Membrane content visualization

Confocal Raman Microscopy for Membrane Content Visualization... 

Another approach to differentiating between the anode and cathode water contents is to perform through-plane visualization. Until recently, neutron radiography was not able to achieve the resolutions necessary to sufficiently resolve a membrane thickness of 25 pm and GDL thicknesses of 200 pm. However, Hussey et al.38 developed a new detector technology based on micro-channel plates that allowed in-plane visualization with a resolution of 30 pm (10 pm is feasible with further detector development). An exposure time of 20 min was used and the possibility of increasing temporal... 

In this article, magnetic resonance imaging (MRI) technique is described as a diagnostic tool for in-situ visualization of water content in the membrane under fuel cell operation.7-30 Demonstrative applications and measurement procedure using MRI techniques are presented with discussion on water transport involved in PEMFCs. 

Figure 5 shows the MRI visualization of the transversal water content distribution in the membrane in an operational PEMFC with variation of the current density.29 The cell temperature and relative humidify were 70°C and 92%, respectively. The vertical width of the images is about 1.0 cm across the gas channels, which is in the central part of the GDL. The horizontal width of the images is 600 xm. The anode is on the left side of each figure. Figure 6 shows one-dimensional water content profiles in the membrane that were obtained from MRI visualization results at variation of the relative humidity and current density. The horizontal axis and vertical axis respectively indicate the through-plane position of the... 

The morphology of the water clusters and their connectivity can be better understood with a visual aid as shown in Fig. 5 and 6 where the snapshots of hydrated Nafion (Fig. 5) and SSC (Fig. 6) PFSA membrane are presented with the ionomer rendered invisible at ). = 4.4 and 9.6 respectively. The snapshots for both the membranes clearly indicate the presence of small clusters whose connectivity is poor at low water content and the clusters appears to have grown in size and more densely packed with better chWiel networks when the water content is increased. However, it is difficult, based solely on snapshots, to discern subtle differences in the size, shape and connectivity of the aqueous phase as a function of side chain length. In order to analyze these differences, we must invoke a more statistical characterization of the stmcture. 

Control of dirt and other particles involves use of a membrane filtration method (ASTM D-2276, IP 216) in which the dirt retained by filtration of a sample through a cellulose membrane is expressed as weight per unit volume of the fuel. This test provides field quality control of dirt content and can be supplemented by a visual assessment of membrane appearance after test against color standards (ASTM D-3830). However, no direct relationship exists between particulate content weight and membrane color, and field experience is required to assess the results by either method. 

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