• 한국세라믹학회지
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• 제37권8호
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• pp.745-750
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• 2000

YAG:Tb3+ as green phosphor were studied for the development of low voltage FED phosphor prepared by hydrothermal synthesis. We changed the concentration of luminescence center ion Tb3+ in hydrothermal reaction of which conditions were at 8M NH4OH as mineralizer, at 35$0^{\circ}C$ for 12hrs. As results, we could finally get the YAG:Tb3+ (Y3-xTbxAl5O12) powder of which particle size was about 0.2~1.0${\mu}{\textrm}{m}$. The excitation spectra and the green emitted spectra of YAG:Tb3+ phosphor powder were observed. When we doped 0.25 mol Tb to YAG, we could observe the maximum cathodoluminescence from YAG:Tb3+ phosphor and the chromaticity coordinate of the phosphor was shown x=0.35, y=0.56 in CIE1931 diagram.

• 한국세라믹학회지
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• 제37권8호
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• pp.739-744
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• 2000

YAG(Y3Al5O12) as host material of YAG:Tb3+ was studied via hydrothermal synthesis of metal hydroxides. We changed the kind of mineralizer, the concentrations and process conditions in hydrothermal synthesis. As a result, we found, acicular YAG powders were obtained by the use of KOH as a mineralizer, the concentration of KOH affected the shape and size of YAG powder. Fine grained YAG were perpared by the use of NH4OH as a mineralizer and the concentration of NH4OH affected crystal phases but did not affect particle size. We could finally get the spherical looking YAG powder at 8 M NH4OH and at 35$0^{\circ}C$ for 12h. The average particle size was about 0.2${\mu}{\textrm}{m}$.

• Korean Chemical Engineering Research
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• 제60권3호
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• pp.414-422
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• 2022

본 연구의 목적은 국내 대표적인 농경잔류물인, 볏짚과 보릿짚을 이용하여 헤미셀룰로오스 부분의 최대 가용화를 위한 산 촉매 열수 분별공정의 타당성을 조사한 것이다. 1.2-2.9 범위의 반응가혹도(CS; Combined reaction severity)에서 다양한 분별 조건들을 사용하여 초기 반응조건 기준을 설정했다. 볏짚의 경우, 160 ℃의 반응온도, 0.75%(w/v)의 H₂SO₄, 20분의 반응시간, 그리고 1:15의 고체/액체 비율을 가진 반응 조건에서 56.6%의 헤미셀룰로스 당 수율을 얻을 수 있었으며, 보릿짚의 경우, 150 ℃ 반응온도, 0.75%(w/v) H₂SO₄, 15분의 반응시간, 1:10의 고체/액체 비율에서 83.0%의 헤미셀룰로스 당 수율을 얻었다. 따라서, 볏짚과 비교하여 보릿짚의 경우 산촉매 열수분획을 효과적으로 수행할 수 있었다. 분별과정 후 남은 분획된 고형분은 볏짚과 보릿짚에서 각각 48.5%와 57.5%였다. 분별된 볏짚과 보릿짚의 XMG(Xylan+Mannan+Galactan) 함량은 17.3% 및 17.6%에서 6.0% 및 2.6%로 각각 감소하였으며, 이는 원료 짚 기준으로 각각 16.7% 및 8.5%에 해당한다. 또한, 보리 짚의 산촉매 열수분별 과정에서 과도한 분해로 인해 셀룰로오스 및 XMG의 5.6% 및 8.5%만 손실된 반면, 볏짚의 셀룰로오스 및 XMG 손실은 6.4% 및 26.6%이었다. 볏짚의 헤미셀룰로스 당은 산 촉매 열수 분별공정중, 다소 높은 반응가혹도로 인해 심하게 과분해된 것에 기인한다.

• 방사성폐기물학회지
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• 제5권2호
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• pp.145-154
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• 2007

벤토나이트 완충재의 열수거동 실험에서는 고준위폐기물처분장 완충재로 유력하게 고려되고 있는 국산 벤토나이트를 대상으로 열수특성을 규명하고, 또 그 결과를 바탕으로 KRS 처분환경에서 벤토나이트 완충재의 장기건전성을 평가하였다. 실험결과, 벤토나이트 완충재의 열수반응은 주 구성광물인 스멕타이트의 일라이트화를 통해 진행되었으며, 온도, $K^+$농도, pH는 이러한 일라이트화에 중요한 열수반응인자 역할을 하였다. KRS 처분환경에 대한 국산벤토나이트 완충재의 장기건전성을 분석한 결과, 정상상태에서는 벤토나이트 완충재가 오랜 기간 동안 방벽재기능을 유지하였지만, 보수적인 조건에서는 약 $5{\times}10^4$년이 경과했을 때 벤토나이트 완충재를 구성하는 스멕타이트의 50%이상이 일라이트로 전환되어 방벽재로서의 팽윤능력을 상실할 수 있음을 예상할 수 있었다.

• 한국재료학회지
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• 제30권2호
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• pp.81-86
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• 2020

MoO₃ metal oxide nanostructure was formed by hydrothermal synthesis, and a perovskite solar cell with an MoO₃ hole transfer layer was fabricated and evaluated. The characteristics of the MoO₃ thin film were analyzed according to the change of hydrothermal synthesis temperature in the range of 100 ℃ to 200 ℃ and mass ratio of AMT : nitric acid of 1 : 3 ~ 15 wt%. The influence on the photoelectric conversion efficiency of the solar cell was evaluated. Nanorod-shaped MoO₃ thin films were formed in the temperature range of 150 ℃ to 200 ℃, and the chemical bonding and crystal structure of the thin films were analyzed. As the amount of nitric acid added increased, the thickness of the thin film decreased. As the thickness of the hole transfer layer decreased, the photoelectric conversion efficiency of the perovskite solar cell improved. The maximum photoelectric conversion efficiency of the perovskite solar cell having an MoO₃ thin film was 4.69 % when the conditions of hydrothermal synthesis were 150 ℃ and mass ratio of AMT : nitric acid of 1 : 12 wt%.

• 방사성폐기물학회지
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• 제8권3호
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• pp.173-179
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• 2010

고준위폐기물처분장에서 완충재는 오랜 기간 동안 방사성핵종의 붕괴열과 여러가지 화학조건의 지하수에 노출되며, 이러한 열수조건은 완충재물질의 차수 및 핵종저지 방벽성능에 심각한 영향을 줄 수 있다. 본 연구에서는 국산 스멕타이트를 대상으로 열수실험을 수행하고, 열수반응에 의한 스멕타이트 점토의 팽창도, 층전하, 양이온교환능의 변화를 조사하였다. 열수실험 결과, 온도와 용액 중 칼륨농도를 증가시켰을 때, 스멕타이트의 팽창도는 감소하였고, 층전하는 더 큰 음전하를 가졌으며, 양이온교환능도 감소하였다.

• 한국환경과학회지
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• 제22권7호
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• pp.837-845
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• 2013

This study was designed to synthesize mesoporous carbon, porous carbonic material and to characterize its surface in an attempt to adsorption methane gas($CH_4$). Synthesis of mesoporous carbon was carried out under two steps ; 1. forming a RF-silica complex with a mold using CTMABr, a surfactant, and TEOS, raw material of silica, and 2. eliminating silica through carbonization and HF treatment. The mesoporous carbon was synthesized under various conditions of synthesis time and calcination. Eight different types of mesoporous carbon, which were designated as MC1, MC2, MC3, MC4, MCT1, MCT2, MCT3, and MCT4, were prepared depending upon preparation conditions. The analysis of mesoporous carbon characteristics showed that the calcination of silica stabilized the mixed structure of silica and carbonic complex, and made the particle uniform. The results also showed that hydrothermal synthesis time did not have a strong influence on the size of pore. The bigger specific surface area was obtained as the hydrothermal synthesis time was extended. However, the specific surface area was getting smaller again after a certain period of time. In adsorption experiments, $CH_4$ was used as adsorbate. For the case of $CH_4$, MCT3 showed the highest adsorption efficiency.

• 한국결정성장학회지
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• 제4권1호
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• pp.100-104
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• 1994

KTP 종자결정의 육성을 수열법에 의해 행하였으며, 육성결정의 물성은 적외분광 광도계를 이용하여 조사하였다.종자결정의 육성에 있어 큰 성장속도를 나타내는 수열 조건은 다음과 같다. 즉, 온도범위,$430~450^{\circ}C $ ; 수열용매, 4몰 KF용액 ; 온도차, $30<{\triangle}T<65^{\circ}C$ ; 충진율%, 65% ; 육성방법, 수직온도 구배법. 이와 같은조건하에서 얻어진 KTP단 결정의 형태는(100), (011), (201)면이 잘 발달하는 경향이 있었으며 그리고 육성결정 중에는hydroxyl group이 존재하였다.

• 한국분말재료학회지
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• 제11권3호
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• pp.217-223
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• 2004

Submicron nickel powders were prepared from aqueous solution under hydrothermal condition. The experimental conditions including the types of protective agents, concentration of the solution and the pH were studied in detail. Starting concentration of nickel ion is a dominant factor affecting particle size. It was shown that the subsequent addition of Poly Vinyl Pyrrolidone(PVP) and Sodium Dodecyle Sulfate(SDS) can help to disperse the nickel powder. X-ray diffraction and SEM were employed to characterize the products.

• 한국지열·수열에너지학회논문집
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• 제3권1호
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• pp.1-9
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• 2007

A steady-state simulation model for Dual-Source Heat Pump(DSHP) of 8RT was presented. A Dual-Source Heat Pump(DSHP) has been designed to make up for the conventional air source heat pumps. The performance evaluation has been conducted under internal standard test conditions such as ISO-13256-1 and KS C 9306. However, as test conditions such as entering water, indoor and outdoor air conditions could not be controlled to satisfy the standard test conditions in outdoor tests, a series of experiments have been conducted with the actual test conditions. Then, computer models for DSHP could be used for the standard condition have developed using EES program. The model was developed from basic thermodynamic principles and heat transfer relations. Most of the parameters were obtained with EES from the actual catalog data. The simulation results were in good agreement with the experiments.