Application of sputtered alumina coatings as insulating coatings for metallic MHD electrode and insulator modules

Journal Article · Tue Jan 01 00:00:00 EST 1991 · Magnetohydrodynamics; (United States)

OSTI ID:5027088

Vuoristo, P M.J.; Maentylae, T A; Kettunen, P O ^[1]

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1. Tampere Univ. of Technology, Inst. of Materials Science, P.O. Box 527, SF-33101 Tampere (FI)

The paper summarizes the results from tests in which alumina coated electrode and insulator wall modules were tested in actual MHD environments. Alumina coatings with a thickness of 5...10 {mu}m were prepared by rf diode and rf magnetron sputtering techniques. These methods yielded good quality coatings with a dense microstructure, good adhesion, and good electrical insulating properties. Both metallic cold electrodes and combined type metal/ceramic electrodes were used in the tests, which were carried out at a various pilot plant magnetohydrodynamic channels in the USSR. The test carried out at the SFTI facility showed that interelectrode resistance could be increased noticeably as compared to that of uncoated cold copper electrodes. Further, the interelectrode breakdown voltage was found to be higher by using alumina coatings as an additional insulating coating on copper electrodes. Combined type metal/ceramic electrodes with copper surfaces coated with dense sputtered alumina coatings were tested at the U-02 facility. At best, the alumina coating could prevent totally the conduction of electric current between the plasma and the coated electrode. Also no breakdown occurred when a voltage of 290 V was applied over the interelectrode gap. Rf diode sputtered alumina coatings showed somewhat better performance over rf magnetron sputtered alumina coatings. Long-time behavior was tested with insulator wall modules coated with a sputtered alumina layer at the U-25BM facility. The test proved that such a thin alumina coating can stay uneroded for several hundred hours and protect the copper ribs from oxidation.

• OSTI ID: 5027088
• Journal Information: Magnetohydrodynamics; (United States), Vol. 3:1; ISSN 0891-9801
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
ELECTRODES
COATINGS
METALS
MHD GENERATORS
ADHESION
ALUMINIUM OXIDES
BREAKDOWN
CERAMICS
ELECTRICAL INSULATORS
MAGNETRONS
MHD CHANNELS
MICROSTRUCTURE
PILOT PLANTS
RF SYSTEMS
SPUTTERING
TESTING
THICKNESS
USSR
ALUMINIUM COMPOUNDS
ASIA
CHALCOGENIDES
CRYSTAL STRUCTURE
DEVELOPED COUNTRIES
DIMENSIONS
DIRECT ENERGY CONVERTERS
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ELEMENTS
EQUIPMENT
EUROPE
FUNCTIONAL MODELS
MICROWAVE EQUIPMENT
MICROWAVE TUBES
OXIDES
OXYGEN COMPOUNDS
300103* - MHD Generators- Materials
Components
& Auxiliaries
300102 - MHD Generators- Performance & Testing