• Journal of Powder Materials
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• v.17 no.6
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• pp.456-463
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• 2010

This paper describes the results of the application of Cr-Diamond-like carbon (DLC) films for efficiency improvement through surface modification of spur gear parts in the hydraulic gear pump. Cr-DLC films were successfully deposited on SCM 415 substrates by a hybrid coating process using linear ion source (LIS) and magnetron sputtering method. The characteristics of the films were systematically investigated using FE-SEM, nano-indentation, sliding tester and AFM instrument. The microstructure of Cr-DLC films turned into the dense and fine grains with relatively preferred orientation. The thickness formed in our Cr buffer layer and DLC coating layer were obtained the 487 nm and $1.14\;{\mu}m$. The average friction coefficient of Cr-DLC films considerably decreased to 0.15 for 0.50 of uncoated SCM415 material. The hardness and surface roughness of Cr-DLC films were measured 20 GPa and 10.76 nm, respectively. And then, efficiency tests were performed on the hydraulic gear pump to investigate the efficiency performance of the Cr-DLC coated spur gear. The experimental results show that the volumetric and mechanical efficiency of hydraulic gear pump using the Cr-DLC spur gear were improved up to 2~5% and better efficiency improvement could be attributed to its excellent microstructure, higher hardness, and lower friction coefficient. This conclusion proves the feasibility in the efficiency improvement of hydraulic gear pump for industrial applications.

• Preventive Nutrition and Food Science
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• v.17 no.4
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• pp.299-305
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• 2012

Yam has been recognized having the beneficial effects for the prevention of various diseases, such as cancer, immunity, infection and obesity etc. There is increasing consideration to supplement the antioxidant nutrients to make up the lack of the antioxidant nutrient intakes. No study has been reported for the analysis of antioxidant mineral contents and comparison to dietary recommended intake for the sense of health promotion. In our study, we analyzed the contents of antioxidant trace elements (Zn, Mn, Fe, Cu and Se) and Cr contents in cultivated Korean yam powders for evaluation of nutrient intake aspects. We collected the commercial yam powders from six different cultivated areas in the South Korea and measured antioxidant minerals (Zn, Mn, Fe, Cu and Se) and Cr contents using trace element-free plasma spectrometer (ICP) or atomic absorption spectrometer (AAS) after dry-ashing and then wet-acid digestion. The accuracy of mineral analysis method was confirmed by the mineral analysis of standard reference material. Each analyzed element contents in yam were compared to dietary reference intakes of Koreans (KDRIs). The average levels of trace elements (Zn, Mn, Fe, Cu, Se and Cr) in yam powders were 18.3, 11.9, 36.0, 3.7, 1.9 and 1.27 ${\mu}g/g$ yam powder, respectively. The intakes of Zn, Fe, Cu and Se of which KDRIs is determined, are accounted as being up to 23.8%, 55.6%, 32.5% and 236% recommended intake (RI) of KDRIs, if daily yam supplementation (50 g) of commercial instruction would be considered. The intake of Mn is about 25% adequate intake (AI) of KDRIs with the daily supplementation of yam powder. Most of mineral intakes from daily yam supplementation were with the range of non-detectable to <10% upper limit (UL) level, which is very much safe. The study results show that daily supplementation of Korean yam power is beneficial to provide the supplemental nutrient intake and also is safe, if the suggested dosage would be considered.

• Analytical Science and Technology
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• v.17 no.5
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• pp.416-422
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• 2004

Time-resolved laser induced breakdown spectroscopy (TRELIBS) has been developed and applied to the qualitative analysis of the component materials of nuclear power plant. The alloy samples used in this work were carbon steels (A106 Gr. B; A336 P11; A335 P22), stainless steels (type 304; type 316) and inconel alloys (Inconel 600; Inconel 690; Inconel 800). Carbon steels can be individually distinguished by the intensity ratio of chromium to iron and molybdenum to iron emission lines observed at the wavelength raging from 485 to 575 nm. Type 316 stainless steel can be easily differentiated from type 304 by identification of the molybdenum emission lines at an emission wavelength ranging from 485 to 575 nm: type 304 does not give any molybdenum emission lines, but type 316 does. The inconel alloys can be individually distinguished by the intensity ratio of Cr/Fe and Ni/Fe emission lines at the wavelength raging from 420 to 510 nm. TRELIBS has been proved to be a powerful analytical technique for direct analysis of alloys due to its non-destructivity and simplicity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.3
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• pp.297-302
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• 2022

We investigated the origin of magnetic behaviors induced by an asymmetric spin exchange interaction in Fe-site engineered lead iron niobate [Pb(Fe_1/2Nb_1/2)O₃, PFN], which exhibits a room-temperature multiferroicity. The magnitude of spin exchange interaction was regulated by the introduced transition metals with a distinct Bohr magneton, i.e., Cr, Co, and Ni. All compositions were found to have a single-phase perovskite structure keeping their ferroelectric order except for Cr introduction. We discovered that the incorporation of each transition metal imposes a distinct magnetic behavior on the lead iron niobate system; antiferro-, hard ferro-, and soft ferromagnetism for Cr, Co, and Ni, respectively. This indicates that orbital occupancy and interatomic distance play key roles in the determination of magnetic behavior rather than the magnitude of the individual Bohr magneton. Further investigations are planned, such as X-ray absorption spectroscopy, to clarify the origin of magnetic properties in this system.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.143-143
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• 2017

CrAlN 코팅은 높은 경도, 낮은 표면 조도 등의 상온에서의 우수한 기계적 특성 이외에 고온에서 안정한 합금상의 형성으로 인하여 우수한 내산화성 및 내열성을 보유하여 공구 코팅으로의 적용 가능성이 크다. 그러나 최근 공구사용 환경의 가혹화로 인하여 코팅의 내마모성 및 내열성 등의 물성 향상을 통한 공구의 수명 향상이 필요시 되고 있으며, 다양한 코팅 물질을 활용하여 다층 코팅을 합성함으로써 난삭재용 공구 코팅의 물성을 높이는 연구들이 진행되고 있다. 본 연구에서는 CrAlN 코팅과 WC-Co 6wt.% 모재 사이에 CrZrN, CrN, CrN/CrZrSiN 등의 중간층을 합성하여 CrAlN 코팅의 상온 및 고온 특성을 향상시키는 연구가 진행되었다. 합성된 코팅의 구조 및 물성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, atomic force microscopy(AFM) 및 ball-on-disk wear tester를 사용하였다. 코팅의 고온 특성을 확인하기 위해 코팅을 furnace에 넣어 공기중에서 30분 동안 annealing 한 후에 nano-indentation을 사용하여 경도를 측정하였고, $500^{\circ}C$ annealing 코팅의 표면 조도 분석 및 $500^{\circ}C$에서 마찰마모시험을 실시하였다. CrAlN 코팅의 상온 특성을 분석한 결과, 모든 코팅의 경도(35.5-36.2 GPa)와 탄성계수(424.3-429.2 GPa)는 중간층의 종류에 상관없이 비슷한 값을 보인 것으로 확인됐다. 그러나, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 마찰계수는 0.33로 CrZrN 중간층을 증착한 CrAlN 코팅의 마찰계수(0.41)에 비해 향상된 값 보였으며, 코팅의 마모율 및 마모폭도 비슷한 경향을 보인 것으로 보아 코팅의 내마모성이 향상된 것으로 판단된다. 이것은 중간층의 H/E ratio가 코팅의 내마모성에 미치는 영향에 의한 결과로 사료된다. H/E ratio는 파단시의 최대 탄성 변형율로써, 모재/중간층/코팅의 H/E ratio 구배에 따라 코팅 내의 응력의 완화 정도가 변하게 된다. WC 모재 (H/E=0.040)와 CrAlN 코팅(H/E=0.089) 사이에서 CrN, CrZrSiN 중간층의 H/E ratio는 각각 0.076, 0.083 으로 모재/중간층/코팅의 H/E ratio 구배가 점차 증가함을 확인 할 수 있었고, 일정 응력이 지속적으로 가해지면서 진행되는 마모시험중에 CrN과 CrZrSiN 중간층이 WC와 CrAlN 코팅 사이에서 코팅 내부의 응력구배를 완화시키는 역할을 함으로써 CrAlN 코팅의 내마모성이 향상된 것으로 판단된다. 내열성 시험 결과, CrN/CrZrSiN 중간층을 증착한 코팅은 $1,000^{\circ}C$까지 약 28GPa의 높은 경도를 유지한 것으로 확인 되었다. $500^{\circ}C$ annealing 후 진행된 표면 조도와 마모시험 결과, 모든 코팅의 조도 값 및 마찰계수는 상온 값에 비해 증가하였으며 CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 변화량이 가장 낮은 값을 보였다. 이는 CrZrSiN 중간층 내에 존재하는 $SiN_x$ 비정질상이 고온 annealing시에 산소 차폐막 역할을 하여, 코팅내의 잔류 산소에 의한 산화작용을 효과적으로 방지함으로써 코팅의 고온 특성이 향상된 것으로 판단된다.

• Proceedings of the Mineralogical Society of Korea Conference
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• 2001.06a
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• pp.132-132
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• 2001

옥천변성대의 충주-황강리 지역내 앰피볼라이트의 기원암은 염기성 화성암으로 쏠레이아이트 계열의 변이질암에 속한다. Fe $O^{*}$/MgO값의 변화에 대하여 분별작용에 의해 영향을 받는 주성분 원소와 미량원소들의 변화를 보게되면 Ti $O_2$, Fe $O^{*}$와 불호정성 원소(incompatible element)인 Zr, Nb, Hf, Ta, Th 등은 분별작용동안 증가하는 반면 호정성 원소(compatible element)인 MgO, $Al_2$ $O_3$, Ni, Cr 등은 감소하는 경향을 보여주고 있다. Fe $O^{*}$/MgO, Ti $O_2$ 그리고 Fe $O^{*}$는 심해성 쏠레이아이트 영역으로부터 분화된 경향을 나타내 주고 있다. Ni, Cr은 Fe $O^{*}$/MgO값의 증가에 따라 급속히 감소하며 안정한 대륙과 해저화산의 영역에 도시되고 있으며 칼크-알칼리(CA)와는 관계가 없고 쏠레이아이트의 영역에서 변화 패턴을 보여주어 앰피볼라이트가 활동적인 대륙연변부의 지구조 환경보다는 안정한 대륙이나 해저화산과 관계가 더 있음을 시사한다. 경휘토류 원소(LREE)는 중휘토류 원소(HREE)에 비해 더욱 부화된 특성을 띠고 원자번호가 증가하면서 표준화된 휘토류 원소패턴의 경사가 점차 감소하는 경향을 보여주고 있다. 대부분의 시료들은 큰 Eu이상치를 갖고 있지 않아 마그마 정출 과정동안 사장석의 분별작용이 거의 수반되지 않았음을 지시하고 전체적인 휘토류 원소의 패턴은 거의 평행하게 나타나므로 기원 마그마가 유사함을 의미하고 있다. 비유동성 원소를 이용한 여러 판별도표들을 통해서 본암은 대륙성 현무암질암으로서 판내부 환경에서 유래되었으며 대륙내부 열곡의 알칼리 현무암과 대륙성 현무암 영역에 속하는 것으로 보아서 대륙지각내 열곡작용과 같은 장력운동에 수반되어 생성된 것임을 시사해 주고 있다. 앰피볼라이트의 지각혼성화를 평가하기 위해 이에 필요한 몇 개의 지화학적 매개변수를 계산한 결과 La/Ta, La/Nb, Nb/Th들의 값이 오염 안된 마그마의 값을 지시해 주어 본암이 지각혼성화 작용을 받지 않은 것으로 나타났다. 대부분의 시료들은 P-타입 MORB의 영역에 속하며 소수의 시료가 T-타입 MORB의 영역에 도시되고 있어 본 앰피볼라이트의 생성에는 양적으로 다른 두 가지의 유사한 마그마가 수반된 것으로 추정된다. 것으로 추정된다.

• Journal of Environmental Impact Assessment
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• v.14 no.5
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• pp.355-363
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• 2005

We studied the concentrations of $PM_{10}$ and heavy metal in the incinerators around Dong-hae from December 2003 to April 2004. The seasonal mean of $PM_{10}$ concentration was less than the value of environmental standard, the lowest ($36.59mg/m^3$) in spring and the highest ($78.54mg/m^3$) in fall. The measured seasonal heavy metals were Fe $503,44ng/m^3$, Mg $410.85ng/m^3$, Na $134.14ng/m^3$, Zn $24.58ng/m^3$ in spring and Na $315.29ng/m^3$, Mg $48.36ng/m^3$, Fe $44.78ng/m^3$, Zn $23.34ng/m^3$ in summer and Na $88.53ng/m^3$, Fe $33.80ng/m^3$, Zn $20,43ng/m^3$, Pb $6.16ng/m^3$ in fall and Na $4603.72ng/m^3$, Fe $575,26ng/m^3$, Al $411.01ng/m^3$, Cr $203.51ng/m^3$ in winter. The relationship between measured metals concentrations showed that Na and Fe were associated with natural sources such as soil. Pb, Cr and Zn were strongly related to urban anthropogenic sources such as fuel combustion.

• Korean Journal of Metals and Materials
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• v.48 no.8
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• pp.691-698
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• 2010

A study has been carried out to evaluate the interaction behavior between a lanthanide element and clad material in order to analyze the effect of the lanthanide element on the fuel cladding chemical interaction (FCCI). A diffusion couple test between Misch metal (70Ce-30La) and ferritic-martensitic steel (Gr.92) was performed at $660^{\circ}C$, followed by a microstructural analysis of the coupled sample. The results showed that Ce in the Misch metal, rather than La, reacted with the ferritic-martensitic steel (FMS) to form an interaction layer that penetrated the clad thickness. Fe diffused outside the clad interface to form an $Fe_2Ce$ compound, leaving a depletion of Fe caused by excess diffusion as well as by the formation of Cr-rich precipitation inside the interaction layer. The rate of growth followed the cubic rate law, which indicated that Fe depletion was caused by the diffusion of Fe and that the associated Cr-rich phase formation controlled the whole diffusion process.

• Analytical Science and Technology
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• v.17 no.3
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• pp.199-210
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• 2004

A new polystyrene-divinylbenzene chelating resin containing 4,5-dihydroxy-naphthalene-2,7-disulfonic acid (chromotropic acid : CTA) as functional group has been synthesized and characterized. The sorption and desorption properties of this chelating resin for Cr(III) ion and Cr(VI) ion including nine metal bloodstain. As a results, FOB test kit could be effectively applied to identification of human blood at chelating resin was stable in acidic and alkaline solution. The Cr(VI) ion is selectively separated from Cr (III) ion at pH 2 and the maximum sorption capacity of Cr(VI) ion is 1.2 mmol/g. In the presence of anions such as $F^-$, $SO{_4}^{2-}$, $CN^-$, $CH_3COO^-$, $NO{_3}^-$, the sorption of Cr(VI) ion was reduced but anions such as $PO{_4}^{3-}$ and $Cl^-$ revealed no interference effect. The elution order of metal ions obtained from breakthrough capacity and overall capacity at pH 2 was Cr(VI)>Sn(II)>Fe(III)>Cu(II)>Cd(II)${\simeq}Pb(II){\simeq}Cr(III){\simeq}Mn(II){\simeq}Ni(II){\simeq}Al(III)$. Desorption characteristics for Cr(VI) ion was investigated with desorption agents such as $HNO_3$, HCl, and $H_2SO_4$. It was found that the ion showed high desorption efficiency with 3 M HCl. As the result, the chelating resin, XAD-16-CTA was successfully applied to separation and preconcentration of Cr (VI) ion from several metal ions in metal finishing works.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.3
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• pp.229-234
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• 2001

The EDXRF(Energy Dispersive X-ray Fluorescence Spectrometer) technique was applied to the determination of heavy metals in welding fume. The EDXRF method designed in this study was a non-destructive analysis method. Samples were analyzed directly by EDXRF without any pre-treatment such as digestion and dilution. The samples used to evaluate this method were laboratory samples exposed in a chamber connected with a welding fume generator. The samples were first analyzed using a non-destructive EDXRF method. The samples subsequently were analyzed using AAS method to verify accuray of the EDXRF method. The purpose of this study was to evaluate the possibility of the non-destructive analysis of heavy metals in welding fume by EDXRF. The results of this study were as follow: 1.When the samples were collected under the open-face sampling condition, a surface distribution of welding fume particles on sample filters was uniform, which made non-destructive analysis possible. 2. The method was statistically evaluated according to the NIOSH(National Institute for Occupational Safety and Health) and HSE(Health and Safety Executive) method. 3. The overall precision of the EDXRF method Was calculated at 3.45 % for Cr, 2.57 % for Fe and 3.78 % for Mn as relative standard deviation(RSD), respectively. The limits of detection were calculated at $0.46{\mu}g$/sample for Cr, $0.20{\mu}g$/sample for Fe and $1.14{\mu}g$/sample for Mn, respectively. 4. A comparison between the results of Cr, Fe, Mn analyzed by EDXRF and AAS was made in order to assess the accuracy of EDXRF method. The correlation coefficient between the results of EDXRF and AAS was 0.9985 for Cr, 0.9995 for Fe and 0.9982 for Mn, respectively. The overall uncertainty was determined to be ${\pm}12.31%$, 8.64 % and 11.91 % for Cr, Fe and Mn, respectively. In conclusion, this study showed that Cr, Fe, Mn in welding fume were successfully analyzed by the EDXRF without any sample pre-treatment such as digestion and dilution and a good correlation between the results of EDXRF and AAS was obtained. It was thus possible to use the EDXRF technique as an analysis method of working environment samples. The EDXRF method was an efficient method in a non-destructive analysis of heavy metals in welding fume.