Sulfides and Oxysulfides

The main sulfide phosphors are the group II-V ones based on high purity zinc and cadmium sulfides activated by dopants, primarily using copper and silver but also manganese, gold and rare earths. The nature and concentration of the activator, the composition of the flux and the firing conditions, normally in furnaces at 800-1500 °C, influence the luminescent properties. 

Zinc sulfides activated by copper are widely available, mass-produced, low cost materials. Their emission can be tuned over a wide range, from short UV to visible and so the phosphors work in most commonly encountered lighting conditions. However, the green emitting ZnS Cu phosphors, together with copper activated zinc-cadmium sulfide (Zn,Cd)S Cu, are the ones most often used in industrial apphcations. The different versions of ZnS Ag phosphors are exclusively used industrially to obtain a blue emission. Another very important industrial phosphor is the yellow to orange ZnS Mn, which finds application in monochromatic displays. ZnS Tb is a very efficient green phosphor. 

The alkaline earth sulfides activated with rare earths are also of importance. They are suitable for use in CRTs because of the linear dependence of their brightness on applied current over a wide range. For example, MgS activated with 0.004% Eu has a very bright maximum emission at 600 nm. 

The alkaline earth sulfides are mostly used because of their long afterglow properties. (Ca, Sr)S Bi is blue, CaS BE+ is violet and Ca S Eu, Tm is red. SrS Ce + has a maximum at 483 nm and is a very useful blue phosphor. 

The main emission lines of Y OjSiEu are at 565 and 627 mn but by increasing the Eu content to 4%, a shift in tlie intensity of the longer wavelength emission occurs and a deep red is produced, eminently suitable for colour CRT. 

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Tellurium forms many sulfides and oxysulfides. The metal reacts with sulfides of zinc, cadmium, or mercury, forming tellurium sulfide ... 

Rare-earth nanomaterials find numerous applications as phosphors, catalysts, permanent magnets, fuel cell electrodes and electrolytes, hard alloys, and superconductors. Yan and coauthors focus on inorganic non-metallic rare-earth nanomaterials prepared using chemical synthesis routes, more specifically, prepared via various solution-based routes. Recent discoveries in s)mthesis and characterization of properties of rare-earth nanomaterials are systematically reviewed. The authors begin with ceria and other rare-earth oxides, and then move to oxysalts, halides, sulfides, and oxysulfides. In addition to comprehensive description of s)mthesis routes that lead to a variety of nanoforms of these interesting materials, the authors pay special attention to summarizing most important properties and their relationships to peculiar structural features of nanomaterials s)mthesized over the last 10-15 years. 

The sulfur tolerance of these anodes is primarily dictated by the thermodynamics of ceria sulfide and oxysulfide formation, as the sulfur concentration required for CuaS formation is significantly higher [45]. Kim et al. demonstrated that stable operation could be achieved if the sulfur level in the fuel is reduced to 100 ppmv S as thiophene in 5 mol% n-CioH22 - this is below the concentration predicted from thermodynamics for Cc202S formation. This study was followed by work of He et al. who demonstrated stable operation up to 450 ppmv H2S in H2 [46], significantly higher than the tolerance levels reported for Ni-based anodes [47]. 

Row85] Rowe, R.G. and Koch, E.F., Rapidly SoUdified Titanium Alloys Containing Cerium Sulfide and Oxysulfide Dispersions, in Rapidly Solidified Materials, PW. Lee and R.S. Carbonara, Ed., American Society for Metals, 1985, p. 115-120... 

Using these K values calculated for cerium oxides, sulfides, and oxysulfides, Wilson et al. (1974, 1976) have constructed an inclusion precipitation diagram for the Fe-Ce-O-S system (fig. 4), where hct, ho and hs represent the Henrian activities of cerium, oxygen and sulfur, respectively. This composite precipitation diagram gives a clear, qualitative picture of the conditions of phase formations and transformations. 

If Sj is > 10 Oi but < 100 Oi, the initial melt composition is located within the oxysulfide field, for example, at F. On the addition of rare earths, oxysulfide will precipitate and the melt composition will move from F towards G. When the oxygen content has been reduced to G, both sulfide and oxysulfide will separate until the final required sulfur level is reached. 

Rare earths form extremely stable sulfides and oxysulfides, as described above. Free energies of formation of the nitrides suggest that Al and rare earths have an almost similar behavior. No problems related to nitride formation have been encountered in the past with Al at levels of typical killed steels, therefore, no difficulty was anticipated with rare earths. This assumption has been substantiated by several investigators. In view of the low free energy of formation of rare earth carbides, it is unlikely that carbide formation would be a problem. 

Carbon disulfide is essentially unreactive with water at room temperature, but above about 150°C in the vapor phase some reaction occurs forming carbonyl sulfide (carbon oxysulfide) [463-58-1] and hydrogen sulfide [7783-06-4]. Carbonyl sulfide is an intermediate in the hydrolysis reaction ... 

Figure 6. Free energy of formation of some sulfides and REM oxysulfides at...

The method described is adapted from the procedures of Kym 3 and Engelhardt, Latschinoff, and Malyscheff.4 Thio-benzoic acid has been prepared by the reaction of benzoyl chloride with potassium sulfide,4 hydrogen sulfide in pyridine,6 6 and magnesium bromide hydrosulfide.7 It is formed from dibenzoyl disulfide with potassium hydrosulfide,4 potassium hydroxide,4 8 and ammonia.9 It is also formed from dibenzoyl sulfide, from phenyl benzoate, and from benzoic anhydride with alcoholic potassium hydrosulfide.4 It has been obtained from dibenzoyl sulfide and hydrogen sulfide,10 carbon oxysulfide and phenyl-magnesium bromide,11 12 dibenzyl disulfide and sodium ethoxide,13 benzyl chloride and sulfur in the presence of potassium hydroxide,14 and benzylthiosulfuric acid and alkali.18 16... 

Although dithiazolones 8 (X = Y = S Z = O) are more stable than oxathiazolones, under more drastic conditions they slowly decompose to give nitrile sulfides and carbon oxysulfide <1996CHEC-II(4)506>. In a reported example, more than 50 h in refluxing mesitylene (ca. 164 °C) are required for decomposition (five to six half-lives) <2002ARK121>. Trapping reactions of these nitrile sulfides are discussed later (see Section 6.04.5.6). In the absence of a trapping dipolarophile, the thermolysis products are nitriles and sulfur. 

P/Al and AIPO4 samples are unreactive with H2S at temperatures up to 723°C. Chadwick et al. (60) found no evidence of formation of sulfided phosphorus from XPS measurements. These results indicate that the phosphorus oxo-species do not transform into phosphorus sulfides or oxysulfides (Fig. 2) during the normal conditions of the hydrotreating reactions. 

Figure 5 shows the HP-TPR profiles. Sulfur in the presulfided catalyst begins to react with H2 at 150 °C to yield H2S, which immediately reacts with the metal oxysulfides to form the sulfides and H2O. The activation reactions appear to complete by 300 °C. It should be noted that some H2S slipped out, in this case approximately 7% of the stoechiometry. 

Nearly all the sulfur dioxide entering the process was converted selectively to hydrogen sulfide between 660 and 760 °C. The process was also applied to convert sulfur dioxide to sulfur at lower reaction temperatures. As shown in Figure 6, when 100% of the sulfur dioxide is converted, 90% reacts to form elemental sulfur while 10% yields different by-products such as hydrogen sulfide, carbon oxysulfide, carbon disulfide, etc. Nearly 100% selectivity to sulfur can be obtained at lower conversions corresponding to lower reaction temperatures. Lower temperatures caused lower conversions since the maximum contact time,... 

The method is unaffected by a fivefold excess of hydrogen sulfide and of most mercaptans (phenylmercaptan, however, interferes). If carbon oxysulfide is present, the method must be modified. 

In all primary lithium cells, the negative electrode is made of metallic lithium. Thus, different types of lithium cells differ in the positive electrode material and in the type of electrolyte. A variety of oxidant materials was offered as the active material of the positive electrode. These included different oxides, sulfides, selenides, oxysulfides, oxychlorides, and some other substances perfluorinated carbon and sulfur. However, only a small number of electrochemical systems in the cells actually reached the industrial production stage. The electrochemical systems of the cells produced industrially are given in Table 11.1. This Table also presents the values of open circuit voltage (OCV) of these cells and the theoretical values of their energy density. 

Kinetic data can only be interpreted meaningfully if the catalyst contains of a single phase. However, classically prepared tungsten catalysts are only partially sulfided and are actually a mixture of W( ) oxysulfides and WS2 [4]. In such a case, it is difficult to isolate... 

When this decomposition takes place in the presence of elemental sulfur, there is subsequent formation of carbonyl sulfide (carbon oxysulfide) and this gas will blacken lead acetate paper. 

Rare earth elements and sulfur combine to form a wide range of compounds as sulfides or oxysulfides Among them, sesquisulfides appeared to have the best potential as far as color is concerned (Table 4—1). We gave most of our attention to cerium sulfide, which was the most promising in terms of color intensity and purity. 

The Colour Index (Cl 77975) describes Griffith s zinc white as zinc oxide sulfide ( zinc oxysulfide ). It was produced by precipitating a zinc solution with barium sulfide and calcining the precipitate (recipe according to Bersch, 1901). However, other... 

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