Ikwhang Chang

Fabrication of low-temperature solid oxide fuel cells with a nanothin protective layer by atomic layer deposition

Anode aluminum oxide-supported thin-film fuel cells having a sub-500-nm-thick bilayered electrolyte comprising a gadolinium-doped ceria (GDC) layer and an yttria-stabilized zirconia (YSZ) layer were fabricated and electrochemically characterized in order to investigate the effect of the YSZ protective layer. The highly dense and thin YSZ layer acted as a blockage against electron and oxygen permeation between the anode and GDC electrolyte. Dense GDC and YSZ thin films were fabricated using radio frequency sputtering and atomic layer deposition techniques, respectively. The resulting bilayered thin-film fuel cell generated a significantly higher open circuit voltage of approximately 1.07 V compared with a thin-film fuel cell with a single-layered GDC electrolyte (approximately 0.3 V).

Bendable polymer electrolyte fuel cell using highly flexible Ag nanowire percolation network current collectors

This study reports a polymer electrolyte fuel cell based on polydimethylsiloxane coated with a flexible current-collecting layer of Ag nanowire percolation networks. The reactive area of the bendable fuel cell was 9 cm2 and showed the maximum absolute power of 639 mW (the power density was 71 mW cm−2) under various bending conditions. Impedance spectra of the operating cell revealed that ohmic and Faradaic resistances decreased under the bent condition. Overall, the degree of bending improves the cell performances. The structural modeling result showed that decrease of the resistance and corresponding performance enhancement were due to the increased compressive force normal to the membrane electrode assembly, which was investigated through finite element simulation of the stress within the bendable fuel cell.

Designing and manufacturing of Formula SAE-Hybrid racecar for a new engineering education program

This paper addresses the preparation and participation of new collegiate design series “Formula SAE-hybrid (FSAE-Hybrid)” under society of automotive engineers (SAE). These participation processes of FSAE-Hybrid are required various engineering knowledge as well as practical skills in terms of the design engineering education in university. The car is built in an open-wheel, single seat, plug-in hybrid racecar. The design issues of FSAE-Hybrid emphasize powertrain innovation and fuel efficiency in high hybrid power management. It is next generation vehicle, even though base model of FSAE-Hybrid is based on FSAE regulations and rules. Also, the several processes of competition, design, cost, and sale presentation, required the team management and team-work for university students. Students would utilize the software (CATIA and Pro-E) of computer-aided design in order to design chassis and suspension, including especially upright. Based on a design part and a frame, they should analyze stress distribution of each part and flow visualization of intake as well as exhaust. Also, the integrated vehicle is simulated by estimating the estimation of fuel-economy of hybrid management (supervisory control logic) via Matlab/Simulink and vehicle dynamics via Adams program.

Influence of a platinum functional layer on a Ni-Ce0.9Gd0.1O1.95 anode for thin-film solid oxide fuel cells

A Pt functional layer was deposited between a Ni-Ce0.9Gd0.1O1.95 (50 wt. % Ni) anode and an 8 mol. % yttria-stabilized zirconia electrolyte in order to enhance the performance of a thin film solid oxide fuel cell. By inserting this ultrathin functional layer, the ohmic impedance of the single cell was significantly reduced, and the maximum power density was increased by a factor of ∼1.55. However, excessive deposition of the Pt functional layer caused ionic conduction pathway blocking between the yttria-stabilized zirconia and Ni-Gd0.1Ce0.9O1.95 (Ni-GDC), deactivating the Ni-GDC as a mixed ionic and electronic conducting anode. As a result, both the ohmic impedance and anodic faradaic impedance were increased after introduction of excessive Pt functional layer, and the maximum power density was also reduced.

Fabrication of Solid Oxide Fuel Cells via Thin Film Techniques

Fabricating electrolyte with thin film is one of various methods of lowering the operation temperature for solid oxide fuel cell (SOFC). Because the major polarization of SOFCs is ohmic loss, many groups have tried to fabricate a thin film electrolyte – some proton conducting material that has the conductivity of a couple of orders higher than oxygen conducting one. We have investigated the synthesis of Membrane Electrode Assembly (MEA) including Yttria-doped Barium Zirconate(BYZ) thin film electrolyte via thin-film processes such as Pulsed Laser Deposition and Sputtering. Another approach to lower the operation temperature of SOFCs is the bi-layer structure electrolyte. The functional layer via thin film deposition could guarantee minimum power density loss and stable operation. After the study of Atomic Layer Deposition (ALD) condition to deposit Yttria Stabilized Zirconia (YSZ) on Gadonilia doped Cerate (GDC) substrate, GDC/YSZ bi-layered electrolyte button cells showed higher OCV and larger limiting current with 100nm YSZ ultra thin film. The performance improvement might be attributed to the function of electron blocking and cutting off the reducible gas.

Fabrication of Thin Solid Oxide Film Fuel Cells

Recently, thin film processes for oxides and metal deposition, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), have been widely adapted to fabricate solid oxide fuel cells (SOFCs). In this paper, we presented two research area of the use of such techniques. Gadolinium doped ceria (GDC) showed high ionic conductivity and could guarantee operation at low temperature. But the electron conductivity at low oxygen partial pressure and the weak mechanical property have been significant problems. To solve these issues, we coated GDC electrolyte with a nano scale yittria-doped stabilized zirconium (YSZ) layer via atomic layer deposition (ALD). We expected that the thin YSZ layer could have functions of electron blocking and preventing ceria from the reduction atmosphere. Yittria-doped barium zirconium (BYZ) has several orders higher proton conductivity than oxide ion conductor as YSZ and also has relatively high chemical stability. The fabrication processes of BYZ is very sophisticated, especially the synthesis of thin-film BYZ. We discussed the detailed fabrication processes of BYZ as well as the deposition of electrode. This paper discusses possible cell structure and process flow to accommodate such films.

Parametric study of Y-doped BaZrO3 thin film deposited via pulsed laser deposition

This study investigates the microstructure morphologies of Y-doped barium zirconate (BZY) thin films via a pulsed laser deposition (PLD) process. BZY thin film crystallinity was investigated at different substrate temperatures in a PLD chamber. BZY thin films deposited under 0.013 mbar of oxygen pressure are highly dense regardless of the substrate temperature (25 °C ≤ T ≤ 600 °C), while those deposited at low temperature (T ≤ 200 °C) have porous structures at an oxygen partial pressure of 0.13 mbar. In addition, BZY thin films deposited at 0.26 mbar in low/intermediate temperature ranges (25 °C ≤ T ≤ 400 °C) have porous and columnar structures. Regardless of the chamber pressures, BZY thin films with dense structures can be obtained when the substrate temperature exceeds 500 °C.

EFFECT OF NICKEL CONTENTS ON THE MICROSTRUCTURE OF MESOPOROUS NICKEL OXIDE/GADOLINIUM-DOPED CERIA

The effect of NiO contents on the microstructure of mesoporous NiO-Gd0:25Ce0:75O2� x (NiO-GDC) composite for intermediate temperature solid oxide fuel cells (IT-SOFC) was investigated. Mesoporous NiO-GDC powders with different NiO contents were synthesized by self-assembly hydrothermal method using tri-block copolymer, Pluronic F127, as a structure directing agent. Grain growth/agglomeration behaviors of NiO particles and changes of mesoporous structure of GDC particles were characterized by microstructural analyses. NiO-GDC powders were composed of GDC nano particles with ordered mesopore inside the particles and octahedral NiO grains with truncated-edges. As the amount of NiO increases, specific area value of mesoporous NiO-GDC was decreased, and the agglomeration/growth behavior of NiO grains was accelerated.

Study on Ohmic Resistance of Polymer Electrolyte Fuel Cells Using Current Interruption Method

최근 전인류가 당면한 화석에너지 고갈문제는 신∙재생에너지 연구개발의 필요성을 높이고 있다. 이들 중 고효율이며 친환경적 특성을 모두 갖춘 연료전지는 넓은 적용 범위를 가지며 현재의 화석에너지 체계를 대신할 만한 유력한 후보 군으로 각광 받고 있다. 이들 연료전지 중 작동 온도가 비교적 상온에 가깝고, 시동 시간이 짧은 고분자전해질 연료전지는 활발한 물리화학적 실험 및 시뮬레이션 연구들을 바탕으로 최근 상용화를 앞두고 (있다.1~3) 이와 관련하여 연료전지의 저항을 측정하기 위한 대표적인 방법으로는 교류 임피던스 측정법과 전류차단법이 있다.

Study of Air-Breathing Polymer Electrolyte Membrane Fuel Cell Using Metal-Coated Polycarbonate as a Material for Bipolar Plates

In this study, a metal-plated polycarbonate was adopted as a material for bipolar plates in a polymer electrolyte membrane fuel cell (PEMFC). The coated layers included 40--thick copper, 10--thick nickel, and 0.3--thick gold that respectively played the roles of current conduction, adhesion between copper and gold, and minimization of surface corrosion. The maximum power of the air-breathing PEMFC with polycarbonate bipolar plates was , which was similar to that of graphite bipolar plates. Finally, the maximum power of a 12-cell stack of polycarbonate bipolar plates was , and it had an operating time of 12 h. Therefore, this was considered a suitable material for bipolar plates in PEMFCs.