The Oxidation of Diamond
Date
2001-02
Authors
Journal Title
Journal ISSN
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Publisher
New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.
Abstract
The objective of this project is to develop a fundamental understanding of the oxidation
behavior of diamond. Research efforts on oxidation and phase transition of diamond
have been undertaken through a combination of experimental and computational
approaches. Heat treatments are carried out on CVD diamond film ET100, manufactured
by Norton Diamond Film, in a wide temperature (420 to 1500 oC) and oxygen partial
pressure range (from 6x10-10 to 95 kPa). Theoretically, surface chemisorption and
reconstruction of diamond surfaces are investigated using density functional theory.
Taking both oxidation and phase transition into consideration, we propose that diamond
can take either one of the two different paths during the heat treatment of diamond in
oxygen at elevated temperatures: 1) direct gasification of sp3-bonded carbon; and 2) sp3
to sp2 phase transition (surface reconstruction) first, then gasification of sp2-bonded
carbon. Diamond oxidation and phase transition are results of these two competing
mechanisms. We further suggest that surface oxygen coverage and temperature are the
two most influential factors that govern the surface reaction of diamond. The reaction
between oxygen and diamond (111) surface at ambient pressure is summarized as:
• Room temperature and 0 % coverage:
The (111) surface reconstructs to (2x2) or (2x1) reconstruction. This occurs without
any change of the bond character.
• Elevated temperature (~ 700 oC to 1500 oC), zero coverage:
The bond character of diamond (111) surface changes from sp3 to sp2. Thus, diamond
goes through a phase transition and forms amorphous, sp2-bonded carbon. If the
temperature reaches 1600 oC or higher, the amorphous carbon graphitizes and
becomes crystalline.
• Elevated temperature (~ 700 oC and higher), low coverage (up to 20%):
Diamond converts to amorphous, sp2-bonded carbon first. Then the oxidation of
carbon proceeds, yielding gaseous products CO and/or CO2.
• Elevated temperature (~ 500 oC and higher), high coverage (more than 50%):
Diamond converts to amorphous, sp3-bonded carbon first. Then the oxidation
proceeds, yielding gaseous products CO and/or CO2.
Description
Advisory committee members: Scott Misture, Alastair Cormack, Robert Condrate. Dissertation completed in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in Ceramics at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University
Type
Thesis