High-temperature thermionics
This dissertation is divided into three sections: (1) A complete high-temperature tensile station has been set up for studying the mechanical properties of thermionic electrode materials. The mechanical properties of W,30Re and W,30Re,1ThO{sub 2} were evaluated at elevated temperatures. It was found that the dispersed second phase (1 w/o ThO{sub 2}) improved the strength and ductility of W,30Re alloy. Great alloy strength results when thoria particles impede the grain-boundary sliding. (2) Thermionic emission microscope and vacuum emission station have been used previously for effective work functions and normal spectral emissivity measurements. The present study evaluates W,Re,0.35HfC alloys with various rhenium contents in the temperature range of 1700 K to 2500 K. The results indicated that the normal spectral emissivity at {lambda} = 0.65 {mu}m or {lambda} = 0.535 {mu}m decreased with increasing temperature and rhenium content. The presence of hafnium carbide exhibited higher normal spectral emissivity that sintered materials with a comparable alloy content. The results also indicated that the effective work function increased with increasing temperature and rhenium content. The increase in effective work function with rhenium content can be explained by the increase in the potential barrier at the metal-vacuum boundary, associated with the volume effect-decrease in the lattice constant. Coversely adding HfC lowers the effective work function at temperatures below 2100 K. (3) The use of a cesium cell as a heat-to-electric energy converter has been described extensively in the literature. The goal was to begin TEC studies in existing diodes with the emitter electrodes of W(110) and Re(0001) and determine the optimum performance.
- Research Organization:
- Arizona State Univ., Tempe, AZ (USA)
- OSTI ID:
- 5951957
- Country of Publication:
- United States
- Language:
- English
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CARBON COMPOUNDS
CHALCOGENIDES
DIRECT ENERGY CONVERTERS
DUCTILITY
ELECTRODES
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OXYGEN COMPOUNDS
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TENSILE PROPERTIES
THERMIONIC CONVERTERS
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