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Reactivity of XPS Ion-etched CoCrMo and TiAlV alloys in physiological medium
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
2009 (English)Conference paper, Poster (Other academic)
Abstract [en]

Introduction: Osteolysis induced by wear particles in metal-on-polyethylene hip implants has been the key motivation to look for alternative bearings and in fact emergence and development of new metal-on-metal (MOM) implant materials for joint replacement. However, while the volume of wear particles produced in metal-on-metal articulations is lower in MOM implants, it is clear that the smaller size of the metal wear particles has a dramatic effect on the number of particles produced per unit volume of wear. Although various surface and interface characterization methods have been applied to study the physical wear, corrosion and implant surface interactions with biological environments, presently the local and systematic effects of metal debris in body are poorly understood. Materials and Methods: Cobalt-chromium-molybdenium (CoCr) and titanium-aluminum-vanadium (TiAlV) alloys have been used in MOM implants extensively. Metallic samples were cut and mirror polished. In the present study the samples were immersed in four different biological lubricants (Human serum, synovial fluid and MEM) for 10 min, 1 hr, and 5 days of immersion and then studied by X-ray Photoelectron Spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). XPS determined the chemistry of elements located whit in the top few nanometers of materials. Significant differences in the absorbed layers and differences in the corrosive nature of CoCr implant substrates immersed in different media were found. Results and discussion: Spectra from P2p3/2, O1s, Ca2p3/2, C1s and N1s were collected. Metallic substrates behaved differently when immersed in the same lubricant for different time intervals. The three lubricants reacted different with metallic surfaces. Larger calcium deposits occurred in supersaturated physiological solutions. Deposition of calcium phosphate was different on CoCr and TiAlValloys depending on the lubricant and the immersion period. Specimens immersed into synovial fluid gave thinner oxide layers and lower calcium phosphate deposits. For all specimens, water immersion resulted in thicker oxide layer. Conclusion: Passivation of the metal surface is fundamental to corrosion resistance where a metallic oxide (like chromium oxide) barrier protects the underlying metal from further corrosion. The amount and purity of the oxide layer on immersed specimens depends on the density and thickness of the overlying deposits of calcium phosphate (Figure 1), proteins and other adsorbed molecules, as well the contaminations. The ration of Cr2O3 to Cr was calculated for CrCo alloy and was related to the thickness and/or concentration of the oxide in different lubricants. The lower calcium phosphate deposit in synovial fluid might be due to the present of components such as GAG and associated proteins, which stop the calcium deposition due to the circulation of the fluid in the effective joint space. ToF-SIMS measurements showed that the resulting corrosion products depend upon the nature of the environment. The thickness of the calcium phosphate deposits was different for different metal substrate.

Place, publisher, year, edition, pages
Research subject
Machine Elements
URN: urn:nbn:se:ltu:diva-40190Local ID: f37ef060-a831-11de-8293-000ea68e967bOAI: diva2:1013713
European Conference on Biomaterials : 07/09/2009 - 11/09/2009
Godkänd; 2009; 20090923 (emami)Available from: 2016-10-03 Created: 2016-10-03Bibliographically approved

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