Ice accumulation poses a series of severe issues in daily life. Inspired by the nature, superwettability surfaces have attracted great interests from fundamental research to anti-icing and ice-phobic applications. Here, recently published literature about the mechanism of ice prevention is reviewed, with a focus on the anti-icing and ice-phobic mechanisms, encompassing the behavior of condensate microdrops on the surface, wetting, ice nucleation, and freezing. Then, a detailed account of the innovative fabrication and fundamental research of anti-icing materials with special wettability is summarized with a focus on recent progresses including low-surface energy coatings and liquid-infused layered coatings. Finally, special attention is paid to a discussion about advantages and disadvantages of the technologies, as well as factors that affect the anti-icing and ice-phobic efficiency. Outlooks and the challenges for future development of the anti-icing and ice-phobic technology are presented and discussed.

Bioinspired Surfaces with Superwettability for Anti-Icing and Ice-Phobic Application: Concept, Mechanism, and Design

Ice accumulation on solid surfaces can incur irretrievable losses and catastrophic affairs in daily life. These issues can be addressed and strategically alleviated by adopting effective methods for remediation. Compared with conventional active deicing strategies, such as electro-impulse, the chemical method, and the mechanical deicing approach, passive anti-icing and ice-phobic surfaces inspired by animals in nature and plants can confer an exceedingly profound advantage. Herein, the kinetics of ice nucleation, ice accretion on solid surfaces, and heat transformation during ice formation were investigated. Then, the reduced attachment pathway of water droplets on substrate surfaces is reviewed for the purpose of achieving the self-removal of water droplets and averting the wettability transition on superhydrophobic surfaces. Furthermore, recent biomimetic anti-icing strategies regarding reduction of ice adhesion, decrease of ice nucleation temperature, and delay of freeze time were considered. Significantly, other external factors affecting ice formation and growth, such as environmental humidity and exoteric gas flow, are comprehensively discussed. Finally, outstanding mechanical and chemical stability are vital for lengthening the durability and longevity of anti-icing/ice-phobic surfaces. This article discusses all of these matters along with outlooks for future research directions for anti-icing and ice-phobic surfaces.

Fundamentals of icing and common strategies for designing biomimetic anti-icing surfaces

For faster and greener anti-icing/deicing, a new generation of anti-icing materials are expected to possess both passive anti-icing properties and active deicing properties. The photothermal effect of carbon nanotubes (CNTs) is used in the field of photothermal cancer therapy, while the application in anti-icing/deicing is seldom investigated. Superhydrophobic SiC/CNTs coatings with photothermal deicing and passive anti-icing properties were first prepared by a simple spray-coating method. The results of 3D profile and microstructure observed via scanning electron microscopy demonstrate that the micronanostructure combined with peaklike SiC microstructure and villiform CNTs nanostructure makes the coatings surface superhydrophobic, exhibiting a water contact angle of up to 161° and a roll angle as low as 2°. This micronanostructure can also reduce ice anchoring and ice adhesion strength. Utilizing the photothermal effect of CNTs, the surface temperature of the coatings is rapidly increased upon near-infrared light (808 nm) irradiation. The heat is transferred rapidly to the surroundings by highly thermal conductive CNTs. The light-to-heat conversion efficiency in deicing tests is approximately 50.94%, achieving a highly efficient remote deicing effect. This superhydrophobic coating combining photothermal deicing and passive anti-icing properties is expected to be further used in various practical applications and in development of a new generation of anti-icing/deicing coatings.

Superhydrophobic SiC/CNTs Coatings with Photothermal Deicing and Passive Anti-Icing Properties.

Magnetic responsive and flexible composite superhydrophobic photothermal film for passive anti-icing/active deicing

Considerable work has been done on preventing ice formation on insulators and the modification of the surface characteristics by increasing the contact angle and decreasing the adherent force have been tried with some degree of success. Heating by electric current has however proved to be an effective and practical method for de-icing transmission lines, but difficult to apply to insulators. A room temperature vulcanized (RTV) silicone rubber coating containing sufficient carbon black to render it partially conducting but not enough carbon to lose its surface hydrophobicity, has been investigated to determine if the heat generated would suffice to inhibit ice growth on the insulators. The heat exchange progress was analyzed and the leakage current through it to prevent ice forming was estimated and coatings developed accordingly. The anti-icing performances of these RTV silicone rubber coatings with different leakage current magnitudes were compared in a climate chamber. The results showed that the surface heating effect, together with the hydrophobicity, could significantly reduce the formation of ice on insulators.

Anti-icing performance of RTV coatings on porcelain insulators by controlling the leakage current

Prevention of icing flashover on transmission lines has become an important problem. A new method for mitigating effects of glaze ice on energized insulators has been developed. Semiconductive silicone rubber was painted on the bottom of suspension disc insulators, while the upper ceramic surface was untreated. An electrically conductive path was formed when supercooled water or droplets bridged the uncoated areas. The power loss was limited when there was no precipitation. The heat and partial discharge energy generated by the leakage current melted the original ice accretion on the insulator surface. The electrical performance of the insulator string with this kind of coating under freezing rain conditions was comparable with that of a clean insulator string. The impact of the ambient temperature on the anti-icing performance was also evaluated. In addition, the performance of the insulator with bottom surface semiconductive coating under fog conditions was compared with an uncoated string.

Study of anti-icing performance of insulator strings bottom-coated with semiconductive silicone rubber coating

This paper addresses the salt migration during phase transition of cooling water in the icicle growth period. This paper contains three parts, first, application of Fick's law in salt migration process; second, salt concentration measurement of icicles in artificial climate chamber; third, ice flashover experiments during melting period. Based on freezing model analysis, cooling water started to freeze from the water-insulator interface. Fick's diffusion law was applied to deduce the change of salt content in the liquid water. It was investigated that the melting water conductivity of icicle tips was proportional to the applied water conductivity. Freezing velocity (in mm/h) played important roles on the salt migration process during the growth of icicles and the melting water conductivity of an icicle tip under 2.6 mm/h was 1.66 times higher than under 3.6 mm/h. Special attention was paid to the ice flashover under non-bridged and bridged icicles. Icing experiments under energized condition showed that the conductivity of icicle tips increased by 70 percent when icicles grew to bridge the gap between adjacent sheds, which was a critical reason for the decline of the corresponding ice flashover voltage.

Mechanism of salt migration in icicles during phase transition and its impact on ice flashover

Icing of transmission lines due to extreme weather conditions has caused many failures in power networks worldwide [1]. As China has much of its land 2,000 m above sea level, intense snow and ice storms at this altitude have caused significant losses to the economy, and the harsh conditions have made life very difficult in these regions [2]. The winter of 2008/2009 was particularly harsh with freezing rain, which continued for more than three weeks in the central provinces, causing 218 ice flashovers. In particular, Hunan and Jiangxi Provinces experienced the severest storms resulting in damage to 37% of the 500-kV power transmission towers, collapsing many towers. Considerable work has been done in China on understanding the reasons for, and preventing, the icing flashover of insulators [3]-[10], but in this article the various anti-icing and de-icing methods for insulators currently being investigated in China are discussed with particular reference to the application of semiconductive silicone rubber coatings on insulators.

http://ieeexplore.ieee.org/iel7/57/6749562/06749572.pdf

Development of anti-icing coatings applied to insulators in China

Partial coating of insulators with semiconductive silicone rubber has proved to be a potential method for reducing ice accretion on insulators. The performance of the coated insulator strings is mainly determined by the insulator parameters, the coating resistance, and the coating area covering the insulator surface. This research is to investigate the effect of using semiconductive silicone rubber coating on the anti-icing performance of ceramic insulators, considering the coating resistance and the coating area. A series of icing tests was carried out in a climate room and the results obtained from tests on a single insulator unit were extended to short insulator strings. The experimental results showed that the magnitude of the appropriate coating resistance was below $0.3 ~{\rm M}\Omega$ in the freezing condition recommended, and that the suitable width of the band of the uncoated area was about 5 to 8 cm. Since the main heating power was consumed in the region of the uncoated band, the uncoated area should better be close to the edge of the top surface of the insulator, in which case the icicles could fall off more easily.

Xiaoxing Wei

Papers

Anti-icing performance of RTV coatings on porcelain insulators by controlling the leakage current

Study of anti-icing performance of insulator strings bottom-coated with semiconductive silicone rubber coating

Mechanism of salt migration in icicles during phase transition and its impact on ice flashover

Development of anti-icing coatings applied to insulators in China

Effect of the Parameters of the Semiconductive Coating on the Anti-Icing Performance of the Insulators