 | Si-B-C-N PRECURSOR: SYNTHESIS AND THERMAL STABILITY
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| | Markus Weinmann1) and Fritz Aldinger1) |
| | 1) Max-Planck-Institut für Metallforschung and Institut für Nichtmetallische Anorganische Materialien, Universität Stuttgart, Pulvermetallurgisches Laboratorium |
| | The synthesis and thermal behavior of boron-modified polysilazanes and polysilylcarbodiimides is discussed. The title compounds were obtained by different methods e.g. metathesis reactions of tris(chlorosilylethyl)boranes with ammonia or bis(trimethylsilyl)carbodiimide, hydroboration of vinylated polysilazanes and polysilylcarbodiimides or base-catalyzed dehydrogenative coupling of ammonia and tris(hydridosilylethyl)boranes. Besides synthetic procedures, the ceramization of the Si-B-C-N polymers, monitored by thermogravimetric analysis (TGA), is reported. High temperature thermogravimetric analysis (HT-TGA) of the as-obtained amorphous ceramics carried out in inert gas atmosphere up to 2200°C, occasionally reflect their stability towards decomposition up to 2000°C. HT-TGA in air reveal resistance of the Si-B-C-N ceramics towards oxidation, due to the formation of protective Si-C-O surface layers. XRD and NMR analyses of annealed samples indicate microstructure evolution in the 1550-1750°C range, where the as-obtained amorphous ceramics transform into α-SiC and β-Si3N4 crystalline phases. |
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