Synthesis of Polyyttriocarbosilane and its Conversion to Yttrium-Containing Ceramic.

The polyyttriocarbosilane (PYCS) with various quantities of yttrium was obtained by reacting yttrium acetylacetonate (Y(AcAc)) with polycarbosilane (PCS). The molecular weight, softening point, and Si-H bond content of the resulting PYCS are controlled by the Y(AcAc):PCS weight ratio, reaction temperature and reaction time. The main chain of the PYCS is made up of alternating carbon and silicon atoms with small amount of Si-O-Y presented in the main chain and Si-H groups at the side chain. The pyrolysis process of PYCS was investigated by TG and XRD. The results reveal that the polymer-to-ceramic transition of the PYCS occurs in three steps. The final ceramics obtained at 1,800 °C contain a large number of β-SiC crystallites and a small amount of α-SiC crystallites. [ABSTRACT FROM AUTHOR]