The oxidation resistance mechanism of SiC-B4C-xAl2O3 ceramics at 1400 ℃ in air atmosphere

The oxidation property of SiC-B 4 C- x Al 2 O 3 ( x ranges from 0 wt% to 30 wt%) ceramics was studied in air at 1400 ℃. Results show that the porous oxide layer becomes dense and smooth with addition of Al 2 O 3 . When the content of Al 2 O 3 is proper, the DOP (degree of polymerization) of borosilicate network can be improved with increase of Al 2 O 3 content, inhibiting the migration of atoms and molecular groups. With that, the crystallization of SiO 2 and volatilization of B 2 O 3 can be restrained. When the content of Al 2 O 3 is excessive, the DOP of borosilicate network will be decreased, deteriorating the oxide layer morphology. It is believed that the damage of borosilicate network by excess Al 2 O 3 should be responsible for this phenomenon. In this research, the SiC-B 4 C ceramic with optimal oxidation resistant can be obtained when the content of Al 2 O 3 is 15 wt%.