• Journal of the Korean Ceramic Society
• /
• v.53 no.5
• /
• pp.494-499
• /
• 2016

In this work, the effects of different sintering inhibitors added to $La_{0.8}Sr_{0.2}MnO_{3-{\partial}}$ (LSM) were studied to obtain an optimum cathode material for cathode-supported type of Solid oxide fuel cell (SOFC) in terms of phase stability, mechanical strength, electric conductivity and porosity. Four different sintering inhibitors of $Al_2O_3$, $CeO_2$, NiO and gadolinium doped ceria (GDC) were mixed with LSM powder, sintered at $1300^{\circ}C$ and then they were evaluated. The phase stability, sintering behavior, electrical conductivity, mechanical strength and microstructure were evaluated in order to assess the performance of the mixture powder as cathode support material. It has been found that the addition of $Al_2O_3$ undesirably decreased the electrical conductivity of LSM; other sintering inhibitors, however, showed sufficient levels of electrical conductivity. GDC and NiO addition showed a promising increase in mechanical strength of the LSM material, which is one of the basic requirements in cathode-supported designs of fuel cells. However, NiO showed a high reactivity with LSM during high temperature ($1300^{\circ}C$) sintering. So, this study concluded that GDC is a potential candidate for use as a sintering inhibitor for high temperature sintering of cathode materials.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.24 no.3
• /
• pp.127-132
• /
• 2014

$Y_2O_3$-BN ceramic composites were fabricated from the slurries of yttria powder with average particle size of 3~10 ${\mu}m$. The slurry was fabricated by mixing PVA binder, NaOH for Ph control, PEG, BN powder and $Y_2O_3$ powder. The mixed $Y_2O_3$ powders were obtained by spray drying process from the slurry. The $Y_2O_3$-BN composite specimen was shaped in size of ${\O}14mm$ and then sintered at $1550^{\circ}C$ and $1600^{\circ}C$, respectively. The characteristics, microstructure, purities, densities, bulk resistance, thermal expansion, hardness and plasma resistance of the $Y_2O_3$-BN composites were investigated with the function of BN contents and sintering temperature.

• Korean Journal of Materials Research
• /
• v.26 no.8
• /
• pp.401-405
• /
• 2016

The cobalt silicides were investigated for employment as a catalytic layer for a DSSC. Using an E-gun evaporation process, we prepared a sample of 100 nm-thick cobalt on a p-type Si (100) wafer. To form cobalt silicides, the samples were annealed at temperatures of $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$ for 30 minutes in a vacuum. Four-point probe, XRD, FE-SEM, and CV analyses were used to determine the sheet resistance, phase, microstructure, and catalytic activity of the cobalt silicides. To confirm the corrosion stability, we also checked the microstructure change of the cobalt silicides after dipping into iodide electrolyte. Through the sheet resistance and XRD results, we determined that $Co_2Si$, CoSi, and $CoSi_2$ were formed successfully by annealing at $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$, respectively. The microstructure analysis results showed that all the cobalt silicides were formed uniformly, and CoSi and $CoSi_2$ layers were very stable even after dipping in the iodide electrolyte. The CV result showed that CoSi and $CoSi_2$ exhibit catalytic activities 67 % and 54 % that of Pt. Our results for $Co_2Si$, CoSi, and $CoSi_2$ revealed that CoSi and $CoSi_2$ could be employed as catalyst for a DSSC.

• Proceedings of the KWS Conference
• /
• 2002.10a
• /
• pp.187-192
• /
• 2002

Applicability of laser micro welding process to the fabrication of medical devices was investigated. Austenitic stainless steel wire (SUS304) was spot melted and crosswise welded, which is one of the most possible welding process for the fabrication of medical devices, by using a Nd-YAG laser. Effects of welding parameters on the microstructure, tensile strength and corrosion resistance were discussed. In the spot melting, melted metal width decreased with decreasing the input energy and pulse duration. Controlling the laser wave to reduce laser noise which occurred in the early stage of laser irradiation made reasonable welding condition wider in the welding condition of small pulse duration such as 2ms. The microstructure of the melted metal was a cellular dendrite structure and the cell size of the weld metal was about 0.5~3.5 ${\mu}{\textrm}{m}$. Tensile strength increased with the decrease of the melted metal width and reached to a maximum about 660MPa, which is comparable with that for the tempered base metal. Even by immersion test at 318K for 3600ks in quasi biological environment (0.9% NaCl), microstructure of the melted metal and tensile strength hardly changed from those for as melted material. In the crosswise welding, joints morphologies were classified into 3 types by the melting state of lower wire. Fracture load increased with input energy and melted area of lower wire, and reached to a maximum about 80N. However, when input energy was further increased and lower wire was fully melted, fracture load decreased due to the burn out of weld metal.

• Journal of the Korean Ceramic Society
• /
• v.44 no.12
• /
• pp.690-695
• /
• 2007

Scandia stabilized zirconia (ScSZ) is adapted for electrolyte material of solid oxide fuel cell (SOFC) because of its high ionic conductivity and chemical stability. ScMnSZ1 powder having a composition of $((ZrO_2)_{0.89}(Sc_2O_3)_{0.1}(MnO_2)_{0.01})$ is synthesized by ultrasonic spray pyrolysis (USP) method. Porous ScMnSZ1 powder is obtained by using a pore forming agent. Microstructure and morphology, particle size distribution of porous powder synthesized with 3wt% pore forming agent are investigated. Sintered ScMnSZ1 sample with ground fine powder are also investigated their microstructure and electrical conductivity. The electrical conductivity of sintered ScMnSZ1 samples with ground fine powder was 0.082 S/cm, 0.127 S/cm and 0.249 S/cm at $750^{\circ}C$, $800^{\circ}C$ and $900^{\circ}C$, respectively.

• Korean Journal of Food Science and Technology
• /
• v.21 no.2
• /
• pp.294-299
• /
• 1989

The quality of dehydrated instant rice produced by a few selected processing methods with short grain milled rice was evaluated. Instant rice produced by process 2 had high rehydration rate, and those by processes 1 and 2 revealed light brown color with less lightness. Instant rice produced by processes 1 and 2 with ammonium carbonate treatment had more uniform porous microstructure, as shown by SEM micrographes, and microstructural difference was noticed between instant rice prepared with government rice and Akibari. Instant rice produced by processes 1 and 2 had less sensory color score, and those by processes 2 and 4 had higher sensory cohesiveness. Overall quality of instant rice produced by process 2 was better, except color.

• Korean Journal of Food Science and Technology
• /
• v.30 no.3
• /
• pp.569-573
• /
• 1998

This study was conducted to investigate the differences of textural characteristics and microstructure of sugared chestnuts between heated by a heater and microwave. Raw chestnuts were boiled and infiltrated the sugar in sugar syrup by heating. The content of WSP (water soluble pectin) was increased, but HSP (hydrochloric acid soluble pectin) was decreased by boiling and sugaring. This change was remarkable when it was boiled and sugared by a microwave heating. The hardness, gumminess and chewiness were more decreased in the sugared chestnut boiled and sugared with a microwave than that processed with a heater. Microstructure of sugared chestnut processed with a microwave heating showed the distruction of cell wall.

• Journal of the Semiconductor & Display Technology
• /
• v.12 no.3
• /
• pp.41-46
• /
• 2013

Efficient and inexpensive solar cells are necessary for photo-voltaic to be widely adopted for mainstream electricity generation. For this to occur, the recombination losses of charge carriers (i.e. electrons or holes) must be minimized using a surface passivation technique suitable for manufacturing. Recently it has been shown that aluminum oxide thin films are negatively charged dielectrics that provide excellent surface passivation of silicon solar cells to attract positive-charged holes. Especially aluminum oxide thin film is a quite suitable passivation on the rear side of p-type silicon solar cells. This paper, it demonstrate the interfacial microstructure and electrical properties of mono-crystalline silicon surface passivated by $Al_2O_3$ films during firing process as applied for screen-printed solar cells. The first task is a comparison of the interfacial microstructure and chemical bonds of PECVD $Al_2O_3$ and of PEALD $Al_2O_3$ films for the surface passivation of silicon. The second is to study electrical properties of double-stacked layers of PEALD $Al_2O_3$/PECVD SiN films after firing process in the temperature range of $650{\sim}950^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.2
• /
• pp.26-32
• /
• 2021

The photovoltaic properties and microstructure changes were observed while perovskite solar cells (PSCs) with a fabricated carbon electrode were formed using the following annealing processes: hot-plate, oven, and rapid thermal annealing (RTA). Perovskite solar cells with a glass/FTO/compact TiO2/meso TiO2/meso ZrO2/carbon structure were prepared. The photovoltaic properties and microstructure changes in the PSCs were analyzed using a solar simulator, optical microscopy, and field emission scanning electron microscopy. An analysis of the photovoltaic properties revealed outstanding properties when RTA was applied to the cells. Microstructure analysis showed that perovskite was formed locally on the carbon electrode surface when hot-plate and oven annealing were applied. On the other hand, PSC with RTA showed a flat surface without extra perovskite agglomeration. Denser perovskite formed on the porous carbon electrode layer with RTA showed superior photovoltaic properties. These results suggest that the RTA process might be appropriate for the massive production of carbon electrode PSCs considering the processing time.

• Journal of Powder Materials
• /
• v.15 no.5
• /
• pp.405-410
• /
• 2008

SOFC (Solid Oxide Fuel Cell) Ni-YSZ anode was fabricated by the spark plasma sintering (SPS) process and its microstructure and electrical properties were investigated in this study. The spark plasma sintering process was carried out at $800{\sim}1000^{\circ}C$ for holding time of 5 min under 40 MPa. To fabricate Ni-YSZ anode, the SPS processed specimens were reduced at $800^{\circ}C$ under $H_2$ atmosphere. The reduced specimens showed relative density of $48.4{\sim}64.8%$ according to sintering temperature. And also, the electrical conductivity of reduced specimens after sintering at 900 and $1000^{\circ}C$ showed $480{\sim}600$ (S/cm) values at the measuring range of $600{\sim}900^{\circ}C$.