Reformulation of Oxide Growth Equations for Oxidation of Silicon Bond Coat in Environmental Barrier Coating Systems

Sullivan, Roy M

关键词: PROTECTIVE COATINGS;    OXIDATION;    SILICON;    LINEAR EQUATIONS;    BARRIER LAYERS;    ENVIRONMENT PROTECTION;   

RP-ID  :  GRC-E-DAA-TN61998,NASA/TM—2019-220028

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来源: NASA Technical Reports Server

【 摘 要 】

The formulation of Deal and Grove for the oxidation of silicon and the growth of a silica layer is revisited to include the effects of a protective coating layer. The linear-parabolic equation of the form x_o^2+Ax_o=Bt is still applicable, but the expressions for the constants A and B must be modified to account for the coating. The modified expression for A is a linear function of the coating thickness. The expression for B is modified by the relative solubility of the outer coating layer. The modified expressions are applied to assess recently published experimental results for the oxidation of a silicon bond coat in an environmental barrier coating (EBC). Conclusions are drawn regarding the diffusivity and solubility of oxidants in the EBC top coating.