| 摘要 |
PROBLEM TO BE SOLVED: To improve the strength of a high m.p. glass tube used for a discharge tube by dipping a glass tube in a solution of a cesium compound having a m.p. of equal to or below a temp. giving no effect on the glass tube and heating. SOLUTION: Such as a borosilicate glass tube 1 suitable for sealing or joining a high m.p. metal is charged in a metal or ceramic made vessel 2 durable enough against a long term use at a high tamp. of about >=500 deg.C. The powder or the like of cesium nitrate 3 having 414 deg.C m.p. is charged in the vessel 2 to cover the glass tube 1. Next, the vessel 2 is charged to a high temp. furnace 4. The temp. of the inside of the furnace 4 is increased up to a temp. of about 420-450 deg.C, at which cesium nitrate is completely melted and the glass tube is not affected. The glass tube 1 is heat treated by keeping the melting temp. constant for several hours. Then, the temp. of the high tamp. furnace 4 is lowered, the vessel 2 is taken out from the high temp. furnace 4 and further the glass tube 1 is taken out to complete the tempered glass tube.
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