Spherical composite powders combining boron with ammonium and potassium nitrates

Spherical composite powders of boron and various combinations of ammonium nitrate (AN) and potassium nitrate (PN) were prepared by emulsion assisted milling. Combined results of powder X-ray diffraction and thermal analysis show that milling effectively causes the same nitrate phases to form as would be expected from solution synthesis. Thus, the crystal structure of AN can be modified mechanochemically with added PN – improving its stability as a gas-generating oxidizer. Under thermal analysis conditions, the composite powders broadly show mass losses of the AN and PN components in sequence. The reaction between the boron fuel and the oxidizer decomposition products can be optimized using the mixed oxidizers. The powders are further characterized by ignition and combustion experiments. Even small additions of PN to AN provide effective control over ignition temperatures and combustion properties. Experiments using the laser-induced air shock from energetic materials (LASEM) method show also that relative shock velocities are larger for compositions with mixed oxidizers.