Three-dimensional thermal stress analysis of the re-oxidized Ni-YSZ anode functional layer in solid oxide fuel cells

Kim, Jun Woo,Bae, Kiho,Kim, Hyun Joong,Son, Ji-won,Kim, Namkeun,Stenfelt, Stefan,Prinz, Fritz B.,Shim, Joon Hyung Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.752 No.-

<P><B>Abstract</B></P> <P>Nickel-yttria-stabilized zirconia (Ni-YSZ) cermet is widely used as an anode material in solid oxide fuel cells (SOFCs); however, Ni re-oxidation causes critical problems due to volume expansion, which causes high thermal stress. We fabricated a Ni-YSZ anode functional layer (AFL), which is an essential component in high-performance SOFCs, and re-oxidized it to investigate the related three-dimensional (3D) microstructural and thermo-mechanical effects. A 3D model of the re-oxidized AFL was generated using focused ion beam-scanning electron microscope (FIB-SEM) tomography. Re-oxidation of the Ni phase caused significant volumetric expansion, which was confirmed via image analysis and calculation of the volume fraction, connectivity, and two-phase boundary density. Finite element analysis (FEA) with simulated heating to 500–900 °C confirmed that the thermal stress in re-oxidized Ni-YSZ is concentrated at the boundaries between YSZ and re-oxidized NiO (nickel oxide). NiO is subjected to more stress than YSZ. Stress exceeding the fracture stress of 8 mol% YSZ appears primarily at 800 °C or higher. The stress is also more severe near the electrolyte-anode boundary than in the Ni-YSZ cermet and the YSZ regions. This may be responsible for the electrolyte membrane delamination and fracture that are observed during high-temperature operation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Re-oxidized NiO-YSZ was 3D-reconstructed via FIB-SEM tomography. </LI> <LI> Re-oxidation of Ni-YSZ removes pores via Ni volume expansion. </LI> <LI> The NiO-YSZ interface and the YSZ electrolyte exhibit high thermal stress. </LI> <LI> Thermal stresses greater than the fracture stress of YSZ appear at some interfaces. </LI> </UL> </P>

Influence of On-Stage Control Parameters on Patterning in the Focused Ion Beam Deposition Process

김윤제,김준현 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

This paper describes the interaction of the operation parameters during the focused ion beam (FIB) deposition process using an organo-metallic (C) precursor gas. Under the fine beam condition (30 kV, 40 nm beam size, etc.), the in fluences of the on-stage control parameters, such as the dwell time, beam overlap, incident beam angle relative to the tilted surface, minimum frame time and pattern size, on the FIB micro-deposition process were investigated by using deposition tests based on the design of five factors and four levels of L16(45). The process analysis was examined with respect to the deposited dimensions and the shapes of the single- pattern. Throughout the singlepatterning process, optimal conditions were selected. Additional procedures for multi-patterning deposition are presented to show the effect of on-stage parameters on the processing results. The analysis provided the sequential beam scan method and the aspect-ratio had the most significant in uence on FIB processing in multi-patterning deposition. The bit-mapped scan method was more efficient than the one-by-one scan method for obtaining a high-aspect ratio (height/width > 1) patterns. In the nano-scale gap, the one-by-one scan method and optimized conditions were required for successful modifications. This paper describes the interaction of the operation parameters during the focused ion beam (FIB) deposition process using an organo-metallic (C) precursor gas. Under the fine beam condition (30 kV, 40 nm beam size, etc.), the in fluences of the on-stage control parameters, such as the dwell time, beam overlap, incident beam angle relative to the tilted surface, minimum frame time and pattern size, on the FIB micro-deposition process were investigated by using deposition tests based on the design of five factors and four levels of L16(45). The process analysis was examined with respect to the deposited dimensions and the shapes of the single- pattern. Throughout the singlepatterning process, optimal conditions were selected. Additional procedures for multi-patterning deposition are presented to show the effect of on-stage parameters on the processing results. The analysis provided the sequential beam scan method and the aspect-ratio had the most significant in uence on FIB processing in multi-patterning deposition. The bit-mapped scan method was more efficient than the one-by-one scan method for obtaining a high-aspect ratio (height/width > 1) patterns. In the nano-scale gap, the one-by-one scan method and optimized conditions were required for successful modifications.

Ga? 이온 빔 조사량에 따른 자기 조립 단분자막의 습식에칭 특성변화

노동선(Dong Sun Noh),김대은(Dea Eun Kim) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

As a flexible method to fabricate sub-micrometer patterns, Focused Ion Beam (FIB) instrument and Self-Assembled Monolayer (SAM) resist are introduced in this work. FIB instrument is known to be a very precise processing machine that is able to fabricate micro-scale structures or patterns, and SAM is known as a good etch resistance resist material. If SAM is applied as a resist in FIB processing for fabricating nano-scale patterns, there will be much benefit. For instance, low energy ion beam is only needed for machining SAM material selectively, since ultra thin SAM is very sensitive to Ga? ion beam irradiation. Also, minimized beam spot radius (sub-tens nanometer) can be applied to FIB processing. With the ultimate goal of optimizing nano-scale pattern fabrication process, interaction between SAM coated specimen and Ga? ion dose during FIB processing was observed. From the experimental results, adequate ion dose for machining SAM material was identified.

셰일 저류층 내 공극 구조 연구를 위한 표면 밀링

박선영 ( Sun Young Park ),최지영 ( Jiyoung Choi ),이현석 ( Hyun Suk Lee ) 한국암석학회·(사)한국광물학회 2020 광물과 암석 (J.Miner.Soc.Korea) Vol.33 No.4

비전통 저류층에서 에너지 자원의 회수율을 높이기 위해서는 저류층 내의 미세 공극 형태와 연결도 등을 포함하는 공극 구조 연구가 필수적이다. 본 연구에서는 셰일 저류층 내 나노스케일의 공극 구조 연구에 적합한 조건과 방법을 찾기 위해 집속 이온 빔 시스템(Focused Ion Beam, FIB)과 이온 밀링 시스템(Ion Milling System, IMS)을 이용하여 분석을 진행하였다. 셰일 저류층 내 공극 구조 연구를 위해 리아드 분지에서 획득된 A-068 시추공의 시료를 사용하였다. 각 시료마다 특성이 다르기 때문에 시료 전처리 방법과 조건을 달리하여 최적의 조건을 찾았고 FE-SEM을 이용하여 공극 이미지를 획득하였다. 연구 결과 국소 부위의 공극구조를 관찰하기 위해서는 FIB를 사용하여 시표 표면을 밀링 후 바로 공극 이미지를 얻는 것이 효율적이고 반면에 넓은 면적을 단시간에 밀링하여 여러 공극 구조를 관찰하기 위해서는 IMS를 이용해야 한다는 것을 확인했다. 특히 탄산염 광물 함량이 높고 강도가 큰 암석에 대해서는 FIB보다는 IMS를 활용하여 밀링을 수행해야 공극 구조 관찰이 가능하다는 사실이 밝혀졌다. 본 연구를 통해 셰일 저류층 내 공극 구조 관찰을 위한 방법이 정립되었으며 향후 이를 이용한 셰일 가스 저류층 시료 분석을 통해 공극의 크기나 형태가 셰일가스 회수 증진에 미치는 영향을 밝힐 수 있을 것이다. Understanding the pore structure including pore shape and connectivity in unconventional reservoirs is essential to increase the recovery rate of unconventional energy resources such as shale gas and oil. In this study, we found analysis condition to probe the nanoscale pore structure in shale reservoirs using Focused Ion Beam (FIB) and Ion Milling System (IMS). A-068 core samples from Liard Basin are used to probe the pore structure in shale reservoirs. The pore structure is analyzed with different pretreatment methods and analysis condition because each sample has different characteristics. The results show that surface milling by FIB is effective to obtain pore images of several micrometers local area while milling a large-area by IMS is efficient to observe various pore structure in a short time. Especially, it was confirmed that the pore structure of rocks with high content of carbonate minerals and high strength can be observed with milling by IMS. In this study, the analysis condition and process for observing the pore structure in the shale reservoirs is established. Further studies are needed to perform for probing the effect of pore size and shape on the enhancement of shale gas recovery.