TOF velocity-spectra technique

ABSTRACT. The use of mass spectrometry to collect data on the decomposition chemistry of nitramine compounds and the relevance of the data to the processes occurring in these materials when they are used in actu propellant and explosive applications is discussed. The simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) and time-of-flight (TOF) velocity-spectra techniques and then-application to the study of energetic materials are discussed. The means by which these techniques enhance the amount of information obtained from more conventional mass spectrometric experiments is illustrated with studies on the evaluation of the use of appearance energy measurements to study the thermal decomposition of HMX and on the identiHcation of the HMX pyrolysis products and the determination of their gas formation rates. 

Figure 6. Illustration of the TOF velocity-spectra technique used to determine the molecular weights of the pyrolysis products contributing to the ion signals at m/z=46 from a hypothetical decomposition of HMX.

The STMBMS and TOF velocity spectra techniques enhance the use of mass spectrometry in the study of the decomposition of energetic materials. The careful control of the reaction environment in these experiments allows the identification of the pyrolysis products and accurate measurement of their gas formation rates to be made. Correlation between the observed products and the macroscopic and microscopic processes occurring within the reaction cell will allow qualitative models to be created that may explain the processes leading to the formation of the various products. Hopefully, these results may be correlated with the more limited results gathered from experiments conducted under more severe conditions (i.e. shock initiated reactions or quenched combustion experiments) to provide further insight into the mechanisms controlling the combustion of these materials under their operational conditions. 

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