The aim of this work is the production and characterisation of sol-gel coatings for protection and bioactivation of metals used as standard surgical implant materials, such as stainless steel 316 L (ASTM F138), Co based alloys (ASTM F75) and titanium alloy Ti-6Al-4V (ASTM F67). These films should both prevent degradation of the substrates by wear or corrosion, and bioactivate the material for inducing the formation of a hydroxyapatite (HA) rich layer onto the material surface, thereby permitting a natural bonding to living tissues. Formation of HA layers can be observed on performing in vitro tests by soaking the material in simulated body solutions. The work describes the development of coatings containing bioactive glass and glass-ceramic particles in hybrid methyl-triethoxysilane (MTES) and tetraethylorthosilicate (TEOS) acidic sol, applied by dip-coating to surgical alloys, AISI 316 L, ASTM F75 and ASTM 67, with the aim of accomplishing both high corrosion resistance of the metal in the body environment and adhesion of the implant to the surrounding tissue. The performance of the coated metal was evaluated in vitro by electrochemical techniques including potentiodynamic polarisation curves and electrochemical impedance spectroscopy, to follow the formation of hydroxyapatite on the surface, as well as the in vitro release of ions by plasma atomic emission spectroscopy (ICP-MS) after up to one year of immersion. In vivo behaviour was evaluated by subcutaneous tests and endomedullar implantation in Hokaido rats to study possible rejection reactions and natural bonding to living tissue.

A commercial highly focused (Gaussian) nanosecond UV (266 nm) Nd:YAG laser ablation system coupled to an inductively coupled plasma quadrupole mass spectrometer was examined as a tool for depth profile analysis of copper coating on steel. The studied samples were Standard Reference Materials 1361b and 1362b from NIST, which consist of a set of eight coupons of an AISI 1010 cold rolled sheet steel substrate with a uniform coating of copper (certified copper coating thickness: 5.9, 12.3, 25.3, 40.6, 52.0, 77, 130, and 199 mm). Depth resolution was determined from the normalized depth profiles as a function of irradiance, which was varied by changing the laser pulse energy and the focusing conditions, as well as coating thickness. At lower irradiances, depth resolution values were higher for irradiances obtained by changing the laser pulse energy, whereas at higher irradiances this parameter was higher for irradiances obtained by changing the focusing conditions. At moderate irradiance levels, the results obtained were quite similar, and, in addition, the best depth resolution was attained in this irradiance range, which was obtained by using a moderate laser energy (about 2 mJ per pulse) and by focusing the laser beam below the sample surface (approximately 2000 mm). Depth resolution increased linearly with coating thickness. For the eight studied samples the ablation rate was approximately 1 mm per pulse and the depth resolution values were between 0.8 mm for the thinnest coating and 26 mm for the thickest one.

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A methodology for bulk analysis of Al and Ti and for determination of soluble and total Al and Ti concentration in steel samples by laser ablation inductively coupled plasma mass spectrometry was developed. The spatial distribution (both at surface and within the sample) of the insoluble fraction of Al and Ti was also qualitatively estimated. Certified reference materials (CRMs) SS-451 to 460 (carbon steel) and 064-1 (Nb/Ti interstitial free steel), from BAS, and JK 2D (carbon steel) and JK 37 (highly alloyed steel), from SIMR, were studied. It was demonstrated that the insoluble fraction of Al and Ti is heterogeneously distributed. A series of nine glass samples (fused beads) with fixed Fe content and different Al and Ti contents was prepared by melting appropriate amounts of Fe(2)O(3), Al(2)O(3) and TiO(2) with a lithium tetraborate-sodium carbonate mixture. Quantitative determinations were performed by using calibration graphs obtained from the synthetic fused beads, with (57)Fe as internal standard; line scan laser sampling mode was used, focusing the laser beam at the sample surface. The optimized laser operating parameters were: laser pulse energy of 1.5mJ, pulse repetition rate of 5Hz, scanning speed of 5microm s(-1) and preablation time of 20s. The concentrations obtained for bulk analysis of CRM samples corresponded with the certified values within the experimental uncertainty. An acceptable concordance between certified and found values was attained for the determination of soluble and total Al and Ti in CRM 064-1 sample.

Isotope dilution analysis using flow injection inductively coupled plasma mass spectrometry was applied to determine low boron contents in iron and steel samples. Sample dissolution was carried out in a microwave oven with an HCl, HNO3, and H2SO4 acid mixture and high-pressure digestion vessels. A solvent extraction procedure using acetylacetone−chloroform was applied for the separation of the iron matrix as the sulfate (pH = 1.4 ± 0.1). Test solutions corresponding to 50 mg mL-1 of sample, with the total boron content and iron contents below 1 μg mL-1, were obtained. Flow injection was used as a sampling system to minimize problems arising from the total salt concentration of the test solutions. This method made it possible to analyze boron in iron and steel at submicrogram per gram levels. The detection limit (3σ), in micrograms of boron per gram of sample, was 0.02, and the precision for concentrations above 10 times the detection limit was better than 1%. Accuracy was tested with eight standard reference materials with boron certified values in the 0.5−10 μg g-1 range.