Improving the Tribological Properties and Biocompatibility of Zr-Based Bulk Metallic Glass for Potential Biomedical Applications.

Victoria Sawyer,Huan Dong,Behnam Dashtbozorg,Xiao Tao,Rachel Sammons,Han-Shan Dong,Xiaoying Li

doi:10.3390/ma13081960

Abstract

Zr-based bulk metallic glasses (Zr-BMGs) are potentially the next generation of metallic biomaterials for orthopaedic fixation devices and joint implants owing to their attractive bulk material properties. However, their poor tribological properties and long-term biocompatibility present major concerns for orthopaedic applications. To this end, a novel surface modification technology, based on ceramic conversion treatment (CCT) in an oxidising medium between the glass transition temperature and the crystallisation temperature, has been developed to convert the surface of commercially available Zr44Ti11Cu10Ni11Be25 (Vitreloy 1b) BMG into ceramic layers. The engineered surfaces were fully characterised by in-situ X-ray diffraction, glow-discharge optical emission spectroscopy, scanning electron microscopy, transmission electron microscopy, and scanning transmission electron microscopy. The mechanical, chemical, and tribological properties were evaluated respectively by nano-indentation, electrochemical corrosion testing, tribological testing and the potential biocompatibility assessed by a cell proliferation assay. The results have demonstrated that after CCT at 350 °C for 40 h and at 380 °C for 4.5 h the original surfaces were converted into to a uniform 35–55-nm-thick oxide layer (with significantly reduced Ni and Cu concentration) followed by a 200–400-nm-thick oxygen-diffusion hardened case. The surface nano hardness was increased from 7.75 ± 0.36 to 18.32 ± 0.21 GPa, the coefficient of friction reduced from 0.5–0.6 to 0.1–0.2 and the wear resistance improved by more than 60 times. After 24 h of contact, SAOS-2 human osteoblast-like cells had increased surface coverage from 18% for the untreated surface to 46% and 54% for the 350 °C/40 h and 380 °C/4.5 h treated surfaces, respectively. The significantly improved tribological properties and biocompatibility have shown the potential of the ceramic conversion treated Zr-BMG for orthopaedic applications.

Highlights

Metallic biomaterials are widely used for orthopaedic applications such as joint replacements, intramedullary nails and plates for fracture fixation, mainly due to their desirable combination of mechanical properties together with adequate biocompatibility.stress shielding and metal ion release have presented major concerns for the safety and longevity of orthopaedic fixation devices and load-bearing implants with metallic components [1,2,3]
An in-situ XRD analysis was first performed on Vitreloy 1b (Vit1b) during oxidation at 380 ◦ C for 24 h
A novel ceramic conversion treatment has been developed based on thermal oxidation at 350 ◦ C for 40 h (350-40) and at 380 ◦ C for 4.5 h (380-4.5) to modify the surface properties and performances of a commercial Zr-based bulk metallic glass Vit1b Zr44 Ti11 Cu10 Ni11 Be25

Summary

Introduction

Metallic biomaterials (such as stainless steel, Co-Cr and Ti alloys) are widely used for orthopaedic applications such as joint replacements, intramedullary nails and plates for fracture fixation, mainly due to their desirable combination of mechanical properties together with adequate biocompatibility.stress shielding (associated with their high Young’s modulus) and metal ion release (stimulated by tribocorrosion) have presented major concerns for the safety and longevity of orthopaedic fixation devices and load-bearing implants with metallic components [1,2,3]. Brown et al [4] demonstrated in their in vivo study on intramedullary rods implanted in rabbits that fracture remodelling was adversely affected by the metallic rods and cortical bone resorption was observed in the fracture region. No such complications were observed when using polyacetal or polyamide rods with much lower elastic modulus at 3 and 2 GPa, respectively. This proved that the occurrence of stress shielding to the diaphysis was caused by the stiff metal rods used [4]. In a further in vivo research on the levels of metal ions in patients implanted with

Results

Discussion

Conclusion