No abstract

Single-walled carbon nanotubes (SWNTs) were incorporated into precursor-derived ceramics made from a polysilazane. To improve the dispersion of the nanotubes in the liquid precursor and finally in the ceramic matrix, the SWNTs were chemically modified by (iodomethyl)trimethylsilane via a radical reaction. The functionalization degree of the modified SWNTs was determined to be 3 atom %. Microscopic investigation combined with viscosity measurements and thixotropy tests demonstrated that the functionalized SWNTs are more homogeneously dispersed in the liquid SWNT/polymer mixtures and the solid cross-linked precursor, as compared to pristine nanotubes. SWNT/Si-C-N ceramics with nanotube contents of up to 1 wt % were obtained through pyrolysis of cross-linked SWNT/polymer composites at 1000°C. The presence of intact nanotubes in these composites could be verified by scanning transmission electron microscopy. The high viscosity of the SWNT/polysilazane mixtures was identified as an important prerequisite for attaining good nanotube dispersion in the Si-C-N matrix.

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.