Potential use of smart coatings for icephobic applications: A review
Graphical abstract
Introduction
Water is a unique substance that exists in three states in nature. Through a change in temperature and/or pressure, liquid water can undergo a phase change to solidify as ice; however, the nature of this solid form can vary (Table 1). Moreover, these ice forms can strongly adhere to exposed infrastructures [1]. This icing can result in serious safety, operational, and economic issues for a wide range of settings, including road, sea, and rail transportation, power transmission, telecommunications, wind turbines, pumps, and heat exchangers (Fig. 1) [[2], [3], [4], [5], [6]]. For example, wind turbines located in areas of harsh cold-weather conditions must often cease to function during winter because of hazards related to ice accumulation. This stoppage results in the loss of almost half of the annual energy production of these wind turbines [7,8]. Ice build-up on the blade surface increases surface roughness, thereby disrupting airflow around the airfoil and reducing energy production. This phenomenon can prevent the operation of the wind turbine for days and even weeks. Ice adhesion and accumulation can also cause a load imbalance on the blade, and this ice presence accelerates the wear of the turbine components; maintenance costs are therefore heightened, and the service life of the turbine is reduced [9].
Wet snow conditions can also produce catastrophic blackouts of electrical networks involving high-voltage and medium-voltage power lines. The related costs can be quite high. In Italy, for example, damages related to these particular weather conditions cause losses of more than €200 million/year [15]. In 2008, China experienced massive economic losses (about $1.5 billion US) because of disruptions to transmission lines [16]. These blackouts occur because of ice formation on conductors and insulators. The forming of an ice layer on an insulator surface can lead to electrical flashover failure during icing and later during ice melting. The sudden shedding of accreted ice accretion can also mechanically damage power network equipment [17]. The aircraft industry must deal with major icing problems that, in some cases, have resulted in fatal accidents. According to the American Safety Adviser, approximately 12% of all flight accidents between 1990 and 2000 involved icing during adverse weather conditions. Moreover, 92% of ice-induced accidents occurred because of in-flight icing [3]. In 1992, approximately $33 million US was spent worldwide on removing ice from navigation equipment [16]. Increased shipping operations in the Arctic over recent decades have increased climate-related accidents in this region [18]. The accreted ice on the surface of some equipment increases the heat-transfer resistance, thereby decreasing the energy transfer rate. Accreted ice also disrupts the airflow within refrigeration systems to reduce system performance and increase energy consumption by approximately 20% [19].
These financial and mechanical issues have led to greater interest in reducing ice accretion on exposed surfaces subjected to harsh cold-weather environments. In the next section, we describe the concept of icephobicity and present icing mitigation strategies that rely on smart icephobic coatings.
Section snippets
Icephobicity
Much work has focused on understanding the principles of ice formation and growth. As water is cooled to or below 0 °C under atmospheric conditions, a phase transition occurs. As shown in Fig. 2a, ice nucleation begins within a water droplet at the free and solid interfaces as homogeneous and heterogeneous nucleation, respectively [20,21]. Upon the thermodynamic driving force, multiple long-lived hydrogen bonds are spontaneously developed, resulting in the formation of compact ice nuclei. The
Smart coatings
Smart coatings, also called intelligent coatings, have attracted much interest over the last decades owing to their potential use in high-tech industries. Conventional coatings are fabricated to passively protect the substrate and act as a barrier between the substrate and the environment. These coatings provide a constant functionality, which depends on the formulation of the coating, and this functionality remains present over the coating's lifetime. Progress in the coatings industry has led
Smart icephobic coatings
The lack of a universal definition of a smart icephobic coating prevents the clear categorization of these intelligent coatings. Thus, referring to the general definition of smart coatings, a smart icephobic coating senses an environmental stimulus and provides a suitable response; this response results in reduced ice accumulation or a longer delay in ice formation on an exposed surface.
Depending on the types of stimuli and response, smart icephobic coatings can be classified into several
Conclusion
Demands for innovative coatings to mitigate ice accumulation and ice adhesion have guided academic and industrial sectors toward developing smart icephobic coatings because of the multiple advantages of these coatings for solving icing-related issues. In this review, we investigated and classified various smart icephobic coatings in terms of their stimuli response; however, the lack of a comprehensive definition for each response category remains a significant obstacle to their proper
CRediT authorship contribution statement
Mohammadreza Shamshiri: Conceptualization, Methodology, Writing – original draft, Writing – review & editing, Visualization, Investigation, Resources. Reza Jafari: Conceptualization, Writing – review & editing, Supervision, Funding acquisition. Gelareh Momen: Conceptualization, Writing – review & editing, Supervision, Funding acquisition.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors acknowledge all support from the Natural Sciences and Engineering Research Council of Canada (NSERC), Hydro-Québec, and PRIMA Québec.
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