• Journal of the Korean Magnetics Society
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• v.21 no.2
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• pp.77-82
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• 2011

The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-to-particle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.4
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• pp.259-269
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• 2013

Applicability of ammonium molybdophosphate/iron oxides-polyacrylonitrile (AMP/IO-PAN) composites on the removal of radionuclides in the radioactive wastewater generated from nuclear power plants was investigated. The composites were characterized using the following analytical techniques: X-ray diffraction (XRD), Fourior transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), particle size analyzer (PSA), nitrogen adsorption-desorption and magnetic property measurement system (MPMS). 10wt% of AMP/IO-PAN composite has a saturation magnetization of 2.038 emu/g. Single-solute sorptions of Co, Sr and Cs onto 10wt% of AMP/IO-PAN composite were investigated. The maximum sorption capacities ($Q^0$) predicted by the Langmuir model on 10wt% of AMP/IO-PAN composite were 0.097, 0.086 and 0.66 mmol/g for Co, Sr and Cs, respectively. The maximum sorption capacities ($Q^0$) of Cs predicted by Langmuir model on 0, 10, 20 and 30wt% of AMP/IO-PAN composites were 0.702, 0.655, 0.602 and 0.559 mmol/g, respectively. The maximum sorption capacities ($Q^0$) of Cs decreased with increasing the iron oxide content in the AMP/IO-PAN composites.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.667-684
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• 2020

In this article, the static responses of layered magneto-electro-thermo-elastic (METE) plates in thermal environment have been investigated through FE methods. By using Reddy's third order shear deformation theory (TSDT) in association with the Hamilton's principle, the direct and derived quantities of the coupled system have been obtained. The coupled governing equations of METE plates have been derived through condensation technique. Three layered METE plates composed of piezoelectric and piezomagnetic phases are considered for evaluation. For investigating the correctness and accuracy, the results in this article are validated with previous researches. In addition, a special attention has been paid to evaluate the influence of different electro-magnetic boundary conditions and pyrocoupling on the coupled response of METE plates. Finally, the influence of stacking sequences, magnitude of temperature load and aspect ratio on the coupled static response of METE plates are investigated in detail.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1712-1719
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• 2015

In recent days, there was a significant development on the electrical, thermal, mechanical, physical, chemical, magnetic and optical properties of the polyamide enamel, varnish and other insulating materials by the addition of nano fillers to it. Enamel was used in High Voltage Apparatuses used in Medical Electronics as insulation. Insulating materials determine the life time of the electrical apparatuses. The life time of the insulating materials was improved by the addition of nano fillers to it. Hence the life time of the electrical apparatuses was improved by the mixing of nano fillers to the enamel. In this research, the basic dielectric properties of the enamel and enamel mixed with nano composites of silica and alumina were analyzed and compared with each other. The addition of nano fillers has improved the quality factor and capacitance of the enamel. It was also observed that the addition of nano fillers has reduced the dissipation factor and dielectric losses of the enamel. Heat produced by the dielectric losses was also reduced by adding nano fillers to it.

• Journal of the Korean Magnetics Society
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• v.7 no.6
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• pp.285-292
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• 1997

We have studied magnetoelectric effect with cobalt ferrite-Pb(Zr, Ti) $O_3$ composites made by solid state reaction. The maximum magnetoelectric voltage coefficient, $(dE/ dH)_{max}$, increased with longer sintering time and higher volume fraction of the cobalt ferrite. The magnetic field for $(dE/ dH)_{max}$ became lower with increasing the sintering time and decreasing the volume fraction of the cobalt ferrite. The phenomena were explained in terms of grain size change, mechanical coupling efficiency, easiness of magnetization and polarization. We obtained the highest magnetoelectric voltage coefficient of 0.174V/cm-Oe, which is about 30% higher than the best value reported.

• Advances in concrete construction
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• v.8 no.4
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• pp.311-320
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• 2019

In this study, the effect of cellulose nanocrystals (CNCs) on the fire resistance properties of fiber-reinforced cement composites was investigated. The main variables were CNCs content (0.4, 0.8 and 1.2vol.% compared with cement), steel fiber ratio, and exposure temperature (100, 200, 400, 600 and 800℃). The fire resistance properties, i.e., residual compressive strength, flexural strength, and porosity, were evaluated in relation with the exposure temperature of the specimens. The CNCs suspensions were prepared to composited dispersion method of magnetic stirring and ultra-sonication. CNCs are effective for increasing the compressive strength at high temperatures but CNCs do not seem to have a significant effect on flexural reinforcement. Porosity test result showed CNCs reduce the non-hydration area inside the cement and promote hydration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.228-234
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• 2005

A magnetic composite as noise absorber of quasi-microwave band was developed. The Fe-Si-Al alloy powder were forged by attrition mill to get flaky shape. The magnetic composite sheet was fabricated in which powders are dispersed in polymer and aligned in the direction perpendicular to electromagnetic wave propagation. The permittivity of magnetic composite is increased as forging time increasing, while the permeability is decreased slightly. The maximum attenuation peak of reflection loss is shifted to lower fiequency range as milling time increasing, and the value of maximum attenuation peak is to get smaller gradually. From these result, we could designed a noise absorber sheet (t=1.0 mm) for quasi-microwave band, which is impedance matched at 1.4 GHz with respect to -8.2 dB reflection 1055.

• Journal of Magnetics
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• v.19 no.3
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• pp.221-226
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• 2014

Significantly enhanced low-field magnetoresistance (LFMR) and maximum dMR/dH {$(dMR/dH)_{max}$} values were successfully achieved from $La_{0.7}Sr_{0.3}MnO_3$(LSMO)-manganese oxide composite samples prepared by liquid phase sintering, compared with those of the same composites prepared by solid state reaction. For this study, pure LSMO and LSMO-manganese oxide composites with various nominal compositions of (1-x)LSMO-$xMn_2O_3$ (x = 0.1, 0.2, 0.3, 0.4, and 0.8) were sintered at $1450^{\circ}C$, above the eutectic temperature of $1430^{\circ}C$, for 1 h in air. The highest LFMR value of 1.28% with the highest $(dMR/dH)_{max}$ value of 21.1% $kOe^{-1}$ was obtained from the composite sample with x = 0.3 at 290 K in 500 Oe. This enhancement of LFMR and $(dMR/dH)_{max}$ values is ascribed to efficient suppression of magnetic disorder at the LSMO grain boundary, by forming a characteristic LSMO-manganese eutectic structure.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.1
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• pp.17-25
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• 1993

The Cu - $Nb_3Sn$ composites wire as a superconducting material was prepared by in situ method as follow: Cu - 15wt.% Nb alloys which were melted in a high -frequency induction furnace and casted in bar were cold-worked up to the final diameter of 0.24 mm, electroplated with Sn, pre-treated in two steps and then diffused at $550{\sim}650^{\circ}C$ for 24 ~ 96 hrs. The overall $J_c$ and $T_c$ of the specimens were measured by the four point-probe method at 10 K in the magnetic field of 0 Tesla. The overall $J_c$ of the composites wire which diffused at $550^{\circ}C$ after pre-treating in two steps were generally higher than those of the wire at either $600^{\circ}C$ or $650^{\circ}C$. For the specimens diffused at $550^{\circ}C$, the overall $J_c$ were increased until 72 hrs. of diffusion time and then decreased. However, in case of diffusion at $600^{\circ}C$ and $650^{\circ}C$, the overall $J_c$ were gradually decreased from the beginning. The maximum overall $J_c$ obtained in this experiment was $1.3{\times}10^4\;A/cm^2$, which was measured for the specimen diffused at $550^{\circ}C$ for 72 hrs. When the specimens were diffused at $550^{\circ}C$ for 72 hrs, after pre-treating, the measured critical temperature, $T_c$ was 16.19 K. Similar $T_c$ value were obtained in other specimens regardless of diffusion time and temperature.

• 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.