Mechanism of metal surface nitridation of ammonia combustion at elevated pressure

Ammonia is a molecule composed of nitrogen and hydrogen. Ammonia is potentially useful as a fuel that could help meet the nation’s energy demands. It has a high volumetric energy density, and it is relatively easily transported and stored. However, some challenges must be addressed before using ammonia as a fuel. One challenge is that the nitrogen atoms in ammonia can react with metal surfaces of the combustion machinery, which can produce voids on the surface. The process is called nitridation, and it can lead to degradation of the mechanical and thermal properties of combustor components. Despite growing interest in using ammonia as a fuel, nitridation on metal surfaces during ammonia combustion has not been studied extensively. This project will conduct experiments that will use laser diagnostics in a high-pressure ammonia combustor to understand the underlying chemical and physical mechanisms of nitridation. The chemical compounds that form during combustion will be measured, and their effects on nitridation will be identified. The project will also develop a computational model that integrates quantum chemistry data, machine learning, and simulation tools to investigate nitridation and high temperatures and pressures. The project will provide training and mentorship opportunities for postdoctoral researchers, graduate students, and high school students that will help cultivate the next generation of leaders in energy engineering. This project will explore new mechanistic hypotheses for metal surface nitridation and porosity generation during ammonia combustion. The research team will build a novel high-pressure, well-stirred turbulent combustor coupled with advanced in-situ and operando diagnostics to systematically test these hypotheses and elucidate the nitridation and morphological evolution of carbon steel and nickel surfaces. In parallel, an ab initio machine-learning quantum chemistry molecular dynamics (aML-MD) framework will be developed to predict metal surface nitridation under combustion-relevant conditions, with experimental validation. The outcomes of the proposed work will support the transition to hydrogen and ammonia energy systems, enable new technologies for materials manufacturing and chemical synthesis, improve energy efficiency, and strengthen advanced energy technologies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2552244 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Yiguang Ju | Institution: Princeton University, PRINCETON, NJ | Award Amount: $400,000 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2552244 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2552244.html