• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.109-114
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• 2000

In this paper, we studied the relation between heat-treatment temperature of ferrite and electromagnetic wave absorbing properties of ferrite-rubber composite. The heat-treatment temperatures of ferrite are 1200 and 1300 $^{\circ}C$, 2 hr. As s result, it has been shown that the optimum heat-treatment temperature of ferrite for electromagnetic wave absorber are related to the chemical composition. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the control of heat-treatment temperature of ferrite.

• Journal of Magnetics
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• v.18 no.4
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• pp.391-394
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• 2013

In this study, nickel-zinc ferrite nanoparticles, with the chemical formula of $Ni_{0.3}Zn_{0.7-x}Cu_xFe_2O_4$ (where x = 0.1- 0.6 by step 0.1), were fabricated by the sol-gel method. The effect of copper substitution on the phase formation and crystal structure of the sample was investigated by X-ray diffraction (XRD), thermo-gravimetry (TG), differential thermal analysis (DTA), Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The XRD result shows that due to the reduction of Zn content,the crystallite size of the sample increased. The results of the vibration sample magnetometer (VSM) exhibit an increase in saturation magnetization value (Ms) for samples with x ${\leq}$ 0.3 and a linear decrease for samples with x > 0.3. The variation of saturation magnetization and coercivity of the samples were then studied.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1245-1252
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• 1996

The charcteristics for the copper-contained spinel ferrites such as NiCu-and ZnCu ferrites with various copper content are investigated in this study which can provide a explanation for the behavior of copper in sintering at a low temperatuer. The bulk density and the grain size for these sintered ferrites were increased with the larger amount of copper in compositions. In microstructure of copper-contained spinel ferrites copper exists in the grain boundary which is sintering process. Electrical resistivity and frequency range with maximum Q-facor of NiCu-or ZnCu ferrites were decreased as increasing of copper content in ferrite composition.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.04a
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• pp.82-83
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• 2002

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.542-542
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• 2006

• Korean Journal of Materials Research
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• v.5 no.5
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• pp.512-517
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• 1995

EMI 대책용 전자파 흡수체로 알려진 cu-Ni-쿠 페라이트를 분말야금법으로 제조하여, 성형압력과 소결온도의 변화에 따른 미세조직을 과낯ㄹ하고, 투과반사법으로 전자파 흡수능을 측정하여 조직과의 관계로 검토하였다. 하소는 공기중에서 90$0^{\circ}C$로 2시간동안 행하는 것이 최적이었다. 미세조직과 입자의 크기는 성형압과 소결온도로 제어할 수 있다. 100Mpa로 성형한 것이 치밀하고, 전자파 흡수특성이 우수하였다. 복소유전율과 복소투자율은 기공도와 소결밀도에 영향을 받았다. 전자파흡수능은 밀도보다는 입자의 크기에 더 큰 영향을 받았다.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.600-607
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• 2002

The Ni-Zn synthetic ferrite were acquired from thermally decomposing the metal nitrates Fe(NO$_3$)$_3$.$9H_2$O, Zn($NO_3$)$_2$.$6H_2$O, Ni($NO_3$)$_2$. $6H_2$O, and Cu($NO_3$)$_2$. $3H_2$O at $150^{\circ}C$ for 24 hours and was calcined at $500^{\circ}C$. Each of those was pulverized for 3, 6, 9, and 12 hours in a steel ball mill and was sintered between $700^{\circ}C$ and $1,000^{\circ}C$ for 1 hour, and then their microstructures and electromagnetic properties were examined. We could make the initial specimens chemically bonded in liquid at the temperature as low as $150^{\circ}C$, by using the melting points less than $200^{\circ}C$ of the metal nitrates instead of the mechanical ball milling, then narrowed a distance between the particles into a molecular level, and thus lowed sintering temperature by at least $200^{\circ}C$ to$ 300^{\circ}C$. Their initial permeability was 50 to 400 and their saturation magnetic induction density and coercive force 2,400 G and 0.3 Oe to 0.5 Oe each, which were similar to those of Ni- Zn ferrite synthesized in the conventional process. In the graph of initial permeability vs frequencies, we could observe a $180^{\circ}C$rotation of the magnetic domain, which appears in a broad band of microwave near the resonance frequency.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.210-210
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.273.1-273.1
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• 2007

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.365-368
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• 2000

We have studies on the Microstructures and densities as a function of forming pressures and the magnetic properties of the specimens with additive Bi$_2$O$_3$ that sintered at 95$0^{\circ}C$ for 4.5 hours for synthesizing optimal Ni-Cu-Zn ferrite. Green density rose generally as Forming pressure increased from 1.7 ton/cm$^2$to 2.5 ton/cm$^2$and Cold Isostatic Pressure(CIP) method was more effective than Die Pressure(DP) method to high green density. Forming pressure had no influence on apparent density but on the other hand Bi$_2$O$_3$contents were strongly dominant to appaernt density than forming pressure. Bi$_2$O$_3$liquid phases created during sintering process promoted sintering and grain growth so that apparent density, grain size and permeability increased compared to that of the specimens which were sintered with non-additive Bi$_2$O$_3$.