Conductivity profiles

T.M. Habashy, W.C. Chew, and E.Y. Chow, Simultaneous reconstruction of permittivity and conductivity profiles in a radially inhomogeneous slab, Radio Sci., 1986,21,... 

Fig. 8. Model of the conductivity profile in an anodic oxide film on tantalum after heat treatment, where Tj < r, < T,.

Vinyl acetate is a colorless, flammable Hquid having an initially pleasant odor which quickly becomes sharp and irritating. Table 1 Hsts the physical properties of the monomer. Information on properties, safety, and handling of vinyl acetate has been pubUshed (5—9). The vapor pressure, heat of vaporization, vapor heat capacity, Hquid heat capacity, Hquid density, vapor viscosity, Hquid viscosity, surface tension, vapor thermal conductivity, and Hquid thermal conductivity profile over temperature ranges have also been pubHshed (10). Table 2 (11) Hsts the solubiHty information for vinyl acetate. Unlike monomers such as styrene, vinyl acetate has a significant level of solubiHty in water which contributes to unique polymerization behavior. Vinyl acetate forms azeotropic mixtures (Table 3) (12). 

Fig. 8 Temperature, dissolved oxygen saturation, and conductivity profiles in the Sau and Susqueda reservoirs during a water transfer in 2005. Gray banners indicate the depth of the spillways (actual withdrawal depth indicated as an arrow). The path of the Sau Reservoir water inside Susqueda is indicated as a black thick arrow...

Fig. 10 Temperature, dissolved oxygen saturation, and conductivity profiles recorded in reservoirs from the Llobregat basin during the summer of 2005. Despite 6 months of stratification, oxygen saturation still showed high values except in La Baells. Compare these profiles with those from the Ter River reservoirs in Fig. 8...

Sowada and Warman (1982) have described a dc conductivity method for Ar gas at 295 K and 45 atm. Following a 20-ns pulse of irradiation, the conductivity rises to a peak at -50 ns, due to the Ramsauer effect, before settling to a plateau, which is ascribed to thermal conductivity since the collecting field is very low. Since there is little electron loss, the conductivity profile is proportional to the mobility profile this in turn can be considered a kind of image of collision frequency as a function of electron energy. The time to reach the conductivity plateau, -150 ns, is the measure of thermalization time in the present case. At a density of -9 X 1021 cm-3, the conductivity maximum vanishes, indicating the disappearance of the Ramsauer minimum according to Sowada and Warman. 

The microstructure of a catalyst layer is mainly determined by its composition and the fabrication method. Many attempts have been made to optimize pore size, pore distribution, and pore structure for better mass transport. Liu and Wang [141] found that a CL structure with a higher porosity near the GDL was beneficial for O2 transport and water removal. A CL with a stepwise porosity distribution, a higher porosity near the GDL, and a lower porosity near the membrane could perform better than one with a uniform porosity distribution. This pore structure led to better O2 distribution in the GL and extended the reaction zone toward the GDL side. The position of macropores also played an important role in proton conduction and oxygen transport within the CL, due to favorable proton and oxygen concentration conduction profiles. 

Conductivity Profiles in SrTiC>3 Single Crystals after High Field Stress... 

Before a large dc field was applied to a single crystal, a homogeneous conductivity could be detected [273]. After a high field stress (103 V cm-1 for 90 minutes), however, a distinct conductivity profile has developed in the sample (Fig. 33a). It consists of four characteristic regions i) an enhanced conductivity region at the anode with a relatively smooth drop towards the center of the sample ii) a sharp... 

Fig. 33. (a) Conductivity profile in a Fe-doped SrTiC>3 single crystal obtained at 417 K after electrocoloration with Au electrodes (E = 103 V cm-1 at 493 K for 90 min), (b) Profile after subsequent annealing at about 613 K for two hours profiling temperature 417 K. 

Fig. 35. Detail of the conductivity profile measured close to the anode of an electrocolored Fe-doped SrTiCb polycrystal (E = 103 V cm1, electrocoloration with Au electrodes at about 493 K for 60 min). The corresponding area of the sample with evaporated microelectrodes (dmt = 10 pm) is depicted below the diagram. The dotted lines indicate grain boundaries the arrow, the investigated electrode line. The profile was measured at 473 K.

The applicability of microelectrodes in various fields of solid state ionics has been demonstrated in four examples i) Local conductivity measurements on SrTiC>3 revealed pronounced conductivity profiles after high-field stress and confirmed that non-stoichiometry effects due to blocked ion exchange at the electrodes cause the phenomenon of resistance degradation in perovskite-type electroceramics, ii) Micro-... 

Guo Q, Cayetano M, Tsou Y, De-Castro ES, White RE (2003) Study of ionic conductivity profiles of the air cathode of a PEMFC by AC impedance spectroscopy. J Electrochem Soc 150(ll) A1440-9... 

It is known that the catalyst layer is far from uniform, especially in the case of a gradient catalyst layer. Thus, profiling properties, such as conductivity, in the catalyst layer are important. Both an electronic conductor (carbon) and an ionic conductor (Nafion ) exist in the catalyst layer, which can be considered a conductive polymer. The conductive polymer electric circuit model has been applied to the catalyst layer, and an ionic conductivity profile was obtained [8], as shown in Figure 4.33. 

Lefebvre MC, Martin RB, Pickup PG (1999) Characterization of ionic conductivity profiles within proton exchange membrane fuel cell gas diffusion electrodes by impedance spectroscopy. Electrochem Solid-State Lett 2 259-61... 

Figure 6.28. Conductivity profiles used to simulate the impedance data shown in Figure 6.27 [25], (Reproduced by permission of ECS—The Electrochemical Society, and the authors, from Li G, Pickup PG. Ionic conductivity of PEMFC electrodes.)...

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