• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.90-90
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• 2010

We investigated the modification of optical response properties of titanium dioxide (TiO2) coatings on the ceramic water-purification filters by using ultraviolet-visible absorption spectroscopy and X-ray diffraction. The TiO2 coatings were prepared on ceramic substrate by e-beam evaporation method. These amorphous TiO2 were turned into anatase phase by heat treatment at $700^{\circ}C$ for 2 hours. The doping of N atoms into the TiO2 coatings was done by using 70KeV of N＋ ion implantation with the dose of $1.0{\times}1017$ ions/cm2, followed by post-irradiation heat treatment at $550^{\circ}C$ for 2 hours. Methylene blue test of TiO2 coatings to solar irradiation showed that the post-evaporation heated TiO2 was photocatalytic and N-doped TiO2 reacted to the visible part of solar irradiation.

• Tribology and Lubricants
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• v.26 no.3
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• pp.157-161
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• 2010

This study investigated the effects of spray parameters on wear behavior of the Ni-based hard coatings fabricated by thermal spray process. The experiment was designed by an orthogonal array, the Ni-based hard coatings were fabricated according to this experimental design. The wear test was performed on these coatings using ball-on-disk wear tester. The ANOVA was used to analyze the effects of spray parameters on the wear rate of these coatings, as a result, oxygen gas flow and acetylene gas flow were determined as main factors effected on the wear rate. The effects of these two factors on wear behavior were observed by using SEM and EDX.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.186-189
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• 2005

This paper was designed to assess the adhesive properties of hard coatings on non-nitrided and nitrided various tool steels. Estimations of adhesion were done to scratch test which is mainly used in hard coating. The critical load(Lc) between coating and substrate is defined through analysis of frictional load vs. normal load curve, signals of acoustic emission and optical observations. Coatings employed in this study are TiN, CrN and TiAlN, tools as substrates are STD11, STD61 and SKH51. It was classified to substrates with/without nitrided layer and hard coatings on substrate were deposited by arc PVD. Results showed that harder substrates and coatings give higher values of critical loads.

• Journal of Surface Science and Engineering
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• v.48 no.4
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• pp.136-141
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• 2015

The paper presents the comparative results of NbN coatings deposited by DC and pulsed DC asymmetric bipolar magnetron sputtering systems. The results show that, with the decreasing duty cycle and increasing pulse frequency, the coating morphology changes from a columnar to a dense structure, with finer grains. The Pulsed sputtered NbN coatings showed higher hardness, higher residual stress, and smaller grain sizes than those of DC prepared NbN coatings. Moreover residual stress of pulsed sputtered NbN coatings increased on increasing pulse frequency. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 50 kHz.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.340-344
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• 1998

Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2$-8wt.% $Y_2O_3$ ceramic coating during cyclic oxidation. $Al_2O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_2O_4$ and $Ni(Al, Cr)_2O_4$ during cyclic oxidation. It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr, Al)_2O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

• Journal of Welding and Joining
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• v.12 no.1
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• pp.94-101
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• 1994

In this study, plasma spraying has been used to produce $TiO_2$ polycrystalline coatings from $TiO_2$ powders. The physical and chemical properties of plasma sprayed $TiO_2$ coatings depend greatly on plasma spraying conditions. The electrical resistivity, oxygen concentration, photocurrent and crystal structure of plasma sprayed $TiO_2$ coating has been studied. The results are as follows: 1. The oxygen loss and electrical conductivity of $TiO_2$ plasma sprayed coatings increased by low pressure and high amount of auxiliary gas, hydrogen in plasma spraying. 2. Oxygen loss increase electrical conductivity, and decrease photocurrent of $TiO_2$ plasma sprayed coatings. 3. Photocurrent of $TiO_2$ plasma sprayed coatings manufactured in atmospheric pressure is higher than that of low pressure.

• Journal of the Korean Applied Science and Technology
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• v.12 no.1
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• pp.19-27
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• 1995

The 2-packaged polyurethane coatings were synthesized, blending pheylmodified polyesters(of which synthetic methods were reported in the previous paper), Desmodur L-75(polyisocyanate wide1y used for coatings), wetting-dispersing agent, white pigment. etc. A variety of coating properties were tested for the coating treatment polyurethane coationgs. Compared with conventional 2-packaged polyure-thane coating, abrasion resistance and lightness index difference of the ones synthesized in the present work were somewhat decreased, but the coating properties such as hardness, gloss specular, cross hatch adhesion. etc. were improved. Especially, resistance against chemical reagents and salt were strikingly improved. In addition. the coationgs had short drying time and long pot-life. This shows that the coationgs are appropriate for rapid drying coatings.

• Journal of Surface Science and Engineering
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• v.20 no.3
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• pp.95-105
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• 1987

For the purpose of improving the hot corrosion resistance of Ni-base superalloy, Inconel 600, aluminide and chromium-aluminide coatings by pack cementation process were studied. The morphology of these coatings is dependent on the type of process employed. And their overall composition depends on the composition of the base alloy and on the nature of the cement. Therefore the different aluminide and chromium-aluminide coatings obtained on a superalloy do not possess the same resistance to oxidation and hot corrosion. The mechanisms governing the formation of the coatings and the composition of the coating were varied by pack composition and temperature, and cyclic hot corrosion resistance of the auluminide coating formed by one-step process was inferior to that of the coating formed by two-step process. and Cr-Al composite coating showed good resistance for cyclic hot corrosion.

• Journal of Surface Science and Engineering
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• v.21 no.2
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• pp.39-46
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• 1988

Corrosion behavior of 5-26wt% Ni-Zn electrodeposited alloys was investigated by means of dipping electrochmical polarization measurement and galvanic coupling test. The weight loss and anodic polarization curve of coatings were measured by means of dipping and polarization measurement respectively. The galvanic protection effect of alloy coatings was measured by galvanic coupling test and the surface morpholgy of coatings was observed after corrosion testing. Our findings support thous of previous investigations showing that ${\gamma}$single phase coatings, while galvanic pprotection effect of dual phase coatings improved in comparison with ${\gamma}$single phase coating. The formation of colony in coating of ${\gamma}$and η+${\gamma}$ dual phsae caused the localized corrsion and increased the corrosion rate of the Ni-Zn coating.

• Journal of Surface Science and Engineering
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• v.43 no.4
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• pp.165-169
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• 2010

$Ni-Al_2O_3$ nanocomposite coatings were fabricated by conventional electrodeposition technique using nickel sulfamate bath. Effect of plating parameters on electrodeposition of $Ni-Al_2O_3$ nanocomposite were studied. The properties of the nano composite were investigated by using SEM, XRD, and Vicker's microhardness test. The results demonstrated that $Al_2O_3$ incorporation in the composite coatings was found to be increased by increasing stir rate and $Al_2O_3$ content in plating bath. Microhardness of the composite coatings was also increased with increasing content of the nano particles in the plating bath. The surface morphologies of the nanocomposite coatings were found to be varied with varying pH, current densities as well as alumina content in the plating bath.