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

• Combination of SHS and HP use to obtain ceramics in the ZrSi 2 -MoSi 2 -ZrB 2 system. • Kinetics of oxidation at 1400 °C described using a power function with index n > 2. • Mostly the ZrSi 2 phase were oxidized. • Two-layer film formed during oxidation consist of silicate glass and ZrSiO 4 sublayer. • ZrSiO 4 with scheelite-type structure encapsulate the ZrB 2 and MoSi 2. The results of a study of the kinetics and mechanism of heterogeneous and compact ceramics oxidation in the ZrSi 2 -MoSi 2 -ZrB 2 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 ZrSiO 4 phase, with the scheelite structure encapsulating the ZrB 2 and MoSi 2 grains. The influence of the ZrSi 2 , MoSi 2 and ZrB 2 phases on the structural-morphological peculiarities of the appearing oxide films and the effectiveness of its protective action are revealed. [ABSTRACT FROM AUTHOR]