Electrical Contact Performances

ELECTRIC CONTACT PERFORMANCES AND ELECTRICAL CONDUCTION MECHANISMS OF AN ELASTOMERIC CONDUCTIVE POLYMER... 

There are, however, technical limitations to substitution. Some materials are used in ways not easily filled by others. Platinum as a catalyst, liquid helium as a refrigerant, and silver on electrical contact areas cannot be replaced they perform a unique function - they are, so to speak, the vitamins of engineering materials. Others - a replacement for tungsten for lamp filaments, for example - would require the development of a whole new technology, and this can take many years. Finally,... 

Abbott, W. H., Proc. I2th Ini. Conf. on Electric Contact Phenomena, Chicago, p. 47 (1984) Materials Performance, 24 No. 8,46 (1985) Proc. I3th Int. Conf. on Electric Contacts, Lausanne, 343 (1986) Proc. 33rd Int. IEEE/Holm Conf. on Electrical Contacts, Chicago (1987) Proc. Nth Int. Cong, on Electric Contacts, Paris (1988) Koch, G. H., Abbott, W. H. and Davis, G. O., Materials Performance, 27 No. 3, 35 (1988)... 

Porous electrodes are commonly used in fuel cells to achieve hi surface area which significantly increases the number of reaction sites. A critical part of most fuel cells is often referred to as the triple phase boundary (TPB). Thrae mostly microscopic regions, in which the actual electrochemical reactions take place, are found where reactant gas, electrolyte and electrode meet each other. For a site or area to be active, it must be exposed to the rractant, be in electrical contact with the electrode, be in ionic contact with the electrolyte, and contain sufficient electro-catalyst for the reaction to proceed at a desired rate. The density of these regions and the microstmcture of these interfaces play a critical role in the electrochemical performance of the fuel cells [1]. 

Finally, the wafer is immersed in acetone, and the Hft-off process is performed in an ultrasonic bath. The Pt metal layer showed good adhesion to the CMOS-aluminum electrodes and facihtated good electrical contact to the sensitive layer. 

Occasionally, we prepare a different type of electrode - we screen-print them. With modem screen-printing technology, a complicated arrangement of precisely arranged and well-defined electrodes can be prepared on the solid substrate of choice. In essence, these electrodes are simply dots of conductive material, with suitable electrical contacts to ensure that each can be addressed correctly. As an example, each electrode can be connected to a separate channel of a frequency analyser or potentiostat. In this way, a great many analyses can be performed simultaneously. 

DL thicknesses on overall fuel cell performance and concluded fhaf fhe performance of DLs wifh MPL increased considerably when the MPL thickness was increased from 7.5 to 17.5 pm. Their explanation was that very thin MPLs provide poor electrical contact between the CL and the current-collecting FF plate because the electrical resistance is increased due to the roughness of fhe carbon clofh DL. If fhe MPL is too fhin, fhe amount of carbon/PTFE is insufficienf to provide good elecfrical confacf for the collection of fhe currenf generated in fhe fhree-phase reaction zone of fhe catalyst layer. 

For example, the small tolerance and low surface roughness of the plate in manufacture are critical for assuring the high electrical contact conductivity, low fluid flow resistance, and low water holdup to meet performance require-menfs of fhe plates. Moreover, to play the role of removing generated water in the cathode side—particularly to avoid flooding when fhe current density is high, the surface of the cathode plate may need hydrophobicity [11] so as to better adjust hydrophobic and hydrophilic properties of plate materials in cathode and anode plates. This area needs further study. 

Cadmium sulfide particulate films, generated in thicknesses of 300 50 A at arachidic acid (AA) monolayer interfaces, have been characterized in situ by STM under potentiostatic control [644], Electrical contact was made between the tip of the STM, acting as the working electrode (WE), which was in contact with the CdS particulate film floating on aqueous 0.30 M NaCl, and the reference (RE) and counter (CE) electrodes, placed in the subphase (Fig. 112) [644]. A well-defined single-reduction wave at about — 1.15 V was observed. Prolonged exposure to room light shifted the reduction peak to — 0.85 V. Electrical and photoelectrical characterizations have also been performed on Ti-foil-supported, 5000-A-thick CdS particulate films in an electrochemical cell (Fig. 113) [644]. The Ti foil was used as the WE, while the RE and CE were placed into 0.50 M... 

Metrohm and BAS have also introduced improved DME models capable of operating in the SMDE mode. The Metrohm electrode (Fig. 14.6b) has a needle valve and small-bore capillary. Much of it is pneumatically controlled. The BAS version (Fig. 14.6c) is called the controlled growth mercury electrode (CGME). It is based on the work of Kowalski, Osteryoung, and coworkers [30]. Its features include a low-resistance electrical contact to the mercury thread in the capillary via a stainless steel tube and a fast response valve. The fast valve has allowed unique experiments to be performed where precise control of mercury drop growth during the experiment is desirable [31-33]. The BAS (Fig. 14.7), EG G Princeton Applied Research (Fig. 14.8), and Metrohm (Fig. 14.9) electrodes offer this easy and reproducible drop renewal in fully equipped cell stands. 

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