• Korean Journal of Materials Research
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• v.24 no.7
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• pp.370-374
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• 2014

Inorganic pigments have high thermal stability and chemical resistance at high temperature. For these reasons, they are used in clay, paints, plastic, polymers, colored glass and ceramics. $CoAl_2O_4$ nano-powder was synthesized by reverse-micelle processing the mixed precursor(consisting of $Co(NO_3)_2$ and $Al(NO_3)_3$). The $CoAl_2O_4$ was prepared by mixing an aqueous solution at a Co:Al molar ratio of 1:2. The average particle size, and the particle-size distribution, of the powders synthesized by heat treatment (at 900; 1,000; 1,100; and $1,200^{\circ}C$ for 2h) were in the range of 10-20 nm and narrow, respectively. The average size of the synthesized nano-particles increased with increasing water-to-surfactant molar ratio. The synthesized $CoAl_2O_4$ powders were characterized by X-ray diffraction analysis(XRD), field-emission scanning electron microscopy(FE-SEM) and color spectrophotometry. The intensity of X-ray diffraction of the synthesized $CoAl_2O_4$ powder, increased with increasing heating temperature. As the heating temperature increased, crystal-size of the synthesized powder particles increased. As the R-value(water/surfactant) and heating temperature increased, the color of the inorganic pigments changed from dark blue-green to cerulean blue.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.33-39
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• 2010

The moisture absorption properties such as diffusion coefficient and moisture content ratio of liquid type epoxy resin systems with the filler were investigated. Bisphenol A type and Bisphenol F type epoxy resin, Kayahard MCD as hardener and 2-methylimidazole as catalyst were used in these epoxy resin systems. The nano-sized spherical type fused silica as filler were used in order to study the moisture absorption properties of these liquid type epoxy encapsulant according to the change of filler size. The temperature of glass transition (Tg) of these epoxy resin systems was measured using Dynamic Scanning Calorimeter (DSC), and the moisture absorption properties of these epoxy resin systems according to the change of time were observed at $85^{\circ}C$ and 85% relative humidity condition using a thermo-hygrostat. The diffusion coefficients in these systems were calculated in terms of modified Crank equation based on Ficks' law. An increase of Tg and diffusion coefficient with filler size in these systems can be observed, which are attributed to the increase of free volume with Tg. The change of maximum moisture absorption ratio according to the filler size and filler content cannot be observed; however, the diffusion coefficients of these systems decreased with filler content. The diffusion via free volume is dominant in the epoxy resin systems with low nano-sized filler content; however, the diffusion with the interaction of absorption according the increase of the filler surface area is dominant in the liquid type epoxy encapsulant with high nano-sized filler content.

• Advances in nano research
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• v.12 no.5
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• pp.467-482
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• 2022

In the current work, static and free torsional vibration of functionally graded (FG) nanorods are investigated using Fourier sine series. The boundary conditions are described by the two elastic torsional springs at the ends. The distribution of functionally graded material is considered using a power-law rule. The systems of equations of the mechanical response of nanorods subjected to deformable boundary conditions are achieved by using the modified couple stress theory (MCST) and taking the effects of torsional springs into account. The idea of the study is to construct an eigen value problem involving the torsional spring parameters with small scale parameter and functionally graded index. This article investigates the size dependent free torsional vibration based on the MCST of functionally graded nano/micro rods with deformable boundary conditions using a Fourier sine series solution for the first time. The eigen value problem is constructed using the Stokes' transform to deformable boundary conditions and also the convergence and accuracy of the present methodology are discussed in various numerical examples. The small size coefficient influence on the free torsional vibration characteristics is studied from the point of different parameters for both deformable and rigid boundary conditions. It shows that the torsional vibrational response of functionally graded nanorods are effected by geometry, small size effects, boundary conditions and material composition. Furthermore, for all deformable boundary conditions in the event of nano-sized FG nanorods, the incrementing of the small size parameters leads to increas the torsional frequencies.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2008.04a
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• pp.63-65
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• 2008

The functional non-woven fabrics have been applied in various industry fields, such as clothing, hygiene, environment, medical and so forth. The functional non-woven fabrics were manufactured by meltblown and finishing processes. These functional non-woven fabrics were made of 2,000ppm nano-silver resin composite and polypropylene resin. Silver is one of the most universal antimicrobial substances. Nano-technology enables us to expand the surface area of silver particles markedly. Nano-silver particles were successfully produced less than 10nm in size. The functional non-woven fabrics including nano-silver particles showed excellent antibacterial activities against Staphylococcus aureus(ATCC 6538) and Klebsieila pneumoniae (ATCC 4352). From the results, nano-silver particels probably will be available as a good and safe antibiotic alternative.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.251-251
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• 2009

The generation of energy and the cooling of system using thermoelectric semiconductor material have been in spotlight. Thermoelectric effect increases with the decrease of the thermal conductivity. In the thermoelectric devices, thermal conductivity is related to phonon scattering. Therefore, few studies have been conducted in the thermoelectric materials dispersed nano oxide particle for increasing the phonon scattering. However, core-shell structure which nano particle disperses in solvents and then which thermoelectric materials coated on the nano oxide particles has not been reported. In this study, we selected commercial nano powder such as $Al_2O_3$. This nano particle was about 20nm and was crushed aggregate by mechanical treatment. We have developed the effect of the dispersant and the solvent. The properties of particles were evaluated by SEM, TEM, particle size analysis, and BET. Dispersion and dispersion stability were evaluated by electronic microscope and turbidity.

• Fibers and Polymers
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• v.7 no.2
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• pp.169-173
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• 2006

Six nano disperse dyes were prepared using corresponding O/W nanoemulsions which were obtained with sodium laurylsulphate and caprylic triglyceride. The average particle size of the dyes prepared were in the range of $110{\sim}130nm$. Exhaust dyeing using nano dyes resulted in low exhaustion yields of $17{\sim}26%$ on regular polyester fiber and $28{\sim}38%$ on ultramicrofiber polyester. The observed low exhaustion yields of nano disperse dye can be explained by the solubilization of dye particles into surfactant micelles as well as the high stability of the nanoemulsions, these might reduce the capacity of dye uptake onto the fibers. However, higher K/S values of dyeings with nano dyes on ultramicrofiber sites compared to those on regular polyester sites suggested their potential to be more efficient dyes for finer denier microfiber polyesters.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.389-392
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• 2008

High purity carbon nano fibers/tubes (CNF/Ts) which contain 97% pure graphitic carbon are prepared by a new catalytic method. These carbon nano fibers/tubes are ready to use without any further purification. The striking feature of this method is the production of carbon nano fibers/tubes of narrow distribution range. The developed catalytic method also produces pure hydrogen. An additional advantage of this catalytic method is that catalyst can be reused without reactivation. Ni:Cu catalyst system is embodied into SCHOTT-DURAN filter disc of large pore size (40-100 mm). Due to the production of hydrogen in the reaction catalyst stability is enhanced and deactivation process is considerably slowed down.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1211-1212
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• 2006

The electrophoretic deposition process of Ni nano-particles was employed for self-repairing of heat exchanger tubes. For electrophoretic deposition of Ni nano-particles on pitted Ni alloy specimen, a constant electric field of 100 V $cm^{-1}$ was applied to the specimen for 180 s in Ni-dispersed solution. It was found that as electrophoretic deposition proceeded, the size of the pit remarkably decreased due to the agglomeration of Ni nano-particles at the pit. This strongly suggests that the electrophoretic mobility of the charged particles is larger for the pit with a higher current value rather than outer surfaces with a lower current value.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.565-570
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• 2016

In this work, the complex permittivity of epoxy resins is measured. Epoxy resins, epoxy with micro size fillers and epoxy with micro+nano alumina composites have been evaluated for dielectric properties according to frequency variation. The dielectric spectroscopy measurement and analyses are carried out in the frequency range of $10^{-2}Hz$ to 1MHz and constant to room temperature. The results of dielectric loss suggest that significant improvement in the electrical performance can be expected by using samples containing nano and micro fillers mixture when compared to materials containing only microfillers. As the result, we verified the specific characteristics of dielectric permittivity and dielectric loss namely, relative permittivity become low with improving dispersibility of nano+micro mixture composites and become rise with agglomerate of nano particles.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.237-240
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• 2005

The demand of micro electrical mechanical system (MEMS) bio/chemical sensor is rapidly increasing. To prevent the contamination of sensing area, a filtration system is required in on-chip total analyzing MEMS bio/chemical sensor. A nano-filter was mainly applied in some application detecting submicron feature size bio/chemical products such as bacteria, fungi and so on. We suggested a simple nano-filter fabrication process based on replication process. The mother pattern was fabricated by holographic lithography and reactive ion etching process, and the replication process was carried out using polymer mold and UV-imprinting process. Finally the nano-filter is obtained after removing the replicated part of metal deposited replica. In this study, as a practical example of the suggested process, a nano-dot array was replicated to fabricate nano-filter fur bacteria sensor application.