Authors
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Stöckelhuber, K.W. ; Schulze, H.J. ; Wenger, A.
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Title
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Metastable water films on hydrophobic silica surfaces
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Date
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31.12.2001
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Number
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9835
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Abstract
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The mechanism of the rupture process of liquid films is not fully understood yet, particularly in the case of an asymmetric film between a solid surface and a gas bubble. There are two theoretical approaches describing this problem:<br />- Growing fluctuation waves (spinodal dewetting) on fluid interfaces under the influence of any kind of attractive force [electrostatic, van der Waals, and maybe a so-called long-range hydrophobic force (LRHF)]. This mechanism was first developed by Scheludko.<br />- Nucleation inside the film first proposed by Derjaguin.<br />Metastable wetting films on glass surfaces either hydrophobized by methylation (negatively charged) or with Al3+ ions positively charged and hydrophilic, are analyzed by film thinning according to the Reynolds law.<br />These experiments demonstrate that<br />- Both mechanisms can be responsible for thin wetting film rupture: in the case of hydrophobic surfaces, the nucleation mechanism; in the case of oppositely charged silica surfaces, the capillary waves mechanism due to the attractive electrostatic double layer force between silica and the air bubble.<br />- The existence of a LRHF on a hydrophobic surface can be excluded. The apparent interaction can be explained by the presence of gas nuclei formed on heterogeneous sites.<br />The results provide deeper insight into the mechanisms of wetting film stability, the adhesion process in flotation and droplet coalescence.
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Publisher
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Progress in Colloid and Polymer Science
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Wikidata
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Citation
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Progress in Colloid and Polymer Science 118 (2001) 11-16
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DOI
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http://www.springerlink.com/link.asp?id=1lpqkujpq13036tu
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Tags
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