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Photo Oxidative Degradation of Perfluoropolyether Lubricant for Data Storage
강호종,이지혜,천상욱,Frank E. Talke 한국고분자학회 2011 Macromolecular Research Vol.19 No.6
The degradation mechanism of perfluoropolyethers (PFPE) under UV exposure was investigated. Chain scission was found to be in the methylene (fluorine) and the hydroxyl end chain rather than in the methylene oxide and ethylene oxide main chain where the catalytic Lewis acid degradation was started. This suggests that UV light creates low energy electrons, which initiate the formation of radicals resulting in the chain scission of PFPE. Chain scission was accelerated under an air environment by the oxidation through radical propagation in the methylene (fluorine) end. In addition, the effect of UV degradation on the physical properties of Z-DOL was determined. UV exposure caused the dramatic weight loss of Z-DOL even at low temperatures that were far below the evaporation temperature of Z-DOL. On the other hand, the thermal stability of UV degraded Z-DOL was enhanced by increasing the molecular weight due to the chain extension through reactions between the formed radicals.
L. Zhou,K. Kato,G. Vurens,F. E. Talke 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
Magnetron and Ion beam sputtering were used to texture the air-bearing surface of magnetic recording sliders. Flying height measurements and Laser-Doppler interferometry were used to compare the "flyability" of textured and un textured sliders. Lubricant redistribution on the disk surface caused by slider/disk interactions was investigated using scanning ellipsometry (Surface Reflectance Analyzer (SRA)). The results show that slider surface texture causes only small changes in the flying height of sliders but reduces slider in-plane and out-of-plane vibrations. Textured sliders were found to cause less lubricant depletion on the disk surface than untextured sliders.
Strongly Superhydrophobic Silicon Nanowires by Supercritical CO₂Drying
최철민,Yeoungchin Yoon,홍대훈,Karla S. Brammer,Kunbae Noh,오영,오승한,Frank E. Talke,Sungho Jin 대한금속·재료학회 2010 ELECTRONIC MATERIALS LETTERS Vol.6 No.2
This paper reports on the extremely superhydrophobic behavior of supercritical CO₂ processed silicon nanowires (SiNWs) with a contact angle in excess of ~177°. Vertically aligned silicon nanowires with 10 nm to 40nm diameter and 1 mm to 3 mm in length were obtained by electroless etching (EE) technique. The asfabricated SiNWs were superhydrophilic with no water droplet formation (zero contact angle), and were then completely transformed to an extreme superhydrophobic state when their nanoscale surface roughness is combined with trichlorosilane hydrophobic coating. The processed SiNW array was so hydrophobic that water droplets always bounced off the surface and did not allow contact angle measurements to be obtained unless the substrate was intentionally given a concave-curvature by vacuum suction. Utilization of a hydrophobically surface-treated micro-pipette syringe enabled the release of a water droplet onto this extremely superhydrophobic surface for contact angle measurement. To prevent severe nanowire agglomeration during the drying process of wet etched SiNWs, supercritical CO₂ drying was utilized, which process significantly improved the nano configuration and enhanced hydrophobicity.
( Chul Min Choi ),( Yeoung Chin Yoon ),( Dae Hoon Hong ),( Karla S. Brammer ),( Kun Bae Noh ),( Young Oh ),( Seung Han Oh ),( Frank E. Talke ),( Sung Ho Jin ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 재료마당 Vol.23 No.3
This paper reports on the extremely superhydrophobic behavior of supercritical CO2 processed silicon nanowires (SiNWs) with a contact angle in excess of ~177°. Vertically aligned silicon nanowires with 10 nm to 40 nm diameter and 1 mm to 3 mm in length were obtained by electroless etching (EE) technique. The as-fabricated SiNWs were superhydrophilic with no water droplet formation (zero contact angle), and were then completely transformed to an extreme superhydrophobic state when their nanoscale surface roughness is combined with trichlorosilane hydrophobic coating. The processed SiNW array was so hydrophobic that water droplets always bounced off the surface and did not allow contact angle measurements to be obtained unless the substrate was intentionally given a concave-curvature by vacuum suction. Utilization of a hydrophobically surface-treated micro-pipette syringe enabled the release of a water droplet onto this extremely superhydrophobic surface for contact angle measurement. To prevent severe nanowire agglomeration during the drying process of wet etched SiNWs, supercritical CO2 drying was utilized, which process significantly improved the nano configuration and enhanced hydrophobicity.