• Nuclear Engineering and Technology
• /
• 제42권5호
• /
• pp.576-581
• /
• 2010

KAERI (Korea Atomic Energy Research Institute) fabricated MOX (Mixed Oxide) fuel pellets as a cooperation project with PSI (Paul Scherrer Institut) for an irradiation test in the Halden reactor. The MOX pellets were fitted into fuel rods that included instrumentation for measurement in IFE (Institutt for Energiteknikk). The fuel rods were assembled into the test rig and irradiated in the Halden reactor up to 50 MWd/kgHM. The irradiated fuel rods were transported to the IFE, where ceramography was carried out. The fuel rods were cut transversely at the relatively higher burn-up locations and then the radial cross sections were observed. Micrographs were analyzed using an image analysis program and grain sizes along the radial direction were measured by the linear intercept method. Radial cracks in the irradiated MOX were observed that were generally circumferentially closed at the pellet periphery and open in the hot central region. A circumferential crack was formed along the boundary between the dark central and the outer regions. The inner surface of the cladding was covered with an oxide layer. Pu-rich spots were observed in the outer region of the fuel pellets. The spots were surrounded by many small pores and contained some big pores inside. Metallic fission product precipitates were observed mainly in the central region and in the inside of the Pu spots. The average areal fractions of the metallic precipitates at the radial cross section were 0.41% for rod 6 and 0.32% for rod 3. In the periphery, pore density smaller than 2 ${\mu}m$ was higher than that of the other regions. The grain growth occurred from 10 ${\mu}m$ to 12 ${\mu}m$ in the central region of rod 6 during irradiation.

• 대한금속재료학회지
• /
• 제49권1호
• /
• pp.25-31
• /
• 2011

Solid oxide fuel cells (SOFCs) have many attractive features for widespread applications in generation systems. Recently, stainless steels have attractive materials for metallic bipolar plate because metallic bipolar plates have many benefits compared to others such as graphite and composite bipolar plates. SOFC operates on high temperature of about $800{\sim}1000^{\circ}C$ than other fuel cell systems. Thus, many studies have attempted to reduced the operation temperature of SOFC to about $600{\sim}800^{\circ}C$, which is the intermediate temperature (IT) of SOFC. Low cost and high-temperature corrosion resistance are very important for the practical applications of SOFC in various industries. In this study, two specimens, 304 and 430 stainless steels with and without different pre-surface treatments on the surface were investigated. And, specimens were exposed at high temperature in the box furnace under oxidation atmosphere of $800^{\circ}C$. Oxidation behavior have been investigated with the materials exposed at different times (100 hrs and 400 hrs) by SEM, EDS and XRD. By increasing exposure time, the amount of metal oxide increased in the order like; STS304 < STS430 and As-received < As-polished < Sand-blast specimens.

• 한국세라믹학회지
• /
• 제19권2호
• /
• pp.145-151
• /
• 1982

Many materials such as silica gel, metallic oxide, activated alumina and alkaline earth metal carbonates were employed as filter media for gaseous oxides of ruthenium volatilized during high level radioactive waste processing. The adsorption efficiency of ruthenium on these materials was evaluated. For the purpose of observing behavior of ruthenium oxides, thermogravimetric analysis of ruthenium oxide in a stream of oxygen was carried out. The rate of volatilization was proportional to the square root of oxygen partial pressure, and increased exponentially with temperature. At $650^{\circ}C$, gaseous ruthenium oxides showed a strongly marked effect of deposition. Of all the materials available, calcium oxide proved to be the best that could be used to adsorb ruthenium.

• 한국표면공학회지
• /
• 제35권5호
• /
• pp.273-278
• /
• 2002

We oxidized pure titanium by anodizing oxidation process in the range of 590V, within 1.5A, 30seconds. we investigated color evolution with a spectrophotometer. Surface images and surface roughness were characterized by an optical microscope and an atomic force microscope, respectively. Below the thickness of 40 $\mu\textrm{m}$, metallic yellow, blue, and pink colorsn were obtained. Lightness decreased, increased, and decreased again as titanium oxide thickness increased. Blue color at the applied voltage of 30V showed the best lightness and reproducibility with surface roughness below l$\mu\textrm{m}$. Bare titanium and titanium oxide films had micro pits more than 10ea/$\mu\textrm{m}^2$. We report that we successfully made colors by varing thickness below 40$\mu\textrm{m}$ with anodizing oxidation of method.

• 한국표면공학회지
• /
• 제31권2호
• /
• pp.101-108
• /
• 1998

The effect of oxidation-reduction heating conditions on coating adherence of hot-dip galvanized steel containing silicon has beeninvestigated. The presence of a stbke sillicon oxide formed on the steel surface has been shown to be very detrimenal to proper wetting by liquid zinc. When the steel has more than the critical sillicon content neeled to from a stable external oxide, the use of oxidation-reduction method has been found successful in obtaining a good quality, coated product with excellence adhreence. This can be explained by the formation of an iron oxide. The iron oxrtion of the scale is reduced, leaving the stable oxides dispersed in a fresh metallic iron surface layer. This reduced iron surface is easily wetted by the liquid zinc and excellent adherence is obtained.

• 통합자연과학논문집
• /
• 제11권1호
• /
• pp.14-18
• /
• 2018

Nickel oxide nanofibers were synthesized by electrospinning with nickel(II) acetate tetrahydrate and polyvinylpyrrolidone and calcination process. The nanofiber shape was easily detected from the nanofibers with high Ni contents after calcined at $600^{\circ}C$ and the crystal structure of layer-by-layer growth was observed from SEM images at $900^{\circ}C$. XRD and TEM results showed metallic Ni and NiO structure were formed at nanofibers obtained at 600 and $900^{\circ}C$ and the crystallite size was calculated from 25 to 55 nm. The surface of nanofibers was fully oxidized from the deconvoluted Cu 2p and O 1s XPS spectra.

• 정보저장시스템학회논문집
• /
• 제9권2호
• /
• pp.67-71
• /
• 2013

The fabrication method of plasmonic nanodots on silicon substrate has been developed to improve the efficiency of thin film solar cells. Nanoscale metallic nanodots arrays are fabricated by anodic aluminum oxide (AAO) template mask which can have different structural parameters by varying anodization conditions. In this paper, the structural parameters of gold nanodots, which can be controlled by the diverse structures of AAO template mask, are investigated to enhance the optical properties of a-Si thin film solar cells. It is found that optical properties of the thin film solar cells are improved by finding optimization values of the structural parameters of the gold nanodot array.

• 한국재료학회지
• /
• 제9권5호
• /
• pp.491-495
• /
• 1999

In this study, we focus on Ca contaminant which affects on the roughness Si substrate after thermal process. The initial Si substrates were contaminated intentionally by using a standard Ca solution. The contamination levels of Ca impurity were measured by TXRF and the chemical composition of that was analyzed by AES. Then we gre the thermal oxide to investigate the effect of Ca contaminants. The microroughness of the Si surface, the thermal oxide surface, and the surface after removing the thermal oxide were measured to examine the electrical characteristics. The initial substrates that were contaminated with the standard solution of Ca exhibited the contamination levels of 10\ulcorner~10\ulcorneratoms/$\textrm{cm}^2$ which was measured by TXRF. The Ca contaminants were detected by AES and exhibited the peaks of Ca, SI, C and O.After intentional contamination, the surface microroughness of this initial substrate was increased from $1.5\AA$ to 4$\AA$ as contamination levels became higher. The microroughness of the thermal oxide surfaces of both contaminated and bare Si substrates exhibits similar values. But the microroughness of the contaminated$ Si/SiO_2$ interface was increased as contamination increased. The thermal oxide of contaminated substrate exhibited the small minority carrier diffusion length, low breakdown voltage, and slightly high leakage current.

• 한국재료학회지
• /
• 제16권3호
• /
• pp.178-182
• /
• 2006

A single electro-discharge-sintering (EDS) pulse (1.0 kJ/0.7 g), from a $300{\mu}F$ capacitor, was applied to atomized spherical Ti-6Al-4V powder in a low vacuum to produce porous-surfaced implant compacts. A solid core surrounded by a porous layer was formed by a discharge in the middle of the compact. XPS (X-ray photoelectron spectroscopy) was used to study the surface characteristics of the implant material. C, O, and Ti were the main constituents, with smaller amounts of Al, V, and N. The implant surface was lightly oxidized and was primarily in the form of $TiO_2$ with a small amount of metallic Ti. A lightly etched EDS implant sample showed the surface form of metallic Ti, indicating that EDS breaks down the oxide film of the as-received Ti-6Al-4V powder during the discharge process. The EDS Ti-6Al-4V implant surface also contained small amounts of aluminum oxide in addition to $TiO_2$. However, V detected in the EDS Ti-6Al-4V implant surface, did not contribute to the formation of the oxide film..

• 한국세라믹학회지
• /
• 제51권4호
• /
• pp.295-299
• /
• 2014

Electrical conductivities of complex perovskites, layered perovskite and Sr doped layered perovskite oxides were measured and analyzed for cathode materials of Intermediate Temperature-operating Solid Oxide Fuel Cells (IT-SOFCs). The electrical conductivities of $Sm_{1-x}Sr_xCoO_{3-\delta}$ (x = 0.3 and 0.7) exhibit a metal-insulator transition (MIT) behavior as a function of temperature. However, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ (SSC55) shows metallic conductivity characteristics and the maximum electrical conductivity value compared to the values of $Pr_{0.5}Sr_{0.5}CoO_{3-\delta}$ (PSC55) and $Nd_{0.5}Sr_{0.5}CoO_{3-\delta}$ (NSC55). The electrical conductivity of $SmBaCo_2O_{5+\delta}$ (SBCO) exhibits a MIT at about $250^{\circ}C$. The maximum conductivity is 570 S/cm at $200^{\circ}C$ and its value is higher than 170 S/cm over the whole temperature range tested. $SmBa_{0.5}Sr_{0.5}Co_2O_{5+\delta}$ (SBSCO), 0.5 mol% Sr and Ba substituted at the layered perovskite shows a typically metallic conductivity that is very similar to the behavior of the SSC55 cathode, and the maximum and minimum electrical conductivity in the SBSCO are 1280 S/cm at $50^{\circ}C$ and 280 S/cm at $900^{\circ}C$.