Rare-earth hafnium oxide materials for magnetohydrodynamic (MHD) generator application
Several ceramic materials based on rare-earth hafnium oxides have been identified as potential high-temperature electrodes and low-temperature current leadouts for open cycle coal-fired MHD generator channels. The electrode-current leadouts combination must operate at temperatures between 400 and 2000K with an electrical conductivity greater than 10/sup -2/ ohm/sup -1/ cm/sup -1/. The electrodes will be exposed to flowing (linear flow rates up to 100 m/s) potassium seeded coal combustion gases (plasma core temperatures between 2400 to 3200/sup 0/K) and coal slag. During operation the electrodes must conduct direct electric current at densities near 1.5 amp/cm/sup 2/. Consequently, the electrodes must be resistant to electrochemical decompositions and interactions with both the coal slag and potassium salts (e.g., K/sub 2/SO/sub 4/, K/sub 2/CO/sub 3/). The current leadout materials are placed between the hot electrodes and the water-cooled copper structural members and must have electrical conductivities greater than 10/sup -2/ ohm/sup -1/ cm/sup -1/ between 1400 and 400/sup 0/K. The current leadouts must be thermally and electrochemically compatible with the electrode, copper, and potassium salts. Ideally, the electrodes and current leadouts should exhibit minimal ionic conductivity. The fabrication, electrical conductivity, and electrochemical corrosion of rare-earth hafnium oxide materials are discussed. (WHK)
- Research Organization:
- Battelle Pacific Northwest Labs., Richland, WA (USA)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- EY-76-C-06-1830
- OSTI ID:
- 5650464
- Report Number(s):
- PNL-SA-7522; CONF-790641-12
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
300103* -- MHD Generators-- Materials
Components
& Auxiliaries
36 MATERIALS SCIENCE
360201 -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
360205 -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
ALKALI METAL COMPOUNDS
CERAMICS
CHALCOGENIDES
CHEMICAL REACTIONS
COAL-FIRED MHD GENERATORS
CONDUCTOR DEVICES
CONNECTORS
CORROSION
CORROSION RESISTANCE
DATA
DIRECT ENERGY CONVERTERS
ELECTRIC CONDUCTIVITY
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CORROSION
ELECTRODES
EQUIPMENT
FABRICATION
HAFNIUM COMPOUNDS
HAFNIUM OXIDES
INFORMATION
MATERIALS
MHD GENERATORS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
RARE EARTH COMPOUNDS
SLAGS
TRANSITION ELEMENT COMPOUNDS
VERY HIGH TEMPERATURE