【作者】 胡传群；

【导师】 曾黎明；

【作者基本信息】 武汉理工大学 ， 复合材料学， 2009， 博士

【摘要】 镀银玻璃微球在军事、国防、电子、光学、医学、工业催化、生物工程等领域具有重要的应用价值。但银镀层易脱落,导致电阻变大,性能下降,如何用简单可行的方法得到结合牢固的镀层成为人们努力追求的目标。本文提出了新的无钯活化方法,成功在空心玻璃微球和聚合物微球表面化学镀银,探讨了活化机理和基体与镀层作用机理及复合粒子在导电填料方面的应用。主要研究内容和结论如下：(1)采用甲醛还原银氨溶液方法能够很好地镀覆经过除油、粗化、敏化及活化预处理后的空心玻璃微球,活化过程赋予基材大的比表面积和高活性,比表面积变为原来的28.8倍,极大程度上促进了银粒子沉积,形成了大量孔穴,银离子沉积后,体系表面积下降,能量降低,可以自发发生。(2)超声波振动能有效分散溶液中固体粒子,增加表面活性,使沉积银颗粒细化,特别有利于银的径向沉积,且能简化工艺。镀液配制方法显著影响银的析出,从而影响到镀层的表面形貌,适量降低银液滴加速度和可以减缓镀覆速率,能够避免微球表面部分区域出现较大凸起；降低反应温度亦可降低化学镀速率,使单质银均匀沉积。(3)采用乳液聚合方法可以制备单分散性较好的聚苯乙烯粉体,利用透析膜可以分离聚合体系中的小分子,单体、乳化剂、引发剂比例影响聚苯乙烯粉体粒径大小及分布。粉体镀银后电阻率达6×10-3Ω·cm,可以用作导电填料。(4)一种较佳的银导电胶配方为：填充粒子为粒径为5 um～8 um的镀银粉体,其各部分的较佳质量配比为,环氧树脂：镀银粉体=100:260,其中镀银粉体为枝状和球状按1：3质量比,固化剂DDM,发现其耐银迁移性为银导电胶的3倍以上,满足使用要求。(5)一种成功的银导电胶固化工艺为：选用芳香二胺中的4,4-二氨基二苯甲烷(DDM)作为改性树脂体系的固化剂,其用量为30wt%左右,可以满足完全固化的要求。利用非等温DSC方法确定改性聚醚醚酮／环氧树脂体系的固化制度：80℃/2h+125℃/2h+180℃/3h,即80℃预固化2h,再升温至125℃固化2h,180℃后固化3h。(6)活化后的玻璃微球和镀层的作用机理包括强的化学键和机械咬合作用机理,大大提高了镀层结合力和耐迁移能力,同时提高了导电胶的可靠性。本文的创新点在于：1)首次提出氢氧化铁凝胶活化体系,成功在玻璃微球和聚合物微球表面进行化学镀银；2)探索了氧化铁在玻璃微珠表面的沉积机理和在化学镀中的作用机制；3)探讨了镀层形态的影响因素和形貌控制方法；4)制备了复合镀膜银导电胶并探讨了其性能。更多还原

【Abstract】 The Ag-coated cenospheres can be of great application interest in war industry, national defence, electronics,optics, medicine, industrial catalysis, bio-engineering and so on. But the silver layer’s being brushed off easily causes the rising of the resistance of the Ag-coated cenospheres and weakening of their performance, hunting for a simple and feasible method to make silver coating tight and firm is all the researchers’aim. In this paper, new Pd-free activating agent is introduced, and Ag-coated cenospheres and Ag-coated polymer microspheres are produced, mechanism of activating and the coated layer and its application as conductive filler are studied。The main content of the research and conclusion are as follows:（1） The results show that the formaldehyde can react with silver nitrate-ammonia to form silver layer on the surfaces of cenosphere which is pretreated within four steps: degreaseing, coarsening, sensitizing,activation, activation enlarging specific surface area and reactivity, whose specific surface area is 28.8 times of bebore,which promote silver deposition. A great deal of little holes formed during pretreatment make room for silver ion, whose surface area and energe will drops if reacted, such is of spontaneity.（2） Ultrasonic can effectively disperse the cenosphere particles, enhance surface activity, promote radical deposition, simplify process.The way to make the electroless plating solution remarkably affect the deposit of silver, also the appearance of the micro cenospheres. Lowering feeding rate of silver nitrate-ammonia and reaction temperature can slow plating,so as to prevent big Ag particles from depositing on the cenosphere surface,in this way good samples is manufactured.（3） Emulsion polymerization is fit to prepare polystyrene microspheres of good monodispersion, dialyzer is helpful to separate small molecules from polymer system. The ratio of monomer, emulsifier, nitiator affect the size and distribution of microspheres. electrical resistivity of silver coated microspheres is 6x10^-3Ω·cm,which can be used as conductive fillers.（4） An excellent fomula of conductive adhesive is:epoxy:filler （5μm～8μm）= 100:260, filler（dendritic particles:microspheres=1:3 wt）, DDM as curing agent, whose Ag-migratory is 3 times as silver conductive adhesive, fit for use.（5） A successful curing process is:DDM as curing agent,30wt%,according DSC to fix:80℃/2h+125℃/2h+180℃/3h（6） Influence mechanism of cenospheres and the coated layer consist of chemical bond and occluding, which promote to form compact layer and Ag-migratory and increase adhesive’s reliabilityThe main innovation are:1) bring Fe（OH）3 gel as activator for the first time in the world, electroless silver deposition on surface of cenospheres and PS microspheres is carried out.2) Deposition mechanism of ferric oxide on surface of cenospheres is studied;3) The effect on configuration of layer and control of morphology of coating is discussed;4) conductive adhesive is prepared and its performances is studied.更多还原