Oxidation diffusion

The results presented by Bagley et al. [45] imply that the oxide diffusion coefficient is much smaller in the steady-state regime than in the diffusion-controlled regime where physical bombardment is absent. It may be possible to account for this effect in terms of the diffusive transport model presented earlier by using a smaller oxide diffusion coefficient in the steady-state regime. To explore this possibility, one may set dX/dt= 0 in Eq. 7 to obtain... 

Consider a spherical metal particle that is undergoing a high-temperature surface oxidation process. The product of this reaction is a nonvolatile oxide that immediately dissolves in the metal itself. The surface reaction and oxide dissolving rates are very fast compared to the oxidizer diffusion rate. Calculate an expression for the burning rate of this metal. 

Nitric oxide diffuses into the cell and directly activates a soluble, cytoplasmic guanylate cyclase, so no receptor or G protein is required. 

Red blood cells typically contain 20 mM oxyhemoglobin and thus will destroy nitric oxide diffusing into the vascular stream. Nitric oxide can diffuse over... 

In blood-containing vascular beds, the inactivation of nitric oxide by oxygen is of minor importance because of the rapid and irreversible reactions of nitric oxide with oxyhemoglobin in red blood cells. Any nitric oxide that diffuses into the vascular lumen will be quickly destroyed, making blood vessels effective sinks for nitric oxide. The half-life of nitric oxide is sufficiently long that nitric oxide diffusing into the vascular smooth muscle could also diffuse back out to the lumin to be inactivated by hemoglobin in red blood cells. 

Cage Effect in Solid Polymers Migration of Free Valence in Solid Polymers Initiated Polymer Oxidation Diffusion of Dioxygen in Polymer Diffusion Regime of Polymer Oxidation Isomerization of Alkyl and Peroxyl Radicals of Polypropylene... 

In liquid phase oxidations diffusivities are about 1/104 times those existing in the gas phase, and from the pores humic acids and benzenoid acids are removed whose mean diameters are very large compared with the average pore diameter in coal and molecules such as nitrogen and methanol. 

Gas Solid S/G Adsorption, catalysis, corrosion, oxidation, diffusion, surface states, thin films, condensation and nucleation, permeation, energy transfer. 

Let us consider the burning of an ideal spherical particle in static gas. The oxidant diffuses to the surface of the particle to react with the carbon C + CO2, while the latter diffuses out from the surface of the particle. The combustion heat is transferred to the surrounding gas partially by convection and partially by radiation. The following assumptions were made in the modeling (1) The process is at a pseudo steady state. (2) The temperature the highest at the surface, and continuously drops down outwards from the surface of the particle and the concentration of oxidant is highest in the bulk... 

Hvpolimnetic Sulfate Reduction. Little Rock Lake exhibits dimictic circulation, but the volume of the hypolimnion is only about 3% of the total lake volume. Oxygen depletion occurs in late summer, and a buildup of H S and Fe2+ is observed following the development of anoxia. Sulfate depletion is observed (Figure 4), but hypolimnetic reduction is a minor sulfate sink for the whole lake because the hypolimnion is small and because much of the hypolimnetic H2S entrained in the water column during turnover probably is reoxidized. Using an oxidation- diffusion model we estimate that about half of the hypolimnetic H S entrained in the water column during turnover is oxidized and tne other half is lost by diffusion to the atmosphere no more than 5% of annual S input leaves by emission of H2S produced within the hypolimnion. 

This mechanism is in agreement with the mechanism proposed by others (Belin et al., 1989 and 1995 Martin et al., 1986a, Willermet et al., 1992) using extended X-ray absorption fine structure spectroscopy (EXAFS) and infrared spectroscopy. When ZDDP is present in the lubricant formulation, the radial distribution function (RDF) indicates that crystalline iron oxide diffuses into the polyphosphate network material. 

The process of particle combustion depends on the physical and chemical nature of the solid as it heats and burns. Coal is a complex material of volatile and nonvolatile components which becomes increasingly porous during volatilization of low-boiling constituents in burning. The crucial practical questions for boiler design concern whether pulverized fuel combustion is controlled by oxidizer diffusion or by chemical kinetics. 

Density layer = 15.85-15.95 kgm-3. In the middle of the redox zone, oxidizers diffusing from the upper layer (oxygen and nitrate) decrease to zero. This occurs simultaneously with the disappearance of reductants (ammonia, Mn(II), methane) diffusing up from the anoxic zone. A minimum of phosphate is also found here. This layer may be very thin, probably only 3-5 m, and its position may vary over the density range specified. 

Rates given in Table I for coke aggregate are measured under conditions which indicate relative reactivity, not limited by oxidant diffusion rates. 

Anode porosity is important because it affects the extent of oxidant-accessible surface. This surface is influenced both by coke microstructure and the fabrication process for converting the raw materials into baked carbon. The prime requirement for good anode carbon is minimum oxidant-accessible surface. It is also desirable that this surface have a low, uniform specific reactivity. Anode surface with pores having diameters in the 1-10 micron range are accessible to oxidation unless blocked in some manner. Submicron porosity, such as that produced by thermal desulfurization of coke, is oxidant diffusion-limited and will not affect carbon consumption significantly. Increasing anode carbon density will usually increase anode performance because the oxidant-accessible surface is reduced. 

For a single pollutant biofilter application, using the stoichiometric coefficients v for complete pollutant oxidation, diffusivities D, and molecular weights (MW), the maximum acceptable inlet biofilm interface pollutant POL concentration SPOl can be estimated from the maximum available biofilm interface oxygen concentration Sq2 ... 

The equation (6) defines three factors, affecting on polymeric materials thermostability polymer chemical constitution, characterized by value Tm structure of polymeric meet, characterized by dimension Af and type (intensity) oxidant diffusion, connected with structure and characterized by exponent P [14]. 

Attention it is draw the fact, that the experimental values T5% are above theoretical and this discrepancy increases at contents Z raising. For values T5%, obtained in helium atmosphere, where in virtue of absence of external oxidant diffusion processes do not play any role, the condition 7 5o/o=const=708 4 K is carried out, that ought to be expected. 

You have grown an oxidizable metalhc thin film, but must handle it briefly in air before sealing it in a storage container. How would you evaluate the thickness of the native surface oxide, and how deep the oxide diffuses into the thin film, as the sample is annealed ... 

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