Rivestimenti antifouling per applicazioni marine

My work has focused on the design and fabrication of superhydrophobic coatings (SHS) and Slippery Liquid Porous Surfaces (SLIPS) for marine applications. The coatings were obtained by deposition of ceramic nanoparticles (Al2O3, SiO2-X) and chemical modification with low surface energy compounds (< 23mN/m). I designed the synthesis of SiO2 nanoparticles that are inherently superhydrophobic by sol-gel in isopropyl alcohol and ethyl alcohol, respectively with fluorinated and alkyl chains. I characterized nanoparticles in terms of size and Z potential using DLS and ELS technology. I designed the one-step synthesis of flower-like boehmite (Al2O3) in hydrothermal route, in an aqueous solution, evaluating the morphology as different reaction conditions. I explored two deposition techniques, dip coating and spray coating. After the deposition of nanoparticles, a heat treatment was necessary. Heat treatment has been optimized for some more sensitive materials such as steel and fiberglass. The proposed coatings involve the combination of a first inorganic layer alumina based, which after boiling water treatment has flower-like structure, and an organic layer is deposited with fluorinated or alkyl functionality. The second type of coating has a layer composed of silica nanoparticles intrinsically superhydrophobic. To obtain a SLIPS type surface it is necessary to infuse a lubricant inside the porosities. Fluorinated lubricating oils, alkanes with long alkyl chains and silicon oils were chosen. I characterized the coatings in terms of wettability properties (static contact angle WCA and dynamic contact angle CAH) with water. After I determined the surface morphology with FESEM observation, determining the particle size, coating homogeneity, and thickness. The superhydrophobic coatings were subjected to cell adhesion test (MTT cell viability assay) and cytotoxicity tests (Actin/DAPI), also evaluating the strength of the superhydrophobic properties after test. The antifouling properties of the coating was tested with larvae settlement test (no choice assay), and the leaching toxicity of the coatings molecules was evaluated. Finally, the coatings were to the open sea to assess the antifouling qualities under more drastic conditions. Moreover, the durability of the superhydrophobic properties in underwater conditions has been monitored. Coatings have been designed to reduce wall friction in underwater conditions. The tests were conducted on aluminum panels, suitably microstructured with hierarchical structured and functionalized with fluorine-free compounds. The reduction of wall friction was measured in the cavitational tunnel, evaluating the reduction of wall hydrodynamic force as the water flow speed increased. Hydrodynamic force tests are conducted on surface rotors of a suitably nanostructured and functionalized rheometer for the alternative evaluation of morphological potentials easily applicable in future perspective. The ultimate goal was to find a superhydrophobic coating that combined antifouling and friction reduction properties.