• Composites Research
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• v.30 no.2
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• pp.138-144
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• 2017

Damage sensing of polymer composite films consisting of poly(dicyclopentadiene) p-DCPD and carbon nanotube (CNT) was studied experimentally. Only up to 1st ring-opening polymerization occurred with the addition of CNT, which made the modified film electrically conductive, while interfering with polymerization. The interfacial adhesion of composite films with varying CNT concentration was evaluated by measuring the wettability using the static contact angle method. 0.5 wt% CNT/p-DCPD was determined to be the optimal condition via electrical dispersion method and tensile test. Dynamic fatigue test was conducted to evaluate the durability of the films by measuring the change in electrical resistance. For the initial three cycles, the change in electrical resistance pattern was similar to the tensile stress-strain curve. The CNT/p-DCPD film was attached to an epoxy matrix to demonstrate its utilization as a sensor for fracture behavior. At the onset of epoxy fracture, electrical resistance showed a drastic increase, which indicated adhesive fracture between sensor and matrix. It leads to prediction of crack and fracture of matrix.

• Journal of the Korean Applied Science and Technology
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• v.33 no.2
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• pp.247-254
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• 2016

Since microzirconia has excellent thermal and mechanical properties with high chemical and electrical resistance, it can be used in various fields. When the surface of zirconia becomes hydrophilic, its dispersibility in water will be improved as well as the resistance to most hydrophobic contaminants will be increased. In this study, we investigated the introduction of a hydrophilic groups on the microzircornia surface through hydrolysis and condensation reactions with two different silanes containing hydrophilic functional groups, such as ${\gamma}$-aminopropyltrimethoxysilane (APS) and ${\gamma}$-ureidopropyltrimethoxysilane (UPS) at different pH and concentration conditions. A covalent bond formation between the surface hydroxyl groups of zirconia and that of hydrolyzed silanes was confirmed by ninhydrin test and FT-IR spectroscopy. However, the presence of Si on the surfaces of both silane modified microzirconias was unable to detect by SEM/EDS technique. In addition, particle size analysis results provide that the size of microzirconia was changed to smaller or bigger than that of original zirconia due to crushing and aggregation during the modification process. The water dispersibility was improved for only APS modifed zirconia (AS-2 and AS-3) under neutral pH condition, but the water dispersibility and stability for all cases of 0.5~2% UPS modifed zirconia (US series) were much improved.

• Korean Chemical Engineering Research
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• v.44 no.6
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• pp.602-608
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• 2006

Carbon fiber (CF) reinforced papers using polyacrylonitrile (PAN) based CF and wood pulp were prepared by varying the lengths and the concentrations of CF, and the basis weight of paper to investigate adhesive state between CF and pulp, and physical properties and electrical conductivity of the paper. The reinforcement was caused by physical entanglement and adhesion at the interface of the different fibers rather than by chemical bonds. The tear strength and the thickness of the paper increased as increasing the concentration of CF, while the tensile and the burst strength of the paper decreased. The improved dispersion of CF in the paper was obtained from mixing shorter CF, but the maximum electrical conductivity of the paper was gained from mixing 10 mm chopped CF. The electrical conductivity of the paper increased sharply from 2 wt％ to 8 wt％ of CF showing S-curve, and increased linearly as increasing the basis weight of the paper. Therefore, in order to improve the electrical conductivity and the physical property of the paper, the increase of basis weight of the paper is also important as the increase of CF content in the paper.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.26-36
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• 2018

Conventional nickel-based catalyst processes used for dry reforming reactions have high activation temperatures and problems such as carbon deposition and metal sintering on the active sites of the catalyst surface. In this study, the characteristics of butane dry reforming reaction were investigated by using DBD plasma combined with catalytic process and compared with existing catalyst alone process. The physical and chemical properties of the catalysts were investigated using a surface area & pore size analyzer, XRD, SEM and TEM. Using $10%Ni/{\gamma}-Al_2O_3$ at $580^{\circ}C$, in the case of the catalyst+plasma process, the conversion of carbon dioxide and butane were improved by about 30% than catalyst alone process. When the catalyst+plasma process, the conversion of carbon dioxide and butane and the hydrogen production concentration are enhanced by the influence of various active species generated by the plasma. In addition, it was found that the particle size of the catalyst is decreased by the plasma in the reaction process, and the degree of dispersion of the catalyst is increased to improve the efficiency.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.1-8
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• 2017

Cu/Mn/Ce catalysts for water gas shift (WGS) reaction were synthesized by urea-nitrate combustion method with the fixed molar ratio of Cu/Mn as 1:4 and 1:1 with the doping concentration of Ce from 0.3 to 0.8 mol%. The prepared catalysts were characterized with SEM, BET, XRD, XPS, $H_2$-TPR, $CO_2$ TPD, $N_2O$ chemisorption analysis. The catalytic activity tests were carried out at a GHSV of $28,000h^{-1}$ and a temperature range of 200 to $400^{\circ}C$. The Cu/Mn(CM) catalysts formed Cu-Mn mixed oxide of spinel structure ($Cu_{1.5}Mn_{1.5}O_4$) and manganese oxides ($MnO_x$). However, when a small amount of Ce was doped, the growth of $Cu_{1.5}Mn_{1.5}O_4$ was inhibited and the degree of Cu dispersion were increased. Also, the doping of Ce on the CM catalyst reduced the reduction temperature and the base site to induce the active site of the catalyst to be exposed on the catalyst surface. From the XPS analysis, it was confirmed that maintaining the oxidation state of Cu appropriately was a main factor in the WGS reaction. Consequently, Ce as support and dopant in the water gas shift reaction catalysts exhibited the enhanced catalytic activities on CM catalysts. We found that proper amount of Ce by preparing catalysts with different Cu/Mn ratios.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.610-616
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• 2011

A series of polyurethane acrylate/ZnO (PUA/ZnO) nanocomposite films with different ZnO contents were successfully prepared via a UV-curing system. The synthesis and physical properties including morphological structure, thermal properties, barrier properties and optical properties, and antimicrobial properties were investigated as a function of ZnO concentration. FTIR and SEM results showed that these PUA/ZnO nanocomposite films did not have a strong interaction between PUA and ZnO, which may lead to no increase in thermal stability. By incorporating ZnO nanoparticles, the UV blocking and antibacterial properties increased as the content of ZnO increased. Specially, the oxygen permeability in composite films changed from $2005cc/m^2/day$ to $150cc/m^2/day$ by adding the ZnO nanoparticle, which indicates that the PUA/ZnO nanocomposite films can be applied as good barrier packaging materials. Physical properties of the UV-cured PUA/ZnO nanocomposite film are strongly dependent upon the dispersion state of ZnO nanoparticles and their morphology in the films.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.173-173
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• 2010

$Bi_4Ti_3O_{12}$ ($B_4T_3$) is a unique ferroelectric material that has a relatively high dielectric constant, high Curie temperature, high breakdown strength, and large spontaneous polarization. As a result this material has been widely studied for many applications, including nonvolatile ferroelectric random memories, microelectronic mechanical systems, and nonlinear-optical devices. Several reports have appeared on the use of Mn dopants to improve the electrical properties of $B_4T_3$ thin films. Mn ions have frequently been used for this purpose in thin films and multilayer capacitors in situations where intrinsic oxygen vacancies are the major defects. However, no systematic study of the optical properties of $B_4T_3$ films has appeared to date. Here, we report optical data for these films, determined by spectroscopic ellipsometry (SE). We also report the effects of thermal annealing and Mn doping on the optical properties. The SE data were analyzed using a multilayer model that is consistent with the original sample structure, specifically surface roughness/$B_4T_3$ film/Pt/Ti/$SiO_2$/c-Si). The data are well described by the Tauc-Lorentz dispersion function, which can therefore be used to model the optical properties of these materials. Parameters for reconstructing the dielectric functions of these films are also reported. The SE data show that thermal annealing crystallizes $B_4T_3$ films, as confirmed by the appearance of $B_4T_3$ peaks in X-ray diffraction patterns. The bandgap of $B_4T_3$ red-shifts with increasing Mn concentration. We interpret this as evidence of the existence deep levels generated by the Mn transition-metal d states. These results will be useful in a number of contexts, including more detailed studies of the optical properties of these materials for engineering high-speed devices.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.4
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• pp.127-132
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• 2019

In this study, barium strontium titanate (BSTO) with high dielectric perovskite structure was synthesized by liquid-solid solution synthesis and the surface was modified using trimethylsilyl chloride (TMCS) as a silylation agent. Silylation surface modification is a method of reacting -OH ligand on the surface of BSTO nanoparticles with Cl in TMCS to generate HCl and replacing the ligand on the surface of nanoparticles with -Si, -CH₃. Silylation was optimized by varying the concentration of TMCS, and the structure of the silicon network was confirmed by Fourier-transform infrared spectroscopy. In addition, the crystallinity of BSTO nanoparticles was confirmed by X-ray diffractometer and the size of the nanoparticles was calculated using Scherrer equation. The field emission scanning electron microscopic image observed the change of the surface-modified BSTO particle size, and the contact angle measurement confirmed the hydrophobic property of the contact angle of 120.9° in the optimized nanoparticles. Finally, the surface-modified BSTO dispersion experiment in de-ionized water confirmed the hydrophobic degree of the nanoparticles.

• Journal of Adhesion and Interface
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• v.13 no.2
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• pp.58-63
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• 2012

CFRP chip is the byproduct from carbon fiber reinforced plastic (CFRP) processing. CFRP chip is not simply a waste mainly composed of fine carbon fiber and epoxy resin. CFRP chip keeps matrix to maximize their reinforcing effect. To obtain a uniform length of carbon fiber in CFRP chip, chip was chopped ina mortar. CFRP chip should be purified to get better interface adhesion. Epoxy resin on the carbon fiber was removed by $H_2O_2$ surface etching treatment. Optimal dispersion and fabrication conditions of CFRP chip embedded in phenolic resin were determined by thermal stability for fire retardant applications. CFRP chip-phenolic composite exhibits better mechanical and thermal properties than neat phenolic resin. Surface condition of CFRP chip-phenolic composite was evaluated by static contact angle measurement. Contact angle of CFRP chip-phenolic composite was greater than neat phenolic due to heterogeneous condition of fine carbon fibers. From the evaluation for fire retardant (ASTM D635-06) test, thermal stability of CFRP chip-phenolic composite was found to be improved with higher concentration of CFRP chip.

• Journal of Korea Water Resources Association
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• v.54 no.5
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• pp.335-345
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• 2021

The one-dimensional solute transport models have been developed for recent decades to predict behavior and fate of solutes in rivers. Transient storage model (TSM) is the most popular model because of its simple conceptualization to consider the complexity of natural rivers. However, the TSM is highly dependent on its parameters which cannot be directly measured. In addition, the TSM interprets the late-time behavior of concentration curves in the shape of an exponential function, which has been evaluated as not suitable for actual solute behavior in natural rivers. In this study, we suggested a stochastic approach to the solute transport analysis. We delineated the model development and model application to a natural river, and compared the results of the proposed model to those of the TSM. To validate the proposed model, a tracer test was carried out in the 4.85 km reach of Gam Creek, one of the first-order tributaries of Nakdong River, South Korea. As a result of comparing the power-law slope of the tail of breakthrough curves, the simulation results from the stochastic storage model yielded the average error rate of 0.24, which is more accurate than the 14.03 and 1.87 from advection-dispersion model and TSM, respectively. This study demonstrated the appropriateness of the power-law residence time distribution to the hyporheic zone of the Gam Creek.