• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.149-154
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• 2000

In this paper, we studied the relation between addition of carbon and electromagnetic wave absorbing properties of ferrite-rubber composite. The ratio of carbon was 7 wt%. As s result, it has been shown that the electromagnetic wave absorbing properties of ferrite-rubber composite are changed by the addition of carbon in composite. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the using of carbon.

• Journal of the Korean Magnetics Society
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• v.5 no.6
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• pp.928-936
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• 1995

In this research, the processing control of NiCuZn Ferrite has been developed. The mixing and the size reduction of raw materials have been proceeded. In order to produce NiCuZn Ferrite, highly concentrated slurry with fixed ratio and wet ball milling were used. First, the dispersion behavior of raw mixture at the region of pH4~pH11 has been studied. Using wet ball milling operation, the best conditions of mixing and size reduction have been determined. Further more, the most suitable conditions, such as, dispersant kind, dispersant amount, milling time, and slurry concentration have been studied. The poly acrylic ammonium salt (PAN) was chosen as a suitable dispersant to have effective dispersion in basic region. The slurry of raw mixture without dispersant, showed high viscosity and poor grindability. As 0.7 wt% of PAN was added, the concentrated slurry (up to 55 vol%) was possible, and showed well grindability. After 18 h ball milling of 30 vol% of mixture slurry with 0.7 wt% of PAN, the average particle size and specific surface area of raw mixture were $0.54\mu\textrm{m}$ and $12.92m^{2}/cc$, respectively. The ball milled raw mixture, calcined at $700^{\circ}C$ for 3h, was totally changed into NiCuZn Ferrite with spinel phase.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.5
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• pp.994-1000
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• 2001

With the development of electromagnetic communication technology and increased use of electromagnetic wave, the countermeasure of EMI(Electromagnetic Interference) becomes more important socially, and interest for the electromagnetic wave absorber has also increased. In this paper, we have studied characteristics of frequency dependency on complex permittivity and complex permeability according to the changes of composition rate and sintering temperature of NiCuZn ferrite also known as electromagnetic wave absorber and further looked into effect of electromagnetic wave absorption properties. From the measurement where the composition of $Fe_2O_3$ and ZnO of NiCuZn ferrite was fixed at 49 and 34 mol% respectively while composition of NiO and CuO has been varied at each test, we found out that Initial permeability and permittivity were high and the absorbing ability of electromagnetic wave recorded best with $loss tangent(=\mur"/\mur')$ displays more than 1 within the frequency band of 2MHz~9.5MHz when the composition ratio of NiO was ranged around 8.5~9.5 mol% and the sintering temperature was $1080^{\circ}C$.TEX>.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.222-224
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• 1993

In this paper, The optimum oxidation conditions for the formation of Cu-Zn ferrite were investigated using precipitates obtained by the mixture of $CuCl_2{\cdot}2H_2O$, $ ZnCl_2$, $FeCl_3{\cdot}6H_2O$ and NaOH. The precipitates were prepared by coprecipitation method on various temperatures and oxidation conditions. The oxidation products were examined by SEM, XRD, and VSM. The particles obtained at 70($^{\circ}C$) were more spherical and fine than that of prepared at 25($^{\circ}C$), 50($^{\circ}C$), 60($^{\circ}C$), respectively. By $H_2O_2$ oxidation, the saturation magnetization of the powders was little influenced, But, by air oxidation the saturation magnetization of the powders was influenced intricately. According to our experimental data, the saturation magnetization of the powders increased with reaction time and was saturated at 9 hours.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.112.2-112
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.110-111
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• 2003

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1119-1123
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• 2002

Nanostructured spinel NiZn ferrites were prepared by the sol-gel method from metal nitrate raw materials. Analyses by X-ray diffraction and scanning electron microscopy showed the average particle size of NiZn ferrite was under 50 nm. The single phase of NiZn ferrites was obtained by firing at 250${\circ}C$, resulting in nanoparticles exhibiting normal ferrimagnetic behavior. The nanostructured $Ni_{1-X}Zn_XFe_2O_4$ (x=0.0∼1.0) were found to have the cubic spinel structure of which the lattice constants ${\alpha}_2$ increases linearly from 8.339 to 8.427 ${\AA}$ with increasing Zn content x, following Vegard's law, approximately. The saturation magnetization $M_s$ was 48 emu/g for x=0.4 and decreased to 8.0 emu/g for higher Zn contents suggesting the typical ferrimagnetism in mixed spinel ferrites. Pure NiZn ferrite phase substituted by Cu was observed before using the additive but hematite phase was partially appeared at $Ni_{0.2}Zn_{0.2}Cu_{0.6}Fe_2O_4$. On the other hand, the hematite phase in this NiZn Cu ferrite was disappeared after using the additive of acethyl aceton with small amount. The saturation magnetization Ms of $Ni_{0.2}Zn_{0.8-y}Cu_yFe_2O_4$(y=0.2∼0.6) as measured was about 51 emu/g at 77K and 19 emu/g at room temperature, respectively.

• Journal of Magnetics
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• v.12 no.4
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• pp.161-164
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• 2007

Constant temperature regulation of a hybrid heater which is composed of a temperature sensitive ferrite with low permeability and a Cu tube is investigated for hyperthermia. The temperature sensitive ferrite is inserted into a Cu tube and its length and diameter are 10 mm and 3 mm. Below B=0.05 T, the measured temperature and the calculated one increased with the ratio of $B^{1/2}$ and agreed well with each other. Above B=0.05 T, the measured temperatures maintained constantly almost $50^{\circ}C{\pm}1.5^{\circ}C$ because of the influence of Curie temperature of the temperature sensitive ferrite. This result shows that the hybrid heater is able to regulate the temperature constantly at the rate of $50^{\circ}C{\pm}1.5^{\circ}C$.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.225.2-225
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• 2003

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.71-77
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• 1999

In this study, Cu ferrite was machined with cermet tool to clarify the machinability. The main conclusions obtained were as follows. The tool wear becomes the smallest at the cutting speed of 90m/min with the depth of cut of 0.2mm. The surface roughness becomes larger with increasing the cutting speed and the chamfer angle. The tool with the chamfer angle of $15{\circ}$ shows the best performance. The surface roughness increases almost proportionally with the increase of the chip size. The tool wear decreases with increasing feed in the depth of cut not more than 0.2mm.