Effect of the Hydrothermal Heat Treatment Conditions of Titanium Substrates on the Bio-Mimetically Grown 'Bone-Like' Apatite Coatings

摘要

Hydrothermal surface modifications of the titanium specimens were performed (i) at 200 °C under 1.5 MPa pressure, and (ii) at 230 °C under 2.5 MPa pressure. To see the effect of an ion implantation, two different aqueous hydrothermal environments were selected: (i) de-ionized water and (ii) calcium containing de-ionized water. Hydrothermally treated titanium surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and found to become rich with Ca when Ca-containing hydrothermal environment was used. The surface-modified titanium specimens were then kept immersed in 1.5X simulated body fluid (SBF) for 1, 2, 3 and 4 weeks. The bio-mimetically formed coatings were characterized using scanning electron microscopy (SEM) and X-ray diffractometer (XRD). Crack formations and, consequently, severe peelings were observed after drying for all the coatings on the substrates that were treated hydrothermally using only de-ionized water. The Ca implanted titanium surfaces, on the contrary, were able to develop crack-free and quite cohesive coatings. Up to two weeks of immersion and after drying, no-cracks were observed in the coatings when the substrates were treated at higher temperature and under higher pressure (230 °C and 2.5 MPa for the present investigation).