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Chemical treatment to improve usable strength of Ionexchanged cover glass
Hoikwan Lee,Byeongbeom Kim,Yuri Kim,Minki Kim,Seungho Kim,Seongtaek Lee 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.5
Glass leaching, including dissolution and hydrolysis, was introduced to mend surface flaws in ion-exchanged glass. Theleaching behavior on the glass surface was analyzed by using a spectrophotometer, AFM, a confocal LCM, a surface stressmeter and TEM. The results revealed that a silica-rich nano layer was formed on the surface of the glass after soaking in anacidic solution by dissolution of alkali ions from glass surface, and the formed layer including the flaws on the surface of theglass were completely removed after being exposed to an alkaline solution. We also found that leaching an aqueous solutionincreased the mechanical strength dramatically in ion-exchanged glass without degradation of surface quality.
Dielectric-breakdown and Conduction-mechanism in a Thinned Alkali-free Glass
Hoikwan Lee,Michael T. Lanagan 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.7
The leakage current in alkali-free glass was analyzed to understand the dielectric breakdownbehavior and the potential conduction mechanism. The dielectric breakdown strength and theleakage current were increased after the thickness of the glass had been recuded. To identifythe predominant conduction mechanism, we carefully interpreted the dc voltage-current curves viafitting with various conduction mechanisms, e.g.) Poole-Frenkel emission, Schottky emission, spacecharge-limited current, and hopping conduction. The result suggested that the space-charge-limitedcurrent and the hopping conduction of thermally-excited carriers were the most likely mechanismsof conduction in alkali-free glass.
Preparation and Characterization of Ultrathin Free-standing Carbon Films
Hoikwan Lee,Ramakrishnan Rajagopalan 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.10
Ultrathin free-standing carbon films with thicknesses of 8 - 14 nm were prepared by peelingfrom glass after pyrolization of the polyfurfuryl alcohol precursor at 700 C. The carbon films werecharacterized by using optical profilometry, confocal Raman spectroscopy, transmission electronmicroscopy, UV-vis spectroscopy, and a two-point probe I − V station measurement. The resultsconfirmed the formation of ultrathin free-standing carbon films with a polyaromatic domain structure. Those films had up to a 90% transmittance with respect to air and had an ohmic behavior. In this work, we also suggest that the most likely peeling mechanism of carbon films results fromglass corrosion.
Microwave Effect on Curing of Waterborne Polyurethane
Hoikwan Lee,Chris. Y. Fang,Carlo. G. Pantano,Wonho Kang 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.3
Spin-coated waterborne polyurethane to protect glass surface from environmental attacks was cured by using microwave heating. The effect of microwave heating on the reaction kinetics, chemical durability, and transmittance of polyurethane was investigated. In comparison to the conventional heating the results show that the microwave heating substantially accelerates the curing process of waterborne polyurethane and the total time for the completion of the reaction is only 1/7 of that in the conventional process. The microwave cured sample showed an excellent caustic resistance compared to conventional cured one. It means that microwave heating produces dense structure during curing process. The dense structure does not affect to the transmittance in the visible region.
Edge shape effect on the glass strength
Byunghoon Kang,Cheolmin Park,Seungho Kim,Seongtaek Lee,Hoikwan Lee 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2
In this study, the edge shape effect on the impact and bending strength of glass sheet was carefully investigated by using edgeimpact test (EIT) and 4-point bending (4PB) test. The Weibull data obtained from EIT showed that round shape was moreresistance to impact test regardless of the tilted stage angle and the strength values were in the order of round shape, bevelshape, and cut shape. When it comes to the bending strength, it was insensitive to the edge shape unlike the impact strength. Fracture analysis proved that the origins were located around the grinned surface and the breakage behavior of round shapewas different those of bevel and cut shape. The mirror strength was calculated by the means of measuring the mirror radius,and the relationship compared to the tensile stress was discussed in detail.