The engineered barrier system (EBS) is an indispensable element of a deep geological repository (DGR) designed to prevent the discharge of radioactive materials into the environment. The buffer material is a vital component of the EBS by creating a physical and chemical barrier that prevents the migration of radioactive materials. In the disposal environment, gases can be generated from the corrosion of the canister. When the gas generation rate exceeds the diffusion rate, the buffer material’s performance can deteriorate by the physical damage induced by the increase in pore pressure. Therefore, understanding the EBS’s behavior under gas generation conditions is crucial to guarantee the longterm safety and performance of the DGR. Lab-scale and field-scale experiments have been conducted to examine the stability of the buffer material concerning gas generation and movement by the previous researchers. To evaluate long-term stability for more than 100,000 years, it is essential to assess stability using a numerical model verified by these experiments. This study investigated the effect of interfacial characteristics on the numerical modeling accuracy of experimental simulation while verifying a numerical model through field-scale experimental results. The findings of this study are expected to furnish fundamental data for establishing numerical analysis guidelines for the longterm stability assessment of disposal systems.

In order to broaden the range of application of light weight aluminum alloys, it is necessary to enhance the mechanical properties of the alloys and combine them with other materials, such as cast iron. In this study, the effects of adding small amounts of Cu and Zr to the Al-Si-Mg based alloy on tensile properties and corrosion characteristics were investigated, and the effect of the addition on the interfacial compounds layer with the cast iron was also analyzed. Although the tensile strength of the Al-Si-Mg alloy was not significantly affected by the additions of Cu and Zr, the corrosion resistance in 3.5 %NaCl solution was found to be somewhat lowered in this research. The influence of Cu and Zr addition on the type and thickness of the interfacial compounds layer formed during compound casting with cast iron was not significant, and the main interfacial compounds were identified to be Al5FeSi and Al8Fe2Si phases, as in the case of the Al-Si-Mg alloys.

To enhance the thermal properties of epoxy composites, expanded graphite (EG) was oxyfluorinated and embedded into epoxy resin as a reinforcement. The maximum thermal conductivity was obtained for epoxy composites with oxyfluorinated EG, representing a 62% increase compared to that of neat epoxy. Additionally, the glass transition temperature (Tg) and integral procedural decomposition temperature of epoxy composites with oxyfluorinated EG show the increase of 6% (4.4 °C) and 106% (264 °C), respectively, which indicated the improvement in thermal stability. These results can be attributed to the interfacial interaction between epoxy and oxyfluorinated EG, which formed strong interfacial interactions between the epoxy resin and EG due to the presence of oxygen- and fluorine-containing functional groups in oxyfluorinated EG.

Since the directly bonded interface between TiAl alloy and SCM440 includes lots of cracks and generated intermetallic compounds(IMCs) such as TiC, FeTi, and Fe2Ti, the interfacial strength can be significantly reduced. Therefore, in this study, Cu is selected as an insert metal to improve the lower tensile strength of the joint between TiAl alloy and SCM440 during friction welding. As a result, newly formed IMCs, such as Cu2TiAl, CuTiAl, and TiCu2, are found at the interface between TiAl alloy and Cu layer and the thickness of IMCs layers is found to vary with friction time. In addition, to determine the relationship between the thickness of the IMCs and the strength of the welded interfaces, a tensile test was performed using sub-size specimens obtained from the center to the peripheral region of the friction-welded interface. The results are discussed in terms of changes in the IMCs and the underlying deformation mechanism. Finally, it is found that the friction welding process needs to be idealized because IMCs generated between TiAl alloy and Cu act to not only increase the bonding strength but also form an easy path of fracture propagation.

An Al2O3/AlN bilayer deposited on GaN by atomic layer deposition (ALD) is employed to prepare Al2O3/AlN/GaN metal-insulator-semiconductor (MIS) diodes, and their interfacial properties are investigated using X-ray photoelectron spectroscopy (XPS) with sputter etch treatment and current-voltage (I-V) measurements. XPS analyses reveal that the native oxides on the GaN surface are reduced significantly during the early ALD stage, indicating that AlN deposition effectively clelans up the GaN surface. In addition, the suppression of Al-OH bonds is observed through the ALD process. This result may be related to the improved device performance because Al-OH bonds act as interface defects. Finally, temperature dependent I-V analyses show that the barrier height increases and the ideality factor decreases with an increase in temperature, which is associated with the barrier inhomogeneity. A Modified Richardson plot produces the Richardson constant of A** as 30.45 Acm−2K−2, which is similar to the theoretical value of 26.4 Acm−2K−2 for n-GaN. This indicates that the barrier inhomogeneity appropriately explains the forward current transport across the Au/Al2O3/AlN/GaN interface.

Native soy protein is known to possess poor interfacial activity compared to flexible proteins. Acidification could alter its structure in a way that improves its interfacial activity. This study aimed to investigate the effects of seven acids, including hydrochloric, acetic, ascorbic, lactic, malic, citric, and tartaric acid on the oil-water interfacial properties and oil-in-water emulsifying properties of soy protein isolate (SPI) at pH 3.0. The aqueous solutions of 1.5 %(w/v) SPI were adjusted to pH 3.0 with different acids, and the solution without acidification (pH 8.0) was used as a control. The zeta potential of acidified SPI solutions and SPI emulsions were positive value while it was negative value for control. The particle sizes of acidified SPI solutions were between 19-83 m (107 m for the control). The particle size of acidified SPI emulsions were 0.4 m for control, acetic, ascorbic, lactic, and malic, 1.2 m for citric and tartaric, while 20.7 m for HCl. The interfacial pressure between soybean oil and the acidified SPI solutions were between 12.7-15.4 mN/m, while SPI-control was significantly higher than that at 19.4 mN/m. The acidified SPI solution had the meaningful values of interfacial shear rheological parameters and showed viscoelastic layer, but the control was almost no viscoelastic layer. All acidified SPI emulsion showed much higher emulsifying activity index (130-158 m2/g) than the control (111 m2/g). The appearance of emulsion looked no difference over the time when observed by eyes. The evaluation of emulsion stability by the changing of particle size distribution within 40 days showed that the control and HCl was no change, while the others tended to increase particle size.

The synthesis of octenyl succinyl β-gucan (OSA-β-glucan) was carried out and its interfacial properties at the oil-water interface and in emulsion systems were investigated. An aqueous ethanol system as a reaction media was used to facilitate the synthesis process; 10% (w/w) ethanol found to be the best as it showed a maximum degree of substitution (DS: 0.0132). FT-IR showed a characteristic absorption spectrum at 1736cm-1, indicating the esterification of octenyl succinyl groups to β-glucan backbone. As for interfacial tension measurements, it was decreased with increasing concentration of OSA-β-glucan in the aqueous phase and when NaCl was added to aqueous OSA-β-glucan solution in the range of 0.01 M to 0.1 M and also when pH was raised (pH 3 ~ pH 9). In systems of emulsion stabilized with OSA-β-glucan, fat globule size found to decrease with increasing concentration of OSA-β-glucan, showing a critical value of about 0.32μm at 0.5 wt%. When the OSA-β-glucan emulsions were stored, it was found that fat globule size was increased with storage time and particularly pronounced increase was observed in emulsion with 1% OSA-β-glucan, possibly due to depletion flocculation. Results of creaming stability evaluated by light scattering technique showed that it was more stable in emulsions containing smaller fat globule size. Surface load of OSA-β-glucan in emulsions increased with increasing concentration of OSA-β-glucan, suggesting a multilayer adsorption.

This study reports on the influenceof N-butyl-N-methylpyrrolidinium tetrafluoroborat (PYR14BF4) ionic liquid additive on the conducting and interfacial properties of organic solvent based electrolytes against a carbon electrode. We used the mixture of ethylene carbonate/dimethoxyethane (1:1) as an organic solvent electrolyte and tetraethylammo-nium tetrafluoroborate(TEABF4) as a common salt. Using the PYR14BF ionic liquid as additive produced higher ionic conductivity in the electrolyte and lower interface resis-tance between carbon and electrolyte, resulting in improved capacitance. The chemical and electrochemical stability of the electrolyte was measured by ionic conductivity me-ter and linear sweep voltammetry. The electrochemical analysis between electrolyte and carbon electrode was examined by cyclic voltammetry and electrochemical impedance spectroscopy.

The blending effects of surfactants on the polystyrene emulsion polymerization were studied. The blending of Triton X-100 and SDS affects to the interfacial properties of the styrene monomer and water phases, and finally, the properties of the polystyrene latex particles. As the blending ratio of SDS/Triton X-100 increases, the interfacial tension and CMC of the blended surfactants were decreased and results in a reducing the size of the latex particles. It was found that the interfacial tension was reduced when the surfactant were blended. By increasing the SDS content, the interfacial tension was reduced, and, at a certain condition, the interfacial tension was reached to an extremely low value to form micro-emulsion and the nano-sized latex particles (80~110 nm).

Diamond/SiC composites are appropriate candidate materials for heat conduction as well as high temperature abrasive materials because they do not form liquid phase at high temperature. Diamond/SiC composite consists of diamond particles embedded in a SiC binding matrix. SiC is a hard material with strong covalent bonds having similar structure and thermal expansion with diamond. Interfacial reaction plays an important role in diamond/SiC composites. Diamond/SiC composites were fabricated by high temperature and high pressure (HPHT) sintering with different diamond content, single diamond particle size and bi-modal diamond particle size, and also the effects of composition of diamond and silicon on microstructure, mechanical properties and thermal properties of diamond/SiC composite were investigated. The critical factors influencing the dynamics of reaction between diamond and silicon, such as graphitization process and phase composition, were characterized. Key factor to enhance mechanical and thermal properties of diamond/SiC composites is to keep strong interfacial bonding at diamond/SiC composites and homogeneous dispersion of diamond particles in SiC matrix.

The effects of fiber surface-treatment and sizing on the dynamic mechanical properties of unidirectional and 2-directional carbon fiber/nylon 6 composites by means of dynamic mechanical analysis have been investigated in the present study. The interlaminar shear strengths of 2-directional carbon/nylon 6 composites sized with various thermosetting and thermoplastic resins are also measured using a short-beam shear test method. The result suggests that different surface-treatment levels onto carbon fibers may influence the storage modulus and tan δ behavior of carbon/nylon 6 composites, reflecting somewhat change of the stiffness and the interfacial adhesion of the composites. Dynamic mechanical analysis and short-beam shear test results indicate that appropriate use of a sizing material upon carbon fiber composite processing may contribute to enhancing the interfacial and/or interlaminar properties of woven carbon fabric/nylon 6 composites, depending on their resin characteristics and processing temperature.

In this work, the effect of a direct oxyfluorination on surface and mechanical interfacial properties of PAN-based carbon fibers is investigated. The changes of surface functional groups and chemical composition of the oxyfluorinated carbon fibers are determined by FT-IR and XPS measurements, respectively. ILSS of the composites is also studied in terms of oxyfluorination conditions. As a result, FT-IR exhibits that the carboxyl/ester groups (C=O) at 1632 cm-1 and hydroxyl group (O-H) at 3450 cm-1 are observed in the oxyfluorinated carbon fibers. Especially, the oxyfluorinated carbon fibers have a higher O-H peak intensity than that of the fluorinated ones. XPS result also shows that the surface functional groups, including C-O, C=O, HO-C=O, and C-Fx after oxyfluorination are formed on the carbon fiber surfaces, which are more efficient and reactive to undergo an interfacial reaction to matrix materials. Moreover, the formation of C-Fx physical bonding of the carbon fibers with fluorine increases the surface polarity of the fibers, resulting in increasing ILSS of the composites. This is probably due to the improvement of interfacial adhesion between fibers and matrix resins.

The effect of electrochemical surface treatments in KOH chemical solution on microstructures of carbon blacks was investigated in terms of surface functional values and XRD measurements. And their mechanical interfacial properties of the carbon blacks/rubber composites were studied by the composite tearing energy (GIIIC). It was found that the development of basic-surface functional groups lead to the significant physical changes of carbon blacks, such as, decrease of the interlayer spacing (d002), increase of the crystalline size along c-axis (Lc), and increase of degree of crystalline (χc). This treatment is possibly suitable for carbon blacks to be incorporated in a hydrocarbon rubber matrix, resulting in improving the hardness and tearing energy of the resulting composites.

Sophorolipids were biosynthesized using a strain of yeast, Torulopsis bombicola ATCC22214. It has been reported that this yeast gives the highest yields for the production of biosurfactant sophorolipids. Hence, this yeast was used in this study. One of the objectives of this study is to increase the yield of the sophorolipid synthesis. To meet this end, basic culture medium was formulated on the basis of literature research to-date. When this medium was used, the increase in yield from 15% to 150% was observed compared to using the media in the literature. To examine how the interfacial characteristics of sophorolipids change with substrate, glucose (the first carbon source) was maintained in the media and after being cultured for three days, the second carbon sources such as alkanes, vegetable oils, alcohols or organic acids were added. The whole broth was extracted twice with ethyl acetate and the extract was analyzed by thin layer chromatograhy(TLC). After qualitative analyses by TLC, surface tensions of sophorolipids were measured by the Wilhelmy plate method and critical micelle concentration(CMC) was determined using these surface tension data. Also, interfacial tensions were measured by the spinning drop method and emulsions of the three-component water/decane/sophorolipid system were tested. Sophorolipids were effective and efficient in terms of surface tension reduction and CMC, but they were ineffective as emulsifiers because emulsions were separated within 30 minutes.

Sn-3.5Ag, Sn-3.5Ag-lZn Eoa납과 Cu기판과의 계면반응 및 접합특성에 관하여 검토하였다. Eoa납과 Cu기판이 접합된 시편은 100˚C와 160˚C에서 60일간 열처리하였으며, 전단하중을 가하여 강도를 측정하였다. 150˚C에서 열처리에 따른 계면반응층의 두게는 Sn-3.5Ag/Cu계면이 Sn-3.5A9-IZn/Cu계면보다 빠르게 성장하였으며, 반응생성물 성장은 t1/2에 비례하여 체적 확산 경향을 나타냈다. 계면 반응생성물은 Sn-3.5Ag/Cu계면의 경우 Cu6Sn5상이 형성되었고, Ag3Sn상은 반응층 내부 및 반응층과 땜납의 계면에 석출하였으며, Zn을 첨가한 경우에는 계면에 Cu6Sn5 상과 함께 Cu5Zn8상이 형성되었다. 땜납/기판의 전단강도는 Sn-3.5Ag합금에 Zn을 1% 첨가하면 증가하였으며, 열처리를 한 경우에는 감소하였다.

Sn-Bi-X(X:2Cu, 2Sb, 5In) 계 땜납과 Cu 기판과의 계면반응 및 기계적성질에 대하여 고찰하였다. Cu판과 땜납의 접합부는 100˚C에서 60일까지 열처리하여 광학현미경, SEM, EDS,분석을 통하여 시효처리에 따른 미세조직과 계면반응을 분석하였으며, 인장강도 및 연신율은 제조된 시편을 30일까지 열처리 한 후 0.3mm min-1로 인장하여 시험하였다. 미세조직 분석결과 Cu의 첨가로 미세조직이 미세화 됨을 알 수 있으며, 계면에 형성된 화합물은 첨가원소에 따라 다르게 나타났다. 인장시험 결과 열처리 초기에는 땜납쪽에서의 파괴가 발생하였으나 열처리 시간이 증가하면서 계면반응층고 땜납의 계면에서 파괴가 발생하였다. 열처리에 따른 인장강도는 Cu를 첨가한 경우에 가장 높은 값을 나타냈다.