High Temperature Oxidation Kinetics of Non-Oxide Monolithic and Particulate Composite Ceramics

摘要

The high temperature oxidation resistance of silicon and aluminium based non-oxide monolithic ceramics (Si_3N_4, SiC, AlN) depends on the formation of protective oxide scales. Oxidation kinetics seldom obey simple laws due to secondary effects (impurities, crystallization,...). Empirical or alternative growth equation are needed to model the experimental data. Increasing attention has been devoted to ceramic matrix composites in order to improve high-temperature strength, fracture toughness and/or tailor electrical, thermal, wear and chemical properties. However, the addition of compounds (TiN, TiB_2, ZrB_2...) that are easily oxidized in air generally results in a degradation of the protective properties of the oxide scale and leads to a complex oxidation behaviour due to microstructural and compositional changes or vaporization effects (B_2O_3). Ternary compositions [AlN-SiC-TiB_2, AlN-(TiB_2-TiSi_2), AlN-SiC-ZrB_2] have been developed in order to form protective scales containing mullite, aluminium borates or aluminium titanates leading to excellent oxidation resistance up to temperatures as high as 1350-1550℃.