Kovar seals

Certain alloys of iron, nickel, and cobalt (Kovar, Fernico, etc.) have thermal expansion curves which nearly match those of borosilicate glasses, and a good bond may be formed between the two. Kovar is similar to carbon steel in its chemical properties. For example, it oxidizes when heated in air and is not wet by mercury. It may be machined, welded, copper brazed, and soft soldered. Silver solders should not be used with Kovar since they may cause embrittlement. At low temperatures Kovar undergoes a phase transformation, and the change in expansion coefficient below this temperature may be sufficient to cause failure of a glass-to-Kovar seal. The transformation temperature usually is below... 

Oj SbjFn was prepared by irradiation of a fluorine, oxygen, and antimony pentaftuoride mixture contained in a Pyiex bulb provided with a Kel-F tipped Whitey valve joined to the bulb through a Kovar seal. A 450-W Hanovia ultraviolet Lamp was used at a distance of 6 in. irradiations lasted 12-16 hr. A stoichiometry appropriate for the reaction O, + VaF + 2SbFs OjSbjFi, was found to be best thus, 69.0 mmol of SbFj with 34.5 mmol of O, and 17.3 mmol of Fj in a 5-1. flask were quantitatively converted to 02Sb2Fii in 12 hr. In irradiations where an excess of F2 and... 

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