• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.753-758
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• 2018

We investigated annealing effects of seed layers on the properties of ZnO nanorods grown on the seed layers. ZnO nanorods were grown by a hydrothermal method. ~100 nm-thick ZnO films were sputtered on oxidized Si wafers and quartz as seed layers. The ZnO films were annealed at $400^{\circ}C$, $600^{\circ}C$, and $800^{\circ}C$, respectively. ZnO nanorods were grown at $90^{\circ}C$ for 3 hours in the mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine. X-ray diffraction was carried out to estimate the crystallinity and strain of ZnO films and nanorods. A field emission scanning electron microscope was employed to observe the morphology of the films and nanorods. PL(photoluminescence) measurements were conducted with 266 nm light. It was found that the annealing of seed layers increase the growth rate of nanorods, and change compressive strain of nanorods to tensile strain. The intensity of PL in the UV region reduced by using the annealed seed layers.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.173-180
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• 2004

Nano sized ZnO particle as 20-30nm applies for material, pigments, rubber additives, gas sensors, varistors, fluorescent substance as well as new material such as photo-catalyst, sensitizer, fluorescent material. ZnO with a particle size in the range 20-30nm has provided to be an excellent UV blocking material in the cosmetics industry, which can be used in sunscreen product to enhance the sun protection factor and natural makeup effect. But pure ZnO particles application limits for getting worse wearing feeling. We make high-functional inorganic-composite that coated with nano-ZnO on the plate-type particle such as sericite, boron nitride and bismuthoxychloride. In this experiment, we synthesized composite powder using hydrothermal precipitation method. The starting material was ZnCl$_2$ Precipitation materials were used hexamethylenetetramine(HMT) and urea. We make an experiment with changing as synthesis factors that are concentrations of starting material, precipitation materials, nuclear formation material, reaction time, and reaction temperature. We analyzed composite powder's shape, crystallization and UV-blocking ability with FE-SEM, XRD, FT-IR, TGA-DTA, In vitro SPF test. The user test was conducted by product's formulator. In the results of this study, nanometer sized ZnD was coated regardless of the type of plate-powder at fixed condition range. When the coated plate-powders were applied in pressed powder product, the glaze of powder itself decreased, but natural make-up effect, spreadability, and adhesionability were increased.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.49-56
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• 1999

A material was formulated with Phenol novolac and HEXA only. The cure kinetics and thermal characteristics of phenol novolac with various HEXA contents were peformed by differential scanning calorimetry and thermal gravimetric analysis. All kinetic parameters of the curing reaction including the reaction order, activation energy, and rate constant were calculated and reported. The results indicate that the curing reaction goes through an autocatalytic kinetic mechanism. The friction and wear characteristics of this material were determined using friction material testing machine. The friction coefficient of phenol novolac with various HEXA contents was determined using the PV(pressure & velocity) factor. The most stable and highest friction coefficient with a various pressure and velocity condition was found at HEXA 10 wt.% material. The specific wear rate per unit sliding distance with a various HEXA contents was reported.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.317-317
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• 2010

ZnO나노와이어는 높은 투과도, 화학 및 열적 안정성을 가지며, 유기태양전지에 적용하였을 때 Active Layer의 표면적 증가, 전자의 수집 및 전달에 용이한 장점가지고 있어 하이브리드 유기 태양전지에 적용되고 있다. ZnO나노와이어와 P3HT/PCBM을 사용한 하이브리드 유기태양전지는 Active Layer의 열처리 온도를 변화시켜 ITO/AZO/ZnO wire/PCBM:P3HT/PEDOT:PSS/Ag구조로 제작되었다. ZnO나노와이어는 AZO를 Seed로 사용하고 Znc nitrate hydrate와 hexamethylenetetramine을 혼합하여 수열합성법으로 성장 후, P3HT:PCBM, PEDOT:PSS을 Spin Coating법으로 형성하였다. UV-vis와 Solar simulator를 통하여 Active Layer의 열처리 온도에 따른 태양전지의 특성을 분석하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.253.1-253.1
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• 2013

RF 마그네트론 스퍼터링법으로 증착된 Al-doped ZnO 박막을 씨드층으로 하고, zinc nitrate hexahydrate, hexamethylenetetramine (HMTA), ammonium chloride (AC) 및 polyethyleneimine (PEI)를 반응용액으로 한 수열합성법으로 ZnO 나노와이어를 성장시켰다. ZnO 나노와이어의 성장 공정 중 반응 용액내에 DC 바이어스를 인가하고, DC 바이어스의 인가 유무 및 인가 DC 바이어스 전압의 크기 변화에 따라 성장시킨 ZnO 나노와이어의 특성을 비교분석하였다. 다양한 공정변수 변화에 따라 수열합성법으로 성장시킨 ZnO 나노와이어 시편들을 SEM 분석을 통해 특성분석을 수행하였다.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.292-295
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• 2005

The curing time of the phenolic resin for the processing of brake pad is very important factor for reducing the processing cost. The curing time could be investigated by examining the reaction time of the phenolic resin and hexamethylenediamine. The reaction time has been studied by FT-IR, Differential Scanning Calolimetric Analysis (DSC), and Thermogravimetric Analysis (TGA).

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.211-216
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• 2011

In this study, the effects of growth temperature on structural and optical properties of hydrothermally grown ZnO nanorod arrays have been investigated. Zinc nitrate ($Zn(NO_3)_2$) and hexamethylenetetramine were used as precursors. The ZnO buffered Si(100) with a thickness of 40 nm was used as the substrates. The ZnO nanorods were grown on these substrates with the temperature ranging from 55 to $115^{\circ}C$. The results were characterized by scanning electron microscope, X-ray diffraction and room temperature photoluminescence measurements. Well-aligned ZnO nanorods arrays were obtained from all samples. The tips of nanorods were flat when the temperature was less than $95^{\circ}C$, and the sharp-tip nanoneedle-like morphologies were obtained with the temperature of $115^{\circ}C$. In addition, some bundles were on the nanorods arrays with $115^{\circ}C$ due to the non-equilibrium growth. The growth temperature could affect the crystal and optical properties of ZnO. For the effects on crystal properties, the intensity of (002) peak was increased as the temperature was increased to $75^{\circ}C$, then decreased as the temperature was further increased to $115^{\circ}C$. As for the effects on optical properties, the intensity ratio of UV peak to visible peak is increased with the temperature increasing and the strongest UV peak intensity was obtained with the growth temperature of $95^{\circ}C$.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.106-109
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• 2012

A low power methane gas sensor with microheater was fabricated by silicon bulk micromachining technology. In order to heat up the sensing layer to operating temperature, a platinum (Pt) micro heater was embedded in the gas sensor. The line width and gap of the microheater was 20 ${\mu}m$ and 4.5 ${\mu}m$, respectively. Zinc oxide (ZnO) nanowhisker arrays were grown on a sensor from a ZnO seed layer using a hydrothermal method. A 200 ml aqueous solution of 0.1 mol zinc nitrate hexahydrate, 0.1 mol hexamethylenetetramine, and 0.02 mol polyethylenimine was used for growing ZnO nanowhiskers. Temperature distribution of the sensor was analyzed by infrared thermal camera. The optimum temperature for highest sensitivity was found to be $250^{\circ}C$ although relatively high (64%) sensitivity was obtained even at as low a temperature as $150^{\circ}C$. The power consumption was 72 mW at $250^{\circ}C$, and only 25 mW at $150^{\circ}C$.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.846-851
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• 1998

An experimental research on the preparation of zinc oxide fine particles in w/o emulsions was conducted. Precipitation solutions were zinc nitrate aqueous solutions with hexamethylenetetramine(HMTA) as precipitant. The precipitation solutions formed stable w/o emulsions with kerosine in the presence of Span 80. Homogeneous precipitation reaction occurred in the w/o emulsion after the resultant w/o emulsion was heated above the decomposition temperature of HMTA and zinc oxide particles were precipitated. In some case, zinc oxide particles of bi-modal distribution were obtained. However, zinc oxide fine particles of narrow particle size distribution could be obtained, even when the initial zinc concentration of precipitation solution and the conversion to zinc oxide are both higher that those in bulk homogeneous precipitation.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.171.2-171.2
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• 2015

Nowadays, trivalent rare-earth ($RE^{3+}$) ions activated metal oxides have been proved to be excellent host materials due to their various applications. Facile wet-chemical technique have been considered as the best synthetic route due its intensive interest in the preparation of nanostructures. Europium ion doped lanthanum hydroxide ($La(OH)_3:Eu^{3+}$) phosphors were synthesized by the facile wet chemical method using the hexamethylenetetramine (HMTA) as a mediated surfactant. The thermal behavior for the $La(OH)_3:Eu^{3+}$ phosphors was investigated by thermogravimetric and differential thermal analysis method. The morphological studies were measured by scanning electron microscope and transmission electron microscope measurements, indicating three-dimensional (3D) flower-like $La(OH)_3:Eu^{3+}$ nanorod bundles. After subsequent annealing process, the lanthanum oxide ($La_2O_3:Eu^{3+}$) phosphor exhibited similar kind of morphology. The synthesized $La(OH)_3:Eu^{3+}$ and $La_2O_3:Eu^{3+}$ samples were characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. Furthermore, photoluminescence and cathodoluminescence properties were studied in details.