• Bulletin of the Korean Chemical Society
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• 제35권2호
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• pp.466-470
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• 2014

In this paper, organic solvent electrolytes were prepared by a mixture of propylene carbonate (PC), dimethyl carbonate (DMC), tetraethylammonium tetrafluoroborate ($TEABF_4$)s to evaluate the ionic properties of propylene carbonate (PC)/dimethyl carbonate (DMC) mixtures as solvents for a capacitor application, in view of improving the electrochemical performances. The bulk resistance and interfacial resistance of the mixture electrolytes were investigated using an AC impedance method. The morphology of carbon-based electrodes which were contained in different electrolytes was analyzed by scanning electron microscopy (SEM) method. From the experimental results, by increasing the FEC content, capacitance of electrodes was increased, and the interfacial resistance was decreased. In particular, by a content of 2 vol % FEC in 0.2 M $TEABF_4$ PC/DMC solvent, the electrolyte showed the superior capacitance. However, when FEC content exceeds 2 vol %, the capacitance was decreased and the interfacial resistance was increased.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.1031-1036
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• 2000

In this study, a numerical simulation that can effectively predict the strengthening effect of repaired aged RC structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are modeled as quasi-brittle materials. An elastic-perfectly plastic constitutive relationship is introduced for reinforcing bars. Also, a linear-elastic relationship for repair materials such as FRP or CFS. Structural deterioration in terms of corrosion of steel rebar is considered. The interfacial property between steel and concrete which is reduced by corrosion of steel rebar is obtained by comparing numerical results with experimental results of pull out tests. Obtained values are used in repaired reinforced concrete structures under flexural loading conditions. To investigate strengthening effect of the structures repaired with carbon fiber sheet(CFS), repaired and unrepaired RC structures are analyzed numerically. From analysis, rip-off, debonding and rupture failure mechanisms of interface between substrate and CFS can be determined. Finally, strengthening effect according to the variation of interfacial material properties is investigated, and it is shown that interfacial material properties have influence on the mechanical behavior of repaired structure systems Therefore, the developed numerical method using axial deformation link elements can use for determining the strengthening effects and failure mechanism of repaired aged RC structure.

• Composites Research
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• 제32권2호
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• pp.96-101
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• 2019

섬유와 수지 간 계면접착력은 복합재료 성능과 관련되므로 이를 정확하게 평가하는 것은 매우 중요하다. 본 연구에서는, 피로 하중 조건에서의 마이크로드롭렛 실험에 의한 계면접착력 평가를 실시하였다. 도파민이 적용된 에폭시 수지에 대하여 기계적 물성 및 계면접착력을 측정하였다. 기계적 물성을 평가하기 위해 인장 시편을 제작하였고, 계면 접착력 평가를 위하여 유리섬유에 에폭시 마이크로드롭렛을 만든 시편을 사용하였다. 특히 마이크로드롭렛 피로 실험 시 동일한 직경의 마이크로드롭렛을 사용하여 동일한 조건에서 실험하였다. 그 결과 인장 및 마이크로드롭렛 실험을 통해 에폭시 수지에 도파민이 적용될 때 기계 및 계면접착력이 향상됨을 확인하였다. 도파민이 에폭시 수지의 경화정도를 향상시키고 에폭시 수지에 하이드록실 그룹을 부여하여 기계적 물성 및 유리섬유 간 계면 접착력을 증가시켰을 것으로 사려된다.

• 접착 및 계면
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• 제12권1호
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• pp.26-33
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• 2011

폴리케톤 필름의 산처리 조건에 따른 필름 표면의 화학적인 변화를 접촉각과 XPS를 이용하여 분석하고, 모폴로지의 변화를 SEM과 AFM을 통하여 살펴보고, 최종적으로 이러한 변화가 폴리케톤 필름과 고무와의 계면접착력에 어떠한 영향을 미치는지를 살펴보았다. 인산처리에 의하여 폴리케톤 필름의 표면에 젖음성이 증가하여 인산의 농도 및 처리시간에 따라서 접촉각이 감소하였으며, 표면에 산소함유기들이 증가하는 결과를 보였다. 인산농도와 처리시간이 증가함에 따라 표면에 crack과 etching이 증가하여 표면거칠기가 증가하였으나, 산처리 조건이 강화되면서 폴리케톤 필름의 표면에 degradation이 발생하여 roughness가 감소하는 결과를 보였다. 폴리케톤과 고무와의 계면접착력을 살펴본 결과, pH 0.74에서 120 min, pH 0.4에서 60 min 처리한 경우에 최대 계면접착력을 보였으며, 산처리 조건이 그 이상으로 증가하면서 degradation이 발생하면서 계면접착력이 감소하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.61-64
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• 2005

Recently to repair the structure of deteriorated concrete, LMC rehabilitation method is introduced. however, this method has the possible risks of brittle failure depending on bond performance of the interface. the prediction of interfacial behavior becomes essential to protect the failure. all of the studies which have been done about this field are only about material property such as strength, durability, bond. there is not enough data and studies about structural behavior and numerical analysis. therefore, in this study A flexural nonlinear analysis model of ABAQUS was proposed to predict the load-deflection response, interfacial stress, and ultimate strength. The parameter study showed that overlay thickness was a main influencing factor to the behavior of RC beam overlayed by LMC.

• 한국세라믹학회지
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• 제37권2호
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• pp.128-133
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• 2000

In this work, soft carbons produced by pyrolysis of petroleum and coal-tar pitch were used as the negative electrode for Li-ion batteries. We studeid the charge/discharge capacity and the interfacial reaction of these electrodes by constructing a half cell. Charge/discharge property was studied by a constant-current step and the interfacial reaction between the electrolyte and the surface of a carbon electrode was studied by the cyclic voltammetry. The initial charge/discharge capacity for the coal-tar pitch carbon increased exceedingly with the heat treatment temperature. On hte other hand, the capacity of the petroleum pitch carbon increased with temperature up to 1000$^{\circ}C$, thereafter decreased continuously. While the charge capacity decreased with the cycle number, the reversibility increased above 90%. In addition, the thermal stability and crystallization of petroleum and coal-tar pitches were analyzed by TGA and XRD, respectively.

• 설비공학논문집
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• 제17권4호
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• pp.303-311
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• 2005

The problem of conjugate laminar film condensation of the pure saturated vapor in forced flow over a flat plate has been investigated as boundary layer solutions. A simple and efficient numerical method is proposed for its solution. The interfacial temperature is obtained as a root of 3rd order polynomial for laminar film condensation, and it is presented as a function of the conjugate parameter. The momentum and energy balance equations are reduced to a nonlinear system of ordinary differential equations with four parameters: the Prandtl number, Pr, Jacob number, $Ja^{\ast}$, defined by an overall temperature difference, a property ratio R and the conjugate parameter ${\zeta}$. The approximate solutions thus obtained reveal the effects of the conjugate parameter.

• 한국생산제조학회지
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• 제20권3호
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• pp.284-291
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• 2011

Numerical experiments on biological interfacial layer, DEJ by finite element software ABAQUS have been conducted to study its fracture behavior including crack bridging / arresting characteristics in the model. Crack growth simulation has been carried out by numerical tool, XFEM, devoted to study cracks and discontinuities. The fracture toughness of DEJ has been estimated before and after crack bridging. The implications of bridging in numerical study of fracture behavior of DEJ-like biological interface have been discussed. It has been observed that the results provided by the numerical studies without proper accommodation of bridging phenomenon can mislead. This study can be helpful for understanding the DEJ-like biological interface in terms of its fracture toughness, an important material characteristics. This property of the material is an important measure that has to be taken care during design and manufacturing processes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기물성,응용부문
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• pp.124-126
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• 2002

In this study, composite materials were put to dry interfacial treatment by use of plasma technology. It has been presented that the optimum parameters for the best wettability of the samples at the time of generation of plasma were oxygen atmosphere, 0.1 torr of system pressure, 100 W of discharge power, and 3 minutes of discharge time. Also, the surface resistance rate, dielectric property and tensile strength were improved.

• 대한치과보철학회지
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• 제44권6호
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• pp.683-689
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• 2006

Statement of problem. Interfacial toughness is important in the mechanical property of layered dental ceramics such as core-veneered all-ceramic dental materials. The interfaces between adjacent layers must be strongly bonded to prevent delamination, however the weak interface makes delamination by the growth of lateral cracks along the interface. Purpose. The purpose of this study was to determine the effect of the reaction layer on the interfacial fracture toughness of the core/veneer structure according to the five different divesting. Materials and methods. Thirty five heat-pressed Lithia-based ceramic core bars (IPS Empress 2), $20mm{\times}3mm{\times}2mm$ were made following the five different surface divesting conditions. G1 was no dissolution or sandblasting of the interaction layer. G2 and G3 were dissolved layer with 0.2% HF in an ultrasonic unit for 15min and 30 min. G4 and G5 were dissolved layer for 15min and 30min and then same sandblasting for 60s each. We veneered bilayered ceramic bars, $20mm{\times}2.8mm{\times}3.8mm$(2mm core and 1.8mm veneer), according to the manufacturer's instruction. After polishing the specimens through $1{\mu}m$ alumina, we induced five cracks for each of five groups within the veneer close to interface under an applied indenter load of 19.6N with a Vickers microhardness indenter. Results. The results from Vickers hardness were the percentage of delamination G1:55%, G2:50%, G3:35%, G4:0% and G5:0%. SEM examination showed that the mean thickness of the reaction layer were G1 $93.5{\pm}20.6{\mu}m$, G2 $69.9{\pm}14.3{\mu}m$, G3 $59.2{\pm}20.2{\mu}m$, G4 $0.61{\pm}1.44{\mu}m$ G5 $0{\pm}0{\mu}m$. The mean interfacial delamination crack lengths were G1 $131{\pm}54.5{\mu}m$, G2 $85.2{\pm}51.3{\mu}m$, and G3 $94.9{\pm}81.8{\mu}m$. One-way ANOVA showed that there was no statistically significant difference in interfacial crack length among G1, G2 and G3(p> 0.05). Conclusion. The investment reaction layer played important role at the interfacial toughness of body ceramic bonded to Lithia-based ceramic.