• Journal of the Korean Magnetics Society
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• v.19 no.5
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• pp.165-170
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• 2009

It is well-known that a meta-stable fcc bulk Fe has an antiferromagnetic (AFM) ground state and could be synthesized by growing Fe on a proper fcc metal substrate. In this study magnetism of Fe monolayers on nonmagnetic fcc transition metal (Cu, Rh, Pd, and Ag) (001) surfaces has been investigated using the all-electron full-potential linearized augmented plane wave method. The Fe monolayers on Rh(001) and Pd(001) surfaces were calculated to be stabilized in an AFM state, whereas the Fe monlayers on Cu(001) and Ag(001) surfaces are stabilized in a ferromagnetic (FM) state. Noting that Cu and Ag have the smallest and largest lattice constants and the fcc bulk Fe with a larger lattice constant is getting stabilized in a ferromagnetic state, it is unexpectable and interesting. The calculated magnetic moments of the Fe atoms on Cu, Rh, Pd, and Ag(001) surfaces are 2.811, 2.945, 2.987, and 2.990 $_{{\mu}B}$ in FM states and 2.624, 2.879, 2.922, and 3.001 $_{{\mu}B}$ in AFM states.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.11
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• pp.963-968
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• 2000

Magnetic properties and microstructures of Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films were investigated as a function of addition of element Ag, (X$\_$Ag/=0 to 6 at.%) and annealing temperature, T$\_$a/=300$\^{C}$ to 600$\^{C}$. In the case of adding Ag, magnetic properties of Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films were improved than those of Ag-free Fe$\_$93/Zr$_3$B$_4$thin films. The prominent soft magnetic properties with coercivity of 1.1 Oe, saturation magnetization of 2.2 T and permeability of 5400 at 50㎒ were obtained from Fe$\_$88/Zr$_3$B$_4$Ag$\_$5/ thin film annealed was lower than that of Fe-base or Co-base thin films reported previously. Such enhanced magnetic properties are presumably attributed to the format in ultra fine grains. Also, the reduced eddy current loss in the annealed sample is due to refined micro magnetic domains with increasing the amount of Ag in Fe$\_$93-x/Zr$_3$B$_4$Ag$\_$x/ thin films.

• Journal of the Korean Magnetics Society
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• v.3 no.2
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• pp.130-134
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• 1993

The magnetic properties of the amorphous $Fe_{73.5-X}Co_{X}Cu_{1}Nb_{3}Si_{13.5}B_{9}(x=2,\;4)$ alloys, fabricated by a single roll rapid quenching technique and annealed at $400~650^{\circ}C$, have been investigated. The optimum annealing temperature is $550^{\circ}C$ for the amorphous $Fe_{71.5}Co_{2}Cu_{1}Nb_{3}Si_{13.5}B_{9}$ alloy. The properties of the nanocrystalline $Fe_{71.5}Co_{2}Cu_{1}Nb_{3}Si_{13.5}B_{9}$ alloy show the relative permeability of $1.1{\times}10^{4}$ and the coercive force of 0.22 Oe at 1 kHz. When annealed at $600^{\circ}C$, the nanocrystalline $Fe_{69.5}Co_{4}Cu_{1}Nb_{3}Si_{13.5)B_{9}$ alloy shows the relative permeability of $1.0{\times}10^{4}$ and the coercive force of 0.19 Oe at 1 kHz. From the X-ray measurement, it is found that the remarkably improved soft magnetic properties are the effect of the formation of $\alpha$-Fe(Si) grain. By the results of FMR exper-imeIlt, the optimum annealing condition is just below temperature which the peak-to-peak line width of FMR spectrum increase rapidly.

• Journal of Magnetics
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• v.14 no.4
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• pp.150-154
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• 2009

The effect of Ga and, Nb addition on the kinetics and mechanism of the disproportionation of a Nd-Fe-B alloy were investigated by isothermal thermopiezic analysis (TPA) using $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ (x=0 and 0.3, y= 0 and 0.2) alloys. The addition of Ga and Nb retarded the disproportionation kinetics of the Nd-Fe-B alloy significantly, and increased the activation energy of the disproportionation reaction. The disproportionation kinetics of the $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys measured under an initial hydrogen pressure of 0.02 MPa were fitted to a parabolic rate law. This suggested that during the disproportionation of $Nd_{12.5}Fe_{(81.1-(x+y))}B_{6.4}Ga_xNb_y$ alloys with an initial hydrogen pressure of 0.02 MPa, a continuous disproportionation product is formed and the overall reaction rate is limited by the diffusion of hydrogen atoms (or ions).

• Journal of Advanced Marine Engineering and Technology
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• v.10 no.4
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• pp.57-66
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• 1986

The microstructure and mechanical properties of unidirectionally solidified Al-Fe-Ni and Al-Fe-B alloys have been studied in varying the some conditions. To investigate the change of microstructure and mechanical properties was carried out by the varying the composition and solidification rate from 1.2 to 80 mm/min at temperature gradient 60 .deg. C/cm. The results obtained are as follow; 1. In proportion to the increase of the solidification rate, the type of crystallized phase of these composite alloys was changed by added element. a) The crystallized phase of composite alloy in added nikel was changed from the rod-type fiber to platetype fiber. b) The crystallized phase of composite alloy in added boron was changed from the plate-type fiber to rod-type fiber. 2. The strength was rapidly increased with the changing process of crystallized fiber from the plate-type fiber to the rod-type.

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.259-268
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• 1996

In the present study the effect of the addition of Fe on the pressureless and hot press sintering behavior was studied under Ar atmosphere. Pressureless sintering was performed 1900~220$0^{\circ}C$ under. Ar atmosphere. The addition of 1 wt% Fe was increased effectively of the sintered density. However it was impossible to obtain high density higher than 90%,. Zr-Fe-B compound in liquid phase was observed from the EDS and WDS analysis. It was considered that sinterability was enhanced due to the mass transfer through Fe based liquid phase formed at the sintering temperature. Hot pressing was performed at 1600~1$700^{\circ}C$ under Ar atmos-phere for 1 hr. It was possible obtain 95% relative density of ZrB2 specimen which is higher density at pressure-less sintering. It could be thought that ZrB2 particles was rearranged through liquid phase by applied pressure during initial stage of sintering.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.70.1-70
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• 2000

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.902-907
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• 2023

To understand the eutectic reaction mechanism and the relocation behavior of the core debris is indispensable for the safety assessment of core disruptive accidents (CDAs) in sodium-cooled fast reactors (SFRs). This paper addresses reaction products and their distribution of the eutectic melting/solidifying reaction of boron carbide (B₄C) and stainless-steel (SS). The influence of the existence of carbon on the B₄C-SS eutectic reaction was investigated by comparing the iron boride (FeB)-SS reaction by Raman spectroscopy with Multivariate Curve Resolution (MCR) analysis. The scanning electron microscopy with dispersive X-ray spectrometer was also used to investigate the elemental information of the pure metals such as Cr, Ni, and Fe. In the B₄C-SS samples, a new layer was formed between B₄C/SS interface, and the layer was confirmed that the formed layer corresponded to amorphous carbon (graphite) or FeB or Fe₂B. In contrast, a new layer was not clearly formed between FeB and SS interface in the FeB-SS samples. All samples observed the Cr-rich domain and Fe and Ni-rich domain after the reaction. These domains might be formed during the solidifying process.

• Journal of Powder Materials
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• v.22 no.3
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• pp.208-215
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• 2015

Fe-TiC composite powders were fabricated by planetary ball mill processing. Two kinds of powder mixtures were prepared from the starting materials of (a) (Fe, TiC) powders and (b) (Fe, $TiH_2$, Carbon) powders, respectively. Milling speed (300, 500 and 700 rpm) and time (1, 2, and 3 h) were varied. For (Fe, $TiH_2$, Carbon) powders, an in situ reaction synthesis of TiC after the planetary ball mill processing was added to obtain a homogeneous distribution of ultrafine TiC particulates in Fe matrix. Powder characteristics such as particle size, size distribution, shape, and mixing homogeneity were investigated.

• Journal of the Korean Magnetics Society
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• v.8 no.4
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• pp.198-202
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• 1998

We have studied $Al_xFe_{3-x}O_4$ produced by direct composition method using X-ray diffraction and Mssbauer spectroscopy. The cation distribution for $Al_xFe_{3-x}O_4$ was determined by the ratio of sub-spectra absorption area. The charge state of Fe atoms in octahedral site(B-site) is $Fe^{2.5+}$ based on electron hopping, $Fe^{2+}$ ↔ $(Fe^{3+},Al^{3+})$ without dependency of substituted Al amounts.