• The Korean Journal of Ecology
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• v.18 no.1
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• pp.147-156
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• 1995

Restoration of ecosystems degraded by heavy metal pollution can be accomplished by soil amendment and selection and utilization of plants tolerant to heavy metals. Two former zinc mine sites, Sambo Mine in Hwasung, Kyonggi-do and the Second Yonhwa Mine in Samchuk, Kangwon-do, were selected for collection of plant samples and for determination of heavy metal tolerant species. Dominant species on mine waste deposits in Hwasung site were Panicum bisulcatum and Echinoch/oa crus-galli, while those in Samchuk site were Aster yomena, Setaria viridis, Artemisia lavandulaefolia and Oenothera odorata. Mean contents of zinc, lead and cadmium in Hwasung soil were 103, 117 and 1 ppm, respectively, while those in Samchuk soil were 23, 6 and 4 ppm, respectively, Zinc contents were higher in Echinochloa crus-galli from Hwasung and in Artemisia lavandulaefolia from Samchuk, while lead contents were higher in Panicum bisulcatum and Echinochloa crus-galli from Hwasung and Lactuca sonchiJolia and Pinus densiJolia from Samchuk. Plant species with higher cadmium contents were Panicum bisulcatum and Lactuca sonchiJolia. Comparison of metal contents between roots and shoots showed that Echinochloa crus-galli was a zinc accumulator, while Panicum bisulcatum, Persicaria hydroPiPer, Pinus densiJlora and Lactuca sonchiJolia were zinc excluders. In addition, Panicum bisulcatum and Persicaria hydroPiPer were proved to be lead excluders. When both heavy metal contents in plant tissues and biomass of individual plants are considered, it can be concluded that Echinochloa crus-galli and Panicum bisulcatum from Hwasung and Artemisia lavandulaefolia and Aster yomena are heavy metal absorbing plants. The effect of heavy metals on seed germination showed that Artemisia princeps var. orientalis had higher germination rates, but no significant difference in concomitant decrease of germination rates among the species investigated were found by increasing heavy metal contents.

• Journal of the Korean institute of surface engineering
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• v.19 no.3
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• pp.121-127
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• 1986

There are many plating methods already commercially employed in te surface technology. One of the plating methods is electroless (chemical) plating, which is deposited by auto-catalytic reduction of metallic ion with the reducing agent in the plating bath. And it has many advantages comparing with electrolytic plating in respect of properties of deposit, such as corrosion resistance, wear resistance, uniformity, hardness, adhesion and so on. So, electroless plating is the fatest growing process in metallization of plastic and electronic industry. The properties and numerous applications of electroless deposits are attracting more and more attention from finish specifies. Many metal finishers are considering set-up of new electroless line in their shops. This review will be beneficial to domestic metal finishers to understand the real status of present electroless plating technology. It will also provide some knowledge on the economic aspect of electroless plating for the commercial application of specific parts.

• Economic and Environmental Geology
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• v.28 no.1
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• pp.9-17
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• 1995

The Kamkye Cu-Pb-Zn-Au-Ag deposits occur as quartz veins that filled fault-related fractures of NW system developed in the Cretaceous Gyeongsang basin. Three major stages of mineral deposition are recognized: (1) the stage I associated with wall rock alteration, such as sericite, chlorite, epidote and pyrite, (2) the early stage II of base-metal mineralization such as pyrite, hematite, and small amounts of sphalerite and chalcopyrite. and the middle to late stage II of Cu-As-Sb-Au-Ag-S mineralization, such as sphalerite, chalcopyrite, galena with tetrahedrite, tennantite, pearceite, Pb-Bi-Cu-S system, argentite and electrum. (3) the stage III of supergene mineralization, such as covellite, chalcocite and malachite. K-Ar dating of alteration sericite is a late Cretaceous ($74.0{\pm}1.6Ma$) and it may be associated with granitic activity of nearby biotite granite and quartz porphyry. Fluid inclusion data suggest a complex history of boiling, cooling and dilution of ore fluids. Stage II mineralization occurred at temperatures between 370 to $220^{\circ}C$ from fluids with salinities of 8.4 to 0.9 wt.% NaCl. Early stage II($320^{\circ}C$, 2.0 wt.% NaCl) may be boiled due to repeated fracturing which opened up the hydrothermal system to the land surface, and which resulted in a base-metal sulfide. Whilst the fractures were opened to the surface, mixing of middle-late stage II ore fluids with meteoric waters resulted in deposition of Cu-As-Sb-Au-Ag minerals from low temperature fluids(${\leq}290^{\circ}C$). Boiling of ore fluids may be occured at a pressure of 112 bar and a depth of 412 m. Equilibrium thermodynamic interpretation of sphalerite-tetraherite assemblages in middle stage II indicates that the ore-forming fluid had log fugacities of $S_2$ of -6.6~-9.4 atm.

• Economic and Environmental Geology
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• v.20 no.2
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• pp.97-106
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• 1987

The geology of the Bupyeong mine area is consisted of Precambrian Gyeonggi gneiss complex and Mesozoic igneous rocks; i.e., pyroclastic rocks, intrusive breccia, granite and felsic porphyries which were formed during a Jurassic to early Cretaceous resurgent caldera evolution. Granites are not observed on the surface and in the underground of the mine. Bupyeong silver deposits occur as stockworks of base metal sulfides- minor silver minerals-quartz - carbonate veinlets, hosted by pyroclastic rocks and intrusive breccia at the southwestern margin of the caldera. Silver occurs mainly as native silver, and other silver minerals, minor in quantity, are argentite, tetrahedrite-freibergite, pyrargyrite, polybasite, canfieldite and dyscrasite. The average grade of silver ore is about 180g/t Ag. Discrimination of silver ore from the country rocks depends largely on the chemical analyses of rock samples taken every two meters from tunnels, diamond-drilling cores and mining stopes, because silver minerals are hardly observed in the ore by crude eye, and silver orebodies do not properly coincide with the concentrated zone of base metal sulfides which were precipitated at the earlier stage than the stage of precipitation of native silver. General characteristics of the loci of the silver orebodies are as follows; (1) The host rocks of orebodies are pyroclastic rocks and intrusive breccia. (2) Many of the orebodies are distributed around Gyeonggi gneiss complex. Especially where the paleotopography of gneiss complex shows a gradual slope, the basal stratigraphic horizon of the pyroclastic rocks unconformably overlying the gneiss complex offered a favorable loci of high grade ore. (3) $N5^{\circ}W$ to $N15^{\circ}$ E-striking faults played an important role in the localization of the orebodies. (4) Conduits of intrusive breccia within the gneiss complex, through which the intrusive breccia intruded into the upper pyroclastic rocks, exist beneath most of the main orebodies. This suggests that the conduits of intrusive breccia served as channelways for the migration of ore fluids.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.12-17
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• 2013

Nanocrystalline nickel (Ni) tick films were synthesized by direct current electrodeposition at current density from 1 to $30mA/cm^2$ and pH = 4. The basic composition of the bath, which was prepared by dissolving Ni metal particles in HCl, was 0.2M Ni ions. The effects of the current density on the average grain size of Ni deposits were investigated by XRD and SEM techniques. The results showed that the surface roughness was decreased as the saccharin addition was increased up to 2 g/l. The experimental results showed that the increase in the current density had a considerable effect on the average grain size of the Ni deposits. The perpendicular magnetization was raised as the thickness of coating layer was increased.

• Economic and Environmental Geology
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• v.18 no.3
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• pp.225-237
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• 1985

Mineralization of Daehwa and Donsan W-Mo deposits can be devided into three distinct depositional stages on the basis of mineral paragenesis and flnid inclusion studies; stage I, deposition of oxides and silicates ; stage II, deposition of base-metal sulfides and sulfosalts with carbonates; stage III, deposition of barren calcite and fluorite. Tungsten, molybdenum and tin mineralization occurred in stage I. Fluid inclusion studies reveal that ore fluid of stage I were homogeneous $H_2O-CO_2$ fluids containing 3.5~14.6 mol % $CO_2$. Minimum temperature and pressure of stage I ore fluids were $240^{\circ}C$ and 500 bars respectively. Salinities of aqueous type I inclusions in minerals of stage I range from 3.7 to 7.6 wt. % equi. NaCl. whereas those of $CO_2$-containing type III inclusions range from 0.3 to 4.4 wt. %. Temperatures of stage II ore fluids range from 200 to $305^{\circ}C$ on the whole and salinities were in the range of 3.2~7.2 wt. %. Homogenization temperatures of fluid inclusions in calcite and fluorite of stage III range from 114 to $186^{\circ}C$ and salinities were in the range of 0.9~4.3 wt. %. Sulfur fugacities during stage II deduced from mineral assemblages and tamperature data from fluid inclusions declined from earlier to later in the range of $10^{-11}{\sim}10^{-18}atm$. Fluid inclusion evidences suggest that the dominance of $CO_2$ in ore fluid during W-Mo mineralization is the characteristic features of Cretaceous W-Mo deposits of central district of Korea compared to those of Kyeongsang basin district.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2017.05a
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• pp.83-83
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• 2017

Electrorefining is a key step in pyroprocessing. The electrorefining process is generally composed of two recovery steps - the deposit of uranium onto a solid cathode and the recovery of the remaining uranium and TRU elements simultaneously by a liquid cadmium cathode. The solid cathode processing is necessary to separate the salt from the cathode since the uranium deposit in a solid cathode contains electrolyte salt. Distillation process was employed for the cathode processing. It is very important to increase the throughput of the salt separation system due to the high uranium content of spent nuclear fuel and high salt fraction of uranium dendrites. In this study, a mesh-covered crucible was investigated for the sat distillation of electrorefiner uranium deposits. A liquid salt separation step and a vacuum distillation step were combined for salt separation. The adhered salt in uranium deposits was efficiently removed in the mesh-covered crucible. The salt distiller was operated simply since repeated cooling - heating step was not necessary for the change of the crucible. The operation time could be reduced by the use of the mesh-covered crucible and the combined operation of the two steps. A method to preserve a vacuum level was proposed by double O-rings during the operation of the distiller with the mesh-covered crucible. After the salt distillation, the salt content was measured and was below 0.1wt% after the salt distillation. The residual salt after the salt distillation can be removed further during melting of uranium metal.

• Economic and Environmental Geology
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• v.22 no.2
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• pp.103-115
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• 1989

The Tongyoung deposits are epithermal gold and silver bearing quartz-rhodochrosite vein type deposits of late Cretaceous. They occurs in the andesite and tuff breccia member called Gyeongsang basin. Four mineralizations can be distinguished at the mine based on macrostructures. From earlist stage to lastest stage they are: stage I, base-metal quartz vein; stage II, rhodochrosite vein (IIA) and Pb-Zn vein (IIB); stage III, barren quartz vein; stage IV, calcite-ankeritic rhodochrosite veins. Gold and silver mineralizations occur predominantly in the stage I and IIB. Electrum is closely associated with galena, sphalerite and pyrite, and has chemical compositions of 50.98-64.05 atom % Ag. Sphalerite contains 2.09-5.05 mol % FeS and 0.34-2.01 mol % MnS in the stage I, and 2.01-3.41 mol % FeS and 0.21-2.80 mol % MnS in the stage IIB. The FeS and MnS contents are in general correlated, and shows a characteristic zonal arrangement of electrum. It reveals rhat FeS contents of sphalerite which precipitated before electrum, gradually decreases in a grain during its deposition ranging from about 3.3 to 2 mol %. It may be considered from the above data that an increase of $fs_2$ caused by the oxidation of ore forming fluid is more important that the decrease of temperature.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.632-638
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• 2002

Electron beam (EB) and Gas tungsten arc (TIG) welds were performed on 12.7 mm thick Ti-6Al-4V plate (ASTM Titanium Grade 5). Charpy-V toughness and hardness, as well as, microstructure of the welds and penetration from the macrostructure were studied. It appears that by EB welding rather smaller $\beta$-grains than with TIG welding can be obtained. Next to the fusion line the $\beta$-grain size in the HAZ was 50 ${\mu}{\textrm}{m}$l while in the weld metal it was 150 ${\mu}{\textrm}{m}$. Charpy-V toughness of the EB weld metal was equal or even better to that of base metal, which shows that the $\alpha$-martensite per se is not particularly brittle if only the grain size is fine enough. This is similar to behavior of low carbon martensite in steel. The grain size was studied with light optical and scanning electron (SEM) microscopes. Thus for products, for products which can be manufactured automatically with very narrow fit, the EB welding of Ti-6Al-4V appears to yield satisfactory toughness without any complex post weld heat treatment. ill this study as in earlier studies the TIG welds gave lower toughness than that of the base material due to the higher heat input and slower cooling as compared to EB welding.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2073-2080
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• 2013

In this study the effects of adding alkaline-earth (IIA) metal oxides to NiZr-loaded Zeolite Y catalysts were investigated on hydrogen rich production by ethanol steam reforming (ESR). Four kinds of alkaline-earth metal (Mg, Ca, Sr, or Ba) oxides of 3.0% by weight were loaded between the $Ni_6Zr_4O_{14}$ main catalytic species and the microporous Zeolite Y support. The characterizations of these catalysts were examined by XRD, TEM, $H_2$-TPR, $NH_3$-TPD, and XPS. Catalytic performances during ESR were found to depend on the basicity of the added alkaline-earth metal oxides and $H_2$ production and ethanol conversion were maximized to 82% and 98% respectively in 27($Ni_6Zr_4O_{14}$)3MgO/70Zeolite Y catalyst at $600^{\circ}C$. Many carbon deposits and carbon nano fibers were seen on the surface of $30Ni_6Zr_4O_{14}$/70Zeolite Y catalyst but lesser amounts were observed on alkaline-earth metal oxide-loaded 27($Ni_6Zr_4O_{14}$)3MO/70Zeolite Y catalysts in TEM photos after ESR. This study demonstrates that hydrogen yields from ESR are closely related to the acidities of catalysts and that alkaline-earth metal oxides reduce the acidities of 27($Ni_6Zr_4O_{14}$)3MO/70Zeolite Y catalysts and promote hydrogen evolution by preventing progression to hydrocarbons.