Effects of Al2O3-RE2O3 Additive for the Sintering of SiC and the Fabrication of SiCf/SiC Composites

The sintering behavior of monolithic SiC is examined using the binary sintering additive of Al2O3-rare earth oxide (RE2O3, where RE = Sc, Nd, Dy, Ho, or Yb). Through hot pressing at 20 MPa and 1750 degrees C for 1 h in an Ar atmosphere for 52 nm fine beta-SiC powder added with 5 wt% sintering additive, a SiC density of > 97% is achieved, which indicates the effectiveness of Al2O3-RE2O3 system as a sintering of additive for SiC. Based on this result, 7 wt% of Al2O3-Sc2O3 is tested as an additive system for the fabrication of a continuous SiC fiber-reinforced SiC-matrix composite (SiCf/SiC). Electrophoretic deposition combined with the application of ultrasonic pulses is used to efficiently infiltrate the matrix phase into the voids of Tyranno (TM)-SA3 fabric. After hot pressing, a composite density of > 97% is obtained, along with a maximum flexural strength of 443 MPa.