Influence of water vapor on performance degradation and microstructural change of (La,Sr)(Co,Fe)O3-δ cathode

In this study, single cells employing a La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode were operated with a supply of humidified oxygen to the cathode at 1000°C for 100 h to investigate the influence of water vapor on the performance and microstructure of LSCF cathode. When a gaseous mixture of 20% H2O−80% O2 was supplied to the cathode, the performance of LSCF cathode continuously lowered during a discharge at 300 mA cm−2 for 100 h. Then, the microstructures of surface and cross-section of LSCF cathode were observed by scanning electron microscopy. The surface morphology was drastically changed by the discharge operation. A SrO layer was formed at the outermost surface of cathode, indicating that the strontium segregation was accelerated by water vapor. In response to this phenomenon, the formation amount of cobalt- and/or iron-based oxides enlarged inside the electrode. These microstructural and phase changes would be responsible for the performance deterioration of LSCF cathode

Alkylated alkali lignin for compatibilizing agents of carbon fiber reinforced plastics with polypropylene

金沢大学理工研究域生命理工学系As an alternative to petroleum-based compatibilizing agents, we developed lignin derivatives for compatibilizing agents of carbon fiber-reinforced plastics that have thermoplasticity. In this study, alkyl chains were introduced into alkali lignin at various ratios to optimize the compatibility of the lignin derivatives with both polypropylene and carbon fiber. The interfacial shear strength between the two materials was improved from 8.2 to 17.2 MPa by mixing with the optimized lignin derivative. The value is comparable to that achieved with a typical petroleum-based compatibilizing agent (18.3 MPa).Embargo Period 6 monthsThis paper has supplementary information

チュウオン サドウ ネンリョウ デンチヨウ デンカイシツ ト シテ ノ リュウサンエン オヨビ リンサンエン フクゴウタイ ニ カンスル ケンキュウ

京都大学0048新制・課程博士博士(工学)甲第14272号工博第3023号新制||工||1449(附属図書館)UT51-2008-T32京都大学大学院工学研究科物質エネルギー化学専攻(主査)教授 江口 浩一, 教授 小久見 善八, 教授 垣内 隆学位規則第4条第1項該当Doctor of EngineeringKyoto UniversityDA

Comparative Study on Performance Stability of Ni-Oxide Cermet Anodes under Humidified Atmospheres in Solid Oxide Fuel Cells

The influence of the oxide component in Ni–oxide based cermet anodes on the performance stability was examined at 1000℃ with a supply of highly humidified hydrogen, 40% H2O–60% H2. Three types of anodes were applied; Ni–samaria-doped ceria (Ni–SDC), Ni–yttria-stabilized zirconia (Ni–YSZ), and Ni–scandia-stabilized zirconia (Ni–ScSZ). Abrupt deterioration in performance was confirmed during constant current operation for the cells with Ni–YSZ and Ni–ScSZ anodes, accompanied with a drastic increase in ohmic resistance between the anode and reference electrode. In contrast, the performance of cell with Ni–SDC anode was pretty stable for 48 h. These differences in performance stability were significantly related to the local partial pressure of steam in the vicinity of the electrochemically active sites because the surface oxidation of nickel particles resulted in the deterioration. The microstructural changes in Ni–YSZ and Ni–SDC anodes upon discharge were also quantified by the dual–beam focused ion beam–scanning electron microscopy (FIB–SEM). The electrochemical behavior observed in each anode had a strong correlation with the anode microstructure such as triple phase boundary length and nickel particle size

Influence of Ni-Oxide Anode Thickness on Performance Stability in Internal Reforming of Methane for Solid Oxide Fuel Cells

Influence of the materials and cell configuration, especially anode thickness, on the performance stability was examined during long-term operation of solid oxide fuel cells (SOFCs) with humidified methane (S/C = 0.1) at 1000℃. Two kinds of anode materials were evaluated; i.e., Ni–yttria–stabilized zirconia (Ni–YSZ) and Ni–samaria-doped ceria (Ni–SDC). The thickness of anode was controlled to be ca. 10, 20, and 30 μm in this study. Deterioration in performance was observed during a constant current operation with 10 μm-thick Ni–YSZ anode. On the other hand, the cell performance with 20 and 30 μm-thick Ni–YSZ was stable for 20 h. These differences in performance stability were significantly related to the anode thickness. In addition, the same experiments were conducted for the cells employing Ni–SDC anodes. The cell performance was improved obviously during discharge for 20 h regardless of anode thickness. The improvement upon discharge is ascribable to an increase in catalytic activity of Ni–SDC and electronic conductivity of SDC, which is induced by the partial reduction of Ce4+ to Ce3+ under reducing atmospheres. Microstructural observation and Raman spectroscopy were also conducted for the anodes. The electrochemical behavior observed in each anode had a strong correlation with crystallinity of carbon deposited and deposition area

Dynamic Behavior of Segmented-in-Series Tubular Solid Oxide Fuel Cell upon Discharge

Dynamic behavior of the segmented-in-series tubular solid oxide fuel cell upon discharge was investigated. The cell performance decreased initially at 900℃, accompanied by the increase of ohmic resistance. Lower partial pressure of oxygen in the cathode resulted in a more severe decrease, whereas the gas displacement in the anode compartment did not induce such behavior. As the current was cut off, the ohmic resistance rapidly recovered toward the starting value before current load. The possible origin for this increase-recovery behavior of the ohmic resistance has been discussed based on the evaluation of oxygen partial pressure at the cathode/electrolyte interface and element interdiffusion between cathode and electrolyte