ULTRAFAST BROADBAND MIDINFRARED ABSORPTION SPECTROSCOPY ON SHOCKED ENERGETIC MATERIALS_v2.pdf (53.02 MB)
0/0

ULTRAFAST BROADBAND MIDINFRARED ABSORPTION SPECTROSCOPY ON SHOCKED ENERGETIC MATERIALS

Download (53.02 MB)
thesis
posted on 16.04.2020 by Michael S Powell
Balancing increased safety against detonation performance is paramount for new explosive energetic materials in the development process. Often these two requirements are in opposition to each other. Sensitivity tests to external stimuli are used to determine how safe an energetic material is to phenomena such as impact, heat, or friction. Meanwhile, detonation performance is assessed by the maximum pressure and shock velocity induced from chemical reactions. Tailoring the performance while maintaining safety of the explosive would be possible with knowledge of the chemical reactions that functional groups provide during detonation. Current knowledge of the chemical reactions that occur during detonation is limited. Several mechanisms have been suggested for first step reactions throughout the detonation process for energetic molecules; however, no single chemical pathway has been irrefutably substantiated by experiments. Alternatively, models can provide insight into the types of reactions that may transpire, but lack direct experimental comparisons. If experiments and models could be compared at the equivalent time and length scales, then measurements could guide the physics and chemistry assumptions present in models. Experiments presented in this document bridge that gap by using an ultrafast laser system to generate shocks in samples and spectroscopically probe vibrational and electronic absorption changes that occur during shock compression. A review of how to turn a benchtop chirped pulse amplifier into a shock physics and chemistry laboratory is first presented. Applications of the spectroscopic techniques developed were then applied to trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN) during shock compression. Mid-infrared absorption results for shock compressed TNT and PETN were compared to current suggestions on chemical pathways and inconsistencies were present for both materials. It is suggested that a carbon-carbon bond breaking mechanism is present for PETN, and a hydrogenic stretch like hydroxyl or amide bond formation mechanism is suggested for TNT based on the MIR absorption measurements. Recommendations for future experimental thrusts are also provided. The results provided in this document could be directly compared to simulations to refine the assumptions present in models.

Funding

PC@Xtreme - Predictive Chemistry & Physics at Extreme Temperature and Pressure: Molecules, Crystals and Microstructures

United States Department of the Navy

Find out more...

LANL LDRD PROGRAM 20170070DR

History

Degree Type

Doctor of Philosophy

Department

Mechanical Engineering

Campus location

West Lafayette

Advisor/Supervisor/Committee Chair

Steven Son

Advisor/Supervisor/Committee co-chair

Alejandro Strachan

Additional Committee Member 2

Christopher Goldenstein

Additional Committee Member 3

Robert Lucht

Additional Committee Member 4

Shawn McGrane

Licence

Exports

Logo branding

Licence

Exports