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. Issue 7 (15th April 2020)

• Record Type: Journal Article
• Authors: Nguyen, Son Thanh; Nakayama, Tadachika; Takahashi, Tsuyoshi; Suematsu, Hisayuki; Do, Dung Thi Mai; Okawa, Ayahisa; Niihara, Koichi
• Is Part Of: Advanced engineering materials. Volume 22:Issue 7(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-04-15
• Subjects: healing agents -- nanocomposites -- recycling -- self-repair -- ytterbium silicate; Materials -- Periodicals; 620.11
• DOI: 10.1002/adem.202000157
• Languages: English
• ISSNs: 1438-1656

Abstract

Abstract : Yb2 Si2 O7 /Yb2 SiO5 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 SiO2 glass and the newly formed Yb2 Si2 O7 in the composite. The reaction between SiO2 and Yb2 SiO5 to form Yb2 Si2 O7 is considered a critical step that determines the high healing efficiency of this composite, therefore, Yb2 SiO5 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, Yb2 SiO5 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. Abstract : Yb2 Si2 O7 –Yb2 SiO5 –SiC nanocomposites with self‐healing ability are promising materials for environmental barrier coatings. However, once all the Yb2 SiO5 healing agents react, the composite loses its fast crack‐healing ability. To retain this property, Yb2 SiO5 is regenerated through a heat treatment in steam. Analyses confirm that the healing agent is partially recycled and the crack‐healing ability of the treated‐composite is improved.