• Bulletin of the Korean Chemical Society
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• v.25 no.6
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• pp.843-846
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• 2004

Pt nanoparticles loaded on alumina through an impregnation at room temperature was prepared using $K_2PtCl_4$ and acrylic acid as capping material. Transmission electron microscopy showed that the deposited Pt particles indicate ca. 80% cubic shapes with a narrow distribution of 8-10 nm in size. Propylene hydrogenation over the catalyst has been carried out to evaluate their catalytic performance by the values of activation energy. It is determined from the initial rate, reaction order, and rate constant and is found to be $9.7{\pm}0.5$ kcal/mol. This value has been discussed by comparing to those of encapsulated- and truncated octahedral Pt nanoparticles deposited on alumina, respectively, to study influence of the particle size and shape, and capping material used on the activation energy.

• Korean Journal of Materials Research
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• v.27 no.1
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• pp.39-42
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• 2017

E-glass (electrical glass) fiber is the widely used as a reinforced composite material of PCBs (printed circuit boards). However, E-glass fiber is not stable because it has a dielectric constant of 6~7. On the other hand, D-glass (dielectric glass) fiber has a low dielectric constant of 3~4.5. Thus, it is adaptable for use as a reinforcing material of PCBs. In this study, we fabricated D-glass compositions with low dielectric constant, and measured the electrical and optical properties. In the glass composition, the boron content was changed from 9 to 31 wt%. To confirm the dependence of the dielectric constant on melting properties, D-glass with 22 wt% boron was melted at $1550^{\circ}C$ and $1650^{\circ}C$ for 2hrs. The glass melted at $1650^{\circ}C$ had a lower dielectric constant than the glass melted at $1550^{\circ}C$. Therefore, the D-glass with boron of 9~31 wt% was fabricated by melting at $1650^{\circ}C$ for 2hrs, and transparent clear glass was obtained. We identified the non-crystalline nature of the glass using an XRD (x-ray diffractometer) graph. The visible light transmittance values depending on the boron contents were measured and found to be 88.6 % ~ 82.5 %. Finally, the dielectric constant of the D-glass with 31 wt% boron was found to have decreased from 4.18 to 3.93.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.3
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• pp.241-246
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• 2012

A layered planer SOFC module was designed from planar-type SOFC. It was prepared by multi-layered ceramic technology. To form the cathode and the anode in the layered structure, reliable channels should be made on the both side of electrolyte perpendicularly. However, monolithic SOFC using multi-layered ceramic technology hasn't been studied another group, and the warpage of electrolyte in the channel, also, hasn't been studied, when electrode is printed on the electrolyte. In this study, the channels are prepared with electrode printing, and their warpage are evaluated. In the case of YSZ without electrode, the warpages are nothing in the limit of measurement using optical microscope. The warpage of 'YSZ-NiO printed' increases than that of 'NiO printed', and also, the case of 'double electrode printed' is similar to 'YSZ-NiO printed'. It is thought that, in the printed electrolyte, the warpage is related to the difference of the sintering behavior of each material.

• Journal of the Korean Ceramic Society
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• v.43 no.5 s.288
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• pp.277-283
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• 2006

A porous material with a surface layer was fabricated from glass abrasive sludge and expanding agents. The glass abrasive sludges were mixed with expanding agents and compacted into precursors. These precursors were sintered in the range of $700-900^{\circ}C$ for 20 min. The sintered porous materials had a surface layer with smaller pores and inner parts with larger pores. The surface layer and closed pores controlled water absorption. As the expanding agent fraction and the sintering temperature increased, the porosity and pore size increased. The porous materials with $Fe_2O_3$ and graphite as the expanding agents had a low absorption ratio of about 3% or lower while the porous material with $CaCO_3$ as the expanding agent had a higher absorption ratio and more open pores.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.304-304
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• 2007

고주파 모률에서 사용되는 기판소재는 저유전율과 낮은 loss 특성을 요구함으로 지속적인 연구를 필요로 한다. 지금까지의 ceramic/glass composite 에서 주로 사용된 ceramic filler는 Al2O3로 낮은 유전률을 구현에 한계가 있었다. Cordierite는 낮은 유전율 (${\varepsilon}_r$ < 4)을 나타내는 filler로서 그 가능성이 높지만 아직까지 보고된 결과들이 미흡한 실정이다. 따라서 본 연구에서는 cordierite filler와 SiO2-B2O3-Al2O3-RO (R : Zn, Sr, Ba, Ca)계의 glass를 혼합하여 LTCC용 기판소재로서의 가능성을 확인하고자 저온 동시소성이 가능한 소결온도인 $850^{\circ}C{\sim}1.000^{\circ}C$ 사이에서 소재의 소결실험을 진행하였다. 소결온도에 따른 상변화, 유전특성을 확인한 결과 filler로 사용된 cordierite상만이 관찰 되었으며 소결조건에 따라 5.0~5.5의 낮은 유전율과 1.000~1,500의 Q를 나타내는 것을 확인 하였다.

• Membrane Journal
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• v.32 no.5
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• pp.265-274
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• 2022

Separation of oily wastewater, which is a byproduct of various industries such as petroleum refineries, is essential to not exceed the tolerance limit of wastewater streams. Ceramic membranes show potential in oily wastewater separation, due to their excellent oil removal efficiency, good chemical, thermal, and mechanical stability, and simple operation. However, widespread application of ceramic membranes is limited due to high material cost of alumina, silica, and other ceramic based materials used to fabricate them. Recent efforts to reduce material cost have been made, using fly ash and clay. This review examines the fabrication and efficiency of ceramic membranes in oily wastewater separation according to material: silica, alumina, and waste ash.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.23 no.1
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• pp.16-26
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• 2014

Materials that can be use in CAD/CAM are composite, ceramic, hybrid and metal. Among the available materials, monolithic ceramic technique which is the manufacturing technique using one type of the materials is mainly used in a dental office. It is the technique where final tooth-shaped prostheses are made from the material block and used after polishing or applying heat and that does not require traditional ceramic build-up process. Although shot of esthetic quality, because manufactured within 1 hour the monolithic ceramic technique has advantages such as that treatment can be completed in one day and in one time visit, that stability of the material is high because there are low possibility of distort by not melting and phase transformation, and that it can be easily worked in the office with computer assisted devices. We classified the materials that can be used in this technique based on their generations from clinical stand point.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.300-300
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• 2010

Ceramic capacitor의 에너지내량을 향상시켜 제품의 신뢰성을 높이고자 RF Sputtering을 이용하여 외부전극을 형성하였다. 본 연구에서는 Target의 종류, 증착 시간 및 열처리 유/무에 따른 Ceramic capacitor의 전기적 특성 및 미세구조를 분석하여 최적조건을 확립하였으며, 최적 증착 조건으로 제작한 Ceramic capacitor의 에너지내량을 측정하였다. Target은 Ni target과 Cu target을 사용하였으며, Sputtering 시간은 10, 30, 60분으로 하였다. Sputtering 시간에 따른 Ceramic capacitor의 용량 특성과 손실은 큰 차이가 없었지만, Wire 연결시 Sputtering 시간에 따라 납땜성의 차이가 나타났으며, 증착 시간과 열처리 유/무에 따른 에너지내량의 변화를 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.249-249
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• 2010

We investigated novel surface treatment and its impact on silicon photovoltaic cells. Using 2-step etching methods, we have changed the nanostructure on pyramid surface so that less light is reflected. This work proposes an improved texturing technique of mono crystalline silicon surface for solar cells with sub-nanotexturing process. The nanotextured silicon surface exhibits a lower average reflectivity (~4%) in the wavelength range of 300-1100nm without antireflection coating layer. It is worth mentioning that the surface of pyramids may also affect the surface reflectance and carrier lifetime. In one word, we believe nanotextruing is a promising guide for texturization of monocrystalline silicon surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.73-78
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• 1994

Wear and fracture mode of ceramic tool for hardened SKD11 steel was investigated by face milling in this study. The cutting force and Acoustic Emission(AE) signal were utilized to detect the wear and fracture of ceramic tool. The following conclusions were obtained : (1) The wear and fracture modes of ceramic tool are characterized by three types: \circled1wear which has normal wear and notch wear, \circled2 wear caused by scooping on the rake face, \circled3 large fracture caused by thermal crack in the rake face. (2) The wear behaviour of ceramic tool can be detected by the increase of mean cutting force and the variation of the AE RMS voltage. (3) The catastrophic fracture of ceramic tool can be detected by the cutting force(Fz-component). (4) As the hardness of work material increased, Acoustic Emission RMS value and mean cutting force(Fz) increased linearly, but the tool life decreased.