Dense ceramic membranes categories

The ceramic-to-metal seals for dense ceramic syngas membranes that have been suggested or demonstrated fall into one of three categories ... 

Dense membranes are those in which the pores of the membrane material do not cross from one side of the membrane to the other. As shown in Table 27.1, two categories of dense membranes are employed for catalytic oxidations ceramic membranes and metallic membranes. 

Dense (nonporous) membranes can be subdivided into (1) ceranuc membranes, (2) metal membranes, and (3) liqmd-immobilized membranes. These include materials which allow preferential passage of hydrogen or oxygen, in the form of either ions or atoms. With regard to the third category, these membranes consist of a porous support in which a semipermeable liquid is immobilized which fills the pores completely. Interesting examples are molten salts immobilized in porous steel or ceramic supports, semipermeable for oxygen or ammotua. ... 

The last category of inorganic membranes used for gas separation is constituted of dense materials including metals and ceramics [127]. 

One category of dense proton conducting membranes that has received considerable attention in the preceding decade is proton conducting perovskite type oxide ceramics [4-6]. The stoichiometric chemical composition of perovskites is represented as ABO3, where A is a divalent ion (A +) such as calcium, magnesium, barium or strontium and B is a tetravalent ion (B +) such as cerium or zirconium. Although simple perovskites such as barium cerate (BaCeOs) and strontium cerate... 

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