Tribo-Mechanical, Biocompatibility, and Corrosion Properties Investigation of Zirconium and SST 304 by Application of Hydroxyapatite/Reduced Graphene Oxide/Palladium-Platinium Nanocomposite Coatings

Abstract

This thesis describes the synthesis of HA/rGO/Pd and HA/rGO/Pt nanocomposite thin film coatings on stainless steel 304 and pure zirconium applied via an electrodeposition method. The corrosion and biocompatibility characteristics of HA/rGO/Pd and HA/rGO/Pt nanocomposite thin films are investigated here. Biocompatibility tests were carried out on uncoated, HA-coated, HA/rGO-coated, HA/rGO/Pd-coated, and HA/rGO/Pt-coated substrates using the human cell line MDA-MB-231, which had a green fluorescent protein to report the presence of living cells. Experiments revealed that the biocompatibility of the SST 304 surface showed the best cell spreading and proliferation when coated with the HA/rGO/Pd nanocomposite. The zirconium substrate coated with HA/rGO/Pt showed decreased cell proliferation and adhesion compared with HA/rGO, showing that Pt did not improve the biocompatibility. A synthetic medium was used to conduct corrosion tests, which confirmed that the HA/rGO/Pd-coated SST 304 had a significantly higher corrosion resistance than the uncoated, HA-coated, and HA/rGO-coated SST 304 samples. In addition, the HA/rGO/Pd-coated SST 304 and the HA/rGO/Pt-coated zirconium substrates were annealed at different temperatures (200, 300, 400, and 600 oC) to investigate their corrosion and wear behaviors. The HA/rGO/Pd-coated substrate annealed at 600 °C showed better wear resistance compared with the other samples. The wear tests result of bare and electrodeposited specimens before and after heat treatment for the HA/rGO/Pt showed that the coated samples heated at 300 °C had superior resistance against wear compared with bare and electrodeposited substrates at other annealing temperatures.