Effect of Chemistry and Particle Size on the Performance of Calcium Disilicide Primers. Part 1 - Synthesis of Calcium Silicide (CaSi2) by Rotary Atomization

摘要

Rotary atomization was used to synthesize spheres of four calcium silicide (CaSi2)-based compositions in order to understand issues relative to primer performance for military applications. Elemental silicon and calcium were used to synthesize the line compound CaSi2 or the eutectic composition between CaSi2 and silicon (Si). Iron (Fe) was added to form FeSi2 as a secondary phase in selected compositions. In one composition, it was shown that a commercially available CaSi2 material, containing FeSi2, could be used as one of the starting compositions. Rietveld analysis was used to show that CaSi2 polytypes in the synthesized materials consisted primarily of 6R, with less 3R and some hexagonal material. As synthesized materials had low surface areas (=0.1 m2/g), but short milling times were used to increase the surface area by an order of magnitude. Higher surface areas, as expected, showed faster oxidation. Chemistry and particle size characterization are discussed relative to military specifications for primers. Synthesized and existing current production lot of calcium silicide was mixed in FA874 primer mixtures. Peak pressures, pressure rise time, and ignition voltage showed no differences between the materials, demonstrating a pathway for producing synthetic primer additives.