Mechanical Activation of Al/MoO3 Thermite as a Component of Energetic Condensed Systems to Increase Its Effciency

In the present work a stoichiometric energetic compositions Al+MoO3 prepared by dry mixing and by reactive milling of micro-scale particles were investigated. Morphology, particle size and surface structure of produced powders were examined using scanning electron microscopy, atomic-force microscopy, laser diffractometry and BET analysis. DSC/TG data were processed to obtain kinetic mechanism of the reaction between Al and MoO3. The combustion rate of Al+MoO3 thermite mixture increases with pressure, reaching a maximum at ~10 atm, and then decreases with further pressure increase. The rise of combustion rate at the low range of pressure is associated with the rise in the extent of the vapour phase penetrating the pores of the pressed sample as the ambient pressure increases. However, at a higher pressure the gas formation is suppressed, and the melt formed in the combustion process can selectively wet the pores resulting in inhibition of reaction. Burning rates of mechanical activated system Al+MoO3 are two times higher then not-activated system at ambient pressure ~10 atm and 8 times higher at ~40 atm. In additional experiments, nano-scale MoO3 powder was prepared by evaporation with a subsequent condensation onto cooled plate in an inert-gas fow. Scanning electron microscopy showed that nano-MoO3 particles are absolutely spherical with mean diameter ~100 nm, and atomic-force microscopy 278 D. Meerov et al. reveals smaller particles with mean diameter ~5-30 nm. DSC/TG data showed that the nano-MoO3 starts to sublime earlier than micro MoO3. The use of nano-sized components could considerably increase the burning rates of energetic condensed systems, because of its large specifc surface, lower temperature of sublimation, and high reaction ability

Thermal Decomposition of Nitropyrazoles

AbstractFully nitrated five-membered heterocycles (pyrazoles), polynitropyrazoles in particular, have been actively studied as promising high-energy materials. Polynitropyrazoles have high density and high enthalpy of formation combined with reduced sensitivity to external stimuli. We have studied non-equilibrium processes of thermal decomposition of the first members of high-energy polynitropyrazoles row, i.e., 3,4–dinitropyrazole, 3,5–dinitropyrazole, and 3,4,5-trinitropyrazole, under atmospheric and increased pressures. The use of increased pressure allowed to reduce the influence of evaporation process of 3,5–dinitropyrazole and to determine the temperature and heat effect of its decomposition, which was found to exceed this value for HMX. For the first time evolved gas products were identified for each stage of decomposition. As a result the probable thermal decomposition pathway for the investigated materials was suggested

Combustion of Energetic Systems Based on HMX and Aluminum: Infuence of Particle Size and Mixing Technology

In this work the complex experimental investigation of the microstructure and burning parameters of HMX-monopropellant and 25%Al/75%HMX energetic systems was carried on with the particle size variation. Components, their mixtures, pressed samples, and the combustion products (agglomerates) collected from a burning surface by QPCB (quench particle collection bomb) technique were investigated. Two types of HMX particles: micro-sized (mHMX) and ultrafne (uHMX) and aluminium powders: micro- and ultra-sized (ALEXTM) were used. Morphology and particle size were examined by atomic-force microscopy (AFM), scanning electron microscopy (SEM) and BET-analysis. AFM analysis shows the ALEXTM average volume particle size is 180 nm. It was shown, that the monopropellant's burning rates of the micro- and ultra-sized HMX are almost identical in the pressure range 20-100 atm. Two mixing technologies to prepare Al/HMX compositions were used: (i) conventional "dry" mixing and (ii) "wet" technique with ultrasonic processing in diethyl ether. Applying of ultrasonic technique results in a burning rate increase up to 18% comparing to "dry" mixing (under pressure 60 atm). The highest combustion rate was determined for composition of mHMX/ALEXTM (porosity 13%). Infuence of component N. Muravyev et al. size and composition's microstructure on the burning rate of energetic systems is discussed and analyzed