Current-conducting structure

A supporting conductive structure, made of a nickel-wire woven net, silver-plated in order to minimise corrosion of the substrate arising from the operating conditions, and able to distribute the current uniformly all over the surface. 

Although the matrix may have a well-defined planar surface, there is a complex reaction surface extending throughout the volume of the porous electrode, and the effective active surface may be many times the geometric surface area. Ideally, when a battery produces current, the sites of current production extend uniformly throughout the electrode structure. A nonuniform current distribution introduces an inefficiency and lowers the expected performance from a battery system. In some cases the negative electrode is a metallic element, such as zinc or lithium metal, of sufficient conductivity to require only minimal supporting conductive structures. 

In an SOFC, the electrochemical reactions take place in the electrodes in the functional layer, that is, a zone within a distance of less than 10-20 pm from the electrolyte surface [5,136-138], The portion of the electrode beyond this width is principally a current collector structure, which has to be porous to permit the admission of gas to the functional layer where the oxidation and reduction reactions occur. Besides, the electrolyte has to be gas impermeable to avoid direct combination and combustion of the gases [137], The essential parts of the SOFC, that is, the electrolyte, the anode, and the cathode, are made of ceramic materials produced with appropriate electrical conducting properties, chemical and structural stabilities, similar expansion coefficients, and negligible reactivity properties [135],... 

Fig. 22 Schematic self-assembled transverse-witlzin-parallel aligned structure of PS-6-P4VP(TSA)i.o(PDP)i.o supramolecules and the direct-current conductivity as a fimction of temperature. Presented also is the isotropic conductivity of a nonaligned sample (4). In the aligned case (3) the conductivity is increased, probably due to fewer domain boimd-aries, and the nanoscale conductivity anisotropy is manifestly present [155]...

For a number of years the existence of a porous or polar pathway through the stratum comeum, in parallel with the lipoidal pathway, has been hypothesized. Although there has been some criticism of this concept, it is our belief that the root of the lack of a common consensus among scientists in the field can be attributed largely to the limited number of systematic studies in the literature that directly address the issue of the diffusion of polar and ionic permeants across skin. Based upon recent studies that have focused upon this aspect of transdermal diffusion, the existence of a porous permeation pathway through HEM is clear (Hatanaka et al., 1993, 1994 Peck et al., 1993, 1994, 1995). At this point, we have made no attempt to correlate the findings from our studies with specific structural properties of the HEM. In some cases, authors have implicated shunt routes such as hair follicles and sweat ducts to account for permeation data not consistent with the concept of lipoidal membrane permeation (Cornwell and Barry, 1993 Scheuplein and Blank, 1971). Under ionto-phoretic conditions, such shunt routes have been shown to contribute to current conduction (Cullander and Guy, 1991 Scott et al., 1993). When efforts have been made to estimate the effective Rp of skin samples under iontophoretic conditions (Ruddy and Hadzija, 1992), osmotic conditions (Hatanaka et al.,... 

In summary, the results which are presented in this section suggest that the charge transport of ions within paper and paperlike structures is essentially the same as that of the transport properties associated with aqueous electrolyte systems. Furthermore, the transient current behaviour which has been observed in these fibrous cellulosic systems show characteristics similar to the ionic transient current conduction exhibited in both dielectric fluids and aqueous ionic systems. 

The superhydrophobicity of the Au particle array can be described in terms of both equations (1) and (2). First, the structure of the Au particle array shows significant wave-like surface, so that air can be trapped in the interstices between micro-particles, which will increase hydrophobicity according to equation (2). Second, surface nano-scale roughness for the individual micro-particles in the array is beneficial towards increasing water CA based on equation (1). Such hierarchically rough Au particle array with superhydrophobicity could be used for micro-fluidic devices or the nano-devices with water-repeUent behavior. Also, on such superhydrophobic surfaces, the contamination, oxidation, and current conduction can be inhibited, and the flow resistance in micro-fluidic channels can also be reduced. 

Let us briefly consider the conducting properties of hybrid nanocomposites. Conducting properties are manifested only with particular inorganic component to polymer ratios in which cmrent-conducting channels of fractal metal-containing clusters are formed in a polymeric matrix for one reason or other. The highest conductivity is achieved when the composite is converted into a network of interrelated current-conducting chains. This is where a percolation structure is achieved. To put it differently, critical concentrations of the filler (p (the percolation threshold) exist above which (9 > 9 ) the conductivity sharply increases. 

An electrochemical device consists of two electrodes with an electrolyte between them. The electrolyte can be a solid or a solution. Solid state electrolytes serve two functions. They conduct ions and separate the positive electrode from the negative electrode. For liquid state electrolytes such as electrolyte solutions, an inert porous separator sheet allows the ions to pass through, creating a conducting current. The structure of an electrochemical capacitor is very similar to that of an electrochemical cell but there is no electron transfer across the interface. 

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