Research on the electrophoresis method in the manufacture of oxide-coated cathodes

Experiments conducted on electrophoresis of BaSr(CO3)2 particles as used for oxide-coating are described and, based on the results obtained, the general subject and the mechanism of electrophoresis studied. It is pointed out that, to achieve stable electrophoresis in the case of particles of 1-10 mu size, lyophilic colloid must be added. This forms sheaths round the particles so that they behave as lyophilic particles. In addition, experiments are described where the density of coating, effect of moisture and temperature and electron discharge characteristic are varied. Furthermore, the mechanism of electrophoresis is explained on the basis of a double-, rather than a mono-molecular layer and also on the assumption of barrier potentials between the particles. The electrophoresis of Al2O3, as used for the heaters of indirectly heated cathodes, is also mentioned.