Onderzoek naar de interfase tussen ijs en vaste substraten: naar een efficiënt ontwerp van PFAS-vrije ijsafstotende coatings

This doctoral dissertation provides an in-depth examination of the fundamental mechanisms governing interfacial interactions between ice and solid surfaces, with particular focus on surface wetting, roughness, and ice adhesion strength. The ultimate goal is to exploit the acquired knowledge to enhance the design of icephobic surfaces. The research bridges critical gaps in understanding surface wetting behavior, surface topography, and interfacial interactions as vital factors that influence how water and ice interact with and detach from surfaces. The thesis opens with a thorough review of existing theories and experimental studies that attempt to correlate wetting characteristics with ice adhesion strength. It highlights inconsistencies and irreproducible findings in many reported correlations, mainly arising from oversimplified interpretations of wetting phenomena and a limited grasp of the ice-substrate interface. Acknowledging these shortcomings, the research reassesses these relationships using a wide range of experimental and analytical methods. A substantial dataset was generated, covering a variety of surface chemistries and roughness levels, to evaluate the effectiveness of commonly used wetting metrics as predictors of ice adhesion strength. The findings indicate that conventional wetting measures often fall short in capturing the intricate dynamics critical to ice adhesion and detachment. In contrast, more advanced wetting parameters derived from droplet sliding on tilted surfaces offer more meaningful insights, as they closely represent the shear-driven mechanisms governing shear-dominated ice detachment. Complementary studies utilizing various ice adhesion testing systems revealed that merely measuring adhesion strength is insufficient to assess the performance of icephobic coatings. By analyzing complete force-time curves from ice adhesion tests, the thesis provides a deeper understanding of stress buildup, detachment mechanisms, and coating durability, as well as an interpretation of icephobicity behavior. The interface of ice and solid substrates plays a critical role in the observed ice-repellency behavior. However, this interfacial region has always been obscured due to technical limitations in visualizing it. To tackle the longstanding challenge of effectively visualizing the hidden interface between ice and solid surfaces, an advanced visualization technique based on freezing X-ray computed tomography (XCT) was employed. This innovative approach enabled non-destructive, three-dimensional imaging of the ice-solid interface at micrometer-scale resolution, uncovering how internal and interfacial ice pores, solid surface textures, roughness, and wetting regimes contribute to ice-surface interactions. For the first time, XCT provided direct non-destructive visualization of mechanical interlocking between ice and textured surfaces, supporting many hypotheses that had previously relied on indirect or destructive methods for validation. In conclusion, this thesis sets forth a new framework for understanding and evaluating icephobicity by integrating surface science, mechanical testing, and advanced 3D visualization techniques. It illustrates that ice adhesion is a complex, multi-scale phenomenon influenced not only by surface wetting, chemistry, and roughness but also by the dynamic interplay of interfacial interactions and the mechanical response of surfaces. The insights from this work laid the foundation for the rational design of next-generation icephobic coatings for hybrid and active ice protection systems that are not only more effective but also sustainable (completely PFAS-free) and durable, promoting safer, more energy-efficient operations across sectors, including refrigeration systems and energy infrastructure.