Design and Fabrication of Ice-phobic Surfaces
Open AccessDesign and Fabrication of Ice-phobic SurfacesGlobal warming has caused the shrinking of the Arctic ice cover, opening the Arctic Sea for passage of ships during August in 2012 [1]. This is referred to as the Northern Sea Route. The sailing months since has been extended to include other months. The Northern Sea Route connecting Atlantic Ocean to Pacific Ocean reduces the cargo shipping distance about 40% as compared to the sea route via Panama Canal [2]. However, it still faces many weather-related challenges such as frequent snow storms, freezing temperatures, and floating icebergs. Not all ships are equipped for such passage. In the Arctic Sea, cold temperatures, wind gusts, and splashes from the hull, combined to create continuous icing on shipboard, producing safety hazards such as frozen lifeboat latch, ice covered windows, and frozen communication gears. If icephobic surface can be developed to maintain functionalities under freezing conditions, even for a limited time, it will enhance safety. Designing and fabrication of such surfaces are therefore undertaken in this thesis. The objectives of this research are to explore the surface designs, develop fabrication techniques, and to measure their effectiveness in delaying the ice accretion. There are many papers in the literature reporting icing, ice nucleation, and ice crystallization. Most studies are conducted by climatologists studying the ice formation in upper atmospheres. Only recently, the effect of surfaces on icing are studied. It has been observed that heterogeneous ice nucleation can be significantly influenced by the presence of a surface [3]. The basic understanding of how surface roughness, energetics, and the nature of the materials influence icing are somewhat limited. There is no commonly accepted definition of icephobic surface, which just means that the surface resists icing when compared to the same surface without surface treatment. One of the notable characteristics of icephobic surfaces is most treatments or coatings reduce adhesion and make the ice removal easier. In the present study, the strategy of designing icephobic surface is based on high surface energetics by introducing multiscale roughness on the surface. This multiscale rough surface has been characterized in terms contact angles and measured surface roughness. The effectiveness of anti-icing is measured by icing delay time measured using a cryogenic differential scanning calorimeter (C-DSC). Contact angles and freezing time delay have been measured and compared to the baseline of no surface treatment. The freezing delay experiments were conducted at -20 ºC. Under this condition, water droplet on the baseline surface was observed to freeze after 3 minutes while water droplet on treated surfaces exhibit freezing delay up to several hours, which has not been reported in the literature. This result may be attributed to the ultra-hydrophobic surface and the surface topography created by the fabrication process. This is a first step towards potential application on ships to protect sensitive instruments while sailing through the Arctic Seas.
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Hacioglu_gwu_0075M_14864.pdf | 2019-08-18 | Open Access |
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