STUDY OF REACTION DRIVEN PROCESSES USING MOLECULAR DYNAMICS: APPLICATIONS OF REAXFF FOR COMBUSTION CHEMISTRY AND MATERIAL SYNTHESIS
Open Access
- Author:
- Lele, Aditya
- Graduate Program:
- Mechanical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 13, 2021
- Committee Members:
- Jacqueline O'Connor, Major Field Member
Randy Vander Wal, Outside Unit & Field Member
Yuan Xuan, Major Field Member
Adri van Duin, Chair, Minor Member & Dissertation Advisor
Daniel Connell Haworth, Program Head/Chair - Keywords:
- ReaxFF
Molecular Dynamics
Combustion
2D-materials
Biofuels
CVD
Material synthesis
hBN
soot
pyrolysis - Abstract:
- The reactive molecular dynamics method bridges the gap between quantum chemistry and computational fluid dynamics (CFD) methods. The ReaxFF reaction dynamics methods have been successfully employed in many areas, including combustion, heterogeneous catalysis, atomic layer deposition. The work presented here focuses on the application of ReaxFF for combustion chemistry and material synthesis-related applications. Combustion has been a major source of energy generation for humankind and will remain so in the near future. Hence it is very important to make it as less detrimental as possible for the environment. The focus of the present study is on two critical aspects of combustion, namely pyrolysis and soot formation. The ReaxFF reactive force field method has been used to investigate and obtain an atomic-level understanding of these two complex phenomena. The investigation of the initial pyrolysis chemistry of newly synthesized potential jet fuels with relatively uncommon structures is presented first. We successfully use ReaxFF to understand the critical steps of their initial reaction chemistry. Reactive molecular dynamics simulations are also used for our efforts in the investigation of nascent soot formation. Here, we present the results for an exploratory ethylene simulation mimicking an experimental atomic force microscopy (AFM) study. These simulations manage to capture the majority of the structures observed in the experimental study. The second part of the study focuses on the polycyclic aromatic hydrocarbons (PAH) formation in novel biofuels and the well-established JP-10 jet fuel, giving us useful atomistic insights into their initial stages of soot formation. The work also explores an application of ReaxFF on the effect of pressure, temperature, and mixture on the combustion of fuel components. The comparison of ReaxFF super-critical condition mixture simulations of n-dodecane and toluene with existing chemical kinetic mechanisms reveals the limitations of the existing kinetic mechanisms. Here, the ReaxFF simulations could serve as a useful guide to further improve the existing reaction mechanisms. Then the focus shifts to a material synthesis application. In particular, the ReaxFF force field reparameterization for gas-phase B-N chemistry. 2D boron nitride materials are isomorphs of carbon nanomaterials and hold promise for electronics applications owing to their unique properties. We reparametrized an ammonia borane combustion force field to correctly model the formation of boron nitride nanostructures (BNNS) using BN and HBNH as precursors. The work also demonstrates the capability of the new force field by studying the effect of operating conditions on the formation of BNNS.