SPINELS FOR MHD-ELECTRODES.

A number of high temperature spinels appear to hold promise as building blocks for MHD-electrodes. Above 1200 K (and in some cases even 900 K) the electrical conduction in iron-doped Mg-chromite and Mg-aluminate spinels is sufficiently high to carry the current generated in MHD-channels. Fe-Co-spinel seems to have all the properties desired for a good lead-out material. Mg-Al-Fe spinel is recommended for use with clean fuels, because its reactivity with potassium apparently is very small. On the other hand the chromite spinel has shown good corrosion resistance in a slagging environment. A slag layer on top of a chromite electrode would absorb much of the seed, hence lower the potassium activity and thus diminish the possibility of strong K//2O-Cr//2O//3 reactions.