【作者】 张鑫；

【导师】 彭坤； 胡盛青；

【作者基本信息】 湖南大学 ， 材料工程（专业学位）， 2019， 硕士

【摘要】 石墨烯增强铜基复合在理论上可以兼具铜的高导电导热性与石墨烯的高强等优良特性,从而可望在航空航天、机械工业、电子封装等领域得到广泛的应用。然而石墨烯在铜基体中难以分散均匀,石墨烯与铜基体之间润湿性较差及界面结合性能差,使得实际制备的石墨烯/铜复合材料的性能与理论值有很大的差距。因此,寻找合适的工艺方法和通过复合材料界面结构设计来改善复合材料的界面结合性能成为了改善石墨烯增强铜基复合材料性能的主要方向。本文分别采用球磨法、吸附法制取出分散均匀的氧化石墨烯/铜复合粉体,然后经高温还原、真空热压烧结技术制备了石墨烯/铜复合材料,探讨了工艺参数对石墨烯/铜复合材料微观结构、导电、导热、力学性能的影响规律。采用球磨法制备石墨烯/铜复合材料,并研究石墨烯含量、球磨时间对石墨烯/铜复合材料微观结构及性能的影响规律。当石墨烯含量较少时,石墨烯可以均匀地分散在铜基体中,但石墨烯含量达到0.9 wt%后,石墨烯会出现团聚现象,导致复合材料的力学性能下降。随着球磨时间的增加,复合粉末颗粒细化,复合材料机械性能显著提升。然而,采用球磨法不能改善复合材料中石墨烯与铜之间的界面润湿性和界面结合性能,制备的复合材料的导电导热性能均出现了不同程度的下降。采用吸附法实现石墨烯与铜的均匀混合,并通过在石墨烯上生成Cu₂O改善润湿性及界面结合性能,从而制备出具有优异综合性能的复合材料。研究了石墨烯含量、还原时间、热压温度对石墨烯/铜复合材料微观结构及综合性能的影响规律。通过对铜粉表面改性获得表面携带正电荷的铜颗粒,利用电荷吸附原理使带负电荷的氧化石墨烯均匀地吸附在铜粉表面,实现均匀混合。采用热还原方法使氧化石墨烯还原并在石墨烯上形成薄的Cu₂O层,从而有效地改善石墨烯与铜之间的浸润性和界面结合性能,使复合材料的导热率、导电率和机械性能均得到明显提升。在热压烧结过程中,烧结温度的升高有利于提高材料致密度及石墨烯与铜之间相互作用力,提升复合材料的性能。当石墨烯含量为0.6 wt%、还原时间为3 h,热压温度为900℃时,石墨烯/铜复合材料获得最好的综合性能,其导热率、导电率、显微硬度、屈服强度、抗拉强度分别为413 W·m^-1·K^-1、93%IACS、95.4 HV、107.4MPa、226.7 MPa。通过在复合材料石墨烯片层上生成Cu₂O来改善界面润湿性,增强界面强度,降低界面热阻,从而提高复合材料的导热性能,该方法为具有优良综合性能的石墨烯/铜复合材料的制备提供了一种新思路。更多还原

【Abstract】 Graphene reinforced copper matrix composites can theoretically possess both high conductivity and thermal conductivity of copper and high strength of graphene,which was expected to be widely used in aerospace,machinery industry,electronic packaging and other fields.However,graphene was difficult to disperse uniformly in copper matrix.The poor wettability and interface bonding between graphene and copper matrix made the properties of graphene-copper matrix composites far from the theoretical values.Therefore,the main direction of improving the properties of graphene reinforced copper matrix composites was to find suitable process methods and improved the interfacial bonding properties of composites through the design of the interfacial structure of composites.In this paper,graphene/copper composite powders with uniform dispersion were prepared by ball milling and adsorption methods respectively.Graphene/copper composite materials were prepared by high temperature reduction and vacuum hot pressing sintering.The effects of process parameters on the microstructure,electrical conductivity,thermal conductivity and mechanical properties of graphene/copper composite were discussed.Graphene/copper composites were prepared by ball milling method,the effects of graphene content and milling time on the microstructure and properties of graphene/copper composites were studied.When graphene content was low,graphene could disperse uniformly in the copper matrix,but graphene would agglomerate while the graphene content reached 0.9 wt%,resulting in the decline of mechanical properties of the composite.With the increase of milling time,the composite powder particles were refined and the mechanical properties of the composite material were improved significantly.However,the interfacial wettability and interfacial bonding properties between graphene and copper in composites can not be improved by ball milling method,and the electrical conductivity and thermal conductivity of the composites decreased in varying degrees.The uniform dispersion of graphene in copper matrix were achieved by adsorption method,and the wettability and interfacial bonding properties were improved by forming Cu₂O on graphene,improving the comprehensive properties of composite materials.The effects of graphene content,reduction time and hot pressing temperature on the microstructures and comprehensive properties of graphene/copper composites were studied.Copper powders with positive charge were obtained by surface modified,and graphene oxide with negative charge was uniformly adsorbed on the surface of copper powder by charge adsorption,which achieved uniform mixing.Under the thermal reduction,graphene oxide was reduced and a thin Cu₂O layer were formed at the graphene,which improved the wettability and interfacial bonding between graphene and copper,and improved the thermal conductivity,electrical conductivity and mechanical properties of the composites.During the hot pressing sintering process,the increase of sintering temperature was conducive to improve the density of materials and the interaction between graphene and copper,which would improve the properties of composites.When the graphene content was 0.6 wt%,the reduction time was 3 h and the hot pressing temperature was 900℃,graphene/copper composites possessed the best comprehensive properties,the thermal conductivity,electrical conductivity,microhardness,yield strength and tensile strength were 413W·m^-1·K^-1、93%IACS、95.4 HV、107.4 MPa、226.7 MPa,respectively.By introducing Cu₂O on the graphene in the composite,which would improve the wettability and interfacial bonding strength and reduce the thermal resistance,and then improved the thermal conductivity of the composites.The method provided a new idea for the preparation of graphene/copper composites with excellent comprehensive properties.更多还原