• Journal of Korea Foundry Society
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• v.30 no.4
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• pp.130-136
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• 2010

Sulfide segregation behavior, characteristics of solidification microstructure and compositional distribution in the riser/castings junction of heavy-section main bearing support (MBS) steel castings were investigated; Sulfide streaks of A segregation were formed in the transitional region from columnar grain to coarse equiaxed grain and floated with aggregation of the dendritic free crystal. Solute segregation behaviors of elements Si, P and S were V shape negative segregation from the bottom of the castings to upper part of the riser with the reference of vertical center-line of the specimen block. Those of elements C and Mn were V shape negative segregation in the main body and A shape positive segregation in the riser of the casting. Just beneath the pipe shrinkage in the riser segregation ratio of each element was the highest, and that of S was 3.6 times higher, C 3.3 times, P 2.1 times, Si 1.6 times and Mn 1.0 times respectively. [Mn/S] ratio of the specimen block was distributed in the wide range of 20~275.

• Korean Journal of Crystallography
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• v.13 no.2
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• pp.63-68
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• 2002

Zn/sub 2-x/Mn/sub x/SiO/sub 4/ phosphors for PDP were synthesized by solid state reaction method. The effects of firing temperature, ratio of hydrogen gas to nitrogen for heat treatment and concentration of activator and co-dopants on the luminous properties have been investigated. It was found that the phosphor fabricated at 1400℃ with x = 0.002 Mn concentration had a maximum brightness. Luminous properties of a phosphor were improved when Cr/sup 3＋/ was added as a co-dopant rather than other co-dopants.

• Korean Journal of Materials Research
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• v.14 no.12
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• pp.863-869
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• 2004

The purpose of this research is to investigate the mechanical property and ductile-brittle transition temperature of Ti-Nb-P added extra low carbon interstitial free steel having a tensile strength of 440 MPa. The mechanical property and transition temperature of hot rolled steel sheets were more influenced by the coiling temperature rather than by the small amount of alloying element. Further, at the same composition, the property of the specimen coiled at low temperature was superior to that obtained at higher coiling temperature. The fracture surface of 0.005C-0.2Si-1.43Mn steel coiled at $630^{\circ}C$ showed a ductile fracture mode at $-100^{\circ}C$, but coiling at $670^{\circ}C$ showed a transgranular brittle fracture mode at $-90^{\circ}C$. The galvannealed 0.006C-0.07Si-1.33Mn steel sheet annealed at $810^{\circ}C$ has tensile strength and elongation of 442.8 MPa and $36.6\%$, respectively. The transition temperature of galvannealed 0.006C-0.07Si-1.33Mn steel sheet was increased with a drawing ratio, and the transition temperature of the galvannealed 0.006C-0.07Si-1.33Mn steel was $-60^{\circ}C$ at a drawing ratio of 1.8

• Journal of the Korean Magnetics Society
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• v.9 no.6
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• pp.306-311
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• 1999

$La_{2/3}Sr_{1/3}MnO_3(LSMO)/YSZ/SiO_2/Si(100)$ polycrystalline thin films were fabricated be chelated sol-gel method The effect of YSZ buffer layer at low field (120 Oe) spin-polarized tunneling magnetotransport (TMR) properties of LSMO thin film was studied at room temperature. Single perovskite LSMO thin films was obtained. The maximum TMR ratio was increased from 0.2 to 0.42 % by the insertion of YSZ buffer. YSZ as diffusion barrier was attributed to the fine microstructure of LSMO thin films and the reduction of dead layer between LSMO and $SiO_2/Si(100)$ interfaces.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4205-4209
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• 2011

The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ silicate was prepared by blending of $Li_2MnSiO_4$ and $Li_2FeSiO_4$ precursors with same molar ratio. The one of the silicates of $Li_2FeSiO_4$ is known as high capacitive up to ~330 mAh/g due to 2 mole electron exchange, and the other of $Li_2FeSiO_4$ has identical structure with $Li_2MnSiO_4$ and shows stable cycle with less capacity of ~170 mAh/g. The major drawback of silicate family is low electronic conductivity (3 orders of magnitude lower than $LiFePO_4$). To overcome this disadvantage, carbon composite of the silicate compound was prepared by sucrose mixing with silicate precursors and heat-treated in reducing atmosphere. The crystal structure and physical morphology of $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ was investigated by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. The $Li_2Mn_{0.5}Fe_{0.5}SiO_4$/C nanocomposite has a maximum discharge capacity of 200 mAh/g, and 63% of its discharge capacity is retained after the tenth cycles. We have realized that more than 1 mole of electrons are exchanged in $Li_2Mn_{0.5}Fe_{0.5}SiO_4$. We have observed that $Li_2Mn_{0.5}Fe_{0.5}SiO_4$ is unstable structure upon first delithiation with structural collapse. High temperature cell performance result shows high capacity of discharge capacity (244 mAh/g) but it had poor capacity retention (50%) due to the accelerated structural degradation and related reaction.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.785-792
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• 2011

Equal channel angular(ECA) pressing is the established processing technique in which a polycrystalline metal is pressed through the die to achieve a very high plastic strain. Therefore, the capability to produce an ultra-fine grain size in the materials is provided. To investigate that mechanical properties at elevated temperature have the ultrafine grain ECA pressing, experiments were conducted on an Al-4.8% Mg-0.07% Mn-O.06% Si alloy. After having been solution treated at 773K for 2hrs, the billet for ECA pressing was inserted into the die. And it was pressed through two channel of equal to cross section intersecting at a 90 degree angle. The billet can be extrude repeatedly because of 1:1 extrusion ratio. Since the billet is passed through the cannel for 2 times, a large strain is accumulated in the alloy. The tensile tests on elevated temperature were carried out with initial strain rate of $10^{-3}s^{-1}$ at eight temperature distributed from 293K to 673K.

• Journal of the Korean Magnetics Society
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• v.12 no.2
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• pp.64-67
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• 2002

IrMn pinned spin valve (SV) films with stacks of Ta/NiFe/IrMn/CoFe/Cu/CoFe/NiFe/Ta were prepared by dc sputtering onto thermally oxidized Si (111) substrates at room temperature under a magnetic field of about 100 Oe. The annealing cycle number and temperature dependence of exchange coupling field (H$_{ex}$), magnetoresistance (MR) ratio, and coercivity (H$_{c}$) were investigated. By optimizing the process of deposition and post thermal annealing condition, we obtained the IrMn based SV films with MR ratio of 3.6%, H$_{ex}$ of 1180 Oe for the pinned layer. The H$_{ex}$ is stabilized after the second annealing cycle and it is thought that this SV reveals high thermal stability. The H$_{ex}$ maintained its strength of 600 Oe in operation up to 24$0^{\circ}C$ and decreased monotonically to zero at 27$0^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.170-175
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• 2004

The ferroelectric (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ thin films were fabricated by sol-gel method using Y-acetate, Yb-acetate, and Mn-acetate as raw materials. The stable (Y $b_{x}$ $Y_{1-x}$)Mn $O_3$ precursor solution (sol) was prepared through the reflux process with acetylaceton as a catalyst and coated on Si(100) substrate by spin coating. The heat treatment temperature and, Rw ($H_2O$/alkoxide moi ratio) dependence on crystallinity of thin films were studied. The lowest temperature for obtaining YbMn $O_3$phase and the optimum heat-treatment conditions were proved as at 7$50^{\circ}C$ and 80$0^{\circ}C$, respectively. The hexagonal YbMn $O_3$with c-axis preferred orientation could be obtained at Rw=1 condition. The remanent polarization for the thin films of x=0 or 1 was about 200 nC/㎤ while, for the specimens ot 0< x< 1, were 50∼100 nC/$\textrm{cm}^2$.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.2
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• pp.79-85
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• 2008

It is important to consider the life of battery and low power operation for various wireless communications. Thus, Analog current-mode signal processing with SI circuit has been taken notice of in designing the LSI for wireless communications. However, in current mode signal processsing, current memory circuit has a problem called clock-feedthrough. In this paper, we examine the connection of CMOS switch that is the common solution of clock-feedthrough and calculate the relation of width between CMOS switch for design methodology for improvement of current memory. As a result of simulation, when the width of memory MOS is 20um, ratio of input current and bias current is 0.3, the width relation in CMOS switch is obtained with $W_{Mp}=5.62W_{Mn}+1.6$, for the nMOS width of 2~6um in CMOS switch. And from the same simulation condition, it is obtained with $W_{Mp}=2.05W_{Mn}+23$ for the nMOS width of 6~10um in CMOS switch. Then the defined width relation of MOS transistor will be useful guidance in design for improvement of current memory.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.2
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• pp.207-213
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• 2016

This study is focused on manganese (Mn(II)) removal by potassium permanganate ($KMnO_4$) in surface water. The effects of bicarbonate on Mn(II) indicated that bicarbonate could remove Mn(II), but it was not effectively. When 0.5 mg/L of Mn(II) was dissolved in tap water, the addition of $KMnO_4$ as much as $KMnO_4$ to Mn(II) ratio is 0.67 satisfied the drinking water regulation for Mn (i.e. 0.05 mg/L), and the main mechanism was oxidation. On the other hand, when the same Mn(II) concentration was dissolved in surface water, the addition of $KMnO_4$, which was the molar ratio of $KMnO_4/Mn(II)$ ranged 0.67 to 0.84 was needed for the regulation satisfaction, and the dominant mechanisms were both oxidation and adsorption. Unlike Mn(II) in tap water, the increasing the reaction time increased Mn(II) removal when $KMnO_4$ was overdosed. Finally, the optimum conditions for the removals of 0.5 - 2.0 mg/L Mn(II) in surface water were both $KMnO_4$ to Mn(II) ratio is 0.67 - 0.84 and the reaction time of 15 min. This indicated that the addition of $KMnO_4$ was the one of convenient and effective methods to remove Mn(II).