| 摘要 |
962,651. Electrode materials and processing. PATENT - TREUHAND - GES. FUR ELEKTRISCHE GLUHLAMPEN m.b.H. June 17, 1960 [July 8, 1959], No. 21357/60. Drawings to Specification. Heading H1. A cathode for a high-pressure discharge lamp is composed of a solid rod having a tapered tip portion and consisting of tungsten and a small addition, about 5% by weight, of thorium oxide, the rod comprising interlocking tungsten crystals elongated longitudinally throughout the rod, the length of the crystals being at least several mms. and the width of the crystals being at least several tenths of mms., and a plurality of thorium oxide particles minute compared with the tungsten crystals distributed uniformly throughout the whole volume of the rod and enclosed tightly within the tungsten crystals. The cathode is inserted into a body of sintered tungsten. The electrode can be manufactured by pressing a mixture of tungsten powder and a small amount of thorium oxide powder to slug form, sintering the slug to provide a coherent body, swaging the body to rod form to form elongated fine crystals, dividing the rod into portions, tapering one end of each rod portion and annealing the rod portions in a reducing atmosphere of hydrogennitrogen at 2800‹ C. up to complete re-crystallization and formation of coarse crystals. After the annealing step the rod portions can be swaged and annealed again. The mixture of tungsten and thorium oxide can be made by adding a thorium compound in dissolved form to tungstic acid and subjecting the mixture to a high temperature in a current of dry hydrogen. The electrode can be used in a lamp having an ellipsoidal or drop-shaped envelope filled with xenon. |
