• Journal of the Society of Cosmetic Scientists of Korea
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• v.29 no.1
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• pp.169-184
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• 2003

비타민 C(L-ascorbic acid)는 강한 항산화성, 피부에 대한 높은 안전성으로 인해 피부의 노화방지, 미백, 주름 개선 등의 기능성 화장품 원료로써 많은 관심이 있는 물질이지만, 화학적으로 매우 불안정하여 쉽게 산화, 분해되므로 화장품 제형으로 포함시키는데 곤란한 문제가 있다. 본 연구에서는 비타민 C 의 안정성에 대한 단점을 보완하기 위하여 생체 및 피부 친화성이 우수한 무기물을 사용하여 비타민 C 를 캡슐화(encapsulation)한 분말상의 유-무기 복합물질 Vitabrid-C 를 합성하고, 이를 함유하는 피부 미백용 트윈케익 파우더를 개발하였다. 우선 Vitabrid-C 는 수용액상에서 비타민 C 를 수화된 산화아연(ZnO)으로 1 차 캡슐화하여 나노입자를 형성시키고, 그 표면을 실리카(silica)나노 입자로 한번 더 코팅하여 표면의 껍질이 다공특성을 갖는 분말을 제조함으로써 완성하였다. 이렇게 제조된 Vitabrid-C는 순수 비타민 C 에 비해 우수한 안정성을 보였으며, 캡슐 내 비타민 C 가 서서히 방출되는 서방특성을 발휘하였다. 또한 Vitabrid-C는 입자의 크기가 미세하고 균일하여 트윈케익 처방에 용이하게 적용할 수 있었다. Vitabrid-C와 순수 비타민 C의 생화학적 동등성에 대한 평가는 tyrosinase 억제능(L-DOPA oxidase 억제) 및 DPPH항산화 실험을 통하여 비교하였다. 트윈 케익 처방에 적용된 Vitabrid-C 에서 비타민 C 의 피부 투과경향을 Franz diffusion cell 법을 이용하여 확인하였다 또한 Vitabrid-C가 포함된 트윈케익을 건강한 피부를 가진 25 세 이상되는 여성의 전박에 색소 침착을 유도한 후 피부색 개선 효과 평가를 통해 임상적 효능을 평가하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.222-224
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• 2006

A non-vacuum process for $Cu(In,Ga)Se_2$ (CIGS) thin film solar cells from nanoparticle precursors was described in this work CIGS nanoparticle precursors was prepared by a low temperature colloidal route by reacting the starting materials $(CuI,\;InI_3,\;GaI_3\;and\;Na_2Se)$ in organic solvents, by which fine CIGS nanoparticles of about 20nm in diameter were obtained. The nanoparticle precursors were mixed with organic binder material for the rheology of the mixture to be adjusted for the doctor blade method. After depositing the mixture of CIGS with binder on Mo/glass substrate, the samples were preheated on the hot plate in air to evaporate remaining solvents ud to burn the organic binder material. Subsequently, the resultant (porous) CIGS/Mo/glass simple was selenized in a two-zone Rapid Thermal Process (RTP) furnace in order to get a solar ceil applicable dense CIGS absorber layer. Complete solar cell structure was obtained by depositing. The other layers including CdS buffer layer, ZnO window layer and Al electrodes by conventional methods. The resultant solar cell showed a conversion efficiency of 0.5%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.6
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• pp.220-225
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• 2020

Gallium oxide nano-powder, the key starting material for IGZO target, is fabricated by gas phase synthesis using a new apparatus consist of reaction, transportation, and collection parts. As a result of gallium metal evaporation above 1150℃, Ga2O3 nano-powders, are successfully synthesized. The SEM images of the synthesized powders displace the spherical shaped powders without severe agglomeration. X-ray diffraction and PSA analysis show that the higher temperature at the reaction part results in the better crystallinity and larger powder size of the synthesized Ga2O3. To see the applicability to IGZO target, Ga2O3 nano-powders synthesized at 1250℃ are mixed with indium oxide and zinc oxide (In2O3 : Ga2O3 : ZnO = 1 : 1 : 1), and then sintered at 1400~1500℃. The highest sintered density of 5.83 g/㎤ (= 91 % of relative density) is achieved when sintered at 1450℃, showing better sinterability compared to the commercially available Ga2O3 powder, which has 5.61 g/㎤ of sintered density at the same condition.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.742-748
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• 2004

Isopropanol of low boiling point was used as a solvent to prepare Al-doped ZnO(AZO) thin films. A homogeneous and stable sol was made from Zn acetate a solute whose mole concentration was 0.7mol/$\iota$ and Al chloride as a dopant. Al-doped ZnO thin films were prepared by sol-gel method as a function of post-heating temperature from 500 to $700^{\circ}C$ and the optical and electrical properties were investigated. The c-axis orientation along (002) plane was enhanced with the increasing of post-heating temperature and the surface morphology of the films showed a homogeneous and nano-sized microstructure. The optical transmittance of the films post-heated below $650^{\circ}C$ was over $86\%$, but decreased at $700^{\circ}C$. The electrical resistivity of the thin films decreased from 73 to 22 $\Omega$-cm as the post-heating temperature increased up to $650^{\circ}C$, but increased greatly to 580 $\Omega$-cm at $700^{\circ}C$. XPS analysis indicated that the deterioration of electrical and optical properties was attributed to the precipitation of $Al_2O_3$ phase on the surface of AZO thin film. This result suggests that the optimum post-heating temperature to improve electrical and optical properties is $600^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.23-23
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• 2009

CIGS 박막 태양전지는 제조단가가 낮고 박막 태양전지 중에서 변환효율이 가장 높아 발전 가능성이 큰 태양전지로 인식되고 있다. 이미 일본, 독일, 미국을 비롯한 선진국에서는 30-50 MW 급의 양산 라인이 구축되고 있어 2010년 이후에는 본격적인 상용화가 진행될 것으로 보인다. CIGS 광흡수층은 진공증발, 셀렌화, 나노입자, 전기도금등 다양한 방식으로 제조가 가능한데 이 중에서도 동시진공증발공정은 고효율 CIGS 박막 태양전지 제조에 적합하다. 본 연구에서는 동시진공증발법을 이용하여 CIGS 박막을 증착하였으며 소다회유리/Mo/CIGS/CdS/i-ZnO/n-ZnO/Al/AR 구조의 태양전지를 제조하였다. 기판온도 모니터링을 통한 Cu 이차상 조절 기술을 이용하여 결정립이 매우 큰 CIGS 박막을 증착하였으며 Ga/(In+Ga) 조성비의 조절을 통하여 밴드갭 에너지를 최적화하였다. 또한 QCM 장치를 활용하여 용액 속에서 성장되는 CdS 박막의 두께와 특성을 조절하였다. 이러한 공정최적화를 통하여 개방전압 0.65 V, 단락전류밀도 38.8 $mA/cm^2$, 충실도 0.74 그리고 변환효율 18.8% 의 CIGS 박막 태양전지를 얻었다.

• Particle and aerosol research
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• v.12 no.2
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• pp.37-42
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• 2016

$CeO_2$ nanoparticles were prepared by a flame spray pyrolysis from aqueous solution of cerium nitrate. The morphology, structure crystallinity and specific surface area of as-prepared nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Telle (BET). The $CeO_2$ nanoparticles about 5 nm in diameter showed a cubic fluorite structure and polyhedral morphology. The average particle size increased as the cerium nitrate concentration increased. UV absorption performance of the as-prepared nanoparticles was measured by UV-visible spectroscopy. UV absorption of $CeO_2$ nanoparticles was more effective than that of commercial $TiO_2$ nanoparticles. Effect of dopants such as Ti and Zn to $CeO_2$ nanoparticles on UV absorption properties was also investigated. In case of $Ti/CeO_2$, and $Zn/CeO_2$ nanoparticles, they showed a little higher UV absorption values compared with $CeO_2$ nanoparticles. The as-prepared nanoparticles can be promising materials with high UV absorption value.

• Korean Journal of Environmental Biology
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• v.39 no.4
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• pp.550-558
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• 2021

In a radiotracer study, the bioaccumulation and efflux of metals in earthworms (Eisenia fetida) exposed to soil spiked with ZnO and Ag nanoparticles (AgNP) were compared to those exposed to soil spiked with ionic Zn and Ag. Additionally, the bioavailability and chemical mobility of nano- and ionic metals in the soil were estimated using the sequential extraction method and compared to the bioaccumulation factor(BAF). The BAF for ZnO (0.06) was 31 times lower than that for Zn ions (1.86), suggesting that ZnO was less bioavailable than the ionic form in contaminated soil. In contrast, the BAFs for two types of AgNPs coated with polyvinylpyrrolidone (0.12) or citrate (0.11) were comparable to those of ionic Ag (0.17). The sequential extraction of metals from the soil suggests that the chemically mobile fractions in the Zn ion treatment were higher(35%) than those (<20%) in the Ag ion treatment, which was consistent with the greater BAFs in the former than the latter. However, the chemical mobility in the ZnO treatments did not predict bioavailability. The efflux rates of Ag (3.2-3.8% d^-1) in the worms were 2-3×those(1.2-1.7% d^-1) for Zn.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.386-386
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• 2011

sol-gel 및 hydrothermal growth method를 이용한 zinc oxide nanorod는 제작 시 고가의 장비가 필요치 않기에 저비용 대면적 박막을 제작하는데 적합하지만 rod들의 array 및 density 조절에서 어려움을 가지고 있다. 본 연구에서는 이러한 nanorod array 형상 조절을 위하여 zinc oxide seed layer 형성 과정 중 precursor solution에 이종 나노 입자를 첨가하였다. 첨가한 seed precursor solution을 spin coating한 이후에 후처리 하여 hydrothermal method를 이용해 성장시켰다. 합성한 rod들을 optic과 FE-SEM으로 측정해 rod들의 density 변화를 확인할 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.9 s.240
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• pp.1065-1073
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• 2005

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina $(Al_2O_3)$, zinc oxide (ZnO) and titanium dioxide $(TiO_2)$ nanoparticles is measured by varying the particle diameter and volume fraction. The transient hot-wire method using an anodized tantalum wire for electrical insulation is employed for the measurement. The experimental results show that nanofluids have substantially higher thermal conductivities than those of the base fluid and the ratio of thermal conductivity enhancement increases linearly with the volume fraction. It has been found that the ratio of thermal conductivity enhancement increases with decreasing particle size but no empirical or theoretical correlation can explain the particle-size dependence of the thermal conductivity. This work provides, for the first time to our knowledge, a set of consistent experimental data over a wide range of nanofluid conditions and can therefore serve as a basis for developing theoretical models to predict thermal conduction phenomena in nanofluids.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.120-125
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• 2008

In this study, NiCoZn ferrites with the variation of sintering temperature and chemical composition were prepared by the coprecipitation. Microstructures Crystal structure of NiCoZn ferrites were analyzed by XRD and their electric magnetic characteristics were analyzed by LCR meter and their morphology observed by SEM. We identified that these powders have a typical NiCoZn spinel structure and nanoparticles average size of 40 nm. The impurity, the initial permeability and the Q factor value are the lowest of sintered NiCoZn ferrite at $1250^{\circ}C$. Also, we measured S-parameter for $(Ni_{0.4}Co_{0.1}Zn_{0.5})Fe_2O_4$ which showed a maximum reflection loss of -3.1 dB at 6 GHz for the 2 mm thick sample. From this result, we found that the NiCoZn ferrite can be used in ferrite microwave-absorbing application at a higher frequency region (> 6 GHz).