Matrix structure evolution and thermo-mechanical properties of carbon fiber-reinforced Al2O3SiCC castable composites

• Carbon fibers are formed in Al2O3SiCC castable composites under the action of nano Ni.
• Starting growth temperature is 900 °C and growth mechanism agrees with V–S model.
• The high temperature strength of composites can be increased by above 40%.
• The thermal shock resistance can be enhanced by above 20%.

The spalling and corrosion during the thermal cycles are the main causes of the damages observed in Al2O3SiCC castable composites that are used in molten-iron system. Using the catalyst of nano Ni and ball pitch in the matrix, Al2O3SiCC castable composites were prepared with the anti-oxidant addition of silicon. The results indicate that the high temperature of the Al2O3SiCC castable composites can be increased by above 42%, and the thermal shock resistance can be enhanced by above 20% because the ball pitch is carbonized and releases CxHy vapor, which can be pyrolized to carbon atoms and subsequently deposited into carbon fibers under the catalyst action. The starting temperature of carbon fiber growth is approximately 900 °C, and their diameter and aspect ratio can increase with the rising temperature. The in-situ generation of carbon fibers in Al2O3SiCC castable composites can significantly improve the fibers’ thermo-mechanical properties.

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