• Economic and Environmental Geology
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• v.30 no.4
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• pp.279-289
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• 1997

Dark to pale green-colored, Cr-bearing sericites from hydrothermal alteration zone of the Narim gold deposit were investigated mineralogically and geochemically. The alteration zone is composed mineralogically of quartz, carbonate minerals and green sericite with minor amounts of chlorite, barite and sulfide minerals (pyrite, sphalerite, galena). The zone is enriched in As (967 to 1520 ppm), Cu (31 to 289 ppm), Ni (1027 to 1205 ppm), Pb (0.20 to 1.24 wt.%) and Zn (1.03 to 1.07 wt. %) compared with fresh rocks such as granitic gneiss, porphyritic biotite granite and basic dyke. The Cr, probably the chromophore element, is highly enriched in the alteration zone (1140 to 1500 ppm), host granitic gneiss (1200 ppm) and porphyritic biotite granite (1200 ppm). Occurrence and grain size of sericite are diverse, but most of the Cr-bearing sericites (150 to $200{\mu}m$ long and 20 to $30{\mu}m$ wide) occur along the boundaries between ore veins and host rocks (especially basic dyke and granitic gneiss). X-ray diffraction data of the sericite show its monoclinic form with unit-cell parameters of $a=5.202{\AA}$, $b=8.994{\AA}$, $c=20.103{\AA}$, ${\beta}=95.746^{\circ}$ and $V=935.83{\AA}^3$, which are similar with the normal 2M1-type muscovite. Representative chemical formula of the sericite is ($K_{1.54}Ca_{0.03}Na_{0.01}$)($Al_{3.42}Mg_{0.38}Cr_{0.14}Fe_{0.06}V_{0.02}$)($Si_{6.69}Al_{1.31}$)$O_{20}(OH)_4$. The Cr content increases with decrease of the octahedral Al content, and ranges from 0.36 to 2.58 wt.%. DTA and TG curves of the sericite show endothermic peaks at $342^{\circ}$ to $510^{\circ}$, $716^{\circ}$ to $853^{\circ}$ and $1021^{\circ}C$, which are due to the expulsion of hydroxyl group. The total weight loss by heating is measured to be about 8.8 wt. %, especially at $730^{\circ}C$. Infrared absorption experiments of the sericite show broad absorption band due to the O-H bond stretching vibration near the $3625cm^{-1}$, coupled with the 825 and $750cm^{-1}$ doublet. The vibration bands related with the H-O-Al and Si-O-Al bonds occur at $1030cm^{-1}$ and 500 to $700cm^{-1}$, respectively. Based on paragonite content of the sericite, the formation temperature of the Narim gold deposit is calculated to be $220{\pm}10^{\circ}C$.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.168-174
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• 2011

Various La-based perovskite catalysts were prepared by a Pechini method, and they were applied to the low-temperature oxidation of odor compounds exhausted from waste food treatment process for effective deodorization. Quantitative and qualitative analyses of exhausted gas were conducted to measure the amount of major odor compounds with respect to operation time. A standard odor sample composed of major odor compounds was then prepared for use as a feed for oxidation reaction system. Various transition metal(M)-substituted La-based perovskite catalysts ($LaMO_{3}$: M=Cr, Mn, Fe, Co, and Ni) were prepared and applied to the oxidation of odor compounds in order to investigate the $LaNiO_3$ catalyst showed the best catalytic performance. Pt-substituted perovskite catalysts ($LaNi_{1-x}Pt_{x}O_{3}$: x=0, 0.03, 0.1, and 0.3) were then prepared for enhancing the catalytic performance. It was found that $LaNi_{0.9}Pt_{0.1}O_{3}$ catalyst served as the most efficient catalyst. Supported perovskite catalysts ($XLaNi_{0.9}Pt_{0.1}O_{3}/Al_{2}O_{3}$: X=perovskite content(wt%), 0, 10, 20, 30, 40, 50, and 100) were finally applied for the purpose of maximizing the catalytic performance of perovskite catalyst in the low-temperature oxidation reaction. Catalytic performance of $XLaNi_{0.9}Pt_{0.1}O_{3}/Al_{2}O_{3}$ catalysts showed a volcano-shaped curve with respect to perovskite content. Among the catalysts tested, $20LaNi_{0.9}Pt_{0.1}O_{3}$/$Al_{2}O_{3}$ catalyst exhibited the highest conversion of odor compounds of 88.7% at $180^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.409-414
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• 1999

The influence of ion beam energy and reactive oxygen partial pressure on the electrical and crystallographic characteristics of transition metal oxide compound(Cr0x) film was studied in this paper. Chromium oxide films were prepared onto the coverglass using Ion Beam Sputter Deposition(1BSD) technique according to the processing conditions of the partial pressure of reactive oxygen gas and ion beam energy. Crystallinity and grain size of as-deposited films were analyzed using XRD analysis. Thickness and Resistivity of the films were measured by $\alpha$-step and 4-point probe measurement. As results, according to the XRD, XPS and resistivity measurement, the deposited films were the cermet type films which has a crystal structure including amorphous oxide(a-oxide) phase and metal Cr phase simultaneously. The increasernent of the ion b m energy during the deposition process happened to decreasernent of metal Cr grain size and the rapid change of resistivity above the critical $O_2$ partial pressure.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.8
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• pp.459-467
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• 2016

In order to assess the pollution status and distribution characteristics of PM and PM-bound species, PM10 samples were collected using mini-volume air sampler at the subway cabin in Daejeon city. Measurements of about 24 elements including toxic metals (e.g., As, Cr, Mn, V, Zn) in PM10 were made by instrumental neutron activation analysis and X-ray fluorescence. The average PM10 concentration was $59.3{\pm}14.5{\mu}g/m^3$ in the subway cabin with a range of 42.2 to $97.4{\mu}g/m^3$, while the associated elemental concentrations were varied in the range of $10^{-3}$ to $10^5ng/m^3$. It was found that the concentration of Fe ($12.5{\mu}g/m^3$) was substantially higher than any other element. The Fe concentration was apportioned by about 20% of the PM10 concentration. The results of factor analysis indicate that there are no more than six sources in the cabin (e.g., brake-nonferrous metal particle, resuspended rail dust, fuel combustion, vehicle exhaust, black carbon, Cr-related).

• Journal of Welding and Joining
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• v.2 no.1
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• pp.41-48
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• 1984

Recrystallization technique was applied to analyze plastic strain at the notch tip of coarse grain HAZ in mild steel (SB 41) and high strength steel (SA 588). The notch tip of specimen was deformed by three point bending. Accumulated displacement (Crack Opening Displacement ${delta}t$) by the monotonic and cyclic loading under room temperature and hot strain embrittlement temperature ($250^{\circ}C$) was 0~1.0mm. Recrystallization heat treatment conditions were $650^{circ}C{ imes}3hr$ for SB 41 and $700^{circ}C{ imes}3hr$ for SA 588. The experimental results obtained were as follows ; 1) Distribution of the effective plastic strain at plastic zone was appeared by the function of crack opening displacement, and plastic zone or the effective plastic strain increased with crack opening displacement. 2) Plastic strain at notch tip of HAZ due to accumulated hot strain calculated as follows. .epsilon. over bar $_{p}$ = .epsilon. over bar $_{cr}$ (x/ $R_{x}$ ) $^{m}$ (m=0.25) 3) Work hardending ratio of notch tip for hot strain was linearly increased with .epsilon. over bar $_{max}$ and dependent upon the material types.s.

• Korean Journal of Materials Research
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• v.5 no.1
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• pp.112-122
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• 1995

Metal hydride alloys of TiFe based system have been produced by mechanical alloying(MA) method and their electrochemical characteristics have been evaluated for application for Ni/MH battery electrode. These alloys became amorphous after 36hrs ball milling and easily activated electrochemically. All MA amorphous alloys reached at the first charge/discharge cycle the maximum capacity which was 2-3 times higher than the crystalline state. But their cyclic lives were much inferior to the crystalline state. Alloying elements such as Ni, Co, Cr, Mo substituting Fe greatly improved the capacity and 180 mAh/g capacity was obtained in an alloy of TiFe_{0.6}Ni_{0.1}Co_{0.1}Cr_{0.1}Mo_{0.1}$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.6
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• pp.425-433
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• 2000

The stochiometric mix of evaporating materials for the $CuGaTe_2$single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuGaTe_2$polycrystal, it was found tetragonal structure whose lattice constant $a_0 and c_0$ were 6.025 $\AA$ and 11.931 $\AA$, respectively. To obtain the single crystal thin films, $CuGaTe_2$mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were $670^{\circ}C$ and $410^{\circ}C$ respectively, and the thickness of the single crystal thin films is 2.1$\mu\textrm{m}$. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility dependence on temperature. The carrier density and mobility of $CuGaTe_2$single crystal thin films deduced from Hall data are $8.72{\times}10{23}$개 $\textrm m^3$, $3.42{\times}10^{-2}$ $\textrm m^2$/V.s at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c-axis of the $CuGaTe_2$single crystal thin film, we have found that the values of spin orbit coupling $\Delta$s.o and the crystal field splitting $\Delta$cr were 0.0791 eV and 0.2463 eV at 10 K, respectively. From the PL spectra at 10 K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0470 eV and the dissipation energy of the donor-bound exciton and acceptor-bound exciton to be 0.0490 eV, 0.0558 eV, respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.110-110
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• 2018

여러 니켈합금 중 인코넬 600은 원전 가압경수로(PWR)의 튜브 재료로 널리 사용되는 재료이다. 스테인리스강과 비교하여 우수한 내식성과 기계적 특성으로 인해 화학설비, 발전설비, 그리고 해양설비 등과 같은 여러 산업분야에서도 널리 사용되고 있다. 그러나 가압경수로용 증기 발생기의 튜브 재료와 같은 특수 환경에서 예민화에 따른 입계부식 및 입계응력부식 등의 문제가 흔히 보고되고 있다. 이러한 내구성 문제는 설비 및 장비의 수명, 내구성 그리고 안정성 등의 치명적인 영향을 미친다. 따라서 용접, 열처리, 그리고 가공과정에서 발생하는 Inconel 600의 예민화 및 입계부식에 관한 연구가 활발히 진행되고 있다. 그러나 100시간 이상 장시간 열화된 시편에 대한 예민화 연구는 전무한 실정이다. 본 연구에서는 장시간 열화된 Inconel 600의 예민화를 평가하기 위해 최대 1,000시간까지 열화를 실시하였으며, 이에 대한 평가방법으로 Double-Loop Electrochemical Potentiokinetic Reactivation(DL-EPR) 시험법을 적용하였다. 본 실험에서 사용된 인코넬 600의 화학성분(wt, %)은 0.01 C, 0.05 Si, 0.14 Mn, 15.3 Cr, 0.5 Cu, 0.015 S, 그리고 나머지는 Ni 이다. 예민화 평가를 위한 등온 열화는 전기열처리로를 이용하여, $550^{\circ}C$와 $650^{\circ}C$에서 최대 1000시간까지 실시하였다. 열화에 따른 미세조직 변화는 scanning electron microscope와 energy dispersive x-ray spectroscopy를 이용하여 실시하였다. DL-EPR 실험은 $25^{\circ}C$의 0.1M $H_2SO_4$ + 0.001M KSCN(potasium thiocyanate) 수용액 하에서 실시하였으며, 분극은 OCP로부터 600 mV(SSE vs.)까지 1.67mV/s 주사속도로 forward scan을 실시 후, 동일한 속도로 OCP까지 reverse scan을 실시하였다. Degree Of Sensitization(DOS)값은 anodic scan peak($I_a$) 값과 reverse scan peak($I_r$) 값의 비로 산출하였다. $$i.e.\;DOS=I_r/I_a{\times}100$$. 그 결과, 온도 변수에 따른 Inconel 600강의 예민화 거동은 서로 상이한 경향을 나타내었다. $550^{\circ}C$의 경우, 열화가 진행됨에 따라 DOS값은 급격하게 증가하는 경향을 나타냈다. 반면, $650^{\circ}C$에서는 일정시간 이후부터 Cr 확산 현상에 의한 탈 예민화 현상이 관찰되었다.

• Imaging Science in Dentistry
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• v.40 no.4
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• pp.165-169
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• 2010

Purpose : To survey the radiographic examination protocol for lateral cephalometric radiographic examinations and to measure their patient doses in Korea and to compare the dose according to the size of hospital, the type of image receptor system, and the installation duration. Materials and Methods : The radiographic examination protocols (kVp, mA, and exposure time) for lateral cephalometric radiography were surveyed with 61 cephalometric radiographic equipments and their patient dose-area product (DAP) measured with a DAP meter (DIAMENTOR M4-KDK, PTW, Freiburg, Germany) for 51 cephalometric radiographic equipments. The radiographic examination protocols and patient doses were compared according to the size of hospital (university dental hospital, dental hospital, and dental clinic), the type of image receptor system (film-based, DR and CR type) and the installation duration, respectively. SPSS 12.0.1 for Windows (SPSS Inc., Chicago, USA) was used for independent t-test and ANOVA test. Results : The average protocols were 77.0 kVp, 12.7 mA, 6.2 second for cephalometric radiography. The average patient dose (DAP) was $128.0mGy\;cm^2$ and 3rd quartile dose (DAP) $161.1mGy\;cm^2$ for cephalometric radiography for adult male. There was no statistically significant difference at average patient DAP according to the size of hospital, the type of image receptor system, and the installation duration, repectively. Conclusion : The average patient dose was $128.0mGy\;cm^2$ and the third quartile patient dose $161.1mGy\;cm^2$ for lateral cephalometric radiography for adult male in Korea.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.100-100
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• 2016

물리기상증착방법 (Physical vapor deposition)에 의하여 합성된 천이금속 질화물 박막은 경도, 내마모성 등 절삭공구의 성능을 향상시키며, Ti-Al-N, Ti-Zr-N, Zr-Al-N, Cr-Si-N 등의 3원계 경질 박막에 대한 연구가 지속적으로 이루어지고 있다. 이중에서도 CrAlN 코팅은 높은 경도, 낮은 표면 조도 등의 우수한 기계적 특성 이외에 고온에서 안정한 합금상 형성으로 인하여 우수한 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, 코팅에 적합한 중간층을 합성함으로써 공구 코팅으로의 적용 가능성을 높이는 연구들이 진행되고 있다. 본 연구에서는 CrAlN 코팅의 물성을 향상시키기 위해 CrAlN 코팅과 WC-Co 6wt.% 모재 사이에 CrN, CrZrN, CrN/CrZrSiN 등의 다양한 중간층을 합성하였으며, 중간층을 포함한 모든 코팅의 두께는 $3{\mu}m$ 로 제어하였다. 합성된 코팅의 미세조직, 경도 및 탄성계수, 내모성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, ball-on-disk 마모시험기 및 ${\alpha}-step$을 사용하였다. 코팅의 내열성을 확인하기 위해 코팅을 furnace에 넣어 공기중에서 500, 600, 700, 800, 900, $1,000^{\circ}C$로 30분 동안 annealing 한 후에 nano-indentation을 사용하여 경도를 측정하였다. CrAlN 코팅을 나노 인덴테이션으로 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, 코팅의 마찰계수는 중간층의 종류에 따라 다른 값을 보였으며, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅의 마찰계수는 0.34로 CrZrN 중간층을 증착한 CrAlN 코팅의 마찰계수(0.41)에 비해 낮은 값을 보였다. 또한, 코팅의 마모율 및 마모폭도 비슷한 경향을 보인 것으로 보아, CrN/CrZrSiN 중간층을 합성한 CrAlN 코팅의 내마모성이 상대적으로 우수한 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 ratio 는 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. 모든 코팅을 열처리 후 경도 분석결과, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅은 $1,000^{\circ}C$까지 약 28GPa의 높은 경도를 유지한 것으로 확인 되었고, 이는 CrZrSiN 중간층 내에 존재하는 $SiN_x$ 비정질상의 우수한 내산화성에 의한 결과로 판단된다.