Preparation and Thermophysical Properties of (Sm_0.2Gd_0.2Dy_0.2Y_0.2Yb_0.2)₃TaO₇High-entropy Ceramic

Abstract

Developing novel ceramic materials with excellent thermophysical properties is one of the hotspots in the field of thermal barrier coatings. The (Sm 0.2 Gd 0.2 Dy 0.2 Y 0.2 Yb 0.2 ) 3 TaO 7 high-entropy ceramic was fabricated via high-temperature solid-state reaction. The crystal structure, microstructure, phase stability and thermophysical properties were investigated. Results indicate that (Sm 0.2 Gd 0.2 Dy 0.2 Y 0.2 Yb 0.2 ) 3 TaO 7 high-entropy ceramic has single defective fluorite structure, its elements are homogenously distributed, its grain size ranges from 0.2 to 3 μm. After high-temperature thermal cycling, the sample still remains single fluorite structure, showing excelleent phase stability at high temperature. Thermal conductivity lies in the range of 0.72-0.74 W/(m•K), lower than that of 7YSZ. Thermal expansion coefficient at 1200 ℃ is 5.6×10 -6 K -1 , lower than requirement of thermal barrier coatings (TBCs) for surface ceramic layer. However, its thermal expansion coefficient is close to that of the silicon-based ceramics substrate of environmental barrier coatings (EBCs) ((3.4-5.5)×10 -6 K -1 ).

The Effect of a Coating on the Crystallization of Multicomponent Co-Based Amorphous Alloys

“…The state of the coating is undoubtedly important for the kinetics of crystallization and, in particular, it can play a decisive role in the kinetics of the removal of free volume from the sample to the surface. The authors of [72] observed the formation of a porous structure at the interface between a nickel based superalloy and a high-entropy rare-earth aluminate (Y 0.2 Yb 0.2 Lu 0.2 Eu 0.2 Er 0.2 ) 3 Al 5 O 12 coating. The coating thickness in this case was 5 µm.…”

Electrophoretic Deposition of ZnO-Containing Bioactive Glass Coatings on AISI 316L Stainless Steel for Biomedical Applications

“…This EC consisted of (CPEin-Rin) elevated by the barrier role of the oxide film primarily formed on a stainless steel substrate, and (CPEout-Rout) resulting from the porous outer layer of the passive film, which is decreased considerably by the presence of zinc oxide nanoparticles in the coating, and Rs related to solution resistance; the support for using an EC with two (CPE-R) combinations comes from the careful examination of the Bode phase plots. Overall, the corrosion resistance of stainless steels and coating materials is due to an inter-relation of several factors, including the chemistry of the alloy, the surface roughness, and the microstructure [36][37][38]. An equivalent circuit (EC) model (Figure 11) based on a two-layer structure dielectric (an inner compact layer and an outer relatively porous layer) was used for fitting the experimental data of the substrates [33] and the coatings [34,35] using ZVIEW software (2006).…”