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RISS 인기검색어
- 검색키워드
- 저자 : W. Sigmund (검색결과 3 건)
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Biologically inspired hairy structures for superhydrophobicity
Hsu, S.H.,Woan, K.,Sigmund, W. Elsevier Sequoia 2011 Materials science & engineering. a review journal. Vol.72 No.10
Superhydrophobic surfaces have received tremendous attention in the last decade, owing to the number of emerging applications in conservation of environment. These surface properties are based on physio-chemical principles and can be transferred into technical ''biomimetic'' materials, as successfully done for the Lotus leaves. This article provides a review of the most recent development in superhydrophobic surfaces. Examples of superhydrophobic surfaces from nature are presented. It focuses on the hairy exterior of many different plant and animal species which renders them water repellent for protecting and maintaining crucial life functions. The classical Wenzel and Cassie-Baxter models along with manufacturing and understanding of the wettability of flexible hairy structures are reviewed.
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Adsorption studies on nano-zirconia in water and a water-1,2-propanediol mixture
C. Renger,P. Kuschel,A. Kristoffersson,B. Clauss,W. Oppermann,W. Sigmund 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.2
The adsorption of an electrosteric (polyacrylic acid, PAA), an electrostatic (triammonium citrate, TAC) and a steric dispersant (2-(2-(2 methoxy ethoxy) ethoxy)acetic acid, TODA) onto nanozirconia particles in deionized (d.i.) water and in a 75 wt% water-25 wt% 1,2-propanediol mixture was investigated. The amount of dispersant in d.i. water yielding the lowest apparent viscosity was measured via rheology. For PAA this was determined to be 6 wt%, for TAC 2 wt% (which corresponds to ≈ 0.43 mg/m2) and for TODA also 2 wt% (corresponding to ≈ 0.34 mg/m2). In the water-propanediol mixture the minimum viscosity was measured and the adsorbed amount was determined by adsorption isotherms using the depletion method. For TAC this was ≈ 0.076 mg/m2, which is five times less than the value in pure water. Furthermore, zeta-potential measurements were performed to confirm the dispersion mechanism. Zirconia particles in water showed the same zeta-potential as in waterpropanediol, although in water-propanediol less TAC molecules were adsorbed on the surface. For TODA the adsorbed amount was calculated to be ≈ 0.4 mg/m2, which fits well to the value determined in water. Propanediol seems not to influence the adsorption in that case.
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Seo, J.,Moon, J.,Bae, J.-Y.,Yoon, K.S.,Sigmund, W.,Paik, U. American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.6
The adhesion force between ceria and polyurethane (PU) pad was controlled to remove the step height from cell region to peripheral region during Shallow Trench Isolation Chemical Mechanical Planarization (STI-CMP) for NAND flash. Picolinic acid was found to be adsorbed on ceria particles at pH 4.5 following a Langmuir isotherm with the maximum adsorbed amount of 0.36 mg/m(2). The ceria suspension with full surface coverage of picolinic acid showed a threefold increase in the number of adhered ceria particles on the PU pad over non-coated ceria particles. It was shown that the coverage percent of picolinic acid on ceria corresponds well with the amount percent of adsorbed ceria on PU pad. The change in adsorbed particles was directly reflected in the CMP polishing process where significant improvements were achieved. Particularly, convex areas on the chip experienced higher friction force from the attached abrasives on the PU pad than concave areas. As a result, the convex areas have increased removal rate of step height compared to the ceria suspension without picolinic acid. The changing profiles of convex areas are reported during the step height reduction as a function of polishing time.
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