• Journal of the Korean Applied Science and Technology
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• v.33 no.1
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• pp.1-12
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• 2016

This study is to make the liquid crystalline structure using sucrose distearate (Sucro-DS) emulsifier to create the hydrophilic type oil-in-water (O/W) emulsion, the droplets of the emulsion having a structure of a multi-lamellar structure. We have studied the physicochemical properties of Sucro-DS using those techniques. And it has been studied in the emulsion performance. In order to form the liquid crystalline structure applying 3 wt% of Sucro-DS, 5 wt% of glycerin, 5 wt% of squalane, 5 wt% of capric/caprylic triglyceride, 3wt% of cetostearyl alcohol, 1wt% of glyceryl mono-stearate, 78 wt% of pure water in mixture having the lamellar structure of stable multi-layer system was found to formed. By applying them, they were described how to create an unstable active material encapsulated cream. Further, the moisturizing cream was studied using this technique. It reported the results to the skin improvement effect by the human clinical trials. The pH range to produce a stable liquid crystal phase using a Sucro-DS was maintained in 5.2~7.5. In order to increase the stability of the liquid crystal, it was when behenyl alcohol containing 3 wt%, the hardness at this time was 13 kg/mm,min. Viscosity of the same amount was 25,000mPas/min. After a test for the effects of the emulsions, the concentration of 6 wt% Sucro-DS is that was appropriate, the particle size of the liquid crystal was 4~6mm. It was observed through a microscope analysis, reliability of the liquid crystal changes for 3 months was found to get stable at each $4^{\circ}C$, $25^{\circ}C$ and $45^{\circ}C$. In clinical trial test, before applying a moisturizing effect it was $13.4{\pm}7%$. Moisturizing cream liquid crystal was not formed in $14.5{\pm}5%$. Therefore, applying than ever before could see the moisture about 8.2% was improved. On the other hand, it was the moisturizing effect of the liquid cream is $19.2{\pm}7%$. The results showed that 43.3% improvement than that previously used. Applications fields, Sucro-DS emulsifier used liquid cream, lotion, eye cream and a variety of formulations can be developed, as well as the cosmetics industry is expected to be wide fields in the application of the external preparation for skin emulsion technology in the pharmaceutical industry and pharmaceutical industry.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.251-252
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• 2012

Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low Water Vapor Transition Rate (WVTR) of $1{\times}10^{-6}g/m^2$/day. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2$/day) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study, we developed an $Al_2O_3$ nano-crystal structure single gas barrier layer using a Neutral Beam Assisted Sputtering (NBAS) process. The NBAS system is based on the conventional RF magnetron sputtering and neutral beam source. The neutral beam source consists of an electron cyclotron Resonance (ECR) plasma source and metal reflector. The Ar+ ions in the ECR plasma are accelerated in the plasma sheath between the plasma and reflector, which are then neutralized by Auger neutralization. The neutral beam energies were possible to estimate indirectly through previous experiments and binary collision model. The accelerating potential is the sum of the plasma potential and reflector bias. In previous experiments, while adjusting the reflector bias, changes in the plasma density and the plasma potential were not observed. The neutral beam energy is controlled by the metal reflector bias. The NBAS process can continuously change crystalline structures from an amorphous phase to nano-crystal phase of various grain sizes within a single inorganic thin film. These NBAS process effects can lead to the formation of a nano-crystal structure barrier layer which effectively limits gas diffusion through the pathways between grain boundaries. Our results verify the nano-crystal structure of the NBAS processed $Al_2O_3$ single gas barrier layer through dielectric constant measurement, break down field measurement, and TEM analysis. Finally, the WVTR of $Al_2O_3$ nano-crystal structure single gas barrier layer was measured to be under $5{\times}10^{-6}g/m^2$/day therefore we can confirm that NBAS processed $Al_2O_3$ nano-crystal structure single gas barrier layer is suitable for OLED application.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.4
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• pp.31-37
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• 2017

Recently, there has been substantial interest in flexible and wearable devices whose properties and performances are close to conventional devices on hard substrates. Despite the advancement on flexible devices with organic semiconductors or carbon nanotube films, their performances are limited by the carrier scattering at the molecular to molecular or nanotube-to-nanotube junctions. Here in this study, we demonstrate on the vertical semiconductor crystal array embedded in flexible polymer matrix. Such structures can relieve the strain effectively, thereby accommodating large flexural deformation. To achieve such structure, we first established a low-temperature solution-phase synthesis of single crystalline 3D architectures consisting of epitaxially grown ZnO constituent crystals by position and growth direction controlled growth strategy. The ZnO vertical crystal array was integrated into a piece of polydimethylsiloxane (PDMS) substrate, which was then mechanically detached from the hard substrate to achieve the freestanding ZnO-polymer composite. In addition, the characteristics of transferred ZnO were confirmed by additional structural and photoluminescent measurements. The ZnO vertical crystal array embedded in PDMS was further employed as pressure sensor that exhibited an active response to the external pressure, by piezoelectric effect of ZnO crystal.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.157-157
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• 2015

Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low water vapor transition rate (WVTR) of $1{\times}10^{-6}g/m^2day$. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2day$) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study NBAS process was introduced to deposit enhanced film density single gas barrier layer with a low WVTR. Fig. 1. shows a schematic illustration of the NBAS apparatus. The NBAS process was used for the $Al_2O_3$ nano-crystal structure films deposition, as shown in Fig. 1. The NBAS system is based on the conventional RF magnetron sputtering and it has the electron cyclotron resonance (ECR) plasma source and metal reflector. $Ar^+$ ion in the ECR plasma can be accelerated into the plasma sheath between the plasma and metal reflector, which are then neutralized mainly by Auger neutralization. The neutral beam energy is controlled by the metal reflector bias. The controllable neutral beam energy can continuously change crystalline structures from an amorphous phase to nanocrystal phase of various grain sizes. The $Al_2O_3$ films can be high film density by controllable Auger neutral beam energy. we developed $Al_2O_3$ high dense barrier layer using NBAS process. We can verified that NBAS process effect can lead to formation of high density nano-crystal structure barrier layer. As a result, Fig. 2. shows that the NBAS processed $Al_2O_3$ high dense barrier layer shows excellent WVTR property as a under $2{\times}10^{-5}g/m^2day$ in the single barrier layer of 100nm thickness. Therefore, the NBAS processed $Al_2O_3$ high dense barrier layer is very suitable in the high efficiency OLED application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.5
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• pp.393-399
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• 2020

A series of phosphors, SrWO₄:5 mol% Dy³⁺, SrWO₄:5 mol% Sm³⁺, and SrWO₄:5 mol% Dy³⁺:x Sm³⁺ (x＝1~15 mol%), were prepared using a facile co-precipitation. The crystal structure, morphology, photoluminescence properties, and application in anti-counterfeiting fields were investigated. The crystalline structures of the prepared phosphors were found to be tetragonal systems with the dominant peak occurring at the (112) plane. The excitation spectra of the Dy³⁺ singly-doped SrWO₄ phosphors were composed of an intense charge-transfer band centered at 246 nm in the range of 210~270 nm and two weak peaks at 351 nm and 387 nm due to the ⁶H_15/2→⁶P_7/2 and ⁶H_15/2→⁴I_13/2 transitions of Dy³⁺ ions, respectively. The wavelength of 246 nm was optimum for exciting the luminescence of Dy³⁺ and Sm³⁺ co-doped SrWO₄ phosphors. The emission spectra consisted of two intense blue and yellow emission bands at 480 nm and 573 nm corresponding to the ⁴F_9/2→⁶H_15/2 and ⁴F_9/2→⁶H_13/2 transitions of Dy³⁺, and two strong emission peaks at 599 nm and 643 nm originating from the ⁴G_5/2→⁶H_7/2 and ⁴G_5/2→⁶H_9/2 transitions of Sm³⁺, respectively. As the concentration of Sm³⁺ ions increased, the emission intensities of Dy³⁺ rapidly decreased, while the emission intensities of Sm³⁺ gradually increased. These results suggest that the color of the emission light can be tuned from yellow to white by changing the concentration of Sm³⁺ ions at a fixed 5 mol% Dy³⁺. Furthermore, the fluorescent security inks were synthesized for use in anti-counterfeiting applications.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.35-41
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• 2004

This study investigated the crystal growth, crystalline structure and the basic optical properties of $PbSnSe/BaF_2$ epilayers. The PbSnSe epilayer was grown on $BaF_2$(111) insulating substrates using a hot wall epitaxy (HWE) technique. It was found from the analysis of X-ray diffraction patterns that $PbSnSe/BaF_2$ epilayer was grown single crystal with a rock-salt structure oriented along [111] the growth direction. Using Rutherford back scattering, the atomic ratios of the PbSnSe was found to be proper stoichiometric. The best values for the full width at half maximum (FWHM) of the DCXRD was 162 arcsec for PbSnSe epilayer. The epilayer-thickness dependence of the FWHM of the DCXRD shows that the quality of the $PbSnSe/BaF_2$ is as expected. The dielectric function ${\varepsilon}(E)$ of a semiconductor is closely related to its electronic energy band structure and such relation can be drawn from features around the critical points(CPs) in the optical spectra. The real and imaginary parts(${\varepsilon}1$ and ${\varepsilon}2$) of the dielectric function ${\varepsilon}$ of PbSe were measured, and the observed spectra reveal distinct structures at energies of the E1, E2 and E3 CPs. These data are analyzed using a theoretical model known as the model dielectric function (MDF). The optical constants related to dielectric function such as the complex refractive index ($n^*=n+ik$), absorption coefficient (${\alpha}$) and normal-incidence reflectivity (R) are also presented for $PbSnSe/BaF_2$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.2
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• pp.253-258
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• 2016

The $MnO_x-WO_3-TiO_2$ nanoscale powders were synthesized by sol-gel method in order to prevent the biological fouling on the ships and offshore structures. Powder characteristics and antifouling performance were investigated with respect to the crystalline, microstructure and surface property for application in self-polishing copolymer resins. The high antifouling activity of $TiO_2$-system biocide was attributed to its redox potential and soluble metal ions originating from tungsten oxides according to the improvements in the powder characteristics. Based on their physio-chemical characterizations, the specific surface areas of powders were about $90m^2/g$ and the grain size was in the region 100 ~ 150 nm. Powder characteristics and surface properties were improved by the addition of $WO_3$. Antifouling performance were analyzed according to their surface properties and static immersion tests to determine the effects of the $TiO_2$-system compounds. The surface of 2 wt. % added sample was clean for 5 month. This may be attributed to the ability of $MnO_x-WO_3-TiO_2$ powders to act as a promoter in antifouling agents.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.29-37
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• 2018

Bamboo is one of the major biomass resources in the world. To obtain valuable information for effective use of bamboo resources in Korea, the anatomical characteristics of the commercial Korean bamboo species (Phyllostachys pubescens, Phyllostachys nigra, and Phyllostachys bambusoides) were analyzed. The structures in bamboo culm were observed by optical and scanning electron microscopy. Also the crystalline properties as relative crystallinity and crystallite width were measured by an X-ray diffraction method. The three Korean bamboo species had the vascular bundle type I with tylosoid in intercellular space. In the outer part of culm, vascular bundles showed denser spacing than inner part. The fiber length in outer part samples of the three bamboo species showed longer than inner part samples. Furthermore, the fiber length showed a significant difference between inner part and outer part in three bamboo species, showing the longest fiber length in Phyllostachys bambusoides. Phyllostachys pubescens showed the greatest diameter in vessel and parenchyma on cross section. Parenchyma cells in Phyllostachys pubescens and Phyllostachys bambusoides showed similar length and width in both radial and tangential sections. The relative crystallinity and crystallite width in outer part samples of the three bamboo species showed higher values than those in inner part samples, with the greatest values from Phyllostachys bambusoides.

• Journal of the Korean Magnetics Society
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• v.20 no.5
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• pp.173-177
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• 2010

The electronic structure of charge-density-wave (CDW) system $CeTe_2$ has been investigated by using angle-resolved photoemission spectroscopy (ARPES). The clearly dispersive band structures are observed in the measured ARPES spectra, indicating the good quality of the single-crystalline sample employed in this study. The four-fold symmetric patterns are observed in the constant energy (CE) mappings, indicating the $2{\times}2$ lattice deformation in the Te(1) sheets. The observed CE images are similar to those of $LaTe_2$, suggesting that Ce 4f states have the minor contribution to the CDW formation in $CeTe_2$. This study reveals that the carriers near the Fermi level should have mainly the Te(1) 5p and Ce 5d character, that the Te(1) 5p bands contribute to the CDW formation, and that the Ce 5d bands cross the Fermi level even in the CDW state.

• Journal of Environmental Science International
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• v.18 no.3
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• pp.299-308
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• 2009

We manufactured PVA-derived hydrogels using a foam generation technique that has been widely used to prepare colloidal gas aphrons(CGA). These gels were differentiated to the conventional gels such as for medical or pharmaceutical applications, which have tiny pores and some crystalline structure. Rather these should be used in de-pollution devices or adhesion of cells or biomolecules. The crosslinkers used in this work were amino acid, organic acid, sugars and lipids(vitamins). The structures of the gels were observed in a scanned electron microscope. Amino acids gels showed remarkably higher swelling ratios probably because their typical functional groups help constructing a highly crosslinked network along with hydrogen bonds. Boric acid and starch would catalyze dehydration while structuring to result in much lower water content and accordingly high gel content, leading to less elastic, hard gels. Bulky materials such as ascorbic acid or starch produced, in general, large pores in the matrices and also nicotinamide, having large hydrophobic patches was likely to enlarge pore size of its gels as well since the hydrophobicity would expel water molecules, thus leading to reduced swelling. Hydrophilicity(or hydrophobicity), functional groups which are involved in the reaction or physical linkage, and bulkiness of crosslinkers were found to be more critical to gel's cross linking structure and its density than molecular weights that seemed to be closely related to pore sizes. Microscopic observation revealed that pores were more or less homogeneous and their average sizes were $20{\mu}m$ for methionine, $10-15{\mu}m$ for citric acid, $50-70{\mu}m$ for L-ascorbic acid, $30-40{\mu}m$ for nicotinamide, and $70-80{\mu}m$ for starch. Also a sensory test showed that amino acid and glucose gels were more elastic meanwhile acid and nicotinamide gels turned out to be brittle or non-elastic at their high concentrations. The elasticity of a gel was reasonably correlated with its water content or swelling ratio. In addition, the PVA gel including 20% ascorbic acid showed fair ability of cell adherence as 0.257mg/g-hydrogel and completely degraded phenanthrene(10 mM) in 240 h.