【作者】 闫小星；

【导师】 徐国跃；

【作者基本信息】 南京航空航天大学 ， 材料加工工程， 2011， 博士

【摘要】 随着红外探测设备和红外制导武器的迅速发展，红外低发射率涂层(IRLEC)已经成为十分关注的话题，特别是由铜(Cu)填料和聚氨酯(PU)组成的金属/PU复合涂层在IRLEC领域有应用的潜力。然而，Cu/PU涂层较差的耐腐蚀性和力学性能是限制其应用的主要原因。在本文中，我们研究了界面改性对低发射率涂层腐蚀性能及力学性能的影响。并且，计算了IRLEC的寿命，为工程化提供可靠依据。用γ氨丙基三乙氧基硅烷(KH550)化学改性Cu粉表面提高Cu和PU高聚物之间的界面结合，得到了具有高耐腐蚀性能的红外低发射率Cu/PU涂层。由于KH550的加入使Cu和PU之间产生了明显的相互作用。一定合适的量的KH550有利于Cu的分散，在Cu和PU之间诱导产生了较强的化学界面结合，从而提高了Cu/PU涂层的耐腐蚀性能并且保持了较低的红外发射率，力学性能随着KH550的量增加而提高。用KH550和表面活性剂十六烷基三甲基溴化铵(CTAB)协同作用改性Cu粉表面，KH550使Cu和PU之间产生了明显的相互作用，暗示了KH550能够改善Cu和PU之间的化学界面结合，而CTAB只能促进Cu和PU之间的物理结合。一定合适的量的KH550和CTAB的协同作用改善了Cu和PU之间的界面结合，有利于Cu的分散和降低Cu/PU涂层的孔隙率，从而提高了Cu/PU涂层的耐腐蚀性能并且保持了较低的红外发射率。经协同改性后Cu/PU涂层的力学性能明显提高。采用球磨的方法用银(Ag)表面改性Cu，Ag均匀分布在Cu中，球磨后在Ag-Cu复合粉表面形成了油层，与有机相的相容性得到了改善，从而提高了涂层的耐腐蚀性能并且保持了较低的红外发射率。经过Ag表面改性后，球磨Ag-Cu/PU涂层的冲击强度保持不变，而球磨Ag@Cu/PU涂层的冲击强度比改性前较好。铝(Al)取代Cu将Cu/PU界面改性为Al/PU界面，由于电导率随着Al含量的增加而增加，涂层的红外发射率明显降低。Al含量和力学性能之间呈现“U”型曲线，Al/PU复合涂层在40wt.%Al含量时具有良好的附着力和冲击强度。Al氧化生成的Al2O3不会牺牲PU本身的耐腐蚀性能，并且低发射率复合涂层表现出良好的耐腐蚀性。青铜和环氧改性将Cu/PU界面改性为Cu-Sn/EPU界面，由于电导率随着青铜含量的增加而增加，涂层的红外发射率明显降低。青铜/EPU复合涂层在青铜含量低于50wt.%时具有良好的附着力和冲击强度，但是当青铜含量从50wt.%升高到60wt.%时涂层的力学性能下降。低发射率青铜/EPU复合涂层表现出良好的耐腐蚀性。通过比较青铜/EPU涂层、Cu/PU涂层、球磨Ag-Cu/PU涂层和Al/PU涂层，青铜含量为40wt.%的青铜/EPU涂层具有最佳的附着力、红外低发射率和良好的耐腐蚀性。采用微结构-电化学模型预测了红外低发射率复合涂层在盐雾环境中的寿命。IRLEC在3.5wt.%NaCl溶液中收集的电化学数据作为基于机理的腐蚀模型的输入，从而预测涂层的寿命。为了检测计算结果，模型预测与盐雾测试结果进行了比较。该模型能够预测IRLEC的盐雾寿命，但在短时间对寿命预测不足，长时间过高预测。预测不足可能与聚合物对金属颜料颗粒的腐蚀保护有关。在较长时间模型过高预测可能与孔隙率的影响没有包括在这个简单的模型内有关。IRLEC的力学性能随着加热温度的升高和时间的延长而下降，涂层的最高耐受温度为573K。采用Arrhenius关系计算了红外低发射率复合涂层在不同马赫数下冲击强度下降至某一水平的力学寿命。与观测数据相比，计算结果验证了模型预测的有效性。IRLEC的发射率随着加热温度的升高和时间的延长而升高，涂层失效时的发射率随着马赫数的减小而升高。采用Arrhenius关系计算了红外低发射率复合涂层的耐盐水腐蚀寿命。计算结果与耐盐水实验的观测数据对比，验证了模型预测的有效性。IRLEC的发射率随着耐湿热环境下加热温度的升高和时间的延长而升高。采用Arrhenius关系计算了红外低发射率复合涂层的耐湿热寿命。计算结果与湿热观测数据相比，验证了此模型预测的有效性。更多还原

【Abstract】 With the rapid development of infrared detection devices and infrared-guided weapons, infraredlow emissivity coatings (IRLEC) have recently become a topic of considerable interest. Especially,the metal/polyurethane composite coatings composed of copper (Cu) filler and polyurethane (PU)have the potential for applications in IRLEC. However, the poor corrosion resistance and mechanicalproperties of Cu/PU coating are the major causes limiting its application. In the present work,experiments were carried out to assess the influence of interface modification on the corrosion andmechanical properties of low emissivity coating. Furthermore, the lifetime of the IRLEC wascalculated for engineering applications.Surface of Cu powder was chemically modified using gamma-aminopropyltriethoxy silane (KH550)in order to improve the interfacial interaction between Cu and PU polymer, and therefore, expectablecorrosion resistance of the Cu/PU coating with infrared low emissivity was acquired. An an obviousinteraction between Cu and PU was induced by the addition of KH550. Results have shown that theproper amount of KH550is benefit to the dispersion of Cu and induces the strong chemical interfacialinteraction, which often keeps the infrared low emissivity and increases the corrosion resistance of theCu/PU coating. Mechanical properties increase with increasing KH550content.Synergy effect of the surface modification of Cu by surfactant, cetyl trimethyl ammonium bromide(CTAB) and KH550was evaluated. An obvious interaction between Cu and PU was induced by theaddition of KH550, which implied that KH550can improve the chemical interfacial interaction whileCATB only improved the physical interaction between Cu and PU. The interfacial interaction betweenCu and PU was improved by the synergy effect of proper amount of KH550and CTAB, benefiting tothe dispersion of Cu and the low porosity of Cu/PU coating, which keeps the infrared low emissivityand increases the corrosion resistance of the Cu/PU coating. The mechanical properties of Cu/PUcoatings increase obviously after synergy effect of the surface modification.Surface modification of Cu with silver (Ag) using a ball-milling method evaluated was evaluated. Itwas found that Ag was homogeneously distributed in Cu and the encapsulation of oil layer on thesurface of Ag-Cu composite powders was formed after ball-milling, therefore, compatibility withorganic phase was improved, which often keeps the infrared low emissivity and enhances theanti-corrosion performance of the coating. After surface modification with Ag, the impact strength of(ball-milled Ag-Cu)/PU coatings keeps unchanged, and the impact strength of (ball-milledAg@Cu)/PU coatings is better. Modification of Cu/PU interface with aluminum (Al) to Al/PU interface was evaluated. Due toincreasing the electrical conductivity with increasing Al content, the infrared emissivity is deceasingobviously. The relationship between the Al content and mechanical properties presents a “U” type, andAl/PU composite coating has good adherence and impact strength at Al content of40wt.%. Corrosiontest results showed that the Al2O3from Al oxidation do not sacrifice the corrosion resistance of PUitself, and the low emissivity composite coatings exhibited favorable corrosion resistance.Modification of Cu/PU interface with bronze and epoxy to Cu-Sn/epoxy-polyurethane (EPU)interface was evaluated. Due to increasing the electrical conductivity with increasing bronze content,the infrared emissivity is decreasing obviously. The bronze/EPU composite coating had good adherenceand impact strength at bronze content below50wt.%, and then mechanical properties decreased in thebronze content range from50wt.%to60wt.%. The low emissivity bronze/EPU composite coatingsexhibited favorable corrosion resistance. By comparing bronze/EPU, Cu/PU,(ball-milled Ag-Cu)/PUand Al/PU coatings, the bronze/EPU coatings with40wt.%bronze have the best adherence, infraredlow emissivity and good corrosion resistance.The microstructural-electrochemical model is employed to predict the lifetime of infrared lowemissivity composite coatings in chloride environments. Electrochemical data collected in3.5wt.%NaCl solution is presented for the IRLEC, and these values are used as inputs for a mechanistic-basedcorrosion model which yields the salt spray life of the coating. To check the calculated results, themodel predictions were compared with the results of salt spray tests. The current work showed thatthe model was able to predict lifetime of IRLEC under salt spray, but tended to under-predict lifetimeat short times and over-predict at long times. Under-prediction may be associated with corrosionprotection of metallic pigment particles by polymer. Over-prediction by the model at longer exposuretimes may be associated with the fact that an influence of porosity is not included as a part of thissimple model.The mechanical properties of IRLEC decreased with increasing heating temperature and time, andthe maximum-tolerance temperature of the coating was573K. Moreover, the Arrhenius relationshipwas employed to calculate the mechanical lifetime of infrared low emissivity composite coatings, andthe mechanical lifetime at different Mach numbers was calculated when the impact strength wasdecreased to a particular level. The calculated results when compared with observation data validatethe effectiveness of the model predictions.The emissivity of IRLEC increased with increasing heating temperature and time, and that theemissivity of coating failure increased with decreasing Mach number. Moreover, the Arrheniusrelationship was employed to calculate the lifetime of infrared low emissivity composite coatings.When compared with observation data the calculated results validate the effectiveness of the model predictions.The emissivity of IRLEC increased with increasing heating temperature and time in damp heat.Moreover, the Arrhenius relationship was employed to calculate the lifetime of infrared lowemissivity composite coatings in damp heat. The calculated results were compared with observationdata and validated the effectiveness of the model predictions.更多还原