• 한국세라믹학회지
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• 제53권6호
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• pp.628-634
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• 2016

The 8 wt% yttria($Y_2O_3$) stabilized zirconia ($ZrO_2$), 8YSZ, a typical thermal barrier coating (TBC) for turbine systems, was fabricated under different starting powder conditions and coating parameters by atmospheric plasma spray (APS) coating process. Four different starting powders were prepared by conventional spray dry method with different additive and process parameter conditions. As a result, large- and small-size spherical-type particles and Donut-type particles were obtained. Dense structure of 8YSZ coating was produced when small size spherical-type or Donut-type particles were used. On the other hand, 8YSZ coating with a porous structure was formed from large-size spherical-type particles. Furthermore, a segmented coating structure with vertical cracks was observed after post heat treatment on the surface of dense structured coating by argon plasma flame at an appropriate gun distance and power condition.

• 펄프종이기술
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• 제39권3호
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• pp.41-51
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• 2007

In order to elucidate the effects of types and mixing ratio of GCC and clay, coating color concentration, and types of rheology modifiers on high solid coating, various coating colors were prepared, high shear viscosity was measured and then rheology of the coating colors was analyzed. Coating color concentration was able to be increased from 67% to 69% and from 68% to 71% with a higher GCC ratio and with the rheology modifier instead of the synthetic thickener, keeping similar or improved coating color rheology and coated paper quality. The rheological properties of high solid coating color were superior with smaller average particle sizes of clay and latex, wider size distribution of GCC and higher added amount of latex.

• 펄프종이기술
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• 제44권3호
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• pp.1-8
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• 2012

The effects of several factors including organic pigment blending and calending conditions on the surface and optical properties of coated paper were investigated. When clay and calcium carbonate are blended in the ratio of 7 to 3, highest smoothness and relative sediment volume were obtained. When organic pigments were added to the mixture of clay and calcium carbonate, the relative sediment volume did not changed significantly. However, when organic pigments were added to calcium carbonate, sheet gloss and smoothness were improved, and showed the better results than that obtained from the mixture of organic pigment and clay. When organic pigment is blended with clay, the particles of organic pigment are buried in the packing structure of coating layer. However, the particle shape of calcium carbonate is quite different from that of clay, and the aspect ratio of calcium carbonate is similar to that of organic pigment. Thus organic pigment particles are not buried and improved effectively the physical characteristics of coating layer. When the hollow sphere pigment was blended, opacity and sheet gloss were improved significantly. Even though the coating color applied was reduced, the similar level of opacity was maintained. Also, if particle size and void volume are increased, gloss is improved, because coating layer is easily transformed in calendering. Therefore, even though lower pressure was applied during calendering, the smoothness of surface of coating layer was improved, and the decrease of void volume in coating layer was reduced, and the quality of coated sheet can be improved.

• 한국재료학회지
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• 제28권7호
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• pp.423-427
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• 2018

For diamond/metal composites it is better to use diamond particles coated with metal carbide because of improved wettability between the diamond particles and the matrix. In this study, the coating of diamond particles with a chromium carbide layer is investigated. On heating diamond and chromium powders at $800{\sim}900^{\circ}C$ in molten salts of LiCl, KCl, $CaCl_2$, the diamond particles are coated with $Cr_7C_3$. The surfaces of the diamond powders are analyzed using X-ray diffraction and scanning electron microscopy. The average thickness of the $Cr_7C_3$ coating layers is calculated from the result of the particle size analysis. By using the molten salt method, the $Cr_7C_3$ coating layer is uniformly formed on the diamond particles at a relatively low temperature at which the graphitization of the diamond particles is avoided. Treatment temperatures are lower than those in the previously proposed methods. The coated layer is thickened with an increase in heating temperature up to $900^{\circ}C$. The coating reaction of the diamond particles with chromium carbide is much more rapid in $LiCl-KCl-CaCl_2$ molten salts than with the molten salts of $KCl-CaCl_2$.

• 대한금속재료학회지
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• 제49권3호
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• pp.221-230
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• 2011

The cold spray process is an emerging technology that utilizes high velocity metallic particles for surface coating. Metallic powder particles are injected into a converging-diverging de Laval nozzle and accelerated to a high velocity by a supersonic gas flow. The cold spray process normally uses a circular nozzle that has a rather narrow spraying range. To overcome this fault, a slit nozzle was considered in this study. The slit nozzle is anticipated to reduce the coating process time because it has a wider coating width than the circular nozzle. However, the slit nozzle can reduce the coating efficiency because it does not allow as much gas and particle velocity as the circular nozzle. To improve the coating efficiency of a slit nozzle, the shape of the slit nozzle was modified. And the results of gas flow and particle behaviour according to the nozzlers shape were compared by the a numerical analysis. As a results, as Expansion Ratio(ER) of 7.5 was found to be the most optimal condition for enhancing the spraying efficiency when the ER was changed by the variation of nozzle neck and exit size.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.339-339
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• 2007

Metal coating on ceramic powder has long been attracting interest for various applications such as superconductor where the brittle nature of high temperature ceramic superconductor was complemented by silver coating and metalloceramics where mechanical property improvement was achieved via electroless plating. More recently it has become of great interest in embedded passive device applications since metal coating on ceramic particles may result in the enhancement of the dielectric properties of ceramic-polymer composite capacitors. In our study, nickel ion-containing solution was used for coating commercial capacitor-grade $BaTiO_3$ powder. After filtering process, the powder was dried and heat-treated in 5% forming gas at $900^{\circ}C$. XRD and TEM were utilized for the observation of crystallization behavior and morphology of the particles. It was found that the nickel coating characteristics were strongly dependent on the several parameters and processing variables, such as starting $BaTiO_3$ particle size, nickel source, solution chemistry, coating temperature and time. In this paper, the effects of these variables on the coating characteristics will be presented in some detail.

• 대한환경공학회지
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• 제27권7호
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• pp.697-703
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• 2005

본 연구에서는 주문진사 입경, 일차 및 이차 코팅온도, 코팅시간, 및 초기 3가철 주입농도를 변화시키면서 철을 코팅시킨 모래흡착제(Iron-Coated Sand, ICS)를 제조하였다. ICS 제조의 최적조건은 코팅효율, 코팅된 철의 안정성, 및 비소제거능 으로부터 선정하였다. 철코팅 효율은 입경이 작은 모래를 지지체로 사용하고 일차코팅온도를 높여주었을 때 뚜렷이 향상되었다. 철의 코팅효율은 이차코팅온도 및 코팅시간에는 크게 영향을 받지 않았지만 As(V) 흡착능은 이차코팅온도가 증가됨에 따라 크게 감소하는 것으로 나타났다. 이러한 결과들을 고려하여 ICS의 최적 이차코팅 조건을 $150^{\circ}C$ 온도조건과 1시간의 가열시간으로 선정하였다. Fe(III) 주입농도 변화에 따른 철 코팅효율은 0.8 Fe(III) mol/kg sand 될 때 까지는 뚜렷이 증가하였지만 그 이상에서는 큰 차이가 없었다. 기리고 Fe(III) 주입농도를 증가시킬수록 As(V) 흡착능도 증가하였으며 0.8 Fe(III) mol/kg sand 조건에서 최대값을 보여주었다. 이차 코팅온도 및 시간은 ICS 안정성의 주요변수로서 코팅온도를 높이고 코팅시간을 길게 할수록 ICS로 부터 용출되는 철의 양은 감소하였다. ICS에 대한 As(V)의 흡착은 낮은 pH에서 흡착량이 증가하는 전형적인 음이온형 흡착경향을 보여서 ICS는 강한 산성을 띄는 오염수내에 함유된 As(V)를 제거하는데 적용이 가능함을 알 수 있었다.

• 한국분무공학회지
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• 제16권1호
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• pp.37-43
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• 2011

The present study conducted computational simulation for multiphase flow in the flame spray coating process with commercially available Ni-Cr powders. The flows in a flame spray gun is characterized by very complex phenomena including combustion, turbulent flows, and convective and radiative heat transfer. In this study, we used a commercial computational fluid dynamics (CFD) code of Fluent (ver. 6.3.26) to predict gas dynamics involving combustion, gas and particle temperature distributions, and multi-dimensional particle trajectories with the use of the discrete phase model (DPM). We also examined the effect of particle size on the flame spray process. It was found that particle velocity and gas temperature decreased rapidly in the radial direction, and they were substantially affected by the particle size.

• Journal of Welding and Joining
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• 제5권2호
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• pp.17-26
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• 1987

In this study, the experiments were carried out for the purpose of establishment of the arc sparing method which reducing oxides or oxide film by using the inert gas as the carrier gas of atomizing particles. Main results obtained are as follows; 1. Oxides and oxide film which lower the adhesion strength are largely reduced by using the inert gas as the carrier gas of atomizing particles, and adhesion strength of coating film are improved. 2. The coating film characteristics appear to be no difference between the inert gas arc spraying in air environment and that in argon gas environment. 3. Inert gas arc spraying using argon as the carrie gas has higher reduction rate of composition element in coating film than compressed air spraying does.

• 한국식품저장유통학회지
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• 제8권2호
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• pp.181-186
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• 2001

The objective of this study is to determine the effect of soy protein isolate (SPI) film coating on the color, firmness, viscosity and weight loss of Rice Cake stored at 15, 20 and $25^{\circ}C$ (RH 50%) for 30 days. Raw materials mixed with SPI and cocoa powder (10:0, 7:3, 5:5, 3:7, w/w) were prepared. After adding sugar and shortening to raw materials, the mixture were refined to 25 micron of particle size. Coating of Rice Cake were carried out at $65^{\circ}C$. SPI coated Rice Cake had higher internal and external firmness comparing to the control at $25^{\circ}C$. SPI coated Rice Cake showed smooth surface morphology and had 0.71-1.01 mm of thickness. SPI coated Rice Cake showed less weight loss for 30 days compared to controls. SPI coating solution was successfully coated on Rice Cake and extended shelf-life over 15 days at room temperature.