Development of a Dual-Spectroscopic System to Rapidly Measure Diisopropyl Methyl Phosphonate (DIMP) Decomposition and Temperature in a Reactive Powder Environment

TL;DR

This study introduces a dual-spectroscopic system combining IR and TDLAS techniques to rapidly monitor DIMP decomposition and temperature in reactive environments, aiding chemical weapon defense research.

Contribution

It develops and demonstrates a novel dual-spectroscopic setup capable of real-time monitoring of chemical decomposition and temperature in energetic material environments.

Findings

PRiMIRS achieves high SNR at Hz frequencies

TDLAS monitors temperature rises up to 230°C within seconds

Spectral signatures of DIMP decomposition products are detected in reactive conditions

Abstract

The development of systems to measure and optimize emerging energetic material performance is critical for CWA defeat. This study documents a combination of two spectroscopic systems designed to monitor decomposition of a CWA simulant and temperature. The first system is a custom benchtop Polygonal Rotating Mirror Infrared Spectrometer (PRiMIRS) incorporating a fully customizable sample cell to observe decomposition of DIMP as it interacts with combusting composite metal particles. The second is TDLAS used to monitor increases in background gas temperatures as the composite metal powders combust. The PRiMIRS system demonstrates a very high SNR at Hz, reasonable SNR when operating at 100 Hz, and capabilities of resolving spectral features with a FWHM resolution of 15 cm^-1. TDLAS was able to monitor temperature rises between room temperature and 230C +/- 5C at 100 Hz.For testing, liquid DIMP was inserted in a preheated SS cell to generate DIMP vapor and (Al-8Mg):Zr metal powders were ignited in a SS mount with a resistively heated nichrome wire at one end of the cell. The ignited particles propagated across the cell containing DIMP vapor. The path averaged gas temperature in the preheated SS cell rises rapidly (100ms) and decays slowly (< 5 s) but remains below 230C during particle combustion, a temperature at which the thermal decomposition of DIMP is not observed over similarly short timescales (seconds). However, when combusting particles were introduced to the DIMP vapor (heterogenous environment), spectral signatures indicative of decomposition products such as IMP and IPA were observed within seconds.