Effect of Dynamic Chemical Etching on the Pore Structure, Permeability, and Mechanical Properties of Ti-Nb-Zr Scaffolds for Medical Applications

Abstract

Improving the post-processing of metallic porous tissue scaffolds is an essential step to create a new generation of superelastic implants for the replacement of damaged bone tissue. In this study, the dynamic chemical etching technique is applied to improve the permeability and to optimize the porous structure of Ti-Nb-Zr scaffolds fabricated by the powder metallurgy-based space holder technique. The etched scaffolds are characterised in terms of their porous structure geometry, permeability, and mechanical properties. It is shown that an increase in porosity from 49% to 54% during the etching is mainly due to an increase in the number of 100 to 800 µm-diameter pores; from 30 to 50% of them measuring from 100 to 300 µm in size. These changes in the porous structure lead to a significant increase of its permeability, i.e. from (0.1-15)×10−11 m2 before etching to (44-91)×10−11 m2, after etching; these permeability ranges corresponding to those of bone tissues. Furthermore, the etched scaffolds show systematically higher yield compressive stresses as compared to the as-sintered scaffolds of equivalent porosities. Finally, the highly-permeable etched Ti-Nb-Zr scaffolds with a porosity varying from 40 to 60% exhibit an apparent Young’s modulus ranging from 8.6 to 1.9 GPa, and an ultimate compressive strength, from 650 to 190 MPa, which can be considered as a promising balance of properties for the potential use of these scaffolds as bone implants.

Complete Removal of Residual Particles and Realization of Mechanical Properties to Improve Osseointegration in Additively Manufactured Ti6Al4 V Scaffolds through Flowing Acid Etching

“…30,31 However, the discrepancy between the internal and external surfaces of the scaffolds was not entirely resolved after dynamic chemical etching. Sheremetyev et al 32 proposed a different dynamic acid etching process to treat Ti−Nb−Zr scaffolds fabricated by the space holder technique. By pumping the acidic solution flowing through the scaffold, the loosely attached Ti particles inside the scaffolds were removed, and the porosity and permeability of the bone scaffold were enhanced.…”

“…Dynamic chemical polishing technology, which induced magnetic stirring in the chemical etching treatment, improved the surface treatment effect, internal and external homogeneity, and mechanical properties of the Ti64 scaffolds. , However, the discrepancy between the internal and external surfaces of the scaffolds was not entirely resolved after dynamic chemical etching. Sheremetyev et al proposed a different dynamic acid etching process to treat Ti–Nb–Zr scaffolds fabricated by the space holder technique. By pumping the acidic solution flowing through the scaffold, the loosely attached Ti particles inside the scaffolds were removed, and the porosity and permeability of the bone scaffold were enhanced.…”