東北大学機関リポジトリTOUR

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Fabrication and Characterization of

Metal-Supported Solid Oxide Fuel Cells

著者

Zaka Ruhma

学位授与機関

Tohoku University

学位授与番号

11301甲第19384号

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東北大学博士学位論文

Fabrication and Characterization of Metal-Supported

Solid Oxide Fuel Cells

令和元年度

東北大学大学院環境科学研究科

先進社会環境学専攻

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Abstract

Metal supported solid oxide fuel cell (SOFC) is predicted to be highly promising in solving the problem of ceramic supported SOFC due to unique properties of metal to ceramic. Fabrication was studied in relation with change of macrostructural, microstructural, and material properties. Several fabrication method were tried with methods such as pulsed laser deposition, cold spraying, plasma spraying and sintering. Macrostructural changes were observed through the final shape of multilayered metallic-ceramic cell composite. Microstructural change was observed by quantifying measurable quantities such as grain size, pore size, and particle boundary size. It was found the heat transport condition of the container during sintering affect the resulting sintered multilayer structure. Keeping the SS/NiO-8YSZ/8YSZ multilayer temperature isothermally at sintering temperature of 1300o_{C up to 5 hour cause the final}

microstructure of stainless steel to beyond final stage of full sintering or involving melting phenomena. Bulk porosity and surface porosity of the stainless steel support were counted in order to present numerically the difference of the state of sintering between the surface and the bulk. Sample with best surface porosity with 5.5 gr pore former was able to be tested and showing the maximum power density of 10 mW/cm2_{at 700}o_{C. However, long}

term performance testing of the resulted multilayer structure has not been tested. Furthermore, it is well known that the diffusion barrier layer would be needed for preventing catastrophic interdifussion degradation which will enlarge TEC mismatch between layers.

Competing with sintering method in its ability to be mass produced, was plasma spraying method which can be operated with robotic arm. In order to see the feasibility of the metal supported cell, Kawada Lab made a joint research with a Japanese coating company, Tocalo Co., Ltd.. The joint research began by testing the permeability of 8YSZ electrolyte deposition into sintered NiO-8YSZ. The plasma sprayed anode supported half-cell showing best impermeability was checked by impedance testing. The result showed that improvements were needed to fabricate fully dense and reliable electrolyte. Escalating the work to metal supported solid oxide fuel cell (MS-SOFC), plasma sprayed anode layer was made by atmospheric plasma spraying (APS). Considering the layer dimension change phenomena during operation cycle, dilatometry and laser profiling were done from room temperature to operating temperature. This data will help the estimation of how large is the mechanical stress caused by the reduction and oxidation of anode layer. In its first trial of fabricating MS-SOFC, Tocalo Co., Ltd. was able to integrate porous metal support with APS plasma sprayed NiO-8YSZ anode and SPS-APS plasma sprayed 8YSZ electrolyte into a MS-SOFC half-cell. Testing the half-cell MS-SOFC with Ag

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cathode showed mixing of hydrogen from anode and cathode occurred as temperature increased about 50o_{C during operation at 650}o_{C. Later, it was decided from the quality of}

microstructure that APS Plasma Spraying method will be used instead of SPS plasma spraying method. In its later trials of making MS-SOFC, MS-SOFC full cell were able to be fabricated with LSCF6428 cathode. Compared with previous, MS-SOFC half-cell which fabricated by SPS plasma spraying method, this MS-SOFC full-cell made by plasma spraying showed better leakage condition in its initial testing. However, clear sample behavior resulted from leakage was clearly observed after the sample was reheated again for second testing. The last trials were the variation of samples condition with different substrate heating, it showed as the substrate heated up, the cell was showing better permeability. It was important that even the testing results showed that no sample electrolyte was reliable, it was known that the electrode resistance showed fairly low resistance under low porosity. Further study of measuring the resistance of plasma sprayed layer resistance was done by symmetrical cell setup. The results showed that for both cathode and anode part, the electrode resistances were preceded by large interfacial resistance. The cause of this interfacial resistance was still unclear. One possible guess was this caused by micro-scale surface disintegration between anode particles and electrolyte surface.

Problem with SOFC multilayer structure is its degradation phenomena caused by load given to the cell during operation. Loads such as material degradation, interlayer interaction degradation, mechanical load in sealing; all of them, can contribute in change of the layer stresses. Therefore, measuring stresses on sample will help the observation of cell load or degradation process. Two methods promising to be used to measure residual stress are Raman and XRD methods. In Raman method, self-made data reference need to be made in order to be able to quantify the amount of stress remained on layer. In 8YSZ electrolyte, it turned out the cubic peak change with stress was not observable. From this result, the study of Raman method cannot be used for 8YSZ electrolyte material. The second method is XRD sin2 psi method, by changing the psi angle, it was possible to see change of interlattice distance change between plane compared to unstressed condition. Therefore, it was possible to measure the layer stresses by using XRD sin2 psi method. This method needed two hours of data retrieving time in order to measure the residual stress, while real-time residual stress measurement is needed. XRD cos α method was thought to be able to solve this issue of real-time measurement. This XRD cos α method was used to demonstrate the cell warpage condition to the stressed remained on electrolyte. Finally, XRD cos α method was able to be integrated with high temperature system thus high temperature XRD measurement of residual stress of SOFC was possible.

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Chapter 1: Introduction

1.1 Introduction to Solid Oxide Fuel Cell (SOFC) 1.1.1 Why Fuel Cells?

World energy demand currently has not been fulfilled fully and majority of the counter supplies were coming from fossil fuels [1]. Fuel cell is touted as one solution to increase the fuel to electricity conversion efficiency and to maximize the use of renewable energies by stabilizing their short- and long-term fluctuations.

1.1.2 Solid Oxide Fuel Cell

Currently, efficiency higher than 60 % LHV has been achieved with a 100 kW class system along with1.5 kW class system [2, 3]. Japan has commercialized a household SOFC system called “ENEFARM Type-S” which sold already about hundred thousand units.

1.1.3 Operating Principle of Solid Oxide Fuel Cell [4]

Due to conduction of oxygen ion in an SOFC cell, the reactions in electrodes are cathode side O₂+4e-_→2O

(1.1) anode side 2H₂+2O2-→2H₂O+4e- _(1.2)

the resultant of the reaction is

2𝐻₂+ 2𝑂2−_{→ 2𝐻}

2𝑂 (1.3)

1.2 Metal Supported Solid Oxide Fuel Cell

As operating temperature goes down, dense metal interconnect can be used. Further use of porous metal as a structural support was proposed, therefore reduced cost in fabrication and better mechanical support was expected [5].

1.3 Thesis scope

In this thesis, MS-SOFC is aimed to be fabricated at low cost and having sufficient performance. There are several issue to be solved in its fabrication depending on its routes. In this thesis, we study the fabrication using tape casting, and thermal spraying. Besides, structure and mechanical properties evolution during fabrication are also studied.

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Chapter 3 reports fabrication and characterization of MS-SOFC by plasma spraying. Chapter 4 discusses methods for stress distribution measurement.

Chapter 5 summarizes the results and discussions made in Chapters 2 to 4, and concludes suggesting guidelines for a better fabrication method of an MS-SOFC with high performance.

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Chapter 2: Fabrication and Investigation of MS-SOFCs using Tape

Casting

2.1 Introduction

The laminated layers can be co-sintered in a single heat treatment. In order to reach desired microstructural features, sintering strategy need to be determined such as using a single co-sintering or multi stage sintering.

2.2 Review on Tape Casting and Co-sintering Technologies for MS-SOFC 2.2.1 Wet Ceramic Method: Tape Casting

It is considered that tape casting main advantage is to produce large area of thin flat layer of ceramic or metallic sheets at high production rate continuously (continuous casting) [6].

2.3 Experimental Section

In preparing the MS-SOFC, in order to fabricate successfully any kind of cell configuration by route of co-sintering, clarification need to be made regarding the fabrication process such as effect of binder, pore former, furnace condition, and soon. The varied materials then sintered to produce half-cell MS-SOFC. Electrochemical testing was done to check its performance.

2.4 Conclusions

We studied the effect of change of pore former amount on stainless steel slurry on resulted half-cell flatness. We confirmed that the pore former amount on stainless steel changed the half-cell multilayer sintering behavior. By controlling the amount of pore former on the stainless steel, flatness of the half-cell can be controlled.

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Chapter 3: Fabrication and Investigation of MS-SOFC using Plasma

Spraying

3.1 Introduction

Successful fabrications of SOFC using thermal spraying have been reported where various types of metal substrates were used. However, limitations in microstructure quality, i.e. electrolyte gas tightness is considered to be a major obstacle to be solved. [7]. Experiment approaches will be done by depositing electrolyte under various plasma spraying parameter by Tocalo Co., Ltd.. Electrochemical response at various temperature condition will be done in order to evaluate the fabricated MS-SOFC.

3.2 Review on Fabrication of MS-SOFC by Thermal Spraying 3.2.1 Thermal Spraying

Thermal spray composed of spray gun and particles for deposition. Therefore depending on type of heat source, the name of the spraying method is stemmed from. For instance, the use of plasma gun give the method to be plasma spraying. Numerous successful fabrication of MS-SOFC by using plasma spraying reported by Tucker et al [7].

3.3 Outline of Experiments

Fabrication of MS-SOFC by Thermal Spraying were done through two methods: 1). atmospheric plasma spraying (APS) and 2). suspension plasma spraying (SPS). Those three methods were done by Tocalo Co., Ltd.. Electrolyte consisting of 8YSZ was chosen and deposited by Tocalo Co., Ltd. by APS and SPS. As for anode, nanostructured powder of NiO-8YSZ was used.

3.4 Results and Discussion: Anode Supported Half-cell Made by Plasma Spraying Dense sintered electrolyte was used to check the oxygen sensor voltage where no leak occurred, the value is about -0.90 V.Aas air was introduced into the support chamber the voltage lowered from about -0.80 V to -0.10 V. It means that the partial pressure of oxygen on electrolyte chamber was increased from 1.95588E-10 ppm bar to 3000 ppm bar. This increase showed that the leakage occurred on all of the samples.

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3.5 Results and Discussion: Metal Supported Half-cell Made by APS and SPS Plasma Spraying

3.5.1 Fabrication of NiO-8YSZ Layer on Porous Substrate

The fabricated layer of NiO-8YSZ and the nanostructured composite powder used during plasma spray deposition. The powder used in the fabrication were shown to have agglomeration particle size of about 10 to 50 um.

3.5.2 Metal Supported Half-cell Microstructure as Fabricated

Two samples of MS-SOFC half-cell were fabricated by giving the difference on electrolyte fabrication route. The first electrolyte was made by route of APS as explained in AS-SOFC. The second was the newly fabricated sample SPS.

3.5.3 Electrochemical Testing of Metal Supported Half-cell Made by Plasma Spraying OCV of APS Half-cell MS-SOFC showed zero value during testing at both 650o_{C and}

750o_{C. This zero value was thought because of gas leakage on electrolyte. Following}

OCV was showing zero value, measurement was stopped. The reason of this leakage can be seen where visible crack can be observed.

3.6 Results and Discussions: Metal Supported Full-cell Made by APS Plasma Spraying 3.6.1 Metal Supported Full-cell Microstructure as Fabricated

LSCF6428 was deposited in which the resulted microstructure was same as the NiO-8YSZ, by using APS. The microstructure showed dense layer consisted of thin splat microstructure similar as NiO-8YSZ microstructure. The density of both electrodes were the same about 4%. Electrolyte successfully deposited without line crack between interfaces.

3.6.2 Electrochemical Testing of Metal Supported Full-cell Made by Plasma Spraying The full cell MS-SOFC was tested for its OCV and impedance to check its gas leakage. First full-cell sample, named as sample no. 4, was checked in two-cycle separated by cooling into room temperature. First sample testing showed that the OCV was about 0.3 V below theoretical OCV.

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3.7 MS-SOFC Symmetrical Cell Testing

3.7.1 MS-SOFC Cathode Symmetrical Cell Testing

It was observed that the distribution of Ni and YSZ on the deposited microstructure that the surface showed nano distribution of Ni and YSZ. Symmetrical cell consisted of LSCF|GDC|LSCF was fabricated by Tocalo Co., Ltd. 10 mm diameter of LSCF was deposited on top of 15 mm diameter of GDC.

3.7.2 MS-SOFC Anode Symmetrical Cell Testing

It was observed that electrode resistances of the MS-SOFC half cell and full cell were low enough even though the observed OCV below the theoretical value. EDS mapping also show nano distribution of Ni and YSZ elements despite of large deposited particle size about ratio size of 30 um and 10 um.

Similar with the case of cathode supported cell, it showed high interfacial resistance and several observable low electrode resistances.

3.8 Conclusions

Observation of OCVs and impedances testing were done on AS-SOFC half-cell, MS-SOFC half cell, and MS-MS-SOFC fuel cell. The porosity on electrolyte can be solved also by using high torch speed where temperature fluctuation can be reduced. Increased substrate heating showed to increase permeability of the cell. Further symmetrical cell testing of both cathode and anode showed that the symmetrical cell suffered from high interface resistance.

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Chapter 4: Stress Distribution Measurement

4.1 Introduction

Considering of its non-destructive nature during testing and its ability to measure micro-stress in a structure, XRD and Raman method are chosen to be applied in the residual stress study for SOFC application. In its ability for measuring macro-stress in a structure, curvature method is seen as an appropriate method to be used in SOFC application. Therefore, XRD, Raman, and curvature method will be studied to be applied for residual stress measurement in SOFC fabrication and operation.

4.1.1 XRD sin2𝜓 Method

(XRD) sin2𝜓 technique is chosen to be studied due to its ability to measure micro-stress and it availability [8, 9]. XRD is one of nondestructive techniques that can be used to measure residual stress with the high potential to be used in portable setting

4.1.2 XRD cos α Method

XRD cos α method uses a different approach in measuring residual stresses. Difference from XRD sin2𝜓 method, XRD cos α method do not need tilting of sample. In XRD cos α, Debye-Scherrer (D-S) rings were observed by an image plat during measurement [10].

4.1.3 Raman Shift Method

In case of SOFC related materials, it was reported that for tetragonal YSZ, it was possible to attain linear relationship of Raman peak shift and compressive stress [11]. This finding give hope that as 8YSZ that is usually used in SOFC application can benefit from Raman peak shift data for measuring residual stress. The difficulty of measuring Raman peak shift data was on the overlapping of cubic and tetragonal peak [11]. However, the explanation of the difficulty was not explained in detail. The possibility to use Raman method for residual stress measurement of 8YSZ is still open.

4.1.4 Residual Stress Generation in Operation

A reduction of residual stress due to difference in thermal expansion at high temperature is one of the advantage in introducing porous metal substrate into SOFC cell [12]. The strain caused by the reaching of new equilibrium between different expanded materials will result in lower stress porous metal compared to the dense one, thanks to its lower

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stiffness [12, 13]. This is demonstrated in work of joining between stainless steel/stailess steel foam/alumina [12, 14]. Therefore a thorough understanding of porous metal contribution to residual stress change during operation is indispensable.

4.2 Residual Stress Measurement by Raman Method 4.2.1 Experimental

Peak shift in Raman profile can be related with stress contained in material surface such as reported by Limarga et al. [11] for the work of compressive stress in tetragonal 8YSZ. In tetragonal it was easy to distinguish the peak shift fitting since all of the peak belong to tetragonal peak. However, it was reported that due to mixing of cubic and tetragonal peak, it was impossible [15] to measure the change in peak shift in order to measure the residual stress using Raman method for 8YSZ. However, due to the promising of quick measurement of residual stress using Raman method, the feasibility of Raman method to measure the 8YSZ residual stress was researched. A compression jig (5 cm x 5 cm) was used in order to give the desired mechanical stress. The stress was retrieved by using a typical strain gage on S45C steel cube (1 mm x 1 mm) attached to a 8YSZ cube (1 mm x 1 mm). The strain gage was connected to an amplifier therefore strain data can be obtained. By using known young modulus of S45C stainless steel, the stress given can be recorded. 4.2.2 Results and Discussion

The results were shown on the raw Raman profile of 8YSZ showed similar peak profiles. This was confirmed after height normalization. There were two possible calibrations in order to measure residual stress accurately. Two methods of silicon single crystal and neon light calibration were done to calibrate the Raman peak shifts. However, effort to single out cubic peak was reached the conclusion that no physical phenomena can be extracted from trialed fitting using both calibration methods as the data scattered and no tendency was showing.

4.3 Residual Stress Measurement by XRD sin2 𝜓 method 4.3.1 Experimental

The measurement of XRD sin2 𝜓 method was based on Bragg`s law. Selected samples were put on the XRD D8 Advance stage and swung by 𝜓 angle form 0o_{to 75}o_{. Variation}

of residual stress can be expected because of the sample was pseudo-polycrstalline, therefore rotation along phi axis was given between 0o and 45o. peak position (111) of 8YSZ electrolyte was selected to evaluate residual stress.

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4.3.2 Results and Discussions

Successful measurement of residual stresses were done on sintered layer of 8YSZ and plasma sprayed layer of 8YSZ. Sintered layer showed large variation of residual stress when the sample was rotated. This indicated that the sintered layer crystal orientation was not perfectly random. Residual stress shown on sintered layer was tensile stress below the fracture strength of 8YSZ. However, as for plasma sprayed sample showed small variation of residual stress when sample was rotated. This indicated that the plasma sprayed layer crystal orientation was nearly random. However, long experiment time of 2 hours to obtain a single measurement made it unsuitable for real-time residual stress measurement. Therefore, this method was not studied further.

4.4 Residual Stress Measurement by XRD cos 𝛼 Method 4.4.1 Experimental

The Pulstec-u360 (Pulstec, Japan) employed a special Debye ring measurement ability. This Debye ring measured by the Pulstec-u360 area detector able to quantify amount strain in the sample by comparing it with change in strain with cos 𝛼.

4.4.2 Results and Discussions

The magnitudes of error measurement for stainless steel layer are so large because the machine limitation which grain or particle size has to as small as around 1 um; here, stainless steel powder with particle size around 40 um is used. As for magnitudes of error measurement for 8 mol% YSZ some are below 50% which shows its uncertainty. Considering a simple bilayer model of SS430L and 8YSZ without NiO-YSZ as an interlayer, when SS430L is dominating the shrinkage but constrained by 8YSZ (bilayer bend to steel) then compressive residual stress on 8YSZ will be retained.

Ignoring the contribution of NiO-YSZ, the model applies in fairly some amount of cases to warpage behavior, where sintered layers bent to 8YSZ will have tensile residual stress on 8YSZ and vice versa. As a comparison, residual stress measured on plasma spraying was seen that as for 8YSZ plasma sprayed sample deposited on metal supported, substrate heating has no effect on residual stress resulted on 8YSZ surface

4.5 Conclusions

Residual stresses measurements were tried by using Raman method and XRD method. It was clear that by using Raman method, the restrictive nature of 8YSZ peak fitting

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disallowed the further use of Raman method. As for XRD method it can be seen that sin2

𝜓 and cos 𝛼 method were tried. Sin2 _{𝜓 method need as long as 2 hours in measurement.}

Therefore, despite successful measurement using sin2_{psi method for both sintered cell}

and plasma sprayed cell, this method will not be tried further. Promising results were shown by XRD cos alpha method to measure residual stress on 8YSZ layers.

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References

[1] S. E. Hosseini and M. A. Wahid, "Hydrogen production from renewable and sustainable energy resources: promising green energy carrier for clean

development," Renewable and Sustainable Energy Reviews, vol. 57, pp. 850-866, 2016.

[2] U. Bossel, "Small scale power generation for road trucks with planar SOFC system," ECS Transactions, vol. 68, no. 1, pp. 193-199, 2015.

[3] F. Mueller, B. Tarroja, J. Maclay, F. Jabbari, J. Brouwer and S. Samuelsen, "Design, simulation and control of a 100 MW-class solid oxide fuel cell gas turbine hybrid system," Journal of Fuel Cell Science and Technology, vol. 7, no. 3, p. 031007, 2010.

[4] M. Boaro and A. S. Aricò, Advances in Medium and High Temperature Solid Oxide Fuel Cell Technology, Cham, Switzerland: Springer, 2017.

[5] I. Villarreal, M. Rivas, L. M. Rodriguez-Martinez, L. Otaegi, A. Zabala, N. Gomez, ... and Olave, "Tubular metal supported SOFC development for domestic power generation," ECS Transactions, vol. 25, no. 2, pp. 689-694, 2009.

[6] X. Zhu and W. Yang, Introduction to Mixed Ionic–Electronic Conducting Membranes, Springer, 2017.

[7] M. C. Tucker, "Progress in metal-supported solid oxide fuel cells: A review,"

Journal of Power Sources, vol. 195, no. 15, pp. 4570-4582, 2010.

[8] L. Pawlowski, The science and engineering of thermal spray coatings, John Wiley & Sons, 2008.

[9] P. J. Withers, "Residual stress: definition," in Encyclopedia of Materials: Science

and Technology, Elsevier, 2001, pp. 8110-8113.

[10] K. Tanaka, "The cosα method for X-ray residual stress measurement using two-dimensional detector.," Mechanical Engineering Reviews, vol. 6, no. 1, pp. 18-00378, 2019.

[11] A. M. Limarga and D. R. Clarke, "Piezo‐spectroscopic coefficients of tetragonal‐ prime yttria‐stabilized zirconia," Journal of the American Ceramic Society, vol. 90, no. 4, pp. 1272-1275, 2007.

[12] R. Goodall and A. Mortensen, "Porous metals," in Physical Mettalurgy, Elsevier, 2014, p. 2399.

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[13] T. Jarvis, W. Voice and R. Goodall, "The bonding of nickel foam to Ti–6Al–4V using Ti–Cu–Ni braze alloy," Materials Science and Engineering: A, vol. 528, no. 6, pp. 2592-2601, 2011.

[14] A. A. Shirzadi, Y. Zhu and H. K. D. H. Bhadeshia, "Joining ceramics to metals using metallic foam," Materials Science and Engineering, vol. 496, no. 1-2, pp. 501-506, 2008.

[15] J. Malzbender, R. W. Steinbrech and L. Singheiser, "A review of advanced techniques for characterising SOFC behaviour," Fuel Cells, vol. 9, no. 6, pp. 785-793, 2009.

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List of Publications

1. Zaka Ruhma, Keiji Yashiro, Fumitada Iguchi, Itaru Oikawa (2), Yoshiaki Hayamizu, Hitoshi Takamura, Tatsuya Kawada, “Degradation Study of Tape Casted Metal

Supported Solid Oxide Fuel Cell”, The 13th EUROPEAN SOFC & SOE FORUM, B-1303, Lucerne, Switzerland, 3rd– 6th July, 2018.

(Conference proceedings)

2. Zaka Ruhma, Keiji Yashiro, Itaru Oikawa, Hitoshi Takamura, Tatsuya Kawada, “Metal Supported SOFC Fabricated by Tape Casting and Its Characterization: A Study for Co-sintering Process”, J. Eng. Technol. Sci,(2020) (To be published)

Conference Abstracts

1. Zaka Ruhma, Keiji Yashiro, Fumitada Iguchi, Kazuhisa Sato, Tatsuya Kawada, “Residual Stress Measurement of 8 mol% YSZ film electrolyte”, SOFC Japan 26th, Poster No. 156C, Tokyo, Japan, Date 14-15th_{December 2017.}

2. Zaka Ruhma, Keiji Yashiro, Fumitada Iguchi, Kazuhisa Sato, Tatsuya Kawada, “Residual Stress Measurement of 8 mol% YSZ Coating for SOFC Application”, 42nd International Conference and Expo on Advanced Ceramics and Composites,

Presentation No. ICACC-S3-P015-2018, Daytona Beach, Florida, United States of America, 21th-26th January, 2018.

3. Zaka Ruhma, Keiji Yashiro, Fumitada Iguchi, Itaru Oikawa (2), Yoshiaki Hayamizu, Hitoshi Takamura, Tatsuya Kawada, “Degradation Study of Tape Casted Metal

Supported Solid Oxide Fuel Cell”, The 13th EUROPEAN SOFC & SOE FORUM, B-1303, Lucerne, Switzerland, 3rd– 6th July, 2018.

4. Zaka Ruhma, Keiji Yashiro, Fumitada Iguchi, Kazuhisa Sato, Itaru Oikawa, Yoshiaki Hayamizu, Hitoshi Takamura, Tatsuya Kawada, “Fabrication and Characterization of Metal Supported Solid Oxide Fuel Cell”, The 19th Korea-Japan Students' Symposium, Poster No. 28, Daejeon, South Korea, 08th November 2018.

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5. Zaka Ruhma, Keiji Yashiro, Itaru Oikawa, Yoshiaki Hayamizu, Hitoshi Takamura, Tatsuya Kawada “Fabrication of Metal Supported Solid Oxide Fuel Cell”, The 27th Symposium on Solid Oxide Fuel Cells in Japan, Presentation No. 209B, Tokyo, Japan, 14th_{December 2018.}

6. 駒谷拓己、Zaka Ruhma、八代圭司、川田達. “金属支持型固体酸化物型燃

料電池のセル内の応力状態評価”, ECSJ Fall Meeting, Kofu Campus, Japan, 5h

September 2019.

6. Zaka Ruhma, Keiji Yashiro, Itaru Oikawa, Hitoshi Takamura, Tatsuya Kawada, “Metal Supported SOFC Fabricated by Tape Casting and Its Characterization: A Study for Co-sintering Process”, 7th International Conference on Fuel Cell & Hydrogen

Technology in conjunction with Innovation in Polymer Science & Technology,

Presentation No. ICFCHT-044, Bali, Indonesia, 16th_-19th_{October 2019.}

7. 駒谷拓己，Zaka Ruhma，及川格，八代圭司，高村仁，川田達也, “金属支持型固体酸化物形燃料電池の応力評価”, SOFCJapan, Presentation No.160C, Tokyo, Japan, Date 12122019

8. Zaka Ruhma, Takumi Komaya, Keiji Yashiro, Itaru Oikawa, Hitoshi Takamura, Tatsuya Kawada, “Co-sintering Study of Stainless Steel Supported Ni-8YSZ/8YSZ Cell”, SOFCJapan, Presentation No.213B, Tokyo, Japan, Date 13122019

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ACKNOWLEDGEMENT

Author acknowledges that this work is impossible to be done with out the help of the people involved during the Ph.d work. Author would like to thank Kawada sensei and Yashiro sensei as the main supervisor for my study. Author would like to thank the administration help from Kawamura san and GSES Kyomu Gakari, Akasaka san, Sasahara san, and others. Author would like to thank all of the Kawada Laboratory Colleague: all of the students for very sincere help and Watanabe san especially as a very kind and helpful Lab staff. Author would like to thank Iguchi sensei, Sato sensei, Takamura sensei, Oikawa sensei, Matsubara sensei, Hashida sensei, Ogawa sensei, Wesley san, Okuda san and Sakamoto san, Hatakeyama sensei, Hayamizu san, Tocalo Co. Ltd. fellows and others that help directly with author experiment.

There are a lot of collaboration has been done between Kawada Lab, Iguchi Lab, Hashida Lab, Takamura Lab, Tocalo Co. Ltd. and Ogawa Lab. Author felt grateful with so many study experience in Tohoku University. During study, author were given chance to do conference abroad to Indonesia, Switzerland, and USA. It was an uncountable favor that has been given to a young individual such as the author.

Finally, and all of people in daily lives, and especially my family, I would like to thank them for their understanding in lack of author time given to them due to author busyness.