• Journal of the Korean Magnetics Society
• /
• 제1권1호
• /
• pp.12-16
• /
• 1991

The effect of annealing on the magnetic properties and the microstructures of the amorphous $Fe_{76-x}Cu_1Mo_xSi_{14}B_9$(x=2,3) alloys were investigated. When annealed at 500${^{\circ}C}$ for 1hr, $8{\sim}9{\times}10^3$ of the effective permeability and 3~4 A/m of the coercive force were achieved upon crystallization to $\alpha$-Fe phase. And the average diameter of the $\alpha$-Fe grains was about 20nm. For the nanovrystalline ferromagnets. the fine grain size is the important requirement to obtain a good soft magnetic property. In this work, in order to get the finer grain size of $\alpha$-Fe phase, two-step annealing treatment was given. That is, following the low-temperature at $400{^{\circ}C}$ for 1~3hr, the high-temperature annealing at $500{^{\circ}C}$ for 1hr was carried out. As the low-temperature annealing time increased, the effective permeability increased to $1.2{\sim}1.7{\times}10^4$ and the coercive force decreased to about 2 A/m. And the grain size was observed to be smaller than 10nm. The increased permeability and the decreased coercive force were attributed to the reduced average crystalline anisotropy by the refinement of $\alpha$-Fe(Si) grains.

• Journal of the Korean Magnetics Society
• /
• 제20권3호
• /
• pp.114-119
• /
• 2010

Fe compounds of volcanic rock samples distributed in the seaside area of Ulleung island were investigated by means of X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF) and M$\ddot{o}$ssbauer spectroscopy. We found that samples were typical basic rock which had the total amount of iron compounds including hematite ($\alpha-Fe_2O_3$) varies from 10.6 w% to 14.5 w% depending on the different regions by XRF. The M$\ddot{o}$ssbauer spectra of the samples were consisted of one sextet due to hemitite and doublets due to $Fe^{3+}$ in various clay mineral and $Fe^{2+}$ in pyroxene $(Ca,Fe,Mg)_2(SiO_4)_2$, ilmenite ($FeTiO_3$) and olivine $(Mg,Fe)_2SiO_4$. The balance state of Fe ions of all samples was chiefly $Fe^{3+}$, so we could find that the volcanic rocks distributed in the seaside area of Ulleung island were made in inland.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 한국재료학회 2007년도 추계학술발표대회 및
• /
• pp.108.2-108.2
• /
• 2007

• Proceedings of the Materials Research Society of Korea Conference
• /
• 한국재료학회 2000년도 추계학술발표강연 및 논문개요집
• /
• pp.155-155
• /
• 2000

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.59-72
• /
• 1999

In this thesis, we measured the Barkhausen effect of CoFeSiB amorphous ribbon and then investigated its possibility to be used as a sensor material. We used a sample of composition $($Fe_{0.06}$$Co_{0.94}$)_${0.79}$$Si_{2.1}$$B_{18.9}$ with a thickness 12[pm1, width 2.5[rnml and length 5[cm], which was fabricated by a single roll method. In order to improve magnetic characteristics of the sample, we had carried on annealing in the magnetic field and in none magnetic field. And, experimented results to the magnetic characteristics show that the ribbon has large Barkhausen jump even in weak magnetic field below 0.5[0el. From the results, we confirmed that the sample can be used as an magnetic sensor material.

• Electrical & Electronic Materials
• /
• 제10권2호
• /
• pp.113-118
• /
• 1997

For the amorphous F $e_{78}$ $B_{13}$S $i_{9-x}$G $e_{x}$ alloy, thermal analysis and measurements of the magnetic properties were carried out. As the content of Ge increased, the crystallization temperature was decreased and the Curie temperature was increased, and the tendencies were almost linear. The core loss of the amorphous alloy for x=1.7, field annealed at optimized condition, was 0.057 W/kg(l.0T, 60Hz), which was about 30% lower than that of no Ge added amorphous alloy (basic composition). Such a low core loss characteristics was thought to be caused by the lower coercive force and good squareness of B-H loop of the alloy.y.y.

• Korean Chemical Engineering Research
• /
• 제50권3호
• /
• pp.398-402
• /
• 2012

The catalytic performance of some metal oxides in the vapor phase selective oxidation of $H_2S$ in the stream containing ammonia and water was investigated. Among the catalysts tested $Fe_2O_3/SiO_2$ was the most promising catalyst for practical application. It showed higher than 90% $H_2S$ conversion and very small amount of $SO_2$ emission over a temperature range of $240{\sim}280^{\circ}C$. The effects of reaction temperature, $O_2/H_2S$ ratio, amount of ammonia and water vapor on the catalytic activity of $Fe_2O_3/SiO_2$ were discussed to better understand the reaction mechanism. The $H_2S$ conversion showed a maximum at $260^{\circ}C$ and it decreased with increasing temperature over $280^{\circ}C$. With an increase of $O_2/H_2S$ ratio from 0.5 to 4, the conversion was slightly increased, but the selectivity to elemental sulfur was remarkably decreased. The increase of ammonia amount favored the conversion and the selectivity to elemental sulfur with a decrease in $SO_2$ production. The presence of water vapor decreased both the activity and the selectivity to sulfur, but increased the ATS selectivity.

• Applied Microscopy
• /
• 제21권2호
• /
• pp.57-66
• /
• 1991

The main purpose of this paper was to investigate the change of rapidly solidified microstructures and dispersoid behavior according to heat-treatment in the Al-Fe-V-Si-(Mn) alloys. It was found that (111) preferred orientation identified by X-ray diffraction and fine subgrain/large grain were observed in the rapidly solidified Al-Fe-V-Si-(Mn) alloys. Cell boundary of the zone A was composed of the microcrystalline, whereas that of the zone B was amorphous. Decomposition of the Al-Fe-V-Si-(Mn) alloys occurred at about $300^{\circ}C$. These alloys exhibited excellent thermal stability at the elevated temperature. Microstructure of the zone B was more stable than that of the zone A. The spherical dispersoid and 5-fold symmetry phase was also more thermally stable than the amorphous structure of cell boundary.

• Journal of the Korean Magnetics Society
• /
• 제6권5호
• /
• pp.323-328
• /
• 1996

NiFe($60\;{\AA}$)/Cu($60\;{\AA}$)/Co($30\;{\AA}$) trilayers were formed on the $4^{\circ}$ tilt-cut Si(111) substrate by rf magnetron sputtering method. With a Cu($50\;{\AA}$) underlayer, NiFe($60\;{\AA}$)/Cu($60\;{\AA}$)/Co($30\;{\AA}$) trilayers developed in-plane magnebc anisotropy and in-plane perpendicular alignment of easy axes in two magnetic components of NiFe($60\;{\AA}$)/Cu($60\;{\AA}$)/Co($30\;{\AA}$) trilayers has been found. The easy axis of Co layer consisbng of NiFe($60\;{\AA}$)/Cu($60\;{\AA}$)/Co($30\;{\AA}$) trilayers turned out to be along $4^{\circ}$ tilt Si <112> direcbon and that of NiFe layer along Si <110> direction. [NiFe($60\;{\AA}$)/Cu($60\;{\AA}$)/Co($30\;{\AA}$)]/Cu($50\;{\AA}$)/Si(111, $4^{\circ}$ tiIt-cut) trilayers showed about 2.2 % MR ratio at room temperature and large plateau in MR curves, which are more improved MR characteristics than those in [NiFe($60\;{\AA}$)/Cu($60\;{\AA}$)/Co($30\;{\AA}$)]/Cu($50\;{\AA}$)/glass trilayers with no appreciable magnetic anisotropy.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• 제28권2호
• /
• pp.48-53
• /
• 2014

The shield effect of 4 layered shield case was investigated in this paper. The material of the case was non-oriented SiFe sheet with a thickness of 0.5mm. The size of the case was 100mm wide, 100mm high and 300mm long. Relative permeability of SiFe sheet was needed to calculate shield effect. It was obtained from the measurement by a ferrite yoke and from the calculation by eddy current FEM analysis. Three configurations were used to connect both ends of SiFe sheet. First one is a connection by double-welded butt. Second one is to put the sheet the same material above the confronted both ends of the sheet to avoid a leakage magnetic flux. The last one is ideally without any connection. The shield effect of the second one agreed well with the last one and showed the shield effect of -40dB.