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Combinatorial coating development of Si-N-Fe-C coatings for joint implants
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Material i Medicin gruppen. (Biomaterial Systems)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Material i medicin)ORCID iD: 0000-0001-9529-650X
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Biomaterial Systems)ORCID iD: 0000-0001-6663-6536
2018 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

INTRODUCTION

Joint replacements of hip and knee are generally considered successful procedures, with a survival rate of approximately 95% after 10 years. However, the increasing, more active elderly population puts higher demands on implants, which need to last longer. Some of the main limiting factors for the longevity of these implants are the generation of wear debris and release of metal ions. These wear particles and ion release could be reduced with the use of ceramic coatings e.g. silicon nitride. Silicon nitride coatings have in laboratory investigations been shown to reduce the wear rate1 and act as a barrier for metal ions and therefore warrant further investigation for use in joint implants. An addition of the biocompatible elements Fe and C could be used to tune the dissolution rate and increase the deposition rate.

METHODS

Coatings were deposited on silicon wafer substrates using magnetron co-sputtering. The targets used were Si (99.99%purity) powered by a pulsed DC aggregate at 200 W, 200 kHz and 2µs. The two other targets C and Fe were powered by DC aggregates at 65 W and 25 W respectively. During deposition N2 was introduced as reactive gas. Elemental gradients were obtained by angling of the targets and the use of no rotation.

The coatings were investigated using elastic recoil detection analysis (ERDA), atomic force microscopy (AFM), scanning electron microscopy (SEM) and nanoindentation in five different points on the sample. The different points were chosen at coordinates (0,0), (0,40), (40,0), (40,40) and (20,20) based on a coordinate system with origin in the lower left corner.

The cytotoxicity of the coatings was evaluated in vitro with mouse osteoprogenitor cells (MC3T3).

RESULTS AND DISCUSSION

Figure 1: Si, Fe, N and C composition over the substrate.

Clear elemental gradients could be obtained with 26 wt.% < Si < 34 wt.%, 10 wt.% < Fe < 20 wt.%, 8 wt.% < C < 14 wt.% and 40 wt.% < N < 47 wt.% (figure 1). The coatings appeared dense in SEM surface analysis, with a smooth surface for all investigated points (Ra ~ 2 nm, AFM). The cross-sectional morphology was slightly columnar with broader columns for higher Fe content. The modulus (202 GPa < M < 221 GPa) correlated positively to the Si content and negatively to the Fe content while for the hardness (14 GPa < H < 18 GPa) no statistically significant correlations were found.  This can be compared to earlier coatings, only containing Si and N, which have showed a Young’s modulus of 170-240 GPa and a hardness of 12-26 GPa2, as well as the currently used metals such as CoCrMo, showing a Young’s modulus of 293 GPa and a hardness of 6 GPa2 .

The in vitro evaluation indicated biocompatibility with viable cells that adhered and spread across the surface.

CONCLUSIONS

Si-N-Fe-C coatings show promise for applications exposed to wear with their low surface roughness, high hardness, high modulus and biocompatibility. These combined merit further investigations into the suitability of Si-N-Fe-C coatings for joint implants.

REFERENCES

1.           Pettersson, M. et al. Mechanical and tribological behavior of silicon nitride and silicon carbon nitride coatings for total joint replacements. J. Mech. Behav. Biomed. Mater. 25, 41–7 (2013).

2.           Skjöldebrand, C. et al. Influence of substrate heating and nitrogen flow on the composition, morphological and mechanical properties of SiNx coatings aimed for joint replacements. Materials (Basel). 10, 1–11 (2017).

 

ACKNOWLEDGEMENTS

The research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under the LifeLongJoints Project, Grant Agreement no. GA-310477.

Place, publisher, year, edition, pages
Maastricht, 2018.
National Category
Medical Materials Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-367364OAI: oai:DiVA.org:uu-367364DiVA, id: diva2:1267102
Conference
29th Annual Congress of the European Society for Biomaterials, Masstricht, 11-13 April, 2018
Funder
EU, FP7, Seventh Framework Programme, GA-310477Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2018-12-05

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Skjöldebrand, CharlotteHulsart Billström, GryEngqvist, HåkanPersson, Cecilia

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