Chemical vapor deposition of silicon carbide from methylsilane and coating of nuclear waste ceramics
This research evaluated the chemical vapor deposition (CVD) of silicon carbide from methylsilane (CH/sub 3/SiH/sub 3/) and coating of nuclear waste ceramics. The phase equilibria of the SiC coatings were investigated and compared with thermodynamic equilibrium calculations. The major variables studied were coating temperature, hydrogen content of the diluent gaseous system (Ar - H/sub 2/) or (N/sub 2/ - H/sub 2/), and addition of C/sub 2/H/sub 2/ to the system. Pyrocarbon coated alumina, and nuclear waste ceramic substrate particle were coated with silicon carbide in a fluidized-bed coater. The thermodynamic calculation results on the CH/sub 3/SiH/sub 3/ - Ar system indicate that SiC + Si are codeposited up to approx. = 1450 K. Single phase SiC is computed to form above that temperature. The silicon content of the condensed phase increases as the temperature decreases or the hydrogen content in the diluent gas increases. The coated particle concept for solidification of high-radiation-level nuclear waste was also evaluated. Sol-gel derived substrates of high-waste loading, and Cs-loaded zeolite were coated with SiC and pyrolytic carbon in a fluidized-bed coater. Leach testing by standard techniques showed them to be highly leach resistant and possess leach rates lower than other nuclear waste forms.
- Research Organization:
- Tennessee Univ., Knoxville (USA)
- OSTI ID:
- 6960689
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
36 MATERIALS SCIENCE
360602 -- Other Materials-- Structure & Phase Studies
ALKALI METAL COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CERAMICS
CESIUM COMPOUNDS
CHEMICAL COATING
CHEMICAL VAPOR DEPOSITION
COATINGS
DATA
DEPOSITION
ELEMENTS
EQUILIBRIUM
EXPERIMENTAL DATA
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MANAGEMENT
MATERIALS
MINERALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
PHASE STUDIES
PROCESSING
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE PROCESSING
RADIOACTIVE WASTES
SILANES
SILICON CARBIDES
SILICON COMPOUNDS
SURFACE COATING
TEMPERATURE DEPENDENCE
THERMODYNAMICS
VAPOR DEPOSITED COATINGS
WASTE MANAGEMENT
WASTE PROCESSING
WASTES
ZEOLITES