• Journal of Magnetics
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• v.15 no.4
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• pp.173-178
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• 2010

A new kind of magnetic rubber, Fe dispersed ethylene propylene monomer (EPM), was prepared by a conventional technique using a two roll mill. The magnetic fillers of Fe-nanoparicles were coated by low density polyethylene (LDPE). The purpose of surface treatment of nanoparticles by LDPE is to enhance wettability and lubricancy of the fillers in a polymer matrix. The mechanical strength and microstructure of the magnetic rubber were characterized by tensile strength test and scanning electron microscopy (SEM). Results revealed that the Fe nanoparticles were relatively well dispersed in an EPM matrix. It was found that the nano- Fe dispersed magnetic rubber showed higher coercivity and tensile strength than those of micron- Fe dispersed one.

• Journal of the Korean institute of surface engineering
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• v.28 no.3
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• pp.123-132
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• 1995

While a nickel mesh and an expanded nickel sheet are used as current collectors for supporting active anode materials in rechargeable batteries, a porous nickel substrate is studied extensively for its 3-dimensional structure which has high capabilities for active materials and current collection. Optimum plating conditions were studied by polarization measurement. Scanning Electron Microscopy (SEM) showed that both electroless-and electro-plated nickel on an urethane substrate were highly porous and consisted of nearly spherical pores. The diameter and the channel size of the pores were found to be 300~500 $\mu\textrm{m}$ and 50~200$\mu\textrm{m}$, respectively. The shape of skeleton resembled a triangular prism with length extending about 50~100 $\mu\textrm{m}$.

• Macromolecular Research
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• v.16 no.4
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• pp.314-319
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• 2008

An image analysis processing method for the measurement of nanofiber diameter was developed. For the analysis, scanning electron microscopy (SEM) images of electrospun fiber were prepared and applied to the individual measurement of the fiber diameter by using the developed and the traditional manual methods. Both methods provided a similar fiber distribution. The fiber average diameters were similar but the variance of the new method was larger than that of the manual method. The average diameters from the two methods exhibited a linear relationship with a high coefficient. The developed method can be used as a practical tool to estimate the fiber diameter of the electro spun web.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.302-306
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• 2019

We investigated a solution-derived $Y_2O_3$ film treated by ion beam (IB) irradiation as a liquid crystal (LC) alignment layer. With IB irradiation, homogeneous LC alignment was achieved irrespective of the annealing temperature. To verify the effect of IB irradiation, we conducted surface analyses such as X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As $Y_2O_3$ is a high-k material, the electro-optical properties of the twisted nematic (TN) cells were superior to those of conventional TN cells based on a rubbed polymer, with an LC rising time of 4.1ms and falling time of 2.9ms. The IB-irradiated $Y_2O_3$ is a good alternative as an alignment layer for fast-switching TN LC displays.

• Korean Journal of Materials Research
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• v.26 no.7
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• pp.393-399
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• 2016

Flower-like nickel oxide (NiO) catalysts were coated on NiCrAl alloy foam using a hydrothermal method. The structural, morphological, and chemical bonding properties of the NiO catalysts coated on the NiCrAl alloy foam were investigated by field-emission scanning electron microscopy, scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, respectively. To obtain flower-like morphology of NiO catalysts on the NiCrAl alloy foam, we prepared three different levels of pH of the hydrothermal solution: pH-7.0, pH-10.0, and pH-11.5. The NiO morphology of the pH-7.0 and pH-10.0 samples exhibited a large size plate owing to the slow reaction of the hydroxide ($OH^-$) and nickel ions ($Ni^+$) in lower pH than pH-11.5. Flower-like NiO catalysts (${\sim}4.7{\mu}m-6.6{\mu}m$) were formed owing to the fast reaction of $OH^-$ and $Ni^{2+}$ by increased $OH^-$ concentration at high pH. Thus, the flower-like morphology of NiO catalysts on NiCrAl alloy foam depends strongly on the pH of the hydrothermal solution.

• Macromolecular Research
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• v.12 no.2
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• pp.195-205
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• 2004

We have synthesized new aromatic polyesters (DiPEG-HQ and DiPEG-BP) by condensation polymerization of a terephthalic acid derivative bearing a pendant oligo(oxyethylene) (DP = 7, MW = 350), which has a methoxy terminal group, and two different aromatic diols, hydroquinone and 4,4'-biphenoI. The synthesized polymers were characterized by differential scanning calorimetry (DSC), polarizing microscopy, and X-ray diffractometry for their liquid crystallinity (LC), thermal transitions, and structural morphologies in mesophases. The morphology of the LC phases depends strongly on the length of the rigid backbone repeating unit. The DiPEG-BP polymer having a longer repeating unit exhibits both layered and nematic structures before isotropization, whereas the DiPEG-HQ polymer having a shorter repeating unit shows only the layered structure in the mesophase. We found that the layer spacing for DiPEG-HQ is larger than that for DiPEG-BP. Both polymers easily form complexes with LiCF$_3$SO$_3$; we studied this complex formation by FT-IR spectroscopy. The layer spacing of the polymer-electrolyte composites increases upon increasing the amount of the lithium salt. The polymer/salt electrolyte mixtures we investigated at molar ratios of EO:salt in the range of 5-20 exhibit electrical conductivity values at 40$^{\circ}C$ of 2.4${\times}$10$\^$5/ and 1.1${\times}$10$\^$－5/ S/cm for DiPEG-HQ/LiCF$_3$SO$_3$ and DiPEG-BP/LiCF$_3$SO$_3$, respectively. At 80 $^{\circ}C$, these values are higher: 4.6${\times}$10$\^$－3/ and 1.1${\times}$10$\^$－4/ S/cm, respectively. The activation energy of conductivity depends strongly on the salt concentration.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.277.2-277.2
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• 2013

Petri dishes and glass slides have been widely used as general substrates for in vitro mammalian cell cultures due to their culture viability, optical transparency, experimental convenience, and relatively low cost. Despite the aforementioned benefit, however, the flat two-dimensional substrates exhibit limited capability in terms of realistically mimicking cellular polarization, intercellular interaction, and differentiation in the non-physiological culture environment. Here, we report a protocol of culturing embryonic rat hippocampal neurons on the electro-spun polymeric network and the results from examination of neuronal cell behavior and network formation on this culture platform. A combinatorial method of laser-scanning confocal fluorescence microscopy and live-cell imaging technique was employed to track axonal outgrowth and synaptic connectivity of the neuronal cells deposited on this model culture environment. The present microfiber-based scaffold supports the prolonged viability of three-dimensionally-formed neuronal networks and their microscopic geometric parameters (i.e., microfiber diameter) strongly influence the axonal outgrowth and synaptic connection pattern. These results implies that electro-spun fiber scaffolds with fine control over surface chemistry and nano/microscopic geometry may be used as an economic and general platform for three-dimensional mammalian culture systems, particularly, neuronal lineage and other network forming cell lines.

• Journal of the Korean Electrochemical Society
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• v.23 no.3
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• pp.66-72
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• 2020

In this study, the development of biosensors capable of bi-enzyme reactions by including Horseradish peroxidase and glucose oxidase was carried out for detection of glucose. The sensors were manufactured using electro deposition method to reduce production time, and screen printed electrodes (SPE) were used to produce economical sensors. To check the bienzyme effect, the sensor was compared and analyzed with single enzyme biosensor. The characteristics of the sensor were evaluated using scanning electron microscopy(SEM), cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), chronoamperometry(CA), and flow injection analysis(FIA). Analysis results from SEM, CV and EIS confirmed that the enzymes are well fixed to the electrode surface. In addition, it was confirmed that bi-enzyme biosensors manufactured from the CA method improved signal performance by 200% compared to single enzyme biosensors. From this results, we were able to explain that HRP and GOD react catalyzed to each other. And the results of FIA showed that the intensity of each current signal was constant when the same concentration of glucose was injected four times. In addition, by analyzing the intensity of current signals for glucose concentrations, the biosensors manufactured in this study showed excellent trends in signal sensitivity, reproducibility and stability.

• Current Photovoltaic Research
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• v.4 no.1
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• pp.16-20
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• 2016

$Cu_2ZnSnS_4$ (CZTS) thin films were fabricated by successive electrodeposition of layers of precursor elements followed by sulfurization of an electrodeposited Cu-Zn-Sn precursor. In order to improve quality of the CZTS films, we tried to optimize the deposition condition of absorber layers. In particular, I have conducted optimization experiments by changing the Cu-layer deposition time. The CZTS absorber layers were synthesized by different Cu-layer conditions ranging from 10 to 16 minutes. The sulfurization of Cu/Sn/Zn stacked metallic precursor thin films has been conducted in a graphite box using rapid thermal annealing (RTA). The structural, morphological, compositional, and optical properties of CZTS thin films were investigated using X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and X-ray Flourescenece Spectrometry (XRF). Especially, the CZTS TFSCs exhibits the best power conversion efficiency of 4.62% with $V_{oc}$ of 570 mV, $J_{sc}$ of $18.15mA/cm^2$ and FF of 45%. As the time of deposition of the Cu-layer to increasing, the properties were confirmed to be systematically changed. And we have been discussed in detail below.

• Journal of the Korean institute of surface engineering
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• v.37 no.5
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• pp.253-262
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• 2004

Calcareous deposits are the consequence of pH increase of the electrolyte adjacent to metal surface affected by cathodic current in seawater. It obviously has several advantages over conventional coatings, since the calcareous deposit coating is formed from coating (Mg$^{2+}$, $Ca^{2+}$) naturally existing in seawater. In consideration of this respect, environment friendly calcareous deposit films were formed by an electro deposition technique on steel substrates submerged in 48$^{\circ}C$ natural seawater. And the influence of current density, coating time and attachment of steel mesh on composition ratio, structure and morphology of the electrodeposited films were investigated by Scanning Electron Microscopy(SEM), Energy Dispersive Spectroscopy(EDS) and X-Ray Diffractor(XRD), respectively. Accordingly, this study provides a better understanding of the composition between the growth of $Mg(OH)_2$ and $CaCO_3$ during the formation of electro deposit films on steel substrate under cathodically electrodeposition in $48^{\circ}C$ natural seawater. The Mg compositions, in general, are getting decreased regardless of current density but Ca compositions are getting increased as electrodeposition time runs. That is, $Mg(OH)_2$ compounds of brucite structure shaped as flat type is formed at the initial stage of electrodeposition, but CaCO$_3$ compounds of aragonite structure shaped as flower type is formed in large scale. Besides, $Mg(OH)_2$ compounds were much formed at 5 A/$\m^2$ environment condition compared to the 3 A/$\m^2$ and 4 A/$\m^2$ environment conditions. This is because that OH- which was comparatively largely generated at the metal surface is preferably combined with $Mg^{2+}$TEX>.