• Resources Recycling
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• v.7 no.4
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• pp.50-54
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• 1998

In order to obtain desired electromagnetic propertieι high initial permeability and good frequency dependance of initial p permeability, the adding effects of sevral seeds were experimented in Mn-Zn ferrite system. As adding seed grams, calcined at sintering temperature, abnormal grains were disappeared clearly but the density and the initial permcability of sintered Mn-Zn ferrite body were decreased. On the contrary, in case of adding seed rains which were calcined below the calcination temperatnre of matrix particle, abnormal grains remained but the initial permeability was increas$\xi$d with proper s$\xi$ed content. W With proper seed content, the initial permeability was increased by 10-20% but tbe $\alpha$ltoff frequency was not changed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.280-283
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• 1996

The electrical inductivity decreases when the content of NiO is used within 1 at% and increases when it's used more than that. Impedance spectrum seems to be one semicircle. The size of semicircle increases when the content of NiO is sued within 1 at% and decreases when it's used mor than that.

• 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.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.24 no.1
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• pp.27-34
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• 2018

In this work, nano ZnO was introduced into low density poly ethylene (LDPE) composites films with various contents (0, 0.5, 1.0, 3.0 and 5.0 wt%) by melt-extrusion. Their basic properties such as crystallinity, chemical bonds and surface morphology were examined by XRD, FTIR and SEM. XRD patterns and FTIR peaks intensity were increased in proportion to the ZnO contents. SEM images showed well dispersed nano ZnO in LDPE composite films. Antimicrobial functionality of LDPE-nano ZnO composite films was also studied and the presence of nano ZnO resulted in significant improvement of antimicrobial functionality compared to the pure LDPE film. To evaluate influence of nano ZnO on LDPE properties required as packaging material, thermal, mechanical, gas barrier and optical properties of LDPE-nano ZnO composite films were characterized with various analytical techniques including TGA, UTM, OTR, WVTR and UV-Vis spectroscopy. As a result, except optical and mechanical properties of LDPE, no significant effects were found in other properties. Opacity of pure LDPE was greatly increased with increasing concentration of nano ZnO and tensile strength was also improved at 0.5wt% ZnO content.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.4
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• pp.177-184
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• 2022

The present study aims to investigate the influence of Zn addition on hardness and microstructural characteristics of discontinuous precipitates (DPs) formed by isothermal aging in Mg-9%Al and Mg-9%Al-1%Zn alloys. To obtain large DPs volume fractions in the microstructure, the alloy specimens were solution-treated at 688 K for 24 h followed by water quenching, and then aged at 413 K for 48 h. The aged Mg-9%Al-1%Zn alloy had higher DPs content than the Mg-9%Al alloy, indicating that the Zn addition plays a beneficial role in enhancing age-hardening response. The DPs in the Zn-containing alloy possessed the higher hardness than those of the Zn-free alloy. Microstructural examination revealed that the increased hardness of the DPs resulting from the Zn addition is closely associated with the lower α-(Mg)/β(Mg₁₇Al₁₂) interlamellar spacing and the higher volume fraction of β phase layer of the DPs.

• Journal of Powder Materials
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• v.21 no.6
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• pp.460-466
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• 2014

Al-Si-SiC composite powders with intra-granular SiC particles were prepared by a gas atomization process. The composite powders were mixed with Al-Zn-Mg alloy powders as a function of weight percent. Those mixture powders were compacted with the pressure of 700 MPa and then sintered at the temperature of $565-585^{\circ}C$. T6 heat treatment was conducted to increase their mechanical properties by solid-solution precipitates. Each relative density according to the optimized sintering temperature of those powders were determined as 96% at $580^{\circ}C$ for Al-Zn-Mg powders (composition A), 97.9% at $575^{\circ}C$ for Al-Zn-Mg powders with 5 wt.% of Al-Si-SiC powders (composition B), and 98.2% at $570^{\circ}C$ for Al-Zn-Mg powders with 10 wt.% of Al-Si-SiC powders (composition C), respectively. Each hardness, tensile strength, and wear resistance test of those sintered samples was conducted. As the content of Al-Si-SiC powders increased, both hardness and tensile strength were decreased. However, wear resistance was increased by the increase of Al-Si-SiC powders. From these results, it was confirmed that Al-Si-SiC/Al-Zn-Mg composite could be highly densified by the sintering process, and thus the composite could have high wear resistance and tensile strength when the content of Al-Si-SiC composite powders were optimized.

• Journal of the Korean Magnetics Society
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• v.6 no.6
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• pp.382-387
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• 1996

The characteristics of the complex permeability of ${(Ni_{x}Cu_{0.2}Zn_{0.8-x}O)}_{1-w}{(Fe_{2}O_{3})}_{1+w}$ with various Ni and $Co_{3}O_{4}$ contents were investigated in this work. It is found that the NiCuZn ferrites with $x{\geq}0.6$ have a relatively small peak width of the imaginary part of permeability $\mu$". The resonance frequency is increased as Ni content becomes higher, where the loss is low. The $\mu$" value decreases with increasing FezO, deficiency, but the resonance frequency($f_{\mu"max}$) is only slightly affected by $Fe_{2}O_{3}$ deficiency. In case of $Co_{3}O_{4}$ addition to the NiCuZn ferrites, the $f_{\mu"max}$ increases since the initial permeability decreases with the amount of $Co_{3}O_{4}$. It is concluded that the Ni content in the NiCuZn ferrite is a dominant factor for the total loss of these spinel ferrites.

• Journal of Hydrogen and New Energy
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• v.29 no.6
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• pp.549-558
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• 2018

The overall efficiency depend on the overpotential of the oxygen evolution reaction in alkaline water electrolysis. Therefore, it is necessary to research to reduce the oxygen evolution overpotential of electrodes. In this study, Ni-Zn-Fe electrodes were prepared by electroplating and the surface area was increased by Zn leaching process. Electroplating variables were studied to optimize the plating parameters(electroplating current density, pH value of electroplating solution, Ni/Fe content ratio). Ni-Zn-Fe electrode, which is electroplated in a modified Watts bath, showed 0.294 V of overpotential at $0.1A/cm^2$. That result is better than that of Ni and Ni-Zn plated electrodes. As the electroplating current density of the Ni-Zn-Fe electrode increased, the particle size tended to increase and the overpotential of oxygen evolution reaction decreased. As reducing pH of electroplating solution from 4 to 2, Fe content in electrode and activity of oxygen evolution reaction decreased.

• Korean Journal of Materials Research
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• v.27 no.5
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• pp.242-247
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• 2017

ZnO film was prepared on a p-type Si wafer and then annealed at various temperatures in air and vacuum conditions to research the electrical properties and bonding structures during the annealing processes. ZnO film annealed in atmosphere formed a crystal structure owing to the suppression of oxygen vacancies: however, ZnO annealed in vacuum had an amorphous structure after annealing because of the increment of the content of oxygen vacancies. Schottky contact was observed for the ZnO annealed in an air. O 1s spectra with amorphous structure was found to have a value of 529 eV; that with a crystal structure was found to have a value of 531.5 eV. However, it was observed in these results that the correlation between the electronic characteristics and the bonding structures was weak.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.303-305
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• 1996

The electrical Properties of ZnO added TiO$_2$were investigated by using the complex impedance measurement and voltage-current source and measurement unit. The electrical conductivity of ZnO added TiO$_2$decrease with increasing the content of ZnO. The frequency-dependent Ac conductivity increase as frequency increase. Also, the trend of capacitances is similar to the AC conductivity. The semicircles of impedance spectrum increase with increasing ZnO contents. The decrease of electrical conductivity seems to be the effect of ZnO acceptor adding.