• Journal of Powder Materials
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• v.20 no.1
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• pp.48-52
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• 2013

A study of oxidation kinetic of Fe-36Ni alloy has been investigated using thermogravimetric apparatus (TGA) in an attempt to define the basic mechanism over a range of temperature of 400 to $1000^{\circ}C$ and finally to fabricate its powder. The oxidation rate was increased with increasing temperature and oxidation behavior of the alloy followed a parabolic rate law at elevated temperature. Temperature dependence of the reaction rate was determined with Arrhenius-type equation and activation energy was calculated to be 106.49 kJ/mol. Based on the kinetic data and micro-structure examination, oxidation mechanism was revealed that iron ions and electrons might migrate outward along grain boundaries and oxygen anion diffused inward through a spinel structure, $(Ni,Fe)_3O_4$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.131-134
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• 2001

Vertically aligned carbon nanotubes are grown on iron-deposited silicon oxide substrates by thermal chemical vapor deposition of acetylene gas at the temperature range 750∼950$^{\circ}C$. As the growth temperature increases from 750 to 950$^{\circ}C$, the growth rate increases by 4 times and the average diameter also increases from 30 nm to 130 nm while the density increases progresively with the growth temperature and a higher degree of crystalline perfection can be achieved at 950$^{\circ}C$. This result demonstrates that the growth rate, diameter, density, and crystallinity of carbon nanotubes can be controlled with the growth temperature.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.251-251
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• 2007

• Journal of the Korean Ceramic Society
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• v.23 no.2
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• pp.55-63
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• 1986

In variuos physcial and chemical cause of damage of refractories for steel makin the clarification of the wear mechanism of brick is situated on important factor. In the present paper the wear mechanism of high alumina brick for the arc-furnace roof were inves-tigated by means of XRD, EPMA. SEM and microscopy. The results obtained were summerized as follows : (1) The altered layers which exist in high alumina brick used for arc-furnace roof were verified by mineral chemical analysis and EPMA. (2) The diffusion of materials combined with slag dust and iron oxide from furnace atmosphere in high basic process from hot face to interior was verified. (3)Activation energy for the synthesized slag permeated into the unused brick texture was 47-51 kcal per mole.

• KSBB Journal
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• v.27 no.3
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• pp.157-160
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• 2012

When iron oxide magnetic nanoparticles were synthesized by co-precipitation method using aqueous ammonia as reducing agent, the synthesized particles were aggregated and thus precipitation occurred. Using Magnolia kobus leaf extract as reducing agent, spherical nanoparticles of 50~200 nm were synthesized with low yield. By using both Magnolia kobus leaf extract and aqueous ammonia as reducing and stabilizing agents, smaller nanoparticles of 40~120 nm could be synthesized with various shapes. The synthesized magnetic nanoparticles were characterized with field emission transmission electron microscopy (FE-TEM) and scanning electron microscopy (SEM). TEM and SEM images showed that the magnetic nanoparticles are a mixture of triangles, tetragons, rods and spherical structures.

• Journal of the Korean Ceramic Society
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• v.45 no.10
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• pp.605-609
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• 2008

This work describes the preparation of functionalized magnetic nanoparticles(MNPs) and their bioapplication to human DNA separation. Silica coated MNPs were prepared by changing the volume ratio of tetraethyl orthosilicate(TEOS) for controlled coating thickness on the original nanoparticle of MNPs. The sol-gel process in silica coating on MNPs surface was adapted for relatively mild reaction condition, low-cost, and surfactant-free. And then amino functionalized magnetic nanoparticles were synthesized using amine groups as surface modifiers. The result of adsorption efficiency for human DNA with amino-functionalized silica coated MNPs was calculated as a function of the number of amine groups.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.8-18
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• 2010

When metal oxides are exposed to chemical potential gradients, ions are driven to diffusive mass transport. During this transport process, the divergence of ionic fluxes offers the formation/annihilation of oxides. Therefore, the divergence of ionic flux may play an important role in the void formation in oxides. Kinetic equations were derived for describing chemical potential distribution, ionic fluxes and their divergence in oxides. The divergence was found to be the measure of void formation. Defect chemistry in scales is directly related to the sign of divergence and gives an indication of the void formation behavior. The quantitative estimation on the void formation was successfully applied to a growing magnetite scale in high temperature oxidation of iron at 823 K.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.107-107
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• 2001

목적： 초상자성 nano-particle 조영제의 자기이완효과에 관한 out sphere 기전에 기초하여 각각의 자기장의 세기에서 T1/T2 자기이완율을 나타내는 NMRD profile을 수치적으로 simulation 하는 프로그램을 개발하고자 하였다. 대상 및 방법： 초상자성 nano-particle 조영제의 경우 초상자성 물질을 생체적합성 고분자로 표면 coating하기 때문에 상자성 조영제와는 달리 전적으로 "out sphere"기여도만을 고려하였고 또한 초상자성 물질의 경우 자기적 에너지의 크기가 매우 크기 때문에 상자성 조영제의 기전에서 사용되는 "low field"근사를 사용할 수 없으므로 Brillouin 함수로 표현되는 총자화에 대한 표현을 적용하였다. nano-particle내에 포함된 Fe 원자수에 따른 T1 및 T2 NMRD Profile과 온도에 따른 T1 및 T2 NMRD Profile 그리고 초상자성 nano-particle size에 따른 T1 및 T2 NMR Profile을 PC (CPU=800 Mhz, memory=128 MB) 환경하에서 symbolic computation tool 인 MathCad (MathCad, USA)를 사용하여 구현하였다.

• The Korean Journal of Nuclear Medicine
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• v.38 no.2
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• pp.205-208
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• 2004

The two major classes of magnetic resonance (MR) contrast agents are paramagnetic contrast agents, usually based on chelates of gadolinium generating T1 positive signal enhancement, and super-paramagnetic contrast agents that use mono- or polycrystalline iron oxide to generate strong T2 negative contrast in MR images. These paramagnetic or super-paramagnetic complexes are used to develop new contrast agents that can target the specific molecular marker of the cells or tan be activated to report on the physiological status or metabolic activity of biological systems. In molecular imaging science, MR imaging has emerged as a leading technique because it provides high-resolution three-dimension maps of the living subject. The future of molecular MR imaging is promising as advancements in hardware, contrast agents, and image acquisition methods coalesce to bring high resolution in vivo imaging to the biochemical sciences and to patient care.

• Journal of Magnetics
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• v.20 no.3
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• pp.221-228
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• 2015

Colloidal particles consisted of individual nanosized magnetite grains on the surface of the silica cores were obtained by two-stage sol-gel technique. Size distribution and microstructure of the particles were analyzed using atomic force microscopy, X-ray diffraction and Nitrogen thermal desorption. Magnetic properties of the particles were studied by the method of the longitudinal nonlinear response. It has been shown that nanoparticles of magnetite have a size corresponding to a superparamagnetic state but exhibit hysteresis properties. The phenomenon was explained using the magnetostatic interaction model based on the hypothesis of iron oxide particles cluster aggregation on the silica surface.