• Proceedings of the Korean Magnestics Society Conference
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• 1998.10a
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• pp.94-94
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• 1998

• Journal of Powder Materials
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• v.10 no.5
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• pp.305-309
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• 2003

We report on the formation and chemical leaching of non-equilibrium $Al_{0.6}(Fe_{75}Co_{25})$ alloy produced by rod milling. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry, scanning electron microscopy, and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h, only the $Al_{0.4}Fe_{0.6}$ peak of the body-centered cubic type was present in the XRD pattern. The entire rod milling process could be divided into three different stages of milling: agglomeration, disintegration, and homogenization. The saturation magnetization, $M_s$ decreased with increased milling time, the $M_s$ of the powders before milling was about 113.8 emu/g, the $M_s$ after milling for 400 h was about 11.55 emu/g. Leaching of the Al in KOH of the Al at room temperature from the as-milled powders did not induce any significant change in the diffraction pattern. After the leached specimen had been annealed at $600^{\circ}C$ for 1 hour, the nanoscale crystalline phases were transformed into the bcc Fe, cubic Co, and $CoFe_2O_4$ phases. On cooling the specimen from 85$0^{\circ}C$, the degree of magnetization increased slightly, then increased sharply at approximately 364.8$^{\circ}C$, indicating that the bcc $Al_{0.4}Fe_{0.6}$ phase had been transformed to the Fe and Co phases.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.411-414
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• 2005

It is reported that $\varepsilon$ (HCP) and $\gamma$ (FCC) phases of a Fe-17Mn alloy transform to $\alpha'$ phase, which has BCC structure, under a deformation condition. In this study, we investigated the effect of strain-induced-transformed $\alpha'$ phase on sliding wear of the Fe-17Mn alloy that originally had e and y phases. Wear tests of the materials were carried out using a pin-on-disk wear tester at various loads of 0.5N-50N under a constant sliding speed condition of 0.38m/s against glass $(83\%\;SiO_2)$ beads. The sliding distance and radius were loom and 9 mm, respectively. Wear rate of the Fe-17Mn alloy was calculated by dividing the weight loss, measured to the accuracy of $10^{-5}g$ by the measured specific gravity and sliding distance. Worn surface and wear debris of the specimens were examined using an SEM and XRD. During the wear, $\alpha'$ phase of BCC structure was formed by strain-induced transformation when the applied wear load exceeded critical values. The $\alpha'$ phase formed by the strain induced transformation increased the wear rate of the Fe-17Mn alloy.

• Journal of the Korean Magnetics Society
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• v.24 no.2
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• pp.35-40
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• 2014

We investigate magnetism and magnetocrystalline anisotropy of CoFe thin films, using VASP code in GGA. In this study Co-terminated and Fe-terminated 5-layer CoFe thin films are employed. The Co-terminated CoFe thin film shows two total energy minima at 2-dimensional lattice constants of $2.45{\AA}$ and $2.76{\AA}$. The film of $2.45{\AA}$ has fcc-like structure and the film of $2.76{\AA}$ has bcc-like structure similarly to a bulk CoFe alloy. And the fcc-like film is more stable by the energy difference of about 160 meV compared to the bcc-like film. The Fe-terminated CoFe film shows very complicated behaviour of total energy which is suspected to be closely related to its complex magnetic structure. The Co-terminated CoFe film of $2.76{\AA}$ shows perpendicular magnetocrystalline anisotropy (MCA), while the film of 2.45 does parallel MCA. The Fe-terminated CoFe film also exhibits similar MCA behaviour.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.491-495
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• 1995

The crystallization behaviors and magnetic properties for $Fe_{81-x}Al_{4}B_{10}Zr_{5}Cu_{x}$ (x=0, 1, 2 at%) alloys is investigated. By the addition of 1~2 Cu, the temperature range, where a single bcc phase exists, expands largely over 200 K and the grain size of bcc phase represents to less than 10 nm. For the optimally annealed Cu-added alloys, the high $\mu_{e}$ (1 kHz) above 20000 combined with the high $B_{10}$ of about 1.4 T is obtained in nanocrystalline state. The low core loss of 95.8 W/kg at 0.1 T and 100 kHz is confirmed for the nanocrystalline $Fe_{80}Al_{4}B_{10}Zr_{5}Cu_{1}$ alloy.

• Journal of Hydrogen and New Energy
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• v.18 no.3
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• pp.250-255
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• 2007

Hydrogen storage properties of $Ti_{0.32}Cr_{0.43-X}V_{0.25}M_X$($0{\leq}X{\leq}0.1$, M=Fe, Mn, Si) have been investigated. With varing of Mn content, the lattice parameter of the alloy was unchanged and similar to that of $Ti_{0.32}Cr_{0.43}V_{0.25}$ alloy. With increase of Fe, Si content, the lattice parameters of the BCC phases decreased. When the Fe content was 8 at%, the desorption plateau pressure increased to several atmospheres without decrease of the effective hydrogen storage capacity of the alloy. When the Mn content was 8 at%, the effective hydrogen storage capacity showed approximately 2.5 wt% without change in the desorption plateau pressure. With increase of Si content, hysteresis increased and hydrogen storage capacity decreased rapidly. A study was also made on how desorption temperature affected the usable hydrogen of the $Ti_{0.32}Cr_{0.35}V_{0.25}Mn_{0.08}$ alloy. The temperature was varied from 293 to 413 K, and the pressure from 5 to 0.002 MPa. The usable hydrogen of the alloy was 2.7 wt% when absorbed and desorbed at 293 K and 373 K., respectively. The heat of hydride formation of the alloy was approximately -35.5 kJ/mol $H_2$.

• Transactions of Materials Processing
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• v.19 no.6
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• pp.357-362
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• 2010

Dry sliding wear behavior of pure Fe and Cu which have BCC and FCC crystal structure, respectively, was investigated. The wear characteristics of the pure metals with different crystal structure were compared. Dry sliding wear tests were carried out using a pin-on-disk wear tester at various loads under the constant sliding speed condition of 0.15 m/s against a silica ball at room temperature. Sliding distance was fixed as 600 m for all wear tests. Wear rate of a specimen was calculated by dividing the weight loss of the specimen after the test by the specific gravity and sliding distance. Worn surfaces and wear debris were analyzed by SEM. The wear of both pure Fe and Cu proceeded with surface deformation, resulting in similar wear rates despite of their structure difference under the current test conditions. Wear rates of both metals were low if the surface deformation due to wear forms thick surface-deformation layer that is strain hardened beneath the wearing surface. The pure Cu specimens showed a lot of oxides on the worn surface when tested at low loads less than 5 N, which resulted in very low wear rate.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.241-245
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• 2005

CoFeNi alloys are some of the most studied soft magnetic materials because of their applications as write-head core materials in HDD and MEMS. Ternary CoFeNi films with high saturation magnetic flux density, Bs and low coercivity, He were successfully grown by electrodeposition. The optimal composition was $Co_{30}\;Fe_{34}\;Ni_{36}(at\%)$, and Bs and Hc were 1.9 T and 0.16 A/m, respectively. The XRD and TEM results show that the low Hc of the CoFeNi films was due to very fine crystal particles and mixed fcc and bcc phases.

• Journal of the Korean Magnetics Society
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• v.9 no.6
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• pp.285-290
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• 1999

The magnetic properties of sputtered amorphous $Fe_{86.7}Zr_{3.3}B_4Ag_6$ thin films, which contains an additional insoluble element Ag, have been investigated as a function of uniaxal field annealing temperature. The amorphous $Fe_{86.7}Zr_{3.3}B_4Ag_6$ thin films produced by relatively low temperature annealing at 40$0^{\circ}C$ for 1 hour was found to have very high permeability of 7800 at 50 MHz, 0.2 mOe, high magnetization of 1.7 T, low coercivity of 1.0 Oe and very low core loss of 1.4 W/cc at 1 MHz, 0.1 T, respectively. It is notable that the permeability and core loss values for various kinds of the soft magnetic thin films reported up to now. The reason for the appearance for the good soft magnetic properties is presumably due to the homogeneous formation of very fine bcc $\alpha$-Fe clusters with the size in the amorphous $Fe_{86.7}Zr_{3.3}B_4Ag_6$ thin films matrix, which can be deduced from the XRD results.

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.249-254
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• 2006

CoFeNi alloys are some of the most studied soft magnetic materials because of their superial properties over FeNi alloys as write head core materials in HDD and MEMS. We studied the effect of magnetic property according to size and orientation of crystal for electroplated Co-Fe-Ni alleys. In case of heat treated ternary alloy, it affect the change of crystal size and structure. In this study, it intends to improve the magnetic properties of CoFeNi thin film by heat treatment. Minimized coercivity and increased magnetization are due to heat treatment from $300^{\circ}C\;to\;400^{\circ}C$. As a bcc phase formation, it grow to amount of magnetization.