Carbon on iron

Watanabe, S. Matsumoto, S. (1994) Effect of monosilicate, phosphate, and carbonate on iron dissolution by mugineic acid. Soil Sci. 

Like calcium, strontium has moderate mobility in soils and sediments, and sorbs moderately to metal oxides and clays (Hayes and Traina 1998). The Sr2- ion is strongly hydrated and is firmly coordinated with six or more water molecules in aqueous solution. When Sr2- ions sorb on negatively charged mineral surface sites, the hydration sphere is retained (O Day et al. 2000). Strontium sorbs as hydrated ions on the surface of clay minerals (kaolinite), weathered minerals (amorphous silica), and iron oxides (Sahai et al. 2000). Sorbed carbonate on iron oxides enhances the sorption of Sr2- and permits the nucleation of Sr2- as strontium carbonate (Sahai et al. 2000). On calcite (calcium carbonate), Sr2 sorption occurs by electrostatic attraction as hydrated ions. However, at higher concentrations, precipitation of strontianite (strontium carbonate) occurs and strontium is likely to be less mobile (Parkman et al. 1998). 

Figure 4. Schematic of growth mechanism of filamentous carbon on iron carbide. Key left, on rectangular carbide particle and right, on carbide particle with two active faces at oblique angles. (Reproduced, with permission, from Ref. 8.)...

The fomation of carbon on iron and iron-copper catalysts by the reaction 2C0 = C02+C has been studied by several investigators (70-73). The most significant result of this work (in so far as the Fischer-Tropsch synthesis is concerned) is the fact that neither an iron-free nor a copper-free carbon deposit was obtained. The data show that cai-bon is deposited in the crystal lattice of the catalyst and the inability to obtain a copper-free carbon deposit from tests with an iron-copper catalyst shows that iron carbonyl formation will not explain the results. It is very probable that carbon is formed from carbon monoxide b3 way of iron carbide as an intermediate. Carbidic carbon diffuses rapidly throughout the crystal lattice and subsequently decomposes to yield elemental carbon, thus disrupting the lattice structure. 

Properties of intergranular films with widths of a few nm, and with composition and structure distinctly different from those of the mineral pha.ses. have been studied by XPS, SIMS, SAM and related techniques. A specific example concerns the presence of relatively thick (i.e., >25 nm) surface coatings of graphitic carbon on iron sulfide fracture faces after grinding a copper/lead-zinc sulfide ore... 

Austenitic Stainless Steels. These steels, based on iron—chromium—nickel alloys, are not hardenable by heat treatment and are predominandy austenitic. They include Types 301, 302, 302B, 303, 304, 304L, 305, 308, 309, 310, 314, 316, 316L, 317, 321, and 347. The L refers to 0.03% carbon max, which is readily available. In some austenitic stainless steels, all or part of the nickel is replaced by manganese and nitrogen in proper amounts, as in one proprietary steel and Types 201 and 202 (see Table 4). 

Pretreatment of aqueous streams may be required prior to using ion exchange. Suspended soHds that can plug an ion-exchange unit should be reduced to the 10 p.m level. Organics that can foul resins can be removed by carbon adsorption. Iron [7439-89-6] and manganese [7439-96-5], commonly present in ground waters, should be removed because they precipitate on the resin. 

For practical reasons, the blast furnace hearth is divided into two principal zones the bottom and the sidewalls. Each of these zones exhibits unique problems and wear mechanisms. The largest refractory mass is contained within the hearth bottom. The outside diameters of these bottoms can exceed 16 or 17 m and their depth is dependent on whether underhearth cooling is utilized. When cooling is not employed, this refractory depth usually is determined by mathematical models these predict a stabilization isotherm location which defines the limit of dissolution of the carbon by iron. Often, this depth exceeds 3 m of carbon. However, because the stabilization isotherm location is also a function of furnace diameter, often times thermal equiHbrium caimot be achieved without some form of underhearth cooling. 

Palladium and platinum (5—10 wt % on activated carbon) can be used with a variety of solvents as can copper carbonate on siHca and 60 wt % nickel on kieselguhr. The same is tme of nonsupported catalysts copper chromite, rhenium (VII) sulfide, rhenium (VI) oxide, and any of the Raney catalysts, copper, iron, or nickel. 

The evolution of gases, such as in dre example given above of dre formation of CO(g) in dre U airsfer of sulphur between carbon-saturated iron and a silicate slag, requires dre nucleation of bubbles before dre gas can be eliminated from the melt. The possibility of homogeneous nucleation seems unlikely, and the more probable source of gas bubbles would either be at the container ceramic walls, or on detached solid particles of the containing material which are... 

Another subsidiary field of study was the effect of high concentrations of a diffusing solute, such as interstitial carbon in iron, in slowing diffusivity (in the case of carbon in fee austenite) because of mutual repulsion of neighbouring dissolved carbon atoms. By extension, high carbon concentrations can affect the mobility of substitutional solutes (Babu and Bhadeshia 1995). These last two phenomena, quenched-in vacancies and concentration effects, show how a parepisteme can carry smaller parepistemes on its back. 

The incorporation of anions from the electrolyte, such as borate and carbonate, into the oxide has also been shown to occur on iron and cobalt, such anions being restricted to the outer layers of the film. Attempts to find incorporation of chloride into passive iron surfaces from... 

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. 

Direct measurements on metals such as iron, nickel and stainless steel have shown that adsorption occurs from acid solutions of inhibitors such as iodide ions, carbon monoxide and organic compounds such as amines , thioureas , sulphoxides , sulphidesand mer-captans. These studies have shown that the efficiency of inhibition (expressed as the relative reduction in corrosion rate) can be qualitatively related to the amount of adsorbed inhibitor on the metal surface. However, no detailed quantitative correlation has yet been achieved between these parameters. There is some evidence that adsorption of inhibitor species at low surface coverage d (for complete surface coverage 0=1) may be more effective in producing inhibition than adsorption at high surface coverage. In particular, the adsorption of polyvinyl pyridine on iron in hydrochloric acid at 0 < 0 -1 monolayer has been found to produce an 80% reduction in corrosion rate . 

One probable reason for the relatively poor catalyst performance in experiment HGR-10 was the excessively large deposits of iron and carbon on the catalyst surface. Iron and carbon concentrations (Table III) were... 

The results of catalytic activities in the dehydrogenation of ethylbenzene with various iron oxide based catalysts are shown in Fig. l(a-b). The number in the parentheses of the catalyst codes indicates the weight fi-action of metal per gram carbon. On oxidized CNF alone less than 20% conversion of EB is observed after 3 h on stream. The conversion of ethylbenzene... 

If the radical is square pyramidal (C4 ) Fe(CO)5+ (1), the principal axes of the g-matrix must be the molecular axes (the C4 axis and normals to the reflection planes). The iron atom and the carbon of the axial CO group would have the full symmetry of the group and so these hyperfine matrices would share principal axes with the g-matrix. The four equatorial carbonyl carbons, on the other hand, lie in reflection planes, but not on the C4-axis and so are symmetry-required to share only one principal axis with the g-matrix. In fact, the major matrix axes for the equatorial carbons are tilted slightly in the -z direction from the ideal locations along the x and y axes. The g-matrix suggests that the metal contribution is dz2 and the iron hyperfine matrix then can be used to estimate about 55% iron 3d and 34% axial carbon 2pz spin density. The spin density on the equatorial carbons then is mostly negative and due to spin polarization. 

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