【作者】 刘孔华；

【导师】 罗远芳； 刘岚；

【作者基本信息】 华南理工大学 ， 材料学， 2014， 博士

【摘要】 以聚丹物为蕋体添加泞电填料组成的聚丹物泞电泛合材料（如圩电胶）山于.H有加T-温度低、可连接线分辨率小及环境友好性等优点，成为丫新-?代理想的电子封装连接材料。但是它仍存在任电率低、力学剪切强度蒂等问题。如何形成更有效的疗电通路媛提髙拜电胶技电性的关键。石墨烯及纳米银等纳釆材料由干本身M.有的优异泞电性和力学性能在聚丹物玲电复丹材料方而W有广阔的应用前晃。本论文采用液相剥离法制备f高质虽石墨烯，并分別通过原位法和聚酰胺胺树状大分子功能化石墨烯制茶丫纳米银粒子/石墨烯杂化物及银纳米线拓墨烯杂化物;然后将其应用于环氧树脂导电胶中，用以增强其导电性和剪切强度t对其结构与性能进行了研?^采用1-氛乙基-2-乙基4甲基咪唑（2E4MZ-CN)为稳定剂，在低沸点乙腈溶剂中直接超声剥离无然石墨制备石墨烯。研宂了初始天然石墨浓度、2E4MZ-CN浓度及超声时间对石墨烯浓度的影响。AFM和Raaran衷明制备得到了单尾或少层石墨烯.TEM、XRD和XPS表明制谷的石墨烯保持原有品体结构，含氣结枸缺陷捏度较小。揭示了液相剥离石墨烯的作用机理主要是石墨烯与2E4MZ-CN中咪唑环之间的twi相互作用。在液相剥离石墨烯体系中直接加入银盐<乙酸银）与2E4MZ-CN形成络合物，在环氧树脂蓰体中原位生成纳米银粒子，分布在石墨烯表而。TEM、XRD和XPS表明丫纳浓银粒子的生成。垚石墨烯和乙酸银含量分別为环氣树脂的0.6^?和30w极时制崙的泞电胶体积电阻率达4.8E-5Q cm.微观界面结构表明原位生成的纳米银/石墨烯在环氧树脂I古1化时焓结在银片表而和银片之间，改变了原来银片被树脂阻阽的结构t从而提萵泞电性。采用端胺恶聚酰胺胺树状大分子迪过原位过程对液相剥离的石墨烯进行非共价功能化，得到无洧剂的聚酰胺胺功能化石墨烯流体。采用FTIR, NMR和EA表明丹成丫聚酰胺胺。TEM和XRD研宂丫聚酰胺胺功能化石墨烯的结抅形态t表明原位生成的聚酰胺胺可插尾在石墨烯片层间，对石墨烯起到稳上分敗的作用，且不会破坏K-结构。分析了聚酰胺胺与石墨烯之间相互作用，表明石墨烯与聚酰胺胺外端氧基或内层酰胺基等位罝发生作ML以聚酰胺胺同时力纳米银模帜和还原剂制备纳米锒粒子/石墨烯杂化物。研宂T聚酰胺胺还原纳米银拉子的作用机理，表明银离子々聚酰胺胺中各种胺单元可发生络合1形成的络丹物通过中低温加热处理没生还原，生成纳米银粒子修饰石墨烯。杂化结构形态研宂表明，纳米银粒子均匀分布在石墨烯片层表面t无游离在外的粒子，且粒径较平均。1.0、2.0和3.0代聚酰胺胺控制合成的纳米银粒子粒径分别为13nm，12nm和7nm，且在3.0代中纳米银粒子在石墨烯表面的分布密度最大。聚酰胺胺/石墨烯/纳米银复合物可固化环氧树脂，且体系出现两个或三个固化放热峰。当石墨烯和乙酸银含量分别为环氧树脂的0.6wt%和24wt%时制备的导电胶体积电阻率达3E-5Ω·cm，比空白样降低了83%。界面结构研究表明，石墨烯片层均匀分散在基体中，通过石墨烯表面纳米银的烧结将微米银片通过石墨烯桥接起来，形成良好的导电通路。采用边缘功能化法制备边缘接枝对氨基苯甲酰基功能化石墨烯，功能化反应只发生在石墨烯边缘处，对主体结构破坏程度小。以丙三醇为还原剂和溶剂，PVP稳定下制备了直径为50±10nm，长度为8±5μm的银纳米线，呈现网络结构。采用共沉降法制备了石墨烯与一维银纳米线杂化物。石墨烯与银纳米线通过两者之间相互作用可自动发生杂化组装过程，形成共沉淀。研究了杂化物的结构形态，表明石墨烯片层嵌入在纳米银线网络中，形成三维层状网络结构。研究了两者之间的相互作用发现，银纳米线网络对石墨烯起到阻隔分散的作用，同时石墨烯片层可有效防止纳米银线氧化。由于银纳米线在低渗流阈值下可形成较多的导电通路，同时石墨烯片层增强了银纳米线网络中线与线之间的连接，因此在杂化结构中形成了顺畅的三维导电网络。石墨烯的加入使得银纳米线网络强度增加，因此杂化物对导电胶的导电性和剪切强度具有明显的协同增强作用。边缘功能化石墨烯由于边缘处接枝基团可与环氧树脂形成共价界面结合，可有效实现填料与基体间负荷转移，对导电胶剪切强度具有更明显的增强效应。更多还原

【Abstract】 Polymer-based conductive composites (eg. electrical conductive adhesives, ECAs)which consist of polymer and conductive fillers have been considered as the new promisingmaterial for electronic packaging because of the advantages of low processing temperature,fine pitch interconnect and environmental friendliness. However, there are some issues suchas low electrical conductivity and poor mechanical strength which still need to be solved. Theformation of effective conductive paths in the ECAs is the key to improve the electricalconductivity. The nanomaterials such as graphene and silver nanostructure have been widelyused in the conductive composites as result of the excellent electrical and mechanicalproperties. In the study, pristine graphene with high quality was prepared by liquid-phaseexfoliation method. Then the silver nanoparticle (AgNP)/graphene hybrid were prepared byin situ method and Poly(amidoamine)(PAMAM) dendrimer functionalization. Also, the silvernanowire (AgNW) decorated graphene hybrid was generated. The graphene/Ag hyrid wereused to reinforce the electrical conductivity and shear strength of epoxy-based ECAs. Both ofthe structure and properties of ECAs were investigated.Graphene was prepared by direct exfoliation of natural graphite in low boiling-pointsolvent acetonitrile when1-cyanoethyl-2-ethyl-4-methyl imidazole (2E4MZ-CN) was used asstabilizer. The influence of the initial concentration of natural graphite, the concentration of2E4MZ-CN and the sonication time on the concentration of graphene in the dispersions wasinvestigated. The result of AFM and Raman indicated that single and few-layer graphenesheets were obtained. TEM, XRD and XPS demonstrated that the original crystallinestructure was preserved and there was few structure defects. The exfoliation of graphene wasinduced by the π-π interaction between graphene and the imidazole ring in2E4MZ-CN. TheSilver acetate (AgAc) was added to the exfoliated graphene dispersion. The complex wasgenerated between the AgAc and2E4MZ-CN. The AgNPs were in situ generated in theepoxy matrix and evenly distributed on the surface of graphene. The formation of AgNPs wasconfirmed by TEM, XRD and XPS. The ECAs have a volume resistivity of4.8E-5Ω·cmwhen the content of graphene and AgAc was0.6wt%and30wt%. The investigation ofinterfacial structure of the composites indicated that the generated AgNP/graphene hybrid sintered with microscale Ag flakes. The original structure in which the Ag flakes wereisolated by epoxy resin was changed, leading to the improvement of electrical conductivity.The liquid-phased exfoliated graphene was non-covalently functionalized by PAMAMdendrimer with terminal amino-group. FTIR, NMR and EA confirmed the synthesis ofPAMAM. The investigation of the structure morphology of PAMAM functionalized grapheneby TEM and XRD revealed that the intercalation of in situ synthesized PAMAM amonggraphene layers stabilized the graphene sheets and the functionalization did not disturb thestructure of graphene. The interaction sites between graphene and PAMAM dendrimer lied interminal amino-groups and interior tertiary amines. The AgNP/graphene hybrid wasgenerated by using PAMAM as both of the stabilizer and reducing agent. The mechanisminvestigation of the reduction of AgNPs by PAMAM revealed that the complex was formedbetween Ag ions and the amine groups in PAMAM. Then the AgNPs were generated byheating treatment of the complex under low and middle temperature. The investigation of thestructure of the hybrid demonstrated that the AgNPs with average size were uniformlydistributed on the surface of graphene sheets and there was nearly no isolated AgNPs outsidethe graphene sheets. The particle size generated in1.0G,2.0G and3.0G was13nm,12nm and7nm, respectively. The density of AgNPs generated in3.0G PAMAM was the largest. ThePAMAM/graphene/AgNP composite can cure the epoxy resin. There were two or three mainexothermic peaks in the curing system. The volume resistivity of the ECAs filled with0.6wt%graphene and24wt%AgAc reached at3E-5Ω·cm, the decrease of83%comparedwith the control samples. The investigation of the interfacial structure revealed that thegraphene sheets were uniformly dispersed in the matrix and the microscale Ag flakes werejointed together by the connection of graphene sheets, thus leading to the formation ofeffective conductive paths.The edge-functionalized graphene with4-aminobenzoyl group located at the edges wasprepared by edge functionalization method. The AgNWs with diameters of50±10nm andlength of8±5μm were prepared by using glycerol as reducing agent and PVP as stabilizer.The AgNWs display network structure. The graphene/AgNW hybrid was prepared throughthe simultaneous sedimentation process when the graphene were combined with AgNWs. Theinteractions between graphene and AgNWs resulted in the occurrence of co-assembling process and the simultaneous sediments. The investigation of the hybrid structure revealedthat the graphene sheets embedded in the AgNW network, leading to formation ofthree-dimensional (3D) network structure. The interactions between the graphene andAgNWs were investigated. The graphene sheets were separated by the AgNW network andthe graphene sheets can prevent the AgNWs from oxidation. Since the AgNWs can providedmany conductive paths at low percolation threshold and the graphene sheets enhanced theinterfacial contacts between the AgNWs, there was effective3D electrical conductivenetwork formed in the hybrid structure. The graphene sheets also enhanced the strength ofAgNW network. Thus there were synergistic effects on the reinforcement of the electricalconductivity and shear strength of the ECAs. The covalent interfacial bonding between theamino-group at the edge of edge-functionalized graphene and epoxy resin leaded to theeffective load transfer from the matrix to fillers, thus significantly improving the shearstrength of ECAs.更多还原