【作者】 杨涛；

【导师】 陈文革； 颜国君；

【作者基本信息】 西安理工大学 ， 材料学， 2022， 硕士

【摘要】 传统铜基复合材料在应用过程中往往出现力学性能与导电特性倒置问题,导致其无法满足当前电子产品中引线框架和输电导线的功能特性要求。石墨烯(Gr)因其优异的机械性能和导电性能,成为铜基复合材料中最具吸引力的碳材料增强体。但是,石墨烯易团聚以及石墨烯与铜之间不润湿等问题使石墨烯优异性能在铜基体中的发挥受到一定挑战。本文基于原位生成技术的优势,创新性地采用低成本、易获得的小麦面粉作为石墨烯生成的固体碳源,在铜粉表面原位生成石墨烯包覆层,并结合湿法混合技术和放电等离子烧结技术(SPS)制备不同含量石墨烯包覆铜(Gr@Cu)增强铜基复合材料。研究不同面粉含量对铜粉表面原位生成石墨烯质量的影响,得到最优配比Gr@Cu复合粉末;系统分析石墨烯含量对复合材料的组织结构和物理机械性能的影响;采用高分辨透射电子显微镜(HRTEM)揭示复合粉末和复合材料的界面结合状况以及其与力学性能和导电性能的关系。本研究可为制备高性能石墨烯/铜(Gr/Cu)复合材料提供一定的实验和理论支撑。研究结果表明:1.在40 sccm H2和100 sccm Ar混合气氛中,800℃保温10min,原位生成了1.0Gr@Cu、0.8Gr@Cu和0.5Gr@Cu复合粉末。面粉含量由1.0 g降低到0.5 g时,原位生成的石墨烯由较厚的类石墨烯纳米片(GLNPs)转变为较薄的透明状石墨烯;Gr@Cu复合粉末的复合界面没有任何中间相且连接密实,复合界面是以Cu{001}与Gr{002}互相匹配,且晶格匹配关系为半共格界面。2.面粉原位生成石墨烯过程分为两个重要阶段。第一个是低温阶段(最高400℃),H2将铜粉表面的氧化层(Cu2O)还原为金属Cu;第二个是高温阶段(400～800℃),铜粉良好的催化作用使面粉中的化学键断裂,暴露出碳原子,高温下铜和碳原子的亲和力高,碳原子可吸附在铜表面,杂原子从铜表面被去除,降温时碳原子重组形成石墨烯。3.采用90 W,1 h超声分散和65℃,800 rpm磁力搅拌的湿法混合技术以及650℃,45 MPa,8 min的SPS技术成功制备出石墨烯含量分别为0.35 wt.%、0.70 wt.%和1.05 wt.%Gr@Cu/Cu复合材料。当石墨烯含量为0.35 wt.%和0.70 wt.%时其能够均匀分散在基体中,该复合材料只有铜的物相,未有中间相生成。4.Gr@Cu/Cu复合材料的致密度均为99%左右,显微硬度达到90～95HV,比纯铜高15%～22%。0.70wt.%Gr@Cu/Cu复合材料获得的极限抗拉强度和屈服强度分别为252 MPa和132 MPa,比纯铜高出约23%和110%,其延伸率可保持在30%左右,电导率达到86%IACS。0.70 wt.%Gr@Cu/Cu复合材料显示出高强度、高塑性和高导电的匹配。原位生成技术和湿法混合技术改善了石墨烯在铜基体中的团聚现象,获得了纯净且连接性强的界面结构以提供载荷传递,从而使复合材料具有良好的强塑性匹配和较高的导电性能。更多还原

【Abstract】 Traditional copper-matrix composite materials often have the problem of inversion of mechanical properties and electrical conductivity during the application process,which makes them unable to meet the functional characteristics requirements of lead frames and transmission wires in current electronic products.Graphene(Gr)has become the most attractive carbon material reinforcement in copper matrix composites due to its excellent mechanical properties and electrical conductivity.However,graphene is prone to agglomeration and the non-wetting between graphene and copper makes it challenging to exert the excellent properties of graphene in a copper matrix.Based on the advantages of in-situ generation technology,this paper innovatively uses low-cost and readily available wheat flour as a solid carbon source for graphene generation,and in-situ generates a graphene coating on the surface of copper powder.Combined with wet mixing technology and spark plasma sintering(SPS)technology,different contents of graphene-coated copper(Gr@Cu)reinforced copper matrix composites were prepared.By studying the effect of different flour contents on the quality of in-situ generated graphene on the surface of copper powder,the optimal ratio of Gr@Cu composite powder was obtained;The effect of graphene content on the microstructure and physical and mechanical properties of the composites was systematically analyzed;High-resolution transmission electron microscopy(HRTEM)was used to reveal the interfacial bonding state of composite powders and composites and their relationship with mechanical and electrical properties.This study can provide some experimental and theoretical support for the preparation of high-performance Gr/Cu composites.Research indicates:1.The 1.0Gr@Cu,0.8Gr@Cu and 0.5Gr@Cu composite powders were in-situ generated by incubating at 800℃ for 10 min in a mixed atmosphere of 40 sccm H2 and 100 sccm Ar.When the flour content was reduced from 1.0g to 0.5g the in situ generated granbene.transformed from thicker graphene-like nanoplatelets(GLNPs)to thinner transparent graphene.The composite interface of the Gr@Cu composite powder did not have any intermediate phase and was densely connected.Interfacial structures of the graphene-coated copper composite powder have a semi-coherent feature,and the lattice matching was that Gr{002} and Cu{111}match each other.2.The in-situ generation of graphene from flour was divided into two important stages.The first one is the low-temperature stage(up to 400℃),in which H2 reduces the oxide layer(Cu2O)into metallic Cu on the surfaces of the copper powders.The second one is the high-temperature stage(from 400 to 800℃),when the catalytic properties of the copper substrate were used to promote the breaking-up of the chemical bonds of the flour.The carbon atoms were adsorbed on the copper surface due to their high affinity with Cu,and the heteroatoms were removed from the copper surface.When the temperature was decreased,the carbon atoms were recombined to form graphene.3.Gr@Cu/Cu composites with graphene content of 0.35 wt.%,0.70 wt.%and 1.05 wt.%were prepared by wet mixing technology of ultrasonic dispersion at 90 W and 1 h,magnetic stirring at 65℃ and 800 rpm and SPS technology at 650℃,45 MPa and 8 min,respectively.When the graphene content was 0.35 wt.%and 0.70 wt.%,it could be uniformly dispersed in the matrix,and these composites only had copper phase and no intermediate phase was formed.4.The relative density of Gr@Cu/Cu composites was about 99%,and the micro-hardness reached 90～95 HV,which was 15%～22%higher than that of pure copper.The ultimate tensile strength and yield strength obtained by 0.70 wt.%Gr@Cu/Cu composite were 252 MPa and 132 MPa,respectively,which were about 23%and 110%higher than those of pure copper.The elongation could be maintained at around 30%,and the conductivity reached 86%IACS.The 0.70 wt.%Gr@Cu/Cu composite shows a match of high strength,high plasticity,and high electrical conductivity.In-situ generation technology and wet mixing technology improve the agglomeration of graphene in copper matrix,and obtain a pure and strong interfacial structure to provide load transfer.Therefore,the composite material has good strong-plastic matching and high electrical conductivity.更多还原