Spraying Fabrication of Durable and Transparent Coatings for Anti-Icing Application: Dynamic Water Repellency, Icing Delay, and Ice Adhesion

Abstract

Anti-icing/icephobic coatings, typically applied in the form of surface functional materials, are considered to be an ideal selection to solve the icing issues faced by daily life and industrial production. However, the applications of anti-icing coatings are greatly limited by the two main challenges: bonding strength with substrates and stability of the high anti-icing performance. Here, we designed and fabricated a kind of high-performance superhydrophobic fluorinated silica (F-SiO 2 )@polydimethylsiloxane coatings and further emphasized the improvement of the bonding strength with substrates and the maintenance of high antiicing performance. The resultant coatings exhibited excellent water repellency with a contact angle up to 155.3°and a very short contact time (∼10.2 ms) of impact droplets. At low temperatures, the coming droplets still rapidly rebounded off the coating surface, and the superhydrophobic coatings displayed a more than 50-fold increase of freezing time comparing with bare aluminum. The ice adhesion strength on the coatings was only 26.3 kPa, which was far less than that (821.9 kPa) of bare aluminum. Furthermore, the nanoporous structures constructed by anodic oxidation could tremendously enhance the bonding strength of the coatings with the substrate, which was evaluated through a standard method (ASTM D3359). The anti-icing properties still retained high stability under the conditions of 30 icing/deicing cycles, soaking, and scouring of acid solution (pH = 5.6). This work can effectively push the anti-icing coatings toward a real-world application.

Droplet Impact on the Cold Elastic Superhydrophobic Membrane with Low Ice Adhesion

“…The image sequences of the droplet impacting the cold rigid and elastic superhydrophobic membrane surfaces with different stiffness (−5 • C) at a speed of 1.5 m/s (corresponding to We = 90) are illustrated in Figure 5. The stiffness k is calculated by k = 48EI l 3 , where E is the elastic modulus (E ≈ 0.67 MPa) and I (I = wh 3 12 ) is the area moment of inertia. The stiffness of the elastic superhydrophobic membranes with thickness h of~0.5 mm and~1 mm are 0.65 and 5.21 N/m, respectively.…”

“…Ice accumulation is a common and serious phenomenon that exists in numerous industrial fields such as electricity transportation, wind turbine and air conditioning [1][2][3]. The ice accretion may cause the failure of conductors, decrease the efficiency of air conditioning and even cause the system shutdown, which would pose a huge energy consumption and potential safety hazard [4,5].…”

Bioinspired Superhydrophobic Progress and Recent Advances of Its Functional Application

“…目前的超疏水防覆冰领域主要体现在三个方面: 减少液滴与界面长时间接触(小液滴在过冷条件下 的反弹)、降低凝固点及延迟结冰时间(微小冷凝液 滴的自跳动现象)和构建疏冰低结冰粘附力表面(滑 液面防冰)。当固-液界面出现结冰现象时, 表面结 冰过程可用开尔文方程和克拉伯龙方程分析小液滴 的分类形核理论和抑制形核能理论 [84] 来分析该表 面的防覆冰能力(图 3)。 超疏水表面普遍存在小液滴弹跳现象 [87][88][89] , 其 原因为遭到液滴撞击时的小液滴动能不易转变为超 疏水表面内能 [90][91] , 超疏水涂层的表面张力较小 (图 4)。因此, 当低温环境下的超疏水表面出现弹跳 现象时, 弹跳的液滴于结冰形核前离开超疏水表面, 从而减缓界面的过冷传输过程, 达到防覆冰的目 的。Quéré 课题组 [92] 研究表明, 液滴以 20~230 cm/s 的速度撞击超疏水表面时, 液滴和界面的接触时间 仅与液滴半径和界面张力有关, 与撞击速度无关。 冷凝在微纳结构内部的小液滴受限于粗糙结构 而导致其形状改变, 小液滴汇集结合后的液滴自由 能过剩, 即表面自由能大于液滴平衡态自由能, 最 终液滴在低表能的超疏水表面弹起或滚动离开 [93] , 宏观表现为小液滴连续的自跳动现象(图 5)。 通过控 制微纳结构的尺寸变化及其不同的结构粗糙度, 可 提高超疏水表面的自跳动防冰效果 [94][95][96] 。超疏水涂 层的表面能较小且静态接触角较大, 导致液滴与超 疏水表面的接触面积较小。根据小液滴的分类形核 理论和抑制形核能 [84] , 控制超疏水表面的粗糙度小 于且无限接近于临界晶核的最小半径值 [97] , 此时, 超疏水表面具有结冰延迟效果 [98][99] 。 覆冰与物体表面存在范德华力、氢键作用和静 电引力(表 3)。 界面接触时范德华力普遍存在且与接 触面面积呈现线性关系, 具有亲水基团表面的氢键 作用较强, 静电引力是三种作用力中最重要的影响 结冰粘附力因素, 材料的介电常数越低, 覆冰的静 电引力作用越小 [100] 。研究表明, 低表面能的超疏水 表面可降低覆冰的粘附力 [101][102][103][104][105][106][107] , 但由于超疏水表 面形貌和微纳结构的差异, 具体的防结冰及降低覆 冰粘附力的机理研究还有待完善。 图 2 高透明超疏水涂层 [80][81] Fig. 2 (a) Transparent and durable superhydrophobic glass [80] and (b) highly transparent and superhydrophobic nanopaper [81] 无 机 材 料 学 报 第 34 卷 图 3 防-疏冰机理和小液滴形核结冰过程 [85][86] Fig.…”

Multifunctional Superwetting Composite Coatings for Long‐Term Anti‐Icing, Air Purification, and Oily Water Separation

“…Superwetting surfaces, with special structure and function, have caused extensive attention to solve many thorny problems, such as self‐cleaning, [ 1,2 ] anti‐fouling, [ 3,4 ] anti‐icing, [ 5–7 ] anti‐corrosion, [ 8,9 ] drag reduction, [ 10,11 ] moisture‐proofing, [ 12 ] water harvesting, [ 13,14 ] and oil–water separation. [ 15–17 ] On the application side, however, the surfaces with nano‐ and/or micro‐meter scale structures were easily damaged by mechanical impact or deformation, resulting in functional failure.…”

“…Since the strategy that the double‐sided adhesive can be used as primer to enhance the wear resistance of topcoat been proposed, [ 29 ] many resins have been proved to effectively improve the adhesion of coating. For example, adhesive, such as polydimethylsiloxane (PDMS), [ 6,30 ] epoxy resin (EP), [ 31 ] polymethyl methacrylate (PMMA), [ 3,32 ] polyurethane (PU), [ 33,34 ] or polybutadiene (PB), [ 35 ] has been demonstrated as one of several promising strategies to enhance its mechanical durability. However, there are still issues about its service life.…”