Biomedical Engineering – From Theory to Applications

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268 Biomedical Engineering – From Theory to Applications For MS sample, failure events can be seen with cracks perpendicular to the scratch direction that appear on the bottom of the groove. These cracks are essentially due to the tensile stress at the trailing edge of the contact during friction. Furthermore, others cracks are visible on both sides of the scratch (Fig. 15). In contrast, PLD 4 and PLD 6 samples show no evidence of failure and a rather ductile behavior as seems to indicate the allure of the loaddisplacement curves for these samples (Fig. 14). As mentioned with nanohardness measurements, the mechanical properties of PLD 6 are higher. It is important to note that the harder film (PLD 6) appears to be tougher than the softer (PLD 5), as determined by nanoindentation experiments exposed in the above section. However, failure processes are dependent on the deposition routes through residual stresses generated at the interface between film and substrate and also on the adhesion energy which can explain that MS sample (which shows the higher hardness compared to any PLD samples) is subject to cracking under nanoscratch. We can, however, notice that in comparison to PLD 5, these failure events appear with some delay and for a higher load. Using the same tribological experimental conditions scratch tests were performed on the HA samples. Some results are given in Fig. 16 with increasing load from 0.75 to 15 mN (realized in three steps) at the sliding speed of 10 µm·s -1 (length scratch was 500 µm). The HA tribological behaviour is opposed to one of Al2O3 layer. It is due to the surface morphology of this last one which is a dense, homogeneous and with weak roughness. Opposite tribological performance of the PLD HA on Ti substrate is conditioned by its topography presenting a high roughness due to the presence of droplets of different diameters and nanoaggregates. This can de described by the high level of oscillations in the penetration curves. The HA-1 and HA-2 analysis of curves cannot clearly show a distinct mechanical behaviour within the tested range of load. Fig. 16. Resistance to Penetration curves determined by scratch experiments on (a) HA-1 and (b) HA-2 7. Conclusions Morphological, structural, nanoscratch and nanoindentation studies were performed to evaluate the composition, crystallinity status and mechanical properties of Al2O3/304L and HA/Ti structures synthesized by PLD and MS. We compared the characteristics of the substrates and their coatings deposited in different conditions. Alumina nanostructured
Nanocrystalline Thin Ceramic Films Synthesised by Pulsed Laser Deposition and Magnetron Sputtering on Metal Substrates for Medical Applications films had a smooth surface, with few alumina particulates deposited on. They were stoichiometric, partially crystallized with an amorphous matrix. The obtained values of hardness and elastic modulus of the studied films are in good agreements with those found in literature. Different mechanical behaviours were observed in relation to different parameter of deposition (with or without working pressure in O2). By nanohardness and wear measurements, the mechanical properties of PLD 6 are higher. The harder PLD 6 film appears to be tougher than the softer films MS and PLD 5, as determined by nanoscratch experiments and validate by tribological tests. We also compared the characteristics of the HA synthesized with (HA-1) and without (HA-2) a post-deposition heat treatment in water vapour showing a well-crystallized, polycrystalline structure and an irregular HA morphology due to the chemical etching of the substrate and the presence of some HA particles and droplets, characteristic to PLD coatings. Tribological behaviour of HA samples is mainly conditioned by the surface morphology as detected by the numerous oscillations on the scratch penetration curves. During scratching, the plastic strain is the leading deformation mechanism without failure event, at least in the tested load range. These studies reveal that the pulsed-laser deposition and magnetron sputtering techniques appears extremely versatile technology and good candidates in tribological applications. 8. Acknowledgements The authors wish to thank Prof I.N. Mihailescu and Dr. Sorin Grigorescu for performing PLD HA INFLPR of Bucharest in Romania; Mr. Jacques Faerber (IPCMS) for SEM characterizations; Mr. Guy Schmerber for preparing the MS alumina samples (IPCMS) and Mr. Gilles Versini (IPCMS) for the elaboration of PLD alumina samples. We acknowledge the financial support of Egide–Centre français pour l’accueil et les échanges internationaux by the PAI Brancusi (08867SD) and PAI IMHOTEP (12444SH) projects. 9. References Ahn H. and Kwon D. (2000), Micromechanical estimation of composite hardness using nanoindentation technique for thin film coated system Materials Science and Enigineering A vol 285 p. 172 – 179, ISSN 09215093. Arias J.L., Mayor M.B., Garcia-Sanz F.J., Pou J., Leon B., Perez-Amor M. & Knowles J.C. (1997). Structural analysis of calcium phosphate coatings produced by pulsed laser deposition at different water-vapour pressures. Journal of Materials Science: Materials in Medicine, Vol. 8, No 12, pp. 873-876, ISSN 0957-4530. Arias J.L., Mayor M.B., Pou J., León B. & Pérez-Amor M. (2002). Transport of ablated material through a water vapor atmosphere in pulsed laser deposition of hydroxylapatite. Applied Surface Science, Vol. 186, No 1-4, 28 January 2002, pp. 448- 452, ISSN 0169-4332. Babaluo A. A., Kokabi M., Manteghian M., Sarraf-Mamoory R. (2004). A modified model for alumina membranes formed by gel-casting followed by dip-coating. Journal of the European Ceramic Society, Vol. 24, No 15-16, pp. 3779-3787, ISSN 0955-2219. Bordji G., Jouzeau J-Y., Mainard D., Payan E., Delagoutte J-P. & Netter P. (1996). Evaluation of the effect of three surface treatments on the biocompatibility of 316L stainless 269
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BIOMEDICAL ENGINEERING - FROM THEOR
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free online editions of InTech Book
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VI Contents Chapter 9 Targeted Magn
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X Preface stand-alone and readers c
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110 Method (Detection) Analyte Matr
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120 6. Conclusion Biomedical Engine
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150 5. Conclusions Biomedical Engin
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162 1 st phase : half year 4 2 nd p
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172 12. Maturing projects’ story
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180 16. Acknowledgments Biomedical
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190 R* M M M M MR*M O O O O M O R*
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196 Fig. 9. Chemical structure of 5
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198 Relative Intensity (AU) Biomedi
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204 2. Preparation of IO nanopartic
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454 In this case, the eigenvalues a
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472 Nb b b l l1 Biomedical Engineer
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