Astapov A.N. , Levashov E.A.  , Lifanov I.P.  , Pogozhev Yu.S.  , Potanin A.Yu. , Prokofiev M.V.  , Rabinskiy L.N.

DOI Number XXX-YYY-ZZZ

Conference Number HiSST 2018_2990961

This work presents the results of studying the kinetics and mechanism of high-temperature oxidation of compact heterophase ceramics in the ZrSi2-MoSi2-ZrB2 system at temperatures of 1400 and 1650°C for 10 and 5 hours, respectively. Ceramics was obtained by hot pressing of composite powders made by the method of self-propagating high-temperature synthesis according to the scheme of magnesium thermal reduction. The kinetics of oxidation is described by a power law, which indicates a significant influence of evolutionary changes in the structure of the formed oxide films on the course of the process. The oxidation mechanism at 1400°C includes the formation of a two-layer structure consisting of a continuous silicate film, the outer part of which is saturated with magnesium, and a sublayer based on the ZrSiO4 phase with a scheelite structure encapsulating ZrB2 and MoSi2 grains. The mechanism of oxidation at 1650°C includes the formation of a multilayer structure of a heterogeneous oxide film, the partial dissociation of the ZrSiO4 phase, the formation of secondary compounds MoB and Mo5Si3. The effect of the ZrSi2, MoSi2 and ZrB2 phases on the structuralmorphological features of the forming oxide films and the effectiveness of their protective action is shown. In the ZrSi2-ZrSiO4 system above 1620°C, under conditions of lack or absence of oxygen, silicon is being recovered with simultaneous oxidation of zirconium to ZrO2.

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In Categories: HiSST 2018, Materials and Structures, Self-Healing Materials, Thermal and Energy Management Systems, Thermal Protection Systems, Thermal Protection Systems
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