• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.50-53
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• 2008

In this work, the $TiO_2$ pigment influence in HDPE dielectric strength was analyzed. Chemical and structural characterizations were made to identify changes during the processing and your influence in the electrical properties. Formulations containing 0, 0.5, 1, 2.5, 4 and 6 of titanium dioxide were processed by extrusion and injection molding with stabilization-antioxidants, ultraviolet stabilizers and plasticizers. The electrical strength tests were analyzed by the statistical distribution of Weibull, and the maximum likelihood method. The high concentrations present lower values to electrical strength. The $\beta$ parameter could be using to insulator particles dispersion. The $TiO_2$ concentration variation shows that these incorporations implicate strength values increase has a maximum (5,35MV/cm). High pigment concentration induces a little falls in property values. Observing the $\beta$ parameter, minimum experiment electric field (Ebmin) and electric strength value, found that the best electric perform formulation was the formulation with 2.5% $TiO_2$ weight.

• Journal of Korea Foundry Society
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• v.21 no.2
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• pp.119-126
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• 2001

Al/15%Gr. composite have been manufactured by mixing, compacting, and extruding aluminium powder and graphite powder. Then, Al-6%Si/x%Gr., Al-12%Si/x%Gr., and Al-18%Si/x%Gr.(x: 0, 2, 4, 6, 8) composites have been manufactured by remelting the extruded materials(Al/15%Gr.), Al-33.3%Si alloy, and Al ingot, etc. We conducted experiments to chracterize the microstructure, and damping properties and hardness. The result of microstructure experiment on Al-x%Si/y%Gr. composites reveals the good dispersion of graphite. As to Al-Si/y%Gr. composites, the more the graphite contents, the less the tensile strength. And the tensile strength varied according to contents of Si: with its highest value in Al-18%Si/y%Gr. composites and lowest in Al-6%Si/y%Gr. composites. As to Al-x%Si/y%Gr. composites, the more the contents of graphite, the more the vibration damping properties. And we can get the highest vibration damping rate in Al-12%Si/y%Gr. composites which matrix structure is an eutectic component.

• Journal of Korea Foundry Society
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• v.15 no.4
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• pp.368-376
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• 1995

An Al-composite material was fabricated with using the rheocompocasting process and the microstructure of the Al-Cu/SiCp composite material was investigated depending on the stirring times and the amount of Ti additions. The distribution of SiC dispersion shows the good result at the stirring time of 30 min. The degree of microdistribution of the $Al_2Cu$ and SiCp is improved when the amount of Ti addition is increased. At the compositon of 0.3%Ti, the primary solid is the compound of $Al_3Ti$ and no exist of the SiCp and $Al_2Cu$ phase around the primary $Al_3Ti$. In the process of compositization, SiCp is found at the primary and final solid parts and is found at the final solid part after remelting. $Al_2Cu$ and SiCp are distributed around and outside of dendrite or independently after remelting, which is different from the process of compositization.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.281-286
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• 2002

In odder to investigate the magnetic properties of CoCr-based bilayered thin films on kind of underlayer, we introduced amorphous Si layer to Co-Cr(-Ta) magnetic layer as underlayer. First, we prepared CoCr and CoCrTa single layer using the Facing Targets Sputtering system to investigate theirs properties. It was revealed that with increasing the film thickness of CoCr, CoCrTa single layer, crystalline orientation and perpendicular coercivity was improved. The CoCrTa thin film showed bettor crystalline and magnetic characteristics than CoCr thin film. As a result of investigating magnetic properties of CoCr and CoCrTa magnetic layer on introducing the Si underlayer, perpendicular coercivity and saturation magnetization of CoCr/Si and CoCrTa/Si bilayered thin film were decreased due to the increased grain size and diffusion of Si atoms to magnetic layer. And they showed constant with increasing the film thickness of Si thin film. However, in case of CoCrTa/Si bilayered thin film, in-plane coercivity was controlled low at about 250Oe. The c-axis orientations of CoCr/si and CoCrTa/Si bilayered thin film showed a good crystalline characteristics as about $2^{\circ}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.894-899
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• 2002

In this papers, we proposed the new method in order to diagnosis partial discharge type of transformers. For wavelet transform, Daubechies filter is used, we can obtain wavelet coefficients which is used to extract feature of statistical parameters (maximum value, average value, dispersion, skewness, kurtosis) about high frequency current signal per 3-electrode type (needle-plane electrode, IEC electrode and Void electrode.). Also. these coefficients are used to identify Signal of internal partial discharge in transformer. As a result. from compare of high frequency current signal amplitude and average value. we are obtained results of IEC electrode> Void electrode> Needle-Plane electrode. otherwise. In case of skewness and kurtosis, we are obtained results of Void electrode> IEC electrode > Needle-Plane electrode. As Improved method in order to diagnosis partial discharge type of transformers, we use neural network.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.89-90
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• 2006

The CNTs are of great interest because of their unique complete properties of matter, especially, the large thermal conductivity (Thermal conductivity of CNTs ~ >2000W /mK vs. Thermal conductivity of Aluminum ~ >204W/mK). However, owing to the strong agglomeration cause by the vander wall's force, the CNTs are limited to applicate. In this study. we suggest a new method for CNTs dispersion. which are developed by the mechanical and chemical method. and then Cu was coated. This new process produces CNTs/Cu nanocomposite powders. The CNTs are homogeneously located within the Cu powders by chemical reaction. And the thermal properties of the CNTs/Cu nanocomposite were investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.176-177
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• 2006

Two kinds of alumina nanofluids are prepared by dispersing $Al_2O_3$ nanoparticles m transformer oil. The thermal conductivity of the nanoparticle-oil mixtures increases with particle volume fraction and thermal conductivity of the solid particle itself. The $Al_2O_3$ nanoparticles at a volume of 0.5% can increase the thermal conductivity of the transformer oil by 5.7%, and the overall heat transfer coefficient by 20%. From the natural convection test using a prototype transformer, the cooling effect of $Al_2O_3$-oil nanofluids on the heating element and oil itself is confirmed. However, excessive quantities of the surfactant have a harmful effect on viscosity, and thus it is strongly recommended to control the addition of the surfactant with great care.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.164-165
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• 2006

Carbon nanotube(CNT)-reinforced poly(ethylene-co-ethyl acrylate)(EEA) nanocomposites were prepared by melt mixing with a Haake internal mixer. The CNT loading was vaned from 0 to 20 wt%. The changes m CNT dispersion and shape were investigated with FE-SEM observation with and without the Tensile strain of 40%. The CNT was protruded over the fracture surface upon Tensile strain, which is a very interesting behavior.

• Transactions on Electrical and Electronic Materials
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• v.4 no.2
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• pp.1-4
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• 2003

The purpose of this study was to investigate the characteristics of slurry including phosphoric acid for chemical-mechanical planarization of copper and tantalum nitride. In general, the slurry for copper CMP consists of alumina or colloidal silica as an abrasive, organic acid as a complexing agent, an oxidizing agent, a film forming agent, a pH control agent and additives. Hydrogen peroxide (H$_2$O$_2$) is the material that is used as an oxidizing agent in copper CMP. But, the hydrogen peroxide needs some stabilizers to prevent decomposition. We evaluated phosphoric acid (H$_3$PO$_4$) as a stabilizer of the hydrogen peroxide as well as an accelerator of the tantalum nitride CMP process. We also estimated dispersion stability and zeta potential of the abrasive with the contents of phosphoric acid. An acceleration of the tantalum nitride CMP was verified through the electrochemical test. This approach may be useful for the development of the 2$\^$nd/ step copper CMP slurry and hydrogen peroxide stability.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1301-1307
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• 2004

Reduced pressure chemical vapor deposition(RPCYD) technology has been investigated for the growth of SiGe epitaxial films with two dimensional in-situ doped boron impurities. The two dimensional $\delta$-doped impurities can supply high mobility carriers into the channel of SiGe heterostructure MOSFETs(HMOS). Process parameters including substrate temperature, flow rate of dopant gas, and structure of epitaxial layers presented significant influence on the shape of two dimensional dopant distribution. Weak bonds of germanium hydrides could promote high incorporation efficiency of boron atoms on film surface. Meanwhile the negligible diffusion coefficient in SiGe prohibits the dispersion of boron atoms: that is, very sharp, well defined two-dimensional doping could be obtained within a few atomic layers. Peak concentration and full-width-at-half-maximum of boron profiles in SiGe could be achieved in the range of 10$^{18}$ -10$^{20}$ cm$^{-3}$ and below 5 nm, respectively. These experimental results suggest that the present method is particularly suitable for HMOS devices requiring a high-precision channel for superior performance in terms of operation speed and noise levels to the present conventional CMOS technology.