Giving Silicides

Higher chlorides, Si2Cle to Si6Cl,4 (highly branched - some cyclic) are formed from SiCU plus Si or a silicide or by amine catalysed disproportionations of Si2Cl,5, etc. Partial hydrolysis gives oxide chlorides, e.g. CUSiOSiCla. SiCU is used for preparation of silicones. 

After 60 minutes of aimealing, all the Pt has reacted to fonn Pt2Si. Almost immediately thereafter the reaction between Pt2Si and Si to fonn PtSi starts and after a fiirther 60 minutes all the Pt2Si has reacted, resulting in a stable PtSi film on Si. The data of silicide thickness versus ramped temperature can be plotted in reduced fonn in an Arrhenius-like plot to give the activation energy [6, 14] ... 

More than half of the elements in the Periodic Table react with silicon to form one or more silicides. The refractory metal and noble metal silicides ate used in the electronics industry. Silicon and ferrosilicon alloys have a wide range of applications in the iron and steel industries where they are used as inoculants to give significantly improved mechanical properties. Ferrosilicon alloys are also used as deoxidizers and as an economical source of silicon for steel and iron. 

The theoretical studies " have been focused on TiSi2. Some attempts, with use of high-symmetry crystal structures, have been made to understand some of the other titanium silicides. This paper deals vith Ti,5Si.3. Because of the crucial interplay between structure and bonding we have studied the proposed stable low-symmetry crystal structure. This will give a better picture of the electronic structure and the bonding properties in this system. An investigation of seven members in the Ti-Si system will be presented in a future publication. ... 

Triferric tetroxide gives rise to a highly violent detonation when it was heated with calcium silicide combined with aluminium and sodium nitrate. 

Barium sulphate is not a strong oxidant yet it can give rise to a very violent thermite reaction when it is heated in the presence of a very electropositive metal. This applies to aluminium for which an accident was described. In addition, there was an accident which involved a mixture of this sulphate with red phosphorus although the latter had been previously treated with potassium nitrate and calcium silicide. 

F. B. Clay R. A. Sahlin, 49, 14326 (1955) Igniter comps for tracer projectiles which include a Ca silicide fuel as a partial or complete replacement for Mg burn in such a manner as to give a dim or invisible trace to a min distance of 25 yds a bright properly colored trace at greater distances. A typical igniter comp is Sr02 78, Ba02 4,... 

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.

Polvere "Canned . SeeCannel Explosives in Vol 2, p C25 R of this Encycl Romite galleria Romite cava, for use in open work have been manufd by Polverificio Stacchini. They are listed in Ref 39, p 32 w/o giving their compn Sabulite AN 78.2, Ca silicide I3.8 St TNT (or TNN or DNB) 8.0% (Ref 58, p 376)... 

If the initial solid substance is a chemical compound (an intermetallic, a silicide, etc), then its oxidation can proceed via two different mechanisms, depending on the experimental conditions. Two oxides are formed in the severe oxidation (combustion) usually resulting in the disintegration of the compact solid phase. In the partial (soft) oxidation the chemical compound undergoes a partial decomposition giving another chemical compound of the same class and an oxide. 

While interactions of alkali metals or magnesium with elemental silicon and germanium (or their oxides) can give various silicides or germanides, most of these products do not contain true anions and some are semiconductors. However, in Li12Si7 there are Si5 rings and trigonal planar Si-centered Si, units in the lattice. 

At elevated temperatures it combines with most nonmetals. With oxygen it gives V205 contaminated with lower oxides, and with nitrogen the interstitial nitride VN. Arsenides, silicides, carbides, and other such compounds, many of which are interstitial and nonstoichiometric, are also obtained by direct reaction of the elements. 

A variety of surface reactions have been observed with other metals on a-Si H (Nemanich 1984). For example, a similar silicide is formed with platinum and nickel at 200 °C and with chromium at 400 °C. Aluminum and gold form intermixed phases at low temperature, but do not form silicides. Instead both metals promote low temperature crystallization of the a-Si H film. Dendritic crystallization occurs at 200 °C at a gold contact, giving a very non-uniform interface, and aluminum causes crystallization at 250 C. The resulting Schottky contact for gold is surprisingly ideal, but is very poor for aluminum. 

A totally different but nevertheless exciting field is the solid state chemistry of silicides and of Zintl anions aimed on the optimization of the physical properties (e.g. conductivity) and their derivatization to give molecular species. 

As can be concluded from Fig. 4, the initial reactivity of the surface of Sited, is very high The relevant copper species present, possibly copper chlorides, which can easily form copper-silicidic phases by reaction with silicon, can easily attack the whole of the surface and react with surface silicon, resulting in Cu-Si species and finally metallic copper, e g, [26]. Due to this very fast formation of catalytically active Cu-Si species and of precursors thereof, the reaction becomes very fast already after a short time. But, on the other hand, this overall attack on the silicon surface gives copper species the possibility to be deposited practically over the whole of the silicon grain This means in terms of our model of catalytically active Cu-Si surface species, explained in the first section of this paper, that there is a lack of still free silicon surface area, which is needed in order to form the active "two-dimensional" Cu-Si species. The surface is simply blocked by thick copper-containing layers. As consequence, the reaction goes down after a short time and the contact mass reaches only low stationary activity. 

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