- Conference date: 7−11 Jan 1996
- Location: Albuquerque, New Mexico (USA)
A thin layer of plasma‐sprayed alumina is used in single cell thermionic fuel elements to provide electrical insulation of the outer surface of the collector from ground. Under normal operating conditions this material is not exposed to cesium vapor. However under abnormal conditions, such as the leaking of a TFE seal, the plasma‐sprayed insulator surface may be expected to come into contact with cesium. The porous nature of these materials raises the concern that the metal vapor may penetrate beyond the surface and degrade the bulk electrical resistance properties. In this paper we describe experiments to determine the effect of cesium vapor on the bulk electrical conductivity of two different plasma‐sprayed insulators: alumina and magnesium aluminate spinel. The results clearly demonstrate that cesium is easily able to penetrate beyond the surface and into the bulk of these materials and does indeed cause a dramatic increase in the bulk electrical conductivity. This effect may be a potential degradation mechanism for thermionic reactor systems operated over an extended period.
- Insulator surfaces
- Electrical conductivity
- Surface conductivity
- Bulk materials
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