• 한국재료학회지
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• 제30권8호
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• pp.383-392
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• 2020

In this paper, AgCl/Ag₃PO₄/diatomite photocatalyst is successfully synthesized by microemulsion method and anion in situ substitution method. X-ray diffraction (XRD), photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) are used to study the structural and physicochemical characteristics of the AgCl/Ag₃PO₄/diatomite composite. Using rhodamine B (RhB) as a simulated pollutant, the photocatalytic activity and stability of the AgCl/Ag₃PO₄/diatomite composite under visible light are evaluated. In the AgCl/Ag₃PO₄/diatomite visible light system, RhB is nearly 100 % degraded within 15 minutes. And, after five cycles of operation, the photocatalytic activity of AgCl/Ag₃PO₄/diatomite remains at 95 % of the original level, much higher than that of pure Ag₃PO₄ (40 %). In addition, the mechanism of enhanced catalytic performance is discussed. The high photocatalytic performance of AgCl/Ag₃PO₄/diatomite composites can be attributed to the synergistic effect of Ag₃PO₄, diatomite and AgCl nanoparticles. Free radical trapping experiments are used to show that holes and oxygen are the main active species. This material can quickly react with dye molecules adsorbed on the surface of diatomite to degrade RhB dye to CO₂ and H₂O. Even more remarkably, AgCl/Ag₃PO₄/diatomite can maintain above 95 % photo-degradation activity after five cycles.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2015년도 추계학술논문요약집
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• pp.465-466
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• 2015

In this study, different amount of (fe(0)) were dissolve into different strength of phosphoric ($H_3PO_4$) acid and the optimum solubility was observed at 0.89M Fe(0) into 4M of $H_3PO_4$ acid. Different concentration of oxalic acid was added to determine the optimum precipitated condition. The dissolution kinetics of Fe(0) into $H_3PO_4$ acid was investigated at $40-50^{\circ}C$. The optimum Fe-oxalate precipitate was dried and thermal decomposition using DSC-TG was conducted. Approximately 52 wt(%) of oxalic acid was removed at $300^{\circ}C$. Iron oxides such as magnetite and hematite that may be formed on the surface of nuclear waste were also dissolved into the $H_3PO_4$ acid and the optimum solubility for magnetite is 0.005M while that for hematite is 0.02M in 8M $H_3PO_4$ acid, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.248-248
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• 2010

리튬이온 2차전지의 대체 양극 후보 물질인 $LiFePO_4$를 합성하기 위하여 출발원료로 $Li_2CO_3$, $Fe_2O_3$, $NH_4H_2PO_4$를 사용하여 볼밀 방법으로 혼합 분쇄한 후 열처리를 실시하였다. 합성 시에 3가 Fe를 2가로 환원시키기 위하여 $C_{12}H_{22}O_{11}$(흑설탕)을 출발원료와 함께 5 ~ 12 wt%로 나눠서 첨가하였다. 합성 후 XRD로 결정구조의 양질성을 확인하였고. FE-SEM으로 나노미터 크기의 구형 입자를 관찰하였다. XRF를 이용하여 3 ~ 10 wt%의 탄소 잔량을 확인하였다. 전기화학적 특성을 충 방전시험기로 평가한 결과, 8wt%의 탄소원을 첨가한 $LiFePO_4$에서 가장 좋은 수명 특성을 얻었고, 최대 145 mAh/g의 방전용량을 얻었다.

• 한국표면공학회지
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• 제52권5호
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• pp.265-274
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• 2019

Formation behavior of PEO (Plasma Electrolytic Oxidation) films on AZ31 Mg alloy was investigated under application of 310 Hz AC as a function of $Na_3PO_4$ concentration from 0.02 M to 0.2 M. Film formation voltage and in-situ observation of arcs generated on the specimen surface were recorded with time, and surface morphologies of the PEO films were investigated using optical microscopy, confocal scanning laser microscopy and scanning electron microscopy. PEO film formation voltage decreased linearly with increasing $Na_3PO_4$ concentration which is attributed to the increase of solution pH. PEO films were grown uniformly over the entire surface in $Na_3PO_4$ solutions between 0.05 M and 0.1 M. However, non-uniform PEO films with white spots were formed in $Na_3PO_4$ solutions containing more than 0.1 M. Thickness and roughness of PEO films on AZ31 Mg alloy increased linearly with increasing $Na_3PO_4$ concentration and their increasing rates appeared to be much higher under 1 M than above 1 M. The experimental results suggest that phosphate ions can contribute to the formation of PEO films but higher $Na_3PO_4$ concentration more than 1 M results in local damages of PEO films due to repeated generation of white arcs at the same surface site of AZ31 Mg alloy.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1495-1498
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• 2005

Due to an efficient red emission, $Eu^{+3}$ ions have doped in various host materials. Eu-doped $LaPO_4/LaPO_4$ core/shell nanophosphor which emits red light in visible range, was synthesized by using a solution system. The mean size of the nanoparticle observed by TEM was about 7-8 nm. In this core/shell system, the thickness of $LaPO_4$ shell was optimized on the basis of relative PL emission intensity. In addition, the luminescent properties of $LaPO_4:Eu/LaPO_4$ core/shell particle have been compared with Eu-doped $LaPO_4$ bulk particle and nanoparticle.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.303-303
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• 2008

$LiMn_2O_4$는 출력특성이 좋고 가격이 저렴하지만 전해액 중에서 $Mn^{2+}$이 용출되어 나오는 것과 반복적인 충방전시 구조가 파괴되는 단점이 있어 이것을 보완하고자 $FePO_4\cdot2H_2O$를 $LiMn_2O_4$의 표면에 코팅하였다, $LiMn_2O_4$를 모재로, $FePO_4\cdot2H_2O$를 코팅재로 사용하여 $FePO_4\cdot2H_2O$의 코팅량 변화와, 열처리 온도변화에 따른 물성 변화를살펴보았다, LiOH 와 $MnO_2$의 혼합물을 $1000^{\circ}C$ 에서 소성하여 $LiMn_2O_4$를 합성하고, Fe$(NO_3)_3$ 수용액과 $NH_4H_2PO_4$ 수용액을 혼합하여 $FePO_4\cdot2H_2O$를 제조하였다, $LiMn_2O_4$에 $FePO_4\cdot2H_2O$를 1wt%, 2wt%, 3wt% 비율로 ball milling 을 통해 코팅한 후, 온도를 변화시키면서 열처리 하였다. 코팅한 물질을 XRD를 통해 구조를 분석하고 SEM을 이용하여 형상을 관찰하였다. 또한 고온에서의 $Mn^{2+}$의 용출량을 ICP로 측정하고 half-cell을 만들어 충방전 test를 통해 충방전 특성을 조사하였다. 아울러, 코팅량과 열처리 온도 등 합성변수들이 소재특성 및 전기화학적 특성에 미치는 영향을 조사하였다.

• 전기화학회지
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• 제15권1호
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• pp.27-34
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• 2012

열처리 온도를 $600^{\circ}C$와 $800^{\circ}C$로 다르게 하여 비정질 및 결정질구조의 탄소를 포함하는 $Li_3V_2(PO_4)_3/C$분말을 각각 합성하였으며, 결정성에 따른 리튬 이차전지용 음극으로의 특성을 비교하였다. 결정질 $Li_3V_2(PO_4)_3/C$은 추가반응에 의하여 리튬이 저장되기 때문에 260 mAh $g^{-1}$의 제한된 용량만을 지니고 있음에 비하여, 비정질 $Li_3V_2(PO_4)_3/C$는 3가의 바나듐이 금속상태에 근접할 정도로 가역적으로 반응되어 460 mAh $g^{-1}$의 큰가역용량을 발현함을 확인하였다. 이는 비정질 구조에서 기인하는 특성으로 유연한 구조로 인한 새로운 리튬의 저장공간이 확보되는 것 때문이라 할 수 있다. 또한, 비정질 $Li_3V_2(PO_4)_3/C$는 비정질 구조에 기인하는 선형적인 충방전 곡선을 지니고 있어 정확한 충전심도의 예측이 용이할 뿐만 아니라, 결함구조에서 유발된 리튬이온의 향상된 확산성으로 인하여 우수한 속도 특성도 나타내고 있다.

• Membrane and Water Treatment
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• 제2권3호
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• pp.187-205
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• 2011

The electric transport of the mixture of hydrochloric and phosphoric acids through strong base (Neosepta ACM) and weak base (Selemion AAV) anion-exchange membranes was investigated. The instantaneous efficiency of HCl removal from the cathode solution, $CE_{Cl}$, with and without $H_3PO_4$ was determined. It was found that $CE_{Cl}$ was 0.8-0.9 if the number of moles of elementary charge passed through the system, $n_F$, did not exceed ca. 80% of the initial number of HCl moles in the cathode solution, $n_{Cl,ca,0}$. The retention efficiency of $H_3PO_4$ in that range was close to one. The transport of acid mixtures was satisfactorily described by a model based on the extended Nernst-Planck and Donnan equations for $n_F$ not exceeding $n_{Cl,ca,0}$. Among the tested model parameters, most important were: concentration of fixed charges, the porosity-tortuosity coefficient, and the partition coefficient of an undissociated form of $H_3PO_4$. For the both membranes, the obtained optimal values of fixed charge concentration, $\bar{c}_m$, were up to 40% lower than the literature values of $\bar{c}_m$ obtained from the equilibrium measurements. Regarding the $H_3PO_4$ equilibria, it was sufficient to consider $H_3PO_4$ as a monoprotic acid.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.921-926
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• 2011

This study investigates a root cause of the improved rate performance of $LiFePO_4$ after metal doping to Fesites. This is because the metal doped $LiFePO_4$/C maintains its initial capacity at higher C-rates than undoped one. Using $LiFePO_4$/C and doped $LiFe_{0.97}M_{0.03}PO_4$/C (M=$Al^{3+}$, $Cr^{3+}$, $Zr^{4+}$), which are synthesized by a mechanochemical process followed by one-step heat treatment, the Li content before and after chemical delithiation in the $LiFePO_4$/C and the binding energy are compared using atomic absorption spectroscopy (AAS) and X-ray photoelectron spectroscopy (XPS). The results from AAS and XPS indicate that the low Li content of the metal doped $LiFePO_4$/C after chemical delithiation is attributed to the low binding energy induced by weak Li-O interactions. The improved capacity retention of the doped $LiFePO_4$/C at high discharge rates is, therefore, achieved by relatively low binding energy between Li and O ions, which leads to fast Li diffusivity.

• 멤브레인
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• 제26권2호
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• pp.108-115
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• 2016

비료를 유도용액으로 사용하는 정삼투를 하수처리수(2차 침전지 유출수)의 재이용에 적용하여 유도용액의 성능을 평가하였다. 일반적으로 많이 사용되고 있는 비료 중에서 삼투압, 용해도 및 pH 등을 고려하여 $NH_4H_2PO_4$, KCl, $KNO_3$, $NH_4Cl$, $(NH_4)_2HPO_4$, $NH_4NO_3$, $NH_4HCO_3$ 및 $KHCO_3$을 유도용액 후보군으로 선정하고, 수투과선속 및 역용질선속을 측정하여 유도용액의 성능을 평가하였다. 평균 수투과선속은 KCl > $NH_4Cl$ > $NH_4NO_3$ > $KNO_3$ > $KHCO_3$ > $NH_4HCO_3$ > $NH_4H_2PO_4$ > $(NH_4)_2HPO_4$의 순서로 나타났으며, KCl을 유도용액으로 사용하였을 때, 평균 수투과선속은 13.49 LMH이었다. 하수처리장 2차 침전지 유출수의 삼투압은 탈이온수의 삼투압에 비해 큰 차이가 없었다. 역용질선속은 $NH_4H_2PO_4$ < $NH_4Cl$ < $(NH_4)_2HPO_4$ < $KNO_3$ < $NH_4HCO_3$ < $NH_4NO_3$의 순서로 나타났으며, $NH_4H_2PO_4$를 유도용액으로 사용하였을 때, 역용질선속은 $4.96{\times}10^{-3}mmol/m^2{\cdot}sec$이었다.