Kinetics and mechanism of the oxidation of ZrSi2-MoSi2-ZrB2 ceramics in air at temperatures up to 1400 °C

• Published in: International journal of heat and mass transfer 2019-09, Vol.140, p.12-20
• Main Authors: Astapov, A.N., Pogozhev, Yu.S., Prokofiev, M.V., Potanin, A.Yu, Levashov, E.A., Vershinnikov, V.I., Rabinskiy, L.N.
• Format: Article
• Language: English
• Subjects: Air temperature; Ceramic powders; Ceramics; High temperature; Hot-pressing; Kinetics; Magnesiothermal recovery; Magnesium; Molybdenum disilicides; Oxidation; Oxide coatings; Protective coatings; Reaction kinetics; Refractory materials; Scheelite; Self propagating high temperature synthesis; SHS; Zirconium compounds; Zirconium silicate
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2019.05.100

[Display omitted] •Combination of SHS and HP use to obtain ceramics in the ZrSi2-MoSi2-ZrB2 system.•Kinetics of oxidation at 1400 °C described using a power function with index n > 2.•Mostly the ZrSi2 phase were oxidized.•Two-layer film formed during oxidation consist of silicate glass and ZrSiO4 sublayer.•ZrSiO4 with scheelite-type structure encapsulate the ZrB2 and MoSi2. The results of a study of the kinetics and mechanism of heterogeneous and compact ceramics oxidation in the ZrSi2-MoSi2-ZrB2 system at air temperature of 1400 °C are presented. The ceramics were obtained by the hot-pressing of composite powders that were manufactured by self-propagating high-temperature synthesis following the magnesiothermal recovery approach. Oxidation kinetics are described using a power function with index n>2, confirming the significant influence on the evolution process in the structure of the formed oxidation coating. The oxidation mechanism includes the formation of a two-layer structure consisting of a continuous silicate film, of which the outer part contains magnesium and a sublayer based on the ZrSiO4 phase, with the scheelite structure encapsulating the ZrB2 and MoSi2 grains. The influence of the ZrSi2, MoSi2 and ZrB2 phases on the structural-morphological peculiarities of the appearing oxide films and the effectiveness of its protective action are revealed.