• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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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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• 제3권4호
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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.

• 열처리공학회지
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• 제7권2호
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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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• 제20권5호
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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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• 제20권3호
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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.

• 한국진공학회지
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• 제5권3호
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• pp.258-262
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• 1996

d.c.magnetron sputtering 방법으로 제작된 Fe/[NiFe/Cu] 다층박막을 Fe 기저층의 두께, 적층횟수 및 열처리 온도 변화에 따라 자기저항비가 계면 거칠기 및 우선 배향에 미치는 영향에 대하여 조사하였다. Fe 기저층의 두께가 증가함에 따라 (200) 우선 배향의 세기라 증가하였으며, 자기저항비는 Fe70$\AA$의 두께어서 최대값 4.7%를 보이며 이때 자장감응도도 최대를 나타낸다. Fe 기저층의 두께를 70$\AA$ 으로 고정시키고 적층횟수를 변화시켰을 때 40층에서 최대값 5.3%를 보였다. 열처리 온도에 따른 자기저항비는 $300^{\circ}C$이하에서는 커다란 변화가 없으며, $300^{\circ}C$이상에서는 크게 감소하였는데, 이는 Cu의 확산에 의한 상자성 혼합층의 증가와 반강자성석으로 결함된 자성층간의 배열의 변화가 그 원인이다.

• 한국환경과학회지
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• 제16권12호
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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.

• 한국재료학회지
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• 제28권7호
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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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• 제6권5호
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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.

• 한국자기학회지
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• 제10권4호
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• pp.171-177
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• 2000

RF 마그네트론 스퍼터링 증착법으로 제작한 Co/NiMn 이층막에서의 교환자기결합현상을 연구하였다. 어닐링의 온도와 시간에 따른 교환자기결합력(H$_{ex}$)의 변화를 조사하여 300 $^{\circ}C$에서 13시간의 열처리후에 최대의 교환결합자장을 얻을 수 있음을 보였고, NiMn과 Co층의 적층순서를 변화시켰을 때, NiMn 상층구조의 시편이 더 높은 교환자기결합력을 나타냄을 알 수 있었다. 상층의 Ta 보호막의 사용이 교환자기결합을 나타내는데 필수적임을 알 수 있었는데 , AES 분석은 Ta 보호층을 적용하지 않은 경우에, 산소원자가 막 내부의 깊은 곳까지 침투함으로 인하여 교환자기결합력이 일어나지 않음을 보여주었다. 또한 교환자기결합에 대한 Ta 바닥층의 효과를 연구하였다. Ta 바닥층은 높은 교환자기결합력을 얻기 위해서는 사용하지 않는 것이 낫다는 것을 알아내었다. X선 회절분석의 결과는, Ta 바닥층이 다층막에 우선방위조직을 형성시키는데 기여하지만, NiFe/NiMn 이층막에서의 경우와는 달리 교환자기결합에 반드시 필요한 조건이 아님을 보여주었다. 또한 Co층과 NiMn층의 두께에 따른 교환결합력의 영향을 조사하여, 교환결합력은 200 $\AA$ 이상의 NiMn층 적용 시 최대값을 가지며, Co층의 두께에 반비례함을 알 수 있었다.다.