A simple way to prepare a precursor for ZrC-SiC ceramics

For cost reduction and process simplification, a homogenous liquid precursor for zirconium carbide (ZrC)-SiC ceramics was prepared by blending Zr(OC4H9)(4), divinylbenzene, and polycarbosilane (PCS). The mixture was cross-linked at 150 A degrees C, decomposed to ZrO2, carbon, and SiC at 800 A degrees C, and then ZrO2 and carbon reacted with each other via carbo-thermal reaction at 1500 A degrees C to form ZrC-SiC ceramics that contained few ZrO2. The ZrO2 content was reduced either by increasing the temperature from 1500 to 1700 A degrees C, or by extending the holding time from 1 to 2 h. Increasing the content of PCS in the precursor not only benefited the carbo-thermal reaction but also caused the generation of free carbon in the pyrolyzed ceramic products. When the precursor contained the optimal content of PCS, the ceramics fabricated from it had a Si/Zr molar ratio of 1. C/ZrC-SiC composites were successfully fabricated via precursor infiltration and pyrolysis using the precursor. The flexural strength and fracture toughness of the composites were 212 +/- A 44 MPa and 13.8 +/- A 1.6 MPa m(1/2), respectively.