• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.312-319
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• 2017

For high value-added applications of natural blue diatomite, the physical refining process and synthesis of SiC from refined diatomite were investigated. Approximately 30 percent Fe ($Fe_2O_3$) in raw blue diatomite was removed by a particle sieve separation process; the Fe composition for 325 mesh down powder was approximately 2 percent. Although a wet and/or dry magnetic separation process had some influence on the separation and/or refining of Fe composition, the Fe composition in the non-magnetic by-product was approximately 2 percent. Water leaching separation was effective in removing the Fe composition; approximately 40 percent of the Fe in raw blue diatomite was removed. The synthesis of ${\beta}$-SiC by a carbothermal reduction of the $SiO_2$ in the refined diatomite using carbon (graphite, carbon black), the effects of an acid-treatment on removing the Fe, and the specific surface area for the synthesized powder were also investigated. The impurities were mostly eliminated and the specific surface area was increased to $52.5m^2/g$.

• Journal of Powder Materials
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• v.10 no.5
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• pp.344-347
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• 2003

Pure tantalum powder has been produced by combining Na as a reducing agent, $K_2$TaF$_{7}$ as feed material, KCl and KF as a diluent in a stainless steel (SUS) bomb, using the method of metallothermic reduction. And we examined various types of after-treatment that affect the high purification of powder. A significant amount of impurities contained in recovered powder was removed in various conditions of acid washing. In particular, 20% (HCl + HNO$_3$) was effective in removing heavy metal impurities such as Fe, Cr and Ni, 8% H$_2$SO$_4$ + 8% $Al_2$(SO$_4$)$_3$ in removing fluorides such as K and F from non-reactive feed material, and 2% $H_2O$$_2$ + 1 % HF in removing oxides that formed during reaction. Significant amounts of oxygen and part of light metal impurities could be removed through deoxidation and heat treatment process. On the other hand, because it is difficult to remove completely heavy metal impurities such as Fe, Cr, and Ni through acid washing or heat treatment process if their contents are too high, it is considered desirable to inhibit these impurities from being mixed during the reduction process as much as possible.

• Transactions of Materials Processing
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• v.10 no.2
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• pp.151-159
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• 2001

Flow defect of a piston-pin for automobile parts is investigated in this study. In combined cold extrusion of piston-pin, lapping defect, which is a kind of flow defect, appears by the dead metal zone. This appearance evidently happens in products with a thin thickness to be pierced for the dimensional accuracy and the decrease of material loss. The flow defect that occurs in piston-pin has bad effects on the strength and the fatigue life of piston-pin. Therefore, it is important to predict and prevent defects in the early stage of process design. The best method that can prevent flow defect is removing or reducing dead metal zone through material flow control. The finite element simulations are applied to analyze the flow defect. This study proposes processes for preventing flow defect by removing dead metal zone. Then the results are compared with the experimental ones for verification. These FE simulation results are in good agreement with the experimental ones.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.155-158
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• 2000

Flow defect of a piston-pin for automobile parts is investigated in this study. In cold forging of piston-pin Lapping defect a kind of flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The finite element simulations are applied to analyze the flow defect. This study proposed processes for preventing flow defect by removing dead metal zone. Then the results are compared with the experiments for verification. These FE simulation results are in good agreement with the experimental ones.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.158-161
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• 2008

It is well known that iron is one of the most common impurity elements found in aluminum and its alloys. Iron in the aluminum forms an intermetallic compounds such as $FeAl_3$. The $FeAl_3$ particles on the aluminum surface are one of the most detrimental phases to the corrosion process and anodizing procedure for aluminum and its alloys. Trial and error surface treatment will be carried out to find the preferential and effective removal of $FeAl_3$ particles on the surfaces without dissolution of aluminum matrix around the particles. One of the preferable surface treatments for the aim of getting $FeAl_3$ free surface was an electrochemical treatment such as cathodic current density of $-2kAm^{-2}$ in a 20-30 mass% $HNO_3$ solution for the period of 300s. The corrosion characteristics of aluminum surface with $FeAl_3$ free particles are examined in a $0.1kmol/m^3$ NaCl solution. It is found that aluminum with free $FeAl_3$ particles shows higher corrosion resistance than aluminum with $FeAl_3$ particles.

• Bulletin of the Korean Chemical Society
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• v.9 no.2
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• pp.87-94
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• 1988

The substitution reaction of Fe$(CO)_5$ by ethylene has been studied for plausible intermediates by means of extended Huckel calculations. Among various reaction mechanisms the favorable reaction pathway is via a dissociative mechanism in which ethylene approaches to Fe$(CO)_4$ unit. For Fe$(CO)_4$ fragment, the square planar conformation is found to be the most stable form by the extended Huckel calculations. Our calculations show that ethylene attacks square planar intermediate formed by removing one carbonyl from Fe$(CO)_5$ and then the unstable species thus formed is distored to the most stable trigonal bipyramid with the ethylene lying in the equatorial plane.

• Journal of the Mineralogical Society of Korea
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• v.27 no.4
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• pp.207-222
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• 2014

In order to recover the metallic copper powder from the mine-waste rock, heap bioleaching, Fe removal and electrowinning experiments were carried out. The results of heap leaching with the mine-waste rock sample containing 0.034% Cu showed that, the leaching rate of Cu were 61% and 62% in the bacteria leaching and sulfuric acid leaching solution, respectively. Sodium hydroxide (NaOH), hydrogen peroxide ($H_2O_2$) and calcium hydroxide ($Ca(OH)_2$) were applied to effectively remov Fe from the heap leaching solution, and then $H_2O_2$ was selected for the most effective removing Fe agent. In order to prepare the electrolytic solution, $H_2O_2$ were again treated in the heap leaching, and Fe removal rates were 99% and 60%, whereas Cu removal rates were 5% and 7% in the bacteria and sulfuric acid leaching solutions, respectively. After electrowinning was examined in these leaching solution, the recovery rates of Cu were obtained 98% in bacteria and obtained 76% in the sulfuric leaching solution. The dendritic form of metallic copper powder was recovered in both leaching solutions.

• Journal of environmental and Sanitary engineering
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• v.15 no.3
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• pp.62-69
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• 2000

In point of recycling wastes, batch test was conducted to examine the neutralization and Fe removal from laboratory wastewater using wastes. Oyster shell and slag had a buffer capacity to neutralize an acidic wastewater but tire rubber didn't. With increasing reaction time, dosage and agitation speed, Fe was well removed by wastes. As a result on the experiments of Freundlich isotherm, the adsorption intensities(1/n) were 0.32∼0.46 and the adsorption capacities(k) were 4.3∼4.6 for removing Fe from laboratory wastewater by wastes. In view of these results, it was estimated that wastes containing the similar compositions as these could utilize the neutralization and adsorption of heavy metals in laboratory wastewater.

• The Korean Journal of Ecology
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• v.26 no.2
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• pp.65-70
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• 2003

Shihwa tidal freshwater marsh was constructed recently to treat pollutants entering Shihwa lake. In this study, we examined the spatial and temporal patterns of heavy metal accumulation in soils of Shihwa marsh and sought correlations between several soil variables (pH, electrical conductivity, organic matter, and acid ammonium oxalate-extractable Fe and Al contents) and the heavy metal concentration of soils. Surface soil samples (0∼20 cm) were collected in June 2000, November 2000, and July 2001, and were analyzed for heavy metals (Zn, Cd, Pb, Cu, Cr, As, and Hg) and soil chemical properties. The neutral pH and water-saturated conditions of Shihwa marsh appeared to favor immobilization of heavy metal through adsorption onto soils. The concentrations of heavy metal (especially Zn, Cu, and Cr) in soils of Shihwa marsh increased along the sampling occasions, suggesting that soils of Shihwa marsh serve as a sink of heavy metal. Among the sub-marshes, metal concentrations were highest in Banweol high marshes and lowest in Samhwa marshes. The temporal and spatial variations in the heavy metal concentrations of soils were correlated positively with organic matter and oxalate extractable Fe and Al contents, but negatively with electrical conductivity. These results suggest that organic matter and hydrous oxide of Fe/Al may playa key role in removing heavy metals in soils of Shihwa marsh, and that heavy metal removing capacity would increase with desalinization. However, the removal patterns of heavy metal by reeds warrant further studies to evaluate the total removal capacity of heavy metals by Shihwa marsh.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.137-140
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• 2007

The ordering of nanopores in AAO has been improved by using laser interference lithography. After growing Fe and Cu on this substrate in vacuum and removing AAO, Fe nanodots are fabricated. The nanopores in AAO and nanodots are ordered in one dimension following the prepatterning. It has been confirmed from the magnetic hysteresis loop that the Fe nanodots have vortex structure and the dipolar interaction is dominant among them.