Hyunho Lee

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.

Electrical conductivity and defect structure of CeO2-ZrO2 mixed oxide

The electrical conductivity of CeO2-ZrO2 system was measured as functions of the temperature and oxygen partial pressure and of the composition. The ionic conduction was prevailing in the ZrO2 rich phase due to the increase of ionic defect concentration via homovalent doping effect. The enhancement of n-type electronic conductivity was observed in intermediate and CeO2 rich phase compared with pure CeO2, which originated either from homovalent doping effect or increase of electronic mobility due to the change of transport mechanism.

Electrical conductivity and defect structure of yttria-doped ceria-stabilized zirconia

AbstractThe electrical property and defect structure of 12 mro CeO –ZrO , which has been known for good mechanical and 22 thermal properties, were studied in order to investigate the possibility of its use as a solid electrolyte for electrochemicaldevice, like electrolyser, sensor and fuel cell. The electrical conductivity of 12 mro CeO –ZrO was greatly enhanced and 22 electrolytic domain boundary EDB was also extended to lowŽ. P with yttria doping, which were readily comparable with O 2 those of commercial electrolyte, YSZ, CSZ. Unlike normal stabilized zirconia, saturation point of electrical conductivityappeared at higher doping concentration 12–15 mŽ.ro yttria and the activation energy was not also changed seriously withdoping till 15 mro yttria doping. q2001 Elsevier Science B.V. All rights reserved. Keywords: Zirconia; Ceria; Yttria; Electrical conductivity; Defect structure 1. IntroductionIn the last few decades, zirconia-based ceramichas been studied with great interests for many appli-cation fields due to its good mechanical, chemicaland electrolytic properties. Especially, doped zirco-nia with a lower valence cation like Ca

Vision-based automatic real time inspection of power transmission line

To provide the electric power for people in easy circumstance, effective maintenance and monitoring operation of power transmission line is very important. However, until a recent date, most inspection of power transmission line has been performed by people. It may cause many problems. In this paper, we proposed the vision-based automatic real time inspection algorithm of the power transmission line using the inspection robot. It can guarantee the safety and performance than conventional inspection method. The experiments in the real power transmission line show its effectiveness which can distinguish normal and abnormal transmission line well. The proposed method can contribute to the economically effective maintenance and monitoring operation of power transmission line.

Vision-based absolute indoor point positioning in the hallway without image database

This paper proposes a method for the vision-based absolute point positioning in the hallway using a single camera without image database. Our vision-based absolute point positioning system has less than 1 m error with respect to the root mean square and 0.5 standard deviation.

Object recognition for vision-based navigation in indoor environments without using image database

This paper proposed recognizing methods of the indoor objects for the vision-based indoor navigation using the smartphone camera without using an image database. It is better realizable and cost-effective system than conventional system which uses an image database. In this proposed approach, we define the metrics to recognize indoor objects.

Detection of retinitis pigmentosa by differential interference contrast microscopy.

Differential interference contrast microscopy is designed to image unstained and transparent specimens by enhancing the contrast resulting from the Nomarski prism-effected optical path difference. Retinitis pigmentosa, one of the most common inherited retinal diseases, is characterized by progressive loss of photoreceptors. In this study, Differential interference contrast microscopy was evaluated as a new and simple application for observation of the retinal photoreceptor layer and retinitis pigmentosa diagnostics and monitoring. Retinal tissues of Royal College of Surgeons rats and retinal-degeneration mice, both well-established animal models for the disease, were prepared as flatmounts and histological sections representing different elapsed times since the occurrence of the disease. Under the microscopy, the retinal flatmounts showed that the mosaic pattern of the photoreceptor layer was irregular and partly collapsed at the early stage of retinitis pigmentosa, and, by the advanced stage, amorphous. The histological sections, similarly, showed thinning of the photoreceptor layer at the early stage and loss of the outer nuclear layer by the advanced stage. To count and compare the number of photoreceptors in the normal and early-retinitis pigmentosa-stage tissues, an automated cell-counting program designed with MATLAB, a numerical computing language, using a morphological reconstruction method, was applied to the differential interference contrast microscopic images. The number of cells significantly decreased, on average, from 282 to 143 cells for the Royal College of Surgeons rats and from 255 to 170 for the retinal-degeneration mouse. We successfully demonstrated the potential of the differential interference contrast microscopy technique’s application to the diagnosis and monitoring of RP.

Improved Multi-Functionality of Ni/YSZ Cermet Anode by Optimizing Fabrication Processes

Ni/YSZ cermet anode is required to simultaneously satisfy various properties as a key component of anode-supported type SOFC, since the cell performance is highly dependent upon anode properties. Ni/YSZ anode, with complicated structural features, consists of three different phases such as metallic Ni, YSZ ceramic and pores. Furthermore, the correlation between those structural features makes it difficult to independently optimize individual function of anode such as gas permeability, electrical conductivity and electrochemical activity. Thus, a great deal of efforts to establish structure-property-processing correlation has been made in this study in order to achieve improved anode performance. Critical process steps in anode fabrication were investigated in terms of raw material selection, mixing and granulation, and forming, judging from the performance evaluation of anode substrate. An optimized fabrication process, enabling to produce thin and large-area anode substrate with improved uniformity, will be presented with respect to multifunctional performance of Ni/YSZ anode, and resulting cell performance will be also discussed.© 2003 ASME