• Proceedings of the IEEK Conference
• /
• 2001.10a
• /
• pp.770-775
• /
• 2001

Effects of magnetic field and carrier gas velocity on the magnetic separation of FCC catalyst by a high gradient magnetic separator were studied. The activities of the equilibrium catalyst, the magnetic particles and the nonmagnetic particles were evaluated in a fixed bed microreactor The results showed that heavy metal contaminated catalyst can be selectively separated by means of high gradient magnetic separation at magnetic field 0.5T and carrier gas velocity 0.3m.s$^{-1}$ , and lightly metal contaminated catalyst retained high catalytic activity.

• Korean Journal of Materials Research
• /
• v.12 no.3
• /
• pp.215-219
• /
• 2002

For the purpose of annihilating tumor in body, hematoporphyrin as a photosensitizer was coated onto magnetic particles of $Fe_3O_4$ prepared by coprecipitation which could be concentrated around the tumor by magnetic field. The photosensitizer was applied differently before, during and after adsorbing the 1st surfactant on the particles. Its added amount was $5{\times}10^{-4}/mol$, and the coating reaction proceeded at temperatures of 60, 70 and 8$0^{\circ}C$. The amounts of photosensitizer coated on the magnetic particles were obtained by calculating an optical density with the maximum UV spectrum. As a result of the UV analysis, the coating amount of photosensitizer increased with higher reaction temperatures. When applied at 8$0^{\circ}C$ after adsorbing the 1st surfactant, the photosensitizer was coated with a maximum value of $3.8{\times}10^{-3}/mo1/$\ell$$. The TGA analysis revealed that the ferrofluids included the particles of 30.115 g/$\ell$. It was suggested that the magnetite particles was coated with photosensitizer of $1.26{\times}10^{-4}/mo1/g$. A small-sized device for magnetic field and light emission was designed, in which LED sheets coverts the permanent magnet of Nd-Fe-B. The LED sheet was connected in series circuit and also protected with a silicon tube. The power was supplied with rechargable battery of 9V and 100-120mA.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.745-748
• /
• 1995

Magnetic nanoparticles of iron and iron oxide have been prepared in a modified upward thermal diffusion cloud chamber using pulsed laser evaporation. SEM/TEM studies of these particles reveal a size distribution with a mean diameter of about $60\;{\AA}$. FTIR spectrum measurements are used to investigate the difference in oxidation level between nanoparticles prepared at different partial oxygen pressures. The complex magnetic behaviour of these particles was studied using DC- and AC-susceptibility measurements. All samples exhibit superparamagnetism with blocking temperatures ranging from 50 K to above room temperature. The coercivity fields as well as the dependence of the blocking temperature on measuring frequency have been studied. magnetic anisotropy constants are found to be one order of magnitude higher than is known for the bulk values. The mean particle size estimated from the magnetic data is found to be in perfect agreement with the TEM observations.

• Journal of the Korean Chemical Society
• /
• v.27 no.5
• /
• pp.376-381
• /
• 1983

Dispersed nickel particles on Spherocarb were prepared at 540$^{\circ}C$ in various reaction atmosphere. Magnetic properties of these samples were determined, and results were compared with those of unsupported and MgO supported nickel particles. It was shown that nickel react primarily with carbon regardless of reducing atmosphere. In addition, apparent possibility of nickel-carbon interaction was discussed.

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

• Journal of the Korean Magnetics Society
• /
• v.8 no.1
• /
• pp.1-5
• /
• 1998

Acicular Fe-Co alloy particles are one of the candidates for high-density magnetic recording media. We examined the effects of Co additions on the magnetic properties of Fe-Co alloy particles by using M$\'{o}$ssbauer spectroscopy, TEM, and X-ray diffraction. Acicular $Fe_n$Co (n=5, 4, 3, 2) alloy particles coated with silica, were prepared by a chemical coprecipitation method and subsequent H $_2$ reduction. The crystal structure was found to be cubic in all n ranges. The lattice constant $a_0$ decreases with increasing Co contents. Analysis of $^{57}Fe$ M\'{o}$ssbauer effect data in terms of the local configurations of Co atoms has permitted the influence of magnetic hyperfine interactions to be monitored.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.1
• /
• pp.59-65
• /
• 2014

Indoor air quality including metro subway is of recent interests in large cities. Inflow air to the inside of the train and circulating air flow through MVAC of stations contain large amount of iron based fine particles. This paper evaluated the collection of such a dust by magnetic filters as comparing to conventional particle capturing mechanisms such as inertia, direct impaction and diffusion. It was found that filtration velocity, magnetic field intensity, and fiber size were the most important parameters for magnetic filtration. Application of magnetic force obviously enhances the collection efficiency particularly in fine modes smaller than 10 mm. However, its effect was found greater in 2.5 mm than submicron particles.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.474-477
• /
• 1995

Granular Fe-SiO films were prepared by co-evaporating in a vacuum. Magnetic properties of the films were investigated by $M\"{o}ssbauer$ and magnetization measurments. The $M\"{o}ssbauer$ data suggest that the films consist of amorphous Fe-Si alloy particles with the size of nanometers. Superparamagnetic magnetization curves were well reproduced by considering the distribution of particle size and the magnetic dipole interaction between particles as the mean field.

• Radiation Oncology Journal
• /
• v.12 no.3
• /
• pp.295-300
• /
• 1994

It was the purpose of present study to develop a new thermoseed for heating deep-seated tumors and assessment of the effect of magnetic control on thermoseeds. Aqueous suspension of iron micro spheres (Ferropolysaccharide) was injected directly into the VX-2 hepatoma and heated with 1.2 MHz inductive radiofrequency unit. Aqueous thermoseed suspension was delivered to the tumor by simple percutaneous injection. The limitation of the thermoseed heating method is the positional change of thermoseed particles in the tumor after implantation. The thermoseed particles could enter the systemic blood circulation and cause a severe embolization of a critical organ. To minimize this limitation, we have used the magnetic control after loading the thermoseed in the tumor, W hen ferropolysaccharides were exposed to a strong magnetic field, they magnetized and subsequently exerted a magnetic force on each other, forming larger aggregates of particles. The size of aggregated Particles were too big to enter the systemic blood circulation. Thus, unlike other thermoseed method, we hold the thermoseed particles stationary in the tumor. The temperature of the injected site and immediate vicinity elevated by $4-5^{\circ}C$. The temperature of the surrounding normal hepatic tissue elevated by $1-2^{circ}C$ only. The heating effect within the tumor was variable depending on the density of ferromagnetic aqueous suspension. Our results suggest that inductive heating of tumor injected with ferropolysaccharide solution offers the possibility of effective heat delivery to the defined tumor volume, which is difficult to heat with other heating devices.

• Journal of the Mineralogical Society of Korea
• /
• v.23 no.2
• /
• pp.99-106
• /
• 2010

To evaluate a potential wash-out effect of rainfalls, a preliminary environmental magnetic test was attempted. Measurement of isothermal remanent magnetization (IRM) and intensive microscopic observations were carried out on the solid particles extracted from the rainfalls collected for the past year (2009) in Daejeon, Korea. Dust particles collected from the rain-free (daily dust) or dustheavy days (during the Asian dust storm event) were also used as a comparison. IRMs were unanimously low for the solid particles extracted from the rainfalls, indicating an efficient wash-out effect of rainfalls as long as the magnetic concentration is concerned. Electron microscopy identified carbonbearing material, (carbon-coated) magnetite, and quartz. It is highly likely that the carbon-containing particles were produced by anthropogenic fossil fuel combustion.