SI Reactions

Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

Membrane material SiN Si Reaction channel width depth length 500 pm 550 pm 18 mm... 

In addition, two kinds of active centers are supposed on the catalyst surface Si (reaction with ROOH) and S2 (reaction with R02 )- The following kinetic scheme was proposed for the explanation of the critical phenomenon [274],... 

Sodium amide is a dehydrating agent. It is used in preparing sodium cyanide and hydrazine, and in many organic synthetic reactions such as Claisen condensations, alkylations of ketones and nitriles, and in ammonoly-sis reactions. 

Stability of Amatols. According to Ref 17a, p 183, the vacuum stability of 50/50 amatol is a little less than that of TNT at temps of 100 and 120°, there evidently being very si reaction betw TNT and AN at those temps. 

Figure 2.38 Schematic of the suspended-tube reactor (left and middle) and SEM (right) showing four suspended SiNx tubes connected to the Si reaction zone, Si slabs thermally linking the four tubes and a meandering Ti/Pt resistive heater/temperature sensor [72] (by courtesy of L. R. Arana).

Table 3.1. Gibbs free energy of formation of vanadium, chromium and manganese silicides257 and the first phase to grow in the Me-Si reaction couples...

G. Majni, M. Costato, F. Panini, G. Celotti. Thin-film compounds in planar Pt-Si reaction// J.Phys.Chem.Solids.- 1985.-V.46, No.5.-P.631-641. 

Ml) as Pd, Pt, Ni or Co, which form metal-rich silicides at low T, or whether they are such metals (M ) as V, Cr, Zr, Mo, Ta and W, which form disilicides as a first phase at high T (see Table 3) or a combination of both. For the latter, the subsequent reaction with Si depends on whether the low-T silicide-forming metal or the high-T disilicide-forming metal is in contact with the Si. Examples of the four Si reaction categories are shown schematically in Fig. 4. 

For the ethane and isobutane reactions the following values were obtained (in percentage of total) Rma 56%, fJabs 21%, and ffirecomb 23%, whilo for tetramethylsilane R b 36%, Rabs 12% and fBrecomb 52%. From this, the rate constant ratio for deactivation to insertion (fcd/ i) lor the (CHsl Si reaction is equal to ca. 1.8, the largest yet obtained. It is also seen that tetramethylsilane is a more efficient third body for the recombination of sulfur atoms than any of the hydrocarbons studied. 

The determination of isotopic abundance by means of an n,p) reaction induced by thermal neutrons has been described by Coon (16). Variations in the He content of helium gas depending on its source had been recorded and Coon was able to confirm these with gas obtained from wells and from air by means of the reaction He (n,p)H whose cross section for thermal neutrons is approximately 5,000 bams. A search for Si in natural silicon was conducted by Turkevich and Tomkins (WB). Theory had indicated that Si might be a beta-stable isotope and occur in natural silicon in small, undetected amounts. Neutron-irradiated quartz was examined radiochemically for 25-day half-life P , the daughter of Si formed by (ra,y) reactions on the sought isotope. However, only P , probably formed from impurities, was detected and assuming a cross section for the Si (n,y) Si reaction of 0.05 bams an upper limit of 4 x 10 % results for the abundance of Si in natural silicon. Subsequent work has shown Si to be an approximately 300-yr half-life beta emitter. 

Fig. 11 Scanning electron microscopy photos of microreactor produced by Jensen et al. for reforming of ammonia showing four freestanding SiN tubes, a suspended Si reaction zone with integrated thin-film platinum heater and temperature sensing resistor (TSR), and Si slabs wrapped around the four tubes. (From Ref.P l)...

---