Abstract:
Chemical time delay detonators are used widely in mine blasting
applications. In order to achieve effective blasting, detonations must follow
a precisely controlled timing sequence in a specified firing pattern. Silicon fuelbased pyrotechnic compositions are widely used in mining detonators
and are well studied. However, some of these formulations are deemed
to be problematic, as they contain heavy metals which are bio-accumulative
and toxic to the environment. Therefore, there is need to explore alternative
formulations which are suitable for these applications. Manganese-fueled
systems are attractive due to their metallic properties and several oxidation states
of the manganese fuel. This study focused on characterizing the burn properties
of Mn/Bi2O3 compositions for slow to intermediate time delay applications.
The compositions supported combustion in the 25 to 55 wt.% Mn range in an inert
helium atmosphere. Burn rates between 2.5 and 11.2 mm·s–1 were recorded
in open burn tests, whilst closed burn tests in glass tubes resulted in burn rates
of 6.3 to 11.2 mm·s–1. Both X-ray diffraction analysis of the reaction products
and thermodynamic simulations confirmed that MnO and Bi are the main
reaction products, with unreacted Mn and Bi2O3 also being detected. Thissuggests
that the dominant reaction for this composition is a simple thermite-type reaction.
