High Entropy Engineering: New Strategy for the Critical Property Optimizations of Rare Earth Silicates

doi:10.15541/jim20200611

Abstract

Abstract:

Environmental barrier coatings (EBCs) have been developed to improve the durability of SiC_f/SiC CMC components against harsh combustion environment. Among the most promising EBC candidates, rare-earth (RE) silicates attract attentions for their low thermal expansion coefficient, excellent high temperature water vaper and CMAS corrosion resistance, and good thermal and chemical compatibility with silicon-based ceramics and composites. Herein, we reviewed the optimizations of critical key properties of rare-earth silicates through strategic high entropy design to modify the current performance deficiencies of rare-earth silicates like thermal properties (coefficient of thermal expansion and thermal conductivity), CMAS corrosion resistance and high temperature phase stability. The present advancements demonstrate the merits of high entropy engineering for advanced EBCs for the improvement of crucial properties in engine applications.

Key words: high entropy engineering, high entropy ceramics, rare earth silicate, environmental barrier coatings, review

CLC Number:

TQ174

SUN Luchao, REN Xiaomin, DU Tiefeng, LUO Yixiu, ZHANG Jie, WANG Jingyang. High Entropy Engineering: New Strategy for the Critical Property Optimizations of Rare Earth Silicates[J]. Journal of Inorganic Materials, 2021, 36(4): 339-346.

Figures/Tables 8

Fig. 1 HAADF-STEM image of high entropy (Y1/4Ho1/4Er1/4Yb1/4)2- SiO5, EDS mapping of uniform spatial distributions for each element[40]

Fig. 2 Temperature dependent thermal expansion coefficient of high entropy (Y1/4Ho1/4Er1/4Yb1/4)2SiO5[40]

Fig. 3 Surface observations of high entropy (Er1/4Tm1/4Yb1/4Lu1/4)2Si2O7 after CMAS corrosion at 1500 ℃ for 4 h (a-b) and 50 h (c-d) [48]

Fig. 4 Observations of the reaction front in the cross-sections of high entropy (Er1/4Tm1/4Yb1/4Lu1/4)2Si2O7 after CMAS corrosion at 1500 ℃ for 4 h (a,b) and 50 h (c,d)[48]

Fig. 5 (a) XRD patterns of (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/4Lu1/6)2 Si2O7, along with the standard XRD patterns of RE2Si2O7 (RE = Y, Gd, Tb, Dy, Tm, Yb and Lu) and (b) Rietveld refinement of XRD pattern for (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/4Lu1/6)2Si2O7[50]

Fig. 6 (a) SEM image of (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/4Lu1/6)2Si2O7 surface with EDS mappings of Si, Gd, Tb, Dy, Tm, Yb and Lu, (b) STEM high angle annular dark field (HAADF) image and corresponding selected compositional EDS maps of high entropy (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/4Lu1/6)2Si2O7, and (c) schematic diagram of the phase formation of (6RE1/6)2Si2O7[50]

Fig. 7 (a)TG/DTA curves of (Gd1/6Tb1/6Dy1/6Tm1/6Yb1/4Lu1/6)2 Si2O7 and (b) XRD patterns of specimens after being heat-treated at 1800 and 1900 ℃ for 2 h[50]

Fig. 8 Schematics of the polymorphic transformation temperatures and melting points of RE2Si2O7 disilicates[50]

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