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• Six supercoolers with icephobic coatings were tested for ice slurry generators. • Three different chemical families were assessed at different mass flow rates. • Coated supercoolers achieve average supercooling degrees in the range of 3 K to 4 K. • Best icephobic coatings increase the supercooling degree by 30 % to 40 %. A supercooler is a heat exchanger that allows to supercool water avoiding ice nucleation on the heat exchanger surface. In this paper, six supercoolers with icephobic coatings were tested for supercooling ice slurry generators. As reference, a supercooler without any coating was used. For coating comparison, three different chemical families were tested at different mass flow rates. Experiments of coated heat exchangers show average supercooling degrees in the range of 3K to 4K. All icephobic coatings improved the supercooling degree respect to the reference non coated case by 7% to 44% at 1000 kg h − 1 mass flow rate with supercooling powers up to 5 kW. For a mass flow rate of 2000 kg h − 1 a supercooling power of about 6kW has been reached for five coatings at a temperature of − 2.5 ∘ C and hold constant for a time span of 3h. Some coatings could reach lower temperatures at this mass flow, but the experimental setup was limited to this supercooling power. The two coatings performing best in the heat exchanger tests were both from the family class hybrid organic-inorganic silane sol-gel with improvements in the degree of supercooling respect to the reference uncoated heat exchanger of 30% to 40%. The supercooling degrees achieved in the present work are up to two times larger compared to results published in scientific journals until this date using industrially relevant heat exchangers. [ABSTRACT FROM AUTHOR]

Nature inspires the artificial morphology regulation of surface structures that is highly preferred for applications such as wettability tuning. In comparison to smart responsive surfaces determined by the progress in material science, microfluidics has provided a material-independent pathway toward programmable surface structures; however, it strongly relies on complex and cumbersome system architecture, thus limiting the number of programmable structures. Inspired by integrated circuits, we use microfluidics and low-surface-energy coating to develop a programmable superrepellent surface, enabling multi-unit morphology regulation with minimal control components. For pedagogical purposes, we realize the programmable control of 8 × 8 basic structures by 6 control components, affording the preferred morphology to tune wettability. As an extension, the anti-icing and de-icing capabilities of the surface at low temperature are also demonstrated. Moreover, for droplet manipulation, the surface can be freely programmed to create elaborated morphological patterns for directional droplet bouncing and rolling, especially with a gradient pattern for stepless control and a pattern splice for long-distance transport. The integrated-circuit-like programmable superrepellent surface provides new insights into wettability tuning, icephobicity, and droplet manipulation. [Display omitted] • A material-independent pathway toward programmable morphology regulation for wetting surfaces is provided. • An integrated-circuit-like surface is developed to enable multi-unit morphology regulation with minimal control components. • Wettability tuning and icephobicity of the surface are demonstrated. • The surface shows stepless control and long-distance transport in droplet manipulation. [ABSTRACT FROM AUTHOR]

In light of the escalating demands for ice protection related applications in diverse fields, including wind energy, power lines and aerospace, there is a notable surge in interest and attention toward the icephobic materials. The increased focus reflects a growing recognition of the crucial role of materials that demonstrate superior resistance to icing phenomenon. However, the intricate correlation between material wettability and icephobicity remains inadequately elucidated. This study aimed to investigate the factors that influence the relationship between icephobicity and different wetting states. The impact of varying surface topographies was examined within the scope of this investigation. A comprehensive analysis was conducted to evaluate the anti-icing and de-icing performances of the surfaces, encompassing anti-frost, ice shear adhesion strength and electro-thermal heating de-icing aspects. Furthermore, the static and dynamic wettability, along with surface free energy measurements, were also performed to enhance the comprehension of icephobicity variation. The detailed water condensation on various surfaces was meticulously observed using environmental scanning electron microscopy (ESEM). The findings elucidated a strong correlation between the icing behaviour and surface topography. It was observed that the surface topography acted as an amplifier, intensifying the deteriorating effect in icephobicity: the formed glaze per unit area exhibited a significant increase with rough asperities; the ice adhesion strength suffered an obvious increase with rough surface and lower hydrophobicity as well as the prolonged ice detachment and overall energy consumption. Therefore, careful consideration should be devoted to the tailoring of surface morphology and wettability when designing and fabricating icephobic surfaces. • Both evolving wetting features and surface morphology significantly affect the icephobic performance. • ESEM observation, surface energy and XPS analysis reveal the contribution of surface adsorption on icephobicity alteration. • Surface topography acts as an amplifier, the increase in roughness could intensify the declining trend in icephobicity. [ABSTRACT FROM AUTHOR]

In recent years, to progress towards carbon emissions reduction, photovoltaic technology has become one of the most significant methods of generating electricity using renewable sources. However, the accumulation of ice and snow during the winter season affects the decrease in the power generation efficiency of photovoltaic modules. As a promising solution, coatings that exhibit anti-icing properties can be used. To date, no efficient ice-phobic coating has been developed for use on photovoltaic panels. In this paper development of transparent silicone-epoxy coatings modified with bi- and tri-functionalized octaspherosilicates was presented. The used organosilicone-based modifiers reveal both types of functional groups: one increases the surface properties and the second compatibility with the polymer matrix. The icephobic properties were discussed by determining an ice adhesion (IA) and a freezing delay time of water droplets (FDT). The coating exhibiting the highest anti-icing performance achieved the IA of 102 kPa and the FDT of 210 min, a 43 % reduction and a 70 times increase in value compared to the unmodified coating, respectively. The performed study included also the characterization of hydrophobic properties: water contact angle (WCA) at room temperature and below 0°C, contact angle hysteresis(CAH), and roll-off angle (RoA) as well as surface roughness and coatings thickness. In addition, the correlations between them and ice adhesion/freezing delay time were determined. It was found that roughness as well as dynamic parameters of the wettability of CAH and RoA have a significant effect on the obtained IA values. Moreover, the developed coatings can be potentially applied to photovoltaic panels, since the conducted modification did not affect the optical properties of the investigated coatings. [Display omitted] [ABSTRACT FROM AUTHOR]

We provide a conceptual framework to correctly measure both ice adhesion strength and interfacial toughness, using a simple push test method, for a complete and comprehensive assessment of ice adhesion on surfaces. [Display omitted] • The ice-substrate fracture mechanism can be stress- or toughness-dominated. • A novel conceptual framework for ice adhesion measurements is provided. • Interfacial toughness measurement procedure based on simple push test is proposed. The interest in the development of icephobic surfaces has pushed towards the definition of standardized processes and parameters to assess ice adhesion, with the ambition of identifying an equivalent method to contact angle measurements used to assess wetting properties. Although most studies focus on the average ice adhesion strength, measured as the force per unit area required to detach ice, much less attention is paid to interfacial toughness, perhaps as its measurement is challenging. In this article, we provide a conceptual framework to correctly measure both ice adhesion strength and interfacial toughness, even using a simple push test method, laying the ground for a complete and comprehensive assessment of surface icephobicity. [ABSTRACT FROM AUTHOR]

The build-up of ice on critical infrastructure could cause severe disruptions and substantial economic consequences. The application of ice-repellent surfaces has been identified as a promising approach to tackle and mitigate the problem. The main challenge is to ensure they can endure harsh environmental conditions and maintain long-term mechanical durability. This study presents an innovative design concept that incorporates phase change liquids with Ni scaffolds and polydimethylsiloxane (PDMS) in a multi-phase ice-repellent construction. Incorporating phase change liquids within the oil-infused surface construction facilitates the absorption and subsequent release of heat during the icing process. The supercooled droplets took significantly longer (7–8 times) to ice on the sample surfaces compared to aluminum alloy, attributed to the solidification of phase change liquids at low temperatures, resulting in decreased oil depletion during de-icing. Furthermore, the durability enhancement effect was validated by the weight maintenance ratio of samples, which remained almost unchanged after undergoing 50 cycles of icing/de-icing tests, providing a practical solution for addressing concerns on oil depletion in prolonged service conditions. • A novel icephobic structure using Ni scaffolds, PDMS infused with phase change oil and aerogel powder was developed. • The inclusion of oil extends the ice formation and reduces oil depletion effectively, enhancing the icephobicity stability. • The infusion of oil with phase change temperature ~ 0 °C into multiphase structure poses beneficial impact on icephobicity. [ABSTRACT FROM AUTHOR]

Anti-icing coatings reduce the freezing onset temperature for water by changing the chemical and physical environment at the water-substrate interface to prevent ice nucleation and growth. Graphene oxide has several attributes that make it attractive as an anti-icing coating and it has been theoretically predicted that graphene oxide has a lower freezing onset temperature than pristine graphene. Here, we test this hypothesis using carefully prepared, well-characterized graphene oxide substrates. We compare the water contact angle for graphene and graphene oxide coatings, both prepared on iridium(111) surfaces. The results show both materials to be transparent to wetting, but indicate a lower freezing onset temperature for graphene oxide than for pristine graphene. The measured water contact angles are dominated by the properties of the underlying Ir(111) substrate while the freezing onset temperature is dictated by the functional groups present on the graphene basal plane. We suggest that the lowering of the freezing onset temperature is caused by the formation of a viscous water layer on the surface. Scanning tunneling microscopy and x-ray photoelectron spectroscopy data are used to evaluate the robustness of the coating material and suggest ways to improve the long-term performance, namely by advancing strategies to avoid water intercalation. Image 1 • Graphene and graphene oxide on Ir(111) are transparent to wetting but not to icing. • Graphene oxide on Ir(111) have a lower freezing onset temperature than pristine graphene on Ir(111). • Wettability and freezing onset temperature of graphene and graphene oxide on Ir(111) are stable over days. • STM and XPS analysis show that the chemical environment on the graphene surfaces change after wetting and icing experiment. [ABSTRACT FROM AUTHOR]

Ice adhesion tests can be correctly understood only if the appropriate fracture mechanism is identified. Here we reframe the theoretical understanding of ice adhesion mechanisms, to predict the type of detachment mechanism for horizontal push tests. [Display omitted] • Identification of ice-substrate fracture mechanisms is critical for ice adhesion. • The critical shear stress is only meaningful in a stress-dominated fracture regime. • The theoretical understanding of ice adhesion mechanisms is reframed. • Fracture model for detachment mechanism prediction is provided. • Guidelines for the correct interpretation of ice adhesion results are provided. Mitigating icing hazards is of interest for many technological applications. One solution is to employ low ice adhesion coatings, either passively or in combination with active de-icing systems. Nevertheless, comparing different low ice adhesion surfaces can be challenging. Studies generally report the average shear stress, calculated as the ratio of applied force to the ice-substrate contact area; however, the fracture mechanism at the ice-substrate interface is rarely reported. There are two fracture mechanisms that can occur at the interface: stress-dominated and toughness-dominated. Average shear stress is only meaningful when performing adhesion tests in a stress-dominated regime; otherwise, interface stresses are underestimated and misleading. This study presents a new understanding of ice adhesion mechanisms combining experimental and numerical methods, demonstrating how the traditional ice adhesion reporting method can lead to errors up to 400%. Using a simple fracture model, the study shows that the stress-dominated fracture regime in the horizontal push test is favored by smaller ice diameter and greater ice thickness, and is also affected by the load force position. The identification of the two fracture regimes is required for the correct understanding and reproducibility of ice adhesion results, enabling better design and characterization of icephobic coatings and materials. [ABSTRACT FROM AUTHOR]

Industries around the world use active methods, which include thermal, mechanical and chemical approaches, to reduce icing on aerodynamic surfaces such as wind turbines and aircraft. However, they are often inefficient, costly, and pollute the environment. For years, new coatings with anti-icing properties (so-called icephobic coatings) have been developed to either replace or work in tandem with active systems. In this study, coatings were designed based on an epoxy gelcoat commonly used for wind turbines through chemical modification with spherosilicate derivatives. Di- and tri-functional spherosilicates have both groups that increase the degree of hydro-/icephobicity of composites and groups capable of interacting with epoxy resin and amine hardener. The icephobicity of the surface was determined using ice adhesion. The lowest value of this parameter reached a value of 186 kPa, a 30 % reduction compared to the unmodified coating. In addition, the hydrophobicity of the surface was determined (the highest water contact angle was equal to 103°). A correlation was observed, proven in many works, that as the surface roughness increases, the anti-icing properties deteriorate. For individual modifications, it was also shown that hydrophobicity has a positive effect on ice adhesion. The work also examined the surface zeta potential and determined the durability of the properties after 100 icing/deicing cycles. [Display omitted] [ABSTRACT FROM AUTHOR]

Ice accretion and accumulation may cause a severe problem in many disparate fields from aircraft to electrical transmission lines. Super-hydrophobic (SHP) surfaces can have a potential anti-icing application due to their extreme water repellency. However, there is a lack in the characterization of icing behavior of these surfaces. Moreover, durability is a major concern for this kind of coatings. One class of super-hydrophobic surfaces is constituted by hierarchical structures, in which a micrometric roughness is combined with a nanometric roughness and finally covered by a low energy chemical finishing. In the present work, we experimentally investigated how the micrometric roughness of the aluminum alloy surface can influence the hierarchical micro-nanostructure and the consequent hydrophobic and anti-icing properties, especially in terms of durability. Aluminum alloy samples were sandblasted or polished to generate a different micrometric roughness. The following steps to obtain a hierarchical super-hydrophobic structure (nano-roughness and final low energy chemical treatment) were kept constant for all samples. The hydrophobic properties were characterized at room and low temperatures and the anti-icing behavior was measured by shear stress tests. Several repetitions of the shear stress measurement on the same samples and icing- thaw cycles were conducted to study the durability of the coatings. This work describes an easy, fast and economic process to obtain super-hydrophobic materials with durable anti-icing properties, with interesting applications in many industrial fields. • Icephobic aluminum is obtained by roughening, boiling and coating the surfaces. • Different roughness treatments cause different hydrophobic and icephobic properties. • Hydrophobicity at low temperature gives clues of the icephobicity of the samples. • The sandblasted samples have a promisingly durable icephobicity. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the effect of wear on the ice adhesion of elastomeric coatings. Approaches in designing surfaces with lower ice adhesion include imparting hydrophobicity, lubrication, crosslink density reduction or induction of interfacial slippage. For icephobic surfaces to find widespread use, it is imperative that they are durable. In the current work, a suitable plasticizer is used to modify the cross-link density and stiffness of a polyurethane elastomeric coating. The wear behavior of the modified elastomer under two body abrasion is studied in terms of its weight loss and topography evolution. The wear loss varies with the coating stiffness, wherein the elastomer with lower stiffness exhibits higher weight loss. The evolution of surface topography as a function of wear is analyzed in terms of roughness parameters and autocorrelation length, and its effect on the ice adhesion behavior of the coating. The results show that wear initially increases ice adhesion, but adhesion reduces as wear propagates due to the evolution of surface topography. The study shows that, among the samples tested, a 20%–30% plasticizer content produces a good combination of icephobicity and wear resistance. • The wear and ice adhesion behavior of elastomeric icephobic surfaces are analyzed. • The spatial evolution of wear surface and its effect on ice adhesion are reported. • Ice adhesion with roughness and autocorrelation length evolution are reported. • The impact of the onset and progression of wear on ice adhesion is elucidated. [ABSTRACT FROM AUTHOR]

Highlights • Durable superhydrophobic coating was fabricated via a facile spray method. • The ice adhesive strength was one order of magnitude lower for coated concrete. • A simplified theoretical model was built for coated and uncoated concrete for the first time. Abstract Road icing has brought huge potential safety hazards and hundreds of millions of losses every year. However studies for anti-icing or de-icing coatings on concrete are still rare due to the special features of concrete surfaces. Here superhydrophobic coating was performed on concrete via spray method and the icephobicity was studied experimentally and theoretically. The low ice adhesive strength and good durability of sprayed coatings represent the potential for icephobic concrete and our theoretical model provides effective route for the design of icephobic concrete. [ABSTRACT FROM AUTHOR]

Ice accumulation on aerodynamic surfaces is a well-known aspect in various industries, including wind turbines. Many solutions have been developed for several years to deal with this problem, but until now no suitable and energy-sufficient method available for industrial applications has been found. A potential solution is using hydrophobic and/or icephobic coatings, which would allow one to reduce ice adhesion to surfaces. In this study, modifications of a gelcoat based on unsaturated polyester resin with in-house synthesized polysiloxanes dual-functionalized with allyl glycidyl ether (AGE) and hexyl (HEX) or octyl (OCT) groups were used. Most of the chemical modifications used resulted in an increase in surface hydrophobicity (an increase in water contact angle and a decrease in contact angle hysteresis) and an improvement in icephobicity - a reduction in ice adhesion. The lowest ice adhesion achieved a value equal to 221 kPa (the decrease in ice adhesion was 36 % compared to the unmodified surface). The highest water contact angle exhibited a value of 96 °C. Furthermore, correlations were observed between roughness/wettability and ice adhesion: as roughness and wettability decrease, ice adhesion is reduced. The study also determined the durability of the produced surfaces after 100 icing/deicing cycles and the zeta potential surface. • The addition of organosilicon compounds having non-polar alkyl groups results in an increase in the hydrophobicity. • Chemical modification with functionalized polysiloxanes caused a decrease in ice adhesion. • A trend was observed that as the water contact angle increases and the roughness decreases, ice adhesion decreases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrophobic concrete specimens were created by top-treatment with a DCE solution. • The hydrophobic concrete specimens have contact angles greater than 90°. • Ice-concrete adhesion was measured using a customized direct shear apparatus. • The hydrophobic concrete specimens show more than 83% reduction in ice adhesion. Ice when formed on structural materials exhibits strong bonds, which poses a major challenge to many industries. To remove the ice, the creation of hydrophobic surfaces is used as a passive ice removal technique by reducing ice adhesion. Concrete surfaces treated by Pavix Dual Crystallization Engineered (DCE) material show strong water-repelling characteristics. However, the effect of such treatment on ice adhesion is yet to be studied. To quantify this effect, a series of direct shear tests were performed on concrete specimens with the top surface treated with a Pavix DCE material. TxDOT standard Class S concrete was used as control concrete and mixed at two water-cement ratios, 0.45 and 0.43. Ice-adhesion shear tests were performed on control and DCE-treated concrete disks using a customized direct shear test device at two controlled sub-freezing temperatures, −1 °C and −10 °C. In addition, water-repellent properties and contact angle were measured using a tensiometer under static and receding conditions. Results show reductions of more than 83% in ice adhesion of ice adhesion and more than 98-degree contact angles for DCE-treated concrete specimens. The measured results quantify the anti-icing benefit of DCE treatment and provide insights into understanding the anti-icing mechanism of the treated concrete. [ABSTRACT FROM AUTHOR]

Formation and accretion of ice on the leading edge surface of aircrafts wings may lead to disasters. The current de-icing system for aircraft will build up weight, increase energy consumption and add complexity to the aircraft systems. Development of icephobic coatings is a potential solution to prevent ice formation and/or reduce accretion on the critical surface of aircraft. Icephobic coatings based on poly(dimethylsiloxane) (PDMS) with modification by fluorosilane and incorporation of silica nanoparticles have been fabricated. The hydrophobicity of the coatings has been measured in normal conditions with atmospheric pressure and room temperature, showing improvement of hydrophobicity by the fluorination of PDMS and incorporation of silica nanoparticles. The water droplet icing behaviour shows better anti-icing performance for fluorinated PDMS (F-PDMS)/silica coatings with a rough surface. The ice adhesion strength test results show that F-PDMS coatings without silica nanoparticles have lower ice adhesion strength implying better de-icing performance. The wettability of the coatings was also measured at reduced pressure and temperature, to study the mechanism of higher ice adhesion strength of F-PDMS/silica coatings comparing with F-PDMS based coatings. For the design and fabrication of icephobic coatings, compromise on the roughness induced hydrophobicity may become a critical requirement to avoid mechanical interlock between the ice and the rough surface. [ABSTRACT FROM AUTHOR]

The durability of the superhydrophobic coatings is an important factor in the lifetime of a coating under extreme environmental conditions. In this study, a superhydrophobic surface was developed by using low pressure plasma polymerized HMDSO coatings on an anodized aluminum surface. The stability of coating was studied under accelerated aging conditions such as several icing/de-icing cycles, UV degradation, immersion in distilled water as well as corrosion. It was found that the developed surface can keep its superhydrophobicity (contact angle ~156°) as well as its icephobic properties even after up to 15 icing/de-icing cycles. It was also observed that the coating has a relatively good stability against UV degradation. In addition, the superhydrophobic surface can keep hydrophobic properties after 1000 h immersion in distilled water. Finally, the superhydrophobic plasma polymerized HMDSO coating also provides anti-corrosion protection for the aluminum substrate. [ABSTRACT FROM AUTHOR]

Surface icing almost invariably derives from the precursory step of liquid water encountering the surface. Thus, slippery liquid infused porous surfaces, SLIPS, must possess steady wetting durability, and lubricant stability to function as a reliable hydro−/icephobic surface design especially in outdoor applications. Additionally, they should maintain their phobic performance under shear forces, and possess low sliding friction to act as a slippery, multirepellent surfaces. These characteristics are needed in variable applications ranging from moving and rotating blades to steady surfaces, operating in altering climate conditions. More profound durability testing is needed to examine the loss of surface functionality when the lubricant is depleted from the structure via various routes. In addition, the durability tests should be designed to serve the application-related purposes and thus, to reveal performance differences between slippery surfaces for further analysis and targeted end-use development. Here, we tested the wetting durability and stability of SLIPS with multicycle Wilhelmy plate by dipping the surfaces multiple times in water bath. Additionally, we examined the effects of centrifugal and friction-based shear stress to investigate the lubricant depletion from the structure. Tests that measure the durability and the stability of SLIPS designs are in great need in further developing functional slippery surfaces for real outdoor application coatings which encounter environmental stresses, e.g., wetting and icing. Acknowledging the material differences under specific stresses will guide designing the slippery surfaces towards more specific and functionable end-use applications. • Slippery surfaces have unique properties based on material pairs used. • Thermal expansion of porous solid material influences lubricant depletion. • Forced wetting still challenging for lubricant stabilty. [ABSTRACT FROM AUTHOR]

Fluorinated polysiloxanes with different grafting densities of fluorinated groups were synthesized via hydrosilylation reaction between polymethylhydrosiloxane and tridecafluorooctyl methacrylate (13FMA). By further introduction of vinyltriethoxysilane (VTES), the produced polymers underwent self-crosslinking to generate icephobic coatings. Characterizations of surface chemical composition and morphology of the fluorinated polysiloxanes coatings suggested that the fluorine content and the surface roughness of the coating surface increased with the amount of 13FMA. When the fluorinated polysiloxanes grafted a suitable amount of 13FMA and VTES, supercooled water droplets could easily slip away from the tilted coating surface at − 15 °C, ascribing to its high receding contact angle, and the ice shear strength could reduce to 83 ± 2 kPa. Results of this study further demonstrated the importance of the synergistic effect of silicon and fluorine for contribution to the enhanced icephobicity, and the self-crosslinking fluorinated polysiloxane coatings could find more feasible applications for anti-icing. [ABSTRACT FROM AUTHOR]

Freezing wave propagation among condensed droplets plays an important role in determining ice invasion and subsequent frost growth during condensation frosting processes. Many researchers have shown the use of superhydrophobic surfaces with nanoscale or hierarchical roughness for retarding interdroplet freezing wave propagation. Here we report effective reduction of interdroplet freezing wave propagation by using micropillar patterned superhydrophobic surfaces with emphasis on pillar pitch effect. Systematic experiments were carried out to examine the dependence of the freezing wave propagation velocity and the ice coverage ratio on pillar pitch. We found that given a pillar diameter there is a critical value for pillar pitch where the minimum freezing wave propagation velocity and ice coverage ratio occur. Our results also showed that compared to the smooth hydrophilic/hydrophobic surfaces, with proper pillar pitches the freezing propagation velocity can be reduced by more than one order of magnitude and the ice coverage can be reduced to 1/3. Additionally, our experimental findings revealed three distinctive physical mechanisms/modes. A quantitative mapping of three regimes was obtained to elucidate the significant effects of pillar pitch on interdroplet freezing wave propagation on superhydrophobic substrates with patterned micropillars. [ABSTRACT FROM AUTHOR]

Recent emerging strategies to prepare icephobic coatings have focused on slippery surfaces containing a liquid lubricant with low surface energy, which significantly reduces ice adhesion. In this work, a facile technique was developed for preparation of polysiloxane coatings with efficient and durable icephobicity. Fluorinated polyhedral oligomeric silsesquioxanes (F-POSS-SiH) with different fluorinated groups and Si-H active sites were synthesized via hydrosilylation between fluorinated methacrylates and octakis(dimethylsiloxy) octasilsequioxane. The F-POSS-SiH hybrid compound was subsequently applied as a co-crosslinker in the system of polymethylhydrosiloxane (PMHS) and polymethylvinylsiloxane to create silicone coatings. The low surface energy of fluorinated groups could drive F-POSS-SiH towards the coating surface, leading to a gradient distribution in which F-POSS-SiH was self-assembled on the top surface, while silicone was rich in the bottom layer. Meanwhile, wavy surfaces were generated spontaneously by compressive stress during the coating formation. The wavy microstructure of coatings provided space for the unreacted silicone oil, i.e., low molecular weight PMHS, that could be considered as a liquid lubricant and controlled by the dosage. Therefore, the slippery wavy coatings showed highly icephobic properties with extraordinarily low ice shear strengths at a lowest value of 3.8 ± 1.8 kPa, only 5 percentage of Sylgard 184. Moreover, the coatings remained icephobicity after 15 icing/deicing cycles, demonstrating excellent durability. [ABSTRACT FROM AUTHOR]

The ability of phase change materials (PCMs) to absorb and release large amounts of latent heat has led to great interest in their use in anti-icing applications. Combining PCMs and other passive icephobic strategies such as self-lubricating coatings could enhance anti-icing performance. Here, an icephobic coating is fabricated by impregnating an elastomeric matrix containing PEG-PDMS copolymers with PCM microcapsules. First, a selected mixture of n-dodecane and n-tetradecane is encapsulated within urea–formaldehyde shells using in-situ polymerization. Various concentrations of microcapsules are then added into the self-lubricated PDMS coating and 2.5 wt% of hydroxyl-terminated PEG-PDMS copolymer. Differential scanning calorimetry confirms that the PCM-embedded coating has colder ice nucleation temperatures than the self-lubricating coatings lacking microcapsules. The release of latent heat by the PCMs likely preserves the liquid-like layer for a more extended time and delays ice nucleation. The presence of PCM microcapsules can positively affect self-lubricating characteristics of the matrix containing the PEG-PDMS copolymer to further reducing ice adhesion. The presence of a liquid-like layer lowers ice adhesion strength and decreases ice accumulation on surfaces. These particular properties are further enhanced by the incorporated PCM microcapsules and their ability to release latent heat. Finally, the durability of the fabricated coatings is confirmed after multiple icing/de-icing cycles. Such PCM-impregnated coatings therefore offer potential uses for diverse icephobic applications. [Display omitted] • The synergistic effect of combining different anti-icing strategies can enhance icephobic performance. • Phase change materials (PCMs) release a large amount of energy as latent heat. • The presence of a liquid-like layer lowers ice adhesion strength. • Embedding PCM microcapsules into the PEG-PDMS copolymer–containing matrix enhances anti-icing properties. [ABSTRACT FROM AUTHOR]

Although the superhydrophobic surfaces are preferable for passive anti-icing systems, as they provide water shedding before initiation of ice nucleation, their practical usage is still under debate. This is so, as the superhydrophobic materials are not necessarily icephobic and most of the synthesis techniques are characterized with low fabrication scalability. Here, we describe a rational strategy for the atmospheric icing prevention, based on chemically functionalized carbon soot, suitable for large-scale fabrication of superhydrophobic coatings that exhibit and retain icephobicity in harsh operational conditions. This is achieved through a secondary treatment with ethanol and aqueous fluorocarbon solution, which improves the coating’s mechanical strength without altering its water repellency. Subsequent experimental analyses on the impact dynamics of icy water droplets on soot coated aluminum and steel sheets show that these surfaces remain icephobic in condensate environments and substrate temperatures down to −35 °C. Furthermore, the soot’s icephobicity and non-wettability are retained in multiple icing/de-icing cycles and upon compressed air scavenging, spinning and water jetting with impact velocity of ∼25 m/s. Finally, on frosted soot surfaces, the droplets freeze in a spherical shape and are entirely detached by adding small amount of thermal energy, indicating lower ice adhesion compared to the uncoated metal substrates. [ABSTRACT FROM AUTHOR]

In this study, a comprehensive analysis of the pH-dependent contact angles, freezing temperatures and ice adhesion on aluminium samples is presented. It is not yet known whether externally applied electric fields or charged interfaces sufficiently affect the heterogeneous freezing and ice adhesion in order to provide technical solutions for refrigeration engineering, de-icing techniques and food preservation. It was found that surfaces charges that are generated on polished aluminium samples by changing the pH value of the adjacent KCl solution significantly reduce the advancing contact angle. The effect of surface charges on the freezing behaviour was determined by cooling an array of droplets of KCl solutions with pH values between 3 and 12 with a cooling rate of 1 K min−1. Ice adhesion was evaluated using an in-house developed pusher test at -10 °C in a climate chamber. Both icephobicity tests revealed that surface charges seem ineffective to significantly change the freezing behaviour and ice adhesion strength on polished aluminium samples. [Display omitted] • The advancing contact angles reach their maximum at the potential of zero charge. • Higher ion contents increase the achievable supercooling and decreases ice adhesion. • There is no significant effect of pH-generated surface charge on icephobicity. • Heterogeneous freezing follows a generalised extreme probability density function. • Naturally occurring charges are insufficient to provide icephobicity on Al samples. [ABSTRACT FROM AUTHOR]

The phase change materials (PCMs) have attracted great interest for applications as smart icephobic coatings because of their capability to restore and release energy. PCMs release a large amount of energy as latent heat upon freezing, which is a stimuli-response behavior for anti-icing applications. Such materials embedded within coatings can be applied to exposed infrastructures to protect them against icing. Here, we encapsulated a mixture of PCMs in a urea–formaldehyde (UF) shell by in situ polymerization and then incorporated the microcapsules into a polydimethylsiloxane (PDMS) coating. Microcapsules 5–15 µm in diameter having a shell thickness of about 200 nm were fabricated. Investigating the chemical composition of the fabricated microcapsules confirmed that PCM material was successfully encapsulated within the UF shell. Moreover, the differential scanning calorimetry (DSC) analysis showed that the PCM preserved its phase-change characteristics when encapsulated and embedded within the matrix. Increasing the abundance of microcapsules within the coating lowered the ice nucleation temperature, verified by DSC, and increased the freezing-delay time because of PCM latent heat release. We utilized a custom-made apparatus, called micro-push-off set-up that allowed us to measure ice adhesion at the exact moment that the water droplet was completely frozen. Therefore, it was observed that the presence of the PCM microcapsules reduced ice adhesion strength, through either possible mechanism of the formation of quasi-liquid layer (QLL) or thermal expansion differences. Furthermore, lower ice adhesion resulted in reduced ice accumulation on the PCM-containing coatings, verified by the static accumulation test (SAT). [Display omitted] [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces serving as icephobic surfaces are a passive means of limiting the icing of surfaces. Ice nucleation time depends on not only liquid properties and environmental conditions but also surface features; however, it is challenging to investigate ice nucleation time and the influencing parameters simultaneously. This manuscript presents two approaches, experimental testing and machine learning, to study ice nucleation time on exposed surfaces. Hydrophobic/superhydrophobic silicone rubber surfaces were fabricated, and these surfaces varied in their wettability and roughness parameters. Superhydrophobic surfaces characterized by a higher arithmetic average, root mean squared, ten-point height, maximum height of the profile, and a Gaussian roughness distribution—skewness near 0—had longer ice nucleation times. We then used neural networks to model icephobicity in relation to ice nucleation time. The predicted ice nucleation time of the model, trained using some of the experimental results, demonstrated a good agreement with the experimental outcomes. Furthermore, this machine learning approach determined the relative importance of roughness parameters, surface wettability, temperature, and droplet volume in determining surface icephobicity. The proposed approach provides a starting point for studying heterogeneous ice nucleation prediction through an understanding of the key parameters required to optimize the icephobic behavior of superhydrophobic surfaces. [Display omitted] • Ice nucleation time of water droplet on hydrophobic/superhydrophobic surfaces has been studied experimentally. • The effect of surface wettability, roughness parameters, temperature and droplet volume on ice nucleation time are evaluated. • An innovative method for predicting ice nucleation time using machine learning algorithms is shown. [ABSTRACT FROM AUTHOR]

Low surface energy materials have been extensively investigated for building icephobic surfaces in recent years. Polydimethylsiloxane (PDMS) and fluoropolymers have been introduced to this field, while control of their structures is of importance to produce deicing surfaces. In this work, fluorinated methacrylate block copolymers containing polyhedral oligomeric silsesquioxane (POSS) moieties were synthesized by reversible addition-fragmentation chain transfer polymerization and transformed into thiolated-copolymers by aminolysis to adjust the self-assembly and modify surface morphology. The icephobic coatings were developed via UV-curable thiol-ene reaction with tunable amounts of thiol-modified POSS-fluorinated methacrylate diblock copolymers with vinyl-functionalized PDMS and thiol-functionalized PDMS. Characterizations of atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle showed the evidence of the POSS-fluorinated diblock copolymers on the outmost surface of the coatings. Owing to the crystallization of perfluoroalkyl side groups, the coatings containing thiol-modified poly(methacrylisobutyl POSS)- b -poly(2-perfluorooctylethyl methacrylate) ( S17F ) exhibited excellent icephobicity, and water droplets could rebound completely on all S17F -containing surfaces at both normal and tilt modes before freeze even at −15 °C. The ice shear strengths of the prepared UV-cured coatings were about one-eighth of that on bare aluminum surface, while the coating containing 5% S17F achieved the lowest ice shear strength of 105 ± 12 kPa. It was found that the icephobicity of these coatings were attributed primarily to the synergistic effect of the POSS-fluorinated methacrylate diblock copolymer and the PDMS component. [ABSTRACT FROM AUTHOR]

Polyhedral oligomeric silsesquioxane (POSS)-containing fluorosilicone multi-block methacrylate copolymers (PDMS- b -(PMAPOSS- b -PFMA) 2 ) were synthesized via RAFT polymerization of methacryloisobutyl POSS (MAPOSS) with hexafluorobutyl methacrylate (HFBMA) or dodecafluoroheptyl methacrylate (DFHMA) as different fluorinated side groups. A macro-RAFT chain transfer agent of polydimethylsiloxane with dithiobenzoate groups at both ends was initially used. Characterizations of surface chemical composition and morphology of the copolymer films suggested that the PDFHMA chains with longer fluorinated side groups, as compared with PHFBMA chains, were easy to migrate onto the surface and the surface roughness was enhanced by introducing PMAPOSS segments. The film of multi-block copolymer PDMS- b -(PMAPOSS- b -PDFHMA) 2 produced a fluorine-rich surface due to the enrichment of fluorinated blocks and exhibited the highest receding contact angle (103.8 ± 0.5°) and lowest water contact angle hysteresis (8.7 ± 1.4°) among all the samples, attributed to the introduction of PMAPOSS segments and the synergistic effect of silicon and fluorine. Measurements of icephobic properties demonstrated that the supercooled water droplet could easily slip away from the tilted PDMS- b -(PMAPOSS- b -PDFHMA) 2 surface (45°) at −20 °C and the ice shear strength tended to decrease from 361 kPa to 264 kPa with incorporation of PMAPOSS blocks in comparison with PDMS- b -(PFMA) 2 . However, it was found that decreasing wettability of the block copolymer film did not have significant effect on reducing the ice shear strength. The prepared POSS-containing fluorosilicone multi-block methacrylate copolymers with good icephobicity can be used as icephobic coating materials potentially. [ABSTRACT FROM AUTHOR]

Ice accumulation on solid surfaces adversely affects many applications. Among diverse surface modification methods to reduce ice adhesion strength, superhydrophobic (SHP) surfaces have been considered due to their non-wetting characteristics, which minimize the solid-liquid interface, reducing the actual solid-ice contact area. In this work, the shear adhesion strength required for ice removal was studied for a series of thermoplastic-based SHP coatings with a wide particle content range. It was found that particle content plays a complex role in the shear adhesion strength of the coating, which changes the locus of failure for ice removal. The presence of cracks at higher particle loading (above 40 wt%) significantly changed the behavior of the coating, increasing the shear stress for removal. This was attributed to the ice anchoring effect caused by crack formation and penetration of the freezing water into the cracks. To minimize the ice-SHP coating interface shear adhesion, crack formation should be eliminated incorporating the lowest possible NPs content, preserving the Cassie-Baxter wettability state. In the case of the PU nanocomposite coating, 35 and 40 wt% silica NPs coatings demonstrate the optimal result with very low ice adhesion. As crack formation is a common phenomenon in high content NPs nanocomposite coatings, the composition of nanocomposite coatings should be optimized for each material system to minimized crack presence with appropriate surface energetics. • Higher particle loading caused lower ice adhesion. • Cracks happened when particle loading is too high. • Existence of cracks complicated the failure mode. • Big cracks caused increased ice adhesion. [ABSTRACT FROM AUTHOR]

Experimental results aimed at understanding the different mechanisms of ice accretion on surfaces with different wettabilities are presented. Ice accretion was studied on a hydrophilic and a superhydrophobic surface of NACA 0021 airfoils, during tests inside an icing wind tunnel. Visualization of ice accretion was performed using an infrared camera, which allows an enhanced view of liquid water and ice present on the airfoil surface compared to the optical imaging. The use of the infrared camera permitted identification of different ice shapes and ice formation mechanisms on the test articles: on the hydrophilic sample, a compact ice front accreted, whereas on the superhydrophobic sample, small isolated ice islands formed. In addition, the ice on the superhydrophobic sample was more susceptible to be shed from the surface, as shown by shedding of several ice islands due to aerodynamic drag during tests. Combined analysis of infrared camera images and optical images confirmed that the fraction of the airfoil covered by ice decreases for the superhydrophobic sample, for a two minute test, for all the input heat power tested. [ABSTRACT FROM AUTHOR]

A facile process to fabricate icephobic surfaces was developed by spin-coating the polydimethylsiloxane- b -poly(fluorinated acrylate) (PDMS- b -PFA) block copolymers on the substrate. The surface microstructure and chemical composition of the block copolymer films can be adjusted by changing the PDMS content. Icephobic properties of the copolymer surface were mainly ascribed to “flexible-hard” microphase separation and the ratio of fluorine to silicon. The appropriate microphase domain size and the fluorine/silicon ratio could weaken the interaction of ice and copolymer surface and delay icing of water droplets on the copolymer surface. The copolymers containing 15 wt.% PDMS showed the most outstanding icephobicity by depressing the interaction between ice and the copolymer surface. [ABSTRACT FROM AUTHOR]

• A novel method of preparing the slippery lubricant-infused porous surface is proposed. • Condensation frosting is experimentally investigated on four typical substrates. • Directional icing propagation is impeded on the proposed slippery surface. • Molecular Dynamics simulation explores droplet wetting on slippery surfaces. Anti-propagation and enhanced icephobicity both are critical for anti-icing surfaces. In this work, four types of functional surfaces were prepared to investigate condensation frosting mechanisms (hydrophilic surfaces, hydrophobic slippery lubricant-infused porous surfaces, and two types of superhydrophobic surfaces). Experimental results indicated that no directional icing was identified on both the hydrophilic and slippery surfaces, while it was observed on superhydrophobic surfaces. The mechanisms were explained based on microscopic photos, together with theoretical analysis and Molecular Dynamics simulations. On the hydrophilic surfaces, the initially frozen droplets can induce the icing of some of their neighbours. However, these inter-droplet icing spreading failed to develop into a directional spreading for the whole field of view. On the slippery surfaces, most of the droplets had to freeze locally because the distances among them were beyond the effects of icing bridge. Moreover, the lubricant effects on droplet wetting were investigated using Molecular Dynamics simulation, and the results can support the existence of a lubricant layer beneath droplets. The surface icephobicity was experimentally investigated by measuring the critical shear stress of a frozen droplet. As a whole, the icephobicity of the slippery surface was significantly enhanced. Especially, when the substrate was chilled to −5 °C, the high icephobicity of the slippery surface was highlighted by an order of magnitude lower than that on the hydrophilic surface. Also, the slippery surfaces were fabricated based on silica nanoparticles via a commercially coating spray. This method can be of low economic cost for scalable preparation. Overall, the present work can be helpful for developing anti-icing functional surfaces. [ABSTRACT FROM AUTHOR]

• Developed a multiphysics-multiphase model capable of simulating a droplet impinging a surface. • Model comprises fluid dynamics, heat transfer, contact angle, solidification, adhesion & other. • Model predictions were carefully validated against our new nanocomposite coating. • Work highlights the important effect of using the correct wettability parameters on model accuracy. • Inclusive effort that provides an insight into rebound/adhesion of a droplet impinging a surface. This multiphysics-multiphase numerical study is concerned with the fundamental understanding of the mechanisms associated with the impingement of a supercooled water droplet on superhydrophobic and icephobic surfaces. Specifically, the current finite volume simulations, which incorporate the volume of fluid method (VOF), account for a number of highly coupled physical processes concurrently. These include fluid dynamics, heat transfer, dynamic contact angle, and solidification under the effect of momentum, surface tension, wall adhesion, and gravitational forces. It also overcomes a number of shortcomings that currently exist in the literature that lack the accurate description of surface wettability. The predictions of the model were compared with the findings of an extensive experimental test program involving newly developed superhydrophobic and icephobic coatings. The model predictions were found to be in excellent agreement with the experimental findings. Specifically, our results reveal that as the repellency features of the surface are reduced, the droplet experiences a longer spreading phase, larger spreading diameter, and increased loss in kinetic energy due to the greater wall adhesion and freezing of the interfacial contact surface. These effects would ultimately lead to droplet pinning instead of rebounding. The findings of this research are crucial to anti-icing applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Five polymethyltrifluoropropylsiloxane (PMTFPS)–polyacrylate block copolymers (PMTFPS– b -polyacrylate) were synthesized by free radical polymerization of methyl methacrylate, n -butyl acrylate and hydroxyethyl methacrylate using PMTFPS macroazoinitiator (PMTFPS-MAI) in range of 10–50 mass percentages. The morphology, surface chemical composition and wettability of the prepared copolymer films were investigated by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. Delayed icing time and ice shear strength of the films were also detected for the icephobic purpose. The surface morphologies of the copolymers were different from those of the bulk because of the migration of the PMTFPS segments to the air interface during the film formation. Maximal delayed icing time (186 s at −15 °C) and reduction of the ice shear strength (301 ± 10 kPa) which was significantly lower than that of polyacrylates (804 ± 37 kPa) were achieved when the content of PMTFPS-MAI was 20 wt%. The icephobicity of the copolymers was attributed primarily to the enrichment of PMTFPS on the film surface and synergistic effect of both silicone and fluorine. Thus, the results show that the PMTFPS– b -polyacrylate copolymer can be used as icephobic coating materials potentially. [ABSTRACT FROM AUTHOR]

[Display omitted] • Superhydrophobic surfaces can be ineffective in combating ice accretion at subfreezing temperatures. • We developed a new durable icephobic coatings using epoxy-silica nanocomposite. • Surface chemistry and structure were modified by varying the nanoparticles' concentration to attain durable icephobicity. • The coating can rebound supercooled droplets, reduce nucleation temperatures, delay freezing, and reduce ice adhesion. • The coating demonstrated excellent adhesion strength and consistent performance after repeated icing/thaw cycles. Ice accretion is the process by which a layer of ice builds up on solid objects that are exposed to freezing precipitation or supercooled cloud of droplets. In fact, the onset of ice accretion can be sudden and hazardous. This has motivated the development and deployment of icephobic coatings as an effective strategy to prevent or suppress ice accumulation on critical and functional surfaces. Previously, we reported a scalable technique to fabricate durable superhydrophobic coatings using siloxane-modified epoxy nanocomposites. Herein, we extend our earlier research by investigating the potential of using these nanocomposites as candidates for icephobicity. Accordingly, nanocomposites with varied silica nanoparticles' concentrations were considered in our efforts to modify the surface energy and structure to transform the original superhydrophobic surface into an icephobic surface. Our results indicate that a highly superhydrophobic surface (25 wt% nanocomposite) can be ineffective in combating ice accretion at subfreezing temperatures. In contrast, a nanocomposite with a nanoparticles concentration of 35 wt% was found to (i) facilitate the full rebounding of supercooled droplets, while maintained at −10 °C, (ii) reduce the water nucleation temperature to −12 °C, (iii) delay the freezing process by ∼ 94 s at a temperature of −10 °C, and (iv) reduce the ice adhesion strength to ∼ 230 kPa. This comprehensive assessment of the different aspects of icephobicity was considered essential as it ensures the surface's effectiveness against the variety of conditions that lead to ice accretion. Moreover, the developed nanocomposite coatings demonstrated excellent adhesion strength as well as consistent wettability and icephobicity after being subjected to numerous icing/thaw cycles. The outcome of our effort offers a great potential for the large-scale adoption of siloxane-modified nanocomposites in applications that require protection against ice accretion. [ABSTRACT FROM AUTHOR]

Engineering icephobic coatings has been a long standing effort to address the challenges caused by ice formation and accumulation in our daily lives and in several industrial applications. Therefore, this review summaries trends in the progress of high performance hydrophobic and superhydrophobic polyurethane (PU) based coatings, their potential to be used as icephobic surfaces, applicability in passive anti-icing and consequent drawbacks/challenges. Meanwhile, numerous industrial coatings are recommended, a wide variety of PU based coatings can be produced from a broad range of diisocyanates, polyols and other additives. This makes it possible to obtain various types of tailored coatings from PUs that can serve many specific applications as top coats in different industries due to their specific properties. PU based coatings offer excellent mechanical strength and durability, toughness, good abrasion resistance, etc. However, owing to the fact that they have a lot of polar groups on the surface, PU based coatings are rather hydrophilic in nature. Therefore, achieving superhydrophobic and icephobic PU based coatings remains an important issue for current research and development. The present review aims to shed light on superhydrophobic and icephobic mechanisms that have been pursued to design PU based coatings. At first, a short introduction of the general overview of PU chemistry is presented, followed by a comprehensive review of the state-of-the-art methods that have been used by several researchers to modify and design superhydrophobic and icephobic PU coatings. Finally, the challenges and urgent issues facing further development in this field are discussed. [Display omitted] • Polyurethane (PU) as a promising candidate to develop durable coatings. • Chemistry and properties of different types of PU components, i.e. polyols and isocyanates • State-of-the-art and advances regarding PUs as superhydrophobic coating • PUs as icephobic coating material and different strategies to achieve passive anti-icing. • Drawbacks and future recommendations for designing durable icephobic coatings [ABSTRACT FROM AUTHOR]

Developing superhydrophobic/icephobic coatings is of significance in limiting ice formation, and is an ideal selection to solve the icing issues faced by daily life and industrial production. Recent investigations are mainly focused on scientific research but not practical application. Here, nanocomposite based superhydrophobic PVDF-HFP/SiO 2 /CNTs coatings were designed and fabricated. Large-area nanocomposite coatings have been fabricated, which are robust and adhesive to many substrates. As-synthesized coatings exhibited exceptional water repellency with a contact angle up to 168° and slide angle lower than 2°. Anti-icing performance of the resultant coatings is excellent. Ice formation process on aluminum film was delayed by more than 300 s at −19 °C. A purpose-built equipment was designed to investigate the placement orientation of coated samples on anti-icing performance. It has proved that a small angle of inclination had great benefits to the anti-icing performance of the superhydrophobic coating. Moreover, the nanocomposite coating has its superior deicing characteristic. Ice adhesion strength tested is lower than 10 kPa, denoting ice can be detached naturally by the action of the wind or its own weight. The anti-icing mechanism was proposed based on nucleation theory and heat transfer physics, which will give further guideline for developing superior anti-icing coatings. [Display omitted] • Robust superhydrophobic coating (>160°) was prepared with excellent icephobicity. • Icing time on the nanocomposite coating was delayed more than 300 s at −19 °C. • Fabricated coating with extremely low ice adhesion strength can be used repeatedly. • Superhydrophobicity maintains in many substrates with various preparation methods. [ABSTRACT FROM AUTHOR]

Abstract: Aluminum alloys are widely used for outdoor structures such as ground wires and phase conductors of overhead power lines, as well as aircrafts wings and fuselage. To protect these surfaces against excessive ice accumulation, icephobic coatings must be highly reliable and durable. New coatings with icephobic characteristics and excellent mechanical properties have been developed. The method consisted in depositing an extremely adherent poly(tetrafluoroethylene) (PTFE) coating on an Al2O3 underlayer produced by anodizing in a phosphoric acid electrolyte followed by an oxide etching step to enhance surface roughness. PTFE impregnation was carried out at low temperature (320°C) and coating adhesion was assessed using tape and bend tests. Some of these coatings showed superhydrophobic properties; ice adhesion was around four times lower than bare aluminum. As well, they remained effective after ten ice-shedding events using an aggressive centrifugal technique. Moreover, no sign of PTFE degradation after 14 ice removals was noted and the coatings remained extremely adherent and very hydrophobic. This technique therefore shows very good potential and could be applied to new high-voltage overhead aluminum cables as protection against excessive ice or snow accumulation. [ABSTRACT FROM AUTHOR]

Abstract: A superhydrophobic and icephobic surface were investigated on aluminum alloy substrate. Anodizing was used first to create a micro-nanostructured aluminum oxide underlayer on the alloy substrate. In a second step, the rough surface was coated with RF-sputtered polytetrafluoroethylene (PTFE or Teflon®). Scanning electron microscopy images showed a “bird''s nest”-like structure on the anodized surface. The RF-sputtered PTFE coating exhibited a high static contact angle of ∼165° with a very low contact angle hysteresis of ∼3°. X-ray photoelectron spectroscopy (XPS) results showed high quantities of CF3 and CF2 groups, which are responsible for the hydrophobic behavior of the coatings. The performance of this superhydrophobic film was studied under atmospheric icing conditions. These results showed that on superhydrophobic surfaces ice-adhesion strength was 3.5 times lower than on the polished aluminum substrate. [Copyright &y& Elsevier]

Abstract: In order to protect aluminum ground wires and phase conductors of overhead power lines against ice adhesion and excessive accretion, for ensuring safe and reliable power transmission during winter periods, a new coating with icephobic characteristics and satisfactory mechanical properties was developed. The method consisted in depositing an extremely adherent poly(tetrafluoroethylene) or PTFE coating on an Al2O3 underlayer produced by anodisation in either a phosphoric or an oxalic acid electrolyte. PTFE impregnation was carried out at low temperature (320 °C) and coating adhesion was assessed using tape and bend tests. These treatments resulted in highly hydrophobic surfaces with water contact angles lying between 130° and 140°. Ice shear stress was reduced by almost 2.5 times, and the PTFE coatings remained active after several ice shedding events. Morphologies and chemical compositions were studied using scanning electron microscopy, energy dispersive X-Ray analysis, as well as Fourier Transform Infra Red and X-Ray photoelectron spectroscopy. [Copyright &y& Elsevier]

Icephobic coatings offer an effective solution for protecting infrastructures subjected to harsh cold-weather environments. Aqueous self-lubricating coatings, derived from the principles of ice skate sliding over ice, provide a cost-effective anti-icing method. Here, we fabricate aqueous self-lubricating coatings by adding polydimethylsiloxane-poly (ethylene glycol) (PEG-PDMS) copolymers to a PDMS matrix. We analyzed the wettability, morphology, and topography of the fabricated coatings using a goniometer, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. Differential scanning calorimetry (DSC), push-off and centrifugal tests detailed the icephobic characteristics of the coating surfaces. Blending PEG-PDMS into the elastomeric matrix enhanced the effective contact area between the water droplet and the coating; the formation of hydrogen bonds between water molecules and the hydrophilic functional groups of the coating produced this effect, and water molecules spread readily over the surface. Increased concentrations of these functional groups increased the freezing-delay time and reduced ice adhesion strength, likely owing to the formation of a quasi-liquid-like layer. Nonetheless, the immiscibility of the PEG-PDMS copolymer within the PDMS matrix can negatively affect wettability and the icephobic characteristics of the coatings. An optimized copolymer content of 5% produced a durable icephobic aqueous self-lubricating coating. [Display omitted] • Increasing the PEG-PDMS copolymer content tends to enhance surface wettability. • Changing copolymer percentage results in positive effects on the icephobic characteristics. • The effect of the miscibility of the copolymer in the elastomer matrix on the freezing-delay time is investigated. • The push-off and centrifugal tests are used to evaluate the effect of PEG-PDMS content on ice adhesion strength. [ABSTRACT FROM AUTHOR]

The analysis of wetting behavior of self-assembled monolayers of alkylsilanes is presented. A simple model accounting for various surface fractions of CH3 and CH2 groups (self-assembly order/disorder) is used. The effect of inclusion of air in the structure of rough silanized surfaces is also considered. The importance of reduced solid–water contact area and assembly order of organic monomers is demonstrated for achieving both high contact angle and low sliding angle. As coatings with low surface energy, these materials may be of potential use for ice-repellent purposes. [Copyright &y& Elsevier]

The formation, adhesion, and accumulation of ice on surfaces can cause both economic and safety issues related to, for example, reduced efficiency in energy generation, increased energy consumption, as well as mechanical and electrical failures. Smart icephobic coatings have attracted significant attention because of their responsive behaviors to external stimuli. Such coatings on exposed surfaces can respond to changes in surrounding environmental conditions or stimuli, such as temperature, electrical and magnetic fields, and pH. Several smart icephobic coatings have been developed; most aim to reduce ice adhesion, decrease the temperature of ice nucleation, and delay freezing time. This review presents recent scientific progress in the realm of smart icephobic coatings. Although these approaches offer a great potential in applications requiring icephobic surface behavior, most related research remains in the early stages and requires more thorough investigation. [Display omitted] • Literature review of new generations of icephobic coatings • The general concepts related to ice and icephobicity were studied. • Smart icephobic coatings were classified. • Stimuli-responsive-based strategies to combat icing were summarized. [ABSTRACT FROM AUTHOR]

Ice accretion on surfaces exposed to supercooled drops is a major issue in several fields, especially for aircraft. The severity and hazardousness of this phenomenon largely depends on the environmental conditions met by the surface. Currently, active ice protection systems are applied to limit the risks related to ice accretion on aircraft, but intense efforts are devoted to the development of passive ice protection systems to overcome their limitations. Anti-wetting materials have been explored as potential icephobic surfaces, with the Slippery, Liquid-Infused Porous Surfaces approach (SLIPS) being one of the most innovative and intriguing possible solutions. However, the literature lacks a proper characterization of the behavior of SLIPS in icing wind tunnel tests that simulate the different icing conditions. In our work, we report the fabrication of ceramic-based coatings as per the SLIPS approach, utilizing two different ceramic porous matrixes and several infused liquids; we also assess the ability of these coatings to reduce ice accretion in icing wind tunnel tests in both glaze and rime icing regimes, as well as their properties in terms of reduced ice adhesion. Observing the remarkable icephobic behavior displayed by these materials in both types of tests, SLIPS gain significant consideration as candidate passive ice protection systems for aeronautical applications. • Fabrication of anti-wetting, liquid-infused surfaces with different characteristics • Coatings show reduced glaze ice accretion in icing wind tunnel tests. • Ice adhesion is reduced by an order of magnitude on coated surfaces. [ABSTRACT FROM AUTHOR]

[Display omitted] • PCM microcapsule modification can delay frosting on bitumen in repeatable cycles. • Condensation deposit forms around freezing droplet while its temperature jumps 0°C. • Bitumen temperature and RH controls initial condensation regardless of cooling rate. • Water freezes on bitumen at lower temperatures at low RH or fast cooling rates. • Cascade freezing expands across supercooled droplets, ice bridging links droplets. Freezing of atmospheric water on bituminous construction and road surfaces is a recurring event during winter. However, droplet freezing on bitumen and passive inhibition methods are poorly understood. Here we investigate relative humidity and substrate cooling effects on condensation freezing on subzero temperature bituminous surfaces and find that droplet freezing is explosive, with rapid local heating. We explain the related physics and find that relative humidity and cooling rate can affect droplet sizes and freezing temperatures. We then rationally embed phase change material microcapsules in bitumen, harnessing their latent heat to significantly delay freezing, demonstrating a viable option for frost mitigation. [ABSTRACT FROM AUTHOR]

• FDTD simulation illustrated SiO 2 nanoparticles possessed light-induced self-heating and enhanced light absorption ability on contiguous semiconductor. • Solar thermal coating composite possessed superior solar thermal property, superhydrophobicity, icephobicity and stability. • The strategy that simulation guided synthesis provides a new design method for multifunctional photothermal composite. A finite difference time domain (FDTD) simulation was adopted to initially illuminate a neglected phenomenon that SiO 2 nanospheres in superhydrophobic layer could enhance the light absorption capacity of the layer itself, and of the contiguous photothermal semiconductor simultaneously. Guided by this simulation, a solar thermal coating (STC) composed of superhydrophobic SiO 2 nanospheres and CuFeMnO 4 /PDMS was assembled to achieve highly efficient icephobicity. The accurate tests illustrated the temperature rise originated from the semiconductor layer by photothermal effect and superhydrophobic layer by self-heating effect, which was consistent with the simulation results. Depending on the high photothermal conversion efficiency, the freezing temperature of droplets on STC dropped to −35 °C, the ice adhesion strength decreased from 78.5 kPa to 12.1 kPa and an ice layer was removed within 99 s under the light illumination. Furthermore, STC could be further adopted in a cold natural environment, and deicing in 12 min. The simulation-guided construction of STC provides a new design strategy for icephobic coatings and new insights on energy management analysis in superhydrophobic photothermal composite coating. [ABSTRACT FROM AUTHOR]

• A first review on polysiloxane as icephobic materials. • Icephobic surfaces were categorized by their low-ice-adhesion mechanisms. • The advantages and shortcomings of each polysiloxane material group were assessed. • A reference coating thickness and a lower bound of ice adhesion were identified. • The challenges in applying the polysiloxane materials were discussed. Polysiloxane is one of the most favorite polymeric materials used in the emerging field of passive surface icephobicity; This is due to its tailorable softness, hydrophobicity, and relatively high durability. Given the state-of-the-art ice adhesion strength of polysiloxane surfaces has reached a threshold below 1 kPa, a timely survey on the published polysiloxane icephobic surfaces can serve as a valuable reference concerning how far the research field has already progressed and how much potential remains to be exploited for the future development of polymeric icephobic materials. This review categorizes the use of polysiloxane materials for icephobic strategies into three classes according to their surface stiffness. The advantages and shortcomings of each polysiloxane material group are assessed. By scrutinizing the current ice adhesion strength theory, a reference coating thickness is identified, which can be used for optimizing icephobic coating design. A surface icephobicity diagram is also presented, where a lower bound of ice adhesion on a smooth surface is derived, depicting the needs of incorporating different mechanisms to break the theoretical low ice adhesion limit. Finally, the challenges in applying the polysiloxane icephobic materials are discussed, and the possible key research directions are highlighted. [ABSTRACT FROM AUTHOR]

• A new approach was proposed to enhance durability of icephobic coatings. • Fibres helped to mitigate the impinging energy and prevent stress concentration. • Ice adhesion strength was maintained below 10 kPa after rigorous erosion impacts. • Low ice adhesion was attributed to the reduced number and shallowed surface cavities. Icephobic performance of low-ice adhesion polymeric coatings has been studied intensively for passive ice protection. However, limited efforts were conducted to identify strategies for enhancing the durability of the coatings to maintain low ice adhesion after erosion impact. In this work, we developed and investigated several polyurethane-based nanocomposite and fibre-reinforced coatings to understand the deteriorating behaviour of the coatings under rigorous impinging erosion tests and the subsequent impact on ice adhesion. The inclusion of fillers resulted in up to 38 points increase in Shore hardness relative to the pristine PU coatings. The ice adhesion strengths on 3 wt% nanoparticle-reinforced coatings after the erosion tests were nearly halved, whereas, a 5-fold reduction was observed on 3 wt% fibre-reinforced coatings compared to that of the pure PU coatings. Our results indicated that the incorporation of fillers was effective in reducing the ice anchoring points, and that, after the impingement, the icephobic performance was retained by either lowering surface roughness or by minimizing surface deterioration. Fibres took a more effective role in limiting crack initiation and resisting crack propagation. The ice adhesion strength of the coatings increased from 5.6 kPa to 8.4 kPa with 20 wt% carbon fibres incorporated PU coatings, essentially keeping the adhesion below 10 kPa even after rigorous impinging tests and a ∼10-fold reduction in ice adhesion strength as compared to the pure PU coatings. The incorporation of the fibres led to enhanced durability and retention of excellent icephobic performance via a mechanism that is adaptable to other polymeric coatings. [ABSTRACT FROM AUTHOR]

• Micro compression molding and atmospheric pressure plasma produced superhydrophobic micro-nanostructured silicone surfaces. • Two forms of icing conditions and two ice adhesion measurement techniques were used. • Delayed ice formation and reduced ice adhesion strength were observed. • The durability properties were tested through a series of mechanical and chemical experiments. • The loss of anti-wetting properties in some destructive tests were recovered. The durability of anti-wetting properties is of great importance for ensuring long-lasting superhydrophobic and icephobic surfaces that require minimal maintenance and resurfacing. Herein, we fabricated superhydrophobic silicone rubber surfaces having ultra-water repellency and icephobic properties via two industrially applicable methods: micro compression molding (μCM) and atmospheric pressure plasma (APP) treatment. We produced surfaces covered by micro-nanostructures of differing sizes. We evaluated the anti-icing properties (delayed ice formation) and de-icing properties (reduced ice adhesion strength) of the produced surfaces that were subjected to two forms of icing conditions. The well-known ice adhesion measurement techniques, i.e., the centrifuge adhesion and push-off tests, provided quantitative comparisons of the ice adhesion strength of the produced surfaces. We observed two different mechanical deformations during the ice detachment from the surfaces. Although both superhydrophobic surfaces reduced ice adhesion strength, the smaller surface micro-nanostructures produced a greater reduction in ice adhesion by favoring less ice interlocking with the surface asperities. To rigorously assess the durability of the produced surfaces, we carried out a comprehensive series of experiments that covered a wide range of real-life conditions. Under harsh environmental conditions, the surfaces maintained a water contact angle and contact angle hysteresis of >150° and <10°, respectively, thereby confirming the resistance of the superhydrophobic silicone surfaces to severe chemical and mechanical damage. In some cases where water repellency was lost, the silicone rubber surfaces demonstrated a satisfactory recovery of their anti-wetting properties. [ABSTRACT FROM AUTHOR]

In-flight icing due to the impingement of supercooled water droplets modifies the shape of the aerodynamic surfaces of aircraft, resulting in lower stall speeds and higher fuel consumption. Icephobic coatings help reducing the adhesion strength of ice to a surface and represent a promising technology to support mechanical/thermal ice protection systems. Superhydrophobic surfaces are water-repellent and embody a straightforward solution to tackle icing: nanostructured porous aluminium oxide layers are generated with anodization and superhydrophobicity can be reached by tuning the pores size. However, not much research has been done to verify if such surfaces are generally icephobic in representative icing conditions, or if they need to have additional properties to effectively reduce ice adhesion. In this work, we investigate the ice adhesion strength on cladded Aluminium Alloy 2024 (AA2024), an alloy commonly used for aerospace components, anodized with different process parameters in sulphuric and oxalic acid and hydrophobized by a commercial fluorinated product. Upon the optimization of the two anodization processes, the micro-/nanostructures generated on the surface were effective in reducing the ice adhesion strength. From icing wind tunnel tests, the surfaces anodized in oxalic acid showed superior icephobic (i.e., lower ice adhesion) properties compared to the ones anodized in sulphuric acid because of their larger air-to-solid surface ratio. The proposed anodization process is fast, easy to perform and to implement in existing production lines, low-cost, and operator- and environmentally-friendly. Unlabelled Image • Anodization in oxalic acid led to surfaces with a decreased ice adhesion strength. • Icephobicity of these surfaces is superior to surfaces generated in sulphuric acid. • Superhydrophobicity does not always lead to icephobicity. • Anodization in oxalic acid is fast and does not require surface pre-treatments. • The chosen chemicals make the process operator- and environmentally-friendly. [ABSTRACT FROM AUTHOR]

An experimental investigation was conducted to evaluate the variations of the surface wettability and ice adhesion strength on a typical hydro−/ice-phobic surface before and after undergoing continuous impingement of water droplets (i.e., rain erosion effects) at relatively high speeds (i.e., up to ~100 m/s) pertinent to Unmanned-Arial-System (UAS) inflight icing mitigation. The experimental study was conducted by leveraging a specially designed rain erosion testing rig available at Iowa State University. Micro-sized water droplets carried by an air jet flow were injected normally onto a test plate coated with a typical Super-Hydrophobic Surface (SHS) coating to simulate the scenario with micro-sized water droplets in the cloud impacting onto UAS airframe surfaces. During the experiments, the surface wettability (i.e., in the terms of static, advancing and receding contact angles of water droplets) and the ice adhesion strength on the SHS coated test plate were quantified as a function of the duration of the rain erosion testing. The surface topology changes of the SHS coated surface against the duration of the rain erosion testing were also measured by using an Atomic Force Microscope (AFM) system. The characteristics of the surface wettability and ice adhesion strength on the eroded SHS surface are correlated with the AFM measurement results to elucidate the underlying physics for a better understanding about the rain erosion effects on hydro−/ice-phobic coatings in the context of UAS inflight icing mitigation. • Rain erosion effects on a superhydrophobic surface (SHS) coating were investigated. • Wettability degradation characteristics of SHS due to rain erosion effects was examined. • Strength of ice adhesion to SHS was found to increase rapidly sue to rain erosion effects. • Hierarchical textures on SHS were found to tear away rapidly due to rain erosion effects. • The potential usage of hydro−/ice-phobic coatings for UAS icing mitigation was explored. [ABSTRACT FROM AUTHOR]