Polymeric Routes to Silicon Carbide

Abstract

Several classes of organosilicon polymers are effective precursors for silicon carbide ceramic compositions. These include polydimethylsilane (via a two‐step process), ‘polysilastyrene’, polycarbosilazanes or polysilazanes, and certain siloxanes, plus the branched polycarbosilanes, branched polysilahydrocarbons, and vinylic polysilanes developed at Union Carbide. The latter three classes are prepared by active metal dechlorinations of appropriate chlorosilane blends, leading to recognition of branching at backbone silicon atoms (either as prepared or during processing) as a prerequisite for obtaining useful ceramic yields. Fundamental reactivity differences between the active metals (potassium and sodium) allow the preparation of sodium‐derived vinylic polysilanes. The latter offer certain economic and performance advantages as ceramic precursors.

Organosilicon Polymers?Synthesis, Architecture, Reactivity and Applications

“…40,62,63 In such a way vinylic copolymers and terpolymers were obtained. Additionally, MeHSiCl 2 may be applied instead of Me 2 SiCl 2 , thus aiding the increase of ceramic yields on pyrolysis.…”

Efficient curing of polymethylsilane by borazine and reaction mechanism study

“…Formation of SiÁ/N by reaction between the SiÁ/H in PMS and the NÁ/H in borazine (Scheme 1) could have been responsible for the former signals in the range (/28 to 15 ppm. [24,25] Assignment can be partly made by referring to chemical shifts in series of organosilicon compounds with substituted N atoms; (CH 3 ) 4 Si at 0ppm, (CH 3 ) 3 Si N(CH 3 ) 2 at 5.9 to Â/6.9 ppm, (CH 3 ) 2 Si (N(CH 3 ) 2 ) 2 at (/1.30 to Â/(/1.85 ppm, CH 3 Si(N(CH 3 ) 2 ) 3 at (/16.30 to Â/ (/17.50 ppm and Si (N(CH 3 ) 2 ) 4 at (/28.1 to Â/ (/28.6 ppm [24,25]. As the 29 Si chemical shift is affected by not only the nearestneighbor atoms but also the next-nearest-neighbor atoms in the presence of B atom as adjacent atoms of N atom, which may have caused the observed peak broadening.…”

Evaluation of poly(methylsilane‐carbosilane) synthesized from methyl‐dichlorosilane and chloromethyldichloromethylsilane as a precursor for SiC

“…Much effort has been devoted to overcome the drawbacks of PMS. For example, addition of unsaturated organic compounds (divinylbenzene, tetravinylsilane), metallorganic compounds [Ru 3 (CO) 12 , CpTi(CH 3 ) 2 , Al(acac) 3 ], and metal chlorides (TiCl 4 , MoCl 5 , SbCl 3) to increase molecular weight or crosslinking of PMS and improve their ceramic yield, or introduction of the second monomer to obtain copolymer, as well as the second polymer to obtain hybrid polymer precursor . However, the drawback of low synthetic yield and not good enough storage stability is still the big obstacle for its application.…”