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Performance of CVD and CVR Coated Carbon-Carbon in High Temperature Hydrogen

Published online by Cambridge University Press:  22 February 2011

J. W. Adams ,
R. E. Barlettia ,
J. Svandrlik  and
P. E. Vanier
J. W. Adams
Affiliation:
Brookhaven National Laboratory, Upton, NY 11973
R. E. Barlettia
Affiliation:
Brookhaven National Laboratory, Upton, NY 11973
J. Svandrlik
Affiliation:
Brookhaven National Laboratory, Upton, NY 11973
P. E. Vanier
Affiliation:
Brookhaven National Laboratory, Upton, NY 11973
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Abstract

As a part of the component development process for the particle bed reactor (PBR), it is necessary to develop coatings which will be time and temperature stable at extremely high temperatures in flowing hydrogen. These coatings must protect the underlying carbon structure from attack by the hydrogen coolant. Degradation which causes small changes in the reactor component, e.g. hole diameter in the hot frit, can have a profound effect on operation. The ability of a component to withstand repeated temperature cycles is also a coating development issue. Coatings which crack or spall under these conditions would be unacceptable. While refractory carbides appear to be the coating material of choice for carbon substrates being used in PBR components, the method of applying these coatings can have a large effect on their performance. Two deposition processes for these refractory carbides, chemical vapor deposition (CVD) and chemical vapor reaction (CVR) have been evaluated.

Screening tests for these coatings consisted of testing of coated 2-D and 3-D weave carbon-carbon in flowing hot hydrogen at one atmosphere. Carbon loss from these samples was measured as a function of time. Exposure temperatures up to 3000 K were used and samples were exposed in a cyclical fashion, cooling to room temperature between exposures. The results of these measurements are presented along with an evaluation of the relative merits of CVR and CVD coatings for this application.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 327: Symposium N – Covalent Ceramics II: Non-Oxides , 1993 , 139
Copyright
Copyright © Materials Research Society 1994

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References

1. Barletta, R. E., Vanier, P. E., Adams, J. W. and Svandrlik, J. F., “Carbon Erosion in Hydrogen - The “Midband” Problem Revisited”, Tenth Symposium on Space Nuclear Power and Propulsion, El-Genk, M. S. and Hoover, M. D., eds., AIP Conference Proceedings 27,1, CONF930103, p 245,1993.Google Scholar
2. Vanier, P. E., Barletta, R. E., Svandrlik, J. F., and Adams, J. W., “Tests of Hercules/Ultramet CVD Coatings in Hot Hydrogen”, BNL Informal Report, BNL-47965, 1992.Google Scholar
3. Clarke, J. T. and Fox, B. R., “Reaction of graphite filaments with hydrogen above 2000 K,” J. Chem. Phys., 46, 827, 1967.Google Scholar