| 摘要 |
828,189. Cathode materials and processing. PHILIPS ELECTRICAL INDUSTRIES Ltd. Jan. 23, 1958 [Jan. 26, 1957], No. 2317/58. Class 39(1). In a dispenser cathode containing an emissive mix ture of barium aluminate and powdered tungsten stored in a supply chamber behind a wall of porous tungsten, the cathode is heated after closure of the supply chamber to 1900‹K-2200‹K in a hydro gen atmosphere for about a minute, after which it is rapidly cooled. The aluminate is made from barium and aluminium oxides, with possibly calcium oxide in addition. After adding the tungsten powder, the mixture is pressed into tablets and fired. As shown in the Fig. the tablets 7 are placed in molybdenum containers 4, and the porous closure members 6 welded in position. The cathodes are then placed in a crucible 3, which is heated by induction inside a quartz tube through which hydrogen is passed. In the vertical position shown, absorption of the aluminate into the porous member by direct contact is avoided. In Fig. 2 (not shown), the same process is applied to a cylindrical cathode, the heating in this case being by passage of a current. The process of the invention is stated to reduce both the activation time, and the evaporation of barium. |
