| 摘要 |
PURPOSE:To obtain a thermocouple which can be used at a high temperature of around 2,000 deg.C, by sealing a metallic wire constituted as a thermocouple in a boron nitride sintered body of high purity consisting of carbon and oxygen of a specified quantity, and tightly sealing it in a metallic pipe mainly consisting of iridium, together with gaseous nitrogen. CONSTITUTION:A metallic wire constituted as a thermocouple is sealed into a boron nitride sintered body of high purity consisting of carbon nd oxygen whose total is <=0.01wt%, and subsequently, it is tightly sealed in a metallic pipe mainly consisting of iridium, together with gaseous nitrogen of a very small quantity. As for a method for setting the total of carbon and oxygen to <=0.01wt% as to the boron nitride sintered body used in this invention, for instance, the boron nitride sintered body is heated to 2,000-2,200 deg.C in an atmosphere having nitrogen decomposition pressure exceeding the decomposition pressure of boron nitride containing no carbon nor oxygen. A thermocouple metallic wire 9 is sealed by making it pass through the inside of an obtained boron nitride sintered body 2. When this boron nitride sintered body is exposed without an airtight protecting film and is exposed in a high temperature atmosphere, it is contaminated quickly, its purity drops, electric conductivity increases, and such a state as an error of a temperature measurement cannot be disregarded occurs, therefore, it is covered with an alloy mainly consisting of iridium or an iridium metal 3, as an airtight protecting film. |
