• Corrosion Science and Technology
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• v.5 no.2
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• pp.69-76
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• 2006

Premature cracking of the epoxy coatings applied on ship's ballast tanks(BT) can lead to damage of ship's hulls. To avoid this, it's important to have clear understanding of the underlying mechanism and primary factors of the coating crack. In this study, the efforts were made to clarify the integrated effects of main factors, i.e., initial coating shrinkage, thermally induced strain, steel-structural strain and the intrinsic coating flexibility at the initial and after aging, to the early cracking phenomena of epoxy coating in the ship's ballast tank. The coating crack is caused by combination of thermal stress, structural stress, and internal stresses which is closely related to chemical structures of the coatings. On the other hand, thermal stresses and dimensional stabilities would rarely play a major role in coating crack for ballast tank coatings with rather large flexibility. Crack resistance of the coatings at early stages can be estimated roughly by measuring internal stress, FT-IR and $T_g$ value of the coatings. A new screening test method was also proposed in this study, which can be possibly related to the long-term resistance of epoxy-based paints to cracking.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.109-115
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• 2022

The demand for metal 3D printing technology is increasing in various industries. The materials commonly used for metal 3D printing include aluminum alloys, titanium alloys, and stainless steel. In particular, for applications in the aviation and defense industry, aluminum alloy 3D printing parts are being produced. To improve the corrosion resistance in the 3D printed aluminum alloy outputs, a post-treatment process, such as chromate coating, should be applied. However, powdered materials, such as AlSi7Mg and AlSi10Mg, used for 3D printing, have a high silicon content; therefore, a suitable pretreatment is required for chromate coating. In the desmut step of the pretreatment process, the chromate coating can be formed only when a smut composed of silicon compounds or oxides is effectively removed. In this study, suitable desmut solutions for 3D printed AlSi7Mg and AlSi10Mg materials with high silicon contents were presented, and the chromate coating properties were studied accordingly. The smut removal effect was confirmed using an aqueous desmut solution composed of sulfuric, nitric, and hydrofluoric acids. Thus, a chromate coating was successfully formed. The surfaces of the aluminum alloys after desmut and chromate coating were analyzed using SEM and EDS.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.146-149
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• 2006

We developed new FED cathode film material that has catalysis function for graphite nano fiber. Using the cathode film with catalyst, we can simplify the FED process. It is composed of Cr, Fe-Ni catalyst. Fabricating FED panel with the film, we confirmed good emission performance of the panel.

• Textile Coloration and Finishing
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• v.27 no.1
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• pp.35-49
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• 2015

This paper investigated optimum process conditions of coating yarn for awning fabric. For this purpose, the simulation for processability and yarn quality using SPSS statistics package was carried out, and PP/TPO and PET/PVC coating yarns specimens were made with variation of extruder temperature and feed speed of core yarn on the yarn coating machine for examining simulation result. It was revealed that optimum coating conditions of PP/TPO 1000d coating yarn were extruder temperature $150^{\circ}C$, and core yarn feed speed 400~500m/min. Mechanical property and thermal shrinkage of PP/TPO coating yarn made at this conditions were best and core evenness rates of these coating yarns by yarn compression tester were also superior, which was certified by SEM photograph. In addition, these experimental results were coincided with simulation results. It was found that, in PET/PVC coating yarn, yarn physical properties between 1500d and 1200d coated yarns were not shown any difference, and core evenness rates of these coating yarns were superior. It revealed and concluded that these simulated coating conditions are applicable to production field.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.11-12
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• 2008

Micron-sized Co-alloy T800 powder was coated on Inconel718 (IN718) using high velocity oxygen fuel (HVOF) thermal spraying by the optimal coating process (OCP) determined from the best surface hardness of 16 coatings prepared by Taguchi program. The surface hardness improved 140-160 % from 399 Hv of IN718 to 560-630 Hv by the coating. Porosity of the coating was 1.0-2.7 %, strongly depending on spray parameters. Both friction coefficients (FC) and wear traces (WT) of the coating were smaller than those of IN718 substrate at both $25^{\circ}C$ and $538^{\circ}C$. FC and WT of IN718 and coating decreased with increasing the surface temperature. Tensile bond strength (TBS) and fracture location (FL) of Ti64/T800 were 8,770 psi and near middle of T800 coating respectively. TBS and FL of Ti64/NiCr/T800 were 8,740 psi and near middle of T800 coating respectively. This showed that cohesion of T800 coating was 8,740-8,770 psi, and adhesion of T800 on Ti64 and NiCr was stronger than the cohesion of T800.

• Journal of Surface Science and Engineering
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• v.54 no.5
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• pp.285-293
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• 2021

High-entropy TiAlCrSiN nano-composite coating was designed to improve mold life for high temperature liquid molding. Alloy design, powder fabrication and single alloying target fabrication for the high-entropy nano-composite coating were carried out. Using the single alloying target, an arc ion plating method was applied to prepare a TiAlCrSiN nano-composite coating had a 30 nm TiAlCrSiN layers are deposited layer by layer, and form about 4 ㎛-thickness of multi-layered coating. TiAlCrSiN nano-composite coating had a high hardness of about 39.9 GPa and a low coefficient of friction of less than about 0.47 in a dry environment. In addition, there was no change in the structure of the coating after the dissolution loss test in the molten metal at a temperature of about 1100 degrees.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.5 s.108
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• pp.53-61
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• 2004

[ $Poly(_{D}-ldactide)\;(_{D}-PLA)$ ] was synthesized to have low molecular weight for miscible blends with a high molecular $poly(_{L}-lactide)\;(_{L} -PLA)$. The blends were prepared by dissolving the two components of $_{L}-PLA\;and\;_{D}-PLA\;(w/w)$ in chloroform (l00/0, 90/10, 70/30, 50/50, 30/70, 0/100). The miscibility of these miscible blends was characterized by gel-permeation chromatography (GPC), differential scanning calorimetry (DSC), and the selective degradability by enzymes (proteinase K, subtilisin and $\alpha$-chymotrypsin). The coating efficiency of PLA blends onto paper was determined and the degrading activity cellulases by on these blends. The miscibility, coating efficiency and enzymatic degradability of these blends were decreased according to increasing of $_{D}-PLA$ blending part. Such results were attributed to the extent of coating application of PLA, with better miscibility (compatibility), coating efficiency and degradability due to a higher $_{L}-PLA$ content.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.56-62
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• 2015

Using an optical 3D scanning device to collect data from a diffused reflection surface is very difficult. To solve this problem, there are many applications including a spray-type developer and silicon molds. However, using a developer can cause chemical reactions between objects and particles of the developer and uneven surfaces on the object. To overcome these problems, we suggest an electrostatic powder coating method for even coating of particles onto surfaces for collecting 3D shape data. We have developed an automatic, electrostatic powder-coating machine and performed three different experiments to compare this system with a laser interferometer and a T-scan 3D scanner. As a result, we could ascertain the various characteristics of this new method, including good sensitivity for the various surface states of the bare surface, developer, and electrostatic powder coating. Finally, we verified the outstanding scanning performance and were able to demonstrate that this method achieves quality than traditional methods.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.6
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• pp.64-69
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• 1984

We found that the maximum efficiency of Al-MIS (p-Si) solar ceil was shown at 80$\AA$ thickness of Al-film which was deposited with slower velocity than 0.6$\AA$/sec. It was coated with ZnS and SiO for Anti-Reflecting. In single coating, ZnS and SiO film had maximum Isc at 570 and 690 A thickness, respectively. We confirmed that these results agreed well with the quarter coating condition; n1d1=λ/4. In double coating, we held the one layer with its optimum thickness in single coating and controlled the other layer. The maximum value of Isc in this case was almost the same with it in single coating but was maintained its value in so wide range of thickness. Keeping the relation; n1d1=n2d2 as another way, we made the total thickness of film thinner to 70-90% of the sum of each optimum thickness in single coating. In this case Isc was higher value than 20% of it in any other previous case and was retained so wide range of thickness.

• Journal of Surface Science and Engineering
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• v.57 no.1
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• pp.14-21
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• 2024

For this study, CrAlN multilayer coatings were deposited on SKD61 substrates using a multi-arc ion plating technique. The structural characteristics of the CrAlN multilayer coatings were evaluated using X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Additionally, the adhesion of the coatings was assessed through scratch testing, and the mechanical strength was evaluated using nanoindentation and tribometric tests for frictional properties. The results show that the CrAlN multilayer coatings possess a uniform and dense structure with excellent mechanical strength. Hardness measurements indicated that the CrAlN coatings have high hardness values, and both the coating adhesion and wear resistance were found to be improved compared to CrN. The addition of aluminum is anticipated to contribute to enhanced durability and wear resistance.