• Transactions of the Korean hydrogen and new energy society
• /
• v.23 no.5
• /
• pp.468-475
• /
• 2012

A proper stacking force and assembly are important to the performance of fuel cell. Improper assembly pressure may lead to leakage of fuels and high interfacial contact resistance, excessive assembly pressure may result in damage to the gas diffusion layer and other components. The pressure distribution of gas diffusion layer is important to make interfacial contact resistance less for stack performance. To analyze the influence of design parameter factors for pressure distribution, and to optimize stack design, DOE (Design of Experiment) was used for polymer electrolyte membrane fuel cell stack pressure test. As commonly known, the higher clamping force improves the fuel cell stack performance. However, non-uniformity of stress distribution is also increased. It shows that optimization between clamping force and stress distribution is needed for well designed structure of fuel cell stack. In this study, stack design optimization method is suggested by using FEM (Finite Element Methode) and DOE for light-weighted fuel cell stack.

• Nuclear Engineering and Technology
• /
• v.52 no.1
• /
• pp.59-68
• /
• 2020

ECCMIX component was introduced in RELAP5/MOD3 for calculating the interfacial condensation. Compared to other existing components in RELAP5, user experience of ECCMIX component is restricted to developmental assessment applications. To evaluate the capability of the ECCMIX component, ECCS experiment was conducted which included single-phase and two-phase thermal mixing. The experiment was carried out with test sections containing a main pipe (70 mm inner diameter) and a branch pipe (21 mm inner diameter) under the atmospheric pressure. The steam mass flow in the main pipe ranged from 0 to 0.0347 kg/s, and the subcooled water mass flow in the branch pipe ranged from 0.0278 to 0.1389 kg/s. The comparison of the experimental data with the calculation results illuminated that although the ECCMIX component was more difficult to converge than Branch component, it was a more appropriate manner to simulate interfacial condensation under two-phase thermal mixing circumstance, while the two components had no differences under single-phase circumstance.

• Composites Research
• /
• v.30 no.3
• /
• pp.175-180
• /
• 2017

Currently, since carbon fiber reinforced plastics (CFRPs) are lightweight and have excellent physical properties, their demand has increased dramatically. Many works have studied the CFRPs based on recycled thermoplastics. In this study, the applicability of recycled composite was evaluated using recycled polyethylene terephthalate (PET). PET was collected from waste materials used in beverage bottles and processed to produce PET films. Optimal thermoforming temperature and time were analyzed by comparing the mechanical properties with forming temperature and time difference for producing PET films. CF mat and PET film were used to determine the suitable parameters for the optimum thermoforming of CF/PET composites. The mechanical properties of each thermoforming condition were verified by bending test. The degree of impregnation of the PET film into the CF mat was evaluated by cross-sectional photographs, whereas the interfacial properties were evaluated by interlaminar shear strength (ILSS). Ultimately, it was confirmed that the thermoforming condition for forming the CF/recycled PET composites yielding the optimal mechanical and interfacial properties was at $270^{\circ}C$ for 5 minutes.

• Composites Research
• /
• v.31 no.5
• /
• pp.186-191
• /
• 2018

Condition and properties of composites with different chemical structure of epoxy matrix were observed after saline solution treatment. Epoxy was used as matrix and the flexibility was controlled by using 2 typed-epoxies and 3 types hardeners (amine, acid anhydride and amide). Saline water treatment was conducted with 6 wt% NaCl solution at $60^{\circ}C$ for 0, 15, and 30 days. Cross section was observed and interfacial and mechanical and properties was evaluated. Amine type exhibited the highest crosslinking density and mechanical and interfacial properties whereas water absorbance was lowest. It is because that the water molecules can be hardly penetrate into the epoxy matrix or the interface between epoxy and glass fiber and it leads to saline water resistance of composites.

• Korean Journal of Materials Research
• /
• v.13 no.8
• /
• pp.497-502
• /
• 2003

Crystallographic characteristics and interfacial structures of $Al_2$$O_3$and $ZrO_2$dielectric films prepared by atomic layer chemical vapor deposition (ALCVD) were investigated at atomic scale by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS)/electron energy-loss spectroscopy (EELS) coupled with a field-emission transmission electron microscope. The results obtained from cross-sectional and plan-view specimens showed that the $Al_2$$O_3$film was crystallized by annealing at a high temperature and its crystal system might be evaluated as either cubic or tetragonal phase. Whereas the $ZrO_2$film crystallized during deposition at a low temperature of ∼$300^{\circ}C$ was composed of both tetragonal and monoclinic phase. The interfacial thickness in both films was increased with the increased annealing temperature. Further, the interfacial structures of X$ZrO_2$$O_3$and $ZrO_2$films were discussed through analyses of EDS elemental maps and EELS spectra obtained from the annealed films, respectively.

• Journal of the Korean Chemical Society
• /
• v.47 no.5
• /
• pp.472-478
• /
• 2003

In this work, the zeolite/diglycidylether of bisphenol A(DGEBA) systems were investigated in terms of the cure kinetics and mechanical interfacial properties of the composites. The 4, 4-diamino diphenyl methane(DDM) was used as a curing agent for epoxy. Two types of zeolite(PZ) were prepared with 15 and 35 wt% KOH treatments(15-BZ and 35-BZ, respectively) for 24 h, and their surface characteristics were studied by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction(XRD). Cure kinetics of the composites were examined in the context of differential scanning calorimetry(DSC), and mechanical interfacial properties were investigated in critical stress intensity factor($K_{IC}$) and critical strain energy release rate($G_{IC}$). In the results of XPS and XRD, sodium ion(Na) of zeolite was exchanged for potassium ion(K), resulting from the treatment of KOH. Also, $Si_{2p}/Al{2p}$ composition ratios of the treated zeolite were increased, which could be attributed to the weakening of Al-O bond in framework. Cure activation energy($E_a$) of 15-BZ composites was decreased, whereas KIC and $G_{IC}$ were increased, compared with those of the pure zeolite/DGEBA composites. It was probably accounted that the acidity of zeolite was increased by surface treatments and the cure reaction between zeolite and epoxy was influenced on the increased acidity of zeolite.

• Journal of the Microelectronics and Packaging Society
• /
• v.16 no.3
• /
• pp.31-37
• /
• 2009

Cu-Cu thermo-compression bonding process was successfully developed as functions of the $N_2+H_2$ forming gas annealing conditions before and after bonding step in order to find the low temperature bonding conditions of 3-D integrated technology where the quantitative interfacial adhesion energy was measured by 4-point bending test. While the pre-annealing with $N_2+H_2$ gas below $200^{\circ}C$ is not effective to improve the interfacial adhesion energy at bonding temperature of $300^{\circ}C$, the interfacial adhesion energy increased over 3 times due to post-annealing over $250^{\circ}C$ after bonding at $300^{\circ}C$, which is ascribed to the effective removal of native surface oxide after post-annealing treatment.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.1882-1887
• /
• 2007

In the present experimental study, the effect of interfacial tensions on pressure drop of air-water two-phase flow in round mini-channels was investigated. A glass (highly wettable) tube and a Teflon (poorly wettable) tube, both in 350 mm length but 1.8 mm and 1.59 mm in inner diameters each, were used for the tests. All the experiments were performed only in the plug flow regime, confirmed by visualization. In the glass tube, the gas plugs were surrounded by the liquid film along the inner periphery. On the other hand, the inner wall remained dry at the gas portion in the Teflon tube. The pressure drop of the plug flow in the Teflon tube without the liquid film) appeared much larger than in the glass tube (with the liquid film) due to dissipation of energy by movement of the wetting lines. In this paper, various correlations on the two-phase pressure drop of plug flows were compared and a modified correlation was proposed, taking account of the surface wettability.

• Journal of the Korean Chemical Society
• /
• v.23 no.4
• /
• pp.210-216
• /
• 1979

A simple method to calculate the interfacial tension between two immiscible molten polymers has been developed. The theory is based on the significant structure theory of liquids. The energy of adhesion is expressed as a geometric mean of the cohesion energies multiplied by correction factor $({\Phi}12)$, ${\Delta}E_{12}={\Phi}_{12}\sqrt{{\Delta}E_{11}{\Delta}E_{22^{\circ}}$. In the calculation of ${\Delta}E_{11}\;and\;{\Delta}E_{22}$, a quasilattice of polymer chains has been assumed. It is assured that, besides the dispersion force, the polar force interactions between polymer constituent groups should be considered in the calculation of the interfacial tensions.

• Journal of the Korean Vacuum Society
• /
• v.6 no.3
• /
• pp.263-266
• /
• 1997

We studied an interfacial characteristics of $In_{0.1}Ga_{0.9}As$/ GaAs by photoreflectance (PR) measurement at room temperature. With increasing thickness of epitaxial layer, Franz-Keldysh oscillation (FKO) periods of PR signals were decreased, and interfacial electric field was decreased. This can be explained by the increases of defects due to lattice mismatch near the heterointerface between InGaAs and GaAs. For the thickness of epitaxial layer thinner than the 300$\AA$, InGaAs epitazial layer closed to critical thickness and increased strain, and then the bandgap energy shifted high greatly.