Oxygen concentration, surface materials

Slime is a network of secreted strands (extracellular polymers) intermixed with bacteria, water, gases, and extraneous matter. Slime layers occlude surfaces—the biological mat tends to form on and stick to surfaces. Surface shielding is further accelerated by the gathering of dirt, silt, sand, and other materials into the layer. Slime layers produce a stagnant zone next to surfaces that retards convective oxygen transport and increases diffusion distances. These properties naturally promote oxygen concentration cell formation. 

The general indication of the results in this table is that the corrosion rates of non-ferrous metals increase with depth in spite of lower temperatures and lower oxygen concentrations than at the surface. It was noted in the paper by Kirk that the results at depth were typical of the variation of performance of these materials experienced on numerous occasions in surface sea water. A notable exception was for aluminium alloys of the 5000 (Al-Mg) and 6000 (Al-Mg-Si) series which had good resistance to corrosion... 

Crevice corrosion is yet another example of corrosion caused by a difference in oxygen concentration between two areas on the metal surface. In this case, the region of low oxygen concentration lies inside a crevice caused by the overlapping of a piece of metal or other material, e.g. the crevice which exists under a washer pressed onto a metal surface (Fig.6). Even if the washer is insulating (e.g. nylon) as is used for mounting test coupons, corrosion will still occur. 

Interpretation is that WOF4 is probably the dominant product formed at the tungsten surface in SF6—02. The nature of the final product desorbed in the gas phase depends on the fluorine and oxygen concentration in the gas phase. If these fluxes are high (as in the case of a plasma-insensitive electrode material, such as... 

Amorphous silicon oxidizes upon exposure to air, at a rate which depends on the microstructure of the film. Columnar material (see Section 2.1.1) oxidizes rapidly along the surface of the columns because the intercolumnar regions are porous. The surface area of the columns is so large that an effective oxygen concentration of 10-20 at%... 

The oxygen-containing surface groups are responsible for the potential response of carbon electrodes to hydrogen ion concentration in. solution. Potential measurements of carbon materials in buffer solutions show that the relationship E = /(pH) is linear in the pH range 2.0-7.0 and can be de.scribed by a linear equation with a slope between 20 and 60 mV/pH. depending on the nature of the electrode material [160,161]. 

Here, S is the specific surface area of the catalyst, a is the conversion and F is the gas flow. The term FjS is the area velocity. The rate constant depends on the type of catalyst material, the oxygen concentration, and the temperature. Additionally, it was found that the rate constant depends on the velocity in the channels, which implies that transport phenomena have an effect on the NO conversion. 

The pressence of oxygen near a burning polymer surface has been recorded by many investigators 3 106 108>. But the oxygen concentration was observed to decrease with the distance from the front edge of the flame, as the ambient oxygen concentration increased 106). These facts are perfectly consistent with the theoretical conceptions of diffusion flame combustion of materials discussed in Sect. 3 82-84). 

The maximum oxygen concentration in surface oxides depends on the specific surface area of the parent carbon material values of 15 Mo 25 oxygen are reported for sugar charcoal. An oxygen content in this range corresponds to an acid content (determined by neutralization with NaOEt) of 2 to 3 mequiv g h... 

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