Fabrication of thin film TiO2 nanotube arrays on Co-28Cr-6Mo alloy by anodization

Abstract

Titanium oxide (TiO2) nanotube arrays were prepared by anodization of Ti/Au/Ti trilayer thin film DC sputtered onto forged and cast Co-28Cr-6Mo alloy substrate at 400 °C. Two different types of deposited film structures (Ti/Au/Ti trilayer and Ti monolayer), and two deposition temperatures (room temperature and 400 °C) were compared in this work. The concentrations of ammonium fluoride (NH4F) and H2O in glycerol electrolyte were varied to study their effect on the formation of TiO2 nanotube arrays on a forged and cast Co-28Cr-6Mo alloy. The results show that Ti/Au/Ti trilayer thin film and elevated temperature sputtered films are favorable for the formation of well-ordered nanotube arrays. The optimized electrolyte concentration for the growth of TiO2 nanotube arrays on forged and cast Co-28Cr-6Mo alloy was obtained. This work contains meaningful results for the application of a TiO2 nanotube coating to a CoCr alloy implant for potential next-generation orthopedic implant surface coatings with improved osseointegrative capabilities.

Keywords: Anodization; CoCr alloy; Next-generation orthopedic implant; TiO(2) nanotube.

Figure 1

Schematic diagrams of two different deposition structures on Co-28Cr-6Mo alloy substrate: (A) Ti/Au/Ti trilayer; (B) Ti monolayer.

Figure 2

Corresponding current density vs. anodization time curve of anodization process of Ti/Au/Ti trilayer at 400 °C (divided into three regions).

Figure 3

The SEM images of the surface morphology of Ti/Au/Ti thin film on forged Co-28Cr-6Mo alloy disc samples sputtered at different deposition temperature: (A) at 400 °C, (B) at room temperature; and the surface SEM images of TiO₂ nanotube arrays anodized Ti/Au/Ti thin film on Co-28Cr-6Mo alloy disc samples sputtered at different deposition temperature: (C) at 400 °C, (D) at room temperature.

Figure 4

The surface SEM images of Ti/Au/Ti thin film on forged Co-28Cr-6Mo alloy disc samples sputtered at 400 °C after anodization in 5 vol% H₂O and 95 vol% glycerol including different content of NH₄F: (A) 2.0 wt%, (B) 2.5 wt%, (C) 3.0 wt%, (D) 4.0 wt%, (E) 5.0 wt%. The insets depict cross-sectional views.

Figure 5

The surface SEM images of Ti/Au/Ti thin film on forged Co-28Cr-6Mo alloy sputtered at 400 °C after anodization in 2.5 wt% NH₄F and 95 vol% glycerol including different content of H₂O: (A) 2.5 vol%, (B) 5 vol%, (C) 6 vol%, (D) 7 vol%. The insets depict cross-sectional views.

Figure 6

SEM micrographs of HOb cells after 24 h incubation on the flat CoCr substrate (A and C) and TiO₂ nanotube substrate (B and D). Image (B) indicates cell elongation in response to the nano topography; image (D) shows extensive filopodia activity on the nanotube surface (yellow arrows).