fumed silica, impeller speed of about 1000 rpm and mixing time of about 150 minutes are the most suitable conditions for the preparation of nitromethane stable gel.

Because their favorable ballistic performance and low stress and strain caused on the canon and gun pipes and also their low prices and light weights, the combustion cartridges have a widespread utilization in artillery, tank, and mortar ammunitions. In this paper, stresses on the cannon pipe, in two cases of brass and combustion ammunition cartridge were analyzed using Abaqus finite element software. Cannon pipe stress increased in the ammunition with brass cartridge because of cartridge contact with pipe. Also, plastic strain in the pipe caused by combustion cartridge is 33% of which caused by brass cartridge. Results indicate that the use of combustion cartridge caused less stress and strain on the gun pipe.

The impact of a massive plate on an initially stationary foam layer is considered. Analytical solution for dynamic deformation of foam materials for two shock wave and elastoplastic wave propagation regimes are developed. Explicit finite element simulation of the collapse of the foam's cells and their compaction behind the shock front are carried out. The numerical prediction is found to be in a desirable agreement with the analytical results.