Characterization of Ti-Based Foams for Biomaterials Applications

Abstract

Development of titanium foams with low elastic modulus has increased its scientific and technological relevance due to the evident need to avoid the stress shielding problems related to stiffness mismatch with respect to bone. In this work we studied the synthesis and characterization of foams of pure Ti which present high potential for biomedical applications. Foams were obtained using NaCl (40, 50 and 60 %v/v), with particle size ranging from 150 to 350 mm, as space-holder. Powders and space-holder were mixed together and compacted under 200 to 800 MPa stress. NaCl particles were removed from the green compacts by submerging samples in distilled water at 60 °C (5 cycles of 4h). The green compacts were sintered at 1300 °C for 3 h in Ar atmosphere. Ti-based foams were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, optical microscopy. In addition, electrochemical impedance spectroscopy (EIS) measurements were performed under potentiostatic conditions at the corrosion potential in Ringer solution. Results showed that Ti-based foams with tailored heterogeneous pore distribution may be obtained using space holder method. Using theoretical models the elastic modulus of foams was estimated between 10 and 25 GPa. The experimental EIS data revealed a CPE behavior of the foams for all exposure time studied. Not significant effect was observed in the impedance modulus at low frequency range (|Z|LF) for low compaction stress. However, the |Z|LF decreased markedly for higher compaction stress, which could be related to the increase of the stress raiser. From our results, we conclude that foams with 50 and 60 % of porosity are potential bone replacement materials due to their stiffness closer to human bone value. Ackowledgements: The authors are grateful to Fondecyt Grant 1160604 and 1161444