Metal Oxidation Incubation

Two mechanisms have been suggested for the formation of spinel Direct oxidation of the alloy melt through cracks in the MgO film [48,49] or an interfacial displacement reaction between aluminum and MgO, followed by solid state diffusion of magnesium through the oxide to repeat the oxidation to MgO at the surface [47,51], 

Evidence for the latter mechanism includes the smaller molar volume of oxygen ions in spinel when compared to that in magnesia, so that for a given quantity of 

The oxide at the external surface of the composite is predominantly a thin (0.1 pm) layer of MgO with an intermittent, underlying spinel layer The microstructure is discussed below. It could be argued that the entire process of incubation and reinitiation is caused by excess magnesium, and that a starting composition near the three-phase equilibrium should trigger immediate growth of alumina. However, controlled growth of a DM0 composite has never been reported from a bulk 

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Metal oxide surfaces become more hydrophilic with time of incubation with aqueous solutions probably due to penetration of water in a porous... 

In the case of MnO/ ( it is known to reduce on the surface of CNTs and graphene spontaneously to produce Mn02 NPs [182,183]. Solvothermal assisted precipitation of metal oxides can occur in milder solutions [184]. For example, mixed metal oxide NPs of CoFe204 have been deposited on GO from metallic salt precursors via the addition of ethanolamine followed by incubation at 180 °C in a sealed vessel [185]. Mixing GO with Cd2+ in DMSO followed by solvothermal treatment has been shown to both reduce GO to RGO and coat with CdS QDs [186]. 

To show further that the cells were firmly attached to the hydrous metal oxide, a different microorganism, Serratia marcescens was employed. When incubated in nutrient medium at 25°C, this organism produces a distinctive red colouration, which enables the immobilised cells to be distinguished readily... 

Most superalloys contain some refractory elements such as molybdenum and tungsten. When the oxides of these elements accumulate in molten deposits, very severe hot corrosion attack can occur. The degradation is characterized by an incubation period during which the attack is not severe, followed by much more rapid attack as the refractory metal oxide in the molten deposit reaches a level to produce catastrophic degradation. Microstructures typical... 

Passive adsorption of stearic acid, a classic lubricant additive, from an alkane solution on metal oxides has been studied by several authors 34,35). Over a period of 1 minute to several days (probably depending on the reactivity of the surface) stearic acid self-assembles on the surface to form a dense monolayer. This is an alternative method to form a methylated surface. Figure 6b shows FRAP curves obtained at different incubation times between the SA - hexadecane solution and the sapphire surface. Unlike the previous experiment the system was not dismantled and readjusted between different measurements, eliminating errors due to alignment. The fluorescence recovery appears faster after a few days of contact compared to short times of incubation, revealing that hexadecane slips on the adsorbed stearic acid layer formed in situ. 

The DMO process consists of a brief period of rapid oxidation, incubation with little oxidation, then substantial oxidation and formation of the bulk metal-metal oxide composite. 

There is often a period before corrosion starts in a crevice in passivating metals. This so-called incubation period corresponds to the time necessary to establish a crevice environment aggressive enough to dissolve the passive oxide layer. The incubation period is well known in stainless steels exposed to waters containing chloride. After a time period in which crevice corrosion is negligible, attack begins, and the rate of metal loss increases (Fig. 2.8). 

Nitrosoarenes are readily formed by the oxidation of primary N-hydroxy arylamines and several mechanisms appear to be involved. These include 1) the metal-catalyzed oxidation/reduction to nitrosoarenes, azoxyarenes and arylamines (144) 2) the 02-dependent, metal-catalyzed oxidation to nitrosoarenes (145) 3) the 02-dependent, hemoglobin-mediated co-oxidation to nitrosoarenes and methe-moglobin (146) and 4) the 0 2-dependent conversion of N-hydroxy arylamines to nitrosoarenes, nitrosophenols and nitroarenes (147,148). Each of these processes can involve intermediate nitroxide radicals, superoxide anion radicals, hydrogen peroxide and hydroxyl radicals, all of which have been observed in model systems (149,151). Although these radicals are electrophilic and have been suggested to result in DNA damage (151,152), a causal relationship has not yet been established. Nitrosoarenes, on the other hand, are readily formed in in vitro metabolic incubations (2,153) and have been shown to react covalently with lipids (154), proteins (28,155) and GSH (17,156-159). Nitrosoarenes are also readily reduced to N-hydroxy arylamines by ascorbic acid (17,160) and by reduced pyridine nucleotides (9,161). 

Oxidized LDL are considered to be one of the major factors associated with the development of atherosclerosis. The earliest event is the transport of LDL into the arterial wall where LDL, being trapped in subendothelial space, are oxidized by oxygen radicals produced by endothelial and arterial smooth muscle cells. The oxidation of LDL in the arterial wall is affected by various factors including hemodynamic forces such as shear stress and stretch force. Thus, it has been shown [177] that stress force imposed on vascular smooth muscle cells incubated with native LDL increased the MDA formation by about 150% concomitantly with the enhancement of superoxide production. It was suggested that oxidation was initiated by NADPH oxidase-produced superoxide and depended on the presence of metal ions. 

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