Influence of Al₂O₃ on the oxidation resistance of SiC ceramic: First-principle study and experiment

The influence of Al₂O₃ on the oxidation resistance of SiC was studied by first-principle calculation and oxidation test. The oxidation process of the Al₂O₃-doped SiC ceramic divides into three stages. At first, Al atom diffuses into the generated SiO₂ and substitutes Si atom to form –Al–O–Si– ring. Then, the ring is damaged due to the reaction between the O atom in Al–O bond and CO molecule, causing a CO₂ molecule and an O vacancy formation. Finally, once O₂ or another CO molecule approaches O vacancy, –Al–O–O–Si– or –Al–O–C–Si– ring will be formed to recover the network structure of SiO₂.