Chemical Mechanisms of Shock Initiation of NTO.

A powerful analytical tool has been developed for in-situ, real-time measurement of the thermally and mechanically induced transient decomposition processes of energetic materials, and has been applied to the new, insensitive high explosive, nitro-1,2,4-triazol-5-one NTO. Modification of the vacuum chamber of a laser-desorption mass spectrometry apparatus has enabled us to perform simple-shear and compressive fracture of pressed pellets directly beneath the sampling region fragments spontaneously emitted from fractured NTO pellets are measured by single-photon ionization SPI time-of-flight mass spectrometry. The fracture-induced fragments of NTO are dominated by a single peak, mz 99, which is completely absent in either the thermal- or laser-desorption spectra obtained in the same apparatus. This difference suggests that under the marginal stress of subcritical mechanical fracture, intermediates of mass 100 andor 101 are diverted to the closed-shell, relatively stable species at mass 99, which then tends to accumulate, rather than going on to produce a next generation of unstable intermediates at mz 85, 71, and 43. Thus, in its first use, this combination of techniques has enabled identification of intermediates not previously observed in NTO decomposition and allowed us to propose a reasonable sequence of reactions that involves all of these intermediates, reconciles a substantial portion of previous slow thermal decomposition data, and potentially explains the initiation insensitivity of NTO as resulting from diversion to a relatively stable dead-end species.