Effect of oxidation

High temperature fatigue and fretting fatigue behavior has also been improved by implantation (113,114). This has been achieved by using species that inhibit oxidation or harden the surface. It is generally accepted that fretting behavior is closely coimected to oxidation resistance, perhaps due to third party effects of oxidation products. Oxidation resistance alone has also been improved by ion implantation (118—120). 

Antioxidants may be assessed in a variety of ways. For screening and for fundamental studies the induction period and rate of oxidation of petroleum fractions with and without antioxidants present provide useful model systems. Since the effect of oxidation differs from polymer to polymer it is important to evaluate the efficacy of the antioxidant with respect to some property seriously affected by oxidation. Thus for polyethylene it is common to study changes in flow properties and in power factor in polypropylene, flow properties and tendency to embrittlement in natural rubber vulcanisates, changes in tensile strength and tear strength. 

Most rubbers used in adhesives are not resistant to oxidation. Because the degree of unsaturation present in the polymer backbone of natural rubber, styrene-butadiene rubber, nitrile rubber and polychloroprene rubber, they can easily react with oxygen. Butyl rubber, however, possesses small degree of unsaturation and is quite resistant to oxidation. The effects of oxidation in rubber base adhesives after some years of service life can be assessed using FTIR spectroscopy. The ratio of the intensities of the absorption bands at 1740 cm" (carbonyl group) and at 2900 cm" (carbon-hydrogen bonds) significantly increases when the elastomer has been oxidized [50]. 

Pick-up of stray current (a.c. or d.c.) (Section 10.5). Decreased use of d.c. in many areas has led to less possibilities of pick-up of direct current from utilities, mines, etc. The importance of grounded a.c. systems has been discounted, but Waters has shown that alternating currents can accelerate corrosion. Furthermore the rectifying effects of oxide films, clay minerals and other soil factors are not understood. 

Work carried out by Gilbert on irons maintained at 500°C for 64 weeks (Fig. 7.15) has shown that in ordinary unalloyed flake irons graphitisation and oxidation cause roughly equal amounts of growth, and that as the carbon content increases the effect of oxidation becomes more important and the overall rate of growth increases. Nodular graphite irons grow very slowly under these conditions. 

To reduce the effects of corrosion, inhibitors are added, typically sodium chromate in the salt brines and sodium phosphate in the glycols. These are alkaline salts and help to counteract the effects of oxidation, but periodic checks should be taken, and borax or similar alkali added if the pH value falls below 7.0 or 7.5 [1]. 

Silicon steel surface, effect of oxidation on x-ray emission spectrography, 221... 

R.D. Gould, Combustion Instability of Solid Propellants Effect of Oxidizer Particle Size, Oxidizer/Fuel Ratio and Addition of Titanium Dioxide to Plastic Pro pell ants , Rept No RPE-TR-68/1, Westcott (Engl)... 

Sulfur dioxide is a reducing bleach and can counter the effects of oxidizing bleaches, thus preserving color in fruits dried in the sun. The combination of fruit acids and ultraviolet light would otherwise react with the colorful compounds, making the fruit pale. 

An example of the effect of oxide-anion associated with the 2n component (i.e. position 1, Equation 1.22) is illustrated in Equation 1.25 [53]. The potassium salt of 1,4-dihydro-11 -hydroxy-9,10-dihydro-9,10-ethanoanthracene undergoes more facile debridging (remotion of ethylene) than the 11-deoxygenated parent compound. 

The effect of oxidative irradiation on mechanical properties on the foams of E-plastomers has been investigated. In this study, stress relaxation and dynamic rheological experiments are used to probe the effects of oxidative irradiation on the stmcture and final properties of these polymeric foams. Experiments conducted on irradiated E-plastomer (octene comonomer) foams of two different densities reveal significantly different behavior. Gamma irradiation of the lighter foam causes stmctural degradation due to chain scission reactions. This is manifested in faster stress-relaxation rates and lower values of elastic modulus and gel fraction in the irradiated samples. The incorporation of O2 into the polymer backbone, verified by IR analysis, conftrms the hypothesis of... 

Fig. 6.10 Examples of the directional effect of oxide ligand arrangement on the location of hard cations and orientation of M-O linkages.

Effect of oxidative treatments on catalytic property of carbon nanofiber composite... 

The effect of oxidation pretreatment and oxidative reaction on the graphitic structure of all CNF or CNF based catalysts has been studied by XRD and HRTEM. From the diffraction patterns as shown in Fig. 2(a), it can be observed the subsequent treatment do not affect the integrity of graphite-like structure. TEM examination on the tested K(0.5)-Fe(5)/CNF catalysts as presented in Fig.2(b), also indicates that the graphitic structure of CNF is still intact. The XRD and TEM results are in agreement with TGA profiles of fi-esh and tested catalyst there is no obviously different stability in the carbon dioxide atmosphere (profiles are not shown). Moreover, TEM image as shown in Fig. 2(b) indicates that the iron oxide particle deposited on the surface of carbon nanofibcr are mostly less than less than 10 nm. 

THAI S F, LEWIS J G, WILLIAMS R B, JOHNSON S P And ADAMS D O (1995) Effects of oxidized LDL on mononuclear phagocytes inhibition of induction of four inflammatory c)dokine gene RNAs, release of NO, and cytolysis of tumor cells Journal of Leukocyte Biology 57, 427-33. 

Based on the characterization studies and the behavior of the model systems, it appears that the promotion effect of oxides of Ti, V,... 

Effect of oxidant nature on benzene oxidation (X-benzene conversion, S-selectivity to phenol)... 

Under the effect of oxidizing agents, a metal may become passivated even when not anodically polarized by an external power source. In this case, passivation is evident from the drastic decrease in the rate of spontaneous dissolution of the metal in the solution. The best known example is that of iron passivation in concentrated nitric acid, which had been described by M. V. Lomonosov as early as 1750. Passivation of the metal comes about under the effect of the oxidizing agent s positive redox potentiaf. 

Passivation of the metal and the associated sharp decline of its anodic dissolntion rate have a strong effect on corrosion rates (curve 5 and the point of intersection C in Fig. 22.2b). Passivation is encountered more often under the effect of oxidizing agents (e.g., in the presence of oxygen). 

Tin disulphide has the same dangerous reactions as sulphides, for which sulphide anion is very sensitive to the effect of oxidants. So the effect of chloric acid and chlorates gives rise respectively to violent detonations and the formation of spectacular showers of sparks. Dichlorine oxide detonates, but this is to be expected. 

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