(644a) Effect of Boron Concentration on Properties of Reactive Al•B•I2 Powders Prepared By Mechanical Milling

Energetic materials with biocidal combustion products are of interest for biological agent defeat applications.  Research has focused on modifying both fuels and oxidizers with additives containing halogens.  Such modified components are expected to produce halogenated reaction products which inactivate the aerosolized microorganisms.  Additionally, such materials must be thermally stable so they can be stored and processed along with other components of energetic systems.  As for other energetic materials, their sensitivity to impact, spark, friction, and other common ignition stimuli needs to satisfy current standards.

Recently, a range of Al-based composites, Al•I₂ [1], Al•B•I₂ [2], and Al•CHI₃ [3], all containing approximately 20 wt. % of iodine was prepared by mechanical milling and tested in both combustion and bio-aerosol inactivation experiments.  It was observed that particles of Al•B•I₂ (Al:B wt. ratio = 8)had the highest ignition temperatures and longest particle burn times, but their combustion products were the most effective in inactivating bioaerosol.   Effect of boron concentration on stability, combustion, and biocidal effectiveness of Al•B•I₂ composites is addressed in this work.  A systematic milling study is conducted on preparation of Al•B•I₂ composites with variation in Al:B wt. ratio from 0.14 to 7.  The iodine content was fixed at 20 wt. %.  Using thermal gravimetry performed under inert and oxygen environments, the stability and oxidation mechanisms of the prepared material were assessed.  The most stable composites contained Al:B wt. ratio of 1 and 0.6, which were further characterized for ignition temperatures and combustion dynamics.  Results showed composites with Al:B wt. ratio of 1 and 0.6, had lower ignition temperatures and comparable particle burn times to that of Al•B•I₂ (Al:B wt. ratio = 8).

References

[1] Zhang et al., Journal of Physical Chemistry C. 2010, 114, 19653.

[2] Aly et al., Combustion and Flame. 2014, 161, 303.

[3] Abraham et al., Advanced Engineering Materials. 2014, Article in Press.