• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.12
• /
• pp.1329-1334
• /
• 2003

We prepared EM wave absorbers by using recycled Ba ferrite far GHz frequency, and investigated the effects of carbon additions and preparation temperatures on their EM wave absorption properties. We clarified that it is very important to consider carbon amounts in Ba ferrite and preparation temperature for Ba ferrite EM wave absorbers with high quality.

• Journal of Navigation and Port Research
• /
• v.28 no.10 s.96
• /
• pp.861-867
• /
• 2004

Generally, a silicone rubber and a chloride polyethylene(CPE) have been used as a binder for high-performance composite EM( Electromagnetic) wave absorbers. In this study, the EM wave absorption abilities for natural lacquer which is newly suggested as a binder were investigated MnZn ferrite composite EM wave absorbers mixed with the natural lacquer were prepared and their absorption ability was also investigated. The prepared MnZn ferrite composite EM wave absorbers mixed with natural lacquer showed an improved EM wave absorption characteristics compared with MnZn ferrite EM wave absorbers mixed with the conventional binders. such as a silicone rubber and a chloride polyethylene(CPE). The matching frequency and the absorption ability of EM wave absorbers varied with the thickness of them.

• Journal of the Korean Magnetics Society
• /
• v.17 no.6
• /
• pp.238-241
• /
• 2007

Ni-Cu-Zn ferrites were prepared by the co-precipitation. Physical properties and Microwave absorbing properties were investigated in Ni-Cu-Zn ferrite for the aim of microwave absorbers. From the analysis of X-ray diffraction patterns, we can see that all the particles have only a single phase spinel structure. The loss factor was maximum at sintering temperature $1100^{\circ}C$. The initial permeability of sintered ferrite obtained was an average of 50. We found that the $(Ni_{0.7}Cu_{0.2}Zn_{0.1}O)_{1.02}(Fe_2O_3)_{0.98}$ can be used in ferrite rubber composite microwave absorber when sintering temperature at $1100^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.29 no.3
• /
• pp.177-182
• /
• 1992

The effect of heat-treatment temperature on the microwave absorbing properties was investigated in Ni0.8Zn0.2Fe2O4 specimens. The composite specimens were prepared by modling and curing the mixture of prereacted ferrite powder and silicone rubber. The measurement of complex permeability and permittivity was made by the reflection/transmission method. The most sensitive material constants with heat-treatment temperature is the imaginary (loss) component of permeability. The higher the heat-treatment temperature, the greater the magnetic loss. The composite specimens with high magnetic loss exhibited superior microwave absorbing properties. The quantitative estimation of microwave absorbing properties were made by plotting the observed material constants on the calculated solution map of impedance-matching.

• Proceedings of the KIEE Conference
• /
• 2001.07e
• /
• pp.86-89
• /
• 2001

In this paper, the composite damping sheet with electromagnetic wave absorption was developed and studied. The damping sheets with Ni-Zn ferrite, Mn-Zn ferrite and PZT were prepared by mixing, molding and drying. From the characterizing results, the optimal portion of the composite is 1:1:0.1 of Mn-Zn ferrite:Rubber:PZT. The maximum absorption was -30 dB at 860 MHz in the single structure and over -15 dB at 180 MHz and 860 MHz in the two or three layers.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2017.05a
• /
• pp.114-114
• /
• 2017

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.6
• /
• pp.1002-1008
• /
• 2001

The absorbing structure composed of multi-layered fiber reinforced composite materials was designed and microwave absorbing properties are investigated. On the basis of transmission line theory, the theoretical equations to predict the reflection loss and the appropriate composite material for each functional layer are suggested. The most significant result of this study is the successful design and fabrication of triple-layered composite laminates which has the superior microwave absorbing porperties (more than 10 dB in 4∼12 GHz range), without using the ferrite filler in the impedance transforming layer. In the two-layered composite laminate (absorber/substrate), however, the use of ferrite filler (about 40 wt %) in the absorbing layer is necessary to obtain the certain level of microwave absorbance. By combining the glass-fiber composite with ferrite filler and carbon-fiber composite substrate, the microwave absorbing properties more than 10 dB in 4∼12 GHz frequencies than be obtained.

• Proceedings of the KIEE Conference
• /
• 1992.07b
• /
• pp.724-726
• /
• 1992

In this paper, the permeability ($\mu_{\tau}'$, $\mu_{\tau}''$), dielectric constants($\varepsilon_{\tau}'$, $\varepsilon_{\tau}''$) and absorbption characteristics of Ferrite/Rubber 0-3 composites were investigated. The composite specimens were prepared by molding and curing the mixtures of matrix rubber and Ni-Zn ferrite powders which were synthesized by wet-direct method. The permeability ($u_{\tau}'$) of specimen was decreased from 2.58 to 0.7 in the range of 1$\sim$7(GHz) and kept constant 0.7$\sim$0.8 at higher than 7(GHz), the higher the frequency was, the less the valves of $u_{\tau}"$ was from 1.57 to 0.03. The optimum thickness of microwave absorber, utilizing the Smith chart, was 5(mm). The reflection loss shows over than 20(dB) from 5.5(GHz) to 7.5(GHz) at 5(mm) thickness and relative band width(B/fm) was about 30%.

• Journal of the Institute of Electronics Engineers of Korea TE
• /
• v.37 no.2
• /
• pp.91-95
• /
• 2000

A new damping composite materials with asphalt and EM absorber are studied for high advantage values. The composite Ni-Zn ferrite and dielectric PZT with a main material is well developed of EM absorbing, and is continuous maintained of origin character, damping absorbing. Experiments and calculation results are shown to act two points frequencies at 928MHz and from 2MHz to 4GHz below -l0dB The narrow band widths of ferrite change to broad band as insert of dielectric material, PZT good of EM wave absorbtion and broad band widths in multi layers with ferrite These are applied to develop of new material at new need frequencies.

• Journal of Electrochemical Science and Technology
• /
• v.2 no.1
• /
• pp.32-38
• /
• 2011

The composite barium strontium cobalt ferrite (BSCF) cathodes were investigated in the intermediate temperature range of solid oxide fuel cells (SOFCs). The characteristics and electrochemical performances of composited BSCF/samarium doped ceria (SDC); BSCF/gadolinium doped ceria (GDC); and BSCF/SDC/GDC were compared to single BSCF cathode. The BSCF used in this study were synthesized using glycine nitrate process and mechanically mixing was used to fabricate a composite cathode. Using a composite form, the thermal expansion coefficient (TEC) could be reduced and BSCF/SDC/GDC exhibited the lowest TEC value at $18.95{\times}10^{-6}K^{-1}$. The electrochemical performance from half cells and single cells exhibited nearly the same trend. All the composite cathodes gave higher electrochemical performance than the single BSCF cathode (0.22 $Wcm^{-2}$); however, when two kinds of electrolyte were used (BSCF/SDC/GDC, 0.36$Wcm^{-2}$), the electrochemical performance was lower than when the BSCF/SDC (0.45 $Wcm^{-2}$) or BSCF/GDC (0.45 $Wcm^{-2}$) was applied as cathode ($650^{\circ}C$, 97%$H_2$/3%$H_2O$ to the anode and ambient air to the cathode).