Mica-based seals

Mica-based materials are used as an alternative to metallic gaskets. Micas are composed of sheets of silica tetrahedrons and belong to the class of layer mineral phyllosilicates. The most commonly investigated mica for SOFC applications are 

All these mica materials exhibit a uniform dielectric constant along with high resistivity. Usually, primary leak paths in compressed mica seals are the interfaces between mica sealants and the ceramic/metal component. Hgure 5.6a shows the gas-light seal formed by mica crystals and the predominant leakage routes. To improve the performance of mica seals, mica powder can be placed inside the gaps in corrugated metal seals O ig. 5.6b). 

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Y.S. Chou and J.W. Stevenson, Thermal cycling and degradation mechanisms of compressive mica-based seals for solid oxide fnel cells. Journal of Power Sources, 112 (2002) 376-383. 

Table 11.5 Sealing properties of selected mica-based seals.

Prediction of H2 leak rate in mica-based seals of planar solid oxide fuel cells. J. Power Sources, 182, 141-144. 

Chou, Y.S. and Stevenson, J.W. (2003), Phlogopite mica-based compressive seals for SOFCs effect of mica thickness, J. Power Sources, 124, 413-lS... 

Octal base plug Supports Mica shields Graded seal... 

Drilling fluids - Coarse, hammermilled (+10 mesh) mica is used in water-based oilwell drilling fluids to prevent fluid loss into porous rock formations. The coarse mica flakes bridge openings and seal porous sections of the drill hole against loss of circulation. Mica s platy nature also aids in the suspension of drilling fluid solids and cuttings. 

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