مجله تحقیق و توسعه مواد پرانرژی
سال هفتم شماره 2 (پیاپی 14، پاییز 1390)

Polymorphism is the ability of a solid substance to crystallize into more than one different crystal structure. Different polymorphs have different arrangements of atoms within the unit cell, and this can have a profound effect on the properties of the final crystallized compound. One of the fundamental subject in the energetic materials is reproducibility operation and efficiency compound or designed system. This matter could be in danger with transform Polymorphic. Thus polymorphisms between the energetic materials is located too much attention. Nitro groups on the bridging nitrogen’s can be different spatial orientation in the molecule CL-20. Depending on how its placement in the CL-20 crystals’ different crystal forms provide. CL-20 can exist as four different polymorphic phases at ambient pressure and temperature; α, β, γ and ε. The crystalline forms have different density and sensitivity that ε form because having more density and less sensitivity is more appropriate for military expenditure. In this paper various methods of preparation of CL-20 polymorphs and crystalline forms analyzes by using spectroscopic techniques, Raman, FTIR, UV, X.ray and XRD will be examined.

Temperature sensitivity is defined as the effect of primary temperature change of grain on the burning rate. This parameter influences on muzzle velocity and range of weapon. There are different methods for reducing temperature sensitivity in gun propellants, such as surface coatings, using chemical additives, controlling combustion chamber volume and changing in formulation of gun propellants. In the present paper, meanwhile introducing each of methods mentioned above, it became clear that formulation changing methods are the most effective way in comparison with other methods for reducing the temperature sensitivity of gun propellants.

The exothermic of aluminum oxidation and its relatively low price, make Al combustion desirable for utilization in solid propellant formulations. This usage aids to improve rocket performance characteristics in particular it increases the specific impulse. However, efficient ignition and burning of aluminum is a problem due to the strong oxide layer naturally formed on aluminum. To improve burn efficiency and to increment of burning rate, one route is creation of metal coatings (Fe and Ni) on Al particles. In this paper investigate influence of this approach on the ignition characteristics of aluminum.

Nitromethane (NM) is a highly energetic, detonatable and liquid organic nitro compound which may be used as a monopropellant, a bipropellant component, or a high explosive. The relatively non-toxic nature of NM, high energy content, low viscosity, ease of manufacture and handling make it an interesting prospect for present and future propulsion and explosive technologies. Nitromethane exhibits high specific impulse. It has a great potential to prepare of energetic gels. Nitromethane gels have two major applications. The gels are employed as propellant, and also used as explosives. In general, gel propellants exhibit a specific impulse comparable to liquid propellants and their performance can be increased even further through the addition of additives such as metal particles. Gel propellants have less sensitive than liquid and solid propellants. Nitromethane gel is environmentally friendly. In this paper, the applications of variety of nitromethane gels and effect of some additives on their properties will be investigated.

Liquid propellant missiles have special rule in military, space and research programs in the world. Many prices are needed for research and development of the missiles. It is very important for a designer and analyzer of the systems that what is the performance efficiency of a liquid propellant system, firstly. Then, modifying the disadvantages of the system from analyzing the results and upgrade the present system are important. In this paper, it is tried to help and deep-view to researchers and designers in liquid propellant missiles by defining two types of efficiency for the missiles and explanation of them. Moreover, on the basis of present data and results from software, these two efficiencies were calculated for known motor RD-253. Results showed that the performance and energetic efficiencies were 77.5% and 60.1%, respectively. Finally, a simple algorithm has been presented for calculating the efficiencies.

A propellant is an explosive which undergoes rapid and predictable combustion (without detonation) resulting in large volume of hot gas. This gas can be to propel a projectile. In gun propellant, the velocity of the projectile is dependent on the rate at which the gas is produced,wich is turn is dependent on the amount of chemical energy released. Today, there are lots of works on development of new gun propellants with special features. In this article meanwhile introducting some principles of gun propellants, we discussed latest innovation in gun propellants.

The gun barrel erosion is a complex physical process which is defined as the progressive damage of the bore surface. occurrence of this phenomenon of firing due to the enlargement of bore diameter results in reducing of the muzzel velocity, range and accuracy. Generally, gun barrel erosion occurs by chemical, mechanical and thermal mechanisms. Understanding of these mechanisms is useful to find methods of controling this phenomenon. So far,different methods such as steel reinforcement, applying of coatings, and liners on the bore surface,or introducting additives in the gun propellant formulation for control barrel gun have be suggested. Nevertheless, gun barrel erosion still is the most important concerns of scientists. This article discussed about theories and mechanism of gun barrel erosion and methods for controlling this destructive phenomenon.