Synthesis and Characterization of Ethylene‐Bridged Copolycarbosilazane as Precursors for Silicon Carbonitride Ceramics

An ethylene‐bridged copolycarbosilazane precursor of copolysilylethylenediamine (co‐ PSDA ) is synthesized by polycondensation of ethylenediamine with the mixture of vinylmethyldichlorosilane and methyldichlorosilane in the presence of triethylamine as acid absorbing agent. Fourier transform infrared ( FTIR ) and nuclear magnetic resonance ( NMR , 1 H NMR and 13 C NMR ) spectral analysis of the as‐synthesized co‐ PSDA suggests a structure of ethylene‐bridged polycarbosilazane having –Si–N–C–C–N– as backbone chain with – CH = CH 2 , –H and – CH 3 attached to Si as side groups. Co‐ PSDA can be cross‐linked at 80°C using 2, 2‐azobisisobutyronitrile as initiator through the polyaddition of the vinyl group and dehydrogenation/deamination of Si–H and N–H. Then the cross‐linked co‐ PSDA precursor is pyrolyzed at 1000°C in argon, giving out amorphous silicon carbon nitride ( SiCN ) ceramics with a high ceramic yield of 76 wt%. The obtained SiCN ceramics consist of nitrogen‐rich silicon sites of SiN 4 as predominant component and some SiCN 3 sites, which should arise from the breaking of N–C bonds below 600°C and the formation of active N–Si bonds.