Silicon reduction

In the past, all grades of refined ferromanganese were made by various modifications of multistep silicon reduction processes. Depending on the carbon content desired in the product, a manganese ore and lime mixture was allowed to react with the silicon in silicomanganese or low carbon silicomanganese in an open, electric-arc furnace. The equilibrium reaction is... 

Silicon Reduction. The preparation of ferrovanadium by the reduction of vanadium concentrates with ferrosiUcon has been used but not extensively. It involves a two-stage process in which technical-grade vanadium pentoxide, ferrosiUcon, lime, and fluorspar are heated in an electric furnace to reduce the oxide an iron alloy containing ca 30 wt % vanadium but undesirable amounts of siUcon is produced. The siUcon content of the alloy is then decreased by the addition of more V2O5 and lime to effect the extraction of most of the siUcon into the slag phase. An alternative process involves the... 

It is postulated that the mechanism of the silane-mediated reaction involves silane oxidative addition to nickel(O) followed by diene hydrometallation to afford the nickel -jr-allyl complex A-16. Insertion of the appendant aldehyde provides the nickel alkoxide B-12, which upon oxygen-silicon reductive elimination affords the silyl protected product 71c along with nickel(O). Silane oxidative addition to nickel(O) closes the catalytic cycle. In contrast, the Bu 2Al(acac)-mediated reaction is believed to involve a pathway initiated by oxidative coupling of the diene and... 

The silicon reduction process is not thermally self-sustaining and, therefore, is done in an electric arc furnace ... 

High-carbon ferrochromium alloys are made by the reduction of chromite ore with carbon in an arc furnace. On the other hand, low-carbon ferrochromium is obtained by silicon reduction of the ore. The carbon content of ferrochromium can be reduced further by heating high-carbon alloys with ground quartzite or by oxidation in vacuum and removal of carbon monoxide formed. Ferrochromium alloys are used in the manufacture of stainless steel. 

The following preparative method (of general utility) includes the reduction of niobium(V) fluoride with elements such as silicon, phosphorus, and boron,1 which yield highly volatile fluorides. Silicon reductions have been studied in greatest detail. Niobium(IV) fluoride can be prepared in good yield by the reaction described by the equation ... 

The first is the hydrogen reduction process which can proceed on any surface raised to a suitable temperature. The second is the silicon reduction process where silicon reduces WF6. The third process is similar to the first, but substitutes chlorine for fluorine. The final process is related to the WSi2 deposition studied earlier. It has been shown17 that depending on the deposition conditions, one can deposit either W, WSi2 or W5Si3 from these two reactants. 

Figure 14 Silicon reduction of WF6-thickness of tungsten versus deposition time.24 Reprinted by permission of the publisher. The Electrochemical Society, Inc.

Metallurgy. — The metals of most of the cerium group elements have been prepared, three general methods having been used t (1) fusion of the anhydrous halides with sodium, potassium, calcium, or aluminium (2) electrolysis of the fused chlorides or of a solution of the oxide in the molten fluoride (3) heating the oxides with magnesium, calcium, or silicon. Reduction with aluminium has also been tried, but it is not satisfactory except possibly for cerium itself. Electrolysis has been the most successful, the other methods usually giving at best an alloy. 

USE In ferrous metallurgy Ferroniobhim (produced by silicon reduction of columbite) is used to alloy stainless steels and metals for welding rods. In niobium base alloys lor high temps and nuclear reactions. Niobium has some use as a getter in electronic vacuum tubes. 

Dense tubular silicone - Reduction of geraniol to citronellol ... 

H. Tveit, M. Garcia, H. Delbeck, A.T. Haug, B. Saugestad, and I.J. Eikeland, "Water Leakages in Ferroalloy and Silicon Reduction Furnaces - Experience Gained from a Severe Accident in 2006," presented at the Silicon for the Chemical and Solar Industry IX, Oslo, Norway, (2006), 1-16. 

Crystalline silicon is a strong but brittle material. The introduction of porosity often lowers hardness, stiffiiess, and fracture strength (see handbook chapter Mechanical Properties of Porous Silicon ), and if the stmcture becomes too weak, it cannot often survive common material processing techniques without alteration. Examples include air drying (see handbook chapter Drying Techniques Applied to Porous Silicon ), reduction of particle size via communition (see handbook chapter Milling of Porous Silicon Microparticles ), and oxidation of layers (see handbook chapter Oxidation of Mesoporous Silicon ). The properties of electrochemically etched layers can depend not only on etch parameters but how the material was dried. The properties of microparticles can be sensitive to how they were milled. 

Figure 7.8.3 Evolution of the silicon reduction peak current density versus time after an addition of K2SiF. Working electrode Ag. T = 800°C...

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