• 한국재료학회지
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• 제15권6호
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• pp.382-387
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• 2005

Polyvinylidene fluoride (PVDF) surface was irradiated and became superhydrophilic by low energy (180 eV) and high flux $(\~10^{15}/cm{\cdot}s)$ ion beam. As an ion source, a closed electron Hall drift thruster of $\phi=70mm$ outer channel size without grid was adopted. Ar, $O_2$ and $N_2O$ were used for source gases. When $N_2O^+$ and $O_2^+$ reactive gas ion beam were irradiated with the ion fluence of $5\times10^{15}/cm^2$, the wetting angle for deionized water was drastically dropped from $61^{\circ}\;to\;4^{\circ}\;and\;2^{\circ}$, respectively. Surface energy was also increased up to from 44 mN/m to 81 mN/m. Change of chemical component in PVDF surface was analyzed by x-ray photoelectron spectroscopy. Such a great increase of the surface energy was intimately related with the increase of hydrophilic group component in reactive ion irradiated PVDF surfaces. By using an atomic force microscopy, the root-mean-square of surface roughness of ion irradiated PVDF was not much altered compared to that of pristine PVDF.

• 한국재료학회지
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• 제31권12호
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• pp.704-709
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• 2021

In the flux used in the batch galvanizing process, the effect of the component ratio of NH₄Cl to ZnCl₂ on the microstructure, coating adhesion, and corrosion resistance of Zn-Mg-Al ternary alloy-coated steel is evaluated. Many defects such as cracks and bare spots are formed inside the Zn-Mg-Al coating layer during treatment with the flux composition generally used for Zn coating. Deterioration of the coating property is due to the formation of AlCl_x mixture generated by the reaction of Al element and chloride in the flux. The coatability of the Zn-Mg-Al alloy coating is improved by increasing the content of ZnCl₂ in the flux to reduce the amount of chlorine reacting with Al while maintaining the flux effect and the coating adhesion is improved as the component ratio of NH₄Cl to ZnCl₂ decreases. Zn-Mg-Al alloy-coated steel products treated with the optimized flux composition of NH₄Cl·3ZnCl₂ show superior corrosion resistance compared to Zn-coated steel products, even with a coating weight of 60 %.

• 치위생과학회지
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• 제22권3호
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• pp.191-198
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• 2022

Background: The purpose of this study was to evaluate the composition of the crystal phases of various calcium silicate-based materials (CSMs): ProRoot white MTA^Ⓡ (mineral trioxide aggregate) (WMTA), Ortho MTA^Ⓡ (OM), Endocem MTA^Ⓡ (EM), Retro MTA^Ⓡ (RM), Endocem Zr^Ⓡ (EN-Z), Biodentine^TM (BD), EZ-seal^TM (EZ), and OrthoMTA III (OM3). Methods: In a sample holder, 5 g of the powder sample was placed and the top surface of the material was packed flat using a sterilized glass slide. The prepared slides were mounted on an X-ray diffraction (XRD) instrument (D8 Advance; Bruker AXS GmbH, Germany). The X-ray beam 2θ angle range was set at 10~90° and scanned at 1.2° per minute. The Cu X-ray source set to operate at 40 kV and 40 mA in the continuous mode. The peaks in the diffraction pattern of each sample were analyzed using the software Diffrac (version 2.1). Then, the peaks were compared and matched with those of standard materials in the corresponding Powder Diffraction File (PDF-2, JCPDS International Center for Diffraction Data). A powder samples of the materials were analyzed using XRD and the peaks in diffraction pattern were compared to the Powder Diffraction File data. Results: Eight CSMs showed a similar diffraction pattern because their main component was calcium silicate. Eight CSMs showed similar diffraction peaks because calcium silicate was their main component. Two components were observed to have been added as radiopacifiers: bismuth oxide was detected in WMTA, OM, and EM while zirconium oxide was detected in RM, EN-Z, BD, EZ, and OM3. Unusual patterns were detected for the new material, OM3, which had strong peaks at low angles. Conclusion: It was caused by the presence of Brushite, which is believed to have resulted in crystal growth in a particular direction for a specific purpose.

• 비파괴검사학회지
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• 제23권6호
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• pp.635-644
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• 2003

To ensure the reliability of ultrasonic nondestructive testing techniques for modern structural materials, the effects of anisotropy and inhomogeneity and the influence of non-planar component geometries on ultrasonic wave propagation have to be taken into account. In this article, fundamentals and applications of two analytical approaches to three-dimensional elastic beam field calculation are presented. Results for both isotropic materials including curved interfaces and for anisotropic media like composites are presented, covering field profiles for various types of transducers and the modeling of time-dependent rf-signals.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.77-80
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• 2002

Thermal analysis has been performed to evaluate the thermal effect on composite antenna (Ka-band) structure in space environment. The concepts of thermal control are also presented to maintain the antenna components within respective temperature limits. A steady-state algorithm of I-DEAS' thermal analysis software was utilized to predict both maximum and minimum temperature, maximum gradient temperature, and temperature distribution on each antenna component.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2003년도 The Korea-Japan Joint Symposium
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• pp.96-96
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• 2003

In this article modification of wool fibers and fabrics by pulse corona discharge and enzymes, in particular purified keratinase with a single component has been carried out to improve their surface properties. The shrinkproofing, tensile strength, weight loss, and the primary hand values calculated from the mechanical properties of the dual treated wool fabrics were investigated. In addition, the surface morphology of wool fiber was observed under the dry and wet conditions using an environmental SEM, ESEM.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 1998년도 가을 학술발표회논문집
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• pp.199-202
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• 1998

Random copolymers are widely used as materials since they afford a convenient possibility of adjusting properties through the compositions of the copolymers. In the case of semicrystalline polymers, the degree of crystallinity generally decreases as the content of the minor component increases, leading often to fully amorphous materials even at low concentrations of the comonomer. (omitted)

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1378-1383
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• 2003

A ferroelectric (called piezoelectric afterwards) wafer has been widely used as a key component of actuators or sensors of a layer type. According to recent researches, the piezoelectric wafer behaves in a nonlinear way under excessive electro-mechanical loadings. In the present paper, one-dimensional constitutive equations for the nonlinear behavior of a piezoelectric wafer are proposed based on the principles of thermodynamics and a simple viscoplasticity theory. The predictions of the developed model are compared with experimental observations.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.816-817
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• 2006

Hydrogen, in even small quantities, is extremely deleterious to the sintering of aluminium. Understanding the cause of this effect is complicated by the multiple interactions that occur in multi-component systems. In this work, we examine the sintering rsponse of Al-2Mg (a simplified system) in pure nitrogen and nitrogen-hydrogen using dilatometry, differential scanning calorimetery, thermogravimetry and metallography.

• Journal of the Optical Society of Korea
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• 제8권1호
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• pp.21-28
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• 2004

When femtosecond laser pulses are focused inside the bulk of transparent materials, the intensity in the focal volume becomes high enough to produce permanent structural modifications. This technique has been applied to fabricate three-dimensional photonic structures such as optical memory, waveguides, gratings, and couplers inside a wide variety of transparent materials. In this paper, we review the fabrication of optical elements in glasses with femtosecond laser pulses, including the fabrication of waveguides, couplers, Bragg gratings, zone plates, holographic memory, and micro holes.