process for the manufacture of indirectly heated cathodes.

摘要

1,090,935. Thermionic cathode constructions. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Feb. 25, 1966 [March 2, 1965], No. 8403/66. Heading H1D. In a method of making an indirectly heated cathode which has the space between the filament wire 2 and the support 1 for the emissive layer 5 filled out with a porous, insulating, ceramic mass, a ceramic suspension containing gas developing constituents is applied as a thin coating to the filament wire 2 and/or the inner surface of the cathode support 1, the filament is then inserted inside the support and the ceramic suspension caused to foam and expand to fill the intervening space, after which the foam 4 is sintered and degassed. In an example, the suspension was composed of 15 gm. of aluminium powder, 100 gm. of silica (av. particle size 20Á), 650 gm. of aluminium metaphosphate, 100 gm. of bentonite, 3000 gm. of aluminium hydroxide which were mixed together in the dry state and then suspended in 3100 gm. of orthophosphoric acid. The foam was heated in air at 150‹ C. for two hours before being sintered and degassed. The emissive layer may be barium-strontium carbonate.