Working temperature range

These grades possess a high dr op point, of the order of 180°C, and a working temperature range from -30"C to + I30°C. 

Nitrile rubbers, including fiber-reinforced varieties, are used both as radial shaft-seal materials and as molded packing for reciprocating shafts. They have excellent resistance to a considerable range of chemicals, with the exception of strong acids and alkalis, and are at the same time compatible with petroleum-based lubricants. Their working temperature range is from —1°C to 107°C (30°F to 225°F) continuously and up to 150°C (302°F) intermittently. When used on hard shafts with a surface finish of, at most, 0.00038 mm root mean square (RMS), they have an excellent resistance to abrasion. 

The fluorine concentration in hydrofluorides of tantalum and niobium is an extremely important issue. Fluorine that separates into the gaseous phase interacts with the construction elements of the furnaces, leading to additional contamination of the final product by silicon, aluminum, etc. Thus, it is recommended to perform diying in crucibles made of Teflon or polypropylene with appropriate temperature limitations. Use of crucibles made of carbon-glass ensures high quality and a broad working temperature range, at least up to 300-350°C. 

The requirements for plate materials in a fuel cell stack for different markets or applications can be quite different due to fuel cell working conditions and specific needs for the power, lifetime, weight, volume, size, and acceptable cost range. For example, in addition to basic requirements of all plate materials for their common functions, the plate material used in transportation fuel cells, such as that used in automotive applications, would be significantly different from requirements in stationary stacks in terms of working temperature range, density, durability, and lifetime. 

The gas phase detection of iodine vapor with an electrochemical probe has been investigated [195]. The Ag AgI Au electrochemical cell was observed to be sensitive to interference from both oxygen and humidity. A sensor based on a Ag Ag(Cs)I graphite electrode system has been reported by Sola etal. [196]. Temperature effects were studied and the effect of Csl doping of the Agl explored to widen the working temperature range. 

Type T (copper-constant) thermocouples are most applicable in steam sterilizer validation work. Their working temperature range is wide and they are resistant to corrosion in moist environments. A high grade of thermocouple wire should be chosen. Premium grades of wire accurate to as close as 0.1°C at 121°C are recommended. These must then be calibrated against a temperature standard traceable to the National Bureau of Standards (NBS). 

Efforts to eliminate grease from sensitive parts of vacuum lines have resulted in the use of a number of new materials with low vapour pressures, an extended working temperature range, and improved resistance to a number of chemicals. Three of the most important of these materials are described. 

Neoprene. Neoprene is an elastomer with mechanical properties very similar to natural rubber. It is manufactured by Du Pont and has a safe working temperature range of -15°C to 80°C. It is resistant to oils, to organic solvents, to some caustic solutions and to salts. It is not suitable for hydrogen peroxide or sulphur trioxide. Neoprene has low permeability to gases and is good for high vacuum and static vacuum systems. 

The sluggish oxygen reduction reaction (ORR) in the cathode catalyst layer (CCL) induces a major fraction of voltage losses in PEFCs. Due to the requirement of sufficient membrane humidification, discussed in Sect. 8.2.2, and the limitation it imposes on the working temperature range (< 100 °C) only platinum-based catalysts can provide acceptable reaction rates. Platinum, however, is costly, and its resources are limited. 

The calculated standard thermodynamic functions for carbonyl difluoride, Cj, S, (G - HjgjVT, (H - W gg), AHf, Gf and log,g(Xf), are listed in Table 13.9 for the extended temperature range 0-6000 K in the ideal gas state [359aa], and are illustrated over the more normal working temperature range [359aa] in Fig. 13.2. Earlier values for these thermodynamic properties have now been superseded [1171,1280,1360c,1587,1972,1973]. 

Y,Zrj -,O2 /2 ceramics, the maximum conductivity is obtained for x 0.10. Higher concentrations of dopant cations decrease conductivity by the effect of their progressive association with oxygen vacancies. The working temperature range extends from 400 to 1600°C for partial pressures of oxygen between 10 ° and 10 bar. 

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