Fabrication of Three‐Dimensional Wavy Single‐Chamber Solid Oxide Fuel Cell by In Situ Observation of Curvature Evolution

Abstract

This study presents a fabrication process via experimental observations for curved porous multilayer structures with a single‐step, co‐sintering operation. Active monitoring of the shrinkage behavior of each porous layer during the co‐sintering process leads to minimize mismatched stresses along with avoidance of severe warping and cracking. During co‐sintering, in‐plane stresses are developed in each layer due to differing shrinkage behaviors between layers. Analysis of curvature evolution using in situ monitoring of the structure was performed in the design of a curved multilayer structure via the co‐sintering process. Materials used are NiO/CGO for anode; CGO for electrolyte; and LSCF for cathode. These materials are tape casted with 20 μm thickness and stacked to form bi‐ and triple‐layer structures by hot‐pressing. Bilayers, consisting of NiO/CGO‐CGO and CGO‐LSCF, were co‐sintered up to 1200°C. The maximum sintering mismatched stress was calculated at the interface of bilayer structure. In situ observation, to monitor the shrinkage of each material and the curvature evolution of the bi‐ and triple‐layer structures, was performed using a long focus microscope (Infinity K‐2). Thereby, viscosity, shrinkage rate of each material, and curvature rate were calculated to determine the mismatched stresses. The monitored results contributed to development of novel design of curved 3D multilayer structures during co‐sintering.

深層学習を援用したテープ成形セラミックス焼結過程のその場観察と積層体変形予測への応用

“…重要である．実際，これまでにも多くの焼結力学モデルが提案され，一体焼結時の変形予測が行われてきた (Molla et al, 2014;Olevsky et al, 2006;Shinagawa, 2003)．しかしながら実測との相違も報告されるなど，数値予測法の精 度検証の重要性が指摘されている (Bordia et al, 2017, Wakai et al, 2019． 一体焼結の変形数値予測モデルを構築し，そのモデルの妥当性を検証するためには，積層前の単層セラミック スシートの収縮挙動，ならびに圧着後の積層セラミックスシートのそり変形挙動を正確に計測できる技術が不可 欠である．従来，焼結体の収縮特性を測定する方法として，試験体にプッシュロッドを接触させる膨張計が広く 用いられてきた (Möbius et al, 2009)．ただし，接触式の欠点として，接触に伴う荷重が焼結体の収縮特性に影響を 及ぼすこと，グリーンシートのような膜状かつ脆い試料に均等な荷重を負荷することが難しいこと，さらにそり 変形を伴う積層体の形状測定には不向きであることが挙げられる．一方近年，非接触で焼結体の形状変化を追跡 できる有用な手法として，光学装置を用いたその場観察法が提案され，これまでにも，SOFC 電解質や燃料極セ ラミックスグリーンシートの収縮挙動や粘性特性の評価に活用されてきた (Atkinson et al, 2011;．また，初期密度の異なる電解質材料を一体焼結した際のそり挙動もその場観察法を用 いて報告されている (Choi et al, 2016;Cologna et al, 2009) CNN を用いたセグメンテーションネットワークのうち，最も標準的なものは Encoder₋Decoder 型構造で構成さ れたネットワークである．中でも，Segnet (Badrinarayanan et al, 2015)，U-net (Ronneberger et al, 2015)，DeepLab V3+ (Chen et al, 2018)が代表的な Encoder₋Decoder 型ネットワークとして知られ，様々な分野の画像セグメンテー ションタスクに適用されるとともに，その性能比較が実施されてきた (Ramirez et al, 2020, Khan et al, 2020．そこ (Cai et al, 1997a(Cai et al, , 1997b…”

Single‐step fabrication of an anode supported planar single‐chamber solid oxide fuel cell

“…Furthermore, thermal expansion coefficient (TEC) mismatch between each layer becomes a dominant factor when materials have higher viscosity that is, during cooling process . Therefore, in order to achieve the single‐step co‐sintering of an anode supported SC‐SOFC, the sintering temperature was decreased to obtain a preferable cathode microstructure, while still densifying the electrolyte . In addition, the sintering temperature of the cathode is generally less than that of the anode and electrolyte .…”

“…6 Therefore, in order to achieve the singlestep co-sintering of an anode supported SC-SOFC, the sintering temperature was decreased to obtain a preferable cathode microstructure, while still densifying the electrolyte. 11,17,18 In addition, the sintering temperature of the cathode is generally less than that of the anode and electrolyte. 11,19,20 Therefore, the cathode particle size was chosen to be greater than that of the anode and cathode, so as to retard the sintering kinetics of the cathode and thereby suppressing quicker densification, as well as to balance the final density of materials during the co-sintering process.…”