• 한국광물학회지
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• 제15권1호
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• pp.59-68
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• 2002

캐나다 퀘벡 주 오카지역에서 산출되는 네오비움 페롭스카이트(일명 라트라파이트, $Ca_2NbFe^{3+}O_6$)에 대하여 화학분석과 분말 X선 회절 데이터를 이용한 리트벨트 구조분석을 실시하였다. 라트라파이트는 $CaTiO_3-NaNbO_3-Ca_2NbFe^{3+}O_6$의 연속계열 고용체의 성분을 가지며, 화학분석 결과 평균$(Ca_{1.5}Na_{0.4})\;(Nb_{0.1}Ti_{0.6}Fe_{0.4})O_6$ 리트벨트 구조분석 결과 라트라파이트의 구조는 페롭스카이트($CaTiO_3$)의 결정구조와 유사하지만, Ti 이온이 Nb와 $Fe^{3+}$에 의해 치환되면서 상당히 뒤틀리고, $TiO_6$ 팔면체가 페롭스카이트에 비해 서로 기울어져 있는 모습을 보여준다 새롭게 결정된 라트라파이트의 공간군은 Pbnm, 단위포는 a=5.4474(4), b=5.5264(4), c=7.7519(5) ${\AA},\;V=233.4(3){\AA}^3$이다.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2567-2573
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• 2012

We successfully synthesized $Fe_3O_4@SiO_2$ nanoparticles with ultrathin silica layer of $1.0{\pm}0.5$ nm that polyethyleneimine (PEI) with low molecular weight of 2.0-4.0 kDa was covalently conjugated with the resulting $Fe_3O_4@SiO_2$ nanoparticles by silane coupling reaction. The PEI-$Fe_3O_4@SiO_2$ nanoparticles were further used as gene delivery vector for a human fibroblast cell (IMR-90) line. Gene transfection efficiency of the PEI-$Fe_3O_4@SiO_2$ complexes did not increase remarkably after magnetofection; however, the addition of Lipofectamine 2000 significantly increased the transfection efficiency of the PEI-$Fe_3O_4@SiO_2$ complexes. We believe that the present approach could be utilized for magnetofection as alternative to $Fe_3O_4$ nanoparticles conjugated with the PEI of high molecular weight thanks to its relatively low cytotoxicity and high transfection efficiency.

• 한국광학회지
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• 제28권3호
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• pp.97-102
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• 2017

본 논문에서는 플라즈모닉 코어와 자성 쉘로 구성된 $Ag@Fe_3O_4$ 나노입자의 흥미로운 광학적 특성에 대해 연구를 하였다. 기존의 60 nm의 지름을 갖는 은 나노입자의 표면에 높은 굴절률을 갖는 $Fe_3O_4$ 쉘이 형성됨에 따라 국소 표면 플라즈몬 공명(Localized surface plasmon resonance; LSPR) 파장이 420 nm에서 650 nm로 이동하는 red-shift 현상을 관찰 할 수 있었고, 또한, 세 가지 시뮬레이션 모델들 ($Ag@Fe_3O_4$ 나노입자, $Fe_3O_4$ 쉘 나노입자, 은 나노입자)을 통해서 410 nm 파장의 peak이 60 nm의 두께를 가진 $Fe_3O_4$ 쉘에 의해 발생하는 산란이 주된 원인이라는 것을 규명하였다. 이 결과는 비슷한 종류의 나노입자를 이용한 추후 다양하고 복잡한 나노어셈블리의 광학적 현상을 이해하는데 사용될 것이다.

• 한국세라믹학회지
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• 제34권11호
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• pp.1159-1164
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• 1997

Magnetite(Fe3O4) powders were synthesized through glycothermal reaction by using crystalline $\alpha$-FeOOH as precursor and ethyleanne glycol as solvent. The phase, morphology and particle size of synthesized powders were characterized by XRD and an SEM. When only ethylene glycol was used as solvent, the phase was transformed from $\alpha$-FeOOH to $\alpha$-Fe2O3 and finally Fe3O4 at 27$0^{\circ}C$ for 6hr without morphological change. But by addition of water, Fe3O4 powders were synthesized at 23$0^{\circ}C$ for 3hr through solution-recrystalization process. As the content of water addition increased, the particle shape changed from sphere to octahedron and the partcle size increased. When the excess amount of water added, residual $\alpha$-FeOOH or $\alpha$-Fe2O3 was recrystalized.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 C
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• pp.506-508
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• 2000

Oxide of the form $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ present properties that make them useful as multilayer chip NTC thermistor for mobile phone NTC thermistor electric properties of $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ system has been measured as a function of temperature and composition. In $Mn_{3}O_{4}-NiO-Fe_{2}O_{3}$ composition, it can be seen that resistivity and B-constant were increased as the ratio of $Mn_{3}O_{4}/F_{2}O_{3}$ and $Mn_{3}O_{4}$/NiO was increased. In particular, resistance change ratio (${\Delta}R$), the important factor for reliability varied within ${\pm}1%$, indicating the compositions of these products could be available for mobile phone.

• 한국자기학회지
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• 제6권3호
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• pp.145-150
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• 1996

Ferrite plating 방법은 진공이 불필요하고, 저온(< $100^{\circ}C$)에서 페라이트 박막을 제작할 수 있다. 이 방법으로 유리 기판위에 $80^{\circ}C$에서 $Fe_{3-x}Mn_{x}O_4(x=0.0~0.023)$의 페라이트 박막을 제작하였다. 박막은 60분간 성장시켰으며, 막의두께는 약 $9000\AA$이었고, 거울면과 같은 광택을 지녔다. X-선 회절 실험으로 스피넬 구조의 단일상을 확인하였다. $Fe_{3-x}Mn_{x}O_4$ 박막의 구성비 x는 반응용액에서의 구성비 x'에 비해 매우낮다(x/x'=0.04). $Fe_{3}O_{4}$ ferrite 박막의 포화자화($M_{s}$)는 480 emu/cc로써 bulk 시료와 비슷한 값을 가졌다.

• 전기화학회지
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• 제17권2호
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• pp.124-129
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• 2014

본 논문에서는 리튬/공기 이차전지의 공기전극에 사용될 수 있는 카본미소구체/$Fe_3O_4$ 나노복합체의 합성과 전기화학적 특성에 대해 보고하고 있다. 산화물 촉매 중 하나인 $Fe_3O_4$의 부족한 전도성을 보완하기 위해 카본미소구체와 복합화를 시도하였고 그 결과 카본미소구체 표면에 수 nm 크기의 $Fe_3O_4$를 균일하게 분산시켜 복합화 할 수 있었다. 이와 같이 미세하게 분산된 산화물 촉매와 카본과의 결합은 촉매의 비표면적을 넓히고 카본과 촉매와의 접촉면을 넓혀 전도성을 높임으로서 높은 촉매 활성을 기대할 수 있다. 카본미소구체/$Fe_3O_4$ 나노복합체를 이용하여 만든 전극은 카본미소구체를 사용한 전극에 비해 낮은 과전압과 상대적으로 안정한 사이클 특성을 관찰할 수 있었다.

• 전기화학회지
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• 제13권4호
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• pp.246-250
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• 2010

In this study, nano-crystallized $Al_2O_3$ was coated on the surface of $LiFePO_4$ powders via a novel dry coating method. The influence of coated $LiFePO_4$ upon electrochemical behavior was discussed. Surface morphology characterization was achieved by transmission electron microscopy (TEM), clearly showing nano-crystallized $Al_2O_3$ on $LiFePO_4$ surfaces. Furthermore, it revealed that the $Al_2O_3$-coated $LiFePO_4$ cathode exhibited a distinct surface morphology. It was also found that the $Al_2O_3$ coating reduces capacity fading especially at high charge/discharge rates. Results from the cyclic voltammogram measurements (2.5-4.2 V) showed a significant decrease in both interfacial resistance and cathode polarization. This behavior implies that $Al_2O_3$ can prevent structural change of $LiFePO_4$ or reaction with the electrolyte on cycling. In addition, the $Al_2O_3$ coated $LiFePO_4$ compound showed highly improved area-specific impedance (ASI), an important measure of battery performance. From the correlation between these characteristics of bare and coated $LiFePO_4$, the role of $Al_2O_3$ coating played on the electrochemical performance of $LiFePO_4$ was probed.

• Journal of Magnetics
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• 제16권2호
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• pp.164-168
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• 2011

Magnetic nanoparticles can potentially be used in drug delivery systems and for hyperthermia therapy. The applicability of $Fe_3O_4$, $CoFe_2O_4$, $MgFe_2O_4$, and $NiFe_2O_4$ nanoparticles for the same was studied by evaluating their magnetization, thermal efficiency, and biocompatibility. $Fe_3O_4$ and $CoFe_2O_4$ nanoparticles exhibited large magnetization. $Fe_3O_4$ and $NiFe_2O_4$ nanoparticles exhibited large induction heating. $MgFe_2O_4$ nanoparticles exhibited low magnetization compared to the other nanoparticles. $NiFe_2O_4$ nanoparticles were found to be cytotoxic, whereas the other nanoparticles were not cytotoxic. This study indicates that $Fe_3O_4$ nanoparticles could be the most suitable ones for hyperthermia therapy.

• Bulletin of the Korean Chemical Society
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• 제18권8호
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• pp.831-840
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• 1997

Core/shell structured composite metal oxides of Fe2O3/MgO were prepared by thermal decomposition of Fe(acac)3 adsorbed on the surface of MgO cores. The morphology of the composites conformed to that of the MgO used as the cores. Broad powder X-ray diffraction peaks shifted toward larger d, large BET surface area (∼350 m2/g), and the size of crystalline domains in nano range (4 nm), all corroborate to the nanocrystallinity of the Fe2O3/MgO composite which was prepared by using nanocrystalline MgO as the core. By use of microcrystalline MgO as the core, microcrystalline Fe2O3/MgO composite was prepared, and it had small BET surface area of less than 35 m2/g. AFM measurements on nanocrystalline Fe2O3/MgO showed a collection of spherical aggregates (∼80 nm dia) with a very rough surface. On the contrary, microcrystalline Fe2O3/MgO was a collection of plate-like flat crystallites with a smooth surface. The nitrogen adsorption-desorption behavior indicated that microcrystalline Fe2O3/MgO was nonporous, whereas nanocrystalline Fe2O3/MgO was mesoporous. Bimodal distribution of the pore size became unimodal as the layer of Fe2O3 was applied to nanocrystalline MgO. The macropores in a wide distribution which the nanocrystalline MgO had were absent in the nanocrystalline Fe2O3/MgO. The decomposition of CCl4 was largily enhanced by the overlayer of Fe2O3 on nanocrystalline MgO making the reaction between nanocrystalline Fe2O3/MgO and CCl4 be nearly stoichiometric. The reaction products were environmentally benign MgCl2 and CO2. Such an enhancement was not attainable with the microcrystalline samples. Even for the nanocrystalline MgO, the enhancement was not attained, if not with the Fe2O3 layer. Without the layer of Fe2O3, it was observed that the nanocrystalline domain of the MgO transformed into microcrystalline one as the decomposition of CCl4 proceeded on its surface. It appeared that the layer of Fe2O3 on the particles of nanocrystalline Fe2O3/MgO blocked the transformation of the nanocrystalline domain into microcrystalline one. Therefore, in order to attain stoichiometric reaction between CCl4 and Fe2O3/MgO core/shell structured composite metal oxide, the morphology of the core MgO has to be nanocrystalline, and also the nanocrystalline domains has to be sustained until the core was exhausted into MgCl2.