Ceramic method sealed tube

This is the most common test method employed to qualify the leak characteristics of a new seal material. The test method involves applying the seal between two ceramic discs or between a ceramic and a metal disc, pressurizing the cavity formed by the seal and monitoring the pressure decay as a function of time.22 Alternatively, a metal tube and a ceramic disc can also be used [34], Typically, the cavity is pressurized to about 2 psi and the leak rate is determined by the pressure decay as a function of time. These tests can be done at room temperature or elevated temperatures. Similar test arrangement has also been used to test a plastically deformable brazed metal seal between fuel cell anode material and Haynes 214 washer [35], The cavity is pressurized to measure the rupture strength of the seal material. 

In spite of such limitations, ceramic techniques have been widely used for the synthesis of solid materials. Mention must be made, among others, of the use of this technique for the synthesis of rare earth mono-chalcogenides such as SmS and SmSe. The method involves heating the elements, first at lower temperatures (870-1170 K) in evacuated silica tubes the contents are then homogenized, sealed in tantalum tubes and heated to around 2300 K by passing a high current through the tube [15]. 

Fig. 1 also shows that the emitter and the collector are connected by several units. To reduce the heat conduction loss, Ta tubes called heat-chokes are joined to the both electrodes. Ceramic seal rings are used to insulate the electrodes electrically. Two rings are arranged for Cs vapor tube inlet and electrical leads. Each unit is connected by a electron beam welding or a vacuum brazing method. 

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