• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.1-6
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• 2017

Functional coatings, such as anti-reflection and self-cleaning, are frequently applied to cover glass for photovoltaic applications. Anti-reflection coatings made of mesoporous silica film have been shown to enhance the light transmittance. $TiO_2$ photocatalyst films are often applied as a self-cleaning coating. In this study, transparent hydrophobic anti-reflective and self-cleaning coatings made of $SiO_2/TiO_2$ thin layers were fabricated on a slide glass substrate by the sol-gel and dip-coating processes. The morphology of the functional coatings was characterized by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The optical properties of the functional coatings were investigated using an UV-visible spectrophotometer. Contact angle measurements were performed to confirm the hydrophobicity of the surface. The results showed that the $TiO_2$ films exhibit a high transmittance comparable to that of the bare slide glass substrate. The $TiO_2$ nanoparticles make the film more reflective and lead to a lower transmittance. However, the transmittance of the $SiO_2/TiO_2$ thin layers is 93.5% at 550 nm with a contact angle of $110^{\circ}$, which is higher than that of the bare slide glass (2.0%).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.237-241
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• 2014

We investigated the optimal etching conditions and properties of the surface change due to molten KOH/NaOH chemical wet etching using an AlN wafer which has been put to practical use in the present study. Results were observed using a scanning electron microscope after 5 minutes etching at $350^{\circ}C$, was found to have a surface form of the respective other Al-face, the N-face. In particular, etch-pit in the form of a hexagon, which is observed in the Al-face appeared, It was calculated at $2{\times}10^6/cm^2{\sim}10^{10}/cm^2$ dislocation density. In the case of N-face, lattice defects in the form of the hexagonal pyramids is formed. It was discovered that in order to observe the orientation of the wafer, which corresponds to the C-axis direction of the resulting hexagonal AlN which was analyzed using XRD (0002) and is a state of being oriented in the (0004) plane. The Radius of curvature of AlN wafer was 1.6~17 m measured by DC-XRD rocking curve position.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.197-204
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• 2016

Concrete walls of neutron generating facilities such as fusion reactors and fission reactors become radioactive by neutron irradiation. Both low-activation and neutron shielding are a critical concern at the dismantling stage after the shutdown of facilities with a requirement of radioactive waste management. To tackle this, two types of additives were investigated in fabricating mortar specimens: synthetic high polymers and boron carbide. It is well known that a hydrogen atom is effective in neutron shielding by an elastic scattering because its mass is almost the same as that of the neutron. And boron is an effective neutron absorber with a big neutron absorption cross section. In this study, the effect of the type, shape, and size of polymers were investigated as well as that of boron carbide. Total 16 mix designs were prepared to reveal the effect of polymers on mechanical properties and neutron shielding performance. The neutron does equivalent of polymers-based mortar for fast neutrons decreased by 36 %, and the count rate of boron carbide-based mortar with regard to thermal neutrons decreased by 90 % compared to conventional mortar. These results showed that a combination of polymers and boron carbide compounds has potential to reduce the thickness of neutron shields as well as radioactive waste from reactors.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.78-82
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• 2015

Hollow silica particles were prepared using sodium silicate and organic templates. Polystyrene latex (PSL) particles produced by dispersion polymerization were used as organic templates. PSL particles ranged from $1{\mu}m$ to $3{\mu}m$ in diameter were synthesized by adjusting the amount of 2,2'-azobisisobutyronitrile (AIBN). The PSL/$SiO_2$ core-shell particles were prepared by coating of silica nanoparticles originated from sodium silicate using sol-gel method. The organic templates were removed by the organic solvent, tetrahydrofuran (THF). Morphology of hollow silica particles was investigated with respect to types of the reaction medium and pH during the process. By changing the solvent from ethanol to water, hollow silica particles were successfully formed. Hollow silica particles with the uniform shell thickness were produced at low pH as well. The reflectivity of the as-prepared silica particles was measured in the range of the wavelength of UV and visible light. Hollow silica particles showed much better reflective properties than the commercial light reflector, Insuladd.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.37-40
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• 1998

Fe량을 0 - 0.4 wt.%까지 변화시켜 Zr-Fe 이원계 합금을 진공아크용해로 제조한 후 1050 $^{\circ}C$에서 30분 균질화 처리 및 700 $^{\circ}C$에서의 열간압연, 그리고 2회의 걸친 냉간압연 및 열처리를 통하여 판재로 제조되었다. 중간 열처리 시 열처리 온도 및 시간을 조절하여 최종 냉간가공에 앞서 각 시편의 결정립 크기 및 경도 값이 같도록 조절하였다. 최종 냉간가공 시 냉간가공량을 60%로 동일하게 조절하였고, 최종열처리 시 열처리 온도 및 시간을 300-750 $^{\circ}C$, 5-3000분으로 각각 변화시켰다. 재결정 정도는 미세조직 관찰 및 경도 측정으로 평가되었으며, 석출물의 구조, 분포 및 형상 등도 TEM으로 분석되었다. 0.1 wt.% 정도까지의 Fe 첨가는 Fe를 첨가하지 않은 순수지르코늄에 비하여 지르코늄입자의 빠른 성장을 야기해, 조대한 재결정 지르코늄 입자들이 나타났다. 그러나 Fe 첨가량이 0.1wt.%이상 첨가되면, Zr$_3$Fe 석출물에 의한 입자성장 억제효과로 지르코늄 입자의 크기는 오히려 작아졌다. 결론적으로, Fe의 첨가는 지르코늄의 확산을 가속시켰다는 것을 보여준다. 한편, 750 $^{\circ}C$에서 열처리 시 이차 재결정현상으로 지르코늄 입자가 비정상적으로 매우 커졌으며, 동시에 annealing twining 현상이 관찰되었다. 이러한 annealing twining 현상은, 입자성장속도가 임계치 이상으로 갑자기 커진, Zr$_3$Fe 석출물이 거의 없는 합금에서만 나타났다. 이 결과를 토대로 annealing twining 현상은 입자의 빠른 이동이 필요 조건이라는 결론을 도출하였다. .Ar-4vol.%H$_2$ 분위기보다 H$_2$분위기에서 소결했을 때 밀도가 더 높았다. 그러나, 결정립은 $UO_2$와 $UO_2$-Li$_2$O의 경우, 수소분위기에서 소결했을 때, (U,Ce)O$_2$와 (U,Ce)O$_2$-Li$_2$O에서는 Ar-4vol.%H$_2$분위기에서 소결했을 때 더욱 성장하였다.설명해 줄 수 있다. 넷째, 불규칙적이며 종잡기 힘들고 단편적인 것으로만 보이던 중간언어도 일정한 체계 속에서 변화한다는 사실을 알 수 있다. 다섯째, 종전의 오류 분석에서는 지나치게 모국어의 영향만 강조하고 다른 요인들에 대해서는 다분히 추상적인 언급으로 끝났지만 이 분석을 통 해서 배경어, 목표어, 특히 중간규칙의 역할이 괄목할 만한 것임을 가시적으로 관찰할 수 있 다. 이와 같은 오류분석 방법은 학습자의 모국어 및 관련 외국어의 음운규칙만 알면 어느 학습대상 외국어에라도 적용할 수 있는 보편성을 지니는 것으로 사료된다.없다. 그렇다면 겹의문사를 [-wh]의리를 지 닌 의문사의 병렬로 분석할 수 없다. 예를 들어 누구누구를 [주구-이-ν가] [누구누구-이- ν가]로부터 생성되었다고 볼 수 없다. 그러므로 [-wh] 겹의문사는 복수 의미를 지닐 수 없 다. 그러면 단수 의미는 어떻게 생성되는가\ulcorner 본 논문에서는 표면적 형태에도 불구하고 [-wh]의미의 겹의문사는 병렬적 관계의 합성어가 아니라 내부구조를 지니지 않은 단순한 단어(minimal $X^{0}$ elements)로 가정한다. 즉, [+wh] 의미의 겹의문사는 동일한 구성요 소를 지닌 병렬적 합성어

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.705-713
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• 2017

A novel material, $Bi_2WO_6-GO-TiO_2$ composite, was successfully synthesized using a facile hydrothermal method. During the hydrothermal reaction, the loading of $Bi_2WO_6$ and $TiO_2$ nanoparticles onto graphene sheets was achieved. The obtained $Bi_2WO_{6-GO-TiO2}$ composite photo-catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis-DRS), and X-ray photoelectron spectroscopy (XPS). The $Bi_2WO_6$ nanoparticle showed an irregular dark-square block nanoplate shape, while $TiO_2$ nanoparticles covered the surface of the graphene sheets with a quantum dot size. The degradation of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) dyes in an aqueous solution with different initial amount of catalysts was observed by UV spectrophotometry after measuring the decrease in the concentration. As a result, the $Bi_2WO_6-GO-TiO_2$ composite showed good decolorization activity with MB solution under visible light. The $Bi_2WO_6-GO-TiO_2$ composite is expected to become a new potential material for decolorization activity. Photocatalytic reactions with different photocatalysts were explained by the Langmuir-Hinshelwood model and a band theory.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.758-763
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• 2002

The various ultrasonic energies (28 kHz, 40 kHz, 70 kHz) were used to improve the magnetic properties of Ba-ferrite as the perpendicular magnetic recording materials. In the sheet formation process, the different orientation hars were used to orientate perpendicularly the dispersed Ba-ferrite to sheet. Throughout these experiments, we have obtained relatively higher value of S. Q. (Squreness Ratio : 0.783) and O. R. (Orientation Ratio : 2.87) magnetic properties at 2 h ultrasonic treatment of 40 kHz ultrasonic energy. With aid of SEM(Scanning Electron Microscopy) images, the obtained sheet with dispersed of Ba-ferrite could be used for perpendicular magnetic recording due to orientated to easy magnetization axis, c-axis. In addition, the value of S. Q. of sheet decreased with increasing applied magnetic field angle during measuring of S. Q. value with changing applied magnetic field angle by VSM (Vibrating Sample Magnetrometer). This result also induced the probability for prependicular magnetic recording.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.1
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• pp.6-13
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• 2010

In this study, Ga-doped ZnO (GZO) thin films have been fabricated on Eagle 2000 glass substrates at various substrate temperatures $100{\sim}400^{\circ}C$ and thin film thickness by RF magnetron sputtering in order to investigate the structural, electrical, and optical properties of the GZO thin films. It is observed that all the thin films exhibit c-axis orientation and a (002) diffraction peak only. The GZO thin films, which were deposited at $T=300^{\circ}C$ and 400 nm, shows the highest (002) orientation, and the full width at half maximum (FWHM) of the (002) diffraction peak is $0.4^{\circ}$. AFM analysis shows that the formation of relatively smooth thin films are obtained. The lowest resistivity ($8.01{\times}10^{-4}\;{\Omega}cm$) and the highest carrier concentration ($3.59{\times}10^{20}\;cm^{-3}$) are obtained in the GZO thin films deposited at $T=300^{\circ}C$ and 400 nm. The optical transmittance in the visible region is approximately 80 %, regardless of process conditions. The optical band-gap shows the slight blue-shift with increase in doping which can be explained by the Burstein-Moss effect.

• Journal of the Korean Vacuum Society
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• v.22 no.1
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• pp.1-6
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• 2013

In this paper, to develop linear source for evaporating $600{\times}1,200mm$ size of large area CIGS absorber layer, we simulated linear thermal source and obtained ${\pm}5%$ thickness uniformity with various nozzle sizes and regular nozzle distance. Flux density was confirmed linear source length. Using this linear source, we tested thickness uniformity of Copper, Indium single layer which was obtained Cu ${\pm}5%$ and In ${\pm}5%$ thickness uniformity. And then CIGS absorber layers were evaporated with In-line single-stage co-evaporation. Large area CIGS absorber layers were confirmed composition uniformity of $$Cu{\leq_-}5%$$, $$In{\leq_-}7%$$, $$Ga{\leq_-}4%$$, $$Se{\leq_-}3%$$ with 600 mm width by XRF. Uniform shape of CIGS absorber layers was confirmed by SEM. XRD showed peaks which indicate chalcopyrite structure of CIGS absorber layers. Thus, developed linear source is suitable for evaporating CIGS absorber layer.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.4
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• pp.728-734
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• 2001

The purpose of this study was to investigate the effects of Er:YAG laser on cutting of efficacy of enamel and dentin in primary and permanent teeth. We used the enamel and dentin specimens of human teeth which contain the physiologic saline and maintain the pulpal pressure in dentinal tubules. Each specimen was exposed to Er:YAG laser with non-contact mode under different treatment condition of irradiation energy, pulse repetition rate. We investigated the cutting efficacy of Er:YAG laser by Scanning Intensity Microscopy, and obtained following results. 1. Cutting volume of enamel and dentin in primary and permanent teeth were increased by increasing the irradiation energy, pulse repetition rate. 2. Cutting volume of primary teeth was larger than that of permanent teeth. 3. Cutting volume of dentin was larger than that of enamel in primary and permanent teeth. From these results, Er:YAG laser would be more effective in cutting dentin than enamel, and in cutting primary teeth than permanent teeth for clinical application.