• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.53-54
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• 2018

U/RE was electrochemically recovered to LCC at $50mA/cm^2$ from LiCl-KCl salt containing $0.5wt%UCl_3$, $0.22wt%NdCl_3$, 0.15wt%$CeCl_3$ and $0.07wt%LaCl_3$. The Cd in the LCC deposit was removed during the distillation using Cd distiller. U/RE product of 107g obtained from the distiller was installed to TG and then heated to $1200^{\circ}C$ to be consolidated. Dense U/RE metal ingot was not acquired through the consolidation process because U/RE product had been partially already oxidized during the distillation process.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.30.1-30.1
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• 2011

Silicon is one of useful materials in various industry such as semiconductor, solar cell, and secondary battery. The metallic silicon produces generally melting process for ingot type or chemical vapor deposition (CVD) for thin film type. However, these methods have disadvantages of high cost, complicated process, and consumption of much energy. Electrodeposition has been known as a powerful synthesis method for obtaining metallic species by relatively simple operation with current and voltage control. Unfortunately, the electrodeposition of the silicon is impossible in aqueous electrolyte solution due to its low oxidation-reduction equilibrium potential. Ionic liquids are simply defined as ionic melts with a melting point below $100^{\circ}C$. Characteristics of the ionic liquids are high ionic conductivities, low vapour pressures, chemical stability, and wide electrochemical windows. The ionic liquids enable the electrochemically active elements, such as silicon, titanium, and aluminum, to be reduced to their metallic states without vigorous hydrogen gas evolution. In this study, the electrodeposion of silicon has been investigated in ionic liquid of 1-butyl-3-methylpyrolidinium bis (trifluoromethylsulfonyl) imide ([bmpy]$Tf_2N$) saturated with $SiCl_4$ at room temperature. Also, the effect of electrode materials on the electrodeposition and morphological characteristics of the silicon electrodeposited were analyzed The silicon electrodeposited on gold substrate was composed of the metallic Si with single crystalline size between 100~200nm. The silicon content by XPS analysis was detected in 31.3 wt% and the others were oxygen, gold, and carbon. The oxygen was detected much in edge area of th electrode due to $SiO_2$ from a partial oxidation of the metallic Si.

• Korean Journal of Metals and Materials
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• v.50 no.7
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• pp.503-509
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• 2012

We report on the feasibility of producing 6xxx series Al alloy sheets using a combination of twin-roll strip casting and asymmetric rolling. The Al alloy sheets produced in this study exhibited an excellent formability ($\bar{r}=1.2$, ${\Delta}r=0.17$) and mechanical properties (${\sigma}_{TS}{\sim}260MPa$, ${\varepsilon}>30%$), which cannot be feasibly obtained via the conventional technique based on ingot casting and conventional rolling. The enhanced formability as evaluated in terms of $\bar{r}$ and ${\Delta}r$ was clarified by examining the evolution of textures associated with strip casting and subsequent thermo-mechanical treatments. The evaluation of the formability leads us to conclude that the combined technique based on strip casting and asymmetric rolling is a feasible process for enhancing the formability of Al alloy sheets to a level beyond which the conventional technique can reach.

• Journal of Conservation Science
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• v.35 no.6
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• pp.631-640
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• 2019

The purpose of this study was to compare analytical results of sand iron bars reproduced by the traditional iron-making method through a destructive analysis and a non-destructive analysis. For these studies, we produced two types of samples. One was sample(SI-A), a part of the sand iron bar for destructive analysis. The other was SI-B(9 ㎠) for non-destructive analysis. A metallurgical microscope and scanning electron microscope were used for the destructive analysis, and neutron imaging analysis with the Hokkaido University Neutron Source (HUNS) at Hokkaido University, Japan, was used for the non-destructive analysis. The results obtained by destructive analysis showed that there was ferrite and pearlite of fine crystallite size, and some of these showed Widmanstätten ferrite microstructure grown within the pearlite and coarse ferrite at the edge of the specimen. The results from the neutron imaging analysis showed that there was also ferrite and pearlite with 3 ㎛ α-Fe of BCC structure. Based on these results, neutron imaging analysis is capable of identifying material characteristics without destroying the object and obtaining optimal research results when applying it to objects of cultural heritage.

• Nuclear Engineering and Technology
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• v.40 no.6
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• pp.497-504
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• 2008

In a study of the optimum operational condition for a melting decontamination, the effects of the basicity, slag type and slag composition on the distribution of depleted uranium were investigated for radioactively contaminated metallic wastes of iron-based metals such as stainless steel (SUS 304L) in a direct current graphite arc furnace. Most of the depleted uranium was easily moved into the slag from the radioactive metal waste. The partitioning ratio of the depleted uranium was influenced by the amount of added slag former and the slag basicity. The composition of the slag former used to capture contaminants such as depleted uranium during the melt decontamination process generally consists of silica ($SiO_2$), calcium oxide (CaO) and aluminum oxide ($Al_2O_3$). Furthermore, calcium fluoride ($CaF_2$), magnesium oxide (MgO), and ferric oxide ($Fe_2O_3$) were added to increase the slag fluidity and oxidative potential. The partitioning ratio of the depleted uranium was increased as the amount of slag former was increased. Up to 97% of the depleted uranium was captured between the ingot phase and the slag phase. The partitioning ratio of the uranium was considerably dependent on the basicity and composition of the slag. The optimum condition for the removal of the depleted uranium was a basicity level of about 1.5. The partitioning ratio of uranium was high, exceeding $5.5{\times}10^3$. The slag formers containing calcium fluoride ($CaF_2$) and a high amount of silica proved to be more effective for a melt decontamination of stainless steel wastes contaminated with depleted uranium.

• 보존과학연구
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• s.27
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• pp.165-180
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• 2006

The research was conducted to understand type of iron used by those who lived at dwelling site of Yangsoo-ri in between the first century B.C. and the first century A.D. to make steel products and their technique such as steel making process and heat treatment, based on micro structure information obtained through microscopic metallographic structure analysis with SEM-EDS of six steel productsexhumed at the site. Key findings are summarized as below. In the sense that Si-Ca-Al style and less than 0.5% of Ti were found in the non-metallic inclusion, the material used for forged iron ware was magnetite resolved in that. It is, however, unclear whether magnetite was resolved at high temperature or at low temperature. Microscopic structure analysis revealed that forged steel products were made through repeated hot working, the technique of molding by hitting after heating in the process of resolving and molding iron. As a result, the iron used here for the products was not the iron ore which was produced through resolution from discarded cast iron axe, ingot iron. It is probable that to make those steel products, disposed-of cast iron was reused after being molded by decarburizing. Although a few of relics were analyzed for the research, they were of critical importance in defining the process of ironware production from the first century B.C. and the first century A.D. at the Yangsoo-ri region. Judging from the iron from A-19 dwellingsite, it is possible to conclude that the iron was manufactured from cast iron decarburized and yet more research has to be done into relics yetto be exhumed in order to ascertain the finding. All of these findings are believed to play a critical role in further studies to define the steel-manufacturing technique used on the central Korean peninsular in the ancient times.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.4
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• pp.121-127
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• 2022

β-Gallium oxide (Ga₂O₃), an ultra-wide bandgap semiconductor, has attracted great attention due to its promising applications for high voltage power devices. The most stable phase among five different polytypes, β-Ga₂O₃ has the wider bandgap of 4.9 eV and higher breakdown electric field of 8 MV/cm. Furthermore, it can be grown from melt source, implying higher growth rate and lower fabrication cost than other wide bandgap semiconductors such as SiC, GaN and diamond for the power device applications. In this study, β-Ga₂O₃ bulk crystals were grown by the edge-defined film-fed growth (EFG) process. The growth direction and the principal surface were set to be the [010] direction and the (100) plane of the β-Ga₂O₃ crystal, respectively. The spectra measured by Raman an alysis could exhibit the crystal phase an d impurity dopin g in the β-Ga₂O₃ ingot, and the crystallinity quality and crystal direction were analyzed using high-resolution X-ray diffraction (HRXRD). The crystal quality and various properties of as-grown β-Ga₂O₃ ribbon was systematically analyzed in order to investigate the spatial variation in entire crystal grown by EFG method.