• Korean Chemical Engineering Research
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• v.49 no.3
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• pp.277-284
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• 2011

In this study, UV-curing type organic - inorganic hybrid hard coating solutions were prepared from alumina sols and acrylate monomers. The mixture of alumina sols, prepared from aluminum isopropoxide, and a silane coupling agent, methacryloxypropyl trimethoxysilane(MPTMS), was used as an inorganic component. Also, the mixture of acrylate monomers, pentaerythritol triacrylate(PETA), 1,6-hexanediol diacrylate(HDDA) and dipentaerythritol hexaacrylate (DPEHA), was used as an organic component. The organic-inorganic hybrid coating solutions were obtained by mixing the inorganic component and organic component, deposited on polycarbonate substrates by spin coating and densified by UV-curing. The effect of the amount of MPTMS in the inorganic component and the irradiation time during UV-curing was studied on the properties of coating films. As a result, when 0.20 mole of MPTMS was used, the pencil hardness of coated films showed an excellent pencil hardness of 3H and also exhibited a good abrasion resistance of 2% in haze.

• Proceedings of the KWS Conference
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• 1994.10a
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• pp.189-190
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• 1994

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1344-1347
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• 2004

Recently, Study on measuring property of a micro thin film(nm ～ hundreds of ) under Thermal Mechanical loading. In this work, We perform tensile test at high temperature(1200 ) to investigate mechanical properties of alumina TGO formed under Thermal Barrier Coating. We used Digital Image Correlation method for measuring displacement, and We presented a method of tensile test for thin film at high temperature.

• Journal of the Korean Ceramic Society
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• v.29 no.6
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• pp.496-504
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• 1992

Alumina tubes suitable for the support of gas separation membranes have been prepared by the slipcasting technique. These supports have the average pore size of 0.1 ${\mu}{\textrm}{m}$ within the narrow distribution. The sol-gel dipcoating process of nanoparticulate sols is very sensitive to microstructure of the support, and the coating on the inside surface of the tube is found to be more successful than on the outside surface. Nanoparticulate silica sols (0.82 mol/ι) have been synthesized by an interfacial hydrolysis reaction between TEOS and high alkaline water. When coating an alumina tube with these sols, the minimum limits of the particle size and the aging time required for forming the coated gel layer at the given pH are provided. It is optimum to coat the support with less concentrated sols stabilized through aging for the appropriate time (more than 22 days) at the lower pH (pH 2.0) for producing a reproducible crack free thin film coating in composite membranes.

• Journal of the Korean Ceramic Society
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• v.31 no.8
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• pp.911-919
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• 1994

As the study for preparation of single-layer anti-reflective coating on glass, the conditions of synthesis of sol for coating and of reproducible coating procedure were investigated. In case of water-based sol, coating was impossible because of poor wettability of sol. The Substitution of solvent with ethanol improved the wettability of sol on the glass surface, and optimum amount of ethanol for substitution was 70 vol%. Maximum specific surface area and total pore volume of water-based sol were 268.7$m^2$/g and 0.315 cc/g, but after substitution, those values increased to 404.1 $m^2$/g and 0.376 cc/g, respectively. The upper limit withdrawl speed of coating in order to get clean coated films without aggregations or stains was 7 cm/min. In case of addition of 0.1 mol HNO3 and substitution with 70 vol% ethanol and heat-treatment at 40$0^{\circ}C$ for 1 hour, thin film with thickness of 94 nm was obtained at withdrawl speed of 4 cm/min. The thickness of thin film was independent of drying time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.397-397
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• 2007

Diamondlike carbon (DLC) coatings were deposited on alumina ceramic seals using a plasma immersion ion deposition technique (PIID). Then they were subjected to tribological tests using a pin-on-disc tribometer under a high load (1.3 GPa) and under elevated temperatures up to 400C. Coefficients of friction (COFs) were recorded and compared with that of the untreated alumina while the wear tracks were analyzed using SEM with EDS to characterize the DLC films. To enhance the DLC adhesion to the substrate, various interlayers including Si and Cr were deposited using the PIID process or an ion beam assisted deposition (IBAD) method. It was observed that the DLC coating, if adhering well to the substrate, reduced the COFs significantly, from 0.4-0.8 for the uncoated alumina to about 0.05-0.1, within the tested temperature range. The adhesion was determined by the interlayer type and possibly by the application method. Cr interlayer did not perform as well as the Si interlayer. This could also be due to the fact that the Cr interlayer and the subsequent DLC coating had to be done in two different processing systems, while both the Si interlayer and the subsequent DLC film were deposited in one system without breaking the chamber. The coating failure mode was found to be delamination between the Cr and the alumina substrate. In contrast, the Si interlayer with proper DLC deposition procedures resulted in very good adhesion and hence excellent tribological performance. Further study may lead to future DLC applications of ceramic seals.

• The Korean Journal of Ceramics
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• v.7 no.2
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• pp.74-79
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• 2001

Alumina composite reinforced by chopped alumina fiber was fabricated by filter-pressing the fiber slurry followed by the infiltration of alumina slurry. The chopped fiber was coated with nickel by electroless plating method. The green samples were densified by hot-pressing. Microstructures were studied by SEM and the mechanical properties such as bending strength and fracture toughness were measured. The resulting mechanical properties were analyzed in relation with processing parameters such as preform density and resulting microstructures. The load-displacement curve of the specimen with Ni interlayer but without Ni inclusion showed brittle fracture mode due to the direct contact between matrix and fiber. The load-displacement curve of the specimen with Ni interlayer and Ni inclusion in the matrix which is introduced by high applied pressure during specimen preparation showed non-brittle fracture mode due to the fiber pull-out and dutile phases in the matrix.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.4
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• pp.297-302
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• 2009

We have successfully fabricated the alumina thick films using inkjet printing processes without a high temperature sintering process. Alumina suspension as dielectric ink was formulated by combining nano-sized alumina powders with an anionic polymer dispersant in formamide/water as co-solvent. The thickness of the printed alumina thick film was measured at around 5 um by field emission scanning electron microscope. The calculated packing density of 68.5 % from the printed alumina thick film was much higher than the same films fabricated by conventional casting or dip coating processes. Q factor of the dielectrics thick film infiltrated with cyanate ester resin was evaluated by impedance analyzer.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.909-914
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• 1995

From alumina powder and TEOS, $\alpha$-Al2O3/SiO2 composite powder for reaction-sintered mullite was synthesized by heterogeneous coagulation and surface coating, and investigated the mullitization reaction and sintering behavor of these powders. In $\alpha$-Al2O3/SiO2 composite powder prepared by heterogeneous coagulation, each alumina particles were surrounded by silica particles of 50~60 nm in size. And the alumina particles in composite powder prepared by surface coating were coated by uniform silica layer with thickness of 50 nm. In both methods, mullitization reaction was completed at 1$650^{\circ}C$ for 3h, and specimen sintered above 145$0^{\circ}C$ was about 95% fo the theoretical relative density. Mullite grains formed from the reaction with composite powders showed spherical shape with a size of 1~2${\mu}{\textrm}{m}$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.184-184
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• 2005