Tribological behavior of ZnO@GO core-shell nanoparticles as water-based lubricants additive and in composite cobalt-based coatings prepared via cathode plasma electrolysis deposition

• Autor(a) principal: Romero, Manuelle Curbani
• Data de Publicação: 2023
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/17160
• topic: Núcleo-casca; Lubrificantes à base de água; Deposição eletrolítica de plasma catódico; Desgaste deslizante; Revestimentos de cobalto; Óxido de zinco; Óxido de grafeno; subject.br-rjbn; Engenharia Mecânica

Core-shell nanoparticles are hybrid nanostructure. This thesis addresses the electrostatic self-assembly of core-shell nanoparticles with hardcore of ZnO and soft graphene oxide (GO) shells. The assembled structures (ZnO@GO) were used as additive in water-based lubricants and in cobalt-based coatings. In the second chapter, the GO nanoparticles were synthesized and assembled with ZnO using a surface modifier, forming a ZnO@GO core-shell nanostructures. ZnO@GO, GO and ZnO were used as additives in water nanofluids which were wear tested in a ball-on-plate configuration using AISI 52100 as the ball and AISI 304 as the plate. ZnO@GO were efficient in reducing wear by the formation of a GO-rich protective tribolayer. The third chapter regards the production of cobalt coatings by cathodic plasma electrolytic deposition (CPED). The deposition mechanism and the effect of polyethylene glycol (PEG) on it are discussed. CPED was efficient in forming nanocrystalline and wear-resistant coatings. PEG decreased the current needed for deposition and affected the thickness and morphology of coatings, while not altering wear or friction. In the fourth chapter, the ZnO@GO nanoparticles were added to the electrolytic bath forming a composite cobalt-based coating. Coatings were tested against an AISI 52100 ball in sliding wear tests. Nanoparticles increased coatings hardness and decreased surface roughness. Composite coatings had a superior tribological performance when compared to pure Co-coatings due to the entrapment of exfoliated GO nanoparticles on the wear track, protecting the surface.