Analisi delle proprietà superficiali nella progettazione di coating anti ghiaccio per applicazioni in campo aeronautico

The thesis is structured into three main parts. The first part, comprising Chapters 2–4, addresses a critical gap in the characterization of icephobic surfaces. During the first two years of the PhD, a custom experimental setup, the ICE-CUBE, was designed and constructed, and dedicated protocols for the investigation of early-stage icing were established. The primary objective was to propose a minimal and comparative testing framework under idealized conditions (low humidity) and to assess the validity of the wettability-based paradigm for achieving icephobicity in aeronautical applications. The proposed protocol includes the freezing probability, dynamic contact angles, as key metrics for evaluating early-stage icing phenomena, while ice adhesion measurements specifically quantify icephobic performance once ice has formed. Long-term coating durability is assessed through repeated frosting/defrosting cycles. The relevance of these laboratory-scale tests to realistic operational scenarios is evaluated through an ice wind tunnel (IWT) campaign, highlighting the necessity of including such tests in icephobic surface characterization protocols for aeronautical use. The second part of the thesis, presented in Chapter 5, moves beyond the classical wettability paradigm and explores the role of the quasi-liquid layer (QLL) in reducing ice adhesion. This research was conducted in collaboration with the Polymer and Functional Interfaces group during a research stay at the Danmarks Tekniske Universitet (DTU). Although first proposed by Faraday, the existence of QLL has gained widespread acceptance only in recent decades. The QLL consists of an interfacial liquid-like water layer that persists under subcooled conditions and may represent an alternative to lubricant-based strategies, such as liquid-infused surfaces. A series of homologous polyelectrolyte coatings—cationic methacrylate-based systems with identical crosslinking ratios—was investigated using the characterization protocol developed in the earlier chapters. These coatings exhibited ice nucleation delays comparable to those of tested hydrophobic reference surfaces. However, ice adhesion values exceeded the commonly accepted threshold of 100 kPa that define an icephobic surface, likely due to non-optimized surface chemistry, thereby identifying clear opportunities for further research into QLL-based icephobic materials. iii The third part of the thesis, described in Chapter 6, focuses on coating fabrication from a material perspective. A systematic investigation is presented on the influence of the modified silica coating solution formulation, including solvent selection and the concentration of low-surface-energy moieties, as well as processing parameters such as ambient humidity, withdrawal speed during dip-coating, and post-deposition annealing temperature. An application to dropwise condensation is also discussed. Furthermore, the chapter addresses the transferability of the optimized sol–gel coating, demonstrating successful deposition on substrates beyond silicon, including glass and aluminum. Scalability considerations are explored through a proof-of-concept spray deposition process, illustrating the potential extension of sol–gel coatings to rough and application-relevant surfaces, beyond the thickness limitations of conventional dip-coating techniques.