Durability impurity effect

Determine fuel and fuel impurity effects on fuel processor catalyst durability... 

Portland cement powder contains live major constituents. These are complex minerals and are known by their chemical names, mineral names and by a shorthand notation, listed in Table 6.6. There are also traces of other impurities in ordinary cement powder, which may have a large effect on the final strength and durability of the concrete. The composition of typical Portland cement is included in Table 6.6. 

The environment in which an article is used may influence bond durability (see also Durability fundamentals). Atmospheric ozone can cause time-dependent crack growth in vulcanized elastomers in addition, ozone can induce failure at a bond with certain bonding agents. Although water is only slightly soluble, it can permeate elastomers by an osmotic mechanism induced by salt-Uke impurities. As a result, the uptake in salt water is generally less than that in pure water. Rubber to metal bond failure has been found to occur in a time-dependent manner under salt water in the presence of electrochemical activity but much more slowly, if at all, in its absence (see also Cathodic disbondment). In the absence of imposed electrochemical activity, effects are likely to depend particularly on the metal used and its corrosion resistance. Provision of a bonded rubber cover layer over all metal surfaces subject to immersion is likely to enhance bond durability. 

Figure 6.8. Polarization curve showing the effects of NO2. Cell temperature 70 °C, Stoich 1.2/2, ambient pressure, RH 100% for both air and fuel side [35]. (Reprinted from Journal of Power Sources, 138(1-2), Mohtadi R, Lee W-K, Van Zee JW, Assessing durability of cathodes exposed to common air impurities, 216-25, 2004, with permission from Elsevier.)...

Goodwin, J.G.J., Zhang, J., HongsMkam, K., Liu, Z., Rhodes, W., Colon-Mercado, H., Greenway, S. 2007. Effects of impurities on fuel cell performance and durability. Oral presentation, Washington, D.C. 

Flooding also has a negative effect on PEMFC durability. Too much water accelerates corrosion of the electrodes, the catalyst layers, the gas diffusion media, and the membrane (Pierre, 2000). Corrosion in turn increases ohmic losses. Dissolved catalyst particles and impurities can also be transported into the membrane, replacing H+ ions and reducing the proton conductivity over time, eventually leading to cell failure (Ge, 2007). 

Du, B., R, Pollard, and J.F. Elter. 2009. Performance and durability of a polymer electrolyte fuel cell operating with reformatted Effects of CO, COj, and other trace impurities. In Polymer electrolyte fuel cell durability, eds. F.N. Buchi, M. Inaba and T.J. Schmidt, pp. 341-366. New York, NY Springer. 

---