• Journal of Powder Materials
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• v.19 no.1
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• pp.13-18
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• 2012

This study has been performed on the full density sintering of Fe nanopowder and the surface hardening by plasma ion nitriding. The Fe sintered part was fabricated by pressureless sintering of the Fe nanopowder at $700^{\circ}C$ in which the nanopowder agglomerates were controlled to have 0.5-5 ${\mu}m$ sized agglomerates with 150 nm Fe nanopowders. The green compact with 46% theoretical density(T.D.) showed a homogeneous microstructure with fine pores below 1 ${\mu}m$. After sintering, the powder compact underwent full densification process with above 98%T.D. and uniform nanoscale microstructure. This enhanced sintering is thought to be basically due to the homogeneous microstructure in the green compact in which the large pores are removed by wet-milling. Plasma ion nitriding of the sintered part resulted in the formation of ${\gamma}$'-$Fe_4N$ equilibrium phase with about 12 ${\mu}m$ thickness, leading to the surface hardening of the sintered Fe part. The surface hardness was remarkably increased from 176 $H_v$ for the matrix to 365 $H_v$.

• Proceedings of the Korean Magnestics Society Conference
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• 1991.05a
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• pp.29-30
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• 1991

• Proceedings of the Korean Magnestics Society Conference
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• 2006.11a
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• pp.24-25
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• 2006

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.34.2-34
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• 2000

• Journal of Magnetics
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• v.15 no.4
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• pp.179-184
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• 2010

We have investigated the effects of post annealing on iron oxide nanoparticles synthesized by the novel hydrothermal synthesis method with the $FeSO_4{\cdot}7H_2O$. To investigate the post annealing effect, the as-synthesized iron oxide nanoparticles were annealed at different temperatures in a vacuum chamber. The morphological, structural and magnetic properties of the iron oxide nanoparticles were investigated with high resolution X-ray powder diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Mossbauer spectroscopy, and vibrating sample magnetometer analysis. According to the XRD and HRTEM analysis results, as-synthesized iron oxide nanoparticles were only magnetite ($Fe_3O_4$) phase with face-centered cubic structure but post annealed iron oxide nanoparticles at $700^{\circ}C$ were mainly magnetite phase with trivial maghemite ($\gamma-Fe_2O_3$) phase which was induced in the post annealing treatment. The crystallinity of the iron oxide nanoparticles is enhanced by the post annealing treatment. The particle size of the as-synthesized iron oxide nanoparticles was about 5 nm and the particle shape was almost spherical. But the particle size of the post annealed iron oxide nanoparticles at $700^{\circ}C$ was around 25 nm and the particle shape was spherical and irregular. The as-synthesized iron oxide nanoparticles showed superparamagnetic behavior, but post annealed iron oxide nanoparticles at $700^{\circ}C$ did not show superparamagnetic behavior due to the increase of particle size by post annealing treatment. The saturation of magnetization of the as-synthesized nanoparticles, post annealed nanoparticles at $500^{\circ}C$, and post annealed nanoparticles at $700^{\circ}C$ was found to be 3.7 emu/g, 6.1 emu/g, and 7.5 emu/g, respectively. The much smaller saturation magnetization value than one of bulk magnetite can be attributed to spin disorder and/or spin canting, spin pinning at the nanoparticle surface.

• Journal of the Korean institute of surface engineering
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• v.27 no.1
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• pp.45-53
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• 1994

A kinetic study on the electrodeposition of zinc-iron alloys onto a steel in chloride solutions has been car-ried out using a rotating disc geometry. The results show that the deposition rate was increased with electropotential, disc rotation speed and temperature, and consequently the rate was partly controlled by elec-trochemical reaction and partly by mass transport. The iron content of deposit was more increased with cell voltage than with disc rotating speed and temperature. During electrodeposition process, the addition of metal-lic zinc powder retards oxidation rate of $Fe^{2+}$.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.67-77
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• 2013

To improve the energy efficiency of conventional thermal treatment, soil remediation with microwave has been studied. In this study, the remediation efficiency of contaminated soil with semi-volatile organic contaminants were evaluated with microwave oven and several additives such as water, formic acid, iron powder, sodium hydroxide (NaOH) solution, and activated carbon. For the experiment, loamy sand and sandy loam collected from Imjin river flood plain were intentionally contaminated with hexachlorobenzene and phenanthrene, respectively. The contaminated soils were treated with microwave facility and the mass removals of organic contaminants from soils were evaluated. Among additives that were added to increase the remediation efficiency, activated carbon and NaOH solution were more effective than water, iron powder, and formic acid. When 10 g of hexachlorobenzene (142.4 mg/kg-soil) or phenanthrene (2,138.8 mg/kg-soil) contaminated soil that mixed with 0.5 g iron powder, 0.5 g activated carbon and 1 ml 6.25 M NaOH solution were treated with microwave for 3 minutes, more than 95% of contaminants were removed. The degradation of hexachlorobenzene during microwave treatments with additives was confirmed by the detection of pentachlorobenzene and tetrachlorobenzene. Naphthalene and phenol were also detected as degradation products of phenanthrene during microwave treatment with additives. The results showed that adding a suitable amount of additives for microwave treatments fairly increased the efficiency of removing semi-volatile soil organic contaminants.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.401-404
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• 2010

A spray-type cleaning agent in utilizing dust-remover on PCB was chosen to study. In cleaning of electronic and semiconductor equipment, a substrate(IPC-A-36) was used to test the jet forces of the agent. And according to the jet forces time of the cleaning agent, the corresponding moving distances were compared with the spray times, and for the pollutants of iron powder and dust, the cleaning efficiency was tested with the IPC-A-36 by a weight method. The moving distance increased with the spray cleaning time longer. For a spray cleaning time of 3sec, the cleaning efficiency decreased with the amount of dust and the iron powder. It was also observed that the dust was remarkably removed, compared to the iron powder.

• Korean Journal of Plant Resources
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• v.20 no.4
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• pp.321-324
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• 2007

This study was conducted to evaluate the effects of silicate fertilizer, soil addition and iron powder on yield and quality of rice. High density plot, cropping pattern of rice showed relatively superior values for all the yield components and yield with 83.2cm in culm length, 21.9cm in panicle length, 8.8 in number of panicles, 65.7% in percentage of productive tillers, 23.15g in weight of 1,000 grain of brown rice, 658.7kg/10a in rough rice yield and 544.7kg/10a in brown rice yield. The results indicate that plot of high density, cropping pattern shows different adaptabilities to a particular cropping pattern and high density plot seems to be the most suitable culture method of rice for high yielding.

• Journal of the Korean Ceramic Society
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• v.38 no.5
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• pp.401-404
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• 2001

Barium ferrite powders were synthesized by the coprecipitation method using iron-pickling waste acid (IPWA) and BaCl$_2$$.$2H$_2$O as raw materials. Fe$\^$2+/ ions in the IPWA, which contains both Fe$\^$2+/ and Fe$\^$3+/ ions, were oxidized into Fe$\^$3+/ ions using H$_2$O$_2$. Proper amount of BaCl$_2$$.$2H$_2$O was dissolved into the oxidized IPWA. Using NaOH, Ba$\^$2+/ and Fe$\^$3+/ ions were coprecipitated as Ba(OH)$_2$and Fe(OH)$_3$. The coprecipitated Ba(OH)$_2$and Fe(OH)$_3$were washed and dried. Barium ferrite powders were obtained by calcining the dried Ba(OH)$_2$and Fe(OH)$_3$mixture from 400$\^{C}$ to 1000$\^{C}$ with a 100$\^{C}$ interval. Barium ferrite powders were characterized by X-ray diffraction, SEM, and VSM. It was found that barium ferrite powders could be synthesized at around 630$\^{C}$. The synthesized barium ferrite powders showed hexagonal plate shapes with a fairly uniform size. The barium ferrite powder calcined at 900$\^{C}$ showed good magnetic properties, saturation magnetization of 67emu/g and maximum coercivity of 5000 Oe.