| Abstract
| - B-trichloroborazene B3N3H3Cl3 reacts with bis(trimethylsilyl)carbodiimide Me3Si−NCN−SiMe3 to form B/C/N/H gels. Pyrolysis at 1200 °C provides an amorphous ceramic with the composition BC0.23N1.1Si0.05H0.09 ≈ B4CN4. This novel nitrogen-rich phase may be a promising precursor for the synthesis of crystalline B/C/N phases. It crystallizes above 1600 °C forming pure B4C at 2000 °C. B4C is known for its extreme hardness and chemical inertness. Small amounts of amorphous carbon as well as carbon nanotubes were also present.
- B-trichloroborazene B3N3H3Cl3 reacts with bis(trimethylsilyl)carbodiimide Me3Si−NCN−SiMe3 in THF or toluene, or without any solvent, to form non-oxide gels. The xerogels,amorphous B/C/N materials, and (semi)crystalline pyrolysis products were characterizedusing infrared (FTIR) and Raman spectroscopy, 11B- and 15N-nuclear magnetic resonancespectroscopy (NMR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM),transmission electron microscopy (TEM), and elemental analysis. In addition, the pyrolysisprocess was investigated through thermal gravimetry coupled with mass spectrometry(TG−MS). The xerogels consist of a three-dimensional polymeric network of borazene ringslinked by carbodiimide groups. Interestingly, the sol−gel transition is phenomenologicallyanalogous to oxide systems and the polymers are almost free of chlorine and trimethylsilylendgroups. Pyrolysis at 1200 °C provides an amorphous ceramic with the compositionBC0.23N1.1Si0.05H0.09 ≈ B4CN4. This material starts to crystallize around 1600 °C underevolution of nitrogen, forming nearly pure B4C at 2000 °C. Very small amounts of amorphouscarbon as well as carbon nanotubes were also present.
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