• Analytical Science and Technology
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• v.8 no.3
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• pp.305-311
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• 1995

The stability constant of the complex between salicylic acid($H_2A$) and Fe(III) ion has been determined using UV-Vis absorption spectrometry and pH titration method in O.1M $KNO_3$ aqueous solution at $20^{\circ}C$ and compared with reference value, $logK_f=16.48$. The $pK_{a1}$ and $pK_{a2}$ of $H_2A$ are $2.92{\pm}0.08$ and $12.90{\pm}0.13$, respectively and the $logK_f$ of 1:1 complex Fe(III)-$H_2A$ system is $11.88{\pm}0.12$ at $20^{\circ}C$.

• Korean Journal of Materials Research
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• v.19 no.4
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• pp.228-231
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• 2009

Phase transition in ferroelectric polymer is very interesting behavior and has been widely studied for real device applications, such as actuators and sensors. Through the phase transition, there is structural change resulting in the change of electrical and optical properties. In this study, we fabricated the Febry-Perot interferometer with the thin film of ferroelectric P(VDF-TrFE) 50/50 mol% copolymer, and thermo-optical properties were investigated. The effective thermo-optical coefficient of P(VDF-TrFE) was obtained as $2.3{\sim}3.8{\times}10^{-4}/K$ in the ferroelectric temperature region ($45^{\circ}C{\sim}65^{\circ}C$) and $6.0{\times}10^{-4}/K$ in the phase transition temperature region ($65^{\circ}C{\sim}85^{\circ}C$), which is a larger than optical silica-fiber and PMMA. The resonance transmission peak of P(VDF-TrFE) with the variation of temperature showed hysteretic variation and the phase transition temperature of the polymer in heating condition was higher than in the cooling condition. The elimination of the hysteretic phase transition of P(VDF-TrFE) is necessary for practical applications of optical devices.

• Journal of IKEEE
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• v.25 no.2
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• pp.322-329
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• 2021

In this study, a method for improving the light extraction efficiency of organic light emitting diodes was presented using the polymer Poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] having an island surface structure after annealing. Polydimethylsiloxane (PDMS) imprinted on the island-structured P(VDF-TrFE) surface has a spike structure, which improves the external light extraction efficiency aroud 20%. It was confirmed that the produced film showed a low haze characteristic of 8.2, and the Current and external quantum efficiency could be improved without pixel blur due to the excellent transmittance of 93.4%.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.529-539
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• 2019

In this study, heavy metal removal and precipitation characteristics with pH change were studied for artificial acid mine drainage. Artificial acid mine drainage was prepared using sulfates of iron, aluminum, copper, zinc, manganese which contained in acid mine drainage from abandoned mines. The single and mixed five heavy metal samples of Fe, Al, Cu, Zn, and Mn were prepared at initial concentrations of 30 and 70 mg/L. Fe and Al were mostly removed at pH 4.0 and 5.0, respectively, and other heavy metals gradually decreased with increasing pH. Concentration changes with increasing pH show generally similar trend for single and mixed heavy metal samples. The effect of removing heavy metals from aqueous solutions is not related to the initial concentration and depends on the pH change. XRD were used for mineral identification of precipitates and crystallinity of the mineral tended to increase with increasing pH. The precipitates that produced by decreasing the concentration of heavy metals in the aqueous solution composed of Fe-goethite(FeOOH), Al-basaluminite(Al₄(SO₄)(OH)₁₀·4H₂O), Cu-connellite(Cu₁₉(OH)₃₂(SO₄)Cl₄·3H₂O) and tenorite(CuO), Zn-zincite(ZnO), and Mn-hausmannite(Mn₃O₄).

• Proceedings of the Korean Magnestics Society Conference
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• 1998.05a
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• pp.124-124
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• 1998

• 한국전기화학회:학술대회논문집
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• 2004.04a
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• pp.32-32
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• 2004

• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.267-275
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• 2007

Melting slag generated from municipal-incinerator ash contains lots of impurities which have adverse effects on zeolite synthesis. These impurities are detrimental to zeolite synthesis, and the yield and purity of zeolite was decreased. And thus its performance is lowered. In melting slag, there are lots of components such as $Fe_2O_3$, FeO and CaO. To remove these impurities, we treated the melting slag with hydrochloric acid at initial pH 1, 3, 5, and 7. After the treatment, the $SiO_2,\;Fe_2O_3,\;and\;TiO_2$ ratios increased, but the $Al_2O_3,\;FeO,\;CaO,\;Na_2O$ and MgO ratios decreased. We reacted these treated slag in a NaOH solution under hydrothermal conditions at $80^{\circ}C$. The hydrothermal products from the slag and the slag treated at pH 7 and pH 5 were determined to be tobermorite, whereas those at pH 3 and pH 1, Na-P1 and Na-X zoelite respectively. CaO was found to inhibit the synthesis of zeolite.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.657-662
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• 2005

Iron sulfide(FeS) is significantly produced through both abiotic and biotic processes in natural sediments and pore waters. In this study, chromium(VI) reaction with iron sulfide at various initial concentrations and at pH values of 4 and 8 was conducted to better understand the interactions between Cr(VI) and Fe(II) species dissolved from iron sulfide in both the aqueous and solid phases. Also, the removal efficiency of iron sulfide was compared with zero valent iron and other iron bearing oxides such as ${\alpha}-Fe_2O_3$, ${\alpha}-FeOOH$ and $Fe_3O_4$. The Cr(VI) removal rate by iron sulfide was higher at pH 4 than at pH 8 because more dissolved Fe(II) existed at pH 4 than at pH 8. Chromium and iron(oxyhydroxide) could be identified on the iron sulfide surface with transmission microscopy imaging and energy dispersive spectroscopy. The removal capacity of iron sulfide was much higher than zero valent iron and other iron oxide minerals due to the synergic effect of hydrogen sulfide and ferrous iron.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.94-98
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• 2005

Coptp films with the additive elements (X=Fe, Mn) of varying concentrations were prepared by in-situ electrodeposition, to tailor their magnetic properties. Alloys of CoPtP-X (X=Fe, Mn) were synthesized by changing the solution concentrations of Fe and Mn for electrodeposition. In the electrodeposited CoFePtP alloys, preferred orientation of the electrodeposited films changed from hexagonal (001) to (100) direction with increasing iron contents as revealed by X-ray diffraction, and these films exhibited various magnetic properties ranging from a typical hard magnetic to a soft magnetic property in accordance with microstructural variations. In the case of Mn addition, excellent hard magnetic property was observed at a specific Mn concentration of 0.0126 M in the electrolyte, with the coercivity of 4630 Oe and squareness of 0.856 and this was attributed to the fact that magnetization easy-axis (hexagonal c-axis) coincides with the preferred growth orientation of the film confirmed by transmission electron microscopy.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.15-22
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• 2017

An oxidation-reduction scheme is an alternative approach for improving the galvanizability of advanced high-strength steel in the continuous hot-dip galvanizing process. Here, we investigated the effect of oxygen partial pressure ($P_{O_2}$) on the oxidation behavior of a transformation-induced plasticity steel containing 1.5 wt% Si and 1.6 wt% Mn during heating to and holding for 60 s at $700^{\circ}C$ under atmospheres with various $P_{O_2}$ values. Irrespective of $P_{O_2}$, a thin amorphous Si-rich layer of Si-Mn-O was formed underneath the Fe oxide scale (a $Fe_2O_3/Fe_3O_4$ bilayer) in the heating stage. In contrast to Si, Mn tended to segregate at the scale surface as $(Fe,Mn)_2O_3$. The multilayered structure of $(Fe,Mn)_2O_3/Fe_2O_3/Fe_3O_4$/amorphous Si-Mn-O remained even after extended oxidizing at $700^{\circ}C$ for 60 s. $Fe_2O_3$ was the dominantly growing oxide phase in the scale. The enhanced growth rate of $Fe_2O_3$ with increasing $P_{O_2}$ resulted in the formation of more Kirkendall voids in the amorphous Si-rich layer and a less Mn segregation at the scale surface. The mechanisms underlying the absence of FeO and the formation of Kirkendall voids are discussed.