You-Kee Lee

Characterization of protective-layer-coated LiMn2O4 cathode thin films

We introduced a post-annealing process for the preparation of spinet-phase LiMn 2 O 4 . The annealed films had proper crystallinity and surface roughness. In order to reduce the interfacereaction during operation, we introduced a diamond-like carbon (DLC) film. The DLC films were deposited on LiMn 2 O 4 films by using electron cyclotron resonance chemical vapor deposition (ECRCVD). A DLC-coated LiMn 2 O 4 film was more stable during the charging -discharging reaction and showed higher discharge capacity over a wide voltage window than the uncoated LiMn 2 O 4 film.

Synthesis and Properties of La 1-x Sr x MnO 3 System as Air Electrode for Solid Oxide Fuel Cell

(LSM,) powders as the air electrode for solid oxide fuel cell were synthesized by a glycine-nitrate combustion process. The powders were then examined by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The as-formed powders were composed of very fine ash particles linked together in chains. X-ray maps of the LSM powders milled for 1.5 h showed that the metallic elements are homogeneously distributed inside each grain and in the different grains. The powder XRD patterns of the LSM with x ) calcined in air at for 4 h. Also, the SEM micrographs showed that the average grain size decreases as Sr content increases. Composite air electrodes made of 50/50 vol% of the resulting LSM powders and yttria stabilized zirconia(YSZ) powders were prepared by colloidal deposition technique. The electrodes were studied by ac impedance spectroscopy in order to improve the performance of a solid oxide fuel cell(SOFC). Reproducible impedance spectra were confirmed using the improved cell, which consisted of LSM-YSZ/YSZ. The composite electrode of LSM and YSZ was found to yield a lower cathodic resistivity than that of the non-composite one. Also, the addition of YSZ to the () electrode led to a pronounced, large decrease in the cathodic resistivity of the LSM-YSZ composite electrodes.

Electroless Copper Deposition on H2 Plasma-Treated TaNx (x=0–1) Diffusion Barriers

Copper was electrolessly deposited on H2 plasma treated TaN diffusion barriers for multilevel interconnect metallization to enhance the quality of electroless Cu with the low electrical resistivity of TaNx barrier films. The electrical resistivity of the H2 plasma treated TaNx barriers increased by 5.2%, compared with the TaNx barriers without plasma treatment. SIMS depth profiles of H2 in TaNx barriers showed that a small fraction (around 15%) of the depth of the TaNx barriers is shown to be plasma-treated. The density of palladium nuclei on the TaNx barriers was remarkably increased by H2 plasma treatment. Thus, improvement of the electroless copper deposition on the TaNx barriers was obtained by H2 plasma treatment without a large increase in the electrical resistivity. The surface energy of the TaNx barriers increased by 29.2% after the plasma treatment. The nucleation sites for palladium nuclei were thought to increase with increasing the surface energy.

금 증착 적외선 반사판의 반사율 및 수명에 미치는 제조공정 변수의 영향

Boron-doped diamond (BDD) electrode has an extremely wide potential window in aqueous and non-aqueous electrolytes, very low and stable background current and high resistance to surface fouling due to weak adsorption. These features endow the BDD electrode with potentially wide electrochemical applications, in such areas as wastewater treatment, electrosynthesis and electrochemical sensors. In this study, the characteristics of the BDD electrode were examined by scanning electron microscopy (SEM) and evaluated by accelerated life test. The effects of manufacturing conditions on the BDD electrode were determined and remedies for negative effects were noted in order to improve the electrode lifetime in wastewater treatment. The lifetime of the BDD electrode was influenced by manufacturing conditions, such as surface roughness, seeding method and rate of introduction of gases into the reaction chamber. The results of this study showed that BDD electrodes manufactured using sanding media of different sizes resulted in the most effective electrode lifetime when the particle size of alumina used was from 75~106 μm (#150). Ultrasonic treatment was found to be more effective than polishing treatment in the test of seeding processes. In addition to this, BDD electrodes manufactured by introducing gases at different rates resulted in the most effective electrode lifetime when the introduced gas had a composition of hydrogen gas 94.5 vol.% carbon source gas 1.6 vol.% and boron source gas 3.9 vol.%.

Convenient Aluminizing Process of Steel by Using Al-Ti Mixed Powder Slurry

)Abstract In this study, we attempted to develop a convenient aluminizing process, using Al-Ti mixed slurryas an aluminum source, to control the Al content of the aluminized layer as a result of a one-step process andcan be widely adopted for coating complex-shaped components. The aluminizing process was carried out by theheat treatment on disc and rod shaped S45C steel substrates with Al-Ti mixed slurries that were composedof various mixed ratios (wt%) of Al and Ti powders. The surface of the resultant aluminized layer was relativelysmooth with no obvious cracks. The aluminized layers mainly contain an Fe-Al compound as the bulk phase.However, the Al concentration and the thickness of the aluminized layer gradually decrease as the Tiproportion among Al-Ti mixed slurries increases. It has also been shown that the Al-Ti compound layer, whichformed on the substrate during heat treatment, easily separates from the substrate. In addition, theincorporation of Ti into the substrate surface during heat treatment was not observed.Key wordsaluminizing process, Al-Ti mixed powder slurry, aluminized layer, Fe-Al compound, Al-Ticompound.

Conditioning effects on La1-xSrxMnO3-Yttria stabilized Zirconia electrodes for thin-film solid oxide fuel cells

Composite cathodes of 50/50 vol percent LSM-YSZ (La1-xSrxMnO3-yttria stabilized zirconia) were deposited onto dense YSZ electrolytes by a colloidal deposition technique. The cathode characteristics were then examined by scanning electron microscopy (SEM) and studied by an impedance spectroscopy (IS). Conditioning effects of the LSM-YSZ cathodes were seen, and remedies for these effects were proposed for improving the performance of a solid oxide fuel cell (SOFC). LSM surface contamination and modification, cathode bonding to the YSZ electrolyte, changing Pt electrode and bonding paste, and curvature of sintered YSZ electrolytes led to some changes in microstructure and variability in cell performances.

Interfacial reactions for the non-stoichiometric TiBx/(100)Si system

AbstractIn order to evaluate the interfacial reactions in the TiBx/(100)Si system and the thermal stability of non-stoichiometric TiBx films (0 ≤ B/Ti ≤ 2.5), TiBx/Si samples prepared by a co-evaporation process were annealed in vacuum at temperatures between 300 and 1000°C. The solid phase reactions were investigated by means of sheet resistance, X-ray diffraction, transmission electron microscopy, X-ray photo-electron spectroscopy, and stress measurement. For TiBx samples with a ratio of B/Ti ≥ 2.0, an apparent structural change is not observed even after annealing at 1000°C for 1 h. For samples with a ratio of B/Ti < 2.0, however, there are two competitive solid phase reactions: the formation of a titanium silicide layer at the interface and the formation of a stoichiometric TiB2 layer at the surface, indicating the salicide

Conditioning effects on La1−xSrxMnO3-yttria stabilized zirconia electrodes for thin-film solid oxide fuel cells

(\underline s elf - \underline {al} igned sil\underline {icide} )