• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.859-864
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• 1991

High quality lead titanate thin films were fabricated by spin coating on a silicon substrate. The resulting dried gel layers were uniform in thickness through 2$\times$2 $\textrm{cm}^2$ area, and polycrystalline perovskite structures developed almost crack free with a heat treatment above 50$0^{\circ}C$ in films with thickness above 360 nm. Metastable pyrochlore structures were observed in films with thickness of 160 nm when heat treated at 500 and $600^{\circ}C$, but these structure did not appear in films with thickness of 360 nm. The thickness dependence in crystal structure of films was studied. by varying the substrate condition and analyzing the interface between the film and substrate. In native oxide films on silicon stbstrates, amorphous dried gel layers were heterogeneously nucleated. Metastable cubic pyrochlore structure could be crystallized in amorphous native oxide.

• Journal of Electrochemical Science and Technology
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• v.9 no.1
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• pp.1-8
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• 2018

The effect of mixing ratio on the corrosion protection of carbon steel coated by a film composed of poly(vinylidene) fluoride (PVDF) and poly(methyl methacrylate) (PMMA) was examined using electrochemical impedance spectroscopy. Surface crystallization behavior and thermal properties of the PVDF/PMMA coated carbon steel were evaluated using polarized optical microscopy and differential scanning calorimetry, respectively. A Maltese cross-pattern spherulite crystal was observed in the PVDF/PMMA coating film, which became more apparent with increasing PVDF content. The highest corrosion protection performance was achieved with 60 wt.% PVDF-coated carbon steel, and delamination and corrosion reactions were observed for 20 wt.% PVDF-coated carbon steel. Further, corrosion protection performance with an amorphous/crystal mixture (PVDF/PMMA, 60/40 (w/w)) was better than those observed in the amorphous domain and the perfect-crystal domain of the PVDF/PMMA blended coating system.

• Journal of the Korean institute of surface engineering
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• v.38 no.1
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• pp.37-43
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• 2005

Nanosized titanium-colloid particles were prepared by sol-gel method. The physical properties, such as thermal stability, crystallite size and crystallinity according to synthesis condition have been investigated by TEM, XRD, SEM, TGA and DTA. In addition, Zinc phosphating has been studied in order to compare the phosphating characterization of prepared nanosized titanium-colloid particles. The major phase of all the prepared titanium-colloid particles was an amorphous structure regardless of synthesis temperature and the structure was composed of phoshate complex and titanium. The micrographs of HR- TEM showed that nanosized titanium-colloid particles possessed a spherical morphology with a narrow size distribution. The crystallite size of the titanium-colloid particles synthesized at 80℃ was 4-5 nm and increased to 8-10 nm with an increase of synthesis temperature (150℃). In addition, the coating weight increased with an increase of temperature of phosphating solution and when the concentration of titanium-colloid was 2.0 g/l, the coating weight was 1.0 g/㎡.

• Journal of Welding and Joining
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• v.25 no.3
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• pp.37-44
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• 2007

Mechanical and thermomechanical properties of the bulk metallic glass (BMG) are so unique that the deformation behavior is largely dependent on the temperature and the strain rate. Impacting behavior of NiTiZrSiSn bulk metallic glass powder during kinetic spraying was investigated in this study. Considering the impact behavior of the BMG, the kinetic spraying system was modified and attached the powder preheating system to make the transition from the inhomogeneous deformation to the homogeneous deformation of impacting BMG particle easy BMG splat formation is considered from the viewpoint of the adiabatic shear instability. It is suggested that the impact behavior of bulk metallic glass particle is determined by the competition between fracture and deformation. The bonding of the impacting NiTiZrSiSn bulk amorphous particle was primarily caused by the temperature-dependent deformation and fracture (local liquid formation) behavior.

• Textile Coloration and Finishing
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• v.20 no.1
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• pp.1-7
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• 2008

The study has attempted to introduce a new coating than the conventional standardized method of spray, padding and roll coating. The study has focused on finding condition for separating water and organic layer in marble bath and surface effects according to kind of raw hide. It was found that dyestuff-free was to be used in water layer and the input amount of initial insoluble pigment to be added in marble bath should be adjusted following the change of surface area of the marble bath in order to get efficient marble effect while preventing coagulation of water and organic layers. Eventually, amorphous high value-added leather could be obtained treated in process other than the conventional standardized method. Even raw hides of low grades($C{\sim}E$ grades) could be processed into amorphous marble effect that could conceal or shield surface scratches by the colorant, which eventually eliminated necessity of using excessive amount of chemicals in the coating process leading to achieving high quality marble leather of natural look.

• Journal of the Korean Solar Energy Society
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• v.28 no.1
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• pp.33-42
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• 2008

Zr-O ($Zr-ZrO_2$) cermets solar selective coatings with a double cermets layer film structure were prepared using a DC (direct current) magnetron sputtering method. The typical film structure from surface to bottom substrate were an $Al_2O_3$ anti-reflection layer on a double Zr-O cermets layer on an Al metal infrared reflection layer. Optical properties of optimized Zr-O cermets solar selective coating had an absorptance of ${\alpha}\;=\;0.95$ and thermal omittance of ${\epsilon}\;=\;0.10\;(100^{\circ}C)$. The absorbing layer of Zr-O cermets coatings on glass and silicon substrate was identified as being amorphous by using XRD. AFM showed that ZF-O cermets layers were very smooth and their surface roughness were approximately $0.1{\sim}0.2 nm$. The chemical analysis of the cermets coatings were determined by using XPS. Chemical shift of photoelectron binding energy was occurred due to the change of Zr-O cermets coating structure deposited with increase in oxygen flow rate. The result of thermal stability test showed that the Zr-O cermets solar selective coating was stable for use at temperature below $350^{\circ}C$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.273-276
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• 2005

Packing characteristics of amorphous alloy particles were investigated by scanning electron microscopy, compositional analysis, micro-hardness test and finite element method (FEM). Electroless Ni-plating was made on the surface of the Cu-based amorphous particles before consolidation in ambient atmosphere at an intermediate region of glass transition and crystallization temperatures $(T_g\;and\;T_x)$. Some parts of the Ni-layer in the interfaces of the consolidated particles disappeared, while some of them still remained without appreciable change in compositions. No cracks or fractures were found in the particles, which may occur at low temperatures below or near $T_g$ as anticipated by the FEM analysis. Crystallization and change in hardness were not observed after consolidation.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.801-808
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• 2012

TiAlCN coatings with various C contents were synthesized by unbalanced magnetron sputtering. The characteristics, the crystalline structure, surface morphology, hardness, and friction coefficient of the coatings as a function of the C content were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), a microhardness tester, and a wear test. In addition, their corrosion behaviors in a deaerated 3.5 wt% NaCl solution at $40^{\circ}C$ were investigated by potentiodynamic polarization tests. The results indicated that the $Ti_{14.9}Al_{15.5}C_{30.7}N_{38.9}$ coating had the highest hardness, elastic modulus, and a plastic deformation resistance of 39 GPa, 359 GPa, and 0.55, respectively, and it also had the lowest friction coefficient of approximately 0.26. Comparative evaluation of the TiAlCN coatings indicated that a wide range of coating properties, especially coating hardness, could be obtained by the synthesis methods and processing variables. The microhardness of the coatings was much higher than that from previously reported coating using similar magnetron sputtering processes. It was almost as high as the microhardness measured from the TiAlCN coatings (~41 GPa) synthesized using an arc ion plating process. The potentiodynamic test showed that the corrosion resistance of the TiAlCN coatings was significantly better than the TiAlN coatings, and their corrosion current density ($i_{corr}$), corrosion potentials ($E_{corr}$) and corrosion rate decreased with an increasing C content in the coatings. The much denser microstructure of the coatings due to the increased amount of amorphous phase with increasing C contents in the coatings could result in the the improved corrosion resistance of the coatings.

• Tribology and Lubricants
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• v.34 no.6
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• pp.241-246
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• 2018

This research addresses the improvement of tribo-systems, specifically regarding the reduction of friction and wear through tribo-coupling between tetrahedral amorphous carbon (ta-C) with different types of counterpart materials, namely bearing steel (SUJ2), tungsten carbide (WC), stainless steel (SUS304), and alumina ($Al_2O_3$). A second variable in this project is the utilization of different values of duct bias voltage in the deposition of the ta-C coating - 0, 5, 10, 15, and 20 V. The results of this research are expected to determine the optimum duct bias and best counter materials associated with ta-C to produce the lowest friction and wear. Results obtained reveal that the tribo-couple between the ta-C coating and SUJ2 balls produces the lowest friction coefficient and wear rate. In terms of duct bias changes, deposition using 5 V produces the most optimum tribological behavior with lowest friction and wear on the tribo-system. In contrast, the tribo-couple between ta-C with a WC ball causes penetration through the coating surface layer and hence high surface delamination. This study demonstrates that the most effective ta-C coating duct bias is 5 V associated with SUJ2 counter material to produce the lowest friction and wear.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.1
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• pp.35-40
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• 2008

Ni-based amorphous alloy ribbon was prepared by a single-roller melt-spinning technique. Palladium coating was found to enhance significantly the absorption/desorption behavior of hydrogen in amorphous alloy. The hydrogen permeability of a Pd-coated $(Ni_{60}Nb_{40}){_{100-X}}$TaX(x=5, 10) amorphous alloy was examined in the temperature range of $623{\sim}773K$, comparable with those of $Pd_{60}-Cu_{40}$ alloys. The permeated hydrogen flux was increased with increasing the temperature and the difference of hydrogen pressure between the feed side and permeates side of the membrane. The Ni-based amorphous alloys were characterized by X-ray diffractometry(XRD) and differential scanning calorimetry(DSC). The morphology of surface and roughness was observed by using scanning electron microscopy(SEM) and atomic force microscopy(AFM).