Boron-Rich Composite Thermite Powders with Binary Bi2O3•CuO Oxidizers

Mixed oxide powders of Bi2O3 and CuO were prepared by mechanical milling as well as calcination of mixed nitrates. Arrested reactive milling was used to prepare boron-rich thermite composite powders with a constant equivalence ratio using these mixed oxides as oxidizers. Thermal analysis showed lower reaction onset temperatures for exothermic reactions and a greater energy release for these binary oxidizer energetic composites compared to composites with the same equivalence ratio but using either Bi2O3 or CuO as the oxidizer. The greatest effect was observed for a mixed oxidizer with 25 wt % Bi2O3. Heated filament ignition tests showed that the ignition temperatures for all mixed oxidizer composites are higher than those measured for the composites with individual Bi2O3 but lower than those for the composites with individual CuO serving as oxidizers. A weak trend of increasing ignition temperatures as the CuO content of the binary oxidizer increases is noted. Correlations between thermal analysis and ignition experiments suggest the early oxidation onset as the reaction leads to ignition. Particle burn times as determined by laser-ignited single particle combustion tests are near 400 mu s for 1 mu m particles, less than for similarly sized pure boron, but with no discernible effect of oxidizer composition.

Automated summary

Mixed oxide powders of Bi2O3 and CuO were prepared by mechanical milling and calcination of mixed nitrates. Thermal analysis showed lower reaction onset temperatures and greater energy release for composites with these mixed oxides as oxidizers compared to composites with individual Bi2O3 or CuO. The composites with 25 wt % Bi2O3 as oxidizer exhibited the greatest effect.