| 摘要 |
PURPOSE:To prevent a heater from being broken due to abrasion by acid- treating the heater after alumina sintering. CONSTITUTION:A W-wire is formed into a double-spiral structure. Next, the surface of the formed W-wire 11 is coated with alumina 12, and further dark alumina 13 is dip-coated. Alumina 12, 13 is sintered in the hydrogen atmosphere. Next, a heater is treated with strong acid after alumina sintering. Thereby, impurities deposited on the alumina surface at the time of alumina sintering are dissolved in the strong acid. Since the operating temperature of the heater is lower than the alumina sintered temperature, pollution of the W-wire due to impurities in the alumina can be reduced to the level practically offering no problem. In addition, the acid passes the alumina and reaches the surface of the W-wire 11, an oxidized W-wire layer and trace W on the surface of the W-wire 11 are dissolved and the W-wire is made thin, and as a result the tensile force from the alumina 12, 13 to the W-wire 11 is reduced after an alumina crack is generated. Accordingly, heater disconnection can be prevented.
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