Pyrolytic conversion studies of blended polycarbosilane and polyaluminasilazane

Abstract Multinuclear solid-state NMR spectroscopy, FTIR and Raman experiments are employed to investigate the pyrolytic conversion of blended polycarbosilane and polyaluminasilazane (denoted CA) up to 800 °C, with the aim of studying structural evolutions and interactions between polycarbosilane and polyaluminasilazane during the pyrolysis process. Vinyl and SiCH 3 units can react with Si–H, SiCH 3 and Si–CH 2 –Si groups below 400 °C. These crosslinking reactions can increase the ceramic yield of the blended precursors. At 500 °C aromatic carbon is formed, and N–H and Si–H groups vanish at 600 °C and 700 °C, respectively. At 600 °C, SiCH 3 and Si–H units can further react with SiCN 3 , SiC 2 N 2 , N–H and C–H units. An amount of amorphous carbon and CSi 4 and CSi 3 H groups are detectable at 800 °C. Even at this temperature there are still many aromatic protons. In addition, there are also SiC 4 , SiC 3 N, SiCN 3 and SiN 4 units. Silicon forms SiN 4 more readily than SiC 4 . Many AlN 5 groups transform into AlN 6 groups. The D and G bands of graphite are observed in CA pyrolyzed at 1400 °C. According to the XRD patterns, the reflection of crystalline β-Si 3 N 4 vanishes at 1700 °C, and the residue pyrolyzed at 1800 °C mainly contains a large number of 2 H -SiC/AlN solid solution crystals and a few β-SiC crystals.