Doctoral Dissertations

Keywords and Phrases

Carbon Phase Diagram; Containerless Solidification; Graphene; Liquid Carbon; Nucleation Theory; Solidification; Computational physics

Abstract

“Elemental carbon has important structural diversity, ranging from nanotubes through graphite to diamond. Previous studies of micron-size core/rim carbon spheres extracted from primitive meteorites suggest they formed around such stars via the solidification of condensed carbon-vapor droplets, followed by gas-to-solid carbon coating to form the graphite rims. Similar core/rim particles result from the slow cooling of carbon vapor in the lab. The long-range carbon bond-order potential was used to computationally study liquid-like carbon in (1.8 g/cm3) periodic boundary (tiled-cube supercell) and containerless (isolated cluster) settings. Relaxations via conjugate-gradient and simulated-annealing nucleation and growth simulations using molecular dynamics were done to study nucleation seed formation, structural coordination, and the latent heat of fusion. Atomistic results, which agree with independent DFT studies, show an energy preference for pentagon nucleation seeds, sp and sp2 coordination, and a bond defining gap in nearest neighbor histograms. Latent heat of fusion values of 1.015 ± 0.078 eV/atom (1.178 ± 0.053 eV/atom at fixed pressure) were determined which agree with values previously determined by separate experimental and computational studies. Analytical models of nucleation and growth derived from classical nucleation theory links the onset of solidification to the interface/bulk energy ratio, predict cluster size distributions, and suggest a role for saturation during slow (e.g. stellar atmosphere) cooling. The low-pressure analytical model predictions for graphene sheet density and mass weighted average are supported by experimental observations of pre-solar and lab-grown specimens”--Abstract, page iv.

Advisor(s)

Fraundorf, Philip
Medvedeva, Julia E.

Committee Member(s)

Majzoub, Eric H.
Santamore, Deborah H.
Yamilov, Alexey

Department(s)

Physics

Degree Name

Ph. D. in Physics

Comments

A dissertation presented to the Graduate Faculty of the Missouri University of Science and Technology and University of Missouri--St. Louis in partial fulfillment of the requirements for the degree Doctor of Philosophy in Physics

The author would like to thank the Missouri NASA Space Grant Consortium for funding a large portion of this work.

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2021

Journal article titles appearing in thesis/dissertation

The Rates of Unlayered Graphene Formation in a Supercooled Carbon Melt at Low Pressure

Pagination

xii, 129 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2021 Philip C. Chrostoski, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11941

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