Metal/metal oxide nanoparticles (M/MOx NPs) can be rapidly dispersed into the atmosphere through gas-phase reactive processes such as combustion and detonation of metal NPs used as solid-state fuels, propellants and explosives. The energetic behaviors of metal NPs stem from their enhanced reactivities due to large specific surface areas, metastable structures and small diffusion length scales at nanoscale fuel-oxidizer interfaces. But such unique physico-chemical properties at nanoscale also demand a detailed investigation into the air-borne proliferation of M/MOx NPs. In turn, the study entails a fundamental understanding of the thermodynamics and kinetics of background parameters that tailor the sizes, morphology, composition and structure of M/MOx NPs during their growth and evolution via aerosol phase. Gas-phase generation of M/MOx NPs involve rapid cooling of supersaturated vapor (monomers) that leads to nucleation and birth of a stable critical cluster followed by the growth of the critical cluster via competing coagulation/coalescence processes and simultaneous interfacial reactions including surface oxidation. Experimental techniques to study such complex processes with diverse time scales is challenging. Hence, this talk presents a series of hi-fidelity kinetic Monte Carlo models (KMC) developed by us as powerful tools for detailed mechanistic studies of these processes in an efficient and robust manner. It will start with the gas-phase homogeneous nucleation modeling built on the Classical Nucleation Theory (CNT) of Gibbs’ free energy-driven collisional processes (condensation/evaporation), and discuss the validity of steady-state nucleation rates.1 This will be followed by KMC-based studies on the non-linear interplay between competing non-isothermal coagulation/coalescence processes leading to surface oxidation and fractal-like morphologies of NPs during their evolution in aerosol phase.2,3 Simulation results for Al, Si and TiO2 NP case-studies in air under different growth conditions (temperature, pressure, particle volume loading)1,2,3 will be used to show the efficacy of the model in determining optimal process variables for tuning structural and chemical make-up of M/MOx NPs.

Kinetic Monte Carlo models to study nucleation and evolution of metal/metal oxide nanoparticles grown via aerosol route

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.