Investigation of the Phase Stabilizing Effect of 4% Potassium Fluoride on Ammonium Nitrate.

摘要

Ammonium nitrate is an interesting oxidizer in the field of propellants and explosives. The drawbacks of the substance are caused by its polymorphic properties. It crystallizes at ambient pressure in 5 modifications. Some phase transitions take place at temperatures, which occur under normal storage conditions. These transitions are connected with volume changes that influence severely the properties of products containing ammonium nitrate. Samples of ammonium nitrate containing 4 weight % Potassium Fluoride were investigated during cycling the material between -70 and 80 C. The incorporation of 4% KF into the ammonium nitrate lattice extends the stability range of phase III to deeper temperatures. The results differ in dry and humid samples. In dry samples phase III changes directly into phase V on cooling at temperatures between -10 and -65 C. The transitions are not complete. Phase IV is excluded. In the humid samples the transition into phase V is complete occuring at higher temperatures between 5 and -10 C. Besides, phase IV cannot be excluded reliably. The differences can be explained by a retarded nucleation of phase V in the dry samples. On heating the transition V/IV occurs in all samples at temperatures slightly above 0 C followed by the transition IV/III at 30-35 C. Due to the extended stability range of phase III a direct transition V/III is observed in the dry samples. (AW)