Tungsten and Silicon

Two compounds are known in the tungsten-silicon system WsSi3 and WSia. 

PR By reaction of the elements in powder form in a protective atmosphere, like argon or vacuum at elevated temperature. Starting materials, their size, crystallinity, presence of defects, oxide films, and experimental conditions determine the reaction product, mechanism, and kinetics. 

A Tungsten silicides form a protective layer at the surface of tungsten and prevent 

CP Insoluble in water. Will be attacked by fluorine, chlorine, fiised alkalis, and HNO3-HF mixtures. Stable in air up to 900 °C. 

A Can be used in high-temperature thermocouples in combination with MoSi2 in 

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A general method for the separation of vanadium from arsenic, molybdenum, phosphorus, chromium, uranium, tungsten, and silicon, consists in precipitating these metals as their respective lead salts and digesting the precipitate with potassium carbonate, whereupon all the lead salts are decomposed with the exception of the lead vanadate.5... 

Use of these x-ray techniques is only applicable to films as thick as 1 to 3 microns, since the emitted x-rays come from this depth in a sample (as illustrated in Figure 14). For a 2000 A layer of tungsten on silicon, for example, we would clearly detect tungsten and silicon. However, there would be no... 

Finally, in table 6.4 some relevant properties of tungsten and silicon are listed. An important fact is that meta-stable j8-W has quite different properties than a-W. (Refer to chapter II about the occurrence of /3-W in CVD-W films). 

The hot fiber (wire) CVD process has been commercially used for 30 years to produce continuous sheath/core bicomponent boron/tungsten and silicon carbide/carbon fibers. Since they are continuous fibers, they are discussed in Chapter 3.3. More recently, this process was used to produce discontinuous, i.e., short, experimental sheath/core diamond/carbon fibers by depositing a thick diamond sheath on short pieces of a potentially carbon fiber. 

The technology of manufacturing sheath/core bicomponent boron/ tungsten, boron/carbon, silicon carbide/tungsten, and silicon carbide/ carbon fibers is 40 years old and the relationships between process variables, structures, and properties have been authoritatively described in important review articles. One article deals mainly with their preparation [33] another correlates process variables with structures [34], and one explores potential correlations between structures and properties [30]. 

Fig. IX.E. 1 Cryogenic target designed for E 813. The target is approximately 60 cm long with the deuterium vessel located above the hydrogen vessel. The tungsten and silicon detector arraysis a separate unit located in the vacuum between the two cryogenic vessels. The separating walls are milled to the shapes shown out of solid plates of aluminum.

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