Aging Mechanism of Zirconium Potassium Perchlorate Charge in Pyrotechnic Mechanical Devices

摘要

The aging mechanism of zirconium potassium perchlorate (ZPP), which is one of the primary charges in pyrotechnic mechanical devices, was investigated in terms of spontaneous aging and aging under high-humidity conditions. Differential scanning calorimetry experiments revealed an exothermic oxidation reaction related to explosion. The initiation time for the spontaneous oxidation was estimated using commercial software from Advanced Kinetics and Technology Solutions. The initiation time at a storage temperature of 220 degrees C was greater than 500 years, indicating that ZPP itself is hardly aged spontaneously at ambient temperature. To confirm the effect of the major external factor (i.e., humidity), accelerated aging of ZPP was performed at 70 degrees C under 100% relative humidity (RH). The relative heat of combustion decreased gradually over 16 weeks. X-ray photoelectron spectroscopy was performed, and ZPP samples were characterized based on the 3d(5/2) and 3d(3/2) peaks at 183 and 187 eV, respectively, which are related to the Zr-O orbital electrons. The intensity ratio between the two peaks (or the overall peak shape) continuously changed with increasing aging time in the spectra of samples aged under 100% RH; that is, surface oxidation reactions occurred continuously under a continuous supply of moisture. Transmission electron microscopy in conjunction with energy-dispersive spectroscopy also confirmed the formation of oxide shells and indicated that their thickness increased to 87 nm over 16 weeks. Thus, the humidity aging reduced the overall potential energy of ZPP via the preconsumption of reactants by oxidation.