Effects of in situ synthesis of CNTs/SiC _w on microstructure and properties of Al ₂ O ₃ –SiC–C composites

Abstract Al ₂ O ₃ –SiC–C composites were prepared using tabular corundum, ball pitch and silicon carbide as the main raw materials. The carbon nanotubes (CNTs) and SiC whiskers (SiC _w ) were in situ synthesized and their effects on the thermo–mechanical properties of Al ₂ O ₃ –SiC–C composites have been studied. The experimental results indicated that the high yield of SiC _w and CNTs with large aspect ratio could be obtained due to addition of Ni(NO ₃ ) ₂ ·6H ₂ O as catalyst in the composites. The cold modulus of rupture values were increased by 24% to 7.2 MPa, and the flexural modulus was increased from 19 GPa to 24 GPa. Additionally, the hot modulus of rupture reached a maximum value of 3.6 MPa, which presented a 71% increase over that of composites without catalyst. After three thermal shock cycles, the residual cold crush strength was improved from 57.1% to 76.9%. It is believed that the enhancement in the thermo‐mechanical properties of Al ₂ O ₃ –SiC–C composites could be attributed to the reinforcement effect of SiC _w and CNTs.