Dehydrocoupling of tris(hydridosilylethyl)boranes with ammonia or amines: a novel route to Si–B–C–N preceramic polymers

Abstract

0, 1) and ammonia or methylamine is reported. Detailed characterization of the title compounds was performed using spectroscopic methods such as solid-state NMR spectroscopy, IR spectroscopy, and elemental analysis. Thermolysis produces amorphous Si-B-C-N ceramics with ceramic yields between 25 and 83%, as determined by thermogravimetric analysis (TGA) in argon. High-temperature TGA in an argon atmosphere reveals that a number of the ceramics obtained resist degradation up to $2000°C. X-ray diffraction studies of the asobtained amorphous materials show formation of a-SiC or a-SiC/b-Si 3 N 4 crystalline phases between 1600 and 1800°C, depending on the composition of the materials.

Thermal Stability, Phase Evolution, and Crystallization in Si‐B‐C‐N Ceramics Derived from a Polyborosilazane Precursor

“…In this context, particularly work of Riedel et al and Jansen et al should be mentioned, who independently reported on the synthesis of quaternary Si-B-C-N ceramics from structurally different singlesource precursors. 5,7 An alternative procedure for the synthesis of Si-B-C-N precursors with comparable structures which avoids formation of solid byproducts in the final reaction step, thus facilitating the processing, was recently published by Weinmann et al [12][13][14][15] The unusual resistance against decomposition and crystallization at very high temperatures in quaternary boron-containing ceramics was explained by the formation of a turbostratic B-C-N phase, 16 which retards possible decomposition reactions by a kinetic stabilization mechanism. 17 Until now, the extent of this kinetic stabilization under different thermal conditions was not studied.…”

Silicon-Based Polymer-Derived Ceramics: Synthesis Properties and Applications-A Review

“…58,163 In the first step, chlorosilanes are treated with LiAlH 4 to form the corresponding organosilanes. The second step is an n BuLi catalysed dehydrocoupling reaction.…”

“…These polymers can be successfully synthesized by the reaction of tris chlorosilyl-ethyleneboranes BC 2 H 4 SiRCl 2 3 with an excess of bistrimethylsilylcarbodiimide Scheme 9: 74,75,166 Unfortunately, the ceramics obtained from these polymers do not possess satisfactory ultra high-temperature properties, since the thermal degradation already starts at Tࢽ1500c C. Preliminary studies suggested that the degradation temperature strongly depends on the nitrogen content of the samples. 163 In order to reduce the amount of nitrogen, a dehydrocoupling reaction of trishydridosilyl-ethyleneboranes with cyanamide, H 2 N-CN was developed.…”

Control of structure formation of polycarbosilane synthesized from polydimethylsilane by Kumada rearrangement

“…[12][13][14][15][16][17][18][19][20][21][22][23] For example, polymetallocarbosilane (PMCS, M 5 Ti, Zr, Al) is used to manufacture Tyranno TM fibers by UBE Industries 24,25 and polytitanocarbosilane is also used to produce Sylramic TM fiber by Dow Corning 26 (now by ATK COI Ceramics); N-methylpolyborosilazane is developed to produce Siboramic TM fiber by Bayer; 19,27 high molecular weight PCS is synthesized to produce UF and UF-HM fibers in University of Florida; 28 polycarbosilazane is synthesized to prepare Si-C-N fibers in France; 29,30 polymethylsilane 31,32 and copolymerized polysilanes [33][34][35] are investigated as SiC-based fiber precursors; linear polysilylenemethylenes derived by ring opening polymerization 36 and hyperbranched PCS 37 by Grignard reaction are used as the precursors for near-stoichiometric SiC ceramics; various kinds of boron-modified polysilazanes or polysilylcarbodiimides are developed to prepare Si-B-C-N ceramics. 22,[38][39][40] Although many precursors are available, the most successful ones for commercial polycrystalline SiCbased fibers 41 are PCS and PMCS (M 5 Ti, Zr, Al). Most ongoing research on SiC-based fibers in Japan, 42 France, 43,44 Russia, 45 Korea, [46][47][48] …”