【作者】 于庆杰；

【导师】 马学虎；

【作者基本信息】 大连理工大学 ， 化学工程， 2009， 博士

【摘要】 随着现代科技的飞速发展,化工、食品制造、电子、海水淡化、核工业和能源等各个工业部门对防治换热器表面腐蚀和结垢的问题提出了越来越高的要求,原有的以环氧树脂和酚醛树脂为基础的换热器多功能涂料为实现换热器表面耐腐蚀性能、抑制污垢沉积和高热导率等多功能的耦合,需要多次多层涂覆以满足其多功能性的实现,不仅施工工艺复杂,而且难以修复,无法满足实际使用的要求。本论文以溶胶-凝胶法制备的无机金属氧化物/陶瓷复合材料和自由基溶液聚合含氟硅共聚物为基础,开展了材料合成、形态结构表征和表面功能改性的系统研究。尝试开发出一种可以一次性在换热器表面涂装,功能层自动分层,具有耐腐蚀、抑制污垢和高热导率的多功能复合材料。具体地说,主要在以下几个方面开展了探索性的研究工作。（1）通过溶胶一凝胶工艺制备了CuO/SiO₂和NiO/SiO₂纳米复相陶瓷涂层。研究表明,高热导率的弥散相纳米氧化物粒子包埋于氧化硅矩阵中,形成类内晶型结构,可以引起裂纹桥连、钉扎、偏转等纳米复相强韧化效应,从而减轻矩阵界面残余应力,控制陶瓷固有的裂纹,减少陶瓷材料的结构缺陷,显著提高纳米复合陶瓷涂层的耐腐蚀性能和导热性能。对比实验表明,添加的纳米粒子本身的物理化学性质对于纳米复合陶瓷涂层耐腐蚀性能和导热性能的提高同样有着至关重要的影响。（2）分别采用Cu（NO₃）₂·3H₂O和Cu（C₅H₇O₂）₂（Cu（acac）₂）为金属醇盐制备了具有不同CuO含量的SCuN和SCuC系列CuO_X/SiO₂纳米复合材料。随着氧化铜加量的增加,SCuN和SCuC系列复合材料中纳米氧化铜分别存在从氧化铜纳米球到纳米棒（SCuN系列）以及从氧化铜纳米球到方形结构（SCuC系列）的晶形转变。同时,随着氧化铜加量的增加,形成的纳米粒子的尺寸增加,导致植入粒子和硅陶瓷矩阵之间的热扩散失配增大,从而扩大了微裂纹的尺寸以及微裂纹的数量,导致复合涂层的缺陷增多。低的弥散相纳米粒子的添加量、低团聚和高度分散是溶胶-凝胶工艺制备结构致密、缺陷更少的纳米复合材料的关键因素,更有利于提高其耐蚀能力。此外,纳米粒子含量以及粒子尺寸大小对纳米复合涂层热导率的提高也有着重要的影响。（3）采用自由基溶液聚合与溶胶-凝胶法相结合的方法制备了可以自动分层的含氟高分子/SiO₂杂化疏水材料。疏水的含氟烷基由于其极大的表面活性自动向表面富集,定向于空气形成界面层,具有极低的表面能;柔性的碳氢主链可以有效缓解应力集聚,减少涂层缺陷;底层为硅氧网络结构,与基体材料有极强的结合力。溶剂性质及其加量可以极大地影响氟硅低聚物的结构,以及表面含氟基团的富集程度。采用良溶剂制备的低聚物大分子结构呈现更蓬松舒展的无规线团态,使含氟侧链更容易迁移到溶液/空气界面,疏水性能更好。随着溶剂加量的增加,溶液分散性更好,形成的聚合物分子量降低,从而使含氟侧链向表面的迁移速度更快,氟硅氧烷聚合物表面疏水性能更好。无机组分的增加将促进溶胶的水解和缩聚的程度,提高聚合物的分子量,增加底层硅氧网络的厚度,增强杂化材料与基体材料的结合强度,提高氟硅氧烷杂化材料的耐腐蚀和耐久性能,对氟硅氧烷杂化材料表面疏水性能影响不大。（4）通过铜金属盐,TEOS与氟硅低聚物溶液共水解缩聚制备了具有含氟侧基的碳碳主链高分子和硅氧网络的氧化铜/氟硅低聚物纳米复合低表面能材料。结果表明,纳米复合低表面能材料改性处理表面具有优异的耐腐蚀性能;优异的抗介质渗透性能;与基体有良好的附着力;显著的防垢效果;良好的热传导性。引入的氧化铜纳米粒子主要是包埋于底层硅氧网络结构内部,完善底层硅氧网络结构,提高其耐腐蚀性能和热导率,对于纳米复合杂化材料的疏水性能影响不大。含氟侧链的存在使纳米复合杂化材料具有极低的表面能,使污垢附着力降低,在换热表面的沉积也趋于分散,有利提高换热器的换热效果。更多还原

【Abstract】 The rapidly increasing needs for multi-functionalized heat transfer surfaces with good corrosion resistance,anti-fouling and high thermal conductivity are expected in many industrial fields,such as chemical industry,food fabrication,electric industry,desalination, nuclear,energy and so on,where the traditional coatings based on epoxy and phenolic resins can not satisfy all requirements owing to complex coated technology and the difficulty for repairing.In this dissertation,the work is focused on the synthesis and characterization of metal oxide/ceramic nanocomposite material by sol-gel technique and fluorinated organic-inorganic hybrid materials by free-radical random copolymerization.We attempted to fabricate a multi-functionalized nanocomposite material with good corrosion resistance,anti-fouling and high thermal conductivity by combining the useful properties of metal oxide/ceramic nanocomposite material and fluorinated organic-inorganic hybrid material.This composite material could be self-layered on heat transfer surface in one step.Homogeneous CuO/SiO₂ and NiO/SiO₂ nanocomposite coatings containing CuO and NiO nanoparticles in silica matrix were successfully synthesized by sol-gel process, respectively.The results indicated that the dispersed second phase in the silica matrix can cause crack bridging,crack pinning,and crack deflection to control the size and density of processing flaws,reduce the residual stress of the silica matrix and produce more compact surface.The thermal conductivity as well as corrosion resistance of nanocomposite coatings was significantly improved by the introduction of metal oxide particles.In comparison with NiO/SiO₂ nanocomposite coatings,CuO/SiO₂ composite coatings displayed lower corrosion protective behavior but higher thermal conductivity.Experimental results revealed that the nature of embedded nanoparticles had a vital rule on the improvement of corrosion resistance and thermal conductivity of the composite coating.Two series of CuO_x/SiO₂ samples with various Cu/Si molar ratios,have been synthesized by sol-gel technique from two different copper metal precursors,cupric nitrate hydrate（Cu（NO₃）₂·3H₂O） and cupric acetylacetonate（Cu（acac）₂） respectively.The results indicated that the structures and chemical states of CuO_x nanoparticles in the silica matrix were sensitive to the nature of chemical precursors and Cu content.At low Cu content,the primary copper oxide nanoparticles self-aggregated into normally known spherical aggregates. With the amounts of copper oxide increasing,different structure transitions of CuO_x have been found,i.e.,from nanosphere to uniform nanorod using Cu（NO₃）₂·3H₂O as chemical precursor and,to square-like frames starting from Cu（acac）₂.It has also been found that,with the increase of the CuO content,more and enlarged flaws were formed due to the formation of larger copper oxide aggregates through the Ostwald ripening process,which led to a gradually declining corrosion protection.Consequently,it could be concluded that minimum agglomeration and uniform distribution of the second phase particles in the matrix are preferred for enhancing the corrosion protection ability of CuO/SiO₂ nanocomposite coatings. Moreover,the thermal conductivity of the composite coatings could be significantly improved by adding CuO nanoparticles.But it showed a fluctuant tendency with increasing CuO content.Fluorinated silicon oligomers were prepared by free-radical random copolymerization and sol-gel process from dodecafluoroheptyl methyl acrylate（FA）,vinyltriethoxy silane （VTES）,and tetraethyl orthosilicate（TEOS）.FTIR and XPS results indicated that, hydrophobic perfluoroalkyl groups were preferentially enriched to the outermost layer at the coating film-air interface.The fluorinated silicon oligomers had a good water repellency property,governed by hydrophobic fluorocarbon groups of the outermost layer.The nature and concentration of solvent had a significant influence on the structure of molecular assemblies of the oligomers and the mobility of perfluoroalkyl side chain.Compared with ETOH and Butanol,THF was a good solvent for fluorinated silicon oligomers prepared by free-radical random copolymerization.The fluorinated silicon oligomers showed a looser random coil-like shape in THF solution.Hydrophobic perfluoroalkyl groups of the random coil-like shape fluorinated silicon oligomers can move more easily and enrich at the coating film-air interface.With the increase of the concentration of solvent,the structure of molecular assemblies of the oligomers would be rather small and loose,which made the movement of perfluoroalkyl side chain at the coating film-air interface more easily.An important role of TEOS was to increase the density of the reaction sites of the-OH groups and the thickness of the bottom layer composed of mainly silica network originating from hydrolysis and polycondensation of TEOS.The useful properties of hybrid coatings,like better wear resistance and corrosion resistance,could be significantly enhanced by the increase of TEOS, due to the improvement of thickness of the bottom SiO₂ layer and bonding between SiO₂ layer and aluminum substrates,while it had a slight influence on the surface wettability of hybrid coatings.Copper oxide/fluorinated silicon oligomers nanocomposite hybrid materials,with high corrosion resistance,anti-fouling and high thermal conductivity,have been synthesized by co-hydrolyzed and co-condensed using the as-prepared fluorinated silicon oligomers,TEOS and cupric nitrate hydrate as chemical precursor.The dispersed second phase embedded in the silica matrix have caused particle bridging,crack pinning,crack deflection and stress induced micro-cracking effects to improve corrosion resistance behavior and thermal conductivity, while it had a slight influence on the surface wettability of the hybrid coatings.The characteristics of CaCO₃ crystallization fouling on heat transfer surface were investigated in convective heat transfer test rig.It has been demonstrated that these metal oxide/fluorinated silicon oligomers nanocomposite hybrid coatings with very low surface energy could reduce the formation of deposits on heat transfer surfaces significantly.The heat transfer coefficients remained almost constant during the running,impling that almost no CaCO₃ scale formed on the treated surfaces.Obviously,this is a most promising result which indicates substantial benefits in practice.更多还原