مجله تحقیق و توسعه مواد پرانرژی
سال هفتم شماره 3 (پیاپی 15، زمستان 1390)

Detecting explosives is a challenging task because of a number of factors, such as the low vapor pressures of most explosives, frequent introduction of novel explosive compositions, concealment and weapon delivery schemes. Also, selective and sensitive detection of explosive has received considerable attention for environmental monitoring/ restoration and national security applications. Nano sensors with increased sensitivity and selectivity and the ability to operate in a multimodal platform offer a potential paradigm for deploying a large number of sensors for detection. This review is intended to highlight recent advances in vapor detection of explosives by enabled nanotechnology sensors.

Tetrazoles are class of high nitrogen heterocycles. These compounds have C-N and N-N chemical bonds and thus have positive heat of formation, high density and specific high impulse. Tetrazoles have also high potential energy and low sensitivity to friction and shock and thus are used as green energetic materials in propellants, gas generators, explosives and pyrotechnics. Some of tetrazole derivatives are used as green primes now. Tetrazoles have some advantages compared to classical high energy materials such as lower toxicity, easier synthesis, cleaner and environmentally friendly decomposition. As a result they are good alternative for normal energetic materials. These compounds also are used as agricultural and pharmaceutical.

Conventional propellants (single base, double base and triple base) due to accidental initiation cause to catastrophic disasters for crews and lose of costly equipments. During recent times, for reducing sensitivity of ammunitions, It have been efforts for development of LOVA propellants. The concept of LOVA gun propellant is evolved by formulation a propellant which is least sensitive to impact friction and heat stimuli and meeting the ballistic requirements satisfactorily. LOVA propellant are developed using a reduced amount of nitric ester (which are highly sensitive constituents).in their propellant formulation as well as, using newer ingredients such as inert binders. In order to replace, nitroglycerine (containing nitric ester) and a part of nitrocellulose, we can use micronized RDX as an energetic factor. In this paper, we have considered formulation, ballistic parameters, mechanical characteristics, process technology, erosion and aging phenomena of this kind of novel propellant.

Dimethyl amino ethane azide (DMAZ) is a good replacement of hydrazine derivatives in aerospace industries. It is produced from the reaction between dimethyl amino ethyl chloride and aqueous sodium azide. DMAZ is formed in organic phase with a purity of at least 90%. High pure DMAZ is necessary for aerospace utilization. Thermal sensitivity of DMAZ leads the purification procedure to be performed at low temperatures. So, the Distillation at sub-atmospheric pressures is a good choice for this purpose. In this paper, effect of various parameters such as temperature and pressure on the distillation time and loss of material and final purity of DMAZ was studied in regular packed column, known as vigorous column, and optimized conditions were found.

Plasticizers are the most important ingredient of gun propellant. They have essential role in control of ballistic and mechanical properties of gun propellants. Development of new gun propellants requires study of energetic plasticizers effect. There are lots of researches around the synthesize and application of energetic plasticizers resulting to the production of nitro, nitrato, fluoro nitro, fluoro amino and azido based energetic plasticizers. Using these plasticizers in propellants causes the modification of energy and mechanical strength. In this article, some fundamentals properties of plasticizer, such as glass transition temperature and migration of plasticizers, are explained and then some of the novel plasticizers for gun propellants such as Bu-NENA, DANPE, NF, BDNPA/F, DNDA57 are introduces and their effects on ballistic and other properties of gun propellants are considered.

Gel propellants, in comparison with liquid propellants, have some significant advantages. Atomization and then combustion of gel propellants can provide required thrust for propulsion of missiles. Characteristics of atomization and combustion of propellant depends on its rheological properties. In this paper the rheological properties, atomization pattern and combustion processes of liquid and gel propellant are presented. Gel propellant is a shear thinning fluid, so its viscosity is decreased with increasing shear rate. Thus, suitable injectors for this kind of propellant are those, that are able to apply high shear rates on propellant during passing through the injector. Smaller diameter of atomized droplets, lead to faster evaporation and more efficient combustion, so the combustion process can be completed in a shorter length of thrust chamber.

Ionic liquids (ILs) have received considerable attention as green solvents in organic synthesis and advanced materials. Recent interest was focused on energetic ILs with the aim to reduce the overall exposure to hazardous and potential toxic materials. Compared with traditional energetic compounds, such as TNT, HMX, and RDX, energetic ILs have several advantages, such as excellent stability, negligible vapor pressure, higher density and little or no vapor toxicity. In addition, their properties are readily tuned through independent modification of both cationic and anionic components. The approach significantly increases the numbers of compounds available.