PTFE layers

Material Quartz glass, top and bottom stainless steel, impregnated with PTFE layer Quartz glass (both) glass... 

The use of LIF in fuel cells is less extensive than PIV, but has produced valuable results. Bazylak et al.101 used ex-situ testing to quantify the effects that cell compression have on GDL hydropho-bicity by damaging the GDL and PTFE layer. Lozano et al.102,103 and Barreras et al.5 conducted a series of LIF experiments on mock fuel cells with various flow field designs (diagonal, serpentine, and... 

Orbital energies of polysilanes are very sensitive to molecular conformation. Structured PDMS layers have been deposited by epitaxy on various substrates inducing various conformations via self-arrangement of the polymeric chains, either normal or parallel to the surface of the substrate, such as PTFE layers or freshly cleaved crystalline surfaces of KBr, NaCl, or KC1.5 Highly crystalline PDMS layers have been deposited on substrates and the UV absorption spectra are found to depend on the orientation of the crystal with respect to the substrate, as shown in Figure 6. 

FIGURE 6. Room temperature PL, EX, and ABS of (a) PDMS powder, (b) PDMS film evaporated on PTFE layer, and (c) on KBr cleaved surface. (Reprinted from Ref. 5.)... 

Cell reactor PTFE and Pd on an inorganic carrier H2 diffusion in liquid-filled pores Hydrogenation of /7-nitrobenzoic acid The PTFE layer on the gas side 26... 

Al Hot-pressed Pt black/PTFE layers B1 Ionomer - impregnated Pt/C//PTFE... 

Fig. 10. STM images of fcc(l 11) alloy surfaces. The bright atoms are Pt in PtCo and PtCu, but Fe in PtFe and Ni in PtNi. Compositions given are bulk compositions, except for PtFe, which is a surface alloy with =8 PtFe layers obtained by annealing a4 ML Fe film on Pt(111). The ordering of the PtFe alloy depends on the preparation frame (a) corresponds to an annealing tem-peramre of 470 °C, frame (b) to 530 C.

The authors gratefully acknowledge Prof. Faupel and coworkers for sputtering PTFE layers, the IPMS Fraunhofer Dresden for supplying the purified penta-cene and the DFG for financial support in the framework of the OFET-Schwerpunktprogramm for Contract No. Hi 551/7-3. 

Fig. 7.9 Alignment of discotic liquid crystals on PTFE layers. Columnar HBC stacks are lying edge-on and parallel with respect to the underlying PTFE chain. Reproduced with permission from [43]. Copyright 2007 American Chemical Society...

Fig. 2.5 Scanning electron micrograph of microporous membrane (a) hydrophilic surface layer (b) hydrophilic layer partly removed showing PTFE layer. ...

Fig. 3. Attenuated total reflection spectra of thin layers of CBOOA on PTFE-covered fused silica Wavelength is plotted on the x-axis, and reflection coefficient on the y-axis. Thg thickness of the PTFE layer is, from top to bottom 20A, lOX, 5A and oA. The individual traces in each of the figures are for liquid crystal thicknesses of 4.4 9 13 18 27 36 53 71 106 and 141A, respectively.

Our tentative interpretation is that the thin PTFE layers are patchy. Then, for liquid crystal layers thinner than the crossover thickness, the molecules on top of the patches will be perpendicular to the surface, while those between patches will be parallel. (We disregard here the case of very thin layers discussed above, when all molecules are parallel.) With increasing liquid crystal thickness, however, the elastic bend energy in the transition between the two orientations becomes gradually more important, and at some transition thickness a single orientation, parallel to the surface, may become energetically favored. Conceivably, a compromise inclined orientation could also be the results. 

SCHEME 3.14 Chemical structures of DLC compounds aligned on PTFE layers. 

Wittmann and Smith [15] reported that thin PTFE layer deposition is achieved by rubbing a bar of PTFE on a smooth siuTace and that this induces a well oriented chain axis of PTFE macromolecules. (See Fig. 3.6.1)... 

Fig. 3.6.1 Thin PTFE layer deposition on a smooth surface PTFE bar (a), substrate (b), aligned macromolecules of PTFE (c).

The thiekness of the MPL is eritieal to fuel cell performanee. Paganin et al. [52] showed that the performance of their thin-film eleetrodes inereased eonsiderably when the MPL thiekness was inereased from 15 to 50 pm, but when the thickness was further inereased the performanee dropped. Aeeording to these researehers, if the MPL is too thin, the cell total resistance increases for want of a sufficient carbon/PTFE layer to establish good electronie eontaet between the rough macroporous substrate and the eatalyst layer conversely, if the MPL is too thick, the diffusion distance and electrical resistance increase. 

PTFE) layer that would seal the hole in the vessel wall. The Wallgraft (Boston Scientific) has a woven Dacron graft material and although this is more porous, it will still effectively seal a hole and prevent further bleeding. 

Workers of the same group suggested using polytetrafluoroethylene (PTFE) in membranes of this type to raise the thermal resistance (Reichman et al., 2007). Nano-sized ceramic particules produced from tetraethyl orthosilicate [TEOS Si(OC2Hs)4] by sol-gel synthesis were introduced into a porous PTFE layer to give the material some degree of hydrophilicity and to secure a sufficiently... 

The great majority of current AFC systems use electrodes of the type shown in Figure 5.8, which have a PTFE layer over the gas side . PTFE is an insulator, and so it is difficult to make an electrical connection to the face of the electrode. The result is that the bipolar plate-type cell interconnect usually used in fuel cells, and shown in Figures 1.9 and 1.10, cannot normally be used in the AFC. This is also encouraged by the fact that the electrode is built onto a metal mesh, and so has a higher than normal conductivity across the plane, making edge connections less of a problem. 

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