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1
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Improvement of Corrosion Properties of AL-4.08MG Alloy in Seawater by Two Step Anodizing in Electrolyte with Varied Concentration

100%
Lee S., Kim S.
Acta Physica Polonica A
|
2016
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vol. 129
|
issue 4
742-746
EN
Aluminum is extremely active metal on the surface of which the oxide is instantly created when exposed to atmosphere. This naturally generated film has little industrial value as it has thickness as thin as 10 nm. Hence, oxide films are often made thick by electrochemical method. The characteristics of the films can be controlled by varying process parameters including composition, concentration, additives, solution temperature, voltage etc. These films have high hardness and excellent corrosion resistance. Therefore, they are receiving great amount of attention in both academic and industrial areas with their diverse applicability. In this paper, the optimal electrolyte concentration was investigated to produce oxide film with excellent corrosion resistance. The results reveal that Al₂O₃ oxide film was created on the surface for all tested electrolyte concentrations. Moreover, the films have a considerably lower corrosion current density than that of the substrate, implying excellent corrosion resistance.
2
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Investigation of Localized Electric Field in the Type-II InAs/GaAsSb/GaAs Structure

85%
Lee S., Kim J., Yoon S., Kim Y., Lee S., Honsberg C.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 5
1213-1216
EN
The effect of localized electric field (F) was investigated in the type-II InAs/GaAsSb/GaAs structures. To compare type-I to type-II, two types of samples with different Sb contents was grown by molecular beam epitaxy, whose Sb contents are 3% (type-I) and 16% (type-II), respectively. In the both samples, we performed excitation power dependent-photoreflectance at 10 K and the result showed that the period of the Franz-Keldysh oscillation, revealed above the band gap (E_{g}) of GaAs, was broadened in the only type-II system, which means that F was also increased because it is proportional to the period of the Franz-Keldysh oscillation while the period of the Franz-Keldysh oscillations stayed unchanged in type-I system. This phenomenon is explained by that the F was affected by the band bending effect caused by the spatially separated photo-excited carriers in the interface between GaAsSb and GaAs. The F changed linearly as a function of square root of excitation power as expected for the F. Moreover, F was calculated using fast Fourier transform method for a qualitative analysis, which is in a good agreement with the theory of triangular well approximation.
3
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Gamma-C₂S Synthesis from Fly Ash of Fluidize-Bed Boiler for CO₂ Capture

81%
Na S., Kang S., Lee S., Song M.
Acta Physica Polonica A
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2015
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vol. 127
|
issue 4
1282-1285
EN
This paper describes the CO₂ capture performance of cement blended paste incorporating gamma-dicalcium silicate (gamma-C₂S) made with industrial by-products, by taking into consideration of effect of CaCO₃, fly ash replacement ratio under the sintering process. X-ray diffraction method was conducted in order to quantitatively investigate the gamma-C₂S content. CO₂ capture performance of mortar sample incorporating gamma-C₂S was investigated by means of compressive strength test using accelerated carbonation chamber. The experimental results revealed that the kind of CaCO₃ would affect the affect the formation of gamma-C₂S after the sintering with respect to the XRD-Rietveld analysis. Moreover, it is confirmed that compressive strength of mortar sample incorporating gamma-C₂S has the same tendency at curing age of 3, 7 and 28days. Blended mortar sample made with 10 wt.% replacement ratio of gamma-C₂S had high compressive strength value compared to normal mortar sample, therefore, incorporating gamma-C₂S had a positive effect on the compressive strength after accelerated carbonation. Finally, the waste foundry sand powder may be alternative to produce gamma-C₂S.
4
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Corrosion Behavior of Crofer 22APU for Metallic Interconnects in Single and Dual Atmosphere Exposures at 1073 K

81%
Stygar M., Matsuda K., Lee S., Brylewski T.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 5
1394-1398
EN
To determine the impact of an oxidizing Ar-H₂-H₂O/air dual atmosphere on the kinetics and mechanism of oxidation of the Crofer 22APU steel as compared to oxidation in a single atmosphere (Ar-H₂-H₂O or air), the oxidation kinetics of this steel were investigated both in single and dual reaction atmospheres at 1073 K during 100, 250, 500, and 1000 h of oxidation. Detailed morphological observations and the results of chemical composition analyses carried out using transmission electron microscopy combined with energy-dispersive X-ray spectroscopy revealed the presence of Fe in the scale formed on the cathode side in the dual atmosphere. Based on morphological observations (scanning- and transmission electron microscopies) and chemical and phase composition analyses (energy-dispersive X-ray spectroscopy and X-ray diffraction, respectively) of the products of oxidation of the Crofer 22APU steel, and on the determined oxidation kinetics, a mechanism describing scale growth on both sides of the steel during its oxidation in conditions involving a gradient of the chemical potential of oxygen and hydrogen was proposed.
5
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Content available

Design of simultaneous input-shaping-based SIRMs fuzzy control for double-pendulum-type overhead cranes

81%
Qian D., Tong S., Yang B., Lee S.
|
2015
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issue 4
6
Content available remote

Influence of Applied Frequency on Microstructural and Electrochemical Characteristics of Ceramic Coating Produced on Al-Mg Alloy by Pulsed Plasma Electrolytic Oxidation

81%
Lee J., Lee S., Kim S.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 4
753-758
EN
Plasma electrolytic oxidation (PEO) coating is gaining attention as a promising surface treatment technique for lightweight metals and alloys such as Al, Mg and Ti. The coating involves complex interactions among various process parameters including substrate composition, current modes and electrolyte composition. In this study, ceramic coating was produced in silicate based alkaline solution on Al-Mg alloy by pulsed PEO with different applied frequencies (100, 500, 1000, 2000 Hz). The resultant coating was characterized using FE-SEM, EDS and HR-XRD. The electrochemical characteristics of the PEO coating were also investigated in seawater solution. It was found that changing frequency in the PEO process had a prominent effect on both surface and cross-sectional morphology of the coating. The electrochemical studies indicated that the pulsed PEO have improved the corrosion resistance of the Al-Mg substrate. In particular, the applied frequency of 100 Hz has produced one order of magnitude lower corrosion current density than that of the Al-Mg substrate.
7
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Microstructure of Small Amount of TM Added Al-Mg-Si Alloys with Two-Step Ageing

71%
Kuroda Y., Yoshino D., Lee S., Ikeno S., Matsuda K.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1373-1375
EN
Traditionally, Al-Mg-Si alloys are strengthened by dispersed small particles and they have medium strength with good formability. It is well known that alloying elements on Al-Mg-Si alloys (e.g. Cu) can improve mechanical properties because Cu can alter precipitation sequence. In this research, we investigated the effect of transition metals (TM) on Al-1.06at.%MgSi-TM alloys through single- and two-step ageing. Mechanical property and microstructure observation were conducted by micro Vickers hardness measurement and transmission electron microscopy.
8
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TEM Observation of Cu and Ag Added Al-Mg-Si Alloy

71%
Matsumoto A., Nejigaki T., Lee S., Ikeno S., Matsuda K.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1379-1381
EN
It is well known that Cu and Ag addition on Al-Mg₂Si alloy can enhance its mechanical properties due to solid solution hardening. Several reports are available about the effect of each alloying elements, Cu and Ag, on Al-Mg-Si alloys. In this research, Al-Mg-Si-Cu-Ag alloys have chemical compositions of (1) 0.18Cu-0.18Ag and (2) 0.35Cu-0.35Ag [at.%] fixed Cu/Ag rate of 1.0 are prepared using casting to estimate effects of Cu and Ag amount to precipitation behaviour and mechanical properties. The Vickers microhardness measurement was conducted to estimate mechanical property after ageing treatment microstructure observation was carried out using transmission electron microscopy. In peak-aged at 473 K hardness of each alloys was almost the same, but in peak-aged at 523 K, hardness of 0.35Cu-0.35Ag was higher than 0.18Cu-0.18Ag alloy.
9
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Time and Temperature Dependent Damage Characteristics of 5083 Al Alloy under Cavitation-Corrosion Condition

71%
Lee S., Han M., Jeong J., Kim M., Kim S.
Acta Physica Polonica A
|
2016
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vol. 129
|
issue 4
747-752
EN
Continuous efforts to construct high-speed and lightweight ship have been made to reduce cost against growing oil prices. In this context, aluminum has received attention as an alternative material for steel, for small and medium-sized ships. In an effort to extend service life of aluminum, various researches have been attempting to improve the corrosion resistance and anti-corrosion characteristics by applying heat treatment and alloying. The material, however, has a high probability of being attacked by corrosion and erosion, caused by high ship speed in severe marine environments. Cavitation damage is dependent on several important factors, such as shape of objects, surface roughness, rotation speed, fluid pressure and velocity. Vapor pressure, density and surface tension of fluid are also taken into account. In this study, an electrochemical cavitation erosion-corrosion experiment was conducted as a function of solution temperature and applied amplitude for 5083-O aluminum alloy used commercially as a hull material for a small sized ship. The result of the experiment revealed that the damage was accelerated due to synergistic effect of corrosion and erosion as the solution temperature was elevated, and that the weight loss showed a steady increase with increasing time of cavitation.
10
Content available remote

Exchange Coupling in Magnetic Semiconductor Multilayers and Superlattices

62%
Furdyna J., Leiner J., Liu X., Dobrowolska M., Lee S., Chung J., Kirby B.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
973-980
EN
The study of ferromagnetic semiconductors continues to be of great interest because of their potential for spintronic devices. While there has been much progress in our understanding of ferromagnetic semiconductor materials - particularly of the canonical III-V system Ga_{1-x}Mn_xAs - many issues still remain unresolved. One of these is the nature of interlayer exchange coupling in GaMnAs-based multilayers, an issue that is important from the point of view of possible spintronic applications. In this connection, it is important to establish under what conditions the interlayer exchange coupling between successive GaMnAs layers is antiferromagnetic or ferromagnetic, since manipulation of such interlayer exchange coupling can then be directly applied to achieve giant magnetoresistance and other devices based on this material. In this review we will describe magneto-transport, magnetization, and neutron reflectometry experiments applied to two types of GaMnAs-based multilayer structures - superlattices and tri-layers - consisting of GaMnAs layers separated by non-magnetic GaAs spacers. These measurements serve to identify conditions under which AFM coupling will occur in such GaMnAs/GaAs multilayer systems, thus providing us the information which can be used for manipulating magnetization (and thus also giant magnetoresistance) in structures based on the ferromagnetic semiconductor GaMnAs.
11
Content available remote

Influence of Growth Break before Capping on Photoluminescence Dynamics of CdSe/ZnSe Self-Assembled Quantum Dots

62%
Nowak S., Suffczyński J., Goryca M., Kossacki P., Gaj J., Lee S., Furdyna J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1267-1271
EN
Influence of growth breaks before capping of CdSe self-assembled quantum dot layers on photoluminescence dynamics was examined in three samples. Short (5s) break resulted only in a small blue shift, caused probably by partial strain relaxation and/or Zn interdiffusion. Long (20 min) break induced a strong broadening and red shift of the spectra, combined with a dramatic slow down of the photoluminescence decays. The main result of the long break was identified as introduction of defects (impurities), which generate local electric fields and act as traps of photogenerated carriers.
12
Content available remote

Tunneling Magnetoresistance in Ferromagnetic Junctions: Bias Dependence

62%
Barnaś J., Lee S., Holody P., Schelp L., Petroff F., Fert A.
Acta Physica Polonica A
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1998
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vol. 93
|
issue 2
387-391
EN
Electron tunneling between two ferromagnetic electrodes across an insulating barrier is analysed theoretically and experimentally. The barrier is either uniform or it includes a layer of small magnetic metallic particles. Particular attention is paid to the origin of the tunneling magnetoresistance and its bias dependence, as well as to the effects due to Coulomb blockade.
13
Content available remote

Effect of Cu²⁺ Ion Irradiation on Microstructure of Er₂O₃ Coating Layer Formed by MOCVD Method

52%
Tanaka M., Takezawa M., Hishinuma Y., Tanaka T., Muroga T., Ikeno S., Lee S., Matsuda K.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 5
1351-1352
EN
Erbium oxide (Er₂O₃) coating is one of the promising methods to restrict tritium permeation and the magneto hydrodynamic pressure drop for advanced breeding blanket systems. Er₂O₃ coating layer on large interior surface area of metal pipe is deposited by using metal organic chemical vapor deposition process. In this work, the influence of Cu²⁺ ion irradiation on microstructure of Er₂O₃ coating layer on stainless steel 316 (SUS 316) substrate by metal organic chemical vapor deposition methods was investigated using scanning electron microscopy, transmission electron microscopy observation and X-ray diffraction analysis. Microstructure observation of Er₂O₃ coating was carried out after 0.00-1.50 dpa Cu²⁺ ion irradiation at 298 K and 773 K. Scanning electron microscopy observation of the surface area on Er₂O₃ thin film revealed the crack generation on surface after Cu²⁺ ion irradiation. X-ray diffraction peaks were identified in Er₂O₃ after Cu²⁺ ion irradiation transmission electron microscopy observations, the formation of interlayer between Er₂O₃ coating and SUS substrate was confirmed. According to transmission electron microscopy-energy dispersive spectroscopy, the interlayer includes Fe and Cr.
14
Content available remote

AC Microcalorimetry of Superconducting MgCNi_3 Single Crystals

52%
Kačmarčík J., Pribulová Z., Samuely P., Marcenat C., Klein T., Jang D., Lee H., Lee H., Lee S.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
363-366
EN
The low-temperature specific heat of single-crystal samples of superconducting MgCNi_3 with typical dimensions 200 μm were measured for the first time. A computer controlled ac microcalorimeter using an optical fiber and an infrared light-emitting diode as the heat source was used down to 2 K at magnetic fields up to 8 T. The specific heat data suggest a moderate coupling in MgCNi_3.
15
Content available remote

Point-Contact Spectroscopy of Superconducting MgCNi_3 Single Crystals

52%
Pribulová Z., Szabó P., Kačmarčík J., Samuely P., Jang D., Lee H., Lee H., Lee S.
Acta Physica Polonica A
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2008
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vol. 113
|
issue 1
215-218
EN
The first point-contact spectroscopy measurements on MgCNi_3 single crystals of very good quality are presented. The measurements have been performed in the temperature range from 1.5 K up to 10 K and at magnetic fields up to 6 T. The superconducting energy gap Δ of the system is found to be scattered between 1 and 1.2 meV which gives the 2Δ/k T_c ratio between BCS weak-coupling value of ~3.5 and a strong coupling of about 4.2. The excess current evaluated in magnetic field indicates the presence of a single energy gap.
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