• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.244-250
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• 1992

Iron nitride $Fe_4N$ by partial substitution of nitrogen by carbon was prepared by nitriding the iron oxalate whose thermal decomposition gives a carburating atmosphere. Iron oxalates, the precursors, were prepared by precipitation and co-precipitation. The size and shape of the carbonitride particles could be controlled by modifying the conditions of preparation of the oxalate precursor. From the results of electron micrographs, it is clear that the $Fe_4N$ pigment particle maintains the original shape(needle shape) of the starting materials and that it consists of fine unit particles which link together to form a stereo-network structure. An investigation of the $Fe^{II}_3\;Fe^I_{1-x}\;Sn_xN_{1-y}C_y$ solid solution has shown that Sn plays the role of a growth inhibitor of the elementary microcrystallites of the iron carbonitride. The coercive force and saturation magnetization of iron carbonitride obtained from co-precipitated iron oxalate were 500 Oe and 120 emu/g, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.563-569
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• 1999

The numerical simulation method was utilized to investigate the optimal condition for synthesizing ultrafine SiC powders by using $TMS[Si(CH_3)_4]-H_2$ gaseous mixtures in the horizontal reactor. As a result of the theoretical analysis, the conversion percentage of TMS source was increased with increasing reaction temperature, however, which was decreased with increasing H$_2$flow rate. Though the SiC particles concentration synthesized was decreased with increasing the reaction temperature due to the higher collision rate in the gas phase, they were increased with increasing the H$_2$flow rate and TMS concentration. The SiC particle size showed a tendency to become larger as the reaction temperature and the initial TMS concentration were increased and smaller as the H$_2$ flow rate was increased. The variation of experimental particle size with the reaction temperature, H$_2$flow rate and TMS concentration was agreed with the theoretical results.

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.709-714
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• 2003

Eu doped $Y_2$ $O_3$ nanoparticles were prepared with the solvothermal synthesis using the ethyleneglycol solvent at 20$0^{\circ}C$ for 3-5 h and then annealed in air at 1000-140$0^{\circ}C$ for 2-4 h. The X-ray diffraction pattern of annealed crystals at 100$0^{\circ}C$ for 2 h could be indexed as pure cubic cell of $Y_2$ $O_3$ phase with lattice parameters a=10.5856 $\AA$ which is very close to the reported data (JCPDS Card File, 41-1105 a=10.6041 $\AA$). Average size of prepared phosphor particles have about 100 nm, which were spherical morphology. The phosphor particle sizes decreased and the emission intensity increased at the annealing temperature. Though PL spectrum analysis, the 3% Eu doped $Y_{2-x}$ $O_3$:E $u_{x}$ $^{3+}$(x=0.06) phosphor showed the excitation spectrum at 250 nm wavelength and the maximum emission spectrum at 611 nm wavelength.

• Journal of Adhesion and Interface
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• v.14 no.2
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• pp.82-87
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• 2013

Preliminary studies on the synthesis of magnetic nanoparticles including nanoporous carbon materials have been done via a direct carbonization process from resol, ferric nitrate and triblock copolymer F127. The results show that the nanoporous magnetite/carbon ($Fe_3O_4$/carbon) with a low $Fe_3O_4$ content (1 wt%) possesses an ordered 2-D hexagonal (p6mm) structure, uniform nanopores (3.6 nm), high surface areas (up to 635 $m^2/g$) and pore volumes (up to 0.48 $cm^3/g$). Magnetite nanoparticles with a small particle size (10.2 nm) were confined in the matrix of amorphous carbon frameworks with superparamagnetic property (7.7 emu/g). The nanoporous magnetite/carbon showed maximum adsorption amount (995 mg/g) of ibuprofen after 24 h at room temperature. The nanoporous magnetite/carbon was separated from solution easily by using a magnet. The nanoporous magnetite/carbon material is a good adsorbent for hydrophobic organic drug molecules, i.e. ibuprofen.

• Journal of the Korean Magnetics Society
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• v.9 no.1
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• pp.23-28
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• 1999

${\Alpha}-Fe_2O_3$ was accomplished by chemical method as low temperature as possible and the crystallographic and magnetic properties have been studied by Mossbauer spectroscopy and X-ray diffraction. The sample heated at 15$0^{\circ}C$ is found to have a Corundums symmetry with the hexagonal lattice constant a=8.26$\pm$0.05$\AA$, c=8.75$\pm$0.05$\AA$. The M$\"{o}$ssbauer spectra between the 4.2K and the room temperature show that the ${\Alpha}-Fe_2O_3$ crystallized with a single phase and fine sizes. The particle size distribution has the Gaussian distribution center at 98$\AA$ and the half width of 32$\AA$.TEX>.

• Journal of Environmental Health Sciences
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• v.31 no.4 s.85
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• pp.316-321
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• 2005

4개 업종(축전지제조업, 광명단 제조업, 2차 제련업, 라디에타 제조업)에서 근무하는 총 100명의 근로자를 대상으로 8단계다단충돌기(eight stages personal cascade imparter)에 의한 입자 크기 별 납농도를 측정하였다 크기 별 납 농도는 총납(PbA), 흡입성납(IPM-PbA), 흉곽성납(TPM-PbA), 호흡성납(RPM-PbA), $1{\mu}m$ 미만의 납$(Pb_{1\mu})$ 그리고 $1{\mu}m$ 이상의 소화성납$(Pb_{ing})$이었다. 동일한 근로자(100명)를 대상으로 혈액에서 납농도를 측정하였다. 혈액 중 납은 원자흡광광도계(atomic absorption spectrometry)의 Zeeman effect graphite furnace를 이용하여 분석하였다. 총 납의 노출농도는 노출기준$(50\;ug/m^3)$을 크게 초과하였다. 평균 호흡성 납 노출농도$(115.7\;ug/m^3)$ 총 납의 노출기준을 훨씬 초과하였다. $1{\mu}m$미만의 납$(Pb_{1\mu})$ 노출농도의 범위는 0.7에서 $(492.2\;ug/m^3)$이나 되었다. 근로자의 $46\%$가 혈액 중 납 농도 40 ug/dL을 초과하였다. 60 ug/dL을 초과한 경우도 $13\%$나 되었다. 입자 크기가 큰 납인 총납, 흡입성 납 그리고 호흡성 납 농도는 혈액 중 납 농도와 유의한 상관을 보였다(p<0.0001). 그러나 가장 높은 상관은 $1{\mu}m$미만의 납$(Pb_{1\mu})$ 혈액 중 납과의 관계였다. T-test에서 $50ug/m^3$이상의 호흡성 납을 나타낸 근로자 그룹과 $50ug/m^3$ 이하의 근로자 그룹간에의 혈액 중 납 농도는 유의한 차이가 있는 것으로 나타났다(p=0.000). 이러한 연구결과는 입자크기 구분이 없는 현재의 총납에 의한 노출기준과 측정방법은 미세 납 먼지에 노출되는 근로자의 납흡수를 보호하는데 한계점이 있다는 것을 의미한다. 향후 납 입자크기는 물론 근로자의 개인적인 위생과 작업내용 등을 변수로 납 흡수에 영향을 미치는 종합적인 요인을 찾아내는 연구를 진행할 필요가 있다.

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1322-1326
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• 1997

Characteristics of viscosity and spray dried particles for several polysaccharides were studied to investigate the possibilities as wall materials for microencapsulation. Viscosities of 10% maltodextrin, 10% gum arabic, 10% dextran, 1% gum locust bean, and 1% gum karaya were 2.2 mPa.s, 9.2 mPa.s, 13.0 mPa.s, 4660.0 mPa.s, and 77.0 mPa.s, respectively. In scanning electron micrographs for spray dried polysaccharides, gum arabic had spherical shapes at 20% and 30% emulsion concentration, while trailed shapes at 40%. Maltodextrin had uniform spherical shapes at 30%, while aggregated form with various kinds of capsule sizes at 40%. Dextran had spherical shapes at 20%, while trailed fibrous shapes at over 30%. Mixed polysaccharides with gum arabic:maltodextrin (1:3, w/w) had uniform spherical shapes at 20%, 30%, and 40% with increasing diameter with increasing concentration.

• Economic and Environmental Geology
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• v.37 no.3
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• pp.291-301
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• 2004

In order to charaterize weathering of chalcopyrite and behavior of dissolved metal ions in waste rocks from Manjang Cu mine, mineralogical studies such as refractive microscope, XRD and SEM/EDS analyses carried out. The weathering was mainly occurred in fractures and edge of the chalcopyrite within the mine waste rocks. The weathering process can be seen to reflect four stages based on the weathering degree of chalcopyrite. The main secondary minerals are goethite, covellite, azurite, malachite and brochantite. Dissolved Cu and As were mainly adsorbed Fe-hydroxide. Poorly crystalline Fe-oxide contains relatively high As contents. In oxdizing condition, the weathering of chalcopyrite mainly occurs along the fracture, while the replacement of chalcopyrite observed mainly in the grain and produced covellite and brochantite. The dissolved metals (Cu, Fe, As) in waste rocks from the abandoned Manjang mine area could attenuate naturally by precipitation, adsorption and replacement reaction.

• Journal of the Korean Magnetics Society
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• v.14 no.5
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• pp.169-173
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• 2004

We have synthesized monodispersed $\alpha$-F $e_2$ $O_3$ nano particles to investigate the spin change during the Morin transition temperature( $T_{M}$). The particle size was founded to have a very uniform distribution of 80 nm by x-ray diffraction and size dispersion analyzer. The Mossbauer spectra between the 4.2 K and the room temperature show that $T_{M}$ was shifted and the spin states of Fe ion were changed with the particle size. The Morin transition temperature of bulk usually quoted in literature is 265 K but, it decreases with the size and no transition was found at the critical size down to 4.2K. The spin direction of 80 nm sized particles are normal to the hexagonal c-axis above the $T_{M}$ and are tilted about 28～29$^{\circ}$ below $T_{M}$, which is the [110] direction of rombohedral structure.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.2
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• pp.75-83
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• 2009

In order to understand the impacts of the construction of artificial sea dikes on carbon cycle in Samangeum area being a closed environment after April, 2006, we had measured suspended particulate matters, particulate and dissolved organic carbon in the surface water of inner Saemangeum dike from 2003 to 2006. The significant inputs of suspended particulate matter and organic carbon were mainly occurred during the wet season which suggests that most organic matter loading is concentrated within a short period of time inside the dike. The concentrations of particulate matter and organic carbon have gradually increasing every year inside of dike from the Mangyeong river estuary to Saemangeum dike, which has been closed since 2003 after the construction of the 4th dike. The particulate organic carbon increased due to the phytoplankton blooms by eutrophication. If the large portion of particulate organic matter produced in the surface water sink to the bottom sediment, this will cause the anoxic condition in this closed environment.