热障涂层高温失效的研究进展

热障涂层的高温失效问题是热障涂层材料研究的重要命题,本文对国内外学者在热障涂层高温失效试验、失效机制、失效的动态监测和寿命预测方面的研究进展进行了综述。热障涂层的失效主要源自涂层中存在的热生长氧化物(TGO)的失效,文中总结出了国内外学者对TGO研究的几个重点方面,以期为热障涂层的高温失效问题提供研究思路。     

陶瓷基复合材料用环境障涂层专利分析研究

本文以环境障涂层专利数据为基础,从趋势、技术、地域、申请人四个维度研究分析了环境障涂层技术的发展过程和现状。分析结果表明：在发展趋势方面环境障涂层正处于较为活跃的研究发展阶段,并且随着陶瓷基复合材料的应用还将具有较为广阔的研究发展空间;在技术构成方面陶瓷涂层材料、制备工艺和应用领域是环境障涂层最主要的研究领域,并且从2014年开始环境障涂层逐渐成为国内外研究的热点;在地域分布方面环境障涂层技术的技术主导国是中国和美国,国外在材料、结构、工艺、应用等多个领域均有专利申请和布局,并且对于环境障涂层在航空发动机的应用更为关注,而中国目前主要集中于陶瓷涂层材料等基础研究领域;在申请人方面,国外申请人主要集中在GE、R-R等主流航空发动机公司,而国内主要集中在高校和研究院所,对环境障涂层技术持续研究和创新缺乏合理的规划,同时申请专利的质量还有待进一步提升。     

Topcoat thickness measurement of thermal barrier coating using grating laser acoustic spectrum method

The thickness of top coating is a crucial factor to characterize the performance of thermal barrier coating. Aiming at the difficulty of thickness measurement with conventional ultrasonic method, a noncontact method based on grating laser ultrasonic acoustic spectrum is proposed. Firstly, the dispersion curve of surface acoustic waves in thermal barrier coating was obtained. The numerical simulation of the established three-layer media model based on finite element method was then performed. Experiments with thermal barrier coating specimens in different thicknesses of top coating were conducted. The theoretical results and simulative results were corrected by ultrasound attenuation theory to fit experimental results. It is found that experimental results show great agreement with the theoretical curve and numerical simulation results after correction, which illustrates the usefulness and potential of the proposed method when applied to the thickness measurement of top coating in service.     

Diffusion cell investigations into the acidic degradation of organic coatings

Protective organic coatings work by preventing contact between an aggressive environment and a vulnerable substrate. However, the long required lifetime of a barrier coating provides a challenge when attempting to evaluate coating performance. Diffusion cells can be used as a tool to estimate coating barrier properties and lifetime. In this work, a diffusion cell array was designed, constructed, and compared to previous designs, with simplicity being the most important design parameter. Sulfuric acid diffusion through five different coatings was monitored using a battery of cells, and a mathematical model was developed to simulate the experimental data and to study diffusion mechanisms. The diffusion cells allowed an objective and fast analysis of coating barrier properties. It was found that sulfuric acid deteriorated these properties as it diffused through the films. This was also expressed in the modeling results, where a three-step time dependency of the diffusion coefficient was required to simulate both acid breakthrough time and the subsequent steady-state flux. A vinyl ester-based coating proved to be the most effective barrier to sulfuric acid diffusion, followed by a polyurethane coating. Amine-cured novolac epoxies provided the least effective protection.     

复合外墙隔热涂料的制备和隔热性能研究

制备了2类复合外墙隔热涂料,一类是将反射型、辐射型、阻隔型3种功能填料按一定比例复合配制外墙隔热涂料;另一类是分别制备反射、辐射、阻隔涂层,并将这3种涂层按2种方式叠加复合,构成外墙隔热涂层。3种功能填料复合涂层在红外灯照射下的绝对温升为27.4℃,在波长为250~2 500 nm范围内的太阳反射比为87%,半球发射率为89%;在太阳光照射下,功能填料复合涂层的热箱内最高温度分别比未涂覆的空石棉板、空白样、叠加复合涂层、单涂反射涂层、单涂辐射涂层和单涂阻隔涂层低11.0℃、5.5℃、0.9℃、2.1℃、3.8℃和1.2℃。研究结果表明:将3种功能填料以一定比例复合配制的涂层隔热效果优于3种隔热机理涂层叠加而得的复合涂层,更优于单一隔热机理涂层。     

防扩散镀层的新工艺方向

镀金制品采用镀镍防扩散层可以防止底层的铜与金层的相互扩散。西欧国家对与人体直接接触的金属消费品规定了镍释出率和标准，因而提出代镍的防扩散层工艺。     

Barrier and mechanical properties of biodegradable poly(ε‐caprolactone)/cellophane multilayer film

In this study, cellophane (PT) multilayer films were prepared by coating with different thickness of poly(ε‐caprolactone) (PCL) and chitosan (CH), and its effects on barrier and mechanical properties were evaluated. It was shown that the PCL/PT/PCL and PCL/CH/PT/CH/PCL multilayer films exhibit much better water vapor barrier than PT, and these films still keep the high oxygen barrier. And the barrier properties of multilayer film were improved with the increase of the thickness of coating materials. The Young's modulus and tensile strength of PT multilayer film were slightly decreased, and their elongations at break were increased by coating. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1805–1811, 2013     

Thermal shock resistance of air plasma sprayed thermal barrier coatings

The spallation resistance of an air plasma sprayed (APS) thermal barrier coating (TBC) to cool-down/reheat is evaluated for a pre-existing delamination crack. The delamination emanates from a vertical crack through the coating and resides at the interface between coating and underlying thermally grown oxide layer (TGO). The coating progressively sinters during engine operation, and this leads to a depth-dependent increase in modulus. Following high temperature exposure, the coating is subjected to a cooling/reheating cycle representative of engine shut-down and start-up. The interfacial stress intensity factors are calculated for the delamination crack over this thermal cycle and are compared with the mode-dependent fracture toughness of the interface between sintered APS and TGO. The study reveals the role played by microstructural evolution during sintering in dictating the spallation life of the thermal barrier coating, and also describes a test method for the measurement of delamination toughness of a thin coating.     

舰船新型涂料的研究进展

介绍了新型船舶涂料的种类。综述了船舶用防污涂料、船体防锈涂料和舰用特种功能涂料包括吸波涂料、纳米隐身涂料和其它新型涂料(防滑涂层、潜艇特征信号控制涂层、新型光触媒涂料、新型室温可逆变色涂料、新型热防护涂料、热障涂层和溶胶-凝胶涂层等)的性能和研究状况。指出了其发展趋势。     

Optimization of hybrid sol–gel coatings by combination of layers with complementary properties for corrosion protection of AA2024

The coating system usually employed for corrosion protection of metal substrates consists of different layers which can be constituted of a chemical conversion coating applied on the metal surface followed by a number of organic layers. Hybrid films prepared by the sol–gel method provide a good approach as protective layers on metallic surfaces, although it is necessary to combine the barrier functionality with an active protection mechanism to avoid corrosion when the coating is damaged. Previous works have shown that it is very difficult to reach this result in a mono-layer sol–gel because the amount of inhibitors incorporated tends to increase significantly the porosity of the coating and reduces drastically the barrier properties. This work presents the characterization of a multi-layer sol–gel hybrid inorganic–organic coating system with a structure composed of an intermediate cerium inhibited layer deposited between two un-doped layers on AA2024 alloy. The comparison between the inhibited system and a bi-layer non-inhibited one has allowed to assess the migration of the cerium ions into the hybrid coating towards the substrate corresponding to the improvement of the corrosion properties. The combination of the physical barrier and the active protection enables to obtain an effective protective system.     

Preparation and barrier property of poly(vinyl alcohol)/SiO<Subscript>2</Subscript> hybrid coating films

Using sol-gel method, poly(vinyl alcohol)/SiO₂ hybrid coating materials with an improved gas barrier property could be produced. Phase compatibility between organic PVA segments and inorganic silicate network in the hybrid was evaluated by analyzing FT-IR spectra and investigating the crystallization behavior in terms of X-ray diffraction patterns for the hybrid gels. For the preparation of coating film with barrier property, the biaxially oriented polypropylene (BOPP) substrate was coated with the hybrid sols by a spin coating method. Morphological analysis for the fractured surface of the hybrid gel and the surface of the coated film was performed not only to examine the microstructure of the hybrid, but also to propose evidence for the oxygen permeation behavior through the coated film. It was revealed that an optimum amount of inorganic silicate precursor, TEOS, should be used to obtain high barrier PVA/SiO₂ hybrid coating materials with enhanced micro-phase morphology and optical transparency. This homogeneous morphology densified with nano-structured silicate, obtained at optimal conditions, was found to result in a significant increase in the oxygen barrier property of film coated with PVA/SiO₂ hybrid by about 50 times relative to the pure BOPP substrate. In addition, the effect of pretreatments of the BOPP substrate surface on the barrier property was also examined.     

Fabrication of cellulose nanofiber‐based ultrafiltration membranes by spray coating approach

Ultrafiltration membranes containing a cellulose nanofiber barrier layer were fabricated by the spray coating method, where the thickness and uniformity of the barrier layer were systematically investigated as a function of air pressure, flow rate and concentration of the cellulose nanofiber suspension. In specific, the surface morphology of the barrier layer was studied by scanning electron microscopy and its uniformity was examined by the fluorescence dye imaging method. The ultrafiltration performance of the membranes fabricated by the spray coating method was also compared with that of the membranes made by the knife coating approach using dextran molecules as probe, where the former consistently exhibited significantly higher permeation flux while remaining the same rejection ratio. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44583.     

陶瓷基复合材料的界面相容性研究

有关陶瓷基复合材料（CMC）的界面问题已经得到广泛的重视。为了使材料达到一个很好的刚性，在纤维与基体之间保持尽量小的界面作用力对于陶瓷纤维增强Si-C-O复合材料是非常重要的。在纤维界面上涂层有利于减小它们之间相互作用，涂层处理后的Si-C-O复合材料的弯曲强度比一般无涂层的复合材料高5倍。在介质涂层、基体、以及涂层与纤维间的三相物质中避免化学反应的发生。目前，可利用化学相容性的原理对涂层纤维进行选择。     

Semiquantitative method for the evaluation of grease barrier coatings

Many tests are known for testing the grease barrier performance of coatings in paper or paperboard. Some are manifested in standard procedures such as TAPPI, ASTM, or ISO, but as many procedures were developed and modified by companies and research groups. Mainly the test methods are based on visually detecting the amount of oil, which is in most cases dyed for better contrast, penetrating through the coating, meaning the procedures are based on a subjective visual evaluation and thus often not linked for instance to a statistical meaningful physical value. We found that by using a slightly modified ASTM D 722 test the L*a*b* color coordinates determined with a commercial handheld spectrophotometer are related to the grease barrier performance of an organic coating. By applying this new method the penetration time of an oil/dye mixture could be correlated to the lightness L* and chromaticity b* and fitted by an exponential function. Furthermore, the coating was slightly modified and an improvement or worsening of the grease barrier could be detected clearly outside of the statistical scatter of a control series. We call this method semiquantitative, since the level of grease barrier of a coating is not measured directly by a quantitative value, but color coordinates are correlated in a series to the effectiveness of the grease barrier.     

新型PVC片材的力学性能和阻隔性能的研究

采用微层挤出技术制备了微层PVC片材,采用涂覆法制备了多层PVC/PVA复合片材,对其力学性能和阻隔性能进行了研究。结果表明:①多层结构有利于提高PVC/PVA复合片材的阻隔性能,涂覆PVA溶液增大了片材的拉伸强度。②微层PVC片材的分子链发生取向,沿挤出方向的拉伸强度明显高于垂直挤出方向;微层PVC片材的层数越多,取向作用越强,越有利于阻隔性能的提高。     

聚偏氯乙烯乳液最低成膜温度对涂层阻隔性能的影响

通过对连续乳液聚合的偏氯乙烯-丙烯酸甲酯（VDC—MA）共聚乳液最低成膜温度（MFFT）的测量和涂覆膜阻隔性能的测试,研究了VDC含量和PVDC胶乳的存放时间对乳液MFFT的影响。结果表明,当单体中w（VDC）〉92％时。MFFT剧增,阻隔性能急剧下降;当w（VDC）〈92％时,MFFT随VDC的质量分数上升而缓慢下降,但表观质量下降;当w（VDC）约为92％时,MFFT最低,涂层阻隔性能最佳。     

Enhanced corrosion protective coating based on conducting polyaniline/zinc nanocomposite

Conducting polyaniline (PANI) is being explored as promising material for protection of metals against corrosion. It has the possibility of making smart coatings on metals, which can prevent corrosion even in scratched areas where bare metal surface is exposed to the aggressive environment. However, PANI coatings have poor barrier and mechanical properties. The barrier property of coatings can be enhanced by the addition of appropriate filler particles. Also it has been demonstrated that nanoparticulate fillers give much better barrier properties even at lower concentrations. In this study, the effect of zinc nanoparticles on the anticorrosive property of PANI coating on iron samples has been investigated. The PANI/Zn nanocomposite was synthesized by in situ polymerization of aniline in the presence of Zn nanoparticles. The nanocomposite was characterized by using FTIR, conductivity measurement, cyclic voltammetry, and AFM techniques. Results showed that PANI/Zn nanocomposite coating has improved corrosion protection effect when compared with pure PANI coating. The corrosion current of PANI/Zn coated samples were found to be much lower than that of pure PANI coated samples. The results were referred to the good barrier properties of Zn nanoparticles and improvement in electrochemical corrosion protection of PANI coating in the presence of Zn nanoparticles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Barrier and adhesion properties of anti-corrosion coatings based on surfactant-free latexes from anhydride-containing polymers

We have successfully obtained surfactant-free latexes from anhydride-containing polymers, including poly(styrene-alt-maleic anhydride) (PSMA), maleinized polybutadiene (PBDMA), and poly(octadecene-alt-maleic anhydride) (POMA). Here we report barrier and adhesion properties of the coatings made from these surfactant-free latexes, which were crosslinked with adipic acid dihydrazide (ADH). The barrier property of these coatings was studied with electrochemical impedance spectroscopy in NaCl solutions on pretreated aluminum substrates. PSMA and PBDMA-based coatings demonstrated good barrier property, indicated by the absence of corrosion after 1-month immersion in NaCl solutions, which was comparable to that of a commercially available polyester coating. The polyester coating, however, was found to hydrolytically degrade when immersed in a NaCl solution, which was not observed for our latex-based coatings. The POMA-based coating showed inferior barrier property on un-pretreated aluminum, likely due to inhomogeneous film formation and poor adhesion to the substrate, but the adhesion could be improved by an alkali pretreatment of the substrate. In comparison, PBDMA and PSMA-based coatings showed much better adhesion toward the aluminum substrates. The anti-corrosion behavior appeared to be closely related to both the barrier and adhesion properties of the coatings on the metal substrate.     

镀层中基体金属扩散系数的测定

铜在防渗铜镀层中的扩散系统是评价镀层防渗铜能力的重要参数。采用电子显微探针法,“俣野”数值方法推导出扩散系数。并分析了铜在柱状和块状镍镀层中的扩散系数。     

Simulation of Hardness Testing on Plasma-Sprayed Coatings

A plasma-sprayed thermal barrier coating consisting of a NiCoCrAlY bond coat and Ce-stabilized zirconia ceramic coating was heat-treated at 400°C for 1000 h. Microhardness measurements were used to evaluate microstructural variations throughout the coating. One hundred and twenty measurements were performed at both the bond coat and ceramic coating positions within the thermal barrier coating system. Both data sets were analyzed to assess whether they could be described as Gaussian (i. e., "normal") or Weibull distributions. The influence of the sample size, i. e., the number of microhardness tests for a group, on the mean hardness value was also evaluated by a Monte Carlo simulation procedure. The mean value, the standard deviation, the coefficient of variation, and the Weibull modulus for the subsets of data were calculated to assess these effects. The confidence for the mean value was also considered. The results indicated that the reliability of the microhardness test improved as the sample size increased. At least 20 measurements were needed to distinguish differences in micro-hardness between the bond coat and the ceramic coating at a 95% confidence level.