Synthesis of ZrC-SiC Powders by a Preceramic Solution Route

Homogenous liquid precursor for ZrC-SiC was prepared by blending of Zr(OC4H9)(4) and Poly[(methylsilylene)acetylene]. This precursor could be cured at 250 degrees C and converted into binary ZrC-SiC composite ceramics upon heat treatment at 1700 degrees C. The pyrolysis mechanism and optimal molar ratio of the precursor were investigated by XRD. The morphology and elements analyses were conducted by SEM and corresponding energy-dispersive spectrometer. The evolution of carbon during ceramization was studied by Raman spectroscopy. The results showed that the precursor samples heat treated at 900 degrees C consisted of t-ZrO2 (main phase) and m-ZrO2 (minor phase). The higher temperature induced phase transformation and t-ZrO2 converted into m-ZrO2. Further heating led to the formation of ZrC and SiC due to the carbothermal reduction, and the ceramic sample changed from compact to porous due to the generation of carbon oxides. With the increasing molar ratios of C/Zr, the residual oxides in 1700 degrees C ceramic samples converted into ZrC and almost pure ZrC-SiC composite ceramics could be obtained in ZS-3 sample. The Zr, Si, and C elements were well distributed in the obtained ceramics powders and particles with a distribution of 100300nm consisted of well-crystallized ZrC and SiC phases.