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Recycling of a Healing Agent by a Water‐Vapor Treatment to Enhance the Self‐Repair Ability of Ytterbium Silicate‐Based Nanocomposite in Multiple Crack‐Healing Test
Author(s) -
Nguyen Son Thanh,
Nakayama Tadachika,
Takahashi Tsuyoshi,
Suematsu Hisayuki,
Do Dung Thi Mai,
Okawa Ayahisa,
Niihara Koichi
Publication year - 2020
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.202000157
Subject(s) - materials science , self healing , composite number , composite material , silicon carbide , nanocomposite , silicon , metallurgy , medicine , alternative medicine , pathology
Yb 2 Si 2 O 7 /Yb 2 SiO 5 composites dispersed with silicon carbide (SiC) possess a self‐crack‐healing ability that makes them promising top‐coat materials for multilayered environmental barrier coatings (EBCs) of SiC/SiC gas turbine blades. Stress‐induced surface cracks can be fully healed at high temperatures by the volume expansion of SiO 2 glass and the newly formed Yb 2 Si 2 O 7 in the composite. The reaction between SiO 2 and Yb 2 SiO 5 to form Yb 2 Si 2 O 7 is considered a critical step that determines the high healing efficiency of this composite, therefore, Yb 2 SiO 5 is considered as the secondary healing agent apart from the primary one, SiC. However, once all the healing agents have reacted, the composite can no longer promote its crack‐healing ability. To retain this property, in this work, Yb 2 SiO 5 is regenerated by a heat treatment in water‐vapor atmosphere at 1073 K. X‐ray diffraction (XRD) and energy‐dispersive X‐ray spectroscopy (EDS) analyses show that the healing agent can be partially recycled after the treatment. In addition, the composite treated in water vapor demonstrates a greater crack‐healing ability compared with the untreated composite. These results open a new path for the development of gas turbine blades and high‐temperature components possessing permanent crack‐healing ability.