Polymer-ceramic conversion of liquid polyborosilazanes

The chemical structure and ceramization process of a liquid polymer precursor for SiBNC ceramics were investigated by Fourier transform infrared spectrometry, thermal gravimetric-differential scanning calormetry analysis and X-ray diffraction, respectively. The results indicate that there are the side substituents of -CH ₃ and -CH=CH ₂, and the bonds of C-H, C=C, Si-H, B-N, N-H, Si-N in the precursor structure. The ceramic yield of the precursor obtained in nitrogen atmosphere is 85% (in mass) and the mass loss occurs mainly in 300-800°C. The amounts of organic groups decrease with the increase of temperature. The amorphous SiBNC ceramics containing free carbon were obtained at 900°C. The ceramics started to crystallize above 1200°C, resulting in the formation of partially crystallized phases of C, SiC, Si ₃N ₄ and BN.