Hwan Moon

Quantitative analysis of microstructure and its related electrical property of SOFC anode, Ni–YSZ cermet

Abstract The microstructural and electrical properties of Ni–YSZ composite anode of solid oxide fuel cells (SOFC) were investigated. We measured the electrical conductivity via 4-probe DC technique as a function of Ni content (10–70 vol.%) in order to examine the correlation with the microstructure of Ni–YSZ cermet. Image analysis based on quantitative microscopic theory was performed to quantify the microstructure of Ni–YSZ composite. The size and distribution, contiguity and interfacial area of each phase or between the phases could be obtained from the image analysis. According to image analysis, contiguity between the same phases was simply dependent on the amount of that phase itself while the contiguity between different phases was greatly influenced by the amount of Ni phase because the overall microstructural changes were mainly controlled by the coarsening of Ni phase. These similarly quantified microstructural properties were used for the characterization of the electrical properties of Ni–YSZ cermet.

Fabrication and Characterization of Anode-Supported Planar Solid Oxide Fuel Cell Manufactured by a Tape Casting Process

A planar anode-supported electrolyte was fabricated using a tape casting method that involved a single step cofiring process. A standard NiO/8YSZ cermet anode, 8 mol % YSZ electrolyte, and a lanthanum strontium manganite cathode were used for the solid oxide fuel cell unit cell. A pressurized cofiring technique allows the creation of a thin layer of dense electrolyte about 10 μm without warpage. The open circuit voltage of the unit cell indicated negligible fuel leakage through the electrolyte film due to the dense and crack-free electrolyte layer. An electrochemical test of the unit cell showed a maximum power density up to 0.173 W/cm 2 at 900°C. Approximated electrochemical properties, e.g., activation energy, Ohmic resistance, and exchange current density, indicated that the cell performance was significantly influenced by the electrode properties of the unit cell.

Fabrication and Characterization of Cu-Ni- YSZ SOFC Anodes for Direct Utilization of Methane via Cu pulse plating

The Cu-Ni-YSZ cermet anodes for direct use of methane in solid oxide fuel cells have been fabricated by electroplating Cu into the porous Ni-YSZ cermet anode. The uniform distribution of Cu in the Ni-YSZ anode could be obtained via pulse electroplating in the aqueous solution mixture of CuSO₄ㆍ5H₂O and H₂SO₄ for 30 min with 0.05 A of average applied current. The power density (0.17W㎝?²) of a single cell with a Cu-Ni-YSZ anode was shown to be slightly lower in methane at 700℃, compared with the power density (0.28W㎝?²) of a single cell with a Ni-YSZ anode. However, the performance of the Ni-YSZ anode-supported single cell was abruptly degraded over 21 h because of carbon deposition, whereas the Cu-Ni-YSZ anode-supported single cell showed the enhanced durability upto 52 h.

박막 테이프캐스팅과 동시소성에 의한 연료극 지지형 SOFC 단전지 제조

An anode-supported SOFC single cell having 5 ㎛ thin electrolyte was fabricated cost-effectively by tape casting, laminating, and co-firing of anode (NiO-YSZ), cathode (LSM-YSZ), and electrolyte (YSZ) components. The optimal slurry compositions of the green tapes for SOFC components were determined by an analysis of the mean diameter, the slurry viscosity, the tensile strength/strain of the green tapes, and their green microstructures. The single cells with a dense electrolyte and porous electrodes could be co-fired successfully at 1325~1350℃ by controlling the contents of pore former and the ratio of coarse YSZ and fine YSZ in the anode and the cathode. The single cell co-fired at 1350℃ showed 100.2 ㎽㎝?² of maximum power density at 800℃ but it was impossible to apply it to operate at low temperature because of low performance and high ASR, which were attributed to formation of the secondary phases in the cathode and the interface between the electrolyte and the cathode.