Vol. 60 No. 5Material Science and Technology of Japan, 60（2023）159〜166

13Regular Paper
Effect on Self-healing Behavior of SiC Size on Yb2Si2O7/SiC
Composites for Environmental Barrier Coatings
Seung-Hyeon KIM1, Toshio OSADA1 and Byung-Koog JANG2,*
1 Research Center for Structural Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba,

Ibaraki 305-0047, Japan
2 Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6–1 Kasuga-koen, Kasuga,Fukuoka 816-8580, Japan
Received Jul. 21, 2023; accepted Sep. 11, 2023
Abstract
Dispersions of SiC (nano) and SiC (micro) are proposed to maintain the Yb2Si2O7 matrix and promote crack selfhealing for environmental barrier coating (EBC). The high-temperature self-healing behavior of Yb2Si2O7/ 20 vol.%SiC (micro, nano) was investigated at temperatures of 1100 and 1300°C for up to 10 h in air. The self-healing effect isaffected by SiC size, oxidation time and temperature. The formation of SiO2 by high-temperature oxidation of SiC
particles was analyzed by XRD at 1100°C from 5 h for SiC (micro) to 2 h for SiC (nano). Commonly, surface cracks
were fully recovered after heat treatment at 1300°C for 0.5 h in air. Cracks were recovered by volume expansion due
to SiO2 formed by SiC oxidation, and the crack recovery rate increased as the size of SiC (micro, nano) decreased. The
self-healing behavior of the Yb2Si2O7/20 vol.% SiC composite as a function of SiC (micro, nano) demonstrates that it
is worth further investigation as an EBC material.
Keywords: Yb2Si2O7, SiC, Self-healing, Oxidation, Environmental barrier coating

1.

Introduction

maintain the mechanical stability and protective properties of EBC,

SiC-based ceramic matrix composites (CMCs) are applied as

the cracks formed must be healed [23]. In the case of SiC as ahigh-temperature structural materials for next-generation gas

healing agent, the self-healing mechanism is that the cracks are

turbines due to their excellent high-temperature mechanicalfilled by SiO2, an oxidation product of SiC, and form depending

properties and oxidation resistance [1–2]. In a high-temperatureon the oxidizing environment (temperature and time). The

combustion environment, a silica protective layer is formed on thefollowing reaction proceeds in a high-temperature steam

surface of CMCs, and the generated water vapor reacts with theenvironment [24–25].

silica protective layer to form volatile silicon hydroxide,
shortening the lifespan of CMCs [3–6]. Therefore, an

SiC(s)+3/2O2(g)→SiO2(s)+CO(g)↑(1)

environmental barrier coating (EBC) is applied to increase theSiC(s)+3H2O(g)→SiO2(s)+CO(g)↑+3H2(g)↑(2)

durability of the CMCs and protect it from water vapor [7–18].

SiO2(s)+2H2O(g)→Si(OH)4(g)↑(3)

However, cracks occur on the surface of the EBC itself due tothermal shock and physical impact of fine dust or debris from theRecently, rare-earth (RE) silicates have been reported ascombustion section of the gas turbine. Cracks seriously affectpromising EBC materials [26–28]. In particular, many studies

EBC durability in a high-temperature combustion environment.

have been reported on Yb2Si2O7 because its resistance to water

To solve this problem, it is to develop structural ceramics withvapor corrosion and coefficient of thermal expansion (CTE) are

self-healing properties to improve durability [19–22]. In order tosimilar to those of SiC [26,29,30]. However, Yb2Si2O7 and other
EBC ceramics have low fracture toughness and strength, making*Corresponding author: jang.byungkoog@kyudai.jp(159)