Optimization microstructure

In this chapter the technological development in cathode materials, particularly the advances being made in the material s composition, fabrication, microstructure optimization, electrocatalytic activity, and stability of perovskite-based cathodes will be reviewed. The emphasis will be on the defect structure, conductivity, thermal expansion coefficient, and electrocatalytic activity of the extensively studied man-ganite-, cobaltite-, and ferrite-based perovskites. Alterative mixed ionic and electronic conducting perovskite-related oxides are discussed in relation to their potential application as cathodes for ITSOFCs. The interfacial reaction and compatibility of the perovskite-based cathode materials with electrolyte and metallic interconnect is also examined. Finally the degradation and performance stability of cathodes under SOFC operating conditions are described. 

Behrens M, Furche A, Kasatkin I, Trunschke A, Busser W, Muhler M, Kniep B, Fischer R, Schlogl R. The potential of microstructural optimization in metal/oxide catalysts Higher intrinsic activity of copper by partial embedding of copper nanoparticles. ChemCatChem. 2010 2(7) 816-818. 

Lai ZP, Bonilla G, Diaz I, Nery JG, Sujaoti K, Amat MA, Kokkoli E, Terasaki O, Thompson RW, Tsapatsis M, and Vlachos DG. Microstructural optimization of a zeolite membrane for organic vapor separation. Science 2003 300 456-460. 

J. T. Drake, R. L. Williamson and B. H. Rabin, "Finite Element Analysis of Thermal Residual Stresses at Graded Ceramic-Metal Interfaces, Part II Microstructure Optimization for Residual Stress Reduction," J. Appl. Phys., 74 [2] 1321-1326 (1993). 

A further improvement of both hot-pressing cycles and additives, in particular concerning the transition metal diborides resulted in a microstructural optimization with in-situ grown W2B5 particles. After annealing, the average of the diameter of the W2B5 particles was about 4.5-7 pm (Fig. 59). 

Depending on the current density a rather non uniform utilization of the catalyst layer can be expected. While at low current density negligible effects are caused by the ionic resistance in the catalyst layer and almost all platinum particles can be used, the reaction concentrates close to the membrane interface at high current densities causing underutilization of the platinum present in the electrode [54, 55]. Optimization of electrode performance can be expected from microstructural optimization for example by designing catalyst layers having gradients in noble metal concentration and porosity. 

The importance of microstructural optimization of hydrophobic gas diffusion electrodes was emphasized in an article by Tantram and Tseung (1969). Tantram and Tseung considered porous electrodes that consisted of mixtures of finely dispersed Pt black particles, bonded by polytetrafluoroethylene (PTFE). Hydrophobic and hydrophilic parts formed interconnected networks of porous PTFE and porous catalyst aggregates. The two authors recognized the importance of agglomeration and dual hydrophobic/hydrophilic porosity. 

Within the requirements of the economic life of the product, adequate control of heat treating and metal working processes is required to develop microstructure optimally resistant to a specific environment. 

Microstructural Optimization of Thin Supported Inorganic Membranes for Gas and Water Purification... 

MICROSTRUCTURAL OPTIMIZATION OF THIN SUPPORTED INORGANIC MEMBRANES... 

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