• 한국재료학회지
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• 제17권2호
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• pp.81-85
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• 2007

Embedded capacitor technology can improve electrical perfomance and reduce assembly cost compared with traditional discrete capacitor technology. To improve the capacitance density of the $Al_2O_3$ based embedded capacitor on Cu cladded fiber reinforced plastics (FR-4), the specific surface area of the $Al_2O_3$ thin films was enlarged and their surface morphologies were controlled by anodization process parameters. From I-V characteristics, it was found that breakdown voltage and leakage current were 23 V and $1{\times}10^{-6}A/cm^2$ at 3.3 V, respectively. We have also measured C-V characteristics of $Pt/Al_2O_3/Al/Ti$ structure on CU/FR4. The capacitance density was $300nF/cm^2$ and the dielectric loss was 0.04. This nano-porous $Al_2O_3$ is a good material candidate for the embedded capacitor application for electronic products.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제32회 KOSCO SYMPOSIUM 논문집
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• pp.49-54
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• 2006

The present study conducted a numerical modeling on the diesel SCR (selective catalytic reduction) system using ammonia as a reductant over vanadium-based catalysts $(V_2O_5-WO_3/TiO_2)$. Transient modeling for ammonia adsorption/desorption on the catalyst surface was firstly carried out, and then the SCR reaction was modeled considering for it. In the current catalytic reaction model, we extended the pure chemical kinetic model based on laboratory-scale powdered-phase catalyst experiments to the chemico-physical one applicable to realistic commercial SCR reactors. To simulate multi-dimensional heat and mass transfer phenomena, the SCR reactor was modeled in two dimensional, axisymmetric domain using porous medium approach. Also, since diesel engines operate in transient mode, the present study employed an unsteady model. In addition, throughout simulations using the developed code, effects of space velocity on the DeNOx performance were investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1472-1474
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• 1994

In this paper, $TiO_2-V_2O_5$ thin films are fabricated by Sol-Gel method and their humidity-sensing characteristics have been investigated. The microstructure of specimen is porous. The humidity-sensing characteristics of thin films are good according to increasing heat treatment temperature and decreasing measurement frequency.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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• pp.687-693
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• 2004

Composite membranes with a titania layer were prepared by soaking-rolling method with the titania sol of nanoparticles formed in the sol-gel process and investigated regarding the vapor permeation of various organic mixtures. The support modification was conducted by pressing $SiO_2$ xerogel of 500 nm in particle size under 10 MPa on the surface of a porous stainless steel (SUS) substrate and designed the multi-layered structure by coating the intermediate layer of ${\gamma}-Al_2O_3$. Microstructure of titania membrane was affected by heat-treatment and synthesis conditions of precursor sol, and titania formed at calcination temperature of 300$^{\circ}C$ with sol of [$H^+$]/[TIP]=0.3 possessed surface area of 210 $m^2$/g, average pore size of 1.25 nm. The titania composite membrane showed high $H_2/N_2$ selectivity and water/ethanol selectivity as 25-30 and 50-100, respectively. As a result of vapor permeation for water-alcohol and alcohol-alcohol mixture, titania composite membrane showed water-permselective and molecular-sieve permeation behavior. However, water/methanol selectivity of the membrane was very low because of chemical affinity of permeants for the membrane by similar physicochemical properties of water and methanol.

• 한국포장학회지
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• 제27권2호
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• pp.55-62
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• 2021

This study aims to reduce the rancid odor generated during the fermentation process of kimchi by inserting zinc oxide (ZnO) into an inorganic porous material with a high surface area to decompose or adsorb the fermentation odor. ZnO activated by the presence of moisture exhibits decomposition of rancid odors. Mixed with Titanium dioxide (TiO₂), a photocatalyst. To manufacture the packaging liner used in this study, NaOH, ZnCl₂, and TiO₂ powder were placed in a tank with diatomite and water. The sludge obtained via a hydrothermal ultrasonication synthesis was sintered in an oven. After being pin-milled and melt-blended, the powders were mixed with linear low-density polyethylene (L-LDPE) to make a masterbatch (M/B), which was further used to manufacture liners. A gas detector (GasTiger 2000) was used to investigate the total amount of sulfur compounds during fermentation and determine the reduction rate of the odor-causing compounds. The packaging liner cross-section and surface were investigated using a scanning electron microscope-energy dispersive X-ray spectrometer (SEM-EDS) to observe the adsorption of sulfur compounds. A variety of sulfur compounds associated with the perceived unpleasant odor of kimchi were analyzed using gas chromatography-mass spectrometry (GC-MS). For the analyses, kimchi was homogenized at room temperature and divided into several sample dishes. The performance of the liner was evaluated by comparing the total area of the GC-MS signals of major off-flavor sulfur compounds during the five days of fermentation at 20℃. As a result, Nano-grade inorganic compound liners reduced the sulfur content by 67 % on average, compared to ordinary polyethylene (PE) foam liners. Afterwards SEM-EDS was used to analyze the sulfur content adsorbed by the liners. The findings of this study strongly suggest that decomposition and adsorption of the odor-generating compounds occur more effectively in the newly-developed inorganic nanocomposite liners.

• Membrane and Water Treatment
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• 제6권3호
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• pp.251-262
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• 2015

In this work the preparation and characterization of a membrane containing a uniform mesoporous Titanium oxide top layer on a porous stainless steel substrate has been studied. The 316 L stainless steel substrate was prepared by powder metallurgy technique and modified by soaking-rolling and fast drying method. The mesoporous titania membrane was fabricated via the sol-gel method. Morphological studies were performed on both supported and unsupported membranes using scanning electron microscope (SEM) and field emission scanning microscope (FESEM). The membranes were also characterized using X-ray diffraction (XRD) and $N_2$-adsorption / desorption measurement (BET analyses). It was revealed that a defect-free anatase membrane with a thickness of $1.6{\mu}m$ and 4.3 nm average pore size can be produced. In order to evaluate the performance of the supported membrane, single-gas permeation experiments were carried out at room temperature with nitrogen gas. The permeability coefficient of the fabricated membrane was $4{\times}10^{-8}\;lit\;s^{-1}\;Pa^{-1}\;cm^{-1}$.

• 한국응용과학기술학회지
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• 제36권2호
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• pp.498-506
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• 2019

이 연구는 경상북도 봉화지역에서 매장된 천연 광물을 이용하여 화장료용의 분체로써 활용가치를 부여한 코팅 방법에 관한 것이다. 이 광물의 이름은 부석이라고 칭하며, 미립자 파우더를 개발하여 이 파우더의 성능을 평가하고 화장품의 효능적 가치가 있는 가에 대하여 연구한 결과를 보고한다. 이 파우더의 표면에 오일을 코팅하기 위하여 미립자 표면에 알루미늄하이드록사이드를 1차 코팅한 후에 여기에 알킬실란으로 코팅하였다. 또한, 식물성 오일로 코팅하여 파우더의 응집을 막고, 오일상에서의 분산성을 높일 수 있도록 하였다. 첫째; 부석파우더의 입자는 $10{\sim}50{\mu}m$의 입자를 가지고 있었으며, 입자의 표면에 다공성의 구멍이 있었다. 둘째; 이 파우더의 구성성분은 $SiO_2$, $Al_2O_3$, $Fe_2O_3$, MgO, CaO, $K_2O_2$, $Na_2O$, $TiO_2$, $TiO_2$, MnO, $Cr_2O_3$, $V_2O_5$ 등을 함유하였다. 셋째: 이 파우더의 입자는 판상형 구조를 가지며, 다공성으로 적갈색을 가지고 있음을 SEM과 TEM 분석을 통하여 알 수 있었다. 넷째; 이부석 파우더의 원적외선 방사율은 $0.924{\mu}m$이었으며, 방사에너지는 $3.72{\times}10^W/m^2{\cdot}{\mu}m$ 이었다. 또한 음이온 방출량은 128 ION/cc를 방출하는 것으로써, 코팅을 하더라도 변하지 않고 그대로 그 성능이 유지되는 것을 알 수 있었다. 이러한 결과를 바탕으로 화장품의 응용분야로써 비비크림, 쿠션파운데이션, 파우더펙트 등의 색조화장품, 선블록크림, 워시오프 마사지팩 등의 기초 화장료에 폭넓게 응용이 가능할 것으로 기대한다.

• 한국세라믹학회지
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• 제50권6호
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• pp.353-358
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• 2013

The hot corrosion behavior of plasma sprayed 4 mol% $Y_2O_3-ZrO_2$ (YSZ) thermal barrier coatings (TBCs) with volcanic ash is investigated. Volcanic ash that deposited on the TBCs in gas-turbine engines can attack the surface of TBCs itself as a form of corrosive melt. YSZ coating specimens with a thickness of 430-440 ${\mu}m$ are prepared using a plasma spray method. These specimens are subjected to hot corrosion environment at $1200^{\circ}C$ with five different duration time, from 10 mins to 100 h in the presence of corrosive melt from volcanic ash. The microstructure, composition, and phase analysis are performed using Field emission scanning electron microscopy, including Energy dispersive spectroscopy and X-ray diffraction. After the heat treatment, hematite ($Fe_2O_3-TiO_2$) and monoclinic YSZ phases are found in TBCs. Furthermore the interface area between the molten volcanic ash layers and YSZ coatings becomes porous with increases in the heat treatment time as the YSZ coatings dissolved into molten volcanic ash. The maximum thickness of this a porous reaction zone is 25 ${\mu}m$ after 100 h of heat treatment.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3470-3477
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• 2022

Soils are porous materials with high shielding capability to attenuate gamma and X-rays. The disposal of radionuclides throughout the soil profile can expose the living organisms to ionizing radiation. Thus, studies aiming to analyze the shielding properties of the soils are of particular interest for radiation shielding. Investigations on evaluating the shielding capabilities of highly weathered soils are still scarce, meaning that additional research is necessary to check their efficiency to attenuate radiation. In this study, the radiation shielding properties of contrasting soils were evaluated. The radiation interaction parameters assessed were attenuation coefficients, mean free path, and half- and tenth-value layers. At low photon energies, the photoelectric absorption contribution to the attenuation coefficient predominated, while at intermediate and high photon energies, the incoherent scattering and pair production were the dominant effects. Soils with the highest densities presented the best shielding properties, regardless of their chemical compositions. Increases in the attenuation coefficient and decreases in shielding parameters of the soils were associated with increases in clay, Fe₂O₃, Al₂O₃, and TiO₂ amounts. In addition, this paper provides a comprehensive description of the shielding properties of weathered soils showing the importance of their granulometric fractions and oxides to the attenuation of the radiation.

• 한국재료학회지
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• 제26권8호
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• pp.449-453
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• 2016

$HA(hydroxyapatite)/{\beta}-TCP$ (tricalcium phosphate) biomaterial (BCP; biphasic calcium phosphate) is widely used as bone cement or scaffolds material due to its superior biocompatibility. Furthermore, $NH_4HCO_3$ as a space holder (SH) has been used to evaluate feasibility assessment of porous structured BCP as bone scaffolds. In this study, using a spark plasma sintering (SPS) process at 393K and 1373K under 20MPa load, porous $HA/{\beta}-TCP$ biomaterials were successfully fabricated using $HA/{\beta}-TCP$ powders with 10~30 wt% SH, TiH2 as a foaming agent, and MgO powder as a binder. The effect of SH content on the pore size and distribution of the BCP biomaterial was observed by scanning electron microscopy (SEM) and a microfocus X-ray computer tomography system (SMX-225CT). The microstructure observations revealed that the volume fraction of the pores increased with increasing SH content and that rough pores were successfully fabricated by adding SH. Accordingly, the cell viabilities of BCP biomaterials were improved with increasing SH content. And, good biological properties were shown after assessment using Hanks balanced salt solution (HBSS).