Selenium alloy Silicon

Selenium is added up to 0.1% to silicon steels (2—4% Si) used in transformer cores to enhance the development of the secondary recrystallization texture which, in turn, improves the magnetic characteristics. Selenium alloying additions to the melt may be made as elemental Se, nickel—selenium, or ferroselenium. The recovery depends on the melting practice and method of addition. Normally, it is in the range of 66%, but may be as high as 90%. 

Platinum can be alloyed with many elements at elevated temperatures. Such elements include other noble metals, as well as, cobalt, selenium, silicon, and arsenic and nonmetals like carbon, phosphorus, and sulfur. 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

The arsenomolybdenum blue method was applied for determination of arsenic in biological materials [7,17,60,61], plants [24], water [24,62-64], silicates [20], petroleum products, organic compounds [24,65], steel [15,66], antimony [2,3,67,68], antimony and gallium chlorides [69], bismuth [18], zinc [70], zinc and lead concentrates [71], tungsten [72], copper alloys [73], gold and platinum [34], silicon [74], selenium [75], and boron [76]. 

A wide variety of inorganic materials have been used to precipitate or collect trace metals from solution. The most direct approach is a cementation process, which is one that removes the trace pollutants from solution by reduction with a metal and plating onto that metal surface. Although this process may be slow, the filtration is usually quick, since decantation is often sufficient. Finely divided cadmium extracts copper, selenium, and mercury from nitric and sulfuric acid solutions (66). When copper was used to preconcentrate mercury from water or biological fluids prior to atomic absorption analysis, the detection limit was 1-2 X 10 g (67, 68). Iron (69), zinc (70), and tungsten (71), as metals, have also been used to obtain a deposit of several trace metals from aqueous systems as dilute as 10 ppb for subsequent analysis. Elemental tellurium can be produced in solution by reduction using tin(II) chloride or sulfur dioxide, and coprecipitates silver (72) and selenium (73). Granulated silicon-metal alloys were used to remove metal ions from water and brine by reduction as well (74, 75). 

RBS has also been used to characterize palladium and tin catalysts on polyetherimide surfaces [229], titanium nitride thin films [230], silicon oxynitride films [231], and silicon nitride films [232]. and to study the laser mixing of Cu-Au -Cu and Cu - W - Cu thin alloy films on Si3N4 substrates [233], and the annealing behavior of GaAs after implantation with selenium [234]. 

The control of the second critical step, crystallization of the amorphous alloy, is the focus of the following discussion. Iron-silicon and iron-aluminum systems are discussed. The critical lengthscales in the iron-aluminum and iron-silicon systems are much larger than that observed in the molybdenum-selenium systems. By critical lengthscale, we refer to the thickness of the repeat unit in the multilayer below which the multilayer evolves completely into an amorphous material without the nucleation of any crystalline phase. The samples discussed are all layered on a lengthscale which is less than this critical value. That is, they evolve from a layered initial state, through a distinct amorphous intermediate, to a crystalline compound. 

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