Abstract
Among titanium alloys with non-toxic elements, the Ti-25Nb-25Ta alloy has good elastic behavior for applications in osseous implants, biocompatibility, and excellent corrosion resistance. The present study aimed to better the biocompatibility characteristics of Ti-25Nb-25Ta alloy modifying its surface through Plasma Electrolytic Oxidation (PEO) treatment. The formed oxide coating is amorphous and composed of two distinct porous formations: smaller hole-shaped pores and larger volcano-like pores. The regions with the formation of smaller pores and in the hole shaped presented the highest atomic percentage of the chemical element phosphorus. Nanoindentation tests have shown that the hardness of the Ti-25Nb-25Ta alloy is slightly lower than the commercially pure grade 2 titanium (a material used as reference), while elastic modulus measurements of Ti-25Nb-25Ta presented more suitable values for implant application (lower values when compared with titanium reference). After PEO treatment there were significant mechanical surface improvements (increased fairly surface hardness and decreased elastic modulus) for application in osseous tissue. Despite the Ti-25Nb-25Ta alloy presented excellent characteristics for applications in hard biological tissues, the PEO treatment better its features.
Highlights
Metallic materials used in biomedical implants are predominant in orthopedic surgical procedures and represent the main function in most orthopedic products [1]
Nanoindentation tests have shown that the hardness of the Ti-25Nb-25Ta alloy is slightly lower than the commercially pure grade 2 titanium, while elastic modulus measurements of Ti-25Nb-25Ta presented more suitable values for implant application
The β phase is a result of the Nb and Ta elements in the Ti-25Nb-25Ta system, which play a role as β stabilizers [42]
Summary
Metallic materials used in biomedical implants are predominant in orthopedic surgical procedures and represent the main function in most orthopedic products [1]. The Ti-6Al-4V alloy was created for use in general structures and later adopted for biomedical applications [10]. This alloy has been questioned mainly by the toxicity of vanadium (V) and aluminum (Al) in the human body [12–14]. CpTi and Ti-6Al-4V elastic moduli are lower when compared with Co-alloys and 316L stainless steel ones, their magnitude is still much superior concerning the cortical bone. As a result, such mismatch may induce bone reabsorption by the stress shielding effect, when implanted in body regions submitted to high and cyclical loads [15-17]. Aiming at rule out these problems, novel alloys were proposed in which niobium (Nb) or tantalum (Ta) substitute the toxic β-stabilizing V [10]
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