• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2999-3003
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• 2012

Various types of room temperature ionic liquids (RTILs) containing 1,1-dicyano-1-acetylmethanide anion ($[C(CN)_2(COCH_3)]^-$, $[DCNAcC]^-$) were prepared and their physical and electrochemical properties were studied. All of these ILs exhibited high thermal stabilities over $200^{\circ}C$ and relatively high ionic conductivities up to 29.4 $mS\;cm^{-1}$ at $80^{\circ}C$. Although the ionic conductivity of IL containing bis(trifluoromethanesulfonyl)-imide ($[Tf_2N]^-$) anion is higher than that of ILs bearing $[DCNAcC]^-$ anion, the specific capacitance of ILs bearing $[DCNAcC]^-$ anion are higher than that of IL containing $[Tf_2N]^-$ anion and showed high temperature dependence. Such favorable electrochemical properties of these ILs are likely to be attributed to the efficient dissociation of cation and anion at higher temperature and enhanced electrosorption of $[DCNAcC]^-$ anion at the electrode.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.1
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• pp.17-24
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• 2020

As an interconnect scaling faces a technical bottleneck, the device stacking technologies have been developed for miniaturization, low cost and high performance. To manufacture a stacked device structure, a vertical interconnect becomes a key process to enable signal and power integrities. Most bonding materials used in stacked structures are currently solder or Cu pillar with Sn cap, but copper is emerging as the most important bonding material due to fine-pitch patternability and high electrical performance. Copper bonding has advantages such as CMOS compatible process, high electrical and thermal conductivities, and excellent mechanical integrity, but it has major disadvantages of high bonding temperature, quick oxidation, and planarization requirement. There are many copper bonding processes such as dielectric bonding, copper direct bonding, copper-oxide hybrid bonding, copper-polymer hybrid bonding, etc.. As copper bonding evolves, copper-oxide hybrid bonding is considered as the most promising bonding process for vertically stacked device structure. This paper reviews current research trends of copper bonding focusing on the key process of Cu-SiO₂ hybrid bonding.

• Current Photovoltaic Research
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• v.6 no.2
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• pp.39-42
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• 2018

When the PV module is illuminated in a high temperature region, solar cells are also exposed to the high temperature external environment. The operating temperature of the solar cell inside the module is increased, which causes the power drops. Various efforts have been made to reduce the operating temperature and compensate the power of solar cells according to the outdoor temperature such as installing of a cooling system. Researches have been also reported to lower the operating temperature of solar cells by improving the heat dissipation properties of the backsheet. In this study, we conducted a test to measure the internal temperature of each module components and the external temperature when the light was irradiated according to the surrounding temperature. Backsheets with different thermal conductivities were compared in the test. Finally, in order to explain the temperature difference between the solar cell and the outside of the module, we proposed an evaluation method of the heat transfer characteristics of photovoltaic modules with different backsheet.

• Korean Journal of Materials Research
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• v.25 no.9
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• pp.450-454
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• 2015

A simulation method to estimate microstructure dependent material properties and their influence on performance for a honeycomb structured SiC heating element has been established. Electrical and thermal conductivities of a porous SiC sample were calculated by solving a current continuity equation. Then, the results were used as input parameters for a finite element analysis package to predict temperature distribution when the heating element was subjected to a DC bias. Based on the simulation results, a direction of material development for better heating efficiency was found. In addition, a modified metal electrode scheme to decelerate corrosion kinetics was proposed, by which the durability of the water heating system was greatly improved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.350-350
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• 2010

Silicon carbide (SiC), one of the well known wide band gap semiconductors, shows high thermal conductivities, chemical inertness and breakdown energies. The design of normally-off 4H-SiC VJFETs [1] has been reported and 4H-SiC VJFETs with different lateral JFET channel opening dimensions have been studied [2]. In this work, 4H-SiC based VJFETs has been designed using the device simulator (ATLAS, Silvaco Data System, Inc). We varied the n-epi layer thickness (from $6\;{\mu}m$ to $10\;{\mu}m$) and the channel width (from $0.9\;{\mu}m$ to $1.2\;{\mu}m$), and investigated the static characteristics as blocking voltages, threshold voltages, on-resistances. We have shown that silicon carbide JFET structures of highly intensified blocking voltages with optimized figures of merit can thus be achieved by adjusting the epi layer thickness and channel width.

• Journal of Korea Foundry Society
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• v.33 no.1
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• pp.8-12
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• 2013

Although aluminum-silicon based commercial casting alloys have been used in applications that demand high electrical or thermal conductivity, new aluminum casting alloys that possess higher conductivities are currently required for advanced applications. Therefore, there is much research into the development of new high conductivity aluminum casting alloys that contain lower amounts of or no silicon. In this research, the properties and casting characteristics of Al-Zn-Fe-Si alloys with various Fe and Si contents were investigated. Two types of AlFeSi phases were formed depending on the Fe and Si contents. As the silicon content increased, the tensile strength of the Al-Zn-Fe-Si alloy increased slightly, while the electrical conductivity decreased slightly. It was also observed that both the fluidity and hot cracking susceptibility of the investigated alloys were closely related to the formation of the AlFeSi phases.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.633-638
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• 2009

Lightweight materials were fabricated using glass abrasive sludge, bottom ash and slag powder in this study. This study tried to draw the correlation between physical properties and internal pore of lightweight material. The content of bottom ash and slag powder was from 10% to 50% and firing temperature from $760{^{\circ}C}\;to\;800{^{\circ}C}$ in rotary kiln. The lightweight material containing bottom ash or slag powder had a specific gravity of $0.21{\sim}0.70$ at particle size $2{\sim}4$ mm. Replacement ratio of the admixture increasing with specific gravity increased. Fracture strength of panel made with various lightweight materials was $32{\sim}55\;kgf/cm^2$ and flexural strength was $11{\sim}18\;kgf/cm^2$. Fracture strength increased by 72% and flexural strength was 63% compared with reference. Thermal conductivities of panel was $0.07{\sim}0.11W/m{\cdot}k$. The water absorption ratios of panel with lightweight materials containing bottom ash were $1.8{\sim}2.8$% and slag powder were $2.65{\sim}2.8$%. Excellent results on resistant of water absorption.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.12
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• pp.1209-1216
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• 2010

This paper dealt with an alternative for maximizing mass savings in spacecraft design by replacing conventional aluminum alloy housing used for various spacecraft avionics by composite materials. Key requirements were defined for the purpose of composite housing design with sufficient durability and various functionalities as well as more lightweight characteristics as compared with aluminum alloy widely-used for conventional electronics housing. Conceptual design was also carried out for manufacturing modular, lightweight composite electronic housing equipped with high thermal and electrical conductivities, EMI protection, and radiation shielding characteristics as well as excellent structural performance; feasibility of enhancing mass savings in spacecraft design was presented.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.4
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• pp.430-439
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• 1985

Conjugate natural convection in double enclosed annuli between horizontal concentric cylinders has been studied by the numerical analysis and experimental measurements. The interface conditions between the liquid and the solid of middle shell are obtained through the correlation factor based on the ratio of solid to fluid thermal conductivities and the Prandtl number. The characteristics of conjugate heat transfer are discussed under various dimensionless parameters such as conductivity ratios, shell thickness, diameter ratios, Prandtl number, and Rayleigh number. It is found that the average equivalent conductivity K over var $_{eq}$ does not depend on the conductivity ratios and shell thickness. The K over bar $_{eq}$ however, depends on the Prandtl number and the Rayleigh number.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.211-215
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• 2005

The binary Al-Mg alloys are the basis for the 5000 series of non-heat-treatable aluminum alloys. In general, 5000 series of aluminum alleys have a high strength, good welding characteristics and a high resistance to corrosion, especially under the seawater. Thus the aluminum alloys are adopted in the hull material of hovercraft that is required light in weight as well as high strength. It is very important that the weldability problem of these alloys caused by high thermal conductivities welding deformation, porosity and so on. in this study, auto-welding equipment was applied for aluminum welding automation. Also, optimal welding data were studied by investigating welding characteristics for various shapes of weldment to use Al 5083 that is representative structural materials of the 5000 series of aluminum alloys.