Composites silicides

AES has found applications in measuring semiconductor composition, oxide film composition, silicides, metallization, particle analysis and the effects of surface cleaning. AES measurements are made inahigh vacuum environment(10 10 °torr)... 

Nb-Aluminides, precious metal and exotic aluminides. Laves phases and in-situ composites, silicides, and beryllide intermetallics. Given previous excellent reviews of the oxidation of intermetallics (e.g. Aitken, 1967 Doychak, 1994 Meier, 1996 Welsch et al., 1996), these sections emphasize the findings of recent studies. Areas in need of additional research, and issues that have already been well explored or are unlikely to yield fruitful results, are noted. 

To return to die problem of die vaporization of die tantalum silicides, which could be transported as the tetraiodide of each element, but not as the elementary species. From these data it can be concluded that whatever die starting point in the composition range, the composition of the surface phase will tend towards Tag Sis, which is die most nearly congruently vaporizing composition. 

Kara, T., Miyamato, T., Hagiwara, H., Bromley, E., and Harshbarger, W., Composition of Tungsten Silicide Films Deposited by Dichlorosilane Reduction of Tungsten Hexafluoride, /. Electrochem. Soc., 137(9) 2955-2959 (Sept. 1990)... 

This has been used, for instance, to follow the formation of palladium silicide in a silicon wafer for thicknesses up to 6nm [Vanleerdam et al., 1990]. More recently, investigation of the tails in LEIS has been used as a tool for high resolution nondestructive in-depth composition analysis of ultrathin layers [Brongersma et al., 2003] and shallow interfaces [Janssen et al., 2004]. 

A proportion of finely divided aluminium is often added to TNT explosives in order to increase the power. As aluminium has also a sensitising effect, it is particularly useful in waterproofed compositions. Another power producing additive which is sometimes employed in large diameter charges where its slow reaction is of less disadvantage is calcium silicide. Care must be taken with this material, however, to ensure that it does not lead to sensitiveness to friction and impact. 

Germanides and Silicides. A crystal-structure determination of the material previously formulated as NbjGej has shown that the actual composition is NbioGe7. The structures of NbFeGe, TaMnGe, and TaMnSi have also been investigated. ... 

Tungsten also forms hard, crystalline refractory borides, such as WB2, W2B and WB when heated with boron in an electric furnace. Tungsten also forms a group of silicides, hard refractory compounds of compositions WSi2, WSis and W2Si3. These silicides are attacked by hydrofluoric-nitric acid mixture or by fused alkalies. 

Fig. 4.52 Atom-probe compositional analysis of the polycrystalline silicide layers shown in Fig. 4.51. The slope gives the composition to be WSi2.

LSt has been used extensively abroad as igniting charge for LA and to some extent in the US as an ingredient of priming compositions (Ref 24, p 7-12). On p 7-18 of Ref 18, it is stated that LSt has been used in electric primers and the following compn is used for that purpose LSt 39.5, Ba nitrate 44.4, Ca silicide 14.1, carbon black 1.0 gum arabic 1.0%... 

The structure of type I hydrates is repeated in melanophlogite 61), and that of hydrates of types I and II is repeated in clathrate silicides or germa-nides of Na, K, Rb, or Cs 59, 60). The alkali metal atoms are enclosed in cages of Si or Ge atoms and are thereby protected from attack by atmospheric oxygen. The limiting composition is 8G 46Si or 24G-136Si, or the same with Si replaced by Ge however, neither of these compositions is reached since some voids do not contain an alkali metal atom. The unit cells vary as follows with the bond distances between pairs of vertices in the polyhedra. 

In earlier work, it was found for borides, silicides and nitrides that specific activity, expressed as total rate of methane consumption per unit surface area, plummeted with increasing surface area of the catalyst samples.1718 The same relationship was also found for transition metals carbides (Figure 16.4). It should be noted the dependence of specific activity on surface area rather than catalyst composition is unusual for heterogeneous catalytic reactions. In addition, it can be found that the reaction order in the oxidant is perceptibly in excess of 1 (Tables 16.8 and 16.9). Such an order is hard to explain in terms of common mechanism schemes for heterogeneous catalytic oxidative reactions. 

The Badische AniKn- und Soda-Fabrik prepared a nitride of undetermined composition by heating a mixture of silica and carbon in an atm. of nitrogen. The reaction proceeds at a relatively low temp, if a hydroxide or salt of a metal be added. The product contains silicon nitride mixed with the nitride of the metal. The Badische Anilin- und Soda-Fabrik also removed many of the impurities—iron, carbon, silicates, carbides, silicides, and phosphides—by treatment with acids or mild oxidizing agents which do not affect the silicon nitride. A. S. Larsen and O. J. Storm prepared the nitride by the action of nitrogen on molten silicides—e.g. ferrosilicon. 

Several fiber types have been mentioned so far, and several other types have been neglected that have been worked on over the past few years. Some of those not discussed may become important fibers for reinforcement in the years ahead. To date though, they have not been available in sufficient quantity for thorough evaluation in composite specimens. Included in this group are boron carbide, spinel, polycrystalline alumina and silica, titanium diboride, and miscellaneous silicides and intermetallics. Ten years from now as we look back on the 70s we no doubt will have an entirely different view of some of these materials. 

Large grains, low amounts of impurities and defects and solid solutions Large, needle like grains, composites with SiC, or refractory silicides Large, needle-like grains, composites with SiC, or refractory silicides... 

Klemm H, Tangermann K, Reich T, Herrmann M, Schubert C, Hermel W (1995) High-Temperature Properties of Silicon Nitride Molybdenum Silicide Composites. In Bellosi A (ed) Fourth Europ Ceramics, Vol 4, Grupp Editoriale faenca Editrice, Faenza, p 233... 

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