| 摘要 |
PURPOSE: To suppress oxidation degradation and keep a satisfactory performance for a long period under high temperature and oxidizing environments by providing a protecting film on the surface of a metal filament at a temperature higher than the highest operating temperature. CONSTITUTION: A filament 18 formed of a heat resisting metal such as tungsten is extended across a plate 16, and welded to a pin 20 fixed to the plate 16. Prior to the integration of the filament 18 into a heat conductivity detector, the surface is covered with a protecting film such as oxy nitride, DOP oxide, or the like. The plate 16 is placed in an air circulating furnace having a temperature higher than the highest operating temperature of a detector to be used by at least about 50 deg.C, or about 500 deg.C or more for about 7 hours to form a film having a thickness of about 500-5000Åis formed on the surface of the filament 18 by chemical evaporation. The detector using the thus-formed filament 18 can be significantly extended in durable life under an operating temperature of about 450 deg.C.
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