The Oxidation of Graphite. I. The Observation of Oxidation on Synthetic Graphite Before and After Irradiation

Journal Article · Tue Jul 30 04:00:00 EDT 1963 · Proceedings of the Royal Society. A. Mathematical, Physical and Engineering Sciences

DOI:https://doi.org/10.1098/rspa.1963.0139· OSTI ID:4690203

Dawson, I. M.; Follett, E. A. C.

Ultra-thin sections of a synthetic graphite were examined in the electron microscope before and after oxidation in air at a temperature of 500 deg C. In unirradiated material, micrographs of individual areas showed that oxidative attack occurred at grain boundaries and at pores between individual crystallites. Parallel experiments on material that had been irradiated to a dose of 8.7 x 10¹⁹ n.v.t. again showed etching at pores and at grain boundaries, but, in addition, in the majority of specimens, a shallow surface pitting of the entire (0001) faces of the individual crystallites took place. The density o these shallow pits varied from 5 x 10 ¹⁰cm² to 5 x 10¹¹cm². Variations in reaction rate we re observed and were traced to impurity which, especially appeared to be absorbed only at pores and intercrystallite boundaries, oxidation effects being observed only at these sites. In irradiated material impurity was also absorbed at sites on the (0001) crystal faces where oxidation produced etch pits of widely varying depth and density. Channelling of the (0001) layer nets occurred in both irradiated and unirradiated specimens. Annealing of the irradiated graphite at 650 deg C for 1 h produced no significant change in the pattern of attack by oxygen. The observed etch pit density measured on the (0001) layer nets was 8 x 10¹⁰ cm². A mechanism for pit formation relating pit density and vacancy content is proposed. The general appearance of irradiated samples differed from the unirradiated in that the well-defined moire patterns characteristic of thin sections of synthetic graphite were absent in irradiated samples, but reappeared when the samples were annealed at 650 deg C. This change is related to the known behavior of interstitial atoms in graphite on annealing the materials.

• Research Organization: Glasgow Univ.
• Sponsoring Organization: USDOE
• NSA Number: NSA-17-032688
• OSTI ID: 4690203
• Journal Information: Proceedings of the Royal Society. A. Mathematical, Physical and Engineering Sciences, Journal Name: Proceedings of the Royal Society. A. Mathematical, Physical and Engineering Sciences Journal Issue: 1358 Vol. 274; ISSN 1364-5021
• Publisher: The Royal Society Publishing
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AIR
ANNEALING
DEFECTS
ELECTRON MICROSCOPY
ETCHING
GRAIN BOUNDARIES
GRAPHITE
IMPURITIES
INTERSTITIALS
IRRADIATION
LATTICES
MECHANICS
NEUTRONS
OXIDATION
POROSITY
RADIATION DOSES
REACTION KINETICS