The effect of chlorofluoromethanes on graphite oxidation

✍ Scribed by P.G. Pallmer

• Publisher: Elsevier Science
• Year: 1966
• Tongue: English
• Weight: 674 KB
• Volume: 4
• Category: Article
• ISSN: 0008-6223
• DOI: 10.1016/0008-6223(66)90075-3

✦ Synopsis

The effect of dichlorodifluoromethane, CClsFs and chlorotrifluoromethane, CClFs, on the air oxidation of nuclear graphite was studied by the continuous measurement of weight loss. One-half volume per cent CCl,Fs in air reduced the rate of oxidation of CSF and TSGBF nuclear graphites to about one-third the rate in air, whereas CCIF, had negligible effect. The slight effect of CCIFs is presumed to be related to its greater stability in a surface pyrolysis reaction The adsorption of chlorine in the pyrolysis reaction can reduce the active sites available for oxidation. Surface pitting was suppressed during inhibited oxidation and greater BET area was developed than during air oxidation.

It is proposed that some impurities react with CCl,Fs to become more effective oxidation catalysts. These impurities, especially vanadium, were present in significant amounts in EGCR graphite. Its oxidation behavior, as a result, showed a lower activation energy and higher rates as the impurities reacted with the halomethanes, unless or until the particular impurities were removed as volatile halides.

in correlating these results with the previous chlorine inhibition tests. Discussions with R. E. NIGHTINGALE which stimulated the development of the mechanisms suggested are gratefully acknowledged.