• Journal of Korea Foundry Society
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• v.34 no.5
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• pp.156-161
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• 2014

This study is focused on the effect of $Al_2Ca$ as a modifier on eutectic Si modification of A356 alloy. Microstructural observation was carried out for as-cast, as-solution treated and as-aged samples. Solution treatment and aging were performed for 2, 4, 6 and 10 hrs at $540^{\circ}C$ and $170^{\circ}C$, respectively. Although A356 alloy, which $Al_2Ca$ was added, has no significant difference in as-cast phases with normal A356 alloys, it shows much more modified eutectic Si, grain refinement and improved tensile property both in as-cast and as-heat treated conditions. TGA result shows that $Al_2Ca$ added A356 alloy has a certain improvement in oxidation resistance.

• Journal of Integrative Natural Science
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• v.7 no.2
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• pp.130-137
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• 2014

Resins were synthesized by mixing N-phenylaza-15-crown-5 macrocyclic ligand attached to styrene (2th petroleum in 4th class hazardous materials) divinylbenzene (DVB) copolymer with crosslink of 1%, 2%, 6%, and 12% by substitution reaction. The synthesis of these resins was confirmed by content of chlorine, element analysis, thermo gravimetric analysis (TGA), surface area, and IR-spectroscopy. The effects of pH, equilibrium arrival time, dielectric constant of solvent and crosslink on adsorption of metal ions by the synthetic resin adsorbent were investigated. The metal ions were showed fast adsorption on the resins above pH 4. The optimum equilibrium time for adsorption of metallic ions was about two hours. The adsorption selectivity determined in ethanol was in increasing order uranium (VI) > zinc (II) > europium (III) ions. The uranium ion adsorbed in the order of 1%, 2%, 6%, and 12% crosslink resin and adsorption of resin decreased in proportion to the order of dielectric constant of solvents.

• Journal of the Korean Chemical Society
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• v.34 no.2
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• pp.143-158
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• 1990

Metal complexes were prepared by reacting uranium (Ⅵ), thorium (Ⅳ) and rare earth metal (Ⅲ) ions including Nd (Ⅲ), Sm (Ⅲ) and Ho (Ⅲ) with macrocyclic ligands including five crown ethers, nine crownands and one cryptand ligands, and subjected to NMR studies in order to examine coordination sites of the ligands and compositions of the complexes formed. Among the marcocyclic ligands, crown ethers and crownand ligands have shown down-field shifts of the methylene protons of the lcigands by forming stable complexes with all the metal ions and the differences of chemical shifts were decreased as increasing of the cavity-size of crown ethers for the same metal ions and decreasing of the atomic number of the rare earth metals for the same ligands. It has been found that crownand 22 gave a stable complex with uranium(Ⅵ) ion by the coordination through both oxygen and nitrogen atoms of the ligand whereas no complex was formed with the rare earth metal(Ⅲ) ions, which on the other hand were found to form stable complexes with cryptand 221. The rest of the crowand ligands have also been found to form stable complexes with uranium(Ⅵ) ion by coordinating through all the oxygen and nitrogen atoms of the ligands whereas no complexes were formed with the rare earth metal(Ⅲ) ions. It has also been shown by 1H-NMR study that uranium(Ⅵ), thorium(Ⅳ) and rare earth metal(Ⅲ) ions formed 1:1 complexes with the macrocyclic ligands except for thorium(Ⅳ) complex of 12C4 in which the mole ratio of metal to ligand is 1:2. More stable metal complexes show larger changes in chemical shifts of the coordinated ligand protons. Finally, the rare earth metal(Ⅲ) complexes of 18C6 have shown ligand exchange reaction with the solvent molecules in acetylacetone solution, which was not observed for the uranium (Ⅵ) complexes.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.257-261
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• 2001

The separation of rare earths minerals is very difficult because of their similar chemical properties. The rare earth minerals are used as the mixed rare earth minerals or the misch metal without separation to each element. However, the high purity rare earths are recently produced commercially to each element so they there are used as the materials for high tech. Based on the characterization results for the raw minerals, we have developed a combined process containing gravity seperation, magnetic seperation and flotation. The result obtained from this study is monazite concentration of TREO grade 69.11% and Recovery 56.02%.

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.205-207
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• 2001

• Proceedings of the KWS Conference
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• 2001.10a
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• pp.112-115
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• 2001

• Resources Recycling
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• v.22 no.6
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• pp.73-80
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• 2013

Marine mineral resources are classified into submarine and seawater mineral resources. In seawater, huge amounts of useful minerals, such as uranium, lithium, magnesium, aluminum, zinc, iron, silver, copper, vanadium, nickel, titanium and cobalt are present. If the rare metals recovery technology from seawater is developed, the commercialization of the precess will be possible. For the 21st century, countries rich in resoures tend to weaponize the resources, according to the depletion of reserves and quality degradation of metal resources in the land. Therefore, Korea that relies on imports for most of the metal resources, should focus on the research and development of the rare metals recovery technology from seawater by using the geographical characteristics of the country that is on three sea-sides.

• Mineral and Industry
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• v.28
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• pp.45-54
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• 2015

• Mineral and Industry
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• v.28
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• pp.23-37
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• 2015

• Mineral and Industry
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• v.28
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• pp.38-44
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• 2015