• Journal of the Korean Magnetics Society
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• v.22 no.5
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• pp.167-172
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• 2012

In order to analyze the formation mechanism of iron oxide nanoparticles, we measured the heat flow of $Fe(OL)_3$ precursor with temperature, and TEM images and AC susceptibility of aliquots samples sequentially taken from the reaction solution, respectively. The thermal decomposition of two OL-chain from $Fe(OL)_3$ produced the Fe-OL monomer, which were contributed to the formation of iron oxide nanoparticles. In the initial stage of nanoparticles formation, the small iron oxide nanoparticles had ${\gamma}-Fe_2O_3$ structure. However, as the iron oxide nanoparticles were rapidly growth, the iron oxide nanoparticles showed ${\gamma}-Fe_2O_3$-FeO core-shell structure which the FeO layer was formed on the surface of ${\gamma}-Fe_2O_3$ nanoparticles by insufficient oxygen supply from the reaction solution. These nanoparticles were transformed to $Fe_3O_4$ structure by oxidation during long aging time at high temperature. Finally, the $Fe_3O_4$ nanoparticles with high saturation magnetization and stable in the air could be easily synthesized by the thermal decomposition method.

• Journal of Adhesion and Interface
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• v.19 no.3
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• pp.106-112
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• 2018

Recently, the hyperthermia treatment of malignant tissues has gained great attention as a biocompatible and benign method that facilitates successful cancer therapy compared to radiation and chemotherapy. In this study, superparamagnetic ($Fe_3O_4$) iron oxide nanoparticles (IONP) coated with biocompatible polymer (IONP@P(MPC/FOM)) for the purpose of hyperthermia treatment were prepared and related characterization were performed. IONPs with having 15 nm diameter were first prepared by coprecipitation and followed by surface modification with 4-cyanopentanoic acid dithiobenzoate (CTP) for reversible addition-fragmentation chain transfer (RAFT) copolymerization by using 2-methacryloyloxyethyl phosphorylcholine (MPC) and fluorescein O-methacrylate (FOM) to form corona layer of P(MPC/FOM) on the surface of the IONP. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the morphology and hydrodynamic size of the IONP@P(MPC/FOM) and thermogravimetric analysis (TGA) confirmed the formation of P(MPC/FOM) corona layer, respectively. Exposing IONP dispersion to alternating magnetic field suggests that the IONP@P(MPC/FOM) aqueous dispersion with 0.2 wt.% can be used for hyperthermia treatment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.2
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• pp.120-125
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• 2006

By employing a rapid solidification method and atmospheric annealing at $450^{\circ}C-1hr$, we were able to manufacture inexpensively granular CuCo alloy ribbons with thickness of $20{\mu}m$ showing giant magnetoresistance (GMR) ratio of more than 5% at a high magnetic field of 0.5T. To verify maximum MR effect, the MR ratio, saturation magnetization, and microstructure change were investigated with Co contents between 5 and 30 at%. It was possible to obtain GMR ratios of 5.2% at 1.2T, and 3% at 0.5T, which implies an appropriate MR for industrial purpose at a Co content of $8{\sim}l4%$. MR ratio was reduced rapidly at a Co content below 5% due to superparamagnetic effect and at a Co content above 20% due to agglomeration of Co clusters. Surface oxidation during rapid solidification and atmospheric annealing did not have much affect on MR ratio. Our result implies that our economic CuCo granular alloy ribbons may be appropriate for high magnetic field sensor applications with wide content range of $8{\sim}14$ at%Co.

• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.157-162
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• 2011

The effect of ferrous/ferric molar ratio and precipitants on the formation of nano size magnetite particle was investigated by coprecipitation method. Ferrous sulfate and ferric sulfate were used as iron sources and sodium hydroxide and ammonium hydroxide was used as a precipitant. Single phase magnetite was synthesized with all of experiment conditions (ferrous/ferric molar ratios and precipitants). Particle size was smaller, and particle size distribution was narrower when NaOH was used than $NH_4OH$ was used. The crystallinity and particle size was increased and narrower particle size distribution with increasing molar ratio ferrous/ferric sulfate with the same precipitant. Super paramagnetism could be obtained at all of experiment conditions. The highest saturation magnetization (72 emu/g) was obtained when the ferrous/ferric molar ratio was 2.5 and precipitant was used $NH_4OH$.

• The Journal of the Korea Contents Association
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• v.10 no.8
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• pp.249-256
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• 2010

To the detect of SPIO-labelled hMSC, in vitro study on various cell concentration and in vivo molecular magnetic resonance imaging(MRI) technique using T2, $T2^*$ and SWI are compared with pathology. Cell concentration was $1.56{\times}10^4$, $3.13{\times}10^4$, $6.25{\times}10^4$, $1.25{\times}10^5$, $2.5{\times}10^5$, $5{\times}10^5\;cells/m{\ell}$ and for control $5{\times}10^5\cells/m{\ell}$. MRI technique using T2, $T^2$ and SWI. Photothrombotic infarction was located 2.5mm from bregma right, posterior. Cell injected through the tail vein of rat for 8 rats. MRI performed pre injection and post injection of 1, 3, 7 and 14days and sacrifice for pathology. MRI analysed on quantitatively. In vitro result, SWI was highest CNR as compared with $T2^*WI$, T2WI and $2.5{\times}10^5\;cells/m{\ell}$ cell concentration. In vivo result among the T2WI, $T2^WI$, SWI, T2WI is highest CNR between normal and infarction. CNR in normal-SPIO and infarction-SPIO is high score in SWI. Therefore, T2WI is good distinguish between normal and infarction, SWI are well detect SPIO-labelled hMSC from normal and infarction. Nowaday, SWI are mostly used on hemorrhage, calcification etc. in clinically, but for the future, stem cell therapy is commonly application at all disease which is good observing tool for SPIO-labelled stem cells.