Single-source-precursor synthesis and characterization of SiAlC(O) ceramics from a hyperbranched polyaluminocarbosilane

Polyaluminocarbosilane (PACS) as a single-source-precursor of SiAlC(O) ceramic was prepared by reacting a hyperbranched allylhydridopolycarbosilane (AHPCS) and aluminum(iii) acetylacetonate (Al(acac)3), and the PACS was characterized using gel-permeation chromatography, Fourier-transform infrared spectroscopy, and nuclear magnetic-resonance spectroscopy. The polymer-to-ceramic transformation of the obtained PACSs was investigated by Fourier-transform infrared spectroscopy and thermogravimetric analysis. The ceramic yield of the PACS was approximately 15% higher than that of the original AHPCS at 1,200°C. The phase composition and microstructure of the final ceramics were studied by X-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. The introduction of aluminum to the SiC(O) ceramics suppressed the β-SiC crystal growth and improved the density of the ceramics that were annealed at 1,800°C, which is advantageous for high-temperature ceramics. The aluminum content of the SiAlC(O) ceramics can be readily controlled by the Al(acac)3 content in the PACS precursors.