Sulfide layer

Inject a filming amine to provide a protective barrier that will prevent cyanide from contacting the iron sulfide layer. 

The high resistivity of Inconel 600 (11 OjtI 0 8 Dm) demanded the application of this material as a composite with a central aluminum core. The aluminum was totally enclosed in Inconel 600 so that the Inconel was only exposed to sulfur and polysulfides. In a test over more than three years, cells with a composite current collector of this kind suffered from a high capacity decline. Post-test analysis showed that Inconel sustained polysulfide attack with the formation of a duplex nickel and chromium sulfide layer on the current collector surface. 

On the basis of our theoretical considerations and preliminary experimental work, it is hoped that fast processes of charge carriers will become directly measurable in functioning photoelectrochemical cells, Typical semiconductor electrodes are not the only systems accessible to potential-dependent microwave transient measurements. This technique may also be applied to the interfacial processes of semimetals (metals with energy gaps) or thin oxide or sulfide layers on ordinary metal electrodes. 

The properties of anodic layers of HgS formed on mercury in sulfide solutions have been investigated in comparison with anodic sulfide layers of cadmium and bismuth. Also, the electrochemistry of mercury electrodes in aqueous selenite solutions has been studied (see Sect. 3.2.1). The problem with the presence of several cathodic stripping peaks for HgSe in acidic Se(IV) solutions has been addressed using various voltammetric techniques at a hanging-mercury-drop electrode [119]. 

Fig. 4.9 Schematic illustration of the electrosynthesis procedure using a sulfur-modified gold electrode and alternating exposure to indium- and sulfide ion containing aqueous baths, (a) A polycrystalline gold surface is first modified with a sulfur layer, (b) Indium is plated onto this layer forming indium sulfide, (c) Indium continues to deposit atop the indium sulfide layer, (d) Transfer back to a sulfide ion containing bath results in the suMdization of the residual indium sites. (Reprinted from [95], Copyright 2009, with permission from Elsevier)...

An interesting idea has been to prepare the photosensitive electrode on site having the liquid play the dual role of a medium for anodic film growth on a metal electrode and a potential-determining redox electrolyte in the electrochemical solar cell. Such integration of the preparation process with PEC realization was demonstrated initially by Miller and Heller [86], who showed that photosensitive sulfide layers could be grown on bismuth and cadmium electrodes in solutions of sodium polysulfide and then used in situ as photoanodes driving the... 

A zinc sulfide layer in a CdSe/ZnS/CdSe quantum system structure has also been grown by SILAR from ZnO and sulfur precursors in octadecane.72... 

The growth mechanism for the IF-MS2 (M = Mo,W) materials by the sulfidi-zation of the respective oxide nanoparticles has been studied in detail (12, 31). The growth mechanism is schematically illustrated in Fig. 4 (31a). Here oxide nanoparticles are sulfidized on the surface at temperatures between 800 and 950 °C in an almost instantaneous reaction. Once the first sulfide layer enfolds the oxide nanoparticle its surface is completely passivated, and hence sintering of the nanoparticles is avoided. In the next step, which may last a few minutes, reduction of the oxide nanoparticle core by hydrogen takes place. In the third step, which is rather slow and may take a few hours, depending on the size of the nanoparticles... 

Measurements of the optical properties in this range of wavelengths can probe the fundamental electronic transitions in these nanostructures. Some of the aforementioned effects have in fact been experimentally revealed in this series of experiments (90). As mentioned above, the IF nanoparticles in this study were prepared by a careful sulfidization of oxide nanoparticles. Briefly, the reaction starts on the surface of the oxide nanoparticle and proceeds inward, and hence the number of closed (fullerene-like) sulfide layers can be controlled quite accurately during the reaction. Also, the deeper the sulfide layer in the nanoparticle, the smaller is its radius and the larger is the strain in the nanostructure. Once available in sufficient quantities, the absorption spectra of thin films of the fullerene-like particles and nanotubes were measured at various temperatures (4-300 K). The excitonic nature of the absorption of the nanoparticles was established, which is a manifestation of the semiconducting nature of the material. Furthermore, a clear red shift in the ex-citon energy, which increased with the number of sulfide layers of the nanoparticles, was also observed (see Fig. 21). The temperature dependence of the exciton... 

Figure 11.28 shows the rhenium and osmium isotopic compositions of black shales and sulfide ores from the Yukon Territory (Horan et al., 1994). The black shale and sulfide layers are approximately isochronous. The superimposed reference isochrons bracket the depositional age of the enclosing shales. One reference line represents the minimum age (367 Ma) with an initial ( Os/ Os)q ratio of one, consistent with the mantle isotopic composition at that age (see later). The other reference isochron is drawn for a maximum age of 380 Ma, with ( 870s/ 860s)o = 12 (the maximum value measured in terrigenous sediments). Further examples of application of Re-Os dating of sediments can be found in Ravizza and Turekian (1989). 

Horan M. E, Morgan J. W, Grauch R. I., Coveney R. M. Jr., Murowchick J. B., and Hulbert L. J. (1994). Rhenium and osmium isotopes in black shales and Ni-Mo-PGE-rich sulfide layers, Yukon Territory, Canada, and Hunan and Guizhou provinces, China. Geochim. Cosmochim. Acta, 58 257-265. 

The corrosion behavior and dissolution mechanism of nickel in acid solutions with hydrogen sulfide (H2S) was studied. It was found that the dissolution of nickel is influenced by both the nickel sulfide layer formed on the electrode surface and the acceleration effect of H2S [56]. 

Traces of sulfides were determined by CSV at pH 10 in the presence of cobalt(II) ions. Cobalt sulfide was accumulated at —0.5 V (versus SCE), probably in the form of colloidal particles occluded into the mercury sulfide layer [73]. In the cathodic scan, CoS catalyzed evolution of hydrogen, which was reflected in the current peak at about —1.6 V. 

The intercalation compound formed has layers of a variable number of lithium ions between sulfide layers as given in Figure 6.11. 

Matte smelting involves roasting the concentrate with lime and recycled converter slag at about 1300 °C to form a slag of molten oxides of iron, silicon, and other impurities, and an immiscible matte or molten sulfide layer, which contains CU2S along with some FeS. 

Sol-gel techniques can be used to produce thin layers, as described in Section 19.1. For example, cadmium sulfide layers for photocells are easily made by spraying an ammoniacal solution of cadmium chloride and thiourea (which hydrolyzes to give sulfide ion) onto a substrate surface and baking the resulting CdS film at up to 500 °C ... 

All the three MoS-L compounds exhibit a distinct weight loss at about 200 °C and two small ones at about 310 °C and 550 °C, respectively. The former two are attributable to the decomposition of the surfactant cations in the mesostructured sulfides and the latter one is probably associated with the loss of sulfur from the solid compounds. The total weight loss varies from 67% to 50% depending on the chain length of the surfactant cations intercalated in the sulfide layers. 

Figure 3. Schematic representation of the structure of M0S-L-I6C with the surfactant cations interdigitated (left) and being in the form of double layers (right) between the sulfide layers.

The IR spectra for MoS-L-14C and MoS-L-12C are essentially the same as that for MoS-L-16C, confirming that the three mesostructured compounds possess similar structural features, that is, the surfactant cations are intercalated between identical molybdenum sulfide layers. 

They reasoned that in the vicinity of a silver sulfide speck the conduction band is bent downward and photoelectrons could reach the surface of the crystal more easily, and hence more readily form surface image. However, the thickness of the silver sulfide layer in their experiments was about 4 pm, which far exceeds that of any sensitivity center on emulsion grains. The relevance of their observation to S-sensitization of emulsions is doubtful. Starbov (147) found no evidence of change in the surface potential when either the (111) or the (200) surface of an evaporated silver bromide layer was sulfur-sensitized. 

For determing the concentration of hydrogen sulfide in the product gas, a Gow-Mac thermal conductivity cell (Model 10-952) was used. The cell was equipped with four matched pairs of AuW filaments, especially used because of their resistance to corrosion from the hydrogen sulfide. Layers of styrofoam were used to insulate the cell from changes in ambient temperature. This detector was found to be very sensitive to changes in the flow-rate. 

The formation of zinc phosphate on topmost surface and chemisorbed iron sulfide layer close to the metal substrate was observed (Glaeser et al., 1993 Jahanmir, 1987). 

It has been shown from corrosion studies (97, 98) that bulk sulfide formation involves metal cation diffusion through the sulfide layer to the surface with the formation of a new metal sulfide layer on the outer surface beyond the original metal. Apparently the formation of multilayer sulfides occurs slowly at room temperature and at Ph2s — 1 atm, cation diffusion through the sulfide layer controlling the rate (9, 96). Presumably this step would also be rate limiting at higher temperatures and at H2S concentrations as low as 10-100 ppm. However, in most catalytic processes H2S concentrations are below those needed for bulk sulfide formation. 

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