Studies on characterization and burning of red phosphorus-based smoke compositions

摘要

Burning of red phosphorus leads to attenuation of electromagnetic radiation in the visible and infrared regions. Red phosphorus and potassium nitrate-based compositions exhibit favorable smoke screen formation with high obscuration characteristics at low oxidizer content as indicated by radiometric studies. The rapid vaporization of excess red phosphorus leads to quick dispersion in air. The obscuration is mainly due to formation of P_2O_5 followed by its reaction with moisture/humidity in the atmosphere. The compositions are highly sensitive to impact and friction, and oxidation of phosphorus occurs in moist air. Coated red phosphorus is used to suppress excess flammability and prevent dust formation. The thermograms of coated red phosphorus and smoke composition show the general trend of thermal stability of the mixtures under specified experimental conditions. The SEM photographs of the smoke composition of the sliver sample indicate bubbled surfaces for entrapped phosphorus vapors as well as valley-like holes from which the vaporized phosphorus escaped through the surface. Hot-stage microscopy indicates escape of red phosphorus before complete oxidation. Although loose composition may absorb moisture because of the porous structure, the moisture ingress into the filled munitions where particles are compacted is expected to be less. The data indicate that processing of red phosphorus-based compositions needscontrolled humidity conditions and storage in hermetically sealed systems to avoid moisture ingress.