• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.356.2-356.2
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• 2014

Spin Transfer Torque (STT) is of great interest in data writing scheme for the Magneto-resistive Random Access Memory (MRAM) using Magnetic Tunnel Junction (MTJ). Scalability for high density memory requires ferromagnetic electrodes having the perpendicular magnetic easy axis. We investigated CoZr as the ferromagnetic electrode. It is observed that interfacial magnetic anisotropy is preferred perpendicular to the plane with thickness dependence on the interfaces with Pt layer. The anisotropy energy (Ku) with thickness dependence shows a change of magnetic-easy-axis direction from perpendicular to in-plane around 1.2 nm of CoZr. The interfacial anisotropy (Ki) as the directly related parameters to switching and thermal stability, are estimated as $1.64erg/cm^2$ from CoZr/Pt multilayered system.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.127-134
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• 2015

Recently, the external bonding of carbon fiber reinforced polymer (CFRP) sheets has come to be regarded as a very effective method for strengthening of reinforced concrete structures. The behavior of CFRP-strengthened RC structure is mainly governed by the interfacial behavior, which represents the stress transfer and relative slip between concrete and the CFRP sheet. In this study, the effects of bonded length, width and concrete strength on the interfacial behavior are verified and a bond-slip model is proposed. The proposed bond-slip model has nonlinear ascending regions and exponential descending regions, facilitated by modifying the conventional bilinear bond-slip model. Finite element analysis results of interface element implemented with bond-slip model have shown good agreement with the experimental results performed in this study. It is found that the failure load and strain distribution predicted by finite element analysis with the proposed bond-slip are in good agreement with results of experiments.

• Journal of Adhesion and Interface
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• v.7 no.2
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• pp.1-11
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• 2006

Interfacial evaluation of the untreated and treated Jute and Hemp fibers reinforced different matrix polypropylene-maleic anhydride polypropylene copolymer (PP-MAPP) composites were investigated by micromechanical technique and dynamic contact angle measurement. For the statistical tensile strength of Jute and Hemp fibers, bimodal Weibull distribution was fitted better than the unimodal distribution. The acid-base parameter on the interfacial shear strength (IFSS) of the natural fiber composites was characterized by calculating the work adhesion, $W_a$. The effect of alkaline, silane coupling agent on natural fibers were obtained with changing MAPP content in PP-MAPP matrices. Alkaline treated fibers made the surface energy to be higher due to removing the weak boundary layers and thus increasing surface area, whereas surface energy of silane treated Jute and Hemp fibers decreased due to blocked high energy sites. MAPP in the PP-MAPP matrix caused the surface energy to increase due to introduced acid-base sites. Microfailure modes of two natural fiber composites were observed clearly differently due to different tensile strength of natural fibers.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.384-388
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• 2013

Fluorine-doping on the $Li_{1+x}Mn_{1.9-x}Al_{0.1}O_4$ spinel cathode materials is found to alter crystal shape, and enhance initial interfacial reactivity and solid electrolyte interphase (SEI) formation, leading to improved initial coulombic efficiency in the voltage region of 3.3-4.3 V vs. Li/$Li^+$ in the room temperature electrolyte of 1 M $LiPF_6$/EC:EMC. SEM imaging reveals that the facetting on higher surface energy plane of (101) is additionally developed at the edges of an octahedron that is predominantly grown with the most thermodynamically stable (111) plane, which enhances interfacial reactivity. Fluorine-doping also increases the amount of interfacially reactive $Mn^{3+}$ on both bulk and surface for charge neutrality. Enhanced interfacial reactivity by fluorine-doping attributes instant formation of a stable SEI layer and improved initial cyclic efficiency. The data contribute to a basic understanding of the impacts of composition on material properties and cycling behavior of spinel-based cathode materials for lithium-ion batteries.

• Elastomers and Composites
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• v.37 no.4
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• pp.258-264
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• 2002

In this work, the influence of thermal treatment on surface properties of silicas and mechanical interfacial properties of silicas/polyurethane composites was investigated. The surface properties of thermally treated silicas were studied in the context of Fourier Transform-IR (FT-IR), solid-state 29Si NMR spectroscopy, and contact angle. And the mechanical interfacial properties of the silica/polyurethane composites were evaluated by composite tearing energy (GIIIC). As a result, it was found that the thermally treated silica surfaces became hydrophobic in nature, due to the condensation of surface hydroxyls and the formation of siloxane bonds, resulting in increasing the London dispersive component of surface free energy. From which, the increase of the London dispersive component of the silicas led to an improvement of the dispersion of silicas in a polyurethane matrix, finally resulting in improving the tearing energy (GIIIC) of the silicas/polyurethane composites.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.476-482
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• 2013

In this work, the effects of electrochemical oxidation of carbon fiber surfaces on mechanical interfacial properties of carbon fibers-reinforced polarized-polypropylene matrix composites were studied with various current densities during the treatments. Surface properties of the fibers before and after treatments were observed by SEM, AFM, XPS, and contact angle measurements. Mechanical interfacial properties of the composites were measured in terms of critical stress intensity factor ($K_{IC}$). From the results it was found that $O_{1s}$ peaks of the fiber surfaces were strengthened after electrochemical oxidation which led to the enhancement of surface free energy of the fiber, resulting in good mechanical performance of the composites. It can be concluded that electrochemical oxidation of the carbon fiber surfaces can control the interfacial adhesion between the carbon fibers and polarized-polypropylene in this composites system.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.524-532
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• 2018

In this study, two types of amino acids-based anionic biosurfactants such as potassium cocoyl glutamate (CTK) and sodium cocoyl glutamate (CTN) were synthesized from coconut oils and the structure elucidation of CTK and CTN was carried out by using FT-IR, $^1H-NMR$ and $^{13}C-NMR$ spectrophotometries. Measurements of interfacial properties such as static and dynamic surface tensions and emulsification activity showed that both CTK and CTN were surface-active and effective in lowering the interfacial free energy. In particular, the CTK surfactant was found to be more efficient in reducing the interfacial free energy since the larger number of CTK molecules was preferentially adsorbed at the air-water interface due to the higher hydrophobicity and larger mobility of CTK than those of using CTN, indicating possible uses in cosmetics and household products formulation.

• Journal of Powder Materials
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• v.18 no.5
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• pp.430-436
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• 2011

Joining of NiO-YSZ to 316 stainless steel was carried out with B-Ni2 brazing alloy (3 wt% Fe, 4.5 wt% Si, 3.2 wt% B, 7 wt% Cr, Ni-balance, m.p. 971-$999^{\circ}C$) to seal the NiO-YSZ anode/316 stainless steel interconnect structure in a SOFC. In the present research, interfacial (chemical) reactions during brazing at the NiO-YSZ/316 stainless steel interconnect were enhanced by the two processing methods, a) addition of an electroless nickel plate to NiO-YSZ as a coating or b) deposition of titanium layer onto NiO-YSZ by magnetron plasma sputtering method, with process variables and procedures optimized during the pre-processing. Brazing was performed in a cold-wall vacuum furnace at $1080^{\circ}C$. Post-brazing interfacial morphologies between NiO-YSZ and 316 stainless steel were examined by SEM and EDS methods. The results indicate that B-Ni2 brazing filler alloy was fused fully during brazing and continuous interfacial layer formation depended on the method of pre-coating NiO-YSZ. The inter-diffusion of elements was promoted by titanium-deposition: the diffusion reaction thickness of the interfacial area was reduced to less than 5 ${\mu}m$ compared to 100 ${\mu}m$ for electroless nickel-deposited NiO-YSZ cermet.

• Elastomers and Composites
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• v.45 no.1
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• pp.2-6
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• 2010

The sizing treatments of PAN-based carbon fiber surfaces were carried out in order to improve the interfacial adhesion in the carbon fibers/nylon6 composite system. The parameter to characterize the wetting performance and surface free energy of the sized fibers were determined by a contact angle method. The mechanical interfacial properties of the composites were investigated using critical stress intensity factor ($K_{IC}$). The cross-section morphologies of sized CFs/nylon6composites were observed by SEM. As the experimental results, it was observed that silane-based sizing treated carbon fibers showed higher surface free energies than other sizing treatments. In particular, the KIC of the sizing-treated carbon fibers reinforced composites showed higher values than those of untreated carbon fibers-reinforced composites. This result indicated that the increase in the surface free energy of the fibers leads to the improvement of the mechanical interfacial properties of carbon fibers/nylon6 composites.

• Journal of Welding and Joining
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• v.30 no.3
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• pp.26-31
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• 2012

Three-dimensional integrated circuit (3D IC) technology has become increasingly important due to the demand for high system performance and functionality. We have evaluated the effect of Buffered oxide etch (BOE) on the interfacial bonding strength of Cu-Cu pattern direct bonding. X-ray photoelectron spectroscopy (XPS) analysis of Cu surface revealed that Cu surface oxide layer was partially removed by BOE 2min. Two 8-inch Cu pattern wafers were bonded at $400^{\circ}C$ via the thermo-compression method. The interfacial adhesion energy of Cu-Cu bonding was quantitatively measured by the four-point bending method. After BOE 2min wet etching, the measured interfacial adhesion energies of pattern density for 0.06, 0.09, and 0.23 were $4.52J/m^2$, $5.06J/m^2$ and $3.42J/m^2$, respectively, which were lower than $5J/m^2$. Therefore, the effective removal of Cu surface oxide is critical to have reliable bonding quality of Cu pattern direct bonds.