Study on the preparation and mechanical properties of alumina ceramic coating reinforced by graphene and multi-walled carbon nanotube

The paper investigates preparation and mechanical performances of a composite ceramic coating reinforced by graphene and multi-walled carbon nanotube. The carbon nanotube is functionalized with the carboxyl functional group (–COOH) and un-functionalized with sodium dodecyl benzene sulfonate (SDBS). The structure of the functionalized and hybrid-functionalized carbon nanotube is identified using infrared spectroscopy (FTIR analysis). The coating is brushed on the matrix and then cures under temperature lower than 250°C. The morphological and cross section features are studied by scanning electron microscopy (SEM). The distributions of hardness and fracture toughness are determined using a microhardness tester. The adhesive strength is evaluated using a universal tensile tester. The tribological properties are detected using friction wear testing machine. The experimental results show that the structure of the composite coating is compact, and both graphene and hybridtreated carbon nanotube are well dispersed. Addition of 0.2 wt % graphene and 0.2 wt % hybrid-functionalized carbon nanotube results in a prominent increase in hardness and fracture toughness. Meanwhile, the adhesive strength between the composite coating and the metallic substrate is well improved due to the high tensile strength of both graphene and carbon nanotube. Compared with pure alumina coating, the friction coefficient as well as the wear depth and width of grinding crack of the composite coating is much lower.