Model Studies of CBES Decomposition

Abstract : The explosive decomposition of cryogenic films of fluorine azide, FN3, has been studied using a variety of experimental techniques. Although the amounts of NF(a) and NF(b) produced upon film combustion was found to be below the detection limits of our emission spectrometer, indirect evidence of the presence of these species has been recorded. The presence of CN(B-X) emission and the absence of CN(A-X) implied B state population via resonant energy transfer from a combustion species, having at least 3.2 eV of excitation. Also, using schlieren photography and an optical scattering probe it was deduced that the minimum burn velocity of of the material is 1.6 mm/microsecs. From these observations a simple model involving shock induced unimolecular decomposition of FN3 was developed to describe the detonation of the films. Consistent with the model, the burn velocity could be moderated via addition of high heat capacity materials. Also, the burn velocity was found to be dramatically altered by low level impurities which appear as a result of the thermal decomposition of FN3. Since the pure azide has an exceedingly high specific impulse, relative to monopropellants, and the burn rate of this material is broadly tunable via additives, the results of the above studies indicate that FN3 can be developed for use as a high performance monopropellant. Keywords: Fluorine azide; Nitrogen fluoride; Chemically bound excited states (CBES); Diatomic molecules detonation; Decomposition and dissociation reactions; Electronic and vibrational excitation; Metastable states; Energy storage; Transfer and pooling; Emission spectra; Kinetics; Potential energy curves; High impulse propellants.