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In current work, the interaction between representative CFAS deposit (33CaO-10FeO 1.5 -13AlO 1.5 -44SiO 2) and Yb 4 Hf 3 O 12 ceramics at 1400 °C was investigated. Results indicated that the Yb 4 Hf 3 O 12 ceramics are of high resistance to infiltration of CFAS melt. Microstructure characterization revealed that Yb 4 Hf 3 O 12 reacted with CFAS to form a continuous reaction layer mainly composed of Yb-Ca-Si apatite, which inhibits CFAS further infiltration. Before the formation of the reaction layer, CFAS melts underwent a crystallization process at high temperatures, precipitating CaYbFeAlSi-garnet, which raised the viscosity of CFAS and thus inhibited the fluidity of CFAS. [ABSTRACT FROM AUTHOR]

In this work, Yb 4 Hf 3 O 12 ceramic, a typical rare-earth hafnate, was exposed to water vapor with Al(OH) 3 impurities at 1400 ℃, and microstructural evolution and corrosion mechanisms were investigated. The long-term corrosion can be divided into initial hydration and gasification of Hf4+ and steady-state corrosion after the formation of Al 5 Yb 3 O 12. In the initial stage, Hf4+ and the surrounding O2- tend to be hydrated and then volatilized in the form of Hf(OH) 4 , causing a metastable state of Yb 4 Hf 3 O 12 on the surface. Besides, the preferential corrosion of small grains, grain boundary, and specific crystal plane on the surface and sintered and densified grains result in varied corrosion behavior from the early linear law to the later parabolic law. In the steady-state corrosion stage, due to the consumption of Hf4+, more vacancies promote bonding and diffusion of Al3+ to form corrosion product (Al 5 Yb 3 O 12), and during this stage, regrowth and shedding of the corrosion layer reach a dynamic balance. [ABSTRACT FROM AUTHOR]

High-temperature molten silicate deposit corrosion has become a critical factor for the failure of thermal barrier coatings. In this work, promising ytterbium hafnate ceramics with different HfO 2 content were prepared by solid-phase reaction, and the effect of HfO 2 content on Fe-containing silicate corrosion behavior of ytterbium hafnate ceramics was investigated. The evolution of HfO 2 content showed negligible influences on reaction products and corrosion mechanism. The attack of Fe-containing silicate melts on the ceramic led to the formation of a reaction layer consisting of apatite, fluorite, and garnet. This layer plays a critical role in preventing further penetration of the melts. However, ytterbium hafnate ceramics with lower HfO 2 content showed better resistance to melt attack. [ABSTRACT FROM AUTHOR]