Preparation,Microstructure And Properties Of Graphite(Graphene)/Copper Composites

Copper and its alloys have high electrical conductivity,thermal conductivity,corrosion resistance and excellent processing properties,and are widely used in electronic materials,thermal resistance materials,brush materials and other fields.Graphite and graphene have also been studied extensively as reinforcements for copper-based composites for their unique structure and properties.However,the interfacial wettability between carbon and copper is poor,and graphene is difficult to uniformly disperse in copper matrix because of its large surface areaes.It is also difficult to obtain a high density graphite?graphene?/copper composite material by the conventional powder metallurgy method.This dissertation attempts to prepare graphite?graphene?/copper composite powders with coating structure by electroless plating and preparing graphite?graphene?/copper composite with uniform microstructure;and explores the influence of the electroless plating process on the morphology of the coated powders.The microstructure,interface structure and physical and mechanical properties of the composites were investigated and compared with those of the composites prepared from the mechanically mixed copper and graphite?graphene?powders.This work is helpful to the development of graphite?graphene?/copper matrix composites with high performance.The main results obtained in this work are concluded as followings.Graphite and CuSO₄·5H₂O were used as the main raw materials to prepare graphite/copper composite powders with coating structure by electroless plating.The effects of compositions in the plating solution,plating parameters on the morphology and properties of the graphite/copper composite powders were investigated.The optimum plating conditions are as follows:formaldehyde 40g/L,CuSO₄·5H₂O 14.7g/L,graphite0.6g/L,plating time 30min.The prepared graphite/copper-coated powders contain a little Cu₂O impurities,which can be reduced into copper at 350^oC in H₂ atmosphere.The prepared graphite/copper-coated powders and copper powders are used as the main raw materials to prepare graphites/copper powder mixes with different graphite contents?0.5wt%,1wt%,2wt%,and 3wt%?are obtained by ball mixing.The mixed powders were pressed and sintered to obtain graphite/copper composites.Microstructure and properties of the composites were investigated and compared with those of the composites prepared from the mechanically mixed copper and graphite powders.The results show that the performance of graphite/copper composites prepared from copper-coated graphite powders are better than those of composites from the mechanically mixed powders.The composite materials prepared by electroless plating not only avoids the agglomeration of graphite in the microstructure,but also improves the interfaces between graphite and copper.The graphite/copper composite with a graphite addition amount of 2wt%was prepared by this method and its electrical conductivity and Vickers hardness were 70.95%IASC and 66.8 HV,respectively.Graphite/copper composites with a graphite content of 2wt%prepared from raw material graphite,its conductivity and Vickers hardness were 63.23%IACS and 59.2 HV,respectively.The graphite/copper composites prepared by electroless plating method show better comprehensive performance.Reduced graphene oxide?RGO?and CuSO₄·5H₂O were used as raw materials,and copper-coated graphene?RGO/Cu?composite powders were obtained by electroless plating.The obtained RGO/Cu composite powders were mixed with electrolysis copper powders to obtain RGO/Cu powder mixes with different RGO contents?0.2wt%,0.4wt%,0.6wt%,0.8wt%?.Graphene/copper?RGO/Cu?composites were prepared by pressing and sintering the powder mixes.The RGO/Cu composite powders and the RGO/Cu composites were characterized by XRD,Raman spectroscopy and scanning electron microscopy?SEM?and compared with RGO/Cu composites prepared from powder mixed of Cu and unplated RGO powders.The results show that the copper coated RGO powders disperse uniformly in the composites,while the uncoated RGO agglomeration seriously in the Cu matrix.The mechanical properties of the composites improve with the addition of RGO,while electrical and thermal conductivity of the RGO/Cu composites decreases with the increase of RGO content.Properties of the RGO/Cu composites prepared from the electroless plated RGO are better than those from the unplated RGO.Maximum comprehensive performances were obtained for RGO/Cu composites with 0.4%addition of RGO and compressive yield strength reaches 156.73 MPa,which increases by 109%compared with the pure copper yield strength?75MPa?obtained under the same conditions,the electrical conductivity reaches 95.01%IACS and the thermal conductivity is 415.5 W·?m·K?^-1.