Preparation of Si-Al-N-C ceramic composites by pyrolysis of blended precursors

Abstract

Si-Al-N-C precursors have been prepared from perhydropolysilazane (PHPS) and cage-type poly (ethyliminoalane) [(HAlNEt)n; PEIA, n is mainly 8] with different Si/Al molar ratios (Si/Al-3, 1, 1/3). Spectroscopic analysis indicates that essentially no Si-N-Al linkages form, indicating that the precursors are blended polymers. TG analysis reveals that the ceramic yields of the blended precursors up to 900°C are higher than those of PHPS and (HAlNEt)n, suggesting that cross-linking reactions occur during pyrolysis. Possible reactions are dehydro-coupling and radical reactions, as suggested by the results of solid-state nuclear magnetic resonance (NMR) spectroscopy. The results of solid-state NMR spectroscopy and X-ray diffraction (XRD) analysis indicate that the residue pyrolyzed at 1600°C contains mainly crystalline AlN, 2H-SiC and β-SiC.