Polymer–Ceramic Conversion of Liquid Polyaluminasilazanes for SiAlCN Ceramics

Liquid‐phased polyaluminasilazanes were synthesized by simply reacting a liquid polyureasilazane with aluminum isopropoxide. The reaction was studied by Fourier‐transform infrared spectrometry (FTIR) and mass spectroscopy. The resultant polyaluminasilazanes were then pyrolysized to form amorphous SiAlCN ceramics at 1000°C in flowing N 2 . The structural evolution during pyrolysis was studied using solid‐state NMR and FTIR. Spectral analysis revealed that the amorphous structures of the ceramics consisted of SiC 2 N 2 and SiCN 3 as major building units, small amounts of SiC 3 N and SiN 4 units, and penta‐ or hexa‐coordinated aluminum with nitrogen. Such units were connected with each other through C−C/C=C bonds or by shearing N to form network structures. The results also revealed that the relative amount of these units strongly depended on the Al content.