• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.11b
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• pp.300-315
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• 2005

Recently plasma surface-cleaning or surface-etching techniques have been focused in the respect of decontamination of spent or used nuclear parts and equipment. In this study decontamination rate of metallic cobalt surface was experimentally investigated via its surface etching rate with a $CF_4-O_2$ mixed gas plasma and metallic surface wastes of cobalt oxides were simulated and decontaminated with $NF_3$ - Ar mixed gas plasma. Experimental results revealed that a mixed etchant gas with about $80{\%}\;CF_4-20{\%}\;O_2$ gives the highest reaction rate of cobalt disk and the rate reaches with a negative 300 DC bias voltage up to $0.43\;{\mu}m$/min at $380^{\circ}C$ and $20{\%}\;NF_3-80\%$ Ar mixed gas gives $0.2\;{\mu}m$/min of reaction rate of cobalt oxide film.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.77-83
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• 2018

This paper aims to evaluate the results of toxicity testing with Daphnia magna and Vibrio fischeri on wastewater samples which might be influenced by ion imbalance. The effluents from factories were found to be more toxic with high salinity levels than those from public wastewater treatment plant (WTP) and sewage treatment plant (SWP). Clion composition was highest in the effluent, in terms of percentage, which was followed by $Na^+$, $SO_4^{2-}$ and $Ca^{2+}$. $K^+$ and $Mg^{2+}$ ion was relatively low. The sensitivity of D. magna test results was higher than V. fischeri. Among samples which were proved by V. fischeri testing to be nontoxic, the composition ratio of each ion whether toxic samples or nontoxic samples which were decided by D. magna toxicity testing, were compared. $Na^+$, $K^+$, $Ca^{2+}$, $Mg^{2+}$ ion composition ratio showed high level in nontoxic samples whereas $SO_4^{2-}$ and $Cl^-$ ion composition ratio was high in toxic samples. Accordingly, $SO_4^{2-}$ and $Cl^-$ ion seemed to be considered the ions causing toxicity in effluent. Toxicity from some categories of industries (Mining of non-metallic minerals, Manufacture of basic organic petrochemicals, Manufacture of other basic organic chemicals, Manufacture of other chemical products etc.) seemed to be influenced by salinity. The Ion concentration in influent and effluent were similar. Concentration of $Na^+$, $Cl^-$, $K^+$, $Ca^{2+}$ ions were high in influent, however $Mg^{2+}$ and $SO_4^{2-}$ ions were high in effluent.

• Journal of the Korean institute of surface engineering
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• v.38 no.3
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• pp.126-135
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• 2005

SKD 11 steel has been widely used for tools, metallic mold and die for press working because of its favorable mechanical properties such as high toughness and creep strength as well as excellent oxidation resistance. The ion nitrided tool steel containing Mo results in improvement of corrosion resistance, strength at high temperature and pitting resistance, especially in $Cl^-$ contained environment. But the Mo addition causes a disadvantage such as lower oxidation resistance at elevated temperature. In this study, several effects of ion-disadvantage on the oxidation characteristics for SKD 11 steel with various oxidation temperature were investigated. SKD 11 steels were manufactured by using vacuum furnace and solutionized for 1 hr at $1,050^{\circ}C$. Steel surface was ion nitrided at $500^{\circ}C$ for 1 hr and 5 hr by ion nitriding equipment. ion nitrided specimen were investigated by SEM, OM and hardness tester. Oxidation was carried out by using muffle furnace in air at $500^{\circ}C,\;700^{\circ}C\;and\;900^{\circ}C$ for 1hr, respectively. Oxidation behavior of the ion nitrided specimen was investigated by SEM, EDX and surface roughness tester. The conclusions of this study are as follows: It was found that plasma nitriding for 5 hr at $500^{\circ}C$, compared with ion nitriding for 1 hr at $500^{\circ}C$, had a thick nitrided layer and produced a layer with good wear, corrosion resistance and hardness as nitriding time increased. Nitrided SKD 11 alloy for 1hr showed that wear resistance and hardness decreased, whereas surface roughness increased, compared with nitrided SKD 11 alloy for 5 hr. The oxidation surface at $900^{\circ}C$ showed a good corrosion resistance.

• Resources Recycling
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• v.25 no.4
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• pp.42-48
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• 2016

A research for the recovery of the metal with high purity from the waste tin plating solution was carried out. First, tin plating waste solution was tested to remove the organic substances and metallic impurities such as Fe, Zn, Na etc. using ion exchange resin having iminodiacetic functional groups (Lewatit TP 207). Second, the tin solution was purified to obtain the high purity tin solution using ion exchange resin having ethylhexyl-phosphate functional groups (Lewatit VPOC 1026). Finally, 99.98% of the high purity of tin metal can be recovered from the purified solution by cyclone type electrowinning method.

• Journal of the Korean Vacuum Society
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• v.8 no.4B
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• pp.514-518
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• 1999

Gold (Au) is not supposed to react with sapphire(single crystalline ) under thermodynamic equillibrium, therefore, a strong adhesion between these two dissimilar materials is not expected. However, pull test showed that the gold film sputter-deposited onto annealed and pre-sputtered sapphire exhibited very strong adhesion even without post-deposition annealing. Strongly and weakly adhered samples as a result of the pull testing were selected to investigate the adhesion mechanisms with Auger electron spectroscopy. The Au/ interfaces were analyzed using a new technique that probes the interface on the film using Auger electron escape depth. It revealed that one or two monolayers of Au-Al-O compound formed at the Au/Sapphire interface when AES in the UHV chamber. It showed that metallic aluminum was detected on the surface of sapphire substrates after irradiating for 3 min. with 7keV Ar+ -ions. These results agree with TRIM calculations that yield preferential ion-beam etching. It is concluded that the formation of Au-Al-O compound, which is responsible for the strong metal-ceramic bonding, is due to ion-induced cleaning and reduction of the sapphire surface, and the kinetic energy of depositing gold atoms, molecules, and micro-particles as a driving force for the inter-facial reaction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.451-460
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• 1989

This paper dealt with the effect of the ratios N2 to H2 gas on the corrosion fatigue failure behavior of ion-nitrided SM45C steel specimens. The specimens were water cooled after ion-nitriding at 500.deg. C for 3hrs in 5 Torr, 0.8N$_{2}$ and 0.5N$_{2}$ atmospheres. As the nitrogen concentration increases, the higher compressive residual stresses developed in the surface layer and the depth of nitrided layer increased, which in turn gave rise to increases in fatigue strength and corrosion fatigue life. In the region less than 1.5 * 10$^{5}$ cycles, fatigue failure initiated at the brittle nitrided case, whereas in the region higher than 1.5 * 10$^{5}$ cycles crack initiated from the non-metallic inclusions in the subsurface. The initiation of corrosion fatigue failure was mainly attributed to pitting of case hardened surface layer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.29-33
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• 1999

Transition metallic $Cr^{3+}$ ion was diffused in white sapphire {0001}, ${10\bar{1}0}$ crystal plane which were grown by the Verneuil, it enhanced and changed the physical, electrical and optical properties of sapphires. After mixing the metallic oxide and metal powder, it were used for diffusion powder. When it was used the mixing powder of metal and metallic oxide, the dopping was slowly progressed and it needed the longer duration time and higher temperature, relatively. Metallic powder was vapoured under $1{\times}10^{-4}$ torr of vacuum pressure at $2050^{\circ}C$, first step, it were kept by the diffusion condition of 6 atm of $N_{2}$ accelerating pressure at $2050~2150^{\circ}C$. Each surface density of sapphire crystal are 0.2254(c) and $0.1199\;atom/{\AA}^2(a)$. The color of the Cr-doped sapphires was changed to red. Dopping reaction was come out more deep in the plane of ${10\bar{1}0}$ than {0001}. It was speculated that the planar density was one of the factors to determine diffusion effect.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.133-145
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• 2020

Soil in mine waste-rock fields, and at the pithead, sediments and farmlands around an abandoned mine in the Chungcheong Province of South Korea were investigated to assess the distribution of metallic elements and to understand the scope of the pollution. Reddening was observed from the mine up to a distance of 61 m. Losses of waste rock around the mine were assessed over a section of 1800 ㎥. Yellowish precipitates on the bottom of a stream were identified as ferrihydrite and goethite. For anions, a mean sulfate ion level over 773.6 mg/L was found during August in the river water samples. Mine drainage at the site was shown to have a pH of 4.9 and a sulfate concentration of 1557.8 mg/L during the August rainy season. A possible cause of the metallic element contamination in the mine is waste-rock loss, because mine waste-rock is located on the slope in this area. In conclusion, the total soil area to be treated, based on the amount that exceeded the recommended Korean soil pollution levels, was assessed to be 10,297 ㎡.

• Journal of Microbiology and Biotechnology
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• v.20 no.6
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• pp.1018-1021
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• 2010

Metallic and non-metallic isomerases can be used to produce commercially important monosaccharides. To determine which category of isomerase is more suitable as a template for directed evolution to improve enzymes for galactose isomerization, L-arabinose isomerase from Escherichia coli (ECAI; E.C. 5.3.1.4) and tagatose-6-phosphate isomerase from Staphylococcus aureus (SATI; E.C. 5.3.1.26) were chosen as models of a metallic and non-metallic isomerase, respectively. Random mutations were introduced into the genes encoding ECAI and SATI at the same rate, resulting in the generation of 515 mutants of each isomerase. The isomerization activity of each of the mutants toward a non-natural substrate (galactose) was then measured. With an average mutation rate of 0.2 mutations/kb, 47.5% of the mutated ECAIs showed an increase in activity compared with wild-type ECAI, and the remaining 52.5% showed a decrease in activity. Among the mutated SATIs, 58.6% showed an increase in activity, whereas 41.4% showed a decrease in activity. Mutant clones showing a significant change in relative activity were sequenced and specific increases in activity were measured. The maximum increase in activity achieved by mutation of ECAI was 130%, and that for SATI was 190%. Based on these results, the characteristics of the different isomerases are discussed in terms of their usefulness for directed evolution of non-natural substrate isomerization.

• Applied Microscopy
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• v.45 no.4
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• pp.236-241
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• 2015

Carbon-coated Ni, Cu and Sn nanocapsules were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM) and a four-point probe device. All of these nanocapsules were prepared by an arc-discharge method, in which the bulk metals were evaporated under methane ($CH_4$) atmosphere. Three pure metals (Ni, Cu, Sn) were typically diverse in formation of the carbon encapsulated nanoparticles and their different mechanisms were investigated. It was indicated that a thick carbon layers formed on the surface of Ni(C) nanocapsules, whereas a thin shell of carbon with 1~2 layers covered on Cu(C) nanocapsules, and the Sn(C) nanocapsules was, in fact, a longger multi-walled carbon nanotubes partially-filled with metal Sn. As one typical magnetic/dielectric nanocomposite particles, Ni(C) nanocapsules and its counterpart of oxide-coated Ni(O) nanocapsules were compared in the electrically conductive behaviors for further applications as the electromagnetic materials.