• Corrosion Science and Technology
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• v.23 no.2
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• pp.93-103
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• 2024

In the present work, a phase-field model for dendritic solidification is applied to hot-dip ZnAlMg coatings to elucidate the morphology of zinc dendrites and the solute segregation leading to the formation of eutectics. These aspects define the microstructure that conditions the corrosion resistance and the mechanical behaviour of the coating. Along with modelling phase transformation and solute diffusion, the implemented model is partially coupled with the tracking of crystal orientation in solid grains, thus allowing the effects of surface tension anisotropy to be considered in multi-dendrite simulations. For this purpose, the composition of a hot-dip ZnAlMg coating is assimilated to a dilute pseudo-binary system. 1D and 2D simulations of isothermal solidification are performed in a finite element solver by introducing nuclei as initial conditions. The results are qualitatively consistent with existing analytical solutions for growth velocity and concentration profiles, but the spatial domain of the simulations is limited by the required mesh refinement.

• Korean Journal of Materials Research
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• v.34 no.4
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• pp.215-222
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• 2024

Because collagen is inherently piezoelectric, research is being actively conducted to utilize it to harvest energy. In this study, a collagen solution was prepared using edible low-molecular-weight peptide collagen powder, and collagen films were fabricated using a dip coating method. The collagen films prepared by dip coating showed a smooth surface without defects such as pinholes or cracks. Dehydrothermal treatment of the collagen films was performed to induce a stable molecular structure through cross-linking. The collagen film subjected to dehydrothermal treatment at 110 ℃ for 24 h showed a thickness reduction rate of 19 %. Analysis of the collagen films showed that the crystallinity of the collagen film improved by about 7.9 % after dehydrothermal treatment. A collagen film-based piezoelectric nanogenerator showed output characteristics of approximately 13.7 V and 1.4 ㎂ in a pressure test of 120 N. The generator showed a maximum power density of about 2.91 mW/m² and an output voltage of about 8~19 V during various human body movements such as finger tapping. The collagen film-based piezoelectric generator showed improved output performance with improved crystallinity and piezoelectricity after dehydrothermal treatment.

• Journal of Powder Materials
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• v.21 no.1
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• pp.21-27
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• 2014

In this study, diatomite based materials were investigated as a support filter for silica particle coating. The silica sol for coating was synthesized by a st$\ddot{o}$ber process. The diatomite support was dry-pressed at 10 MPa and sintered at $1200^{\circ}C$ for 1 hour. The coating sol was prepared as a mixture of EtOH and silica sol. The diatomite support was coated by a dip-coating process. Silica coated diatomite filter was sintered at $1000{\sim}1200^{\circ}C$ for 1 hour. The largest pore size was decreased with increasing concentration ratio of coating sol. The gas and water permeability of silica coated diatomite decreased with increasing of concentration ratio of the coating sol.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.233-233
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• 2006

[ $Y_{2}O_{2}S:Eu$ ], a red phosphor, coated with silica nanoparticles or nanocomposites composed of silica nanoparticles and polymeric materials such as PMMA and PVP was prepared via sol-gel process. Samples were prepared from four different methods coded P1, P2, P3, and P4. P1 includes a conventional sol-gel process and a dip-coating method while P2 has the same procedure with P1 except that nanocomposites containing both silica nanoparticles and polymer prepared by sol-gel process were used as coating materials. In P3 method, phosphors were dispersed in a solution containing silica precursor, i.e., TEOS and then polymerization was performed to coat onto the phosphors surface while P4 followed the same procedure with P3 except that a solution containing both TEOS and organic monomer were used in preparing coating materials. Among various coating methods examined in this study, uniform coating of phosphor could be achieved by using method P4, i.e., phosphor surface coating in a solution containing hydrophobic monomer and TEOS. Furthermore, $Y_{2}O_{2}S:Eu$ red phosphor coated with nanocomposite composed of PMMA matrix and silica nanoparticles exhibited enhanced PL intensity and long-term stability.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.37-37
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• 2012

The coated steels, mainly with zinc by either hot-dip galvanizing or electroplating, are widely used for panels of automotive, electrical appliances and construction, whose size of world market have reached 130 million tons in 2008. Current issues for the coated steels can be integrated in terms of high functionality, low cost, environment-friend and available resource. The best solution can be provided if thin layer coating with higher quality is produced by an eco-friendly process, and PVD, physical vapor deposition, can be an alternative practice to existing coating processes. PVD technologies have been very common ones in electronic and semiconductor industries, but recognized as non-profitable processes for the coated steels due to low process speed and lack of continuous operation skills. Systematic researches from 1990s in Europe, even though discouraged by a shutdown of the first Japanese PVD coating plant in 1999, have realized several continuous PVD coating plants, and also enhanced launching of developments in steel industries. To be successful with PVD coating technologies over existing ones, productivity to meet economics should be created from a highly sophisticated process. Some PVD technologies fit for the high-speed process will be introduced together with experiences from industrial applications.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.244-254
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• 1999

폐윤활유 재생용 TiO2 한외여과막은 정밀영과용 지르코니아 복합막(즉, 복층담채) 및 알루미나 단층 담체(기공크기 0.1$mu extrm{m}$)상에 졸-겔 코팅법에 의하여 TiO2 분리막 층을 코팅하여 제조 하였다. TiO2 졸의 특성 분석을 통하여 봉입침지(sealed dip-coating) 및 가압 코팅(pressurized coating)법으로 결함이 없는 TiO2 복합막을 제조할 수 있는 코팅조건을 최적화 하였다. 합성 TiO2 한외여과막의 분리막층 두께는 1$\mu\textrm{m}$이하의 범위에서 조절되었으며,기공값을 보여주었으며 75$0^{\circ}C$까지 열처리하여도 80%정도의 용질배제율(기공크기 22.5nm)을 유지하는 점으로 봐서 고온 공정을 요하는 폐윤활유 재생막으로서 충분한 열적 안정성을 갖고 있었다.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.1
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• pp.85-92
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• 2003

A new type of catalytic filers has been developed in this work. A porous photocatalytic filter was prepared by coating the titania (anatase phase) powder onto the woven metal mesh. The coating sol was prepared with unique cera-mic binder, and would assist drying condition and enhance the mechanical strength of the final ceramic filers. As a result of the test for acetone decomposition, it was found to be quite effective for the photocatalytic reaction as good at conventional glass reactors which were coated inside. The present filter type reactor is expected as one of plausible devices for the simultaneous treatment of gas - particulate materials.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.79-85
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• 1997

In order to improve the surface characteristics of polymethylmethacrylate(PMMA), oxide thin film coatings were applied using the sol-gel dip-coating technique. The $Si(OC_2H_5)_4$, tetra-ethyl-ortho-silicate(TEOS) was used as a starting material for $SiO_2$ coating. The hardness of the alkoxy-derived oxide-coated PMMA was increased from 190 MPa for non-coated PMMA with increasing film thickness. By optimizing the heating conditions and the hydrolysis conditions, a maximum apparent hardness obtained In the present study was achieved 310 MPa using the withdrawal velocity of 5cm/min and heat treatment at $90^{\circ}C$ for 5 hours, which is about 1.6 times larger than that of uncoated PMMA.

• Journal of the Korean institute of surface engineering
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• v.34 no.2
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• pp.115-124
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• 2001

Gas wiping process of continuously hot-dip galvanized coating on steel strip has noise and coating problems. To improve the qualify of product, characteristics of air flow on the steel surface must be investigated. In this paper, fluid dynamic model of the gas flow is setup and solved numerically using STAR-CD. The effects of edge baffle, distance between steel plane edge and baffle, inlet pressure, and gap between air knife and strip steel surface are investigated, and it is concluded that edge baffle can reduce over-coating and edge built-up.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.831-838
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• 2011

Effects of spangle size and crystallographic characteristics on the surface appearance, galling properties, and adhesive strength of hot-dip galvanized steel sheets have been investigated. Both spangle size and crystallographic orientation measured by optical microscopy, scanning electron microscopy, and X-ray diffraction were identified as critical factors influencing the galvanized coating performance. By decreasing the spangle size, surface appearance and galling properties related to the friction coefficient were significantly improved. However, low temperature adhesive-strength with small spangle galvanized steel sheets showed lower values compared to commercially used galvanized coating. The variation of adhesive strength in terms of spangle size has been clarified.