Nano Res.│武汉理工大学谢毅教授:具有梯度和多级结构的高耐候超双疏防污闪涂层材料

WaterOff

2022-09-04 13:05:38

背景介绍

室温硫化硅橡胶（RTV）已被广泛应用于高压绝缘子防污闪，然而RTV表面的疏水特性易遭受破坏，当RTV表面上形成水滴，会导致气-液-固边界处的电场增强，电晕放电导致疏水性降低。疏水性的减弱会降低绝缘表面抑制漏电流和局部放电的能力，从而容易发生闪络事故。近年来，超疏水（SH）材料被认为是传统RTV的一种最有前途的替代材料，可有效提高绝缘子的防污闪性能。在绝缘子表面涂覆超疏水材料，由于其具有超强的拒水能力，可有效防止水粘附在器件表面，赋予绝缘子表面较大的漏电距离，抑制泄露电流，降低闪络的可能性。然而考虑到材料在实际使用过程中，自然界存在的一些污秽物如鸟粪等含有有机污染物。这些有机物容易附着在超疏水绝缘子表面，从而导致可溶性盐类和水的集聚，削弱其污闪性能。

鉴于此，武汉理工大学与伦敦大学学院、华中科技大学等合作，提出了一种具有独特梯度结构的耐久性超疏水超疏油（超双疏）涂层的制备方法并应用于电力设备防污闪领域，由于其优异的拒水拒油性能，在实际使用过程中涂层不会受到自然界中有机污秽物的影响，从而有效提高了高压输电线路绝缘子的防污闪性能。

研究方法

本研究超双疏材料的制备采用喷涂“底漆+面漆”的工艺，通过控制喷涂压力、喷涂距离等获得具有独特梯度结构的超双疏（SAP）涂层。材料的表面形貌、微观结构、表面结构、化学成分等采用SEM、TEM、EDS、FTIR等进行测试分析。采用砂纸打磨的方法测试材料的耐磨性，采用紫外光照、酸碱液浸泡、低温冷冻及高温退火等方法对材料的耐紫外稳定性、耐化学稳定性及耐高温低温稳定性。各种涂层绝缘子（如超疏水、超双疏及RTV 涂层玻璃绝缘子）的污闪试验是在人工污闪试验台上进行，在施加电压之前，绝缘子表面采用人工污秽物（硅藻土和NaCl的混合物）进行污染，并在加湿器的雾室中完全暴露于饱和水蒸汽中15分钟后取出置于污闪试验台进行试验；通过逐渐升压直到发生闪络，并记录闪络电压值。

成果简介

（1）发展了一种具有独特梯度结构的超双疏材料设计及其构筑方法，该梯度结构的构筑有效提高了超双疏涂层材料的耐磨性能。

（2）提出了一种新的污闪性能评估模型，该模型考虑了有机物污染对设备防污闪性能的影响，并通过绝缘子污闪试验进行了验证。研究表明，当超疏水绝缘子表面被有机物污染后，其污闪电压降低，即防污闪性能下降。而超双疏绝缘子在相同条件下污闪性能基本不受影响。

（3）发展了一种采用超双疏涂层材料提高输电线路用绝缘子的污闪性能的方法，其防污闪性能远优于传统RTV。在轻度和重度污染等级下，创制的超双疏绝缘子的污闪电压比传统RTV绝缘子在相同条件下分别提高了29.0% 和42.9%。

图文导读

Figure 1 (a) SEM images of the primer showing mastoid morphologies of the surface. (b) and (c) SEM images of the SH coating displaying hierarchical micro-nanostructure of the surface. (d) The surface superhydrophobicity of SH coating enables the spherical water droplets (dyed with methyl blue) resident on top, while oil drops completely spread on the surface. (e) and (f) SEM images of the SAP coating surface showing hierarchical micro-nanostructure. (g) and (h) The superoleophobicity and superhydrophobicity of the SAP coating enable the spherical dyed water droplets and organic droplets (e.g., bean oil, hexadecane, and castor oil) resident on top. Insets in panels ((a), (c), and (f)) provide the high-magnification SEM images of the corresponding surface. Insets in panels ((d) and (g)) provide the optical images of the resident water droplets on the corresponding coating when measuring WCA. Inset in panel (h) reports the optical image of the hexadecane droplets on the corresponding coating when measuring OCA. (i) Water droplet (5 μL in volume) pinning and re-bouncing behaviour when released from a height of 2.5 mm toward the SAP surface. (j) Dropping dyed water on the fly-ash-contaminated SAP coating to display the self-cleaning performance of the SAP surface.

图1展示了底漆、超疏水（SH）涂层及超双疏（SAP）涂层的表面形貌及表面润湿性能。图1（a-c）中可以看出，制备的纯底漆和“底漆+面漆”超双疏涂层表面具有明显的乳突结构。图1(d)表明，纯超疏水涂层表面水滴（甲基蓝染色）呈球形，而油滴完全浸润表面。图1（g-h）为SAP涂层，由于其优异的疏水疏油性能，水和油滴在表面均为球形。图1(i)展示了水滴在超双疏表面的弹跳行为，图1(j)展示了超双疏涂层表面优异的自清洁效果。

Figure 2 (a) The scheme illustrating the sandpaper abrasion test. (b) and (c) Evolution of WCA and WRA (b), and OCA and OSA (c) on the SAP coatings over sandpaper abrasion cycles. The oil for OCA and OSA tests is pump oil. (d)–(g) SEM images of SAP coatings after sandpaper abrasion test for 200 cycles ((d) and (e)), and 700 cycles ((f) and (g)), respectively. (h) The mechanism on persistence of superamphiphobicity upon sandpaper abrasion.

图2展示了超双疏涂层材料的耐磨性能结果及耐磨机制。从图可以看出，超疏水涂层经过500次的砂纸循环打磨后仍然保持良好的超双疏效果。由于涂层独特的梯度结构及乳突状微纳结构，砂纸打磨后部分乳突顶部受损，但暴露出来区域因为仍然具有一定数量的超双疏SiO₂纳米颗粒，使得整个表面仍保持超双疏性能，即涂层优异的耐磨性可归结于构造的独特的梯度结构以及分级的微纳米结构。

Figure 3 Chemical stability ((a)–(d)), UV irradiation stability ((e) and (f)), and thermal stability ((g)–(j)) of the SAP coating. (a) and (b) The evolution of WCA, and WRA (a) and OCA, and OSA (b) of the coated SAP glass slides after having been soaked in solutions of different pH values for 168 h. (c) and (d) Digital photographs displaying that both water and pump oil droplets preserve sphere-like shape on the coatings collected after submersion in extreme corrosion solutions (e.g., pH = 1 and pH = 14 solutions, respectively) for 168 h. (e) and (f) The evolution of WCA, and WRA (e) and OCA, and OSA (f) of the coated SAP glass slides over UV irradiation time. Inset in panel (f) shows the digital photograph of the coating together with water and pump oil droplets after 288 h of UV irradiation. (g) and (h) WCA, and WRA (g) and OCA, and OSA (h) of SAP coating treated at different temperatures for 2 h. (i) and (j) SEM images of the SAP coatings treated at 200 and 350 °C, respectively, for 2 h.

图3展现了超双疏涂层良好的耐紫外、耐温变及耐化学腐蚀性能。超双疏涂层分别在−20 ℃至350 ℃的极端温度下的热处理2 h、288小时连续紫外线辐照、极端腐蚀溶液（pH为1.0和14.0之间的值）中持续浸泡336小时，仍然能够保持良好的超双疏效果。

Figure 4 (a) Experimental measurement curves of leakage current and DC voltage of the various coatings under light pollution environment. Inset provides the enlarge view of the curve regarding SAP and SH coatings. (b) Experimental measurement curves of leakage current and DC voltage of the SAP coating under three levels, namely heavy, medium, and light contamination. (c) The column chart of leakage currents of various specimens as dictated under 10 kV of DC voltage and heavy, medium, and light pollution environment, respectively. (d)–(f) Digital photographs of SAP (d), SH (e), and RTV (f) coatings after contamination by diatomite powders and wetting in the fog chamber.

图4为裸玻璃、超疏水镀膜玻璃及超双疏镀膜玻璃的泄漏电流测试实验，结果表明超双疏涂层具有良好的抑制泄露电流的性能。图4(a)中表明SAP和SH样品的泄露电流随着直流电压升高变化较小，而RTV和疏水样品的泄露电流随着电压的升高而激增。图4(b)表明污染等级越高，污闪电压越高。而图4（d-f）不同样品的数码照片表明，由于SAP涂层具有良好的超疏水性，水滴以球形驻留在表面，而RTV涂层表面水滴会形成连续水膜，这也是SAP样品具有较低泄露电流的原因。

Figure 5 (a) Scheme illustrating the evaluation proposal for pollution flashover upon organic contamination. (b) and (c) The digital photographs of the SH coatings after contamination by different drops of hexadecane and exposing to saturated moisture environment. (d) Experimental measurement curves of leakage current and DC voltage of the SH coating after contamination by hexadecane droplets and diatomite powder.

图5展示了超疏水涂层表面闪络模型及机理示意图，以及超疏水涂层表面在有机物污染后的污闪性能测试结果。图5(d)中可以明显的发现，被十六烷液滴污染的超疏水涂层泄露电流在较低的电压情况下便发生激增，并且随着污染面积的增加，超疏水涂层的防污闪性能随之下降。而SAP涂层由于良好的疏油效果，其表面的润湿行为不会受到十六烷液滴的影响，因此泄露电流基本保持不变。

Figure 6 (a) The PFOVs of various insulators (SAP, SH, H-O, and RTV represent coated SAP, SH, hydrophobic-oleophobic, and RTV-coated glass insulators, respectively). (b) PFOVs of the SAP and RTV glass insulators under light, medium, and heavy pollution grade, respectively. (c) PFOVs of the representative oil-contaminated insulators (i.e., hexadecane droplets). (d)–(f) Digital photographs of the corresponding insulators after contamination by mixture of diatomite and NaCl, followed by exposing to saturated moisture environment. (g) Digital photograph of SH glass insulator contaminated by both simulated contaminants (i.e., mixture of diatomite and NaCl) and oil (i.e., hexadecane drops), followed by exposing to saturated moisture environment for 15 min. (h)–(k) Digital photographs of the various corresponding insulators after pollution flashover tests.

图6为不同种类绝缘子的污闪电压测试结果。图6(a)表明，相较于其他绝缘子，在相同条件下超双疏绝缘子的污闪电压最高。图6(c)表明随着油污染面积的提高，超疏水绝缘子的污闪电压也随之下降。上述结果表明超双疏绝缘子因为具有优异的拒水拒油效果，在电力设备防污闪应用中比超疏水和传统RTV绝缘子具有更远大的前景。

作者简介

武汉理工大学谢毅教授团队长期从事能源与环境功能纳米材料领域的研究工作，主要致力于半导体纳米晶和纳米结构合成及其化学转换、材料表界面修饰及功能薄膜材料（如超浸润薄膜）制备、基于表面等离子体共振的光热转换材料（金属硫族化合物、MXene等）制备及其上述材料在新能源、发光、光催化、自清洁、电力防污闪、防冰除冰、海水淡化等领域的应用研究，并取得了一系列标志性成果。研究成果发表于J. Am. Chem. Soc., ACS Nano, Chem. Mater., Nano Res., ACS Appl. Mater. Interfaces, Nanoscale, J. Colloid. Interf. Sci.等国内外重要学术刊物上。