• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.4
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• pp.312-317
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• 2004

High dose ($3{\times}10^{16}cm^{-2}$) implantation of Fe or Ni ions into bulk, single-crystal ZnO substrates was carried out at substrate temperature of ${\sim}350^{\circ}C$ to avoid amorphization of the implanted region. The samples were subsequently annealed at $700^{\circ}C$ to repair some of the residual implant damage. X-Ray Diffraction did not show any evidence of secondary phase formation in the ZnO. The Ni implanted samples remained paramagnetic but the Fe-implanted ZnO showed evidence of ferromagnetism with an approximate Curie temperature of ${\sim}$240K. Preliminary X-Ray Photoelectron Spectroscopy measurements showed the Fe to be ill the 2+ oxidation state. The earrler density in the implanted region still appears to be too low to support carrier-meditated origin of the ferromagnetism and formation of bound magnetic polarons may be one potential explanation for the observed magnetic properties, No evidence of the Anomalous Hall Effect could be found in the Fe-implanted ZnO, but its transport properties were dominated by the conventional or ordinary Hall effect.

• Journal of Powder Materials
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• v.17 no.1
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• pp.23-28
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• 2010

HDDR treated anisotropic Nd-Fe-B powders have been widely used for the sheet motors and the sunroof motors of hybrid or electric vehicles, due to their excellent magnetic properties. Microstructural alignment of HDDR treated powders are mostly depending on the hydrogen reaction in disproportionation step, so the specific method to control hydrogenation reaction is required for improving magnetic properties. In disproportionation step, hydrogenation pressure and reaction time were controlled in the range of 0.15~1.0 atm for 15~180 min in order to control the micorstructural alignment of $Nd_2Fe_{14}B$ phase and, at the same time, to improve remanence of HDDR treated magnet powders. In this study, we could obtain a well aligned anisotropic Nd-Fe-B-Ga-Nb alloy powder having high remanence of 12 kG by reducing hydrogen pressure down to 0.3 atm in disproportionation step.

• Journal of Magnetics
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• v.13 no.4
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• pp.144-148
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• 2008

The size and surface effects on the magnetism of a fcc Fe (001) surface was investigated by performing firstprinciples calculations on 3, 5, 7, and 9 monolayers fcc Fe (001) single slabs with two different two-dimensional lattice constants, ${\alpha}=3.44{\AA}$ (System I) and 3.65 ${\AA}$ (System II), using the all-electron full-potential linearized augmented plane wave method within a generalized gradient approximation. The surface layers were coupled ferromagnetically to the subsurface layer in both systems. However, the magnetism of the inner layers was quite different from each other. While all the inner layers of System II were ferromagnetically coupled in the same way as the surface layer, the inner layers of System I showed a peculiar magnetism, bilayer antiferromagnetism. The calculated spin magnetic moments per Fe atom were approximately 2.7 and 2.9 ${\mu}_B$ at the surface for Systems I and II, respectively, due to the almost occupied Fe d-state being in the majority spin state and band narrowing. The spin orientations of System I were out-of-plane regardless of its thickness, whereas the orientation of System II changed from out-of-plane to in-plane with increasing thickness.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.6
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• pp.399-406
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• 2014

Thermal batteries are used for military power sources that require robustness and long storage life such as missiles and torpedoes. $FeS_2$ powder is currently used for cathode materials because of its high specific energy density, environmental non-toxicity and low cost. However, large particle size of conventional $FeS_2$ has been deterred its possible application for higher power thermal batteries. In order to improve the power density, high energy ball milling of $FeS_2$ has been introduced to crush the micron-sized $FeS_2$. Discharge characteristics of the single cells fabricated with nano-materials and conventional $FeS_2$ powder were evaluated.

• Journal of the Korean Vacuum Society
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• v.4 no.3
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• pp.270-274
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• 1995

The growth structure of Fe on CU(001) was studied by scanning tunneling microscope. An analysis of size distribution of Fe islands on Cu(001) surface was made to determine whether Fe atoms mix with substrate Cu. The size distribution deviates from the standard scaling behavior, indicating that atomic density of Fe decreases with coverage up to 1 ML. The growth can be characterized by layer-by-layer scheme from 1 ML to 5 ML. This result agrees well with previously studied, Auger spectroscopy and RHEED result.

• Archives of Metallurgy and Materials
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• v.66 no.3
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• pp.783-787
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• 2021

This study suggests a new way to modify the size and morphology of Al-Fe phases in modified AA 7075 by using an Fe-Mn solid solution powder as the precursor. When Fe and Mn are added in the form of a solid solution, the diffusion of Fe and Mn toward the Al is delayed, thus altering the chemical composition and morphology of the precipitates. The fine, spherical precipitates are found to provide a good balance between strength and ductility compared to the case where Fe and Mn are separately added.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.3
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• pp.91-97
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• 1998

In a LiNbO$_{3}$ crystal, optical noise is caused by the inhomogeneity of crystal inside if the excess energy is incident on the crystal. In this paper, we experiemnt the influence of optical noise when it is applied for beam diffraction and optical information storage. And it is proposed the energy threshold level which is not affected by optical noise in Fe-LiNbO$_{3}$ crystal(0.02Wt.% doped, 10mm*10mm*10mm). The optical noise of crystal weremeasured as a function of the incident beam intensity(10mw, 5mw, 1mw, 0.5mw), direction in incident(orthogonal, left rotation, right rotation) and wavelength(514.5nm, 632.8nm).

• Journal of the Korean Magnetics Society
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• v.18 no.5
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• pp.195-199
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• 2008

Composites of $Fe_{93.5}Si_{6.5}$ powder and epoxy were prepared using a thermal curing process. Scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and network analyzer were used to analyze the structure, electromagnetic properties and microwave absorption of the composites. Results show that the saturation magnetization depends on the fraction of the $Fe_{93.5}Si_{6.5}$ powder in the composite, which affects initial permeability. It is believed that the eddy current loss is a dominant factor over 1 GHz and that the resonance frequency of the composite decreases with increasing fractions of $Fe_{93.5}Si_{6.5}$ powder. Finally, reflection loss was calculated from the permeability and permittivity of these composites. Composite with 50 wt.% $Fe_{93.5}Si_{6.5}$ powder fractions and 5 mm thickness showed reflection loss below -20 dB from 3.66 GHz to 4.16 GHz. Therefore, it is believed that thin Fe-Si/epoxy composites may be a good candidate for microwave absorption application.

• Journal of the Korean Chemical Society
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• v.39 no.6
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• pp.446-452
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• 1995

Lithium intercalates, $Li_xFeMoO_4Cl$ ($1{\leq}X{\leq}2$) prepared by electrochemical lithiation of $FeMoO_4Cl$ crystallizes in monoclinic structure for all x values as revealed by x-ray diffraction and galvanostatic discharge experiments. According to the x-ray photoelectron spectroscopic study, Fe(III) is at first reduced to Fe(II) upon lithium intercalation with the x domain of $0{\leq}X{\leq}1$, where the crystal symmetry is changed from tetragonal to monoclinic. On the other hand, Mo(VI) is reduced to lower valent state upon further lithium intercalation ($1{\leq}X{\leq}2$), where no crystal symmetry transformation and reduction of Fe(II) to lower valent state are observed. The Mo 3d spectrum for $Li_2FeMoO_4Cl$ appears as a complex shape, but can be deconvoluted into the three sets of the doublet on the basis of Gaussian function, those which correspond to Mo(VI), Mo(V) and Mo(IV) states, respectively. The mixed valent states of molybdenum after further lithiation may be due to a competitive reaction between the formation of Mo(V) and its disproportionation to Mo(IV) and Mo(VI).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.330-330
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• 2008

$Fe_2O_3$ added Pb$(Ni_{1/3}Nb_{2/3})O_3-PbTiO_3-PbZrO_3 $ (PNN-PT-PZ) ceramics were produced in order to use them as a bimoph acturator for energy harvesting. Especially, the 0.25 wt% $Fe_2O_3$ added 0.4PNN-0.357PT-0.243PZ, having the composition of morphotropic phase boundary, showed good piezoelectric properties of $d_{33}$ of 810 pC/N, $k_p$ of 77% and $Q_m$ of 55 along with a high Curie temperature of $210^{\circ}C$. A bimorph actuator, composed of the two piezoelectric layers bonded together with a phosphorous bronze layer as a central metallic electrode, was successfully fabricated. The bimorph actuator, vibrated with a 1.3 mm amplitude at 68 Hz, produced high electric power of approximately 60 mW.