Recent Advances and Future Prospects of Novel Self-Healing Coating Technologies in Aerospace Applications
Citations
XUE Mingshan, GUO Jingxiao, HONG Zhen, et al. Recent advances and future prospects of novel self-healing coating technologies in aerospace applications[J]. Aeronautical Manufacturing Technology, 2025, 68(18): 48–61.
图1 以自修复和航空航天常用材料Al、Ti合金和碳钢为关键词检索的学术论文数据统计图
图2 多功能微胶囊修复机理[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]
图3 不同质量分数微胶囊用于碳钢板自修复的光学显微镜图像[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]
图4 铝合金表面设计的缓蚀剂型自修复涂层[ XIE C, JIA Y, XUE M S, et al. Anti-corrosion and self-healing behaviors of waterborne polyurethane composite coatings enhanced via chitosan-modified graphene oxide and phosphate intercalated hydrotalcite[J]. Progress in Organic Coatings, 2022, 168: 106881. 30]
图5 微通道自修复机理[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]
图6 纯硅树脂和CG@K–3/3%复合涂层在不同划痕宽度的碳钢板下的光学显微镜图像[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]
图7 镁合金上不同涂层的自修复和防腐机制示意图[ ZHANG J J, WEI J F, LI B C, et al. Long-term corrosion protection for magnesium alloy by two-layer self-healing superamphiphobic coatings based on shape memory polymers and attapulgite [J]. Journal of Colloid Interface Science, 2021, 594: 836–847. 33]
图8 异氰酸酯–恶唑烷微胶囊体系的自修复机制[ LIN Y L, SONG X Y, ZHU C J, et al. Moisture-triggered self-healing of a polyurethane coating based on isocyanate-oxazolidine-loaded microcapsules synthesized via thiol-ene photopolymerization without CO2 release[J]. Progress in Organic Coatings, 2022, 163: 106687. 44]
图9 光诱导自修复过程的表征与分析[ BAI Y K, ZHANG J W, WEN D D, et al. A reconfigurable, self-healing and near infrared light responsive thermoset shape memory polymer[J]. Composites Science and Technology, 2020, 187: 107940. 37]
Recent Advances and Future Prospects of Novel Self-Healing Coating Technologies in Aerospace Applications
XUE Mingshan
GUO Jingxiao
HONG Zhen
YIN Zuozhu
LUO Yidan
XIE Chan
School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang330063, China
Citations
XUE Mingshan, GUO Jingxiao, HONG Zhen, et al. Recent advances and future prospects of novel self-healing coating technologies in aerospace applications[J]. Aeronautical Manufacturing Technology, 2025, 68(18): 48–61.
Abstract
Aerospace equipment such as aircraft, satellites, and space stations are exposed to multi-field coupling environments including extreme temperature fluctuations, atomic oxygen erosion, ultraviolet radiation, and the penetration of local corrosive media (such as Cl–), which can cause mechanical damage and chemical failure of surface protective coatings. Traditional repair methods, due to insufficient precision and poor adaptability to working conditions, are difficult to meet the protection requirements of complex equipment. Self-healing coatings, designed based on biomimetic repair mechanisms, trigger targeted repair responses in damaged areas, providing an innovative solution for extending the lifespan of equipment. This paper systematically introduces the technical characteristics of exogenous and intrinsic self-healing coatings, and focuses on discussing the engineering application breakthroughs of self-healing coatings in typical aerospace environments (such as thermal shock-resistant coatings for engine hot-end components and atomic oxygen-resistant coatings for space station modules) and special working conditions (such as aircraft body protection in high-humidity and high-salt environments at coastal airports). It reveals the cross-scale action mechanism of “damage perception-repair triggering-performance regeneration”, and points out that environment-adaptive repair, in-situ monitoring integration, and multi-mechanism synergy will be the core directions for future development in this field.
航空航天装备长期暴露在极端的服役环境,如海上巡逻机服役于高湿高盐环境;卫星、空间站等面临强紫外线辐射、高速粒子冲击、极端温度波动等。这些装备表面防护涂层易发生机械损伤与化学降解,导致基体材料的加速失效[ ZHANG T Y, ZHANG T, HE Y T, et al. Corrosion and aging of organic aviation coatings: A review[J]. Chinese Journal of Aeronautics, 2023, 36(4): 1–35. 1]。以飞机蒙皮为例,氯离子渗透引发的麻点腐蚀(Pitting corrosion)及涂层剥落导致的鳞落腐蚀(Flake-off corrosion)可显著降低结构完整性,威胁飞行安全[ 杨泽青, 许康妮, 吴江鹏, 等. 飞机机翼表面金属腐蚀识别方法研究进展[J/OL]. 计算机集成制造系统, 2025: 1–37. (2025–02–17). http://kns.cnki.net/KCMS/detail/detail.aspx?filename=JSJJ20250214003&dbname=CJFD&dbcode=CJFQ.YANG Zeqing, XU Kangni, WU Jiangpeng, et al. Research progress on identification methods of metal corrosion on aircraft wing surface[J/OL]. China Industrial Economics, 2025: 1–37. (2025–02–17). http://kns.cnki.net/KCMS/detail/detail.aspx?filename=JSJJ20250214003&dbname=CJFD&dbcode=CJFQ. 2]。传统涂层修复技术(如人工补漆、热喷涂技术等)依赖人工干预,存在3大技术瓶颈:(1)修复层厚度偏差>±25 μm(ASTM D7091标准),形成应力集中源;(2)腐蚀产物残留率>12%(EDAX检测),导致二次腐蚀萌生;(3)单次维护成本高,难以满足现代装备全寿命周期低成本维护需求[ 江海军, 陈力, 苏清风, 等. 激光扫描热波无损检测技术在航空发动机涂层中的应用[J]. 无损检测, 2018, 40(8): 15–19.JIANG Haijun, CHEN Li, SU Qingfeng, et al. Applications of laser scanning thermographic NDT technique in aircraft engine coatings[J]. Nondestructive Testing Technologying, 2018, 40(8): 15–19. 3]。
自修复涂层(Self-healing coatings),作为一种新型的智能材料,通过仿生学设计模拟生物体的损伤自主修复机制,能够在损伤发生后自动或在外界刺激下恢复其原有性能,为解决航空航天装备的修复问题提供了创新思路[ WHITE S R, SOTTOS N R, GEUBELLE P H, et al. Autonomic healing of polymer composites[J]. Nature, 2001, 409(6822): 794–797. 4]。自修复涂层根据修复机制可分为外援型与本征型两大体系(表1)。外援型体系通过预埋修复剂载体(如微胶囊、微脉管)实现损伤触发式修复,其核心依赖于修复剂的局部释放与化学交联[ ZHANG X S, CHEN Y J, HU J L. Recent advances in the development of aerospace materials[J]. Progress in Aerospace Sciences, 2018, 97: 22–34. 5];本征型体系则利用材料内部动态可逆键(共价/非共价键)的分子重构能力,实现多次至无限次修复[ KESSLER M R, SOTTOS N R, WHITE S R. Self-healing structural composite materials[J]. Composites Part A: Applied Science and Manufacturing, 2003, 34(8): 743–753. 6]。两类体系的差异化特征源于其分子设计与环境响应机制的显著区别[ AN S, LEE M W, YARIN A L, et al. A review on corrosion-protective extrinsic self-healing: Comparison of microcapsule-based systems and those based on core-shell vascular networks[J]. Chemical Engineering Journal, 2018, 344: 206–220. 7]。近年来,随着纳米技术、动态化学与微流控技术的交叉融合,自修复涂层在航空航天领域展现出显著的应用潜力。图1是基于2025年3月10日在Web of Science数据库中的以自修复和航空航天常用材料Al、Ti合金和碳钢为关键词检索的学术论文数据统计图,虽然截至目前有关航空航天自修复涂层材料的研究还较少,但是有望成为未来研究的热点领域。例如,TiC层和NiCrAlY层组成的自修复涂层相比普通涂层能显著提高AISI321的抗氧化和抗热冲击性能,铈盐等稀土基缓蚀剂能够在Al、Mg合金上形成致密氧化层,从而达到对基材的长期保护[ LI W, ZHANG C P, ZHU S P, et al. Experimental and modeling investigation of the thermal shock behavior of TiC–based self-healing coatings on AISI 321 stainless steel[J]. Materials & Design, 2024, 246: 113353. 8]。然而,该领域的研究尚处于初始阶段,仍存在许多关键问题有待进一步研究。例如,针对钛合金、镁合金等轻质材料的自修复体系开发不足、动态键的环境稳定性与规模化制备工艺仍需优化[ ZHANG X S, CHEN Y J, HU J L. Recent advances in the development of aerospace materials[J]. Progress in Aerospace Sciences, 2018, 97: 22–34. 5]等。
表1 自修复涂层的分类
Table 1 Classification of self-healing coatings
分类依据
外援型(Extrinsic)
本征型(Intrinsic)
修复机制
通过预埋修复剂(微胶囊/微脉管)释放修复物质
依赖材料内部动态化学键(共价/非共价)可逆重组
触发条件
机械损伤、压力或温度触发容器破裂
热、光、湿度或pH刺激激活动态键重组
修复次数
单次或有限次数(依赖修复剂储量)
多次至无限次(动态键可再生)
应用领域
航空防腐涂层、混凝土裂缝修复
航空防腐涂层、柔性电子封装、可穿戴设备
注:数据来源于Web of Science数据库。
图1 以自修复和航空航天常用材料Al、Ti合金和碳钢为关键词检索的学术论文数据统计图
Fig.1 Statistical chart of academic papers retrieved with keywords of self-healing and Al, Ti alloys and carbon steel commonly used materials in aerospace
微胶囊技术是外援型自修复体系的典型代表,是一种将修复剂包裹在微小胶囊中的技术。其修复机制依赖于机械损伤触发微胶囊破裂,释放封装的修复剂(如环氧树脂、异氰酸酯或缓蚀剂),并通过化学反应(如聚合、交联)填充裂纹或抑制腐蚀[ ZHANG F, JU P F, PAN M Q, et al. Self-healing mechanisms in smart protective coatings: A review[J]. Corrosion Science, 2018, 144: 74–88. 9]。
在航空航天领域,微胶囊自修复技术可以用于卫星太阳能板、飞机液压密封件、飞行起落架等关键部件。微胶囊可以封装多种修复剂来修复损伤,主要分为两大类:填充愈合剂型和填充缓蚀剂型。常见的修复剂包括环氧树脂、聚氨酯、硅烷偶联剂等[ 胡静, 吉翠萍, 卫国英. 基于微胶囊技术的外援型自修复涂层的研究进展[J]. 涂料工业, 2024, 54(9): 64–70.HU Jing, JI Cuiping, WEI Guoying. Research progress on external self-healing coating based on microcapsule technology[J]. Paint & Coatings Industry, 2024, 54(9): 64–70. 10]。其原理是当涂层受到外力或机械损伤时,微胶囊破裂,自修复剂作为芯材释放到受损部位,并在释放后能够与涂层中的活性基团发生化学反应,形成新的交联网络,然后在外部条件下自动修复缺陷[ WHITE S R, SOTTOS N R, GEUBELLE P H, et al. Autonomic healing of polymer composites[J]. Nature, 2001, 409(6822): 794–797. 4]。为了确保修复过程中的有效性,胶囊的外壳必须具有较高的热稳定性和机械性能[ KARTSONAKIS I A, BALASKAS A C, KOUMOULOS E P, et al. ORMOSIL–epoxy coatings with ceramic containers for corrosion protection of magnesium alloys ZK10[J]. Progress in Organic Coatings, 2013, 76(2–3): 459–470. 11]。微胶囊的制备方法主要包括原位聚合法[ LI J Y, SHI H W, LIU F C, et al. Self-healing epoxy coating based on tung oil-containing microcapsules for corrosion protection[J]. Progress in Organic Coatings, 2021, 156: 106236. ADIBZADEH E, MIRABEDINI S M, BEHZADNASAB M, et al. A novel two-component self-healing coating comprising vinyl ester resin-filled microcapsules with prolonged anticorrosion performance[J]. Progress in Organic Coatings, 2021, 154: 106220. 12-13]、界面聚合法[ LI X D, LI X Y, ZHAO Y H, et al. Controllable preparation of isophorone diisocyanate microcapsules with silica/polyurea hybrid shells and application in self-healing epoxy coatings[J]. Progress in Organic Coatings, 2022, 163: 106638. 14]、乳液聚合法[ NUNES F G, BENDINELLI E V, AOKI I V. Microcapsules containing dehydrated castor oil as self-healing agent for smart anticorrosive coatings[J]. Progress in Organic Coatings, 2024, 197: 108863. 15]等。
1.1.1 愈合剂型微胶囊自修复涂层
愈合剂型自修复涂层通过在涂层内部的微胶囊中封装愈合剂实现自修复。当涂层遭受损伤时,微胶囊破裂并释放出愈合剂,这些物质随即在损伤部位发生交联反应,进而对材料进行修复[ WAZARKAR K, PATIL D, RANE A, et al. Microencapsulation: An emerging technique in the modern coating industry[J]. RSC Advances, 2016, 6(108): 106964–106979. 16]。常见的愈合剂有:环氧树脂、桐油及亚麻油等,它们具有优异的成膜性和化学稳定性,能够在损伤处迅速形成连续的薄膜层,有效阻止腐蚀介质的进一步渗透与侵蚀。
在航空航天装备中,机身、机翼、起落架等关键材料,在极端服役环境下,面临着应力腐蚀开裂、点蚀和缝隙腐蚀等问题,严重影响构件的使用寿命[ ZHANG X S, CHEN Y J, HU J L. Recent advances in the development of aerospace materials[J]. Progress in Aerospace Sciences, 2018, 97: 22–34. 5]。尤其是沿海/海上飞行的飞机(如舰载机、海上巡逻机等),长期暴露于高湿盐雾(Cl–质量浓度>5 mg/m3)环境中,导致铝合金蒙皮晶间腐蚀、镁合金起落架电偶腐蚀等[ ZHAO Q Y, GUO C, NIU K K, et al. Long-term corrosion behavior of the 7A85 aluminum alloy in an industrial-marine atmospheric environment[J]. Journal of Materials Research and Technology, 2021, 12: 1350–1359. 17]。传统的涂层难以阻隔空气中的水汽,可能会使水汽透过涂层与修复剂发生反应,导致设备性能退化甚至损毁[ AGNEW L, CLARK B, AVANCE V, et al. Effect of dynamic humidity on environmental cracking of an aerospace aluminum alloy[C]//AMPP Annual Conference+Expo. San Antonio: AMPP, 2022. WILSON W C, ATKINSON G M. Passive wireless sensor applications for NASA’s extreme aeronautical environments[J]. IEEE Sensors Journal, 2014, 14(11): 3745–3753. 18-19]。
基于异氰酸酯对水敏感,易与环境中的水发生反应这一特性,可将异氰酸酯作为自修复材料。异氰酸酯与水接触后通过交联固化实现自修复。在材料制备过程中,只需将微胶囊嵌入基质材料内部,无须额外添加催化剂,避免了催化剂的酸碱性质对微胶囊的破坏,同时防止了自修复溶液与催化剂之间的相互渗透。Li等[ LI C M, TAN J J, GU J W, et al. Rapid and efficient synthesis of isocyanate microcapsules via thiol-ene photopolymerization in Pickering emulsion and its application in self-healing coating[J]. Composites Science and Technology, 2016, 123: 250–258. 20]基于Pickering乳液,通过巯基–烯光聚合将异佛尔酮二异氰酸酯(IPDI)封装于聚硫醚微胶囊中,所制备的微胶囊表现出优异的环境稳定性,在水中浸泡7 d后,核心含量仅下降18%。将含有微胶囊的丙烯酸酯涂层折断以破坏微胶囊,随后将其浸入水中72 h,负载IPDI的微胶囊能够在水中实现自修复。聚硫醚壳层的不耐温性(<80 ℃)限制了它在航空高温部位的应用,相比之下Nunes等[ NUNES F G, BENDINELLI E V, AOKI I V. Microcapsules containing dehydrated castor oil as self-healing agent for smart anticorrosive coatings[J]. Progress in Organic Coatings, 2024, 197: 108863. 15]通过原位乳液聚合技术制备了含脱水蓖麻油(DCO)的聚脲醛–三聚氰胺微胶囊。该微胶囊芯材占比达86%,封装效率达到81%,将微胶囊耐温性提升至230 ℃。当将含15%微胶囊的高固含环氧底漆涂覆于喷砂处理的碳钢基材,并覆盖聚氨酯面漆后,在0.1 mol/L NaCl溶液中浸泡一年,涂层仍保持完整防护性能。在强腐蚀环境中的测试表明,含脱水蓖麻油的微胶囊可为环氧涂层提供持续的自修复保护。此外,将异氰酸酯与环氧树脂混合可形成兼具自修复与防腐蚀功能的多功能微胶囊,其修复机理如图2所示[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]。Li等[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]以IPDI和末端异氰酸酯预聚物(CPU)的杂化物为活性修复剂合成微胶囊,并将其与环氧树脂混合,制备出了具有优异自修复性能的金属防腐涂层,应用于碳钢板的防护。如图3所示[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21],自修复涂层展现出了比纯环氧涂层更优异的自修复能力和抗腐蚀效果。
图2 多功能微胶囊修复机理[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]
Fig.2 Multifunctional microcapsule repair mechanism[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]
图3 不同质量分数微胶囊用于碳钢板自修复的光学显微镜图像[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]
Fig.3 Optical microscope images of self-healing on carbon steel plates with different microcapsule mass fractions[ LI H, WANG X M. Preparation of microcapsules with IPDI monomer and isocyanate prepolymer as self-healing agent and their application in self-healing materials[J]. Polymer, 2022, 262: 125478. 21]
在航空航天装备中,涡轮叶片、燃烧室等高温部件长期暴露于极端高温、氧化环境,其表面防护涂层因热震应力、CMAS熔融沉积及氧扩散等多重作用易发生微裂纹扩展(宽度>50 μm),导致基体材料直接暴露于高温燃气并引发灾难性氧化腐蚀,而传统修复涂层在高温下因有机组分分解等问题难以实现有效自愈。Li等[ LI W, ZHANG C P, ZHU S P, et al. Experimental and modeling investigation of the thermal shock behavior of TiC–based self-healing coatings on AISI 321 stainless steel[J]. Materials & Design, 2024, 246: 113353. 8]制备了TiC层和NiCrAlY层组成的自修复涂层,并将其喷涂在AISI321上,制备的自修复涂层提高了AISI321的抗氧化和抗热冲击性能。与传统的双AT13涂层相比,TiC基自修复涂层的热震寿命提高了57.1%。这是因为TiC层的自修复效应可以显著延迟不同涂层之间界面周围水平裂纹的扩展,从而将涂层的失效模式从整体片状剥落转变为局部/边缘剥落。
影响自修复涂层效果的因素有很多,其中微胶囊的尺寸大小、壳层组分影响最大。合适的微胶囊尺寸有助于修复剂在涂层中的均匀分布及迅速释放。壳层的成分影响着微胶囊的稳定性以及与基材的物理化学相容性。Kosarli等[ KOSARLI M, BEKAS D G, TSIRKA K, et al. Microcapsule-based self-healing materials: Healing efficiency and toughness reduction vs. capsule size[J]. Composites Part B: Engineering, 2019, 171: 78–86. 22]通过原位乳化聚合,合成了受控尺寸并含有环氧树脂修复剂的尿素甲醛(UF)微胶囊,结果表明,随着胶囊尺寸的减小,胶囊在高温(达230 ℃)下保持了良好的热稳定性。此外,愈合效率与胶囊大小成正比,较大的胶囊最高可实现68%的最大负荷恢复。虽然通过使用相对较大的胶囊可以提高愈合效率,但是以牺牲机械性能为代价。Zotiadis等[ ZOTIADIS C, PATRIKALOS I, LOUKAIDOU V, et al. Self-healing coatings based on poly (urea-formaldehyde) microcapsules: In situ polymerization, capsule properties and application[J]. Progress in Organic Coatings, 2021, 161: 106475. 23]则通过原位聚合技术成功制备了含有聚(脲醛)外壳的环氧树脂负载微胶囊。这些微胶囊呈无色自由流动粉末状,半径介于18.5~33 μm之间,具有较好包封效率(高达75%)。壳层的成分也会显著影响涂层与基材的相容性以及涂层的适用性。Liu等[ LIU T H, ZHAO Y Z, DENG Y N, et al. Preparation of fully epoxy resin microcapsules and their application in self-healing epoxy anti-corrosion coatings[J]. Progress in Organic Coatings, 2024, 188: 108247. 24]研发了一种具备耐腐蚀性的新型自修复环氧树脂涂层,合成了平均粒径为43.73 μm、壳厚为3 μm的微胶囊,核心有效含量为59%。制备的微胶囊壁的化学成分与涂层基材基本一致,微胶囊与涂层树脂基体实现了无缝集成,展现出极佳的兼容性。
愈合剂型微胶囊技术通过精准封装(如IPDI@聚硫醚微胶囊[ LI C M, TAN J J, GU J W, et al. Rapid and efficient synthesis of isocyanate microcapsules via thiol-ene photopolymerization in Pickering emulsion and its application in self-healing coating[J]. Composites Science and Technology, 2016, 123: 250–258. 20]),实现了涂层单次损伤的高效修复(效率>80%),但在航空航天应用中仍面临两大局限:高温部件(如发动机叶片)中微胶囊壳层热稳定性不足(耐受<230 ℃);反复机械冲击导致的微胶囊过早破裂(破损率>40%[ ZOTIADIS C, PATRIKALOS I, LOUKAIDOU V, et al. Self-healing coatings based on poly (urea-formaldehyde) microcapsules: In situ polymerization, capsule properties and application[J]. Progress in Organic Coatings, 2021, 161: 106475. 23])。微胶囊在涂层中的分布和破裂行为难以精确调控,可能导致修复不均匀或过度修复等问题。另外,微胶囊的制备成本相对较高,在一定程度上限制了其大规模应用。未来可以开发陶瓷基微胶囊以提升耐温性,并通过梯度壳层设计(内硬外韧)降低非损伤区域的意外破裂风险。
铝合金和镁合金凭借其质量轻、强度高的特点,在航空航天领域广泛应用,但由于化学活性较高,容易发生腐蚀。尽管铝合金会在其表面形成一层致密氧化膜,具有一定防护作用,但难以完全阻止Cl–等腐蚀介质的侵入[ DENG K P, ZHAO G Q, WANG J C. Crevice-galvanic coupling corrosion behavior and mechanism of QC–10 aluminum alloy in chloride-containing solutions[J]. Journal of Materials Science & Technology, 2025, 228: 11–33. 25];镁合金则对潮湿环境表现出高度敏感性。缓蚀剂自修复涂层作用于铝合金与镁合金时,展现出精确腐蚀控制和防护、极端环境适应性以及有效阻断电化学腐蚀进程等优势,使之在轻质合金材料的局部腐蚀防护领域具有重要应用价值。
铈盐等稀土基缓蚀剂主要通过化学吸附于镁、铝等合金表面,形成厚度约为5~20 nm的氧化钝化膜,从而有效阻挡O2、Cl–等腐蚀介质的渗透。Gong等[ GONG Y, GENG J W, HUANG J, et al. Self-healing performance and corrosion resistance of novel CeO2–sealed MAO film on aluminum alloy[J]. Surface and Coatings Technology, 2021, 417: 127208. 26]首次探究了铝合金表面新型CeO2封闭微弧氧化(MAO)膜的自修复性能及其增强的耐腐蚀性。通过对7085铝合金进行微弧氧化处理,获得了平均厚度约为15 μm的多孔MAO膜,随后将MAO样品浸泡于Ce(NO3)3溶液中,使缓蚀剂充满微孔,再对微孔进行封闭处理实现缓蚀剂的负载。涂敷该涂层的铝合金在酸性溶液(pH=2)下,新型CeO2封闭膜展现出形态学上的正向自修复效应。然而,该体系存在工艺复杂、涂层厚度大(15 μm)导致的界面应力集中等问题,在航空薄壁件应用中受到一定的限制。Yang等[ YANG S K, SUN R X, CHEN K Z. Self-healing performance and corrosion resistance of phytic acid/cerium composite coating on microarc-oxidized magnesium alloy[J]. Chemical Engineering Journal, 2022, 428: 131198. 27]以天然无毒的植酸作为中间螯合剂,增强了铈盐颗粒与微弧氧化层之间的结合强度。试验结果显示,所制备的PA/Ce复合涂层厚度约为5 μm,且结构致密、均匀,显著提升了AZ31B基材的耐腐蚀性。此外,该复合涂层还表现出自修复行为,能够为基材提供长期的腐蚀保护。
8–羟基喹啉分子中的羟基(–OH)与含氮环状结构能够与Al3+、Mg2+等金属离子形成稳定的环状配合物,使之在金属表面形成致密的有机–金属复合层,从而阻碍Cl–、O2等腐蚀性物质的渗透。Yang等[ YANG Z Q, WANG L D, ZHANG P J, et al. A multifunctional Sr(HQ)2 filler-reinforced coating for self-healing and physical barrier properties on aluminum alloy[J]. Progress in Organic Coatings, 2023, 180: 107567. 28]合成了锶(Ⅱ)8–羟基喹啉酸酯(Sr(HQ)2),通过化学浴沉积法制备了Sr(HQ)2改性的氟碳(FC)多功能涂层(Sr(HQ)2–FC),实现了对铝合金的长期腐蚀防护。含有2% Sr(HQ)2(质量分数)的FC2–FC涂层与纯FC涂层相较,耐腐蚀性提升了3倍。由于添加了Sr(HQ)2,涂层缺陷区域能通过活性化学蚀刻重新沉积稳定且致密的保护膜,进而赋予涂层有效的自修复功能。试验结果显示,Sr(HQ)2覆盖的铝基板被划伤后,在FC2–FC涂层下的腐蚀速率较纯FC涂层覆盖时降低了一个数量级。该体系的优势在于工艺温度低(<80 ℃),且与铝合金表面氧化层相容性良好,但其耐湿热老化性能受限于氟碳树脂的相分离倾向。Marhamati等[ MARHAMATI F, GHADERI M, HADDADI S A, et al. Nitrogen-doped carbon hollow sphere capsules for a novel hybrid inhibitor based on lanthanum cations and 8–hydroxyquinoline: Synthesis, characterization, and self-healing properties in epoxy coating[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2023, 675: 132065. 29]在低碳钢样品上制备了La.8HQ@NCHS自修复涂层,将La3+阳离子和8–羟基喹啉(8–HQ)封装于氮掺杂碳空心球(NCHS)中,氮掺杂碳空心球(NCHS)的介孔限域效应保障了La3+与8–HQ的协同释放动力学。将La.8HQ@NCHS涂层覆盖在低碳钢上,试验结果表明,低碳钢涂层的耐腐蚀性得到显著提升。羟基喹啉基自修复体系的技术优势与其载体设计密切相关:铝合金体系侧重缓蚀剂/树脂相容性优化;而钢基体系更关注载体导电性与缓蚀剂控释能力的平衡。这种差异化的技术路线为不同服役环境的金属构件防护提供了多元解决方案。
本课题组制备了一种适用于铝合金的智能自修复涂层(图4)[ XIE C, JIA Y, XUE M S, et al. Anti-corrosion and self-healing behaviors of waterborne polyurethane composite coatings enhanced via chitosan-modified graphene oxide and phosphate intercalated hydrotalcite[J]. Progress in Organic Coatings, 2022, 168: 106881. 30]。将壳聚糖、氧化石墨烯和水滑石纳米杂化材料引入水性聚氨酯中,在铝合金表面成功制备出厚度约为40 μm的防腐涂层。其中,水滑石层间的为涂层提供了自修复能力。在NaCl溶液中,Cl–能够置换出水滑石层间的,从而减少腐蚀性离子,降低铝合金的腐蚀速率。释放的与被氧化的Al3+反应,形成AlPO4沉淀物,这些沉淀物进一步溶解形成Al(OH)3薄膜。在碱性环境中,该薄膜能够修复涂层缺陷,实现自修复功能。通过氧化石墨烯和水滑石的堆积形成致密保护层,以及壳聚糖和磷酸根离子的自愈特性,该涂层展现出了优异的防腐性能。
图4 铝合金表面设计的缓蚀剂型自修复涂层[ XIE C, JIA Y, XUE M S, et al. Anti-corrosion and self-healing behaviors of waterborne polyurethane composite coatings enhanced via chitosan-modified graphene oxide and phosphate intercalated hydrotalcite[J]. Progress in Organic Coatings, 2022, 168: 106881. 30]
Fig.4 Corrosion inhibitor-based self-healing coatings on aluminum alloy surfaces: Design and mechanistic insights[ XIE C, JIA Y, XUE M S, et al. Anti-corrosion and self-healing behaviors of waterborne polyurethane composite coatings enhanced via chitosan-modified graphene oxide and phosphate intercalated hydrotalcite[J]. Progress in Organic Coatings, 2022, 168: 106881. 30]
微胶囊型自修复涂层虽能有效提升金属基材的机械性能(如硬度提升20%~30% HV),并实现单次高效修复(愈合率>85%),但其外援型修复机制存在根本性局限:受限于微胶囊芯材封装率上限(典型值≤86%[ AGNEW L, CLARK B, AVANCE V, et al. Effect of dynamic humidity on environmental cracking of an aerospace aluminum alloy[C]//AMPP Annual Conference+Expo. San Antonio: AMPP, 2022. 18]),当损伤区域修复剂(如DCPD单体)释放量达0.8~1.2 μL/mm2后,涂层即丧失持续防护能力。这种单次修复模式与航天器长达15~20年的在轨服役需求存在显著差距。针对该瓶颈,研究团队受生物血管网络启发,开发了仿生微通道技术(图5)[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]。该技术通过激光刻蚀或模板法构筑三维互联微流控网络(管径10~50 μm,孔隙率35%~60%),将修复剂储存在离散腔室(容积0.5~2.0 mL/cm3)中,并利用毛细作用(流速0.1~0.3 mm/s)实现修复剂动态输送[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]。Fu等[ FU X, DU W B, DOU H X, et al. Nanofiber composite coating with self-healing and active anticorrosive performances[J]. ACS Applied Materials & Interfaces, 2021, 13(48): 57880–57892. 32]将静电纺丝与涂层技术相组合,实现了自修复与主动腐蚀抑制的协同保护效果。将聚己内酯(PCL)纳米纤维与负载2–巯基苯并噻唑的埃洛石纳米管(HNTs–MBT)集成,并直接沉积于金属基材表面,形成互连的纤维网络框架。封装的缓蚀剂MBT通过pH响应的方式进行释放,从而实现对基材的腐蚀保护。此外,连续的聚合物纤维在热处理后能够对涂层缺陷进行反复修复,即便经过3个损伤愈合循环,其防腐效率依然有效,修复后的涂层还展现出了持久的防腐性能。
图5 微通道自修复机理[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]
Fig.5 Self-healing mechanism of microchannel-based repair[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]
基于微通道的微管路定向输送机制,愈合剂可被持续输送至损伤界面,理论上该技术即使面对大面积裂纹也能实现有效修复。Liu等[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]研究发现,通过将水溶性铈基缓蚀剂(葡萄糖酸铈)在抑制剂溶液饱和后结合真空干燥循环处理,可将之预储存至木棉纤维中,其负载能力可达455%。凭借纤维的超高负载能力,该体系成功实现了对400 μm级大面积裂纹的自主修复(图6),这一技术路径理论上可拓展至其他类型愈合剂的封装应用中。自修复涂层中均匀分布的纤维构筑了致密的三维网络结构,结合超高负载特性,使涂层展现出优异的耐腐蚀性能。然而,该技术仍需优化三维微血管网络的拓扑结构设计与自密封机制。例如,微通道破裂可能导致修复剂泄漏,需研发具有自修复功能的壁材(如热响应形状记忆聚合物)以提高系统可靠性[ ZHANG J J, WEI J F, LI B C, et al. Long-term corrosion protection for magnesium alloy by two-layer self-healing superamphiphobic coatings based on shape memory polymers and attapulgite [J]. Journal of Colloid Interface Science, 2021, 594: 836–847. 33]。
图6 纯硅树脂和CG@K–3/3%复合涂层在不同划痕宽度的碳钢板下的光学显微镜图像[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]
Fig.6 Optical microscope images of pure silicone resin and CG@K–3/3% composite coatings on carbon steel plates with different scratch widths[ LIU A L, ZHAI Y, FU C H, et al. Self-healing coatings for large-scale damages via ultrahigh load capacity of healing agents in short kapok microtubules[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2024, 693: 134045. 31]
为克服外援型材料的局限性,近期国内外学者也开始聚焦于多功能集成与环境响应型载体设计:第1种是核壳结构纳米容器,例如Marhamati等[ MARHAMATI F, GHADERI M, HADDADI S A, et al. Nitrogen-doped carbon hollow sphere capsules for a novel hybrid inhibitor based on lanthanum cations and 8–hydroxyquinoline: Synthesis, characterization, and self-healing properties in epoxy coating[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2023, 675: 132065. 29]开发了氮掺杂碳空心球(NCHS)封装La3+与8–羟基喹啉,在环氧涂层中实现缓蚀剂可控释放,使低碳钢的腐蚀电流密度降低了2个数量级;第2种是刺激响应型载体,例如Xie等[ XIE C, JIA Y, XUE M S, et al. Anti-corrosion and self-healing behaviors of waterborne polyurethane composite coatings enhanced via chitosan-modified graphene oxide and phosphate intercalated hydrotalcite[J]. Progress in Organic Coatings, 2022, 168: 106881. 30]将氧化石墨烯(GO)与水滑石纳米片引入水性聚氨酯,利用Cl–触发释放,与Al3+形成AlPO4钝化膜,使铝合金盐雾测试耐蚀性提升了3倍。Huang等[ HUANG J F, FAN H W, SHEN X T, et al. Temperature-responsive self-healing coating with excellent resistances to oxidation and thermal shock from core-shell SiB6@Al2O3 microcapsule[J]. Ceramics International, 2025, 51(9): 12243–12252. 34]为提高碳/碳(C/C)复合材料在中等温度下的抗氧化性,提出了一种新的抗氧化涂层设计概念。该涂层采用了专为自修复和原位增韧而设计的陶瓷微胶囊。这些微胶囊具有SiB6@Al2O3核壳结构,在1573 K的氧化环境中暴露540 h后,涂层表现出良好的抗氧化性。
表2对比了外援型类(微胶囊与微通道)修复技术的主要差异。微胶囊技术凭借成熟的封装工艺(如原位聚合[ NUNES F G, BENDINELLI E V, AOKI I V. Microcapsules containing dehydrated castor oil as self-healing agent for smart anticorrosive coatings[J]. Progress in Organic Coatings, 2024, 197: 108863. 15])已实现工程化应用(如飞机蒙皮修复[ LI C M, TAN J J, GU J W, et al. Rapid and efficient synthesis of isocyanate microcapsules via thiol-ene photopolymerization in Pickering emulsion and its application in self-healing coating[J]. Composites Science and Technology, 2016, 123: 250–258. 20]),但其单次修复特性(修复剂储量≤90%)限制了其在重复损伤场景(如空间站微陨石撞击)中的适用性。微通道技术则通过仿生血管网络设计,将修复剂负载量提升至455%[ AN S, LEE M W, YARIN A L, et al. A review on corrosion-protective extrinsic self-healing: Comparison of microcapsule-based systems and those based on core-shell vascular networks[J]. Chemical Engineering Journal, 2018, 344: 206–220. 7],并可动态补给,但其管道拓扑优化与泄漏抑制仍需突破。未来研究可以结合两种技术的优势:利用微胶囊实现快速修复(<24 h),通过微通道网络补充修复剂,构建分级响应体系。
表2 微胶囊与微管道技术对比
Table 2 Comparative analysis of microencapsulation vs. microchannel technologies
(1)动态共价键体系。通过可逆化学反应(如Diels–Alder(DA)反应、二硫键交换)实现损伤界面的分子重组,可通过热、光或化学对修复效率进行调控。例如,Diels–Alder键在加热(>100 ℃)下可逆解离为呋喃与马来酰亚胺单体,冷却后重新键合,适用于热触发修复。Chen等[ CHEN T Q, FANG L, LI X, et al. Self-healing polymer coatings of polyurea-urethane/epoxy blends with reversible and dynamic bonds[J]. Progress in Organic Coatings, 2020, 147: 105876. 35]将呋喃功能化环氧低聚物与双马来酰亚胺(BMI)共混,通过DA反应形成动态网络。在120 ℃下,涂层划痕(50 μm)在2 h内愈合,修复效率达90%,且循环修复5次后仍保持80%的力学强度。Zhang等[ ZHANG J J, WEI J F, LI B C, et al. Long-term corrosion protection for magnesium alloy by two-layer self-healing superamphiphobic coatings based on shape memory polymers and attapulgite [J]. Journal of Colloid Interface Science, 2021, 594: 836–847. 33]在镁合金表面涂覆DA键修饰的聚氨酯/凹凸棒石复合涂层,在150 ℃下触发修复,盐雾测试(5% NaCl)中耐蚀性提升4倍,服役寿命延长至54 d。二硫键(S—S)通过硫醇–二硫交换或自由基重组实现修复,适用于湿热环境。Qiu等[ QIU X L, LI C P, SUN Y C, et al. Study on anticorrosion and wear resistance of self-healing coating based on functional MXene and dynamic disulfide bond[J]. ACS Applied Polymer Materials, 2024, 6(18): 11392–11405. 36]开发了含有动态二硫键的自修复环氧树脂,在170 ℃加热 10 min 的条件下,涂层的自修复性能得到显著提高,在0.01 Hz超低频下的阻抗模值|Z|0.01 Hz从6.77×106 Ω·cm2提升至1.54×108 Ω·cm2。Bai等[ BAI Y K, ZHANG J W, WEN D D, et al. A reconfigurable, self-healing and near infrared light responsive thermoset shape memory polymer[J]. Composites Science and Technology, 2020, 187: 107940. 37]将氧化石墨烯(GO)掺杂于聚氨酯,利用GO的光热效应(1.4 W/cm2近红外光)触发二硫键重组,修复效率达95%,且适用于航天器蒙皮的真空热环境。
(2)非共价键体系。非共价键(如氢键、金属配位、π–π堆积)通过物理相互作用实现分子链动态重组,具有室温修复与快速响应优势。氢键的断裂与重组可通过湿度或机械能触发。Nardeli等[ NARDELI J V, FUGIVARA C S, TARYBA M, et al. Self-healing ability based on hydrogen bonds in organic coatings for corrosion protection of AA1200[J]. Corrosion Science, 2020, 177: 108984. 38]制备了源自植物油的生物基聚氨酯涂料,并将其应用于AA1200铝合金上,利用其氢键以赋予防腐蚀保护。在高湿度环境下,Lin等[ LIN B, WANG J X, ZHANG H L, et al. Self-healing performance of ethyl-cellulose based supramolecular gel coating highly loaded with different carbon chain length imidazoline inhibitors in NaCl corrosion medium[J]. Corrosion Science, 2022, 197: 110084. 39]将咪唑类离子液体引入聚氨酯,利用其吸湿性增强氢键迁移能力,使涂层在85%湿度下的修复时间缩短至12 h。金属离子(如Fe3+、Cu2+)与配体(如羧酸、吡啶)的动态配位可实现光/热响应修复。Sheng等[ SHENG Y M, WANG M H, ZHANG K P, et al. An “inner soft external hard”, scratch-resistant, self-healing waterborne poly (urethane-urea) coating based on gradient metal coordination structure[J]. Chemical Engineering Journal, 2021, 426: 131883. 40]开发了一种耐刮擦和修复的聚氨基甲酸乙基–尿素水性涂料,通过使用离子渗透的方法包含Zn(Ⅱ)–羧基和Zn(Ⅱ)–二亚胺吡啶的双重金属配位结构。锌离子的添加使涂层表面形成了致密的金属配位键,大大提高了表面硬度和耐刮擦性,此外,该涂层表现出优异的自修复性能,在湿热条件下修复能力更好。Ye等[ YE Y W, CHEN H, ZOU Y J, et al. Study on self-healing and corrosion resistance behaviors of functionalized carbon dot-intercalated graphene-based waterborne epoxy coating[J]. Journal of Materials Science & Technology, 2021, 67: 226–236. 41]从柠檬酸衍生物中获得的功能化碳点(CDs)作为插层剂对石墨烯进行改性,制备了CDs改性石墨烯/环氧树脂(CDs–G/EP)涂层。功能化碳点和石墨烯之间形成了“π–π”相互作用,CDs增强了石墨烯的分散性和界面兼容性,有效增强了涂层的自修复能力和防腐能力。
在航空航天领域,低温高湿环境引发的结冰与冷凝问题严重威胁装备可靠性,机翼前缘在飞行中易形成冰层积聚,载人航天器舱内温湿度波动则导致金属表面产生冷凝液。对此,金属基材的超疏水表面处理技术展现出独特优势。通过构建接触角>150°的微观粗糙结构,可有效减少雨水/冷凝液滞留(接触时间缩短至0.3~0.5 s),显著降低蒙皮腐蚀风险。该技术尤其适用于高盐雾环境服役的装备(如舰载机、沿海部署飞机),其超疏水涂层还可为舱内电子设备外壳提供主动防护[ LYNCH F T, KHODADOUST A. Effects of ice accretions on aircraft aerodynamics[J]. Progress in Aerospace Sciences, 2001, 37(8): 669–767. 42]。针对镁合金腐蚀防护需求,Zhang等[ ZHANG J J, WEI J F, LI B C, et al. Long-term corrosion protection for magnesium alloy by two-layer self-healing superamphiphobic coatings based on shape memory polymers and attapulgite [J]. Journal of Colloid Interface Science, 2021, 594: 836–847. 33]开发了具有双层结构的智能自修复超疏水涂层,结构示意见图7。该体系底层为SMP基复合层,负载缓蚀剂1,2,3–苯并三唑(BTA)和陶瓷蜡微粒(粒径2~5 μm);顶层为凹凸棒土构筑的超疏水功能层(表面粗糙度Ra=1.8 μm)。试验表明,这种仿生双层结构在3.5% NaCl溶液中浸泡80 d后,涂层阻抗模值仍保持在106 Ω·cm2以上;经5% NaCl盐雾环境54 d加速腐蚀测试,镁合金基体未出现点蚀扩展现象。其卓越的耐久性源于双重自修复机制:温度触发SMP层形状恢复(回复率>92%)封闭微裂纹,BTA缓蚀剂持续释放形成钝化膜。
图7 镁合金上不同涂层的自修复和防腐机制示意图[ ZHANG J J, WEI J F, LI B C, et al. Long-term corrosion protection for magnesium alloy by two-layer self-healing superamphiphobic coatings based on shape memory polymers and attapulgite [J]. Journal of Colloid Interface Science, 2021, 594: 836–847. 33]
Fig.7 Schematic illustration of self-healing and anti-corrosion mechanisms of different coatings on Mg alloys[ ZHANG J J, WEI J F, LI B C, et al. Long-term corrosion protection for magnesium alloy by two-layer self-healing superamphiphobic coatings based on shape memory polymers and attapulgite [J]. Journal of Colloid Interface Science, 2021, 594: 836–847. 33]
形状记忆聚合物亦可通过光触发来实现自修复性能。Wang等[ WANG B Y, LIU J, LIU M, et al. Preparation and corrosion resistance of shape memory self-healing coatings responsive to near-infrared light[J]. Polymer Testing, 2023, 126: 108146. 43]采用环氧树脂(EP)作为形状记忆基质,GO–CL/PPy聚合物复合材料作为光热转换剂,制备了一种近红外光响应的形状记忆自修复涂层。研究结果表明,在表面活性剂与吡咯的质量比为2∶1且聚合时间为5 h的条件下,聚吡咯的性能达到了最优。将GO–PCL/PPy聚合物掺入环氧树脂复合材料中,显著提升了整个涂层的导热性能。当聚合物质量分数为7%时,观察到对环氧树脂的光热转换效果最佳,使得复合材料的形状恢复率达到了66.67%。此外,该涂层还展现出了优异的自修复性能,划痕愈合效率高达80%。
针对航天器在近地轨道服役时面临的极端环境条件(–180~150 ℃剧烈温变、原子氧通量>1015 atoms/(cm2·s)),Chen等[ CHEN T Q, FANG L, LI X, et al. Self-healing polymer coatings of polyurea-urethane/epoxy blends with reversible and dynamic bonds[J]. Progress in Organic Coatings, 2020, 147: 105876. 35]通过分子设计构建聚脲–氨基甲酸酯/环氧树脂复合涂层体系,该体系创新性地在聚脲–氨基甲酸酯基体、环氧树脂相及其界面区域引入动态可逆键网络。首先,合成含动态二硫键的呋喃封端热塑性聚脲–氨基甲酸酯(FTPU),再与带有悬垂呋喃基团的环氧低聚物共混。利用双(4–马来酰亚胺基)甲烷(BMI)的马来酰亚胺基团与环氧低聚物呋喃基团间的DA可逆反应,诱导形成微相分离结构,使涂层储能模量提升至1.2 GPa(提升约40%)。试验表明,该体系在冷拔条件下实现91%的形状固定率,经80 ℃热处理后恢复率高达99%。其优异的裂纹愈合能力来源于双重动态机制:(1)FTPU内部的二硫键(S—S键能≈268 kJ/mol)可逆重组;(2)相界面DA键(解离温度≈120 ℃)的热响应重构。
Lin等[ LIN Y L, SONG X Y, ZHU C J, et al. Moisture-triggered self-healing of a polyurethane coating based on isocyanate-oxazolidine-loaded microcapsules synthesized via thiol-ene photopolymerization without CO2 release[J]. Progress in Organic Coatings, 2022, 163: 106687. 44]开发了一种基于异氰酸酯–噁唑烷复合微胶囊的湿度响应型自修复体系(图8)。该研究采用界面光引发巯基–烯点击化学法,在稳定水相乳液中合成了具有核壳结构的球形微胶囊,其壳层厚度为(10±1.2) μm,中值直径达151.4 μm(PDI=0.18)。微胶囊内核封装异氰酸酯与噁唑烷化合物,其中噁唑烷的引入使微胶囊热分解温度提升至280 ℃(较纯异氰酸酯体系提高62 ℃)。其自修复机制分为3个阶段:(1)环境湿度>60%时,噁唑烷优先发生开环反应生成氨基/羟基化合物;(2)活化产物触发异氰酸酯固化反应;(3)修复剂通过壳层微孔扩散至损伤界面完成修复。该体系也存在显著局限性:在湿度<40%环境下修复效率降至43%(ASTM D714标准),且微胶囊厚壳层导致修复剂释放速率常数k仅为0.03 h–1(25 ℃),难以满足干冷地区(湿度30%~50%,温度–20~10 ℃)的工程需求。相比之下,Yu等[ YU K, ZHANG Y J, OUYANG H, et al. Degradable, self-healing, humidity-driven poly (urethane-urea) film[J]. Polymer, 2024, 308: 127358. 45]设计的湿度驱动型聚乙烯(聚氨酯–尿素)材料PUU–DHA–Cu4突破了传统限制。该材料通过引入硼–氧动态共价键(B—O键能≈523 kJ/mol),在室温下实现三重特性耦合:(1)自修复效率达90.1%(48 h,ASTM D638标准);(2)初始拉伸强度25.7 MPa(与商用聚氨酯相当);(3)酸性环境快速降解(0.1 M HCl/THF溶液,4 h降解率>95%)。这种性能平衡源于分子设计:动态硼酸酯键赋予材料室温自修复能力,而Cu2+–羧酸配位作用(结合常数logK=8.2)增强机械强度。研究同时也揭示了湿度敏感性带来的共性难题——当环境湿度从30%增至80%时,材料自修复效率波动幅度达47%,且吸湿性组分加速老化(湿热老化500 h后强度保持率仅62%)。两类研究共同暴露了湿度响应型自修复材料的核心矛盾:环境湿度既是修复动力源(活化能来源),也是性能退化诱因(水解敏感键断裂)。现有技术难以精准调控湿度窗口(理想工作区间需控制在55%~75% RH),且吸湿性组分(如PUU–DHA–Cu4中的羟乙基丙烯酰胺)易引发涂层膨胀应力(ΔV达7.3%),导致界面剥离失效,极大限制了该类材料在温湿度剧烈波动环境(如近海大气、高原机场)的适用性。
图8 异氰酸酯–恶唑烷微胶囊体系的自修复机制[ LIN Y L, SONG X Y, ZHU C J, et al. Moisture-triggered self-healing of a polyurethane coating based on isocyanate-oxazolidine-loaded microcapsules synthesized via thiol-ene photopolymerization without CO2 release[J]. Progress in Organic Coatings, 2022, 163: 106687. 44]
Fig.8 Self-healing mechanism of isocyanate-oxazolidine-loaded microcapsules system[ LIN Y L, SONG X Y, ZHU C J, et al. Moisture-triggered self-healing of a polyurethane coating based on isocyanate-oxazolidine-loaded microcapsules synthesized via thiol-ene photopolymerization without CO2 release[J]. Progress in Organic Coatings, 2022, 163: 106687. 44]
航天器在深空探测中面临三重严苛挑战:(1)高真空环境(<10–6 Pa)削弱传统修复剂扩散动力学;(2)剧烈温变(–170~150 ℃/h)引发涂层界面应力积累;(3)强辐射(UV通量>300 W/m2)加速材料老化。传统湿度响应型涂层在此类环境完全失效,促使学界转向光响应型自修复技术——利用太空富集的光能(如太阳辐照度1361 W/m2)驱动修复过程。如图9所示,Bai等[ BAI Y K, ZHANG J W, WEN D D, et al. A reconfigurable, self-healing and near infrared light responsive thermoset shape memory polymer[J]. Composites Science and Technology, 2020, 187: 107940. 37]创新性地将氧化石墨烯(GO,光热转换效率达68%)掺入热固性聚氨酯基体,构筑出多模态光响应复合材料。该体系在1.4 W/cm2可见光辐照下,GO纳米片产生局部焦耳热(ΔT≈120 ℃),触发氨基甲酸酯动态键交换反应,实现95%的形状恢复率(ASTM D3029标准);当光强升至2.5 W/cm2时,材料同时展现出光诱导可塑性(储能模量下降76%)与自修复能力(微裂纹愈合率>90%)。这种光–热–力多场耦合效应,为卫星在轨紫外辐照(254~365 nm,5~12 SUNs)与再入大气热冲击(>800 ℃/min)协同作用下的原位修复提供了新模式。Hou等[ HOU Y C, WENG D, YU Y D, et al. Near infrared light responsive surface with self-healing superhydrophobicity in surface chemistry and microstructure[J]. Applied Surface Science, 2022, 598: 153772. 46]在此基础上引入近红外响应(808 nm)技术,开发出了具有双重复位机制的疏水自修复表面:(1)形状记忆环氧树脂(Tg=85 ℃)在NIR辐照(1.8 W/cm2,30 s)下恢复微观结构(接触角从112°回升至162°);(2)同步激活微胶囊(壳厚15 μm)释放氟化烷基硅烷(表面能降至12.3 mN/m)。试验表明,该表面经历5次损伤–修复循环后,疏水性能保持率仍达93%,且修复响应时间较传统热触发体系缩短87%。其耐久性源于SMP的精确相变设计(应变固定率98%)与氟硅烷梯度释放动力学(k=0.15 h–1)的协同作用。相较于传统体系,光控自修复技术凸显3大太空适应性优势:(1)能量来源匹配性。直接利用太空富集光能,避免附加能源负载;(2)修复精度可控性。通过调制光强(0.5~3 W/cm2)与波长(405~980 nm)实现毫米级定位修复;(3)环境抗干扰性。真空环境反而增强光热转换效率(较常压提升22%)。
图9 光诱导自修复过程的表征与分析[ BAI Y K, ZHANG J W, WEN D D, et al. A reconfigurable, self-healing and near infrared light responsive thermoset shape memory polymer[J]. Composites Science and Technology, 2020, 187: 107940. 37]
Fig.9 Characterization and analysis of the light-induced healing process[ BAI Y K, ZHANG J W, WEN D D, et al. A reconfigurable, self-healing and near infrared light responsive thermoset shape memory polymer[J]. Composites Science and Technology, 2020, 187: 107940. 37]
除近红外波段外,蓝光(450~495 nm)因其高光子能量(2.5~2.75 eV)逐渐成为光控自修复涂层的新型触发源。Zhu等[ ZHU Y Y, LIU M D, CHEN M, et al. Synthesis of blue light-responsive microspheres for autonomous self-healing coatings[J]. Chemical Engineering Journal, 2022, 450: 138306. 47]创新性地构建了蓝光响应型微球系统,其技术核心在于:(1)聚合物外壳主链嵌入蒽衍生物光敏单元,在30 mW/cm2蓝光辐照下产生高密度自由基(浓度达1018 cm–3);(2)微球内部封装阻聚剂(如BHT)与愈合剂双组分体系。当光生自由基被阻聚剂不可逆淬灭后,系统通过微球可控塌陷(塌陷率>85%)实现修复剂精准释放。该机制在60~80 ℃温和条件下即可完成修复(较传统热触发体系温度降低40~60 ℃),且兼容金属、陶瓷、聚合物等基材,标志着光响应涂层从强刺激(>1 W/cm2)向弱刺激(<100 mW/cm2)范式的技术跨越。
针对湿度/光协同触发体系等多元响应系统[ HOU Y C, WENG D, YU Y D, et al. Near infrared light responsive surface with self-healing superhydrophobicity in surface chemistry and microstructure[J]. Applied Surface Science, 2022, 598: 153772. 46],研究揭示其面临双重技术瓶颈:(1)信号耦合干扰。在相对湿度>80%环境下,水分子对光波的散射作用使光热转换效率衰减达47%(λ=808 nm),导致修复剂释放动力学常数k下降至0.08 h–1。(2)经济性制约。智能材料原料成本占比高达68%(如形状记忆聚酰亚胺单价>320美元/kg)。突破路径包括:(1)开发生物基动态聚合物(如木质素改性聚氨酯,成本可降低至45/kg);(2)构建正交响应机制,通过波长选择(如可见光控形变+微波控释放)实现信号解耦,使双刺激体系修复效率波动率从±32%压缩至±8%。
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