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,respec-tively.The results indicate that there are the side substituents of —CH3 and —CH=CH2,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 ℃.The amounts of organic groups decrease with the increase of temperature.The amorphous SiBNC ceramics containing free carbon were obtained at 900 ℃.The ceramics started to crystallize above 1 200 ℃,resulting in the formation of partially crystallized phases of C,SiC,Si3N4 and BN.