Mechanical properties of titanium-niobium alloy and morphological characterization of nanotubes obtained by anodizing technique

Abstract

Event Abstract Back to Event Mechanical properties of titanium-niobium alloy and morphological characterization of nanotubes obtained by anodizing technique Aline Rossetto Da Luz1, Neide Kazue Kuromoto1, 2 and Carlos Maurício Lepienski1 1 Universidade Federal do Paraná, Programa de Pós-Graduação em Engenharia e Ciência dos Materiais - PIPE, Brazil 2 Universidade Federal do Paraná, Física, Brazil Introduction: Titanium and titanium alloys are the metals used to produce metallic biomaterials. The alloy frequently used for orthopedic prostheses is the Ti-6Al-4V. However, there has been toxic effects due to the release of aluminum and vanadium ions. There are studies being directed on developing new alloys, specifically the type β-Ti alloys containing Nb, Mo, Zr, Sn or Ta, which are considered non-toxic, corrosion resistant and have mechanical properties suitable for biomaterials[1]. Nanotubular surface modification of metallic implants by the anodizing technique can improve the biocompatibility when compared to conventional materials[2]. The purpose of this study was to determine the elastic modulus of the Ti-20Nb and obtain the growth of the nanotubes over the binary alloy by anodization technique. Materials and Methods: The precursor materials used were commercially pure titanium grade 2 (cp-Ti) with 99.7% purity and niobium (Nb) with 99.8% purity. For the fusion of elements it was used an arc-melting furnace with copper crucible water cooled, non-consumable tungsten electrode and an argon-controlled atmosphere. Titanium ingots with a weight percentage of 20 wt. (%) of Nb were obtained after melting process[3]. Disks with 9 mm of diameter and 2 mm of thickness were polished with a suspension of 0.05-mm colloidal SiO2. The samples were ultrasonically cleaned in acetone, isopropyl alcohol and deionized water, and dried at 40 °C for 24h. The microstructure of the chemically etched alloys was analyzed using optical microscope. The elastic modulus of the Ti-20Nb alloy were obtained by instrumented indentation by Oliver-Pharr method[4]. The nanotubes were obtained using anodic oxidation technique under potentiostatic mode in 0.5 M Na2SO4 + 0.1 wt.% HF electrolyte, using voltage of 20 V and anodizing time of 1.5 h, at room temperature. A platinum sheet was used as the counter-electrode. The morphology of the nanostructured surface was analyzed using scanning electron microscopy. Results and Discussion: Optical microscope analysis of the Ti-20Nb alloy showed a structure composed of α’/α” phases and the metastable β phase. Figure 1 shows the elastic modulus value of the Ti-20Nb alloy is of (103 ± 2) GPa at greater depth (~ 2560 nm), which is smaller than the value of cp-Ti that is 130 GPa. This decrease in the elastic modulus is due to the presence of the β phase and can reduce the effect of stress shielding between implant and bone tissue. Figure 2 shows the surface morphology of the anodized Ti-20Nb alloy, highly ordered titania nanotubes were produced. This morphology can improve osteoblasts adhesion ability and osseointegration compared to metal implants without surface treatment[2]. Conclusion: The adding niobium as β stabilizing element reduced significantly the elastic modulus, compared to cp-Ti. An ordered titania nanotube arrays successfully were obtained on the Ti-20Nb alloy, by anodization technique. We would like to thank the Center of Electron Microscopy - UFPR and the Labnano - UFPR for the facilities, and the CAPES for the financial support.