• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.791-794
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• 2008

MRE(Magneto-rheological Elastomer) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb broader frequency range of vibration. These characteristic phenomena result from the orientation of magnetic particle (i.e., chain-like formation) in rubber matrix. In this study, NR was used as a matrix in order to manufacture MREs. Magnetic reactive powder(MRP), having rapid magnetic reaction, was selected as a magnetic particle to give magnetic field reactive modulus. The mechanical properties of manufactured MREs were measured without the application of magnetic field. The results showed that the tensile property and resilience were decreased while the hardness was increased with the addition of CIP. The analysis of MR effect was carried out by FFT analyzer with various magnetic flux. As the addition of MRP and magnetic flux increased, increment of MR effect was observed.

• 한국표면공학회지
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• 제51권2호
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• pp.104-109
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• 2018

Fe-2 wt.%Ni alloys were fabricated by metal powder injection molding, and their oxidation behavior at $600-700^{\circ}C$ for 30 h in air was studied in order to find the effect of the small addition of Ni in the iron matrix on the high-temperature oxidation. Oxide scales that formed after oxidation consisted primarily of $Fe_2O_3$, where microscopic voids were scattered. Nickel was segregated initially at the scale/matrix interface, and later at the lower part of the $Fe_2O_3$ scale. At $600^{\circ}C$, Fe-2wt.%Ni alloys oxidized parabolically initially, and linearly after 15 h. At $650-700^{\circ}C$, they oxidized linearly from the initial period. Although Fe-2wt.%Ni alloys oxidized slower than pure iron, their oxidation rates were relatively fast.

• 한국분말재료학회지
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• 제9권1호
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• pp.25-31
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• 2002

The efects of mechanical aloying conditions and the type of reducing agent on the solid state reductionof haematite $Fe_2O_3$ have been investigated at room temperature. Aluminium titanium zinc and copper were used as reducing agent. Nanocomposites of metal-oxide in which oxide particles with nano size were dispersed in Fe matrix were obtained by mechanical alloying of $Fe_2O_3$ with aluminium and titanium respectively However the reduction of $Fe_2O_3$ by coppe was not occurred Composite materials of iron with $Al_2O_3$ and $TiO_2$ were obtained from the system of $Fe_2O_3-Al$ and $Fe_2O_3-Ti$ after ball milling for 20 hrs and 30 hrs respectively. And the system of $Fe_2O_3-Zn$ resulted in the formationof FeO with ZnO after ball milling of 120 hrs. The final grain sizes of iron estimated by X-ray diffraction line-width measurement were in the ranges of 24~33 nm.

• 한국분말재료학회지
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• 제13권2호
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• pp.112-118
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• 2006

[ $R_{1/3}Sr_{2/3}FeO_{3}$ ](R=Pr, Nd, and Sm) was synthesized and their magnetic properties and charge ordering(CO) transition related with lattice dynamics and oxygen vacancy were systematically investigated. The charge disproportion ation(CD) in $R_{1/3}Sr_{2/3}FeO_{3}$(R=Pr,Nd) was in which two kins of iron with valence state $Fe^{3+}$ and $Fe^{5+}$ were found with ratio of 2:1. In this charge ordering state a sequence of $Fe^{3+}Fe^{3+}Fe^{5+}Fe^{3+}Fe^{3+}Fe^{5+}$ exists aligned along the [111] direction of the pseudocubic perovskite structure. The charge ordering exist in distorted structure involving $t_{pd}$ hybridization. The disordering phases coexist in distorted structure as temprature in creases that is controlled amount of oxygen vacancy. The magnetic hyperfine fields indicate charge tranfering temperature as it dissapeared drastically.

• 한국분말재료학회지
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• 제14권2호
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• pp.97-100
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• 2007

The magnetic alloys of Cu-Fe ($Cu_{50}Fe_{50},\;Cu_{80}Fe_{20}\;and\;Cu_{90}Fe_{10}$) were prepared by a mechanical alloying method and their structural and magnetic behaviors were examined by X-ray diffraction and Mossbauer spectra. The magnetization curves did not distinctly show the saturation at 70 kOe for the concentrated alloys of $Cu_{80}Fe_{20}\;and\;Cu_{90}Fe_{10}$. The Mossbauer spectrum of $Cu_{80}Fe_{20}$ at room temperature shows one Lorentzian line of the paramagnetic phase, whereas the Mossbauer spectrum of $Cu_{90}Fe_{10}$ consists of sextet Lorentzian line at room temperature and a centered doublet line. The Mossbauer spectra of $Cu_{90}Fe_{10}$ measured in the temperature ranges from 13 to 295 K, implies that $Cu_{90}Fe_{10}$ to consists of two magnetic phases. One superimposed sextet corresponds to the ferromagnetic iron in Cu and the other one indicates the superparamagnetic iron rich phase.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 전문대학교육위원
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• pp.150-154
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• 2005

This paper is presented for the development of the brushless DC(BLDC) spindle motors for hard disk drives. A new BLDC Motor has the use of insulated, compacted, iron powder for the armature core material of BLDC motors. Insulated iron powder in this paper is generally called soft magnet composite(SMC). The SMC is used for the stator of the motor instead of the laminated steel core. The motor used by SMC can have the good advantages in condition of the high frequency input power and small sized motor. It gets much more high efficiency than laminated steel core at same input power. The proposed motor has a technique of speed sensorless control. Experimental results show the performance of the proposed BLDC spindle motors for an HDD.

• Journal of Electrochemical Science and Technology
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• 제12권4호
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• pp.398-405
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• 2021

To fabricate a full-scale pilot model of the cost-effective Na-(Ni,Fe)Cl₂ cell, a Na-beta-alumina solid electrolyte (BASE) was developed by applying a one-step synthesis cum sintering process as an alternative to the conventional solid-state reaction process. Also, Fe metal powder, which is cheaper than Ni, was mixed with Ni metal powder, and was used for cathode material to reduce the cost of raw material. As a result, we then developed a prototype Na-(Ni,Fe)Cl₂ cell. Consequently, the Ni content in the Na-(Ni,Fe)Cl₂ cell is decreased to approximately (20 to 50) wt.%. The #1 prototype cell (dimensions: 34 mm × 34 mm × 235 mm) showed a cell capacity of 15.9 Ah, and 160.3 mAh g^-1 (per the Ni-Fe composite), while the #2 prototype cell (dimensions: 50 mm × 50 mm × 335 mm) showed a cell capacity of 49.4 Ah, and 153.2 mAh g^-1 at the 2^nd cycle.

• 한국분말재료학회지
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• 제15권4호
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• pp.271-278
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• 2008

Sintering behavior of iron nanopowder agglomerate compact prepared by slurry compaction method was investigated. The Fe nanopowder agglomerates were prepared by hydrogen reduction of spray dried agglomerates of ball-milled $Fe_2O_3$ nanopowder at various reduction temperatures of $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$, respectively. It was found that the Fe nanopowder agglomerates produced at higher reduction temperature have a higher green density compact which consists of more densified nanopowder agglomerates with coarsed nanopowders. The sintering behavior of the Fe nanopowder agglomerates strongly depended on the powder packing density in the compact and microstructure of the agglomerated nanopowder. It was discussed in terms of two sintering factors affecting the entire densification process of the compact.

• 한국분말재료학회지
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• 제8권2호
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• pp.104-109
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• 2001

The semiconducting ${\beta}-FeSi_2$ compound has been recognized as a thermoelectric material with excel-lent oxidation resistance and stable characteristics at elevated temperature. In the present work, we applied mechanical alloying(MA) technique to produce ${\beta}-FeSi_2$ compound using a mixture of elemental iron and silicon powders. The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-K $\alpha$ radiation, thermal analysis and scanning electron microscopy. The single ${\beta}-FeSi_2$ phase has been obtained by mechanical alloying of $Fe_{33}Si_{67}$ mixture powders for 120 hrs or for 70 hrs coupled with the subsequent heat treatment up to $700^{\circ}C$. The grain size of ${\beta}-FeSi_2$ powders analyzed by Hall plot method was 44nm.

• 환경위생공학
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• 제22권1호
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• pp.37-47
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• 2007

In order to improve the Quality of fermented soybean Doenjang was investigated. The samples were prepared and fermented by the koji made with A. oryzae, B. subtilis and B. natto strains, that the product added green tea powder with sanitary canned food. 1. The water content of sample was 50.30-42.14%, pH value 6.03-5.52 and total acidity, 3.01-3.87. 2. The reducing sugar content for samples was 9.35-7.81%, Amino-N, 7.96-9.21%. 3. In the sensory evaluation test, the good sensory qualify that was S-2 sample than to S-1 and S-3. 4. The heavy metals analyzed from sample cans, tin, iron and lead content were 27.31-29.04 ppm, 5.32-5.91 ppm and trace amount.