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

 

Dmitry MEEROV, Dmitry IVANOV, Konstantin MONOGAROV,
Nikita MURAVYEV, Alla PIVKINA and Yurii FROLOV

Semenov Institute of Chemical Physics
Russian Academy of Science,
Kosygin St. 4, 119991 Moscow, Russia


Igor FOMENKOV
Zelinsky Institute of Organic Chemistry
Russian Academy of Science,
47 Leninsky Prospect, 117913, Moscow, Russia


Abstract: 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.

Keywords: thermites, burning rates, nano-MoO3