Fabrication et caractérisations électriques et mécaniques d'un composite cuivre - carbone à architecture 3D

The aim of this thesis is to study the electrical and mechanical properties of copper-graphene composites. The scientific literature has shown, both experimentally and numerically, that it is possible to dop electrical properties with graphene, provided that a monolayer or even a bilayer of graphene is present at the interface with the copper. However, this was only achieved using a process that produced an anisotropic material. This process involved depositing graphene on micrometre-thick sheets of copper, stacking them and then hot-pressing them. Other processes have been developed to obtain graphene at grain boundaries by sintering powders previously coated with graphene. Similarly, the mechanical properties of a copper/graphene composite are improved by the carbon blocking dislocations at the grain boundaries. Combining copper and carbon to produce a material that improves the mechanical and electrical properties of copper is a complex task. Carbon is virtually insoluble in copper.So we need to be able to master a process that can produce a dense, isotropic material that improves both electrical and mechanical properties. There is a wealth of manufacturing processes in the scientific literature. The one chosen for this project was powder metallurgy. A micrometric copper powder is coated with a precursor containing carbon, in this case sucrose. Two approaches have been used, the first involving coating raw particles with an oxide layer and the second involving coating particles after first reducing the oxide. This coated powder is then burnt in an optimised atmosphere of argon and hydrogen. The powder obtained is finally sintered to produce the composite. The resulting composite is then studied using standard metallurgical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), X-ray diffraction (XRD) and Raman spectroscopy to characterise the carbon. All these techniques are aimed at understanding the interaction between copper and its carbon reinforcement.