RESEARCH STUDIES ON THERMIONIC CONVERTERS, EMITTER SHELL PHASE
Rept. no. 5 (Final) for 1 Jul 1963-28 Feb 1965
RADIO CORP OF AMERICA LANCASTER PA ELECTRONIC COMPONENTS AND DEVICES
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The objective of the program was the development of a barrier shell to protect thermionic energy converters from the combustion products of a fossil fuel flame. Two material properties are of prime importance impermeability, and corrosion resistance. Three types of materials were selected for extensive testing alumina, beryllia and silicon carbide. Equipment of very high sensitivity 10 to the minus 12th power liter torrsq cm second was developed which permitted the determination of gas permeation rates. The identification of individual gases was made possible by the latest mass spectrometer equipment. It was determined that high purity alumina has the lowest permeation rate, the highest material strength, good thermal shock resistance and is resistant to corrosion. Beryllium oxide had a poor corrosion resistance and a high permeation rate for carbon monoxide. The pyrolytic silicon carbide samples obtained for this program evidenced high permeation rates for carbon monoxide and showed a tendency toward unpredictable fracture after extended periods at elevated temperatures.
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