• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.204-210
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• 1996

M type hexa-ferrites were prepared by means of a solid state reaction using mill scale, $Fe_{2}O_{3}$, and the mixture of mill scale and $Fe_{2}O_{3}$. The mixture of powders were calcined at $1150^{\circ}C$ for 2 hrs. and sintered at $1250^{\circ}C$ for 2 hrs, with varing the mole ratio of $Fe_{2}O_{3}$/$BaCO_{3}$, by 5.2~6.0. And the magnetic properties and morphologies of Baferrites with impurities such as $SiO_{2},\;Al_{2}O_{3},\;MgO,\;CaO\;and\;Na_{2}O$ in the mill scale were investigated. The magnetic properties were worsened by the addition of $Na_{2}O because of non-reacted iron oxide and intermediate compound of $BaFe_{2}O_{4}$ but they were improved apparently by the addition of $Si_{2}$ and $Al_{2}O_{3}$ in the composition of $BaO.5.6Fe_{2}O_{3}$. Moreover, $M_{s}$ decreased but $_{B}H_{C}$ increased through the addition of $Al_{2}O_{3}$ in Ba-ferrite. ${(BH)}_{max}$ of sintered BM($BaCO_{3}$, mill scale mixture) and BFM($BaCO_{3}$, $Fe_{2}O_{3}$, and null scale mixture) were 0.86 and 1.04 MGOe, respectively, and the magnetic properties were changed around $440^{\circ}C$.

• Journal of Magnetics
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• v.16 no.4
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• pp.431-434
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• 2011

The reduction of the Nb content in the $(Fe_{0.75}B_{0.20}Si_{0.05})_{96}Nb_4$ bulk metallic glass (BMG) has been studied. The glass-forming ability (GFA) is reduced by decreasing the Nb content, but it can be enhanced by replacing partially Fe by Co. Furthermore, the saturation magnetization of the $(Fe_{0.8}Co_{0.2})_{76}B_{18}Si_3Nb_3$ BMG is 1.35 T, being with 13% larger than that of the base alloy $(Fe_{0.75}B_{0.20}Si_{0.05})_{96}Nb_4$. $(Fe_{0.8}Co_{0.2})_{76}B_{18}Si_3Nb_3$ BMG exhibits slightly larger $B_{800}$ (the magnetic flux density at 800 A/m) and smaller core losses (20%-30%) compared with the commercial Fe-6.5 mass% Si steel.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.6
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• pp.264-271
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• 2016

The effect of the oxygen content and the annealing temperature on the tensile behavior of the Ti-1.5Al-3Fe-0.25Si-(0.1~0.5)O alloy was investigated. The tensile properties were dependent on the volume fraction of the microstructure constituents, i.e. the equixed ${\alpha}$, equixed ${\beta}$ and lamellar ${\alpha}$. The results showed that the O-partitioned equixed ${\alpha}$ had a much higher strength compared to the equixed ${\beta}$. The strength of the lamellar ${\alpha}$ increased with increasing the annealing temperature because the O content of the lamellar ${\alpha}$ increased. Ti-1.5Al-3Fe-0.25Si-0.3O alloy annealed to $900^{\circ}C$ where the volume fraction of lamellar ${\alpha}$ was the highest exhibited an excellent combination of the strength (1198.5 MPa) and ductility (27.5%). The effect of the lamellar ${\alpha}$ on the ductility was discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.31-36
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• 1993

Na-Fe Tourmalene ($NaFe_3Al_6B_3Si_6O_{27}F_4$)single crystals were grown by FZ method. The Growth conditions are counter rotation 20~30rpm, growth rate 1~5mm/hr in the atmospheric environment. The transition elements as Fe(in this research), Mn, Co, etc, are exist in the theoretical fomulae so that dopants were not added. The feed rod was sintered between $1000^{\circ}C$ and $1l00^{\circ}C$, but at higher temperature, it was difficult to manufacture the feed rod because of evaporation of the elements such as F. As grown crystals had a black color and the length of 50~60mm, the diameter of 5~6mm. X-ray powder diffraction pattern indicated that the composition of the feed rod was right to the Tourmaline composition. By FT-IR spectra, the state of bonding of each element was charaterized.

• Journal of the Korean Magnetics Society
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• v.25 no.2
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• pp.43-46
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• 2015

$Si(100){\backslash}200nm$ $SiO_2{\backslash}5nm$ $Ta{\backslash}5nm$ $MgO{\backslash}35nm$ $Fe_3O_4$ multi-layers were prepared by using RF-sputtering and ultra-high vacuum molecular beam epitaxy (UHV-MBE) techniques. After post-annealing the multi-layers at $500^{\circ}C$ for 1 hour under the high vacuum of ${\sim}1{\times}10^{-6}Torr$, we observed ferromagnetic properties at room temperature as well as the Verwey transition which is the typical features of magnetite crystals formed. We have carried out a comparative study of the effect of Ta buffered layer on the crystallinity and magnetic properties of $Fe_3O_4$ thin films prepared under different growth and annealing conditions.

• Journal of Magnetics
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• v.16 no.2
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• pp.177-180
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• 2011

0.30 mm thick and 90 mm wide thin foils made of Fe-6.5wt.%Si alloy were successfully fabricated by traditional rolling. The as-rolled sheets had good shapes and shining metal luster. The effects of annealing temperature on the magnetic properties of the sheets were investigated. Excellent Dc properties ($H_c$: 11.55 A/m, ${\mu}_m$: 23710, and $B_s$: 1.439 T) were obtained at an annealing temperature of 1453 K for 1.5 h. At low frequencies ($\leq$ 1 kHz), heat treatment temperature has little effect on iron loss which remained at the level of 9.8 W/kg. Annealing at 1273 K for 1.5 h is optimum for frequencies above 5 kHz.

• Journal of the Mineralogical Society of Korea
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• v.2 no.1
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• pp.8-10
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• 1989

Sphene from the McDonald pegmatite near Bancroft, Ontario, Canada was analyzed using EPMA. It contains 4.3 to 6.3 weight percent of Nb2O5 with an average formula Ca1.02(Ti0.62Al0.22Nb0.07Fe0.06Ta0.01)Si0.99(O4.85F0.16). Three types of subtitutions are possible; 1)2Ti4+=(Nb, Ta)5+ + (Al, Fe3+), 2) Ti + O = (Al, Fe3+) + (F, OH), and 3) 2Ti + O = Fe2+ + (Nb, Ta)5+ + (F, OH). T재 different schemes of substitutions for balancing the analysis are considered when the iron is either all ferric or all ferrous. Assuming stoichiometry fo Ca and Si, a general formula derived from the two different schemes is Ca(Ti0.64Al0.22Fe3+0.06-X {{{{Fe_{x}^{2+} }} Nb0.01)Sio4.80-XF0.16(OH)0.04+x.

• Corrosion Science and Technology
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• v.16 no.1
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• pp.15-22
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• 2017

An oxidation-reduction scheme is an alternative approach for improving the galvanizability of advanced high-strength steel in the continuous hot-dip galvanizing process. Here, we investigated the effect of oxygen partial pressure ($P_{O_2}$) on the oxidation behavior of a transformation-induced plasticity steel containing 1.5 wt% Si and 1.6 wt% Mn during heating to and holding for 60 s at $700^{\circ}C$ under atmospheres with various $P_{O_2}$ values. Irrespective of $P_{O_2}$, a thin amorphous Si-rich layer of Si-Mn-O was formed underneath the Fe oxide scale (a $Fe_2O_3/Fe_3O_4$ bilayer) in the heating stage. In contrast to Si, Mn tended to segregate at the scale surface as $(Fe,Mn)_2O_3$. The multilayered structure of $(Fe,Mn)_2O_3/Fe_2O_3/Fe_3O_4$/amorphous Si-Mn-O remained even after extended oxidizing at $700^{\circ}C$ for 60 s. $Fe_2O_3$ was the dominantly growing oxide phase in the scale. The enhanced growth rate of $Fe_2O_3$ with increasing $P_{O_2}$ resulted in the formation of more Kirkendall voids in the amorphous Si-rich layer and a less Mn segregation at the scale surface. The mechanisms underlying the absence of FeO and the formation of Kirkendall voids are discussed.

• Journal of Korea Foundry Society
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• v.32 no.5
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• pp.219-224
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• 2012

The effects of Mg and Si contents on the microstructure and mechanical properties in Al-Mg alloy (ALDC6) were investigated. The results showed that phase fraction and size of $Mg_2Si$ and $Al_{15}(Fe,Mn)_3Si_2$ phase in the microstructure of Al-Mg alloy were increased as the Mg and Si contents were raised from 2.5 to 3.5 wt%. With Si content of 1.5 wt%, freezing range of the alloy was significantly reduced and solidification became more complex during the final stage of solidification. While there was no significant influence of Mg contents on mechanical properties, Si contents up to 1.5 wt%, strongly affected the mechanical properties. Especially elongation was reduced by about a half with more than 1.0 wt%Si in the alloy. The bending and impact strength were decreased with increased amount of Si in the alloy, as well. The lowered mechanical properties are because of the growth of particle shaped coarse $Mg_2Si$ phase and precipitation of the needle like $\beta$-AlFeSi in the microstructure at the last region to solidify due to presence of excess amount of Si in the alloy.

• Journal of Korea Foundry Society
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• v.5 no.3
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• pp.13-18
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• 1985

Decarburization phenomena were investigated at $800^{\circ}C$ by the $PH_2O/PH_2$ + Ar gas mixture in the case iron range which contains Si, Mn and Cr as an alloying elements. Dissociation of cementite in a matrix which contains graphitizer as Si begins at the carbon rich cementite dendrite arms. Several primary austenite $({\gamma})$ skeletons are surrounded by those nucleated graphite nodules, and that forms a limited area of nucleation region. Decarburization reactions at $800^{\circ}C$ in Fe-C, Fe-Mn-C and Fe-Cr-C alloy are followed by parabolic rate law under the gas mixture of $PH_2O/PH_2=0.01$ and the modified rate const. ${\kappa}$ were in the range of $1{\sim}6{\times}10^{-10}cm^2/s$.