• 한국대기환경학회지
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• 제33권4호
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• pp.411-423
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• 2017

The spacial potential source contribution function (PSCF) method was utilized by considering topography and height of back trajectories based on the measurement of organic typo matter (OM), $NO_3{^-}$, $SO{_4}^{2-}$, and $NH_4{^+}$ at the Baegryungdo Super Site ($37^{\circ}57^{\prime}N$, $124^{\circ}37^{\prime}E$, 135 m a.s.l. (above sea level)) for three selected periods (i.e., January~April, May~August, and September~December) in 2013. The PSCF were calculated on the contributions of trans-boundary transport to the hourly mean concentrations using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). The cluster analysis using back trajectories was performed to identify the major airflows to the sampling site. The upper atmosphere in the Tianjin area of China and the lower atmosphere in the western coast area of Korea can be the major source of trans-boundary pollution to the sampling site during January~April resulted from PSCF. The area in Lianyungang-city and Liaoning-sheng, China can be responsibile for the nitrogen related secondary compounds during May~August, and Shandong Peninsula in China is the major source area during September~December. In addition, relationships between the cluster analysis of back trajectories and PSCF were investigated for the statistically significance level for the source areas.

• 한국광물학회지
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• 제17권1호
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• pp.37-47
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• 2004

대구광역시에 위치한 달성광산의 폐광석과 하천수에 형성된 황산염 광물인 명반석과 슈베르트마나이트의 특징과 수질변화를 통하여 산화환경하에서의 환경지구화학적 의미를 고찰하였다. 산성광산배수는 하류로 갈수록 pH가 감소하는 특징을 보이는데, 이는 슈베르트마나이트의 형성에 크게 영향을 받는다. Al광물들의 침전작용에 의하여 하천수로부터 Al이 제거되는데, 그 중에서 가장 중요한 Al-황산염광물인 명반석은 Al의 가수분해 상수인 $pK_1$ 이상의 높은 pH환경에서 잘 형성된다. 명반석은 SEM하에서 뚜렷한 구상의 결정체로서 슈베르트마나이트와 수반되고, 높은 포화지수를 나타낸다. 지표환경에 노출된 폐금속광석에서는 산화작용으로 인하여 다양한 이차광물이 기존의 광물표면에 성장하거나, 피복 되어 있다. 명반석은 특징적으로 구형, 싸리버섯 같은 정벽(botrytis-like habit), 또는 방사상의 결정집합체로 나타난다. 또한, natroalunite를 수반하거나, 이 둘의 물리적 혼합체(mixture)를 형성한다. 본 산성광산배수의 유해성분들이 하천을 따라 다소 저감되기는 하나, 슈베르트마나이트가 지속적으로 형성되므로 하류로 갈수록 pH가 감소한다. 그러므로 하상침천물은 쉽게 다시 용해될 수 있다. 따라서, 본 AMD에서 자연저감효과는 미미하며, 여전히 잠재적인 위해 요소를 가지고 있다.

• 마이크로전자및패키징학회지
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• 제8권1호
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• pp.27-32
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• 2001

($Zr_{0.8}, Sn_{0.2})TiO_4$의 소결온도를 저하시키고 품질계수 향상의 목적으로 첨가한 $V_2O_5$가 다른 donor형태의 화합물과 달리 품질계수의 저하를 가져오는 원인을 $Ta_2O_5$가 첨가된 ($Zr_{0.8}, Sn_{0.2})TiO_4$와 미세 구조변화, 전기전도도, 산화상태의 관점에서 비교 분석하였다. 일반적으로 donor형태의 화합물의 첨가는 ($Zr_{0.8}, Sn_{0.2})TiO_4$의 산소공공의 농도를 감소시켜 품질계수의 증가를 가져오는 것으로 알려져 있다. $V_2O_5$의 첨가의 경우는 액상소결에 의한 결정입계상 존재, 섬유상 형태의 $V_2O_5-TiO_2$rich 이차상 형성 및 Vanadium 이온의 산화상태 불안정에서 기인된 산소공공의 농도 증가가 복합적으로 ($Zr_{0.8}, Sn_{0.2})TiO_4$의 품질계수 저하 요인으로 작용하였다.

• 한국환경과학회지
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• 제27권4호
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• pp.241-250
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• 2018

The objective of this study was to estimate air quality trends in the study area by surveying monthly and seasonal concentration trends. To do this, the mass concentration of $PM_{10}$ samples and the metals, ions, and total carbon in the $PM_{10}$ were analyzed. The mean concentration of $PM_{10}$ was $33.9{\mu}g/m^3$. The composition of $PM_{10}$ was 39.2% ionic species, 5.1% metallic species, and 26.6% carbonic species (EC and OC). Ionic species, especially sulfate, ammonium, and nitrate, were the most abundant in the $PM_{10}$ and had a high correlation coefficient with $PM_{10}$. Seasonal variation of $PM_{10}$ showed a similar pattern to those of ionic and metallic species. with high concentration during the winter and spring seasons. $PM_{10}$ showed high correlation with the ionic species $NO_3{^-}$ and $NH_4{^+}$. In addition, $NH_4{^+}$ was highly correlated with $SO{_4}^{2-}$ and $NO_3{^-}$. We obtained four factors through factor analysis and determined the pollution sources using the United States Environmental Protection Agency(U.S. EPA) pollution profile. The first factor accounted for 51.1% of $PM_{10}$ from complex sources, that is, soil, motor vehicles, and secondary particles: the second factor indicated marine sources; the third factor, industry-related sources; and the last factor, heating-related sources. However, the pollution profile used in this study may be somewhat different from the actual situation in Korea because it was from US EPA. Therefore, to more accurately estimate the pollutants present, it is necessary to create a pollution profile for Korea.

• 한국대기환경학회지
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• 제25권4호
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• pp.275-288
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• 2009

The Korean government strengthened the environmental polices to manage and enhance Metropolitan Area air quality, and also has enforced "Special Act on Seoul Metropolitan Air Quality Improvement (SASMAQI)" issued in Dec. 2004. Recently government expanded the Seoul Metropolitan Air Quality Management District (SMAQMD) to the outskirts satellite cities of Seoul area through the "Revised Law Draft of SASMAQI". The SMAQMD has been alloted the allowable emission loads to the local governments on the basis of the carrying $PM_{10}$ capacity. However, in order to establish the effective air quality control strategy for $PM_{10}$, it is necessary to understand the corresponding sources which have a potential to directly impact ambient $PM_{10}$ concentration. To deal with the situations, many receptor methodologies have been developed to identify the origins of pollutants and to determine the contributions of sources of interests. The objective of this study was to extensively identify $PM_{10}$ sources and to estimate their contributions at the metropolitan area. $PM_{10}$ samples were simultaneously collected at the 3 semi-industrialized local cities in the Seoul metropolitan area such as Hwasung-si, Paju-si, and Icheon-si sites from April 15 to May 31, 2007. The samples collected on the teflon membrane filter by one $PM_{10}$ cyclone sampler were analyzed for trace metals and soluble ions and samples on the quartz fiber filter by another sampler were analyzed for OC and EC. Source apportionment study was then performed by using a positive matrix factorization (PMF) receptor model. A total of 6 sources were identified and their contributions were estimated in each monitoring site. Contribution results on Hwasung, Paju, and Icheon sites were as follows: 33%, 27%, and 27% from soil source, 26%, 26%, and 21% from secondary aerosol source, 11%, 11%, and 12% from biomass burning, 12%, 6%, and 5% from sea salt, 7%, 15%, and 19% from industrial related source, and finally 11%, 15%, and 16% from mobile and oil complex source, respectively. This study provides information on the major sources affecting air quality in the receptor sites and thus it will help to manage the ambient air quality in the metropolitan area by establishing reasonable control strategies, especially for the anthropogenic emission sources.

• 대한화학회지
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• 제50권4호
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• pp.315-320
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• 2006

도핑된 망간 산화물을 저온 산화환원반응을 통하여 합성하였다. 분말X선 회절분석 결과는 황이 도핑된 화합물이 층상 birnessite 구조로, 그리고 셀레늄 도핑 시료는 터널 -MnO2 구조로 결정화 되어 있음을 나타낸다. 이와 대조적으로 텔루륨이 도핑된 시료는 비정질상으로 잘 발달된 회절 피크를 보이지 않는다. EDS분석으로부터 칼코겐 원소가 망간 산화물 격자 내에 망간원소에 대해 4-7%의 농도로 도핑되었음을 확인하였다. 이들 물질을 이루는 구성원소의 화학결합상태를 X선 흡수 분광분석법 (XAS)을 이용하여 조사하였다. Mn K-흡수단 XAS 결과로부터 +3/+4가 혼합 원자가 상태를 가지는 망간 이온이 산소 팔면체 자리에 안정화 되어 있다는 사실을 확인하였다. Se K-와Te L1-흡수단 XAS 분석 결과는 중성인 Se과 Te 원소가 산화제인 KMnO4와의 반응을 통해 +6가 양이온으로 산화되었음을 보여준다. 결정구조와 망간의 산화상태를 감안하면 이들이 리튬 이차전지용 전극물질로서 응용 가능할 것으로 기대된다.

• 한국자기학회지
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• 제19권3호
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• pp.113-119
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• 2009

sol-gel 방법을 이용하여 제작된 $^{57}Fe_xCu_{1-x}O$(x = 0.0, 0.02) 분말 시료들에 대한 결정구조 및 초미세 자기적 특성을 X-선 회절(XRD)과 $M{\ddot{o}}ssbauer$ 분광법을 이용하여 조사하였다. XRD 측정 결과 단사(monoclinic) 구조의 CuO 단일상 만이 나타났고, 열처리 온도 상승에 따라 격자상수 값들은 소폭 증가하였다. 또한, 열처리 온도 증가에 따라 $Fe^{3+}$ 스핀들의 정렬과 관련되는 산소 vacancy 농도가 증가하며, 이에 따라 상온에서의 강자성 상의 세기가 증가되었다. Jahn-Teller 효과에 의하여 왜곡된 팔면체 자리에 위치하는 $^{57}Fe$ 이온에 대하여 CuO의 Neel 온도보다 매우 낮은 17 K에서 사중극자 상호작용과 초미세 자기장 상호작용이 동시에 작용하는 조건을 적용하여 분석한 결과, 초미세 자기장 방향은 전기장 기울기 텐서의 세 주축에 대하여 ${\theta}=65^{\circ}$, ${\phi}=0^{\circ}$이고, 비대칭인자 ${\eta}=0.6$으로 나타났다. 그리고 Jahn-Teller 효과에 의한 왜곡으로 비교적 큰 사중극자 분열 ${\Delta}E_Q=-3.67\;mm/s$ 값이 나타났으며, 이성질체 이동 값은 $Fe^{3+}$에 대한 값인 0.32 mm/s으로 얻어졌다. $500^{\circ}C$에서 열처리를 통하여 얻어진 $^{57}Fe_{0.02}Cu_{0.98}O$ 시료에 대하여 17 K에서 취한 $H_{hf}$ 값은 426.94 kOe로 비교적 작은 값으로 얻어졌는데, 이것은 $H_{hf}$에 관계되는 세가지 항 $H_L$, $H_d$, $H_c$ 사이의 온도 의존성 차이에 기인하는 것으로 해석된다.

• 한국환경과학회지
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• 제27권7호
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• pp.597-610
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• 2018

This study observed particulate matter ($PM_{2.5}$ and $PM_{10}$) in the downtown area of Jeju City, South Korea, to understand the chemical composition of particulates based on an analysis of the water-soluble ionic species contained in the particles. The mass fraction of the ionic species in the sampled $PM_{10}$ and $PM_{2.5}$ was 44.3% and 42.2%, respectively. In contrast, in Daegu City and Suwon City, the mass fraction of the ionic species in $PM_{2.5}$ was higher than that in $PM_{10}$. The chloride depletion percentage of $PM_{10}$ and $PM_{2.5}$ in Jeju City was higher than 61% and 66%, respectively. The contribution of sea-salt to the mass of $PM_{10}$ (5.9%) and $PM_{2.5}$ (2.6%) in Jeju City was similar to that in several coastal regions of South Korea. The mass ratio of $Cl^-$ to $Na^+$ in the downtown area of Jeju City was comparable to that in some coastal regions, such as the Gosan Area of Jeju Island, Deokjeok Island, and Taean City. The mass fraction of sea-salt in $PM_{10}$ and $PM_{2.5}$ was very low, and the concentration of sodium and chloride ions in $PM_{10}$ was not correlated with those in $PM_{2.5}$ ($R^2$ < 0.2), suggesting that the effects of sea-salt on the formation of particulate matter in Jeju City might be insignificant. The relationship between $NH_4{^+}$ and several anions such as $SO_4{^{2-}}$, $NO_3{^-}$, and $Cl^-$, as well as the relationship between the measurement and calculation of ammonium ion concentration, suggested that sea-salts may not react with $H_2SO_4$, and $(NH_4)_2SO_4$ may be a major secondary inorganic aerosol component of $PM_{2.5}$ and $PM_{10}$ in Jeju City.

• 전기화학회지
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• 제18권4호
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• pp.143-149
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• 2015

Planetary ball mill과 고상반응법을 사용하여 실리케이트계 탄소 코팅된 $Li_2MnSiO_4$ 양극활물질 분말을 합성하였으며 충방전 특성을 조사하였다. 전기화학적 활성을 지니는 ${\beta}-Li_2MnSiO_4$ 상을 형성하기 위하여 하소 온도와 분위기를 조절하였으며 ${\beta}-Li_2MnSiO_4$ 단일상에 가까운 탄소 코팅된 $Li_2MnSiO_4$ 활물질 분말을 제조할 수 있었다. 합성된 분말은 100 nm 정도 크기의 1차 입자가 뭉쳐있는 2차 입자 형태를 보였다. $Li_2MnSiO_4$ 활물질에서 Li의 삽입/탈리가 가능하려면 탄소의 첨가가 필요하였으며, 4.8 wt%의 탄소가 코팅된 $Li_2MnSiO_4$ 활물질에서 초기용량 192 mAh/g를 얻을 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제21권11호
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• pp.1125-1132
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• 2000

The pH effect of the precursor solution on the preparation of $LiCoO_2$ by a solution phase reaction containing malonic acid was carried out. Layered $LiCoO_2$ powders were obtained with the precursors prepared at the different pHs (4, 7, and 9) and heat-treated at $700^{\circ}C(LiCoO_2-700)$ or $850^{\circ}C(LiCoO_2-850)$ in air. pHs of the media for precursor synthesis affects the charge/discharge and electrochemical properties of the $LiCoO_2electrodes.$ Upon irrespective of pH of the precursor media, X-ray diffraction spectra recorded for $LiCoO_2-850$ powder showed higher peak intensity ratio of I(003)/I(104) than that of $LiCoO_2-700$, since the better crystallization of the former crystallized better. However, $LiCoO_2$ synthesized at pH 4 displayed an abnormal higher intensity ratio of I(003)/I(104) than those synthesized at pH 7 and 9. The surface morphology of the $LiCoO_2-850$ powders was rougher and more irregular than that of $LiCoO_2-700$ made from the precursor synthesized at pH 7 and 9. The $LiCoO_2electrodes$ prepared with the precursors synthesized at pH 7 and 9 showed a better electrochemical and charge/discharge characteristics. From the AC impedance spectroscopic experiments for the electrode made from the precursor prepared in pH 7, the chemical diffusivity of Li ions (DLi+) in $Li0.58CoO_2determined$ was 2.7 ${\times}$10-8 $cm^2s-1$. A cell composed of the $LiCoO_2-700$ cathode prepared in pH 7 with Lithium metal anode reveals an initial discharge specific capacity of 119.8 mAhg-1 at a current density of 10.0 mAg-1 between 3.5 V and 4.3 V. The full-cell composed with $LiCoO_2-700$ cathode prepared in pH 7 and the Mesocarbon Pitch-based Carbon Fiber (MPCF) anode separated by a Cellgard 2400 membrane showed a good cycleability. In addition, it was operated over 100 charge/discharge cycles and displayed an average reversible capacity of nearly 130 mAhg-1.