NERVA fuel element development program, July 1966--June 1972. Characterization of vapor-deposited niobium and zirconium carbides
- Oak Ridge Gaseous Diffusion Plant (K-25), Oak Ridge, TN (United States)
Chemical and physical properties of vapor-deposited niobium carbide and zirconium carbide have been determined by the fabrication of thick-wall tubes of each carbide under varying deposition conditions. The effects studied included coefficient of thermal expansion, density, impurity level, carbon-to-metal ratio, and metallographic structure. The niobium carbide coatings contained less than 3,000 parts per million impurities, and the impurity level decreased when the deposition temperature was increased. Some of the zirconium carbide coatings contained four percent oxygen and chlorine, and the impure coatings were unstable when heated above the deposition temperature of 1,100°C. The amount of instability was primarily related to the oxygen and chlorine content; an increased deposition temperature reduced the impurity contents to less than 500 ppm. The higher-temperature process conditions produced coatings with a predictable and consistent coefficient of thermal expansion value which could be repeatedly heated to 2,000°C (~ 700°C above the deposition temperature) without any detrimental effects such as weight and volume changes. The weight and volume changes were related to the impurities being evolved when the coatings were heated to temperatures of 1,600 to 1,800°C.
- Research Organization:
- Oak Ridge Gaseous Diffusion Plant (K-25), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Atomic Energy Commission (AEC)
- DOE Contract Number:
- W-7405-eng-26
- OSTI ID:
- 1313858
- Report Number(s):
- Y-1852 (Pt.3); TRN: US1601828
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
VAPOR DEPOSITED COATINGS
ZIRCONIUM CARBIDES
NIOBIUM CARBIDES
CHLORINE
OXYGEN
DEPOSITION
IMPURITIES
THERMAL EXPANSION
TEMPERATURE RANGE 1000-4000 K
CARBON
FUEL ELEMENTS
WEIGHT
VOLUME
DENSITY
INSTABILITY
METALLOGRAPHY
TUBES
TEMPERATURE DEPENDENCE
NERVA REACTOR