• Transactions of the Korean hydrogen and new energy society
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• v.25 no.3
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• pp.247-254
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• 2014

The synthesis of Fischer-Tropsch oil is the catalytic hydrogenation of CO to give a range of products, which can be used for the production of high-quality diesel fuel, gasoline and linear chemicals. Our cobalt based catalyst was prepared Co/alumina, silica and titania by the incipient wet impregnation of the nitrates of cobalt and promoter with supports. Cobalt catalysts was calcined at $350^{\circ}C$ before being loaded into the FT reactors. After the reduction of catalyst has been carried out under $450^{\circ}C$ for 24hrs, FT reaction of the catalyst has been carried out at GHSV of 4,000/hr under $200^{\circ}C$ and 20atm. From these test results, we have obtained the results as following ; in case of 12wt% Co-supported $Al_2O_3$, $SiO_2$ and $TiO_2$ catalysts, maximum activities of the catalysts were appeared at the promoters of Mn, Mo and Ce respectively. The activity of 12wt% $Co/Al_2O_3$ added a Mn promoter was about 3 times as high as that of 12wt% $Co/Al_2O_3$ catalyst without promoters. When it has been the experiment at the range of reaction temperature of $200{\sim}220^{\circ}C$ and GHSV of 1,546~5,000/hr, the results have shown generally increasing the activities with the increase of reaction temperature and GHSV.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.2
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• pp.153-168
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• 2022

Petrological and mineralogical analyses were conducted to identify minerals containing radioactive elements (uranium) in the Chiaksan gneiss complex and to confirm their association with the surrounding groundwater. Fourteen minerals were identified through the microscopic and electron microscopy (SEMEDS) investigation. The principal minerals included plagioclase, biotite, quartz, alkali feldspar, chlorite, and calcite. Minor minerals were sphene, allanite, apatite, zircon, thorite, titanite, pyrite, and galena. A small amount of thorite was observed in the size of ~1 mm within macrocrystalline allanite. Allanite, which includes a large amount of rare earth elements, appeared in three distinctive patterns. The results of the EPMA analyses indicated that macrocrystalline allanite had higher elemental contents of TiO₂~1.70 wt.%, Ce₂O₃~11.86 wt.%, FeO ~13.31 wt.%, MgO ~0.90 wt.% and ThO₂ ~1.06 wt.% with the lowest average content of Al₂O₃ 17.35 ± 2.15 wt.% (n = 7), CaO 12.13 ± 1.81 wt.% (n = 7). An allanite existing at the edge of the sphenes encompassing titanites had a higher element content of Al₂O₃ ~24.00 wt.%, Nd₂O₃ ~5.10 wt.%, Sm₂O₃~0.66 wt.%, Dy₂O₃~0.86 wt.% and Y₂O₃~1.38 wt.% with the lowest average content of TiO₂ 0.35 ± 0.21 wt.% (n = 11), Ce₂O₃ 5.25 ± 1.03 wt.% (n = 11), FeO 9.84 ± 0.26 wt.% (n = 11), MgO 0.12 ± 0.05 wt.% (n = 11), and La₂O₃ 1.49 ± 0.29 wt.% (n = 11). Allanites in a matrix of parental rocks exhibited intermediate values between the two elemental compositions mentioned above. None of the uranium-rich minerals were observed in the migmatitic gneiss within the study area. Consequently, the origin of uranium in the groundwater was not associated with the geology of the surrounding environment, but our investigation proved the existence of abundant allanites containing significant amounts of radioactive thorium and rare earth elements.

• Journal of Powder Materials
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• v.20 no.1
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• pp.37-42
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• 2013

$YAG:Ce^{3+}$ phosphor powders were synthesized using a $Al_2O_3$ seed (average particle size: 5 ${\mu}m$) by the polymer solution route. PVA solution was added to the sol precursors consisting of the seed powder and metal nitrate salts for homogeneous mixing in atomic scale. All dried precursor gels were calcined at $500^{\circ}C$ and then heated at $1400^{\circ}C{\sim}1500^{\circ}C$ in $N_2/H_2$ atmosphere. The final powders were characterized by using XRD, SEM, PSA, PL and PKG test. All synthesized powders were crystallized to YAG phase without intermediate phases of YAM or YAP. The phosphor properties and morphologies of the synthesized powders were strongly dependent on the PVA content. Finally, the synthesized $YAG:Ce^{3+}$ phosphor powder heated at $1500^{\circ}C$, which is prepared from 12:1 PVA content and has an average particle size of 15 ${\mu}m$, showed similar phosphor properties to a commercial phosphor powder.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.212-217
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• 2021

The applicability of the white LED from the blue LED of the coating film as a binder for surface and curved coatings were confirmed. The particle size of YAG is D₅₀: 9~10 ㎛, and the crystal structure is garnet (Y₃Al₅O₁₂), cubic. The coating film had no cracks, at the same time, the silica sol was uniformly coated with YAG phosphor, and the YAG content and thickness in the coating film showed a tendency to increase up to 40 ㎛ in proportion to the increase in the amount added. Furthermore, as the YAG content increased, the PL emission intensity increased and the color coordinate shift toward the end of the chromatic locus curve was confirmed.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.329-342
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• 2006

The purpose of this study is to determine the geochemical characteristics for the stream sediments in the Konyang area. So we can estimate the environment contamination and understand geochemical disaster. We collect the stream sediments samples by wet sieving along the primary channels and slowly dry the collected samples in the laboratory and grind to pass a 200mesh using an alumina mortar and pestle for chemical analysis. Mineralogy, major, trace and rare earth elements are determined by XRD, XRE, ICP-AES and NAA analysis methods. For geochemical characteristics on the geological groups of stream sediments, the studied area was grouped into quartz porphyry area, sedimentary rock area, anorthosite area and gneiss area. Contents of major elements for the stream sediments in the Konyang area were $SiO_2\;41.86{\sim}76.74\;wt.%,\;Al_{2}O_{3}\;9.92{\sim}30.00\;wt.%,\;Fe_{2}O_{3}\;2.74{\sim}12.68\;wt.%,\;CaO\;0.22{\sim}3.31\;wt.%,\;MgO\;0.34{\sim}3.97\;wt.%,\;K_{2}O\;0.75{\sim}0.93\;wt.%,\;Na_{2}O\;0.25{\sim}1.92\;wt.%,\;TiO_{2}\;0.40{\sim}3.00\;wt.%,\;MnO\;0.03{\sim}0.21\;wt.%,\;P_{2}O_{5}\;0.05{\sim}0.38\;wt.%$. The contents of trace and rare earth elements for the stream sediments were $Cu\;7{\sim}102\;ppm,\;Pb\;15{\sim}47\;ppm,\;Sr\;48{\sim}513\;ppm,\;V\;29{\sim}129\;ppm,\;Zr\;31{\sim}217\;ppm,\;Li\;14{\sim}94\;ppm,\;Co\;5.6{\sim}32.1\;ppm,\;Cr\;23{\sim}259\;ppm,\;Cs\;1.7{\sim}8.7\;ppm,\;Hf\;2.1{\sim}109.0\;ppm,\;Rb\;34{\sim}247\;ppm,\;Sc\;4.5{\sim}21.9\;ppm,\;Zn\;24{\sim}609\;ppm,\;Sb\;0.8{\sim}2.6\;ppm,\;Th\;3{\sim}213\;ppm,\;Ce\;22{\sim}1000\;ppm,\;Eu\;0.7{\sim}5.3\;ppm,\;Yb\;0.6{\sim}6.4\;ppm$. Generally, the contents of $Al_{2}O_{3}\;and\;SiO_2$ had a good relationships with each other in rocks but it had a bad relationships in stream sediments for this study area. The contents of $Fe_{2}O_3$, CaO, MnO and $P_{2}O_{5}$ had a good relationships with major and minor elements in stream sediments of this study area. The contents of Co and V in the stream sediments had a good relationships with other toxic elements.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.39-53
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• 2001

Environmental pollution of the Tohyun mine creek area was investigated on the basis of geology, mineralogy and geochemistry. In soils and sediments of the mine area, ${Al_2}{O_3}/{Na_2O}$ and ${K_2}O/{Na_2}O$ ratios are partly negative correlation against ${SiO_2}/{Al_2}{O_3}$, respectively. Geochemical characteristics of some trace and rare earth elements such as V/Ni, Ni/Co, La/Ce, Th/Yb, Th/U, La/Th, ${La_N}/{Yb_N}$, La/Sc and Sc/Th are revealed a narrow range and homogeneous compositions may be explained by simple source lithology. These results suggest that sediments source of the host shale around the mine area could be originated by basic to intermediate igneous rocks. Mineral compositions of soil and sediment near the mine area were partly variable mineralogy, which are composed of quartz, mica, feldspar, chlorite, clay minerals and some pyrite. Soils and sediments with highly concentrated heavy minerals, gravity separated mineralogy, are composed of some pyrite, arsenopyrite, chalcopyrite, sphalerite, galena, goethite and various kinds of hydroxide minerals on the polished sections. As normalized by bed rock composition, average enrichment indices of major elements in sediments, precipitates, farmland soils and paddy soils are 1.0, 1.7, 0.9 and 0.8, respectively. Maximum concentration of environmental toxic elements in the mine creek are detected with Ag = 186 ppm, As = 17,100 ppm, Bi = ]27 ppm, Cd = 77 ppm, Cu = 12,299 ppm, Pb = 8,897 ppm, Sb = 1,350 ppm, W = 599 ppm and Zn = 12,250 ppm, which are increasing with total FeO increasing, and extremely high concentrations of surface sediments and precipitates near the waste rock dump. These toxic elements (As, Bi, Cd, Cu, Pb, Sb, W and Zn) of the samples, normalizing by host rock concentration, revealed that average enrichment index is 106.0 for sediments, 279.6 for precipitates, 3.5 for farmland soils and 1.6 for paddy soils. However, on the basis of EPA values, enrichment indices of all the samples are 40.7, 121.4, 1.3 and 0.6, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.18-21
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• 2017

In this study, spherical monodispersed cerium-doped yttrium aluminum garnet (YAG : $Ce^{3+}$) phosphor particles were synthesized via homogeneous precipitation method using the mixed solution of yttrium nitrate, cerium nitrate, aluminum nitrate, ammonium aluminum sulfate, and urea as a precipitant. During the process of precursors of monodispersed YAG : $Ce^{3+}$, aluminum ions which form spherical aluminum compounds precipitated first and yttrium compounds precipitated onto the surface of the existing spherical aluminum compounds. Drying process using lyophilization could obtain monodispered spherical YAG : $Ce^{3+}$ particles compare to using oven. The thermal calcination process of YAG : $Ce^{3+}$ precursors under the temperature of $1200^{\circ}C$ for 6 h was enough to obtain 400~500 nm sized YAG particles with pure YAG phase.

• Economic and Environmental Geology
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• v.30 no.5
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• pp.417-431
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• 1997

Characteristics of sedimentary rocks and enrichment of toxic elements in shale and coal from the Chungnam coal field were investigated based upon geochemistry of major, trace and rare earth elements. Shale and coal of the area are interbedded along the Traissic to the Jurassic Daedong Supergroup, which can be subdivided into grey shale, black shale and coal. The coal had been mined, however all the mines are abandonded due to the economic problems. The shale and coal are characterized by relatively low contents of $SiO_2$, and $Al_2O_3$ and high levels of loss-on-ignition (LOI), CaO and $Na_2O$ in comparison with the North American Shale Composite (NASC). Light rare earth elements (La, Ce, Yb and Lu) are highly enriched with the coal. Ratios of $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ in shale and coal range from 30.0 to 351.8 and from 4.2 to 106.8, which have partly negative correlations against $SiO_2/Al_2O_3$ (1.24 to 6.06), respectively. Those are suggested that controls of mineral compositions in shale and coal can be due to substitution and migration of those elements by diagenesis and metamorphism. Shale and coal of the area may be deposited in terrestrial basin deduced from high C/S (39 to 895) and variable composition of organic carbon (0.39 to 18.40 wt.%) and low contents of reduced sulfur (0.01 to 0.05 wt.%). These shale and coal were originated from the high grade metamorphic and/or igneous rocks, and the rare earth elements of those rocks are slightly influenced with diagenesis and metamorphism on the basis of $Al_2O_3$ versus La, La against Ce, Zr versus Yb, the ratios of La/Ce (0.38 to 0.85) and Th/U (3.6 to 14.6). Characteristics of trace and rare earth elements as Co/Th (0.07 to 0.86), La/Sc (0.31 to 11.05), Se/Th (0.28 to 1.06), V/Ni (1.14 to 3.97), Cr/V (1.4 to 28.3), Ni/Co (2.12 to 8.00) and Zr/Hf (22.6~45.1) in the shale and coal argue for inefficient mixing of the simple source lithologies during sedimentation. These rocks also show much variation in $La_N/Yb_N$ (1.36 to 21.68), Th/Yb (3.5 to 20.0) and La/Th (0.31 to 7.89), and their origin is explained by derivation from a mixture of mainly acidic igneous and metamorphic rocks. Average concentrations in the shale and coal are As=7.2 and 7.5, Ba=913 and 974, Cr=500 and 145, Cu=20 and 26, Ni=38 and 35, Pb=30 and 36, and Zn=77 and 92 ppm, respectively, which are similar to those in the NASC. Average enrichment indices for major elements in the shale (0.79) and coal (0.77) are lower than those in the NASC. In addition, average enrichment index for rare earth elements in coal (2.39) is enriched rather than the shale (1.55). On the basis of the NASC, concentrations of minor and/or environmental toxic elements in the shale and coal were depleted of all the elements examined, excepting Cr, Pb, Rb and Th. Average enrichment indices of trace and/or potentially toxic elements (As, Cr, Cu, Ni, Pb, U and Zn) are 1.23 to 1.24 for shale and 1.06 to 1.22 for coal, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.396.2-396.2
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• 2014

백색 유기발광소자는 전색 디스플레이, 조명으로서의 잠재적인 특성으로 차세대 디스플레이 소자 기술로 많은 주목을 받고 있다. 백색 유기발광소자는 주로 R-G-B 영역의 다양한 발광층을 적층하여 제작한다. 하지만 여러 발광층을 적층해야하기 때문에 제작할 때 공정 과정이 복잡해지고, 높은 생산단가를 가지게 된다. 이런 문제를 해결하기 위해 형광체를 이용한 백색 유기발광소자의 연구가 진행되고 있지만, 아직 색순도와 색좌표에 대한 많은 연구가 미흡한 상태이다. 본 연구에서는 무기물 형광체를 활용하여 백색 유기발광소자의 전기적 특성과 광학적 특성을 관찰하였고, 광원으로 사용된 청색 유기발광소자에 녹색과 적색의 무기물 형광체를 결합하는 방법으로 백색 유기발광소자를 제작하였다. 광원으로 사용한 청색 유기발광 소자는 투명전극으로 ITO를 사용하였고, 정공 수송층으로 N,N'-bis-(1-naphthyl)-N,N'-diphenylbenzidine, 발광층으로 4,4-bis(2,2-diphenylethen-1-yl)biphenyl, 정공 저지 층과 전자 수송 층은 각각 bathocuproine 과 4,7-diphenyl-1,10-phenanthroline 을 사용 하였다. 전자 주입 층으로는 lithium quinolate를 사용하였으며 음극으로는 Al을 사용하였다. 색 변환 층으로 사용된 유기물 형광체는 sol-gel 방법으로 제작된 녹색 형광체 Y3Al5O12:Ce, 적색 형광체 Ca2AiO19:Mn 을 사용하였다. Sol-gel 방법으로 제작된 형광체는 X선 회절 분석기를 통해 JCPDS cards를 확인하였고, 형광체의 녹색과 적색의 혼합비율에 따른 색좌표를 확인하여 백색 유기발광소자를 제작 하였다.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.481-492
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• 2005

The purpose of this study is to determine geochemical characteristics for stream sediments in the Gwangju area. We collect the stream sediments samples by wet sieving along the primary channels and dry these samples slowly in the laboratory and grind to under 200mesh using an alumina mortar fur chemical analysis. Major elements, trace and rare earth elements are determined by XRF, ICP-AES and NAA analysis methods. For geochemical characteristics on geological groups of stream sediments, we separate geologic groups which are derived from Precambrian granite gneiss area, Jurassic granite area and Cretaceous Hwasun andesite area. Contents range of major elements for stream sediments in the Gwangju area are $SiO_2\;51.89\~70.63\;wt.\%,\;Al_2O-3\;12.91\~21.95\;wt.\%,\;Fe_2O_3\;3.22\~9.89\;wt.\%,\;K_2O\;1.85\~4.49\;wt.\%,\;MgO\;0.68\~2.90\;wt.\%,\;Na_2O\;0.48\~2.34\;wt.\%,\;CaO\;0.42\~6.72\;wt.\%,\;TiO_2\;0.53\~l.32\;wt.\%,\;P_2O_5\;0.06\~0.51\;wt.\%\;and\;MnO\;0.05\~0.69\;wt.\%.$ According to the AMF diagram for stream sediments and rocks, the stream sediments are plotted on boundary of tholeiitic series and calk alkaline series, which shows that contents of $Fe_2O_3$ are higher in stream sediments than rocks. According to variation diagram of $SiO_2$ versus $(K_2O+Na_2O),$ stream sediments are plotted on subalkaline series. Contents range of trace and rare earth elements for stream sediments in the Gwangiu area are Ba$590\~2170$ppm, Be1\~2.4$ppm, Cu$13\~79$ppm, Nb$20\~34$ppm, Ni$10\~50$ppm, Pb$17\~30$ppm, Sr$70\~1025$ ppm, V$42\~135$ppm, Zr$45\~171$ppm, Li$19\~77$ppm, Co$4.3\~19.3$ppm, Cr$28\~131$ppm, Cs$3.1\~17.6$ppm, Hf$5\~27.6$ppm, Rb$388\~202$ppm, Sb$0.2\~l.2$ ppm, Sc$6.4\~17$ppm, Zn$47\~389$ppm, Pa$8.8\~68.8$ppm, Ce$62\~272$ppm, Eu$1\~2.7$ppm and Yb$0.9\~6$ppm.