Oxygen partial pressure minimum

As an example, we briefly describe here the observations made for Laj. Cax-Fe03. In this solid solution system, a single perovskite-brownmillerite intergrowth structure ( = 3) is foimd at composition x = % [224]. The intergrowth structure exhibits ideal stoichiometry, i.e. LaCa2Fe30g, at reduced oxygen partial pressures near the minimum observed in the electrical conductivity [199]. For any other composition, a disordered intergrowth is observed. 

Table 1 shows the equilibrium oxygen partial pressure of several metal oxides, i. e. the minimum oxygen partial pressure which is required for oxide formation. A comparison with Table 2, in which typical oxygen partial pressures of industrial processes are listed, clearly demonstrates, that in coal gasification processes and petrochemical plants stable oxide scales can only be expected on alumina formers. Chromia becomes unstable at the low oxygen partial pressures encountered in such processes. 

As expected, no carburisation attack at all was detected on iron-aluminium-chromium alloys after 1000 hours exposure in CH4/H2 environments at 850°C, 1000°C and 1100°C. Since the formation of chromia and iron requires relatively high oxygen partial pressures, alumina is the only stable phase at the low partial pressure of the used gas. If once formed, alumina is impervious to carbon, provided the scale remains intact [20], Excellent resistance to carburisation was also found for other alumina forming alloys like nickel aluminides [21] and Ni-Al-Cr alloys [22], The results of the present work show that 10 wt% aluminium are sufficient to prevent carburisation. It is expected, that the minimum aluminium concentration is even lower than 10 wt%. 

SC-SOFCs do not require a fuUy dense, gas-tight electrolyte. Respecting a minimum thickness to avoid contact between the electrodes and short-circuits [18], SC-SOFCs can be fabricated with porous electrolytes at lower manufacturing temperatures and costs. An oxygen partial pressure gradient can be established across a porous... 

The rate of solvent regeneration is affected by the oxygen partial pressure, but the volume of air required must be above the minimum stoichiometric value. At atmospheric pressure, the air volume required to regenerate SulFerox solution is typically in the range of 2 to 3 times stoichiometric (Allen, 1993). Regeneration is usually carried out at low pressure (typically 10 psig) to minimize regeneration air compression costs. 

Matsubara et al. [126] used oxygen radical-assisted PLD to grow highly transparent and low-resistivity Al-doped ZnO films at room temperature. A KrF excimer laser (X = 248 nm, 30 ns pulse width, 10 Hz repetition rate) was used for ablation. The oxygen partial pressure during deposition was 0.7-1.4 x 10 Torr, and the applied RF power was 150W. The distance between the target and the substrate was approximately 6 cm. The minimum resistivity of the obtained transparent films was... 

The criterion for the minimum solute concentration, Ng, of a binary A B alloy required for the second transition process has been derived based on thermodynamic and kinetic analyses. Using this equation the effects of oxygen partial pressure, addition of rare earth elements, surface micro-crystallization, and the gettering effects on the transition between external and internal oxidations can be explained. 

Life-Support Applications. Exploration of outer space by humans has focused considerable attention on maximum as weU as minimum limits in the oxygen content of life-support atmospheres. Above the earth, both the atmospheric pressure and the partial pressure of oxygen decrease rapidly. The oxygen content of air remains constant at 20.946% to an altitude of ca 20 km, after which it decreases rapidly (1). 

NOTE The operational efficiency of a deaerator is governed by its potential to reduce the partial pressure of oxygen in the FW to a minimum. The equilibrium concentration of any gas (such as Of) dissolved in a liquid (i.e., the gas s solubility) is proportional to the partial pressure of that gas in contact with the liquid. This relationship is expressed by Henry s Law ... 

Table II gives the temperature interval, the number of laboratories that Battino judges have published reliable solubility data, the number of experimental values used in the linear regression, the linear regression standard deviation at the midpoint temperature, and the temperature of minimum mole fraction solubility (maximum value of Henry s constant) at one atmosphere partial pressure of the gas. For all of the gases except oxygen only a three constant equation was used.

The minimum mass concentration of oxygen required for fish life is 4 mg-L-1. (a) Assuming the density of lake water to be 1.00 g-mL 1, express this concentration in parts per million by mass, mg-kg L (b) What is the minimum partial pressure of 02 that would supply the minimum mass concentration of oxygen in water in order to support fish life at 20°C (see Table 8.5) (c) What is the minimum atmospheric pressure that would give this partial pressure, assuming that oxygen exerts about 21% of the atmospheric pressure ... 

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