Stochastic modelling of the growth of carbonaceous materials
type: CreativeWork
description: This thesis investigates the processes and morphologies involving key molecules that constitute carbonaceous materials, namely polycyclic aromatic hydrocarbons (PAHs), by applying a detailed particle model solved with a stochastic numerical method. In particular, a Kinetic Monte Carlo (KMC) algorithm is used to study the time-dependent transformations of PAHs in a reactive chemical environment, and thus the model is referred to as a KMC model. Numerical techniques to improve the stochastic simulation of PAHs are proposed. Regarding the PAH transformations, special emphasis is given to processes that integrate or remove curvature, as the morphology of PAHs has direct consequences on the carbonaceous materials they subsequently form. A new methodology to calculate the process rates in KMC models of PAH growth is developed. The methodology uses a combination of the steady-state and the partial-equilibrium approximation. Comparisons of the results obtained with the new methodology show good agreement with those provided by simulations using a detailed chemical mechanism under conditions relevant to flames (temperatures between 1000 and 2500 K, equivalence ratios between 0.5 and 10). The new methodology is used to calculate the rate of different stochastic processes in KMC simulations of PAH growth of premixed ethylene-oxygen flames. The results of the KMC model with the new methodology are consistent with the concentrations of species calculated using a detailed chemical mechanism for the growth of small PAHs. An algorithm to efficiently simulate the migration of partially-embedded five-member rings in PAHs is proposed. The algorithm defers the update of the computational carbonaceous structure whilst successive migration processes are sampled and is thus called the deferred update algorithm. The exactness and computational performance of the deferred update algorithm are investigated. A comparison of the algorithm with one in which the structure of the molecule is upda…
abstract: This thesis investigates the processes and morphologies involving key molecules that constitute carbonaceous materials, namely polycyclic aromatic hydrocarbons (PAHs), by applying a detailed particle model solved with a stochastic numerical method. In particular, a Kinetic Monte Carlo (KMC) algorithm is used to study the time-dependent transformations of PAHs in a reactive chemical environment, and thus the model is referred to as a KMC model. Numerical techniques to improve the stochastic simulation of PAHs are proposed. Regarding the PAH transformations, special emphasis is given to processes that integrate or remove curvature, as the morphology of PAHs has direct consequences on the carbonaceous materials they subsequently form. A new methodology to calculate the process rates in KMC models of PAH growth is developed. The methodology uses a combination of the steady-state and the partial-equilibrium approximation. Comparisons of the results obtained with the new methodology show good agreement with those provided by simulations using a detailed chemical mechanism under conditions relevant to flames (temperatures between 1000 and 2500 K, equivalence ratios between 0.5 and 10). The new methodology is used to calculate the rate of different stochastic processes in KMC simulations of PAH growth of premixed ethylene-oxygen flames. The results of the KMC model with the new methodology are consistent with the concentrations of species calculated using a detailed chemical mechanism for the growth of small PAHs. An algorithm to efficiently simulate the migration of partially-embedded five-member rings in PAHs is proposed. The algorithm defers the update of the computational carbonaceous structure whilst successive migration processes are sampled and is thus called the deferred update algorithm. The exactness and computational performance of the deferred update algorithm are investigated. A comparison of the algorithm with one in which the structure of the molecule is upda…
author: Leon Cazares, Gustavo
language: eng
keywords: Kinetic Monte Carlo, Graphene, Fullerenes, Detailed particle model, Carbonaceous nanoparticles, Soot
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/47273541-8989-40ab-bdfa-65e36a845f7d/download
license: https://creativecommons.org/licenses/by-nc-sa/4.0/
date published: 2021-05-01
date modified: 2026-07-22T22:24:17Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.77409