Physicochemical properties of a Ti67 alloy after EO and steam sterilization

Abstract

The techniques of surface modification play a significant role in forming the physical and chemical properties of titanium and its alloys. Among many techniques for the layers' application, chemical and electrochemical methods are particularly interesting, as they make it possible to control the process of depositing thin layers of the material and modifying their properties through a change of reagents and the parameters of the deposition process. A special advantage the methods bring is the possibility to obtain layers that offer a perfect coating for geometrically complex surfaces. Apart from improved haemocompatibility, a significant issue related to the creation of the layers is also a proper set of physicochemical properties. Therefore, the study comprised tests of the physicochemical properties of oxide layers deposited on the surface of samples taken from a Ti-6Al-7Nb alloy. The samples were subject to various surface modifications, i.e., grinding, electrolytic polishing, a SiO2 layer was applied using the sol-gel method and TiO2 by means of an anodic oxide and medical sterilisation methods (EO and steam). The corrosion-resistance tests were performed on the basis of registered anodic polarisation curves and the Stern method. Electrochemical Impedance Spectroscopy (EIS) was also used in order to evaluate the phenomena taking place on the surface of the tested alloys. As a part of the evaluation of the mechanical properties of surface layers created in such a way, hardness tests and tests of the adhesion of those layers to a metallic substrate were made. Measurements of the instrumental hardness were made with the Oliver & Pharr method, whereas the adhesion of the layers to the substrate was measured by means of a scratch test. The suggestion of proper surface treatment variants has perspective significance and will help to develop the technological conditions with specified parameters of the oxide coating's creation on the surface of metallic implants. Keywords: Ti-6Al-7Nb (Ti67) alloy, sol-gel, anodic oxide, scratch-test, nanohardness, EIS, potentiodynamic method Tehnike modifikacije povr{ine igrajo pomembno vlogo pri doseganju fizikalnih in kemijskih lastnosti titana in njegovih zlitin. Med mnogimi tehnikami uporabe tankih plasti so {e posebej zanimive kemijske in elektrokemijske metode, ker omogo~ajo kontrolo postopka depozicije tanke plasti materiala in spreminjanje njihovih lastnosti, z zamenjavo reagentov in parametrov procesa depozicije. Posebna prednost, ki jo omogo~ajo metode, je mo`nost izdelave plasti, ki omogo~ajo popolno prevleko pri geometrijsko kompleksnih povr{inah. Poleg izbolj{ane hemokompatibilnosti je pomembno vpra{anje povezano z nastankom plasti in tudi z doseganjem ustreznih fizikalno kemijskih lastnosti. Zato je {tudija obsegala preizkuse fizikalno kemijskih lastnosti oksidnih plasti, po depoziciji na povr{ini vzorcev iz Ti-6Al-7Nb zlitine. Na vzorcih so bile opravljene razli~ne modifikacije povr{ine: bru{enje, elektrolitsko poliranje, SiO2 plast, izdelana po sol-gel postopku in T...

Archives of Metallurgy and Materials

“…The use of the synthetic Al 2 O 3 with a grain size 250 μm after the surface modification by the sol-gel method, results in obtaining a tight ZrO 2 layer, which is a good barrier against the corrosive environment. Additionally, based on the obtained results and literature dates it can be concluded, that the pitting corrosion resistance increase with the deposited on the surface of the Ti-6Al-7Nb alloy the thin layer by the sol-gel method [5,7,11]. Moreover, regardless of type of the initial surface treatment, the micro-crack of the oxide layer was observed, which does not affect the quality of the obtained layers.…”

“…The oxide layer deposited by this method are characterized by control chemical composition and microstructure, which thickness exceeds the value 1 μm. Additionally, one of the advantages of sol-gel method is the possibility to create independently the hydroxyapatite on the deposited layers due to the interaction with the physiological fluid [9][10][11][12][13]. For this purpose, the zirconium oxide in one of the most popular layer used in sol-gel method.…”

Archives of Metallurgy and Materials

“…The surface of ZrO 2 , whose oxides are present in three crystallographic variants, the most advantageous of which is high temperature one, because of its better mechanical properties, which are measured by high hardness, good bending strength and elasticity in cracking. In addition, it has very good anticorrosive properties, which translates into high biocompatibility [1,4,17].…”