• Polymer(Korea)
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• v.34 no.2
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• pp.97-103
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• 2010

PMMA was grafted on MWCNT surface in order to prepare conducting film composed of 6FDAbased polyimide/MWCNT. The electrical conductivity of 6FDA-based polyimide/PMMA-g-MWCNT was investigated as a function of PMMA-g-MWCNT content. Dispersion of MWCNT in 6FDA-based polyimide composite film was better than the pristine MWCNT due to the interaction force between PMMA and 6FDA-based polyimide. Electrical conductivity was interpreted by percolation threshold theory. As a result, 6FDA-6FpDA/PMMA-g-MWCNT which have high critical exponents and low critical concentration showed better dispersion than polyimide composite material that contains DABA(diamino benzoic acid).

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1447-1449
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• 1998

The c-axis orientation plays a very important role in controlling the main parameters of the perpendicular magnetic recording media, such as perepndicular magnetic anisotropy field $H_{K{\bot}}$, the ratio of coercive force $H_{C{\bot}}/H_{C//}$, the recording density $D_{50}$, and the dispersion of the c-axis orientation $\Delta\theta_{50}$, which is quite important for the performance as perpendicular recording media, as well as the magnetic properties of the film. In this study, the essential process requirement for preparing the Co-Cr films with the superior c-axis orientation, the dependence of $\Delta\theta_{50}$ and the magnetic properties on the film thickness $\delta$, and the effect of underlayer on the dispersion of c-axis orientation have been investigated for both the FTS and DCM system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.131-136
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• 2011

Many researchers are recently studying about Electroactive polymer(EAP). But it has a physical limitation, because of property of material. Carbon nanotube(CNT) is known as the promising material which has excellent electro-mechanical characteristics and is mostly defect-free. It is expected that a successful synthesis of CNT and Nafion known as a primary material for IPMC would make a great improvement on its electro-mechanic feature. This study focuses on the method of synthesis of CNT with Nafion which improves electro-mechanical characteristic. To come up with mechanical dispersion with Nafion and Isopropyl Alcohol(IPA), we dispersed Single-walled carbon nanotubes(SWCNTs). For a uniformly layer of CNT, we used a spray gun on a hot plate by a simplified method. We fabricated a disperse SWCNT/Nafion composite uniformly. Through the use of the E-beam evaporator to form an uniform electrode layer, we consummated the IPMC actuator. This result shows improving 1.5 times mechanical properties about driving force in IPMC.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.2 s.119
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• pp.168-176
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• 2007

The mixture sound speed in bubbly fluids is highly dispersive due to differences of the density and compressibility between bubbles and fluids. The dispersion range in bubbly fluids expands to a higher frequency than the resonance frequency of an air bubble. A theoretical model was developed to compute the reduction of radiation noise that is generated by a force applied on an infinite flat plate using a bubble layer as a compliant baffle. For evaluating the effectiveness of a bubble layer in reducing the structure-borne noise of an infinite elastic plate, the noise reduction levels for various parameters such as the thickness of bubble layers, the volume fractions and the distribution types of bubbly fluids are calculated numerically. The noise reduction effect of an air bubble layer on an infinite flat plate is considerable level and similar to the tendency of dispersion of bubbly fluids. It is recommended that the thickness of a bubble layer should be increased with keeping an appropriate volume fraction of an air bubble for the most effective reduction of the radiation noise.

• Corrosion Science and Technology
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• v.18 no.1
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• pp.16-23
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• 2019

Steels for automotive fuel tank require unique properties such as corrosion resistance for fuel, welding for joining, forming for press, and painting for exterior. Recently, automakers have been requiring excellent seam weldable steels to enhance manufacturing productivity of fuel tank. Thus, POSCO developed a new type of functional steels coated with nano-composite thin layer on Zn-Ni plating steels. The nano-composite coating solution was prepared by mechanical fine dispersion of solutions consisting of polymeric resin and nano-composite materials in aqueous media. The composite solution was coated on the plating steel surface by using roll coater and cured through induction furnace. These new developed plating steels were evaluated for quality performances such as seam and spot weldability, press formability, and corrosion resistance. These new functional steels coated with nano-composite layer exhibited excellent seam weldability and press formability. Detailed discussion of coating solution and experimental results suggest that nano-sized composite dispersion as coating layer plays a key role in enhancing the quality performance.

• Journal of the Korean Ceramic Society
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• v.46 no.2
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• pp.175-180
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• 2009

Multilayer ceramic capacitors (MLCCs) have continually been made smaller in size and larger in capacity in resent years. However, the end termination electrode is still thick in many MLCCs. In this study, we used small grain glass frit to embody thin film and highly densification in the end termination by improve sintering driving force with well-dispersion and rising surface energy. Pastes were fabricated using size changed glass frit, such as 0.1 ${\mu}m$, 0.5 ${\mu}m$, 1.0 ${\mu}m$, 4.0 ${\mu}m$. Fabricated pastes were applied 05A475KQ5 chip and fired various sintering temperatures to analyze sintering behavior of pastes. Consequently, small glass frit used pastes have many merits than larger, such as well-dispersion, improve cornercoverage and surface roughness, possibility of low temperature sintering. However, we confirmed that small glass frit used pastes have narrow sintering window by rapid completion of sintering densification.

• Particle and aerosol research
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• v.11 no.2
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• pp.29-36
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• 2015

The purpose of this research is to find out the collection property of nanoparticle in diffusion filter to know particle size dispersion of nanomaterial using inertial force and principle of Brownian diffusion motion. We used inertial filters which are two different type and diffusion filters made by various kinds of Wiremesh and the different pieces of filter to compare with particle size distribution using NaCl particles. Finally, We made a conclusion as follows : (1) the bigger available charging volume is and the larger specific surface area of inertial filter is, the better collection efficiency is. (2) The higher wire-mesh number of filter is, the more collection efficiency of small particle is increasing because the wire of the higher Wiremesh number filter is thinner and denser. (3) The more pieces of wire-mesh filter, the more collection efficiency is increasing because it makes the residence time longer.

• Journal of Powder Materials
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• v.21 no.6
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• pp.429-433
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• 2014

This study investigated the magnetic properties and frequency dispersion of complex permeability of Ni-Zn-Co ferrites used for magnetic shielding in near field communication (NFC) system. The sintered specimens of $(Ni_{0.7}Zn_{0.3})_{1-x}Co_xFe_2O_4$ composition were prepared by the conventional ceramic processing. The coercive force and saturation magnetization were measured by vibrating sample magnetometer. The complex permeability was measured by RF impedance analyzer in the range of 1 MHz~1.8 GHz. The coercive force increased and saturation magnetization decreased with increasing the Co substitution. The real and imaginary parts of complex permeability decreased and the resonance frequency increased with Co substitution, which was attributed to the increase in crystal anisotropy field and reduction in saturation magnetization. The effect of Co substitution could be found in reducing the magnetic loss to nearly zero at the operating frequency of NFC (13.56 MHz).

• Textile Coloration and Finishing
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• v.1 no.1
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• pp.7-18
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• 1989

The distinguishing characteristic of the glow discharge is that chemical reaction induced by partially ionized gases are limited only to the substrate surface. Most studies have been done on the plasma etching and polymerization. The graft polymerization in vapour phase by cold plasma has been rarely investigated. In this study the system of tub3ar reaction chamber with capacitively coupled electrode of alternative current of 60 Hz was employed for the graft polymerization. The graft polymerization of Acylic Acid(AA) onto the poly (ethylene terephthalate) (PET) was carried out by treatment of PET film and fabric by cold plasma (glow discharge of argon gas), followed by the supply of AA vapour. The graft yield was about 1 wt%. The surface property was determined by contact angle, the surface tension was evaluated by zisman’s plot and equation of surface tension mesurement. The results were as follows: 1. In order to obtain lower contact angle, it was effective to avoid the vicinity of electrodes for a setting position of substrate. 2. Contact angle affected on the monomer pressure and its duration of exposure to the acid vapour. 3. Polymer radical formation was influenced by the changes of the value of current density and plasma treatment time. 4. Total surface tension of plasma grafted PET film increased. With an increase in the carboxylic acid content, the dispersion force decreased, while, the polar force and hydrogen bonding force increased. 5. The contact angle decreased from $75^\circ$ to around $30^\circ$ by plasma grafting. There was no ageing effect on the contact angle after 4 months.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.227-232
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• 2008

In this research, organic extracts from roots of platycodon grandiflorum was tested to see the possibility for cosmetic natural surfactant. Interfacial properties of extracts of Platycodon grandiflorum was checked for interfacial tension, forming force, dispersion force, emulsion force, emulsion activity, and emulsion stability. At 0.005 wt% concentration, the interfacial tension against the caster oil was 11.5 dyn/cm which was lower than that of Tween 40 and quillaja bark. Extracts of Platycodon grandiflorum showed excellent emulsification activity and stability for cosmetic oils such as olive oil, soybean oil, and canola oil. In patch test using 2-5% of the extract and glycerin, the extract showed mild skin irritation. From the experiment, the extracts of platycodon grandiflorum root showed good interfacial properties as a cosmetic agent with minor skin irritation.