Silane pyrolysis

Also in 1992 Becerra and Walsh suggested that the increase in the rate of silane loss in the 3 to 30% conversion middle stage of silane pyrolysis is due to the chain process (equation 32) in which the chemically activated silylene insertion product gives rise to a silylsilylene that can consume another silane molecule64. 

When a heterogeneous reaction is considered, the partial pressures included in the "Law of Mass Action," Equation (1), are only those for the gaseous reactants. For example, when silicon is deposited on a surface due to silane pyrolysis, we have... 

The objective of this work was to study the influence of Ge, B, and P doing on the properties of nanostructed silicon films grown via silane pyrolysis. 

H. K. Moffat, K. F. Jensen, and R. W. Cart J. Phys. Chem., 96, 7695 (1992). Estimation of Arrhenius Parameters for the 1,1-Elimination of H2 from Si2H and the Role of Chemically Aaivated Disilane in Silane Pyrolysis. 

Szegd G (1939) Orthogonal polynomials. American Mathematical Society, New York Talukdar SS, Swihart MT (2004) Aerosol dynamics modeUng of silicon nanoparticle formation during silane pyrolysis a comparison of three solution methods. Aerosol Sci 35 889-908 Tamamidis P, Zhang G, Assanis DN (1996) Comptirison of pressure-based and artificial compressibility methods for solving 3D steady incompressible viscous flows. J Comput Phys 124 1-13... 

Petersen EL, Crofton MW Measurements of high-temperature silane pyrolysis using SiH4 IR emission and SiH2 laser absorption, J Phys Chem A 107 10988—10995, 2003. 

Polytitanosiloxane (PTS) polymers containing Si—O—Ti linkages have also been synthesized through hydrolysis—polycondensation or hydrolysis—polycondensation—pyrolysis reactions involving clear precursor sol solutions consisting of monomeric silanes, TYZOR TET, methanol, water, and hydrochloric acid (Fig. 2). These PTS polymers could be used to form excellent corrosion protection coatings on aluminum substrates (171). 

Turning now to other types of ceramic fibre, the most important material made by pyrolysis of organic polymer precursors is silicon carbide fibre. This is commonly made from a poly(diorgano)silane precursor, as described in detail by Riedel (1996) and more concisely by Chawla (1998). Silicon nitride fibres are also made by this sort of approach. Much of this work originates in Japan, where Yajima (1976) was a notable pioneer. 

The first type of polycarbosilane synthesized by using ADMET methodology was a poly[carbo(dimethyl)silane].14c Linear poly(carbosilanes) are an important class of silicon-containing polymers due to their thermal, electronic, and optical properties.41 They are also ceramic precursors to silicon carbide after pyrolysis. ADMET opens up a new route to synthesize poly(carbosilanes), one that avoids many of the limitations found in earlier synthetic methods.41... 

Barton and co-workers" performed flash vacuum pyrolysis (FVP) on trimethyl-silylvinylmethylchlorosilane (30), resulting in the production of trimethylchlorosi-lane (30%), trimethylvinylsilane (11.5%), and most interestingly, ethynylmethyl-silane (34, 11.9%). A proposed mechanism for the synthesis of 34 (Scheme 10) begins with the lo.ss of trimethylchlorosilane to form silylene 31, which can rearrange either to silaallene 32 or to silirene 33, both of which can lead to the isolated ethynylsilane. 

Matrix IR spectra of various silenes are important analytical features and allow detection of these intermediates in very complex reaction mixtures. Thus, the vibrational frequencies of Me2Si=CH2 were used in the study of the pyrolysis mechanism of allyltrimethylsilane [120] (Mal tsev et al., 1983). It was found that two pathways occur simultaneously for this reaction (Scheme 6). On the one hand, thermal destruction of the silane [120] results in formation of propylene and silene [117] (retroene reaction) on the other hand, homolytic cleavage of the Si—C bond leads to the generation of free allyl and trimethylsilyl radicals. While both the silene [117] and allyl radical [115] were stabilized and detected in the argon matrix, the radical SiMc3 was unstable under the pyrolysis conditions and decomposed to form low-molecular products. 

Nowadays silenes are well-known intermediates. A number of studies have been carried out to obtain more complex molecules having Si=C double bonds. Thus, an attempt has been made to generate and stabilize in a matrix 1,1-dimethyl-l-silabuta-l,3-diene [125], which can be formed as a primary product of pyrolysis of diallyldimethylsilane [126] (Korolev et al., 1985). However, when thermolysis was carried out at 750-800°C the absorptions of only two stable molecules, propene and 1,1-dimethylsilacyclobut-2-ene [127], were observed in the matrix IR spectra of the reaction products. At temperatures above 800°C both silane [126] and silacyclobutene [127] gave low-molecular hydrocarbons, methane, acetylene, ethylene and methylacetylene. A comparison of relative intensities of the IR... 

Phenylisosilacyanide is produced either by irradiation of triazidophenyl-silane in matrix isolation or by pyrolysis followed by trapping in noble gas matrix (Eq. 3). The reaction with /-butanol leads to the expected product6 ... 

The total energy, the structure, and the ionization pattern of the more stable phenyl derivative have been calculated.52,33 The controlled explosion of triazide(phenyl)silane in a flash-pyrolysis apparatus under approximately unimolecular conditions (p = 10-3 Pa, c = 10 2 3 mil/) can be carried out without danger.52,53... 

The growth rate of silicon crystals by either MBE or CVD is relatively slow, and so there is ample time for adsorbed atoms and molecules to diffuse to energetically more favorable sites. Experimental rates of diffusion of silicon on silicon and the activation barriers, however, are not known well. Experimental estimates of the activation barrier for silicon atoms diffusing on the Si(lll) surface have ranged from 58 kcal/mole when the pyrolysis of silane is used to produce surface silicon atoms , to 4.6 kcal/mole for the direct deposition of silicon atoms under ultrahigh vacuum Furthermore, a comparison of these... 

Other routes include the direct method using 1,4-dichlorobutane (58MI12000) and, remarkably, the flow pyrolysis of silane and THF over alumina (Scheme 149) (59DOKt 128)121). 

The unsubstituted spirononadiene has been obtained from silicon atoms and the diene, albeit in low yield. However it results in better yield from methoxytris(trimethylsilyl)silane and the diene on photolysis. a-Elimination is non-specific but favours the methoxysilylene, addition giving the two silacyclopentenes (111) and (112) with buta-1,3-diene (Scheme 186). Pyrolysis with excess butadiene gives the spiro derivative, in support of the cyclosilylene intermediate (113 Scheme 187) (81JA7344). 

While coupling provides the main route to germanium, tin and lead derivatives, an extensive series of ring closure reactions involving a pair of terminally activated substituents on the silane have been used. These have been reviewed more applicable to smaller rings are included in earlier sections of this article, notably hydrosilation (Schemes 147 and 148 Section 1.20.8.1). The pyrolysis of a,a>-distannaalkanes provides a novel route to stannacycloalkanes (Scheme 152). 

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