Dense crack-free membranes

The electrolyte membrane should be dense, crack-free, and gas-tight. The ionic conductivity of the electrolyte should be in the range of 10 S/cm, with small electronic conduction. The electrolyte membrane must be chemically stable under both anode and cathode atmospheres. 

In the discussions to follow two types of membranes must be distinguished (1) nonsupported and (2) supported ones. Nonsupported membranes are produced by pouring a slip onto a very smooth, dense substrate on which gelling takes place by slow evaporation of the dispersion liquid. In this way rather thick, crack-free films can be obtained. They are especially suitable for characterization purposes and structural investigations. These are evaluated to determine whether or not the structures obtained are similar or comparable with those of the supported ones, made from the same slip and the same material. The next section will also focus on the supported membranes. 

Fig. 10.11 Illustration of the possible scale phenomena as they pertain to membrane transport (a) Cross section of a corrosion free membrane, (b) membrane with porous corrosion scale, (c) membrane with cracked corrosion scale, (d) membrane with spalling corrosion scale, (e) membrane with continuous, dense corrosion scale...

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