FORMATION OF GRAPHENE SHEETS ON COPPER FILMS FOR TRIBOLOGICAL APPLICATIONS

• Grant number: 23/07548-3
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Effective date (Start): July 01, 2023
• Effective date (End): June 30, 2025
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Andre Paulo Tschiptschin
• Grantee: Michell Felipe Cano Ordonez
• Host Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 19/18572-7 - New carbon materials: their relevant space, environmental and relevant spin off applications, AP.TEM

Abstract

The global trend of developing new technologies seeks to reduce the energy losses of mechanical systems sustainably. In passenger transport vehicles, these friction losses are equivalent to 33% of fuel consumption. One way to mitigate these losses is through surface engineering, which allows the development of solutions such as lubricating coatings that can reduce the coefficient of friction to levels below 0.01 under boundary conditions o or dry lubrication. One of the most promising materials for significantly reducing friction is graphene, whose high mechanical properties and structural characteristics confer superlubricity and allow friction and wear control at multiple scales, from nano to macro. However, the real challenge in using this material lies in the ability to safely transfer the synthesized layers to a final substrate. This transfer process can induce defects in the crystalline structure of graphene lamellae, which can reduce their tribological performance. Thus, in this project, the production conditions of graphene layers synthesized in situ and in operation on systems with copper/amorphous carbon (Cu/a-C) coatings will be studied without the need to transfer the graphene from the production substrate to the component of use. The synthesis of the a-C and Cu layers will be carried out by the physical vapor deposition technique, using a reactor in the pulsed DC Magnetron Sputtering (pDCMS) mode. After the deposition process, the surfaces are subjected to an annealing process at high temperature with a mixture of Ar and H2, to obtain the initial graphene sheets. The chemical composition and structure of the layers will be analyzed using Raman spectroscopy techniques, X-ray diffraction, scanning electron microscopy with a field effect gun, optical interferometry, and mechanical characterization by nanoindentation and scratching tests. Tensile tests will be performed in conjunction with the Raman spectroscopy technique to assess fracture toughness and residual stress. Tribological tests will be carried out to determine the conditions under friction or superlubricity in the sphere-plane configuration in a universal tribometer. It is expected from the results of the tribological evaluation that variations in friction are proportional to the cyclic formation of graphene sheets, which allows the evolution of a self-lubricating tribofilm that reduces friction and surface wear