• 소성∙가공
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• 제21권2호
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• pp.138-143
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• 2012

A polishing method using magnetorheological (MR) fluid has been developed as a new precision technique to obtain a fine surface. The process uses a MR fluid that consists of magnetic carbonyl iron (CI) particles, nonmagnetic polishing abrasives, water and stabilizers. But the CI particles in MR fluids cause a severe corrosion problem. When coated with Xanthan gum, the CI particles showed long-term stability in corrosive aqueous environment. The surface roughness obtained from the MR polishing process was evaluated. A series of experiments were performed on fused silica glass using prepared slurries and various process conditions, including different polishing times. Outstanding surface roughness of Ra=2.27nm was obtained on the fused silica glass. The present polishing method could be used to produce ultra-precision micro parts.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.342-349
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• 2018

Polystyrene (PS) was coated on carbonyl iron (CI) particles via dispersion polymerization to produce core-shell structured CI/PS particles and adopted as magnetorheological (MR) material. Two MR fluids were prepared by dispersing CI/PS and CI particles in silicone oil. Their MR and tribological properties were investigated using a rheometer and a reciprocating friction and wear tester, respectively. Experimental data showed that tribological properties of MR fluid based on CI/PS particles are significantly enhanced compared to those of CI based MR fluid. Sedimentation problem of CI/PS MR fluid was also expected to be improved due to relatively lower density of CI/PS particles.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.446-447
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• 2006

Magnetic oxide-coated iron nanoparticles with the mean size ranging from 6 to 75 nm were synthesized by aerosol method using iron carbonyl as a precursor under the flowing inert gas atmosphere. Oxide shells were formed by passivation of asprepared iron particles. The influence of experimental parameters on the nanoparticles' microstructure, phase composition and growth behavior as well as magnetic properties were investigated and discussed in this study.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.251.1-251.1
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• 2007

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.18.2-18.2
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• 2008

• 한국수처리학회지
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• 제26권6호
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• pp.117-124
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• 2018

For the effective removal of phosphorus in water, a novel type of composite was prepared by combining Poly Alumiun Chloride, widely used in sewage/wastewater treatment plants, and Humic Acid particles, which are known to have phosphorus removal ability, with CI. The surface of the ferromagnetic CI particles was oxidized and activated, and then PAC and HA were synthesized to finally produce CIPAC and CIHA. CIPAC and CIHA prepared by this study showed similar results to the phosphorus removal efficiencies of PAC and HA coagulants. The novel composite has a larger weight than the conventional coagulant, and the coagulated sludge precipitates rapidly. The sludge could be easily separated in a short time if the external magnetic field was given by the ferromagnetic force of CIPAC and CIHA prepared with CI as support. Therefore, it can be concluded that if phosphorus removal is carried out using CIPAC and CIHA prepared through this study with external magnetic field, the sedimentation rate will be much faster than that of conventional coagulant. Thus it is possible to obtain a high economic benefit in the sludge recovery part.

• 한국소음진동공학회논문집
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• 제21권12호
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• pp.1132-1137
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• 2011

MRE(magneto-rheological elastomers) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb vibration of broader frequency range. These characteristic phenomena result from the orientation of magnetic particles named carbonyl iron powder(CIP) in rubber matrix. In this paper, simulation on variation rate of shear modulus for anisotropic MRE due to volume fraction of CIP and an effective permeability model was applied to predict the field-induced shear modulus of MREs. Also, the variation rate of shear modulus for anisotropic MRE was derived using magneto-mechanical theory. Based on Maxwell-Garnett mixing rule, the increment of shear modulus was calculated to evaluate the shear modulus of MREs with column structure of CIP due to induced current. The simulation results on variation rate of shear modulus can be applied to the variable mechanical system of MRE such as tunable vibration absorber, stiffness variable bush and mount.

• Journal of Magnetics
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• 제21권4호
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• pp.622-628
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• 2016

Magnetization property is a critical factor for magnetorheological fluids (MRFs) to achieve the liquid-solid transition. The main focus of this study is on exploring the influence factors on magnetization properties of MRFs. In this paper, a theoretical analysis is performed to discuss the magnetization characteristics of MRFs firstly. Then, a method for the preparation of carbonyl iron-based MRFs is illustrated and five MRFs samples with various material parameters are prepared. It is succeeded by a series of experiments on testing the hysteresis loop and the magnetization curve of each sample and the influence factors are compared and analyzed. Experimental results indicate that there is basically no hysteresis phenomenon on MRFs which exhibits superparamagnetic behavior at room temperature. A surfactant coating on magnetic particles can slightly improve the MRFs magnetization. Additionally, the magnetic susceptibility and the saturation magnetization both increase with the particle concentration, whereas the influence of particle diameter is relatively very small. Moreover, as the temperature increases, the magnetization decreases and the declining rate accelerates gradually.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1832-1835
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• 2003

This paper suggests the selective ultra precision polishing techniques for micro die and mold parts using magnetic-assisted machining. Fabrication of magnetic abrasive particle and their polishing performance are key technology at ultra precision polishing process of micro parts. Conventional magnetic abrasives have disadvantages. which are missing of abrasive particle and inequality between magnetic particle and abrasive particle. So, bonded magnetic abrasive particles are fabricated by several method. For example, plasma melting and direct bonding. Ferrite and carbonyl iron powder are used as magnetic particle where silicon carbide and Al$_2$O$_3$ are abrasive particle. Developed particles are analyzed using measurement device such as SEM. Possibility of magnetic abrasive and polishing performance of this magnetic abrasive particles also have been investigated. After polishing, surface roughness of workpiece is reduced from 2.927 $\mu\textrm{m}$ Rmax to 0.453 $\mu\textrm{m}$ Rmax.

• 한국공작기계학회논문집
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• 제12권5호
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• pp.59-66
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• 2003

This study suggests the new ultraprecision finishing techniques for micro die and mold parts using magnetic field-assisted polishing. Conventional magnetic abrasives have several disadvantages, which are missing of abrasive particle and inequal mixture between magnetic particle and abrasive particle. Therefore, bonded magnetic abrasive particles are fabricated by several method. For example, plasma melting and direct bonding. Carbonyl iron powder is used as magnetic particle there silicon carbide and alumina are abrasive particles. Developed magnetic abrasives are analyzed using SEM. Feasibility of magnetic abrasive and polishing performance of this magnetic abrasive particles also have been investigated. After polishing, surface roughness of workpiece is reduced from 85.4 ㎚ Ra to 9 ㎚ RA.