Automotive applications, oxygen

Where R is the gas constant, T is the temperature, and F is the Faraday constant. Caused by the logarithmic correlation between the gas concentration and the voltage signal, the potentiometric measurement is best suited for measurements of small amounts of oxygen. A well-known application of this principle has been realized in the so called lambda-probe for automotive applications where they are used to control the lambda value within a small interval around 1 = 1. The lambda-value is defined by the relation between the existing air/fuel ratio and the theoretical air/fuel ratio for a stoichiometric mixture composition ... 

While this paper will concentrate on oxygen sensors as used in automotive applications, there is increasing interest in their use in the measurement and control of industrial and other furnaces in order to reduce fuel costs by maximizing the combustion efficiency. They have also been used for many years to measure the oxygen content of molten glass, of molten steel and other metals and for numerous other applications where a measurement of the oxygen partial pressure is desired. 

While a number of designs have been used, most oxygen sensors for automotive applications consist of a hollow, closed end tube, a schematic of which is shown in Figure 2. As shown, the interior of the closed end tube is open to the atmosphere which serves as a constant or reference oxygen partial pressure while the exterior is exposed to the exhaust gas. The voltage signal produced by the electrolyte is sensed by electrodes on the inner and outer surface of the sensor. These, in turn, are connected to the electronics package of the closed loop system. 

One other type of oxygen sensor has received considerable attention as an alternative to the galvanic type of sensor. This is the resistive type of sensor which uses a metal oxide whose resistance is dependent on the oxygen partial pressure (6). While a number of different oxides have been used, titanium oxide appears to have the best combination of properties for automotive applications (y. 

Oxygen sensors, in low volume use as part of a closed loop emission control system for automotive applications since 1977, have seen wide-spread use starting with the 1981 model year. At the present time, a partially stabilized zirconia electrolyte using yttrium oxide as the stabilizer appears to be the most common choice for this application. 

Logothetis, E.M. (1987) In Turner, D.R. (Ed.) Oxygen Sensors for Automotive Applications, in Chemical Sensors. Electrochemical Society, p. 142. 

Most of the emphasis of this chapter is on the mixed-oxide solid solution oxygen storage materials that comprise the advanced catalyst formulations in use today and are still under development. In particular, we focus on their durability, both with respect to thermal and chemical deactivation, while also briefly reviewing special uses of these and other oxygen storage materials in automotive applications. 

The use of air is convenient for automotive applications, but if the autothermal scheme were to be used for large industrial plants, dedicated oxygen production for the feed would be preferable, e.g. due to concerns over the volume of N2 to be handled and the associated size of heat exchangers (Rostrup-Nielsen, 2000). 

Oxygen sensors are the most widely used solid electrolyte-based sensors [393-395], because the control of oxygen concentrations is critical to controlling the combustion process. For automotive applications, exhaust gas oxygen (EGO) sensors provide critical information for controlling the air-to-fuel ratio for internal combustion engines [396, 397]. Tlte use of an optimal air-to-fuel ratio leads to increased efficiency and reduced emissions. 

Oxygen sensors in automotive applications are used to measure the air fuel (A/F) ratio of engine exhaust gases and to control the optimum A/F ratio for perfect exhaust gas after-treatment by catalytic converters [1]. Therefore, they are also known as lambda or A/F ratio sensors. 

A typical example includes the yttria-stabilized-zirconia-based high-temperature potentiometric oxygen sensor which is widely used in automotive applications. Platinum thick films are applied, forming both the cathode and anode of the sensor. The thick electrode has a porous structure which provides a larger electrode surface area compared to non-porous structures. For current measurement, a porous electrode is desirable since it leads to a larger current output. If the metallic film serves as the electrocatalyst, a porous structure is also desirable, for it provides more catalytic active sites. On the other hand, electrodes formed by the thick-film technique do not have an exact, identical... 

High performance and low cost oxygen (air) cathodes are of vital importance in metal/air batteries concerning systems for automotive applications. Energy and power-losses, mainly due to the high cathodic polarization, expensive catalysts are the main problems of oxygen cathode for metal/air batteries. 

It has been reported in the course of this review that a recent study of the targets of a costless electrocatalyst to replace Pt in automotive applications requires that such non-noble metal catalysts have an activity no less than 1/lOth of the current industrial Pt activity under equivalent conditions. This requires mainly a sizeable increase in the site density (defined as catalytic sites/cm in the electro-catalytic layer) of the non-noble metal catalysts. A knowledge of the molecular structure of the catalytic site for the electrochemical reduction of oxygen in acid medium is, therefore, essential in order to increase the site density on the carbon support for those catalysts. The long-term stabilities of the same catalysts under current industrial conditions are yet to be demonstrated, as weU. 

Italmatch supplies red phosphorus in a stabilised form, encapsulated in a polymer to avoid spontaneous reactions with oxygen or moisture. The product is known as Masteret and it has applications in electrical appliances, construction and automotive applications, and PU foams. Masteret is said not to harm aquatic life. 

At present, the commercial large-scale use of PEM fuel cell technology, particularly in automotive applications, is limited by the relatively high cost and insufficient durability of the currently available electrocatalyst materials used for the oxygen... 

Ceramic sensors are devices that provide environmental feedback by transforming a nonelectrical input into an electrical output. The applications for which these devices are used are widely varied. A brief list includes the use of sensors to determine the concentration of various gases, such as oxygen and carbon monoxide, temperature measurement devices, and pressure, radiation, and humidity sensors. Sensors have also become widely used in automotive applications. In manufacturing, because of the increasing need for waste minimization, process control, and environmentally conscious manufacturing, the increasing emphasis on sensor use and development is likely to continue to expand. The use of feedback loops in conjunction with sensors for process control/optimization has also increased in recent years. 

The greatest problems of PEFC technology are the need for developing more efficient and stable catalysts for ORR and imderstanding the laws of liquid water transport in these cells. Water is produced in the ORR and wets the membrane, which conducts protons only in a wet state. On the other hand, the excessive water blocks the pores in the GDL and retards oxygen transport to the catalyst sites. Accurate water management requires a compromise between the two issues. Note that the requirements of automotive applications are more stringent in particular, PEFCs for vehicles should withstand multiple start-stop cycles and low temperatures. 

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