MIEC structure

To develop an alternative MIEC cathode not only the ex situ properties, e.g., cr, TEC, /), and k, but also the electrocatalytic activity, structural and chemical stability, and Cr-tolerance must be considered. Beyond testing in small SOFC button cells, the viability of new cathode materials must ultimately be proven in large-scale stack cells under practical current and temperature gradients. The issues involved in the development of cathode materials for large-scale stacks are significantly more complex than those in the small button cells briefly reviewed in this chapter. However, this does provide serious challenges as well as opportunities for materials scientists and engineers in the development of commercially viable ITSOFCs. 

Oxides exhibiting only high ion conductivity are mainly fluorite-related structures based on zirconia or ceria. Zirconia-based electrolytes are currently used in solid oxide fuel cells (SOFCs). The MIEC oxides are more attractive for separative membrane applications, and these oxides mainly belong to the following types fluorite-related oxides doped to improve their electron conduction, - ... 

Figure 18.4 MIEC hollow fiber membranes with (A) sandwiched structure (B) symmetric structure and (C) highly asymmetric structure prepared using different spinning conditions.

Our interest is to develop MIEC block copolymers with microphase separated structures such that the electronic and ionic phases are in intimate contact at the few hundred angstrom level. We believe that such intimate contact between the two phases will result in functional polymers capable of very fast responses, e.g., in sensors and MEMS devices. A synthetic muscle functions by converting chemical energy into mechanical energy [5]. A biopolymer strip capable of carrying out this function consists of a polyethylene layer, a thin gold layer, and a polypyrrole layer immersed in an electrolyte solution. Oxidation of the polypyrrole results in... 

The work carried out in our laboratory has led to the development of synthetic methods required for the preparation of MIEC block copolymers. It will now be necessary to obtain a clear understanding of the structure-microstructure-function interrelationship of the MIEC block copolymers. MIEC block copolymers of controlled structures may be ideal for testing the different hypotheses of coupling between the electronic and the ionic species in mixed conductors [56]. Methods are available to determine the diffusion constants of the ionic species in mixed conducting systems [65]. The diffusion constants of ionic species in mixed con-... 

Mixed ionic and electronic conductors (MIECs) are an important class of materials that include oxides of different structures such as perovskites, brownmillerites, and fluorites. They can potentially be employed in high-temperature applications for which simultaneous reaction and separation is advantageous [29,30]. These... 

In addition, gas transport in both the support structures and the electrodes, and variations in gas composition in the fuel flow direction should also be taken into account when modeling full cells. The above represent the typical equations used for calculating the current densities through an MIEC electrolyte. Oxygen activity through an electrolyte at steady state can be calculated from charge conservation V= 0, where/onk and Teiec are the ionic and electronic fluxes, respectively. For the ID case, conservation of charge translates into = 0. 

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