• Proceedings of the KSME Conference
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• 2004.04a
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• pp.342-347
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• 2004

The deformation behavior of a $Zr_{55}Al_{10}Ni_5Cu_{30}$ bulk metallic glass under tensile loading at different range of strain rates and temperatures between 680 K and 740 K were investigated. The variation in the deformation behavior of $Zr_{55}Al_{10}Ni_5Cu_{30}$ bulk metallic glass which resulted from the crystallization induced during testing was reported. The$Zr_{55}Al_{10}Ni_5Cu_{30}$ bulk metallic glass has showed either homogeneous or inhomogeneous deformation depending on test condition. It exhibited a maximum elongation of about 560 % at the condition of $407^{\circ}C{\times}\;10^{-4}/s$. The flow behavior exhibited three different types and the flow stress became lower at higher temperatures and lower strain rates. The increase of the time elapsed during heating resulted in the partial crystallization of bulk metallic glass phase and eventually strain hardening and brittle fracture.

• Advances in environmental research
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• v.3 no.4
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• pp.321-335
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• 2014

Eight trace metals, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn, were measured in the urban soil of Guwahati City, Assam, India from 31 sites representing five different types of land use, residential, commercial, industrial, public utilities, and roadside. Cd and Co occurred in very low concentrations (Cd << Co) in all types of land use without any significant variation from one type of land use to another. Ni concentrations were more than those of Co, and the concentrations depended on land use pattern. Average Cr and Cu concentrations were ${\geq}100mg/kg$, but Cr had a significantly higher presence in industrial land use. Pb concentrations showed similar trends. The two metals, Mn and Zn, were present in much larger amounts compared to the others with values ${\geq}300mg/kg$. Industrial and roadside soil contained much more Mn while commercial soil was enriched with Zn. Toxicity Characteristic Leaching Procedure (TCLP) was used for elucidating the mobility characteristics of the eight heavy metals. Mn suffered the highest leaching from commercial land (9.9 mg/kg on average) and also from other types of land. Co, Cu and Pb showed higher leachability from commercial soils but the leached concentrations were less than those of Mn. The two metals, Zn and Ni, were leached from residential land in considerable amounts. The TCLP showed Mn to be the most leachable metal and Cr the least.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.2
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• pp.129-138
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• 1994

The purpose of this study is to clarify the influence of the reaction temperature and $AlCl_3$ content on the aluminide coating formation on Ni-based superalloy IN713C in CVD process and to compare its throwing power with that of Pack Cementation process. Aluminide coating was formed by CVD in hot-wall stainless tube reactor from an $AlCl_3-H_2$ mixture in the temperature range $850{\sim}1050^{\circ}C$. At reaction temperature $850^{\circ}C$, the coating thickness and the content of aluminium at the surface were increased as $AlCl_3$ heating temperature was raised. At reaction temperature $1050^{\circ}C$, they were not influenced by the variation of $AlCl_3$ heating temperature. When $AlCl_3$ heating temperature was fixed $125^{\circ}C$, the phases of the coatings were varied from $Ni_2Al_3$ to Al-rich NiAl and to Ni-rich NiAl with the reaction temperature. Therefore, in this study the reaction temperature has been found to be a major factor in determining the phase formed in CVD process. The throwing power of CVD was superior to that of Pack Cementation.

• Bulletin of the Korean Chemical Society
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• v.20 no.5
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• pp.508-516
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• 1999

Polycrystalline powder of LixNi0.85Co0.15O2 was synthesized by pyrolyzing a powder precursor obtained by the PVA-precursor method. Coin cells of lithium-ion rechargeable battery were assembled, whose the cathodes were fabricated from the crystalline powders of LixNi0.85Co0.15O2 synthesized by the method. The effect of synthetic variation on the property of the cell was tested by carrying out 100 consecutive cycles of charge-dis-charge on the cells. The property of the cell was largely influenced by the pyrolysis conditions applied for the synthesis of the LixNi0.85Co0.15O2. Depending on whether the pyrolysis was carried out in standing air or in the flow of dry air, the discharge capacity and cycle-reversibility of the cell varied in large extent. When the powder precursor was pyrolyzed in standing air, a minor phase of lithium carbonate was remained in the LixNi0.85Co0.15O2. The carbon containing powder precursor had to be pyrolyzed in the flow of dry air to eliminate the minor phase. In the flow of dry air, the lithium carbonate in the precursor was eliminated over 500-700。C without any prominent heat event. By controlling the flow of air over the precursor during its pyrolysis, particle size could also be altered. The effect of flowing dry air, during first step pyrolysis or during second step heat treatment, on the property of the cell was discussed.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.291-296
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• 1999

The immobilization of APTMS(3-(2-aminoethylamino)propyltrimethoxysilane) and AAPTMS(3-(2-(2-aminoethyl)aminoethylanino)propyltrimethoxysilane) on the surface of high quality mesoporous molecular sieves MCM-41 and MCM-48 have been confirmed by F.T.-IR spectroscopy, Raman spectroscopy, 29Si solid state NMR, and a surface polarity measurement using Reichardt's dye. The formation of metal (Co(Ⅱ), Ni(Ⅱ), and Cu(Ⅱ)) complexes by immobilized aminosilanes have been investigated by photoacoustic spectroscopy(PAS). The assignment of UV-Vis. PAS bands makes it possible to identify the structure of metal complexes within mesoporous molecular sieves. Co(Ⅱ) ion may be coordinated mainly in a tetrahedral symmetry by two APTMS onto MCM-41, and in an octahedral one by two AAPTMS. Both Ni(Ⅱ) and Cu(Ⅱ) coordinated by aminosilanes within MCM-41 form possibly the octahedral complexes such as [Ni(APTMS)2(H20)2]2+, [Ni(AAPTMS)2]2+, [Cu(APTMS)2(H2O)2]2+, and [Cu(AAPTMS)(H2O)3]2+, respectively. The PAS band shapes of complexes onto MCM-48 are similar to those of corresponding MCM-41 with the variation of PAS intensity. Most of metal ion(Ⅱ) within MCM-41 and MCM-48 are coordinated by aminosilanes without the impregnation on the surface.

• Journal of the Korean Vacuum Society
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• v.5 no.3
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• pp.258-262
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• 1996

We have investigated the changes in magnetoresistive characteristics, interfacial roughness, and preferred orientation with the Fe buffer layer thickness, annealing temperature, and the stacking number of layers variation in Fe/[NiFe/Cu] multilayers by using the 3-gun d.c. magnetron sputtering method. Intensity of the (200) orientation was increased with the increment of the Fe-buffer layer thickness. We found a maximum magnetoresistance ration of 4.7%, when the buffer layer thickness was 70$\AA$, and the field sensitivity also showed a maximum value at the same thickness. We varied the stacking number of multilayers with fixing the Fe buffer layer thickness of 70$\AA$. When the stacking number was 40 layers, maximum MR ratio(5.3%) was observed. With the variation of annealing temperature no change in the MR ratio was found beyond $300^{\circ}C$. But decrement of MR ratio was observed above $300^{\circ}C$. This decrement of the MR ratio was responsible for the increment of paramagnetic mixed layer caused by the diffusion of Cu layer and the change of antiferromagnetic coupling.

• Journal of Environmental Science International
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• v.16 no.12
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• pp.1451-1462
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• 2007

Heavy metal concentrations in the soil were investigated for the abandoned Samkwang metal mine, Cheongyang-Gun, Chungnam Province, Korea. The concentrations of heavy metal(As, Cd, Cu, Ni, Pb, Zn) were determined in mine soils collected at the abandoned mine sites to obtain a general classification and specification of the pollution in this highly polluted region. The results estimated with the normal test and basis statistic on the central tendency and variation showed that the distribution of heavy metal concentration had significantly different at the range of all locations. The range of spatial distribution on the relationship of heavy metal concentration and pH was $4.8{\sim}8.8$ and heavy metal concentration on the type of land use was highest in forest land, and also Ni and Zn in farm and rice field showed the high concentration. The distribution of heavy metal concentration on the depth of a soil showed that the metal concentrations in subsoil were higher than of those in surface soil, while the concentration of Cu and Ni had no significant difference on the depth of soil. Results from the correlation analysis using the data except the extreme and unusual data revel that Zn-Cd(r=0.867), Zn-As(r=0.797), Zn-Pb(r=0.764), Cu-Cd(r=0.673), Cu-As(r=0.614) and Zn-Ni(r=0.605) were the most important parameters in assessing variations of heavy metal in soil. To discriminate pattern differences and similarities among samples, principal factor analysis(PFA) and cluster analysis(CF) were performed using a correlation matrix. This study suggests that PFA and CF techniques are useful tools for identification of important heavy metal and parameters. This study presents the necessity and usefulness of multivariate statistical assessment of complex databases in order to get better information about the quality of soil and gives the basis information to clean up the abandoned mine sites.

• Korean Journal of Materials Research
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• v.28 no.7
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• pp.371-375
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• 2018

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, $Mn_{0.2}Co_{0.8}Fe_2O_4$, $Ni_{0.2}Co_{0.8}Fe_2O_4$, and $Al_{0.2}CoFe_{1.8}O_4$, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of $CoFe_2O_4$. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in $Mn_{0.2}Co_{0.8}Fe_2O_4$ but decreasing in $Ni_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$. All the $M{\ddot{o}}ssbauer$ spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The values of the magnetic hyperfine fields of $Ni_{0.2}Co_{0.8}Fe_2O_4$ are somewhat increased in the A and B sites, while those of $Mn_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$ are decreased. The variation of $M{\ddot{o}}ssbauer$ parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.

• Corrosion Science and Technology
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• v.6 no.5
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• pp.233-238
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• 2007

Due to the occasional occurrence of a localizedcorrosion such as a SCC and pitting in steam generator tubing(Alloy 600), leading to a significant economical loss, an effective repair technology is needed. For a successful electrodeposition inside a tube, many processes should be developed. Among these processes, an anode to be installed inside a tube, a degreasing condition to remove any dirt and grease, an activation condition for a surface oxide elimination, a strike layer forming condition which needs to be adhered tightly between an electroforming layer and a parent tube and a condition for an electroforming layer should be established. Through a combination of these various process condition parameters, the desired material properties can be acquired. Among these process parameters, various material properties including a mechanical property and its variation along with the height of the electrodeposit inside a tube as well as its thermal stability and SCC resistance should be assessed for an application in a plant. This work deals with the material properties of the Ni electrodeposits formed inside a tube by using the anode developed in this study such as the current efficiency, hardness, tensile property, thermal stability and SCC behavior of the electrodeposit in a 40wt% NaOH solution at $315^{\circ}C$. It was found that a variation of the material properties within the entire length of the electrodeposit was quite acceptable and the Ni electrodeposit showed an excellent SCC resistance.

• Journal of the Korean Magnetics Society
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• v.10 no.4
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• pp.171-177
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• 2000

Exchange coupling of Co/NiMn bilayers fabricated by RF magnetron sputtering method was studied. We investigated the variation of exchange coupling field (H$\sub$ex/) for different annealing temperature and time. The maximum exchange coupling field was obtained after 13hr annealing at 300 $^{\circ}C$. With respect to deposition sequence, it was demonstrated that NiMn-top bilayers had higher exchange coupling field than NiMn-bottom bilayers. Ta capping layer was shown to be essential in achieving exchange coupling and Auger Electron Spectroscopy (AES) proved that uncapped NiMn/Co bilayers did not have exchange coupling because of oxygen incorporation into film. We also observed the effect of Ta underlayer on exchange coupling. It was found that Ta underlayer had better not be used for attaining higher exchange coupling. XRD analysis showed that Ta underlayer helped bilayers develop texture, but it was not essential to exchange coupling of Co/NiMn bilayers, which is in contrast to NiFe/NiMn system. Furthermore, the NiMn and Co thickness dependence of exchange coupling has been investigated. The exchange coupling strength reached the maximum above 200 ${\AA}$ NiMn thickness and had inversely proportional relation with Co thickness.