• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.55.2-55.2
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• 2009

A polymer electrolyte membrane (PEM) fuel cell has been getting large interest as a typical issue in useful applications. The PEMFC is composed of a membrane, catalyst and the bipolar plate. SnOx:F films on SUS316 stainless steel were prepared as a function of substrate with using electron cyclotron resonance-metal organic chemical vapor deposition (ECR-MOCVD) in order to achieve the corrosion-resistant and low contact resistance bipolar plates for PEM fuel cells. The SnOx:F films coated on SUS316 substrate at surface plasma treatment for excellent stability, before/after heat treatment for good crystalline structure and microwave power for were characterized by X-ray diffraction (XRD), auger electron microscopy (AES) and field emission-scanning electron microscopy (FE-SEM). The SnOx:F film coated on SUS316 substrate with various process parameters were able to observe optimum interfacial contact resistance (ICR) and corrosion resistance. It can be concluded that fluorine-doping content plays an important function in electrical property and characteristic of corrosion-protective film.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.252-259
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• 2016

In order to form an aluminum-doped zinc oxide (AZO) transparent electrode film on a polyethylene terephthalate (PET) substrate used for a flexible display substrate, the AZO transparent electrode was produced at low temperature without substrate heating. Even though the produced electrode showed characteristic optical transmittance of 90 % (at 550 nm) and sheet resistance within $100{\Omega}/sq$, cracks occurred 10 minutes after loading applied 2 mm radius of curvature, and the sheet resistance increased linearly. An insertion layer of ZrCu was formed between the AZO film and the PET substrate to suppress the generation of cracks on the AZO film. It was verified that the crack was not generated 30 minutes after the loading of 2 mm radius of curvature, and no increase in sheet resistance was recorded. There was also not cracks in the dynamic bending test of 4 mm radius, but surface resistance was slightly increased. As a result, the ZrCu insertion film improved the interfacial adhesion between the substrate and AZO film layer without increasing sheet resistance and decreasing transmittance.

• 연구논문집
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• s.24
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• pp.63-79
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• 1994

This article reports a experimental study of the method to achieve a bond joint at lower temperature in a short time. DC magnetron sputtering of Sn, Sn/Pb, Sn/In and Sn/Cu on copper substrate was provided as an interlayer for Cu to Cu bonding under the air environment. Various examination was conducted and investigated on the effect of experimental parameters such as coating materials, coating time(or coating thickness), bonding temperature and bonding time etc. Bonding was performed at the temperature of $210^\circC-320^\circC$ for 0sec and interfacial reaction between the coated layer and copper substrate was examined using optical, scanning electron microscope and x-ray diffractometer. From the obtained results, it was found that intermetallic compounds layer consisted of $\eta-phase(Cu_6Sn_5)$ and $\beta-phase(Cu_3Sn)$ was formed at the joint interface for almost all coating materials. But the dominant phase formed in the preetched Cu substrate coated with Sn was $\beta-phase$. A characteristic morphology looks like a reaction ring, which was believed as the strong interconnecting regions between two substrates, was found to be formed on the reaction surface of copper substrates. The morphologies and compositions of the intermetallics, which depends on the regions of the reaction surface, was appeared as greatly different. Based on above results, the new bonding process to make the joint at lower temperature for short time can be admitted as a feasible process.

• Polymer(Korea)
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• v.35 no.6
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• pp.580-585
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• 2011

This article aims to enhance the biodegradability and environment-friendliness of petroleum based biodegradable poly(butylene adipate-co-succinate-co-terephthalate)(PBAST) by blending chemically modified thermoplastic starch(CMPS). CMPS is a kind of bio-based biodegradable resin which is manufactured by reacting starch with maleic anhydride(MA) in the presence of a plasticizer and a free radical initiator. The characteristic properties of PBAST/CMPS blends were investigated by observing their morphology, thermal, mechanical properties, and biodegradability. The good interfacial adhesion between the phases examined by SEM revealed that PBAST/CMPS blends were compatible blends. The tensile strength and elongation decreased with increasing CMPS content, while modulus increased. The biodegradability of the blends was much higher than that of pristine PBAST and increased with increasing CMPS contents.

• Steel and Composite Structures
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• v.38 no.3
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• pp.241-255
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• 2021

In order to study the interfacial bond-slip behavior of steel reinforced recycled concrete (SRRC) under cyclic loading, thirteen specimens were designed and tested under cyclic loading and one under monotonic loading. The test results indicated that the average bond strength of SRRC decreased with the increasing replacement ratio of recycled concrete, whereas the bond strength increased with an increase in the concrete cover thickness, the volumetric stirrup ratio, and the strength of recycled concrete. The ultimate bond strength of the cyclically-loaded specimen was significantly (41%) lower than that of the companion monotonically-loaded specimen. The cyclic phenomena also showed that SRRC specimens went through the nonslip phase, initial slip phase, failure phase, bond strength degradation phase and residual phase, with all specimens exhibiting basically the same shape of the bond-slip curve. Additionally, the paper presents the equations that were developed to calculate the characteristic bond strength of SRRC, which were verified based on experimental results.

• Composites Research
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• v.22 no.5
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• pp.30-36
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• 2009

The failure strengths and modes in carbon fiber reinforced polymeric composites, with two serial bolt-fastened composite joints, were investigated to evaluate the typical joint configurations of composite components. The parametric studies were performed experimentally at room temperature dry and elevated temperature wet, $82.2^{\circ}C$ on several different laminate configurations. Based on the experimental data presented, two basic load-displacements curves are observed. Each failure mode has the characteristic curve. It is showed that the bearing failure mode occurs in elevated temperature wet condition. It is analysed that the strength of bearing failure mode is not highly depending on the effective modulus of specimen. The failure strength at elevated temperature wet is decreased by the cause of interfacial deterioration between fiber and matrix with moisture absorption.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.259-264
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• 2015

For the enhanced oil recovery, one of the most important factors is to determine the surfactant formulation in chemical flood. The objective of this study is to analyze the microemulsion formed between the alkali-surfactant (AS) solution and A crude oil for screening surfactants. The alkali-surfactant solution was manufactured by using the surfactant purchased from AK ChemTech. $C_{16}-PO_7-SO_4$ and sodium carbonate solution were used as surfactant and alkaline, respectively. Both TEGBE and IBA were used as a co-solvent. The AS solution and A crude oil can form a Type III middle phase microemulsion at the salinity from 0.0 wt%~3.6 wt%. Increasing the salinity causes the phase transition of microemulsion from the lower (Type I) to middle (Type III) to upper (Type II) phase. Interfacial tension (IFT) values calculated by Huh's equation were in good agreement with ultralow IFT. According to this characteristic, the surfactant purchased from a domestic company can be applied to the enhanced oil recovery.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.361-368
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• 2012

Required performance for repair materials are strength, ductility, durability and bonding with the substrate concrete. Various kinds of fiber-reinforced cement composites (FRCCs) have been developed and used as repair materials. Strain-hardening cement based composites (SHCC) is one of the effective repair materials that can be used to improve crack-damage tolerance of reinforced concrete (RC) structures. SHCC is a superior FRCC that has multiple cracking characteristic and pseudo strain-hardening behavior. The expansive admixture, which can be used to reduce shrinkage in SHCC materials with less workability by controlling interfacial bonding performance between SHCC and substrate concrete. For the application of SHCC as a repair material to RC structures, this study investigates the flexural performance of expansive SHCC-layered concrete beam. Test variables include the replacement levels of expansive admixture (0 and 10%), repair thickness (30 and 40 mm), and compressive strength of SHCC (30, 70 and 100 MPa). Four point bending tests on concrete beams strengthened with SHCCs were carried out to evaluate the contribution of SHCC on the flexural capacity. The result suggested that expansive SHCC materials can be used for repairing and strengthening of concrete infrastructures.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.406-412
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• 2015

Unidirectional carbon/carbon (C/C) composites were manufactured using phenolic resins as a precursor of the carbonized matrix throughout a one-step manufacturing process. Also, molybdenum oxide ($MoO_3$) and binder pitches were impregnated with phenolic resins to improve the bulk density and mechanical property of the C/C composites. In this study, the influence of $MoO_3$ and binder pitches on mechanical properties of the C/C composites were investigated by measuring flexural strength (${\sigma}_f$) and interlaminar shear strength (ILSS). The results show that the enhancement of interfacial adhesions between the fibers and matrix resins of the C/C composites with $MoO_3$ and binder pitches which led to the improvement of mechanical properties of the C/C composites. This indicates that the presence of $MoO_3$ and binder pitches in C/C composites can develop the graphite structure and increase the bulk density.

• Journal of the Korean Ceramic Society
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• v.55 no.3
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• pp.244-260
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• 2018

Issues in the electrical characterization of semiconducting photoanodes in a photoelectrochemical (PEC) cell, such as the cell geometry dependence, scan rate dependence in DC measurements, and the frequency dependence in AC measurements, are addressed, using the example of a $TiO_2$ photoanode. Contrary to conventional constant phase element (CPE) modeling, the capacitive behavior associated with Mott-Schottky (MS) response was successfully modeled by a Havriliak-Negami (HN) capacitance function-which allowed the determination of frequency-independent Schottky capacitance parameters to be explained by a trapping mechanism. Additional polarization can be successfully described by the parallel connection of a Bisquert transmission line (TL) model for the diffusion-recombination process in the nanostructured $TiO_2$ electrode. Instead of shunt CPEs generally employed for the non-ideal TL feature, TL models with ideal shunt capacitors can describe the experimental data in the presence of an infinite-length Warburg element as internal interfacial impedance - a characteristic suggested to be a generic feature of many electrochemical cells. Fully parametrized impedance spectra finally allow in-depth physicochemical interpretations.