• 한국응용과학기술학회지
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• 제28권3호
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• pp.335-344
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• 2011

The pearlesent pigment has received attention in a diversity of fields like cosmetics, inks, paints and so on. Ferric Ferrocyanide, one of the nano sized pearlescent pigment, is a kind of surface modification pigment that covers a metal oxidized substance or a coloring agent with uniform thickness. Characteristics of pearlescent pigment are various interference color, intense gloss effect and a three-dimensional effect. We synthesised the pearlesent pigment that ferric ferrocyanide can be deposited on the titania/mica surface by hydrothermal synthesis method. The process parameters are concentration of precursor, controlling pH and reaction temperature. The optimun conditions is that amount of iron(III) chloride hexahydrate is 3.1 wt% and amount of potassim ferrocynide trihydrate is 3.6 wt% in the started pH 4.5 at $70^{\circ}C$. The coating rate and coating efficiency of ferric ferrocyanide was about 1.47 % and 96.7 %, respectively. The synthesised pearlesent pigment was characterized by SEM, XRD, FT-IR and EDS.

• 한국표면공학회지
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• 제40권1호
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• pp.11-15
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• 2007

Stable metallic Cu/Zn nanoparticles were prepared in the base oil phase by hydrothermal method. The physical properties, such as crystal structure, crystallite size and crystallinity according to synthesis conditions have been investigated by XRD, FT-IR and TEM. In addition, 4-ball test has been performed in order to investigate the frictional wear properties of prepared nanosized Cu/Zn particles. The peaks of the X-ray diffraction pattern indicate that the particle size was very small and crystallinity of Cu/Zn particles was good. The micrographs of TEM showed that nanosized Cu/Zn particles possessed a spherical morphology with a narrow size distribution. The crystallite size of the Cu/Zn particles synthesized in base oils was 23-30 nm. It was found that the antiwear capacity increases with increasing Cu/Zn concentration. When the concentration of Cu/Zn was 5.0 wt%, the wear scar diameters was 0.38 mm.

• Bulletin of the Korean Chemical Society
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• 제25권9호
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• pp.1341-1345
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• 2004

We developed a novel synthesis strategy of titania nanowire arrays by employing simple hydrothermal reaction and ion-exchange reaction techniques. Hydrothermal reactions of metallic titanium powder with $H_2O_2$ in a 10 M NaOH solution produced a new sodium titanate compound, $Na_2Ti_6O_{13}{\cdot}xH_2O$ (x~4.2), as arrays of nanowires of lengths up to 1 mm. Acid-treatment followed by calcination of this material produced arrays of highly crystalline anatase nanowires as evidenced by x-ray diffraction, Raman spectroscopy, and transmission electron microscopy studies. In both cases of sodium titanate and anatase, the nanowires have exceptionally large aspect ratios of 10,000 or higher, and they form arrays over a large area of $1.5 {\times} 3 cm^2$. Observations on the reaction products with varied conditions indicate that the array formation requires simultaneously controlled formation and crystal growth rates of the $Na_2Ti_6O_{13}{\cdot}xH_2O$ phase.

• 에너지공학
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• 제13권3호
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• pp.228-233
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• 2004

본 논문은 다양한 종류의 유기성 폐기물을 이용하여 고온고압수 반응에 의해 생성되는 저분자 카르복시산의 거동에 관해 고찰하였으며 산화제 첨가에 대한 영향도 동시에 검토를 행하였다. 그 결과 acetic, formic, succinic 및 lactic acid와 같은 유기산이 주된 생성물임을 알 수 있었다. 생선내장의 경우 35$0^{\circ}C$(P=16 MPa)의 조건에서 acetic acid비 수율은 26mg/g-dry를 얻을 수 있었으며 산화제로서 $H_2O$$_2$를 첨가했을 경우 42mg/g-dry로 수율이 증가함을 알 수 있었다. 또한 글루코오스를 이용한 실험결과에서는 약 29mg/g-dry의 acetic acid를 얻을 수 있었다. 유기산 생성에 관한 온도 의존성을 검토한 결과, acetic acid는 열적 안정성이 있음을 알 수 있었으나 formic acid는 상대적으로 쉽게 분해하는 경향을 나타내었다. 또한 산화제를 첨가 할 경우, acetic acid와 같은 유기산의 생성을 촉진 시키는 결과를 얻을 수 있었다.

• 대한금속재료학회지
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• 제48권6호
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• pp.543-550
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• 2010

This paper investigated the synthesis conditions of nano-sized $TiO_2$ powder in a hydrothermal process at a temperature range of $100{\sim}180^{\circ}C$ considering the precipitation agent, precipitation pH, reaction temperature and time. Titanium hydroxide formed by $NH_4OH$ exhibited a lower crystallization temperature than that by NaOH and formed less aggregated $TiO_2$ particles. As the precipitation pH increased above 8, the shape of the particles changed from spherical to needle form, which appeared to be caused by dissolution and re-precipitation of the titanium hydroxide in an alkali environment.

• 한국전기전자재료학회논문지
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• 제36권4호
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• pp.376-384
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• 2023

Nitrogen-doped graphene was synthesized by a hydrothermal method using graphene oxide (GO) as the raw material, urea as the reducing agent and nitrogen as the dopant. The morphology, structure, composition and electrochemical properties of the samples are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption analysis, electrical conductivity and electrochemical tests. The results show that urea can effectively reduce GO and achieve nitrogen doping under the hydrothermal conditions. By adjusting the mass ratio of raw materials to dopants, the graphene with different nitrogen doping contents can be obtained; the nitrogen content range is from 5.28~6.08% (atomic fraction percentage).When the ratio of dopant to urea is 1:30, the nitrogen doping content reaches a maximum of 6.08%.The supercapacitor performance test shows that the nitrogen content prepared by the ratio of 6.08% is the best at 0.1 A·g^-1. The specific capacitance is 95.2 F·g^-1.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.63-67
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• 2024

In this study, we successfully synthesized copper oxide (Cu₂O) particles through a hydrothermal method at a relatively low temperature (150℃). The synthesis involved the precise control of molar concentrations of NaOH. Notably, Cu₂O particles were effectively synthesized when NaOH concentrations of 0.15 M and 0.20 M were utilized. While attempts were made at different molar concentrations, the synthesis of pure Cu₂O particles was only achieved at concentrations of 0.15 M and 0.20 M. In this experimental investigation, Cu₂O synthesized under these specific conditions exhibited absorption characteristics within the wavelength range of 640 to 570 nm, consistently exhibiting a band gap energy of 1.9 eV. These Cu₂O particles, characterized by their small band gap energy and straightforward synthetic method, hold significant promise for various applications including semiconductors and solar cells.

• 한국세라믹학회지
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• 제48권1호
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• pp.99-105
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• 2011

Lead titanate ($PbTiO_3$) powder was prepared from lead nitrate ($Pb(NO_3)_2$) and titania ($TiO_2$) by hydrothermal route. Phase formation process was investigated by observing the phases formed in various experimental conditions like different KOH concentration, reaction temperature and time. $PbTiO_3$ powder was fabricated when the KOH concentration was 0.8M or higher. An intermediate compound, $PbTi_{0.8}O_{2.6}$, was formed at first by a reaction between PbO and $TiO_2$ and changed into $PbTiO_3$ powder with a perovskite crystal structure. A $PbTiO_3$ phase was formed in a shorter time when a KOH concentration was increased from 0.8M to 8M because a driving force for a $PbTiO_3$ formation was increased due to an increase in a degree of supersaturation. And $TiO_2$ (rutile) and $3PbO{\cdot}H_2O$ were observed at room temperature in a 0.8M KOH solution and $TiO_2$(rutile) and PbO (litharge) in a 8M KOH. A $PbTiO_3$phase was also formed in a shorter time at a higher reaction temperature as a reaction temperature influenced the rates for a dissolution and a precipitation.

• 한국결정성장학회지
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• 제31권2호
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• pp.78-83
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• 2021

본 연구에서는 수열반응법을 이용하여 3차원 구조를 갖는 NiCo2O4 입자를 합성했다. 수열합성에서 반응조건 [Ni]/[Co] 비율, 반응시간과 열처리온도를 달리하여 입자의 조성과 형상을 조절했다. 최적의 조건을 결정하고자 XRD, SEM을 통해 입자를 분석하였으며, [Ni]/[Co] 1:2 비율, 반응시간 12시간, 열처리 400℃ 4시간 조건에서 3차원 구조를 갖는 단일상의 NiCo2O4가 합성하였다. 합성된 NiCo2O4 나노구조체의 글루코스 센서 특성평가 결과, 글루코스에 대해 높은 민감도와 탁월한 선택성을 나타냈다. 본 연구를 통해 합성한 NiCo2O4 나노구조체는 향후 비효소 기반 전기화학적 글루코스 센서로 널리 응용될 수 있을 것으로 기대된다.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.202.2-202
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• 2003