New PhD Project Offers
2012-15-EM Nanostructured and amorphous alloys functionalized stainless steel surfaces for biomedical use (IST-ICEMS, INPG-LEPMI)
This project aims to develop advanced non-toxic bio-compatible coatings based on nanostructured or amorphous alloys as new high-end, cost-effective coatings for biomedical implants using multidisciplinary state-of-the-art science and technology. Potential future break-through applications are cost-effective, non-toxic new medical implants that reduce the cost of health care for senior citizens as well as bone fracture treatment in younger age groups and children.
Due to the ageing of population and increased incidence of traffic and sport accidents at younger ages, skeletal injuries and disorders will affect 25% of the population in Europe and represent a significant proportion of the total European expenditure in medical care. Despite this, only limited technological and clinical breakthroughs have been achieved in the past decades in materials development for permanent implants for oral implantology and orthopaedics.
Stainless steels are being currently used for orthopaedic or dental implants due to their excellent mechanical properties, corrosion resistance and low cost, compared to titanium or platinum alloys. Moreover, their ductility and formability allows reducing the production costs as compared to Ti and Co-Cr alloys. They have, nevertheless, some limitations of biocompatibility and include in their constitution Ni, which is a well known allergenic for a significant proportion of the human population. Indeed, there is usually a contradiction between anticorrosive properties and acceptable bioactivity of implanted materials, the two extremes of very low and very high bioactivity and corrosion resistance leading respectively to non-integration and dissolution of metallic implants in the body, potentially releasing toxic elements. This proposal hence aims to mitigate this problem by the development of low cost metallic implant materials obtained by coating medical grade austenitic stainless steels with nanostructured or vitrified coatings of materials with outstanding corrosion resistance and biocompatibility. This combination of materials is expected to establish a better compromise between surface properties as corrosion resistance, bioactivity and biocompatibility and bulk properties, such as toughness, fatigue resistance and mechanical strength at a reasonable cost.
Project Partners and their Roles
The work will be shared between the two Universities as follows:
(a)IST has considerable experience in laser-assisted surface engineering. Laser-based methods allow synthetizing coating materials rapid and efficiently and generating the very high cooling rates required to produce nanostructured and amorphous materials. In the present work medical grade stainless steels will be coated with alloys such as Fe66B30Nb4 and [(Fe0.6Co 0.4)0.75B0.2Si0.05]96Nb4 by laser cladding (a process leading to coatings with thickness in the range 0.1-1.0 mm) and laser PVD (coating thickness in the 1-10 micron range). The coatings will be characterised by X-ray diffraction, scanning electron microscopy/EDS/EBSD and, if required, transmission electron microscopy. The coating process results will be optimised taking into consideration the results achieved in order to obtain materials with the best corrosion resistance and biocompatibility. A special attention will be given to the optimisation of the structure of the substrate coating/interface, in order to ensure long-term adhesion and stability of the coating, thus avoiding contamination of body tissues by detached metal particles. Whenever required the coatings will be surface remelted in order to ensure chemical and structural homogeneity and the complete amorphisation of the material.
(b)At Grenoble in LEPMI (Laboratory of Electrochemistry and Physico-Chemistry of Materials and Interfaces, UMR 5279 CNRS, Grenoble – INP, UJF), the samples will be studied in terms of their electrochemical behaviour (corrosion resistance and alloying elements release). The development of new coating alloys will also be considered in collaboration with SIMAP laboratory at Grenoble – INP. Different characterization techniques as XPS (X-ray photo-electron spectrometry), SEM (scanning electronic microscopy), XRD (X-ray diffraction), and TEM (transmission electronic microscopy) will be employed so as to characterize corrosion process and coating microstructures.
This project will be conducted in close collaboration with Ugitech (www.ugitech.com), which provides special stainless solutions for extreme conditions applications.