Highly hydrophobic surfaces have been intensively investigated in the last years because their properties may lead to very promising technological spillovers encompassing both everyday use and high-tech fields. Focusing on textiles, hydrophobic fabrics are of major interest for applications ranging from clothes to architecture to environment protection and energy conversion. Gas diffusion media - made by a gas diffusion layer (GDL) and a microporous layer (MPL) - for fuel cells are a good benchmark to develop techniques aimed at characterizing the wetting performances of engineered textiles. An experimental investigation was carried out about carbon-based, PTFE-treated GDLs with and without MPLs. Two samples (woven and woven-non-woven) were analysed before and after coating with a MPL. Their three-dimensional structure was reconstructed and analysed by computer-aided X-ray microtomography (CT). Static and dynamic wettability analyses were then carried out using a modified axisymmetric drop shape analysis technique. All the surfaces exhibited very high hydrophobicity, three of them near to a super-hydrophobic behavior. Water drop impacts were performed, evidencing different bouncing, sticking and fragmentation outcomes for which critical values of the Weber number were identified. Finally, a CT scan of a drop on a GDL was performed, confirming the Cassie-Baxter wetting state on such surface.
Characterization of highly hydrophobic textiles by means of X-ray microtomography, wettability analysis and drop impact
Guilizzoni, M.;
2017-01-01
Abstract
Highly hydrophobic surfaces have been intensively investigated in the last years because their properties may lead to very promising technological spillovers encompassing both everyday use and high-tech fields. Focusing on textiles, hydrophobic fabrics are of major interest for applications ranging from clothes to architecture to environment protection and energy conversion. Gas diffusion media - made by a gas diffusion layer (GDL) and a microporous layer (MPL) - for fuel cells are a good benchmark to develop techniques aimed at characterizing the wetting performances of engineered textiles. An experimental investigation was carried out about carbon-based, PTFE-treated GDLs with and without MPLs. Two samples (woven and woven-non-woven) were analysed before and after coating with a MPL. Their three-dimensional structure was reconstructed and analysed by computer-aided X-ray microtomography (CT). Static and dynamic wettability analyses were then carried out using a modified axisymmetric drop shape analysis technique. All the surfaces exhibited very high hydrophobicity, three of them near to a super-hydrophobic behavior. Water drop impacts were performed, evidencing different bouncing, sticking and fragmentation outcomes for which critical values of the Weber number were identified. Finally, a CT scan of a drop on a GDL was performed, confirming the Cassie-Baxter wetting state on such surface.File | Dimensione | Formato | |
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