• Journal of Powder Materials
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• v.16 no.4
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• pp.249-253
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• 2009

3-D shape soft magnetic composite parts can be formed by general compaction method of powder metallurgy. In this study, the results on the high density nanostructured Fe-Si/Fe composite prepared by a warm compaction method were presented. Ball-milled Fe-25 wt.%Si powder, pure Fe powder and Si-polymer were mixed and then the powder mixture was compacted at various temperatures and pressures. Pore free density of samples up to 95% theoretical value has been obtained. The warm compacted sample prepared at 650 MPa and 240$^{\circ}C$ had highest compaction properties in comparison with other compacts prepared at 300, 400 MPa and room temperature and 120$^{\circ}C$. The magnetic properties such as core loss, magnetization saturation and coercivity were measured by B-H curve analyzer and vibration sample magnetometer.

• Journal of the Korean Society for Heat Treatment
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• v.2 no.2
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• pp.38-45
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• 1989

The Cu-Fe permanent magnet were prepared in situ process, which has economic and mass productive merits in producing multi filamentary composites. The purpose of this research was to study the effect of reduction ratio and heat treatment on magnetic property. As the reduction ratio of Cu-Fe wire increased, the filament structure became finer and interfilament distances decreased and the morphology of filament cross section became ribbon shape. As Fe content increased significantly. The coercivity and squareness of Cu-55 wt%Fe composite increased as a reduction ratio became higher, whereas they increased to maximum values at 0.09 mm ${\phi}$ for Cu-30 wt%Fe, and 0.066 mm ${\phi}$ for CU-45 wt%Fe respectively, and decreased for further reduction. The magnetic properties of Cu-Fe composites can be more enhanced by intermediate heat treatment. The best magnetic properties were obtained from Cu-55 wt%Fe composite deformed to 0.054 mm ${\phi}$ and annealed.

• Journal of Magnetics
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• v.19 no.1
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• pp.55-58
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• 2014

We have synthesized ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}/{\alpha}$-phase $Fe_{65}Co_{35}$ composite by annealing a mixture of paramagnetic ${\varepsilon}$-phase $Mn_{54}Al_{46}$ and ferromagnetic ${\alpha}$-phase $Fe_{65}Co_{35}$ particles at $650^{\circ}C$. The volume fraction ($f_h$) of hard ${\tau}$-phase $Mn_{54}Al_{46}$ of the composite was varied from 0 to 1. During the annealing, magnetic phase transformation occurred from paramagnetic ${\varepsilon}$-phase to ferromagnetic ${\tau}$-phase $Mn_{54}Al_{46}$. The magnetization and coercivity of the composite monotonically decreased and increased, respectively, as the $f_h$ increased. These results are in good agreement with our proposed composition dependent coercivity and modified magnetization equations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.319-324
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• 2013

In this study, an EP (electro-polishing)-MAP (magnetic abrasive polishing) hybrid process was developed as a precision finishing process. To evaluate the characteristics of this EP-MAP hybrid process, a series of experiments were carried out using various working gaps, current densities, and electrolyte concentrations. As a result, $NaNO_3$ was found to be very suitable as the electrolyte of the hybrid process because there was no electrochemical reaction with the CNT-Co composite. Moreover, an increase in the magnetic flux density affected the liquidity of the electrolyte and prevented it from flowing into the CNT-Co composite powder. For that reason, the lower liquidity of the electrolyte increased the thermal energy on the surface of the workpiece.

• Steel and Composite Structures
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• v.25 no.2
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• pp.141-155
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• 2017

This paper presents an investigation into the magneto-thermo-mechanical vibration and damping of a viscoelastic functionally graded-carbon nanotubes (FG-CNTs)-reinforced curved microbeam based on Timoshenko beam and strain gradient theories. The structure is surrounded by a viscoelastic medium which is simulated with spring, damper and shear elements. The effective temperature-dependent material properties of the CNTs-reinforced composite beam are obtained using the extended rule of mixture. The structure is assumed to be subjected to a longitudinal magnetic field. The governing equations of motion are derived using Hamilton's principle and solved by employing differential quadrature method (DQM). The effect of various parameter like volume percent and distribution type of CNTs, temperature change, magnetic field, boundary conditions, material length scale parameter, central angle, viscoelastic medium and structural damping on the vibration and damping behaviors of the nanocomposite curved microbeam is examined. The results show that with increasing volume percent of CNTs and considering magnetic field, material length scale parameter and viscoelastic medium, the frequency of the system increases and critically damped situation occurs at higher values of damper constant. In addition, the structure with FGX distribution type of CNTs has the highest stiffness. It is also observed that increasing temperature, structural damping and central angle of curved microbeam decreases the frequency of the system.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.192-192
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• 2009

Magnetic and magnetotransport properties of (1-x) $La_{0.7}Sr_{0.3}MnO_3-xRE_2O_3$ (RE=La, Nd) (x = 0.025, 0.05, 0.075, 0.1, 0.2, 0.3) composite polycrystalline samples were systematically studied. Samples were prepared using conventional solid-state reaction. LSMO and $RE_2O_3$ react at high temperature and become chemically compatible. The ferromagnetic-paramagnetic transition temperatures ($T_c$) of the LSMO-$Nd_2O_3$ composite samples were decreased 313K~349K with increasing x, while the $T_c$ values of the LSMO-$La_2O_3$ composite samples were almost unaltered in the range of 355K~358K, representing that the ferromagnetism of LSMO might be more seriously degraded by Nd substitution on the ($La_{0.7}Sr_{0.3}$) site. However, LSMO-$RE_2O_3$ composite samples exhibit greatly enhanced low field magnetoresistance (LFMR) and dMR/dH value without an appreciable increase in its resistivity. Remarkably improved LFMR properties are attributed to LSMO grain boundaries acting as effective spin-dependent scattering centers. The relationship among the $RE_2O_3$ addition, microstructure, magnetic and magnetotransport properties will be discussed in this paper.

• Korean Journal of Radiology
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• v.24 no.6
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• pp.512-521
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• 2023

Objective: There is increasing recognition that left atrial (LA) strain can be a prognostic marker of various cardiac diseases. However, its prognostic value in acute myocarditis remains unclear. Therefore, this study aimed to evaluate whether cardiovascular magnetic resonance (CMR)-derived parameters of LA strain can predict outcomes in patients with acute myocarditis. Materials and Methods: We retrospectively analyzed the data of 47 consecutive patients (44.2 ± 18.3 years; 29 males) with acute myocarditis who underwent CMR in 13.5 ± 9.7 days (range, 0-31 days) of symptom onset. Various parameters, including feature-tracked CMR-derived LA strain, were measured using CMR. The composite endpoints included cardiac death, heart transplantation, implantable cardioverter-defibrillator or pacemaker implantation, rehospitalization following a cardiac event, atrial fibrillation, or embolic stroke. The Cox regression analysis was performed to identify associations between the variables derived from CMR and the composite endpoints. Results: After a median follow-up of 37 months, 20 of the 47 (42.6%) patients experienced the composite events. In the multivariable Cox regression analysis, LA reservoir and conduit strains were independent predictors of the composite endpoints, with an adjusted hazard ratio per 1% increase of 0.90 (95% confidence interval [CI], 0.84-0.96; P = 0.002) and 0.91 (95% CI, 0.84-0.98; P = 0.013), respectively. Conclusion: LA reservoir and conduit strains derived from CMR are independent predictors of adverse clinical outcomes in patients with acute myocarditis.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.04a
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• pp.19-19
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• 2001

• Proceedings of the Korean Magnestics Society Conference
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• 2001.10a
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• pp.30-31
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• 2001

• Proceedings of the Korean Magnestics Society Conference
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• 2015.11a
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• pp.176-177
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• 2015