Sealing compressive seals

The various options for sealing and joining the ceramic and metal components in pSOFCs can be broadly classified into one of three categories rigid bonded seals, compressive seals, and bonded compliant seals. As outiined in Table 11.2, rigid... 

A hermetic seal is achieved by pressing the seal material between the surfaces to be sealed. The seal material must be elastic over the operating temperature range, and sufficiently soft to fill the micro-roughness on the surfaces to be sealed. Compressive seals offer several advantages (29) ... 

An indatable diaphragm or membrane has been used in membrane plate presses closely related to the conventional plate and frame presses. A pressure filtration period is foUowed by compression with the hydraulically operated membrane or by a hydraulically operated ram if dexible rim seals are fitted. This principle also is used in vertical presses that use either one or two endless cloth belts indexing between plates. Indatable membrane also may be used on a cylindrical filtration surface with or without a preceding pressure filtration stage. 

As a tme thermoplastic, FEP copolymer can be melt-processed by extmsion and compression, injection, and blow molding. Films can be heat-bonded and sealed, vacuum-formed, and laminated to various substrates. Chemical inertness and corrosion resistance make FEP highly suitable for chemical services its dielectric and insulating properties favor it for electrical and electronic service and its low frictional properties, mechanical toughness, thermal stabiUty, and nonstick quaUty make it highly suitable for bearings and seals, high temperature components, and nonstick surfaces. 

Cell Assembly. The methods for cell assembly, starting with the processed plaques depend on whether the cells are to be vented or sealed. For vented cells, processed plaques are usually compressed to 85 —90% of their processed thickness allowing sufficient porosity for electrolyte retention and strengthening the plate stmcture. For sealed cells, sizing of the negative plaques is usually avoided because maximum surface area is important to oxygen recombination. 

Compression Set Resistant. One property of fluorocarbon elastomers that makes them uniquely valuable to the sealing industry is their extreme resistance to compression set. Figure 4 plots compression set vs time for compounds prepared especially for compression set resistance (O-ring grades). 

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