• Elastomers and Composites
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• v.43 no.2
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• pp.82-87
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• 2008

In this study, nine kinds of polyimides were synthesized from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA), m-pheny lenediamine (m-PDA) and 4,4'-oxydianiline (ODA) by controlling molar ratio of monomers. Synthesized polyimides were used as insulator films for 2-layer Flexible Copper Clad Laminate(FCCL) which were manufactured by the casting method. Glass transition temperature and thermal degradation temperature for 5% weight loss of the polyimide film were improved by increasing contents of m-PDA and PMDA, respectively. Water absorption of polyimide film was reduced by increasing contents of ODA and BPADA which have relatively long structure, respectively. Peel strength of 2-layer FCCL was improved by increasing contents of ODA and BPADA.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.157-166
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• 2017

In general, carbonation and chlorine ions are the most harmful causes of deterioration of concrete structures. Recently, a method has been developed to control the corrosion of rebar in concrete containing chloride by impregnating a Surface coating material with a inhibitor. In this study, accelerated carbonation and differential thermogravimetric analysis (TG-DTA) and CASS tests were carried out to evaluate the characteristics of Surface coatings containing Organic Corrosion inhibitors which are excellent in corrosion inhibition and fix degradation causes $CO_2$ and $Cl^-$. As a result of the experiment, TG-DTA analysis and accelerated carbonation showed that $CO_2$ was directly reacted with amine derivative in concrete by the incorporation of Organic Corrosion inhibitor. In other words, $CO_2$ was immobilized and carbonation inhibition effect was confirmed. In addition, in the CASS test, the specimen coated with the Surface coating material containing the Organic Corrosion inhibitor with $Cl^-$ fixing property showed no corrosion until the 28th day and had excellent performance in preventing corrosion of a rebar by the chloride ion.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.165-172
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• 2013

Power generating unit structures are designed and built to meet standard to secure its safety for expected life time. As the structures have been exposed to combined environment, degradation of structure material is accelerated and it can cause unexpected damage; evaluating precise mechanical properties of weak site like welded area is an essential research area as it is directly connected to safety issues. Existing measuring technique like tensile test requires specific size in testing specimen yet it is destructive method which is hard to apply on running structures. To overcome above mentioned limitation, IIT is getting limelight as it is non-destructive and simple method. In this study, latest technique is introduced to evaluate tensile property and residual stress by analyzing stress field occurs under the indenter while IIT is performed. Test on welded area, the weak site of nuclear structures have been practiced and confirmed that IIT can be usefully applied to evaluate integrity in industry.

• Journal of Conservation Science
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• v.29 no.2
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• pp.127-138
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• 2013

Plastic, widely used as a material for contemporary art, get damaged as directly exposed to temperature, humidity, ultra violet, etc. And it is very quickly damaged in early time, once damaged, it can't recover into original state. But like this characteristics, there is a few advanced research in Korea. So this study deal with a rising value of plastic artifacts in other country, United Kingdom and France, current conservation state, identification and cleaning method. Also 5 types of cleaners(distilled water, ethanol, acetone, eraser) and adhesives(cyanoacrylate, epoxy, acrylic, chloroprene rubber) were evaluated by produced plastics(PVC, PE, PP, PS, PU). As a result of experiment, ethanol and acetone that were previous evaluated in other research performed in other country are the best cleaner. Result of degradation after adhesive, cyanoacrylate and epoxy resin showed better performance and stability. As a basic research, this study is expected that can be used in future researches.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.288-289
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• 2011

Indium Tin Oxide (ITO) is a typical highly Transparent Conductive Oxide (TCO) currently used as a transparent electrode material. Most widely used deposition method is the sputtering process for ITO film deposition because it has a high deposition rate, allows accurate control of the film thickness and easy deposition process and high electrical/optical properties. However, to apply high quality ITO thin film in a flexible microelectronic device using a plastic substrate, conventional DC magnetron sputtering (DMS) processed ITO thin film is not suitable because it needs a high temperature thermal annealing process to obtain high optical transmittance and low resistivity, while the generally plastic substrates has low glass transition temperatures. In the room temperature sputtering process, the electrical property degradation of ITO thin film is caused by negative oxygen ions effect. This high energy negative oxygen ions(about over 100eV) can be critical physical bombardment damages against the formation of the ITO thin film, and this damage does not recover in the room temperature process that does not offer thermal annealing. Hence new ITO deposition process that can provide the high electrical/optical properties of the ITO film at room temperature is needed. To solve these limitations we develop the Magnetic Field Shielded Sputtering (MFSS) system. The MFSS is based on DMS and it has the plasma limiter, which compose the permanent magnet array (Fig.1). During the ITO thin film deposition in the MFSS process, the electrons in the plasma are trapped by the magnetic field at the plasma limiters. The plasma limiter, which has a negative potential in the MFSS process, prevents to the damage by negative oxygen ions bombardment, and increases the heat(-) up effect by the Ar ions in the bulk plasma. Fig. 2. shows the electrical properties of the MFSS ITO thin film and DMS ITO thin film at room temperature. With the increase of the sputtering pressure, the resistivity of DMS ITO increases. On the other hand, the resistivity of the MFSS ITO slightly increases and becomes lower than that of the DMS ITO at all sputtering pressures. The lowest resistivity of the DMS ITO is $1.0{\times}10-3{\Omega}{\cdot}cm$ and that of the MFSS ITO is $4.5{\times}10-4{\Omega}{\cdot}cm$. This resistivity difference is caused by the carrier mobility. The carrier mobility of the MFSS ITO is 40 $cm^2/V{\cdot}s$, which is significantly higher than that of the DMS ITO (10 $cm^2/V{\cdot}s$). The low resistivity and high carrier mobility of the MFSS ITO are due to the magnetic field shielded effect. In addition, although not shown in this paper, the roughness of the MFSS ITO thin film is lower than that of the DMS ITO thin film, and TEM, XRD and XPS analysis of the MFSS ITO show the nano-crystalline structure. As a result, the MFSS process can effectively prevent to the high energy negative oxygen ions bombardment and supply activation energies by accelerating Ar ions in the plasma; therefore, high quality ITO can be deposited at room temperature.