Electric performance

Materials play an important role ia the electronics iadustry. The effectiveness of the electrical performance of the system, its reUabiUty, and its cost aU. depend on the packagiag materials used, which are chosen for their properties and appHcations. As a result, the practicing engineer must have ready access to current information on the materials that can be used ia product development. This article gives an overview of the various material choices for the elements of an electronic product. 

The properties of gas ions are of great importance for the electrical performance of an electrostatic precipitator. They also are very important for particle-charging processes. The size of gas ions is normally such that they can be regarded as gas molecules carrying a single elementary charge. It can even be assumed that ions form a gas component with a very low- partial pressure. Thus, the thermal motion of gas ions is assumed to be similar to that of gas molecules. The most important parameters describing the properties of gas ions are... 

The electrical engineer likewise takes basic process and plant layout requirements and translates them into details for the entire electrical performance of the plant. This will include the electrical requirements of the instrumentation in many cases, but if not, they must be coordinated. 

Alkyd They are easy to mold, have high heat resistance, and excellent electrical performance, and may be light-colored. 

Allyl They have high heat and moisture resistance, good electrical performance in automotive and aerospace uses, good chemical resistance, dimensional stability, low creep (see Diallyl phthlate). 

The results suggest that the development of high performance catalyst and ASC (anode supported cell) is needed to improve the convasions of CO2 and CFLtand electrical performance. 

Summary of DMFC Electrical Performances Currently Achieved (Single Cell)... 

Widely used parameters are the specific energy or power per unit mass (w = W/M, in Wh/kg, orp = P/M, in W/kg). In each battery type the specific energy is a falling function of specific power. Plots of w vs. p (Ragone, 1968) yield a clear illustration of the electrical performance parameters of given types of batteries and are very convenient for their comparison (see Fig. 19.4). 

From the 1960s onward, alkaline zinc-manganese dioxide batteries started to be produced. They have appreciably better electrical performance parameters (see Section 19.4.3) but do not differ from Leclanche batteries in their operating features, are produced in identical sizes, and can be used interchangeably with them. Thus, a gradual changeover occurred and phaseout of the older system is now almost complete. 

Such bimetallic alloys display higher tolerance to the presence of methanol, as shown in Fig. 11.12, where Pt-Cr/C is compared with Pt/C. However, an increase in alcohol concentration leads to a decrease in the tolerance of the catalyst [Koffi et al., 2005 Coutanceau et ah, 2006]. Low power densities are currently obtained in DMFCs working at low temperature [Hogarth and Ralph, 2002] because it is difficult to activate the oxidation reaction of the alcohol and the reduction reaction of molecular oxygen at room temperature. To counterbalance the loss of performance of the cell due to low reaction rates, the membrane thickness can be reduced in order to increase its conductance [Shen et al., 2004]. As a result, methanol crossover is strongly increased. This could be detrimental to the fuel cell s electrical performance, as methanol acts as a poison for conventional Pt-based catalysts present in fuel cell cathodes, especially in the case of mini or micro fuel cell applications, where high methanol concentrations are required (5-10 M). 

Caillard A, Coutanceau C, Brault P, Mathias J, Leger JM. 2006. Structure of Pt/C and PtRu/C catalytic layers prepared by plasma sputtering and electric performance in direct methanol fuel cells (DMFC). J Power Sources 162 66-73. 

Rousseau S, Coutanceau C, Lamy C, Leger JM. 2006. Direct ethanol fuel cell (DEFC) Electrical performances and reaction products distribution under operating conditions with different platinum-based anodes. J Power Sources 158 18-24. 

Each printed TFT element is composed of nanoscale conducting, dielectric, or semiconducting particles. The electrical performance of the printed transistors and printed integrated circuits is dependent on the uniformity of the... 

The information in the previous sections can be used to determine a mass balance around a fuel cell and describe its electrical performance. System analysis requires an energy or heat balance to fully understand the system. The energy balance around the fuel cell is based on the energy absorbing/releasing processes (e.g., power produced, reactions, heat loss) that occur in the cell. As a result, the energy balance varies for the different types of cells because of the differences in reactions that occur according to cell type. 

Kadjo, A. J. J., Brault, R, Caillard, A., Coutanceau, C., Gamier, J. R, and Martemianov, S. Improvement of proton exchange membrane fuel cell electrical performance by optimization of operating parameters and electrodes preparation. Journal of Power Sources 2007 172 613-622. 

Permeability. The separators should not limit the electrical performance of the battery under normal conditions. Typically the presence of separator increases the effective resistivity of the electrolyte by a factor of 6—7. The ratio of the resistivity of the separator filled with electrolyte divided by the resistivity of the electrolyte alone is called MacMullin number. MacMullin numbers are as high as 10—12 have been used in consumer cells. 

Gurley (Air Permeability). Air permeability is proportional to electrical resistivity, for a given separator morphology. It can be used in place of electrical resistance (ER) measurements once the relationship between gurley and ER is established. The separator should have low gurley values for good electrical performance. 

After rehearsing the working principles and presenting the different kinds of fuel cells, the proton exchange membrane fuel cell (PEMFC), which can operate from ambient temperature to 70-80 °C, and the direct ethanol fuel cell (DEFC), which has to work at higher temperatures (up to 120-150 °C) to improve its electric performance, will be particularly discussed. Finally, the solid alkaline membrane fuel cell (SAMFC) will be presented in more detail, including the electrochemical reactions involved. 

The experiments were carried out using Pt/C, Pt-Sn/C and Pt-Sn-Ru/C catalysts and in each case no other reaction products than AAL, AA and CO2 were detected. The addition of tin to platinum not only increases the activity of the catalyst towards the oxidation of ethanol and therefore the electrical performance of the DEFC, but also changes greatly the product distribution the formation of CO2 and AAL is lowered, whereas that of AA is greatly increased (Table 1.2). 

The first methanol-fed PEM EC working with an AEM was conceived by Hunger in 1960 [15,45]. This system contained an AEM with porous catalytic electrodes pressed on both sides and led to relatively poor electrical performance (1 mA cm at 0.25 Vat room temperature with methanol and air as the reactants). Since this first attempt, many studies have been carried out to develop alkaline membranes. 

Electrode materials in principle should not bear on ohmic drop problems. In practice, they can do, if the conductivity is poor and the thickness of the active film is sizable. Thus, although in principle IR should not depend on electrode materials but only on cell design, in practice catalytically active materials with poor electrical performance cannot be used industrially since they would unacceptably increase the energy consumption for the product unit. 

To avoid misleading results, the electronic characteristics of a device always have to be analyzed in a proper statistical manner to characterize the results of the process in terms of device structure details, yield, electrical performance, and durability. 

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