Chemical kinetic investigation of the thermal decomposition of energetic materials: ammonia borane, ammonium perchlorate & hmx-tagzt
Open Access
- Author:
- Chatterjee, Tanusree
- Graduate Program:
- Mechanical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 18, 2020
- Committee Members:
- Stefan Thynell, Dissertation Advisor/Co-Advisor
Stefan Thynell, Committee Chair/Co-Chair
Adri van Duin, Committee Member
Jacqueline O’Connor, Committee Member
Joseph F. Horn, Outside Member
Daniel Connell Haworth, Program Head/Chair - Keywords:
- Ammonia borane
Quantum mechanics
Hydrogen release
Reaction pathway
perchloric acid
oxygen release
numerical simulation
HMX
TAGzT
TGA
FTIR
thermal decomposition
nitramine-based energetic materials - Abstract:
- Energetic materials such as propellants which are burned to produce thrust in applications like guns, rockets/space propulsion systems, automobile air bags and ejection seats of airplanes, play a critical role in meeting the performance and safety requirements by generating high pressure within a short duration of time. Propellants used in practical applications, generally consists of two or more energetic ingredients. To ensure that the above-mentioned devices are well designed, it is critical to understand the thermal decomposition (or combustion) behavior of energetic ingredients that comprise the propellants. It is also of paramount importance to understand the chemistry involved during decomposition of these energetic ingredients which will enable a knowledge-based improvement and engineering of propellants. In this dissertation using synergistic application of experimental and computational methods, three different energetic materials are studied: Ammonia borane (AB); Ammonium perchlorate (AP) and HMX-TAGzT. Ammonia borane (AB) is a hypergolic rocket fuel used in liquid propellants and a potential hydrogen storage medium. Although several studies have been undertaken over the years to understand the chemical kinetics involved during AB decomposition, it is still not well understood. The reaction pathways developed so far are primarily based on the experimental observations of a limited set of chemical species and there exists no consensus. In this work, a detailed AB reaction mechanism was developed using thermolysis experiments and quantum mechanics (QM) calculations to explain the formation of species observed during experiments, reconciling the existing conflicts regarding the initiation step, as well as the pathways of H2 formation during decomposition. The developed reaction mechanism not only explains the experimental observations, but also provides information which are difficult to obtain only by performing experiments. Ammonium perchlorate (AP) is one of the most common oxidizers used in solid composite propellant. Owing to high-pressure deflagration limit (PDL) and very fine structure of AP flame, minimal amount of experimental data is available till today. Hence, numerical simulations play critical role in order to understand the combustion phenomenon of AP monopropellants. Although existing combustion models use detailed reaction mechanism for gas phase, chemical kinetics involved in AP melt layer or condensed phase is still modeled using global/semi-global reactions which is one of the major stumbling blocks in modeling AP combustion. In this work, a liquid phase reaction mechanism for perchloric acid (HClO4) decomposition is proposed based on QM calculations. HClO4 which is one of the primary sublimation products of AP is experimentally observed during the ignition and combustion of AP (NH4C1O4)-containing solid propellants in both gas and condensed phase. Hence, this work can be viewed as a first step towards development of detailed liquid-phase reaction mechanism for AP combustion modeling. HMX is a nitramine-based high-explosive fuel which is often used in solid composite propellants to increase energy output and TAgzT is commonly used as burn rate enhancer for nitramine-based propellants. Although significant amount of work has been done to understand the thermal decomposition behavior of HMX and TAGzT as a monopropellant, the interaction of these two energetic materials was not studied previously. In this work, using thermolysis experiments (TGA/DSC coupled with FTIR spectroscopy), thermal decomposition characteristics of HMX-TAGzT mixtures at low and moderate temperatures (373-673 K) using low heating rates (<50 K/min) were studied. Along with experiments, quantum mechanics (QM) calculations were also performed to identify important reactions responsible for increased rate of HMX decomposition in presence of TAGzT.