| 摘要 |
An alumina insulated filament wire for a thermionic valve cathode heater has an additional layer comprising an element of high oxygen-binding capacity, to prevent deterioration of the alumina. Suitable elements are zirconium, niobium, tantalum and titanium, and may be applied before or after the alumina. In a first example, zirconium hydride is deposited on a tungsten wire by cataphoresis from a suspension of Zr H2 in isopropylalchol and Ni Cl2 (0-2N). Alumina is then applied and sintered conventionally. In a second example the alumina is applied first and the hydride next, then both layers are sintered in a reducing atmosphere. In a final example alumina is applied to tungsten by cataphoresis, then a suspension of titanium and alumina in colladium is applied by spraying, followed by sintering of both layers. This produces a black filament. |
