• 한국재료학회지
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• 제19권12호
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• pp.680-685
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• 2009

Using a polyurethane foam replica method, porous hydroxyapatite scaffolds (PHS) were fabricated using conventional and microwave sintering techniques. The microstructure and material properties of the PHS, such as pore size, grain size, relative density and compressive strength, were investigated at different sintering temperatures and holding times to determine the optimal sintering conditions. There were interconnected pores whose sizes ranged between about 300 ${\mu}m$ and 700 ${\mu}m$. At a conventional sintering temperature of 1100$^{\circ}C$, the scaffold had a porous microstructure, which became denser and saw the occurrence of grain growth when the temperature was increased up to 1300$^{\circ}C$. In the case of microwave sintering, even at low sintering temperature and short holding time the microstructure was much denser and had smaller grains. As the holding time of the microwave sintering was increased, higher densification was observed and also the relative density and compressive strength increased. The compressive strength values of PHS were 2.3MPa and 1.8MPa when conventional and microwave sintering was applied at 1300$^{\circ}C$, respectively.

• The Korean Journal of Ceramics
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• 제2권2호
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• pp.111-113
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• 1996

Dielectric properties at microwave frequency region of the five-layered compound $Ba_5Nb_4O_{15}$ prepared by the conventional solid state reaction method were investigated. $Ba_5Nb_4O_{15}$ has excellent microwave dielectric characteristics; ${\varepsilon}_r$=38, Q=7500 at 10 GHz, and ${\tau}_l$=+50 ppm/K. Since this compound has a high dielectric constant, high Q and sufficiently stable characteristics, it is useful for the applications at microwave frequencies.

• 대한금속재료학회지
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• 제50권5호
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• pp.389-393
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• 2012

Improvement in microwave absorbance has been investigated by insertion of a periodic air cavity in rubber composites filled with magnetic powders. A mixture of $Co_2Z$ hexagonal ferrite and Fe powders were used as the absorbent fillers in silicone rubber matrix. The complex permeability and complex permittivity of the magnetic composites were measured by reflection/transmission technique. In the grid-type magnetic absorbers, the equivalent permeability (${\mu}_{eq}$) and permittivity (${\varepsilon}_{eq}$) are calculated as a function of air volume rate (K) on the basis of effective medium theory. Reduction in the material parameters (especially, dielectric permittivity and magnetic loss) has been estimated with the increase of K. Plotting the ${\mu}_{eq}$ and ${\varepsilon}_{eq}$ on the solution map of wave-impedance matching, wide bandwidth microwave absorbance has been predicted in the magnetic composites with an optimum value of K.

• 한국결정성장학회지
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• 제18권4호
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• pp.169-173
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• 2008

본 연구에서는 자외선 영역에서 우수한 발광강도를 가지는 적색 형광체를 얻기 위하여 microwave 급속 열처리법으로 합성하여 $Eu^{3+}$와 $Bi^{3+}$가 도핑된 $YVO_4$의 발광특성을 관찰하였다. Microwave 급속 열처리시 입자의 크기는 매우 미세하며, 응집이 매우 심하였으나 열처리 유지시간이 증가할수록 입자 크기는 증가하고 응집현상은 개선되는 경향을 나타내었다. $YVO_4$: $Eu^{3+}$, $Bi^{3+}$ 적색 형광체의 발광 peak는 $Eu^{3+}$ ion의 영향에 의해 594.9 nm와 602.3 nm에서 $^5D_0{\longrightarrow}^7F_1$ 전자 천이에 의한 약한 발광 peak와 616.7 nm와 620.0 nm에서 $^5D_0{\longrightarrow}^7F_2$ 전자 천이에 의한 강한 발광 peak이 관찰 되었다. Microwave 급속 열처리법을 형광체 합성시 장시간 열처리 시간이 필요하지 않으면서 균일한 activator의 확산으로 인하여 발광특성을 향상시키는 것을 확인 할 수 있었다.

• Carbon letters
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• 제3권4호
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• pp.205-209
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• 2002

In the reaction of gas-solid phases, the microwave energy plays a role as a catalyst, because it causes friction between adjacent molecules and enables an unique characteristics of interior heating of the materials. When the dipole gases are adsorbed inside of the pore of carbon materials, the gases are decomposed by the microwave energy and reacted with the carbon atoms. Using this principle, we could make the activated carbon from coconut shell within 20 minute, and this residence time for activation is about 1/16 of rotary kiln. The BET surface area of activated carbon made by microwave is about $1,100m^2/g$ similar to conventional method of rotary kiln. In this study, the power of microwave generator was 400~1000W, and the gas for activation was steam mainly.

• Current Research on Agriculture and Life Sciences
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• 제32권3호
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• pp.131-134
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• 2014

The thermal death kinetics of the Black timber bark beetle, Xylosandrus germanus, was investigated to develop a heat treatment for control of infested wood packing materials used to export goods. To determine the feasibility of microwave irradiation as an alternative control method, laboratory experiments irradiating wooden blocks of Douglas fir ($200{\times}200{\times}250mm$), which were artificially infested with adults, with 2.45 GHz of microwave energy. All (100%) Ambrosia beetle adults were killed by both hot water treatments and microwave irradiation at $52^{\circ}C$ and $58^{\circ}C$, respectively. Probit analyses estimated the internal wood temperature required to produce Probit (0.99) efficacy to be $64.7^{\circ}C$ (95% CI $62.4-69.9^{\circ}C$) at one minute after microwave treatment.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 추계 학술발표 강연 및 논문 개요집
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• pp.129-130
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• 1994

• 한국재료학회:학술대회논문집
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• 한국재료학회 1993년도 추계 학술발표 강연 및 논문 개요집
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• pp.142-142
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• 1993

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 춘계 학술발표 강연 및 논문 개요집
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• pp.131-131
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• 1994

• 한국세라믹학회지
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• 제49권2호
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• pp.151-154
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• 2012

Flower-like and plate-like CuO nanopowder has been successfully synthesized using a facile microwave-assisted synthetic route. The morphology and size of the final products strongly depended on microwave power. The phase, structures and morphologies of the as-prepared products were investigated in detail by BET surface area analysis, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). In addition, the chemical oxygen demand of polluted lake water was employed for characterization of these new photocatalysts. The results showed correlations between the morphology of CuO micro-crystals and their catalytic properties.