Titanium nitride films were formed on the surface of Ti-6Al-4V discs by plasma nitriding (glow discharge) in different N 2 :H 2 atmospheres at several substrate temperatures. In this study the influence of the process parameters on dynamic micro-hardness were investigated. Grain sizes of the nitride films, determined with X-Ray Diffraction, were related to the nitriding parameters. TiNx stoichiometry was determined with Nuclear Reaction Analysis and showed a correlation to substrate temperature during the nitriding process. Micro-hardness measurements were taken on the nitrided surfaces. Grain sizes increased for a particular gas composition of 60%N 2 +40%H 2 where hardness was lowest.
We have studied Co/Cu multilayers to understand the effect of the sample's width on their magnetoresistance (MR). By keeping constant both the length and the thickness and exploring the widths within the range of usual magnetic domain sizes in those nanostructures, we were able to observe effects on the MR curve, as well as infer linked changes in the magnetization process. Associating MR and Planar Hall Effect (PHE) measurements, coupled to an analysis of the MR plots' symmetry, we were able to establish that, apart from the expected antiferromagnetic coupling, reducing the width forces the magnetization to stay aligned to the current channel, thus inducing more symmetric, closer to model Giant Magnetoresistance (GMR). Also, the sample edges might contribute by adding extra coupling through magnetostatic interaction. The added effects result in a counter-intuitive trend that goes from the near ideal wide samples through intermediate sizes with fairly abrupt changes in MR, and finally to the closer to bell-shaped ideal GMR at narrow widths.
Ti-6Al-4V was plasma nitrided using several N 2 /H 2 ratios and substrate temperatures. In order to investigate the combined influence of these parameters on phase composition and thickness of the coatings, the phases in the as received, annealed, and nitrided Ti-6Al-4V samples were identified with Rietveld refinement. In the as-received and annealed samples the structure parameters of -Ti and -Ti were slightly changed, due to the substitution of titanium atoms by Al or V in the and -Ti unit cells. A combination of multiple angle grazing incidence X-ray diffraction, nuclear reaction analysis and cross sectional micrographs showed compound layers consisting of an outer layer of stoichiometric -TiN over a phase mixture of -TiN and -Ti 2 N, formed on top of a nitrogen diffusion region in the alloy. Higher nitriding temperatures induced thicker compound layers, and higher nitrogen content of the plasma induced thicker fine-grained -TiN top layers.
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