• 한국분말재료학회지
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• 제10권1호
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• pp.51-56
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• 2003

To investigate the effect of the parameters of the plasma arc discharge process on the particle formation and particle characteristics of the iron nano powder, the chamber pressure, input current and the hydrogen volume fraction in the powder synthesis atmosphere were changed. The particle size and phase structure of the synthesized iron powder were studied using the FE-SEM, FE-TEM and XRD. The synthesized iron powder particle had a core-shell structure composed of the crystalline $\alpha$-Fe in the core and the crystalline $Fe_3O_4$ in the shell. The powder generation rate and particle size mainly depended on the hydrogen volume fraction in the powder synthesis atmosphere. The particle size increased simultaneously with increasing the hydrogen volume fraction from 10% to 50%, and it ranged from about 45nm to 130 nm.

• 한국전기전자재료학회논문지
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• 제26권6호
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• pp.478-481
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• 2013

Diameter controlled carbon nanotubes (CNTs) were grown using surface modified iron nano-particle catalysts with aminpropyltriethoxysilane (APS). Iron nano-particles were synthesized by thermal decomposition of iron pentacarbonyl-oleic acid complex. Subsequently, APS modification was done using the iron nano-particles synthesized. Agglomeration of the iron nano-particles during the CNT growth process was effectively prevented by the surface modification of nano-particles with the APS. APS plays as a linker material between Fe nano-particles and $SiO_2$ substrate resulting in blocking the migration of nano-particles. APS also formed siliceous material covering the iron nano-particles that prevented the agglomeration of iron nano-particles at the early stages of the CNT growth. Therefore we could obtain the diameter controlled CNTs by blocking agglomeration of the iron nano-particles.

• 한국자기학회지
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• 제15권3호
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• pp.172-176
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• 2005

화학기상응축법(CVC)에 의한 제조된 네 개의 나노-Fe 입자 시료들이 뫼스바우어, XRD, BET와 TEM에 의하여 조사되었다. 네 개의 시료들은 고순도 이송가스와 분해온도에 의해 구성이 되었다. 각 시료를 구성하고 있는 입자들은 2 또는 3층구조로 형성되었음을 TEM분석으로 알 수 있었다. 평균입도의 경우에는 분해온도에 정비례하는 특성을 보여 주었다. 분해온도가 $500^{\circ}C$일 경우에, 이송가스를 CO로 사용하게 되면 $Fe_3C$의 형성이 $CH_4$보다 용이한 것으로 나타났다. 그러나 $1,100^{\circ}C$의 경우에는, CO와 $CH_4$모두에서 $Fe_3C$의 형성이 대부분을 차지하고 있는 것으로 나타났다.

• 한국재료학회지
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• 제16권12호
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• pp.739-742
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• 2006

The ${\gamma}-Fe_2O_3$ nano particles in the size range of $5{\sim}30$ nm were prepared by a chemical coprecipitation method. The nano particles were coated with 2nd surfactants for obtaining the water-based. The size effect of ${\gamma}-Fe_2O_3$ nano particles for the ultraviolet protection was investigated. The variation of the UV-Vis transmittance spectra as a function of wavelength for a ${\gamma}-Fe_2O_3$ nano particles were showed red-shifted increase with the particle size. The protective effects of UVA onset at near 469, 494, 591 nm for a particle size of 8.7, 9.1 and 12 nm. It is shown that the ${\gamma}-Fe_2O_3$ nano particles was good materials for protect of UV.

• Journal of Magnetics
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• 제21권3호
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• pp.308-314
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• 2016

Cobalt-, zinc-, and nickel-zinc-substituted nano-size manganese ferrite powders, $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, $Mn_{0.8}Zn_{0.2}Fe_2O_4$ and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$, were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently studied. The $MnFe_2O_4$ ferrite powder annealed at temperatures above 523 K exhibited a spinel structure, and the particle size increased as the annealing temperature increased. All ferrites annealed at 773 K showed a single spinel structure, and the lattice constants and particle size decreased with the substitution of Co, Zn, and Ni-Zn. The $M{\ddot{o}}ssbauer$ spectrum of the $MnFe_2O_4$ ferrite powder annealed at 523 K only showed a doublet due to its superparamagnetic phase, and the $M{\ddot{o}}ssbauer$ spectra of the $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, and $Mn_{0.8}Zn_{0.2}Fe_2O_4$ ferrite powders annealed at 773 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of the $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$ ferrite powder annealed at 773 K consisted of two Zeeman sextets and one quadrupole doublet due to its ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explained the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. Relative to pure $MnFe_2O_4$, the saturation magnetizations and coercivities were larger in $Mn_{0.8}Co_{0.2}Fe_2O_4$ and smaller in $Mn_{0.8}Zn_{0.2}Fe_2O_4$, and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$. These variations could be explained using the site distribution equations, particle sizes and magnetic moments of the substituted ions.

• 한국자기학회지
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• 제17권2호
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• pp.76-80
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• 2007

화학기상응축공정법으로 세 가지 분해온도에서 제조된 나노 Fe-N 시료들을 뫼스바우어 분광기, XRD와 BET를 이용하여 자기적 특성의 변화를 연구하였다. 분해온도가 낮을수록 ${\gamma}'-Fe_4N$의 형성이 용이하였으며, 중간온도에서의 ${\epsilon}-Fe_{2.12}N$을 거쳐 높은 분해온도에서는 ${\gamma}-Fe$가 주로 형성되었다. 높은 분해온도에서는 Fe와 N이 서로 잘 결합되지 못하였는데, 이는 Fe와 N을 결합시키기 위해서는 분해온도를 낮게 하는 것이 바람직하다는 것을 의미한다.

• Journal of Magnetics
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• 제6권3호
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• pp.94-100
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• 2001

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. BCC structure of Fe-Co-Ni spherical particles can be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-80$0^{\circ}C$ for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a post heating at $600^{\circ}C$ for 5 hours. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nano-particles in a random arrangement on $Al_2O_3$substrate the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and inter-particle distance.

• 공업화학
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• 제21권6호
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• pp.676-679
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• 2010

이송식 직류 열플라즈마를 이용하여 ZrVFe 합금모재로부터 복합 나노 입자를 제조하여 플라즈마 가스 유량이 제조된 입자의 특성에 미치는 영향을 분석하였다. 입자의 특성은 전계방출 주사전자 현미경(FE-SEM), 입도 분석기(PSA), X선 분광기(EDS), X선 회절계(XRD), Brunauer-Emmett-Teller (BET) 비표면적 측정기를 사용하여 분석하였다. 플라즈마 가스 유량을 20 L/min에서 40 L/min으로 증가시키면 평균입자크기가 91 nm에서 55 nm로 감소하며 입도분포의 기하학적 편차가 줄어들었고 비표면적은 $200m^2/g$에서 $255m^2/g$으로 증가하였으며 제조된 입자의 조성에는 큰 영향을 미치지 못했지만 결정성이 향상되었다.

• 한국입자에어로졸학회지
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• 제8권2호
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• pp.83-88
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• 2012

The electrical wire explosion process in liquid media is promising for nano-sized metal and/or alloy particles. The hybrid Pt/Fe-Cr-Al and Pt/Ni-Cr-Fe nanoparticles for exhaust emission control system are synthesized by electrical wire explosion process in liquid media. The alloy powders have spherical shape and nanometer size. According to the wire component, while Pt/Fe-Cr-Al nanoparticles are shown the well dispersed Pt on the Fe-Cr-Al core particle, Pt/Ni-Cr-Fe nanoparticles are shown the partially separated Pt on the Ni-Cr-Fe core particle. Morphologies and component of two kinds of hybrid nano catalyst particles were characterized by transmission electron microscope and energy dispersive X-ray spectroscopy analysis.

• 한국분말재료학회지
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• 제8권3호
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• pp.151-156
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• 2001

MgO based nanocomposite powder including ferromagnetic iron particle dispersions, which can be available for the magnetic and catalytic applications, was fabricated by the spray pyrolysis process using ultra-sonic atomizer and reduction processes. Liquid source was prepared from iron (Fe)-nitrate, as a source of Fe nano-dispersion, and magnesium (Mg)-nitrate, as a source of MgO materials, with pure water solvent. After the chamber were heated to given temperatures (500~$^800{\circ}C$), the mist of liquid droplets generated by ultrasonic atomizer carried into the chamber by a carrier gas of air, and the ist was decomposed into Fe-oxide and MgO nano-powder. The obtained powders were reduced by hydrogen atmosphere at 600~$^800{\circ}C$. The reduction behavior was investigated by thermal gravity and hygrometry. After reduction, the aggregated sub-micron Fe/MgO powders were obtained, and each aggregated powder composed of nano-sized Fe/MgO materials. By the difference of the chamber temperature, the particle size of Fe and MgO was changed in a few 10 nm levels. Also, the nano-porous Fe-MgO sub-micron powders were obtained. Through this preparation process and the evaluation of phase and microstructure, it was concluded that the Fe/MgO nanocomposite powders with high surface area and the higher coercive force were successfully fabricated.