• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1741-1747
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• 2012

Water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface of the nanocrystals with conventional aminoacids ligands: serine and threonine. The aminoacids capped ZnS:Mn nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES and FT-IR spectroscopy. The optical properties were also measured by UV/Vis and solution photoluminescence (PL) spectroscopies in aqueous solvents. The solution PL spectra showed broad emission peaks around 600 nm with PL efficiencies of 9.7% (ZnS:Mn-Ser) and 15.4% (ZnS:Mn-Thr) respectively. The measured particle sizes for the aminoacid capped ZnS:Mn nanocrystals by HR-TEM images were about 3.0-4.0 nm, which were also supported by Debye-Scherrer calculations. In addition, cytotoxic effects of four aminoacids capped ZnS:Mn nanocrsystals over the growth of wild type E. coli were investigated. Although toxicity in the form of growth inhibition was observed with all the aminoacids capped ZnS:Mn nanocrystals at higher dose (1 mg/mL), ZnS:Mn-Met and ZnS:Mn-Thr appeared non-toxic at doses less than 100 ${\mu}g$/mL. Low biological toxicities were seen at doses less than 10 ${\mu}g$/ mL for all nanocrystals.

• 한국환경농학회지
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• 제29권1호
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• pp.77-85
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• 2010

Reactive oxygen species (ROS) are very harmful to living organisms due to the potential oxidation of membrane lipids, DNA, proteins, and carbohydrates. transformed E.coli strain QC 871, superoxide dismutase (SOD) double-mutant, with three sequence variant MnSOD1, MnSOD2, and MnSOD3 manganese superoxide dismutase (MnSOD) gene isolated from wheat. Although all QC 871 transformants grown at $37^{\circ}C$ expressed mRNA of MnSOD variants, only MnSOD2 transformant had functional SOD activity. MnSOD3 expressed active protein when grown at $22^{\circ}C$, however, MnSOD1 did not express functional protein at any growing and induction conditions. The sequence comparison of the wheat MnSOD variants revealed that the only amino acid difference between the sequence MnSOD2 and sequences MnSOD1 and 3 is phenylalanine/serine at position 58 amino acid. We made MnSOD2S58F gene, which was made by altering the phenylalaine to serine at position 58 in MnSOD2. The expressed MnSOD2S58F protein had functional SOD activity, even at higher levels than the original MnSOD2 at all observed temperatures. These data suggest that amino acid variation can result in highly active forms of MnSOD and the MnSOD2S58F gene can be an ideal target used for transforming crops to increase tolerance to environmental stresses.

• Metals and materials international
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• 제24권6호
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• pp.1394-1402
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• 2018

This study investigates the mechanism of MnS precipitation on $Al_2O_3-SiO_2$ inclusions during the solidification of non-oriented silicon steel, especially the influence of the phase structures and sizes of the oxides on the MnS precipitation, by scanning electron microscopy and transmission electron microscopy coupled with energy dispersive spectrometry. The investigation results show that MnS tends to nucleate on submicron-sized $Al_2O_3-SiO_2$ inclusions formed by interdendritic segregation and that it covers the oxides completely. In addition, MnS can precipitate on micron-sized oxides and its precipitation behavior is governed by the phase structure of the oxides. The MnS embryo formed in a MnO-containing oxide can act as a substrate for MnS precipitation, thus permitting further growth via diffusion of solute atoms from the matrix. MnS also precipitates in a MnO-free oxide by the heterogeneous nucleation mechanism. Furthermore, MnS is less prone to precipitation in the $Al_2O_3$-rich regions of the $Al_2O_3-SiO_2$ inclusions; this can be explained by the high lattice disregistry between MnS and $Al_2O_3$.

• 한국재료학회지
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• 제21권1호
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• pp.46-49
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• 2011

Bi co-doped ZnS:Mn,Bi yellow phosphors for white light emitting diodes were prepared by the conventional solidstate reaction method. The optical and structural properties of ZnS:Mn,Bi phosphors were investigated by x-ray diffraction, scanning electro microscopy and photoluminescence. ZnS:Mn,Bi phosphors showed XRD patterns of hexagonal structure. The photoluminescence of ZnS:Mn,Bi phosphors showed spectra extending from 480 to 700 nm, peaking at 580 nm. The photoluminescence of 580 nm in the ZnS:Mn,Bi phosphors was associated with the 4T1 ${\rightarrow}$ 6A1 transition of the Mn2+ ions. The highest photoluminescent intensity of the phosphors under 405 nm and 450 nm excitation was obtained at Bi concentration of 7mol%. The optimum mixing conditions with epoxy and yellow phosphor for white light emitting diodes were observed in a ratio of epoxy:yellow phosphor of 1:3.5. The CIE chromaticity of the white LED at the 1:3.5 ratio was X = 0.3454 and Y = 0.2449.

• 자원환경지질
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• 제51권5호
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• pp.401-407
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• 2018

폐광산에서 유출되는 광산배수 내 중금속을 처리하기 위해 자연정화법 및 물리화학처리 등 다양한 방법이 사용되고 있다. 특히 광산배수 내 중금속 중 망간은 처리되기 위해 pH 9 이상의 조건이 필요하기 때문에 처리하기 어려운 원소 중 하나이다. 본 연구에서는 광산배수 내 망간의 효율적인 제거방법을 연구하기 위해 다양한 제강슬래그 복합매질체 반응조(제강슬래그(S), 제강슬래그+석회석(S+L), 제강슬래그+망간코팅자갈(S+G))를 사용하여 경쟁원소인 철 유입에 따른 망간의 제거효율을 평가하였다. 철 유입이 없는 358일간의 실험에서는 평균 pH 6.7의 고농도 망간(30~50 mg/L)이 포함된 원수를 사용했으며 제강슬래그 반응조 유출수는 pH 8.9~11.4에서 평균 99.9%의 지속적으로 높은 망간제거효율을 보였다. 철 유입 없이 망간제거실험을 진행한 반응조를 이용하여 망간농도 40~60 mg/L의 원수에 철을 추가로 유입하여 237일간의 실험을 진행하였다. 망간 제거 이후 pH는 6.1~10.0 범위로 증가하였으며 철 유입 전에 비해 낮은 범위를 보였다. S반응조가 pH 7.1~9.9로 가장 높았으며 S+L 반응조, S+G 반응조가 그 뒤를 이었다. 하지만 망간제거효율은 비교적 낮은 pH 범위임에도 불구하고 S+L 반응조가 94~100%로 가장 높았으며 S반응조와 S+G 반응조는 약 68~100%의 범위의 효율을 보였다. S+L반응조가 철 유입에 가장 높은 저항성을 나타냈으며 이는 pH 이외에도 석회석에 의해 공급된 탄산염에 의한 $MnCO_3$의 형성 또는 자가촉매반응이 망간제거에 기여했다고 판단할 수 있다. X선 회절 분석을 통해 S+L 반응조 침전물에서 로도크로사이트(rhodochrosite, $MnCO_3$)를 확인할 수 있었다. 광산배수 내 망간을 처리하는데 가장 효율적인 반응조는 제강슬래그+석회석 반응조로 나타났으며, 본 연구결과는 철의 유입에 따른 비교적 낮은 pH(9 이하) 범위에서도 망간이 효율적으로 제거될 수 있는 공법을 선정하는데 기여 할 수 있다.

• 대한전기학회논문지
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• 제41권5호
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• pp.508-516
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• 1992

In this study, dielectric and piezoelectric properties of 0.05Pb(AlS12/3TWS11/3T)OS13T-0.95Pb(ZrS10.52TTiS10.48T)OS13T system ceramics were investigated with respect to the variations of MnOS12T and FeS12TOS13T additions amounts. The results obtained in this study are summarized as follows: 1. As the amounts of MnOS12T and FeS12TOS13T are increased, tetragonality(c/a) and apparent density were decreased but grain size was increased, also the limits of solubility were revealed because pores were formed at the amounts of 0.3wt% MnOS12T and 0.5wt% FeS12TOS13T. 2. AS the increasing of amounts of MnOS12T and FeS12TOS13T, the temperature of phase transition(TS1cT) was decreased, and pemeability had maximum value at the amount of 0.3wt% MnOS12T but were sharply decreasd for the increasing FeS12TOS13T amounts. 3. As the amounts of MnOS12T and FeS12TOS13T are increased, the electro-mechanical coupling factor(kS1pT) was decreased from 60% to 41%, 19% respectively, but mechanical quality factor(QS1mT) had maximum values 720 for amount of 0.3wt% MnOS12T and 320 the amount of 0.5wt% FeS12TOS13T.

• Journal of Magnetics
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• 제6권4호
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• pp.145-147
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• 2001

The effect of interface roughness between [Ni/Mn] superlattice and pinned NiFe layer on magnetoresistance (MR) of [Ni/Mn] superlattice-based spin valve films was investigated. Antiferromagnetic phase structure and interface roughness of [Ni/Mn] superlattice spin valve films were compared in the as-deposited and the annealed samples at 240$\^{C}$, respectively. Surface morphology of spin valves was substantially flattened due to the formation of the antiferromatic NiMn phase. In case of Co insertion between Cu and NiFe, the interlace roughness and MR ratio in the annealed [NiMn] superlattice and pinned NiFe/Co layer increased more than those in the annealed [Ni/Mn] superlattice and pinned NiFe layers respectively.

• Bulletin of the Korean Chemical Society
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• 제35권4호
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• pp.1169-1176
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• 2014

In this study, water-dispersible ZnS:Mn nanocrystals were synthesized by capping the surface with conventional and simple structured amino acid ligands: $\small{L}$-Glycine and $\small{L}$-Alanine. The ZnS:Mn-Gly and ZnS:Mn-Ala nanocrystal powders were characterized by XRD, HR-TEM, EDXS, ICP-AES, and FT-IR spectroscopy. The optical properties were measured by UV-Visible and photoluminescence (PL) spectroscopy. The PL spectra for the ZnS:Mn-Gly and ZnS:Mn-Ala showed broad emission peaks at 599 nm and 607 nm with PL efficiencies of 6.5% and 7.8%, respectively. The measured average particle size from the HR-TEM images were $6.4{\pm}0.8$ nm (ZnS:Mn-Gly) and $4.1{\pm}0.5$ nm (ZnS:Mn-Ala), which were also supported by Debye-Scherrer calculations. In addition, the degree of aggregation of the nanocrystals in aqueous solutions were measured by a hydrodynamic light scattering method, which showed formation of sub-micrometer size aggregates for both ZnS:Mn-Gly ($273{\pm}94$ nm) and ZnS:Mn-Ala ($233{\pm}34$ nm) in water due to the intermolecular attraction between the capping amino acids molecules. Finally, the cytotoxic effects of ZnS:Mn-Gly and ZnS:Mn-Ala nanocrsystals over the growth of wild type E. coli were investigated. As a result, no toxicity was shown for the ZnS:Mn-Gly nanocrystal in the colloidal concentration region from 1 ${\mu}g/mL$ to 1000 ${\mu}g/mL$, while ZnS:Mn-Ala showed significant toxicity at 100 ${\mu}g/mL$.

• 소성∙가공
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• 제9권1호
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• pp.66-71
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• 2000

The present study tackles the metallurgical subjects involving the thin slab-direct hot rolling process, i.e. mini-mill process. In order to clarify the effect of chemical composition of steel and MnS precipitation behaviors on the development of edge cracking during hot rolling, the content of manganese and sulfur in low carbon steel was varied and the isothermal treatment prior to roughing was applied. Edge cracking during roughing in the hot-rolling process of mini-mill was effectively prevented by means of the isothermal treatment at 115$0^{\circ}C$ for 5 minutes in the 0.4% manganese steel containing sulfur lower than 0.013%. With the increase in manganese content in low carbon steel, coarser MnS developed. The edge cracking index which denotes the total length of edge crack per unit edge-length of rolled specimens was proposed in this paper. It was found that the edge cracking index linearly decreased with the increase in the ratio of MnS.

• Metals and materials international
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• 제24권6호
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• pp.1333-1345
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• 2018

The effect of manganese sulfide (MnS) inclusions on the machinability of free-cutting steel is based on their morphology, size and distribution. Furthermore, the plasticity of MnS is high during the hot working caused different characterization of MnS. In this study, the deformation behavior of MnS in 1215MS steel after a thermomechanical process was investigated at 1323 K. The microstructures of MnS inclusions were characterized by optical microscopy, scanning electron microscopy, energy-dispersive spectrometry, and electron backscattering diffraction (EBSD). As the thickness reduction of the inclusions increased from 10 to 70%, their average aspect ratio increased from 1.20 to 2.39. In addition, the deformability of MnS inclusions was lower than that of the matrix. The possible slip systems of A, B, C, and D plane traces were (${\bar{1}}0{\bar{1}}$)[${\bar{1}}01$], ($10{\bar{1}}$)[101], (011)[$01{\bar{1}}$], and (110)[$1{\bar{1}}0$]. Furthermore, the EBSD measurements suggested that slip planes in MnS inclusions occur on {110} planes.