Effect of temperature and treatment time of hydrothermal treatment on crystallization of titanium nitride-hydroxyapatite films coated on polyetheretherketone

Abstract

Titanium nitride-hydroxyapatite (TiN-HA) coating via reactive RF MS system with co-axis target is one means of improving the surface properties of polyetheretherketone (PEEK) without changing the bulk material properties. The main factors contributing to the bioactive properties of the coating are the amount and stability of HA crystal. Hydrothermal treatment is recommended for rearranging the HA crystal structure and increasing HA crystallinity in order to enhance the bioactivity and durability of the thin film coating. This study sought to evaluate the optimal conditions for hydrothermal treatment yielding a highly-crystallized HA layer on the surface of PEEK. Hydrothermal treatment at varying temperatures (100, 150 and 200°C) and durations (6, 12 and 24h) was investigated. The surface morphology, chemical composition, and crystallinity of HA in the TiN-HA coating for the different hydrothermal treatment parameters was analyzed using a scanning electron microscope (SEM) and X-ray photoelectron spectrometry (XPS). The SEM revealed a generally rough surface for all groups. HA crystal morphology, including size and microstructure arrangement, was affected differently based on the hydrothermal treatment parameters. The XPS revealed that the Ca:P ratio in the TiN-HA coating neared the stoichiometric ratio of HA (1.67) when the coating was treated at 100°C or 200°C for 12h.