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The present work is devoted to the optical properties of Au:TiO 2 thin films in order to clarify the role of the Au clusters inclusions in the TiO 2 dielectric matrix. Three series of films containing about 30 at.% (29.2), 20 at. % (19.8) and 10 at.% (9.3) Au were deposited by dc reactive magnetron sputtering. On thermal annealing in the range from 300 to 800°C in protective atmosphere, significant changes on the crystalline phases and clusters dimensions were detected. The most promising optical behavior was found for the film 20% Au:TiO 2 , where the films revealed some colour changes, evolving from several shades of grey to different tones of red. This change in the optical behaviour of the films was found to be correlated with a cluster size increase from 2 to 17 nm. For higher size values (>20 nm) the films, independently of the Au content, showed a golden appearance colour. The optical changes were confirmed by reflectivity and CIELab colour measurements. Regarding the films with 10 and 30 at.% Au, the results confirmed that there is an evident range of compositions and clusters size where the SPR is more evident. Sample A (10 at.% Au) it seems to be in the lower limit of the SPR showing a typical interferometric behavior on the reflectivity measurements, similar to the TiO 2 optical behavior. Regarding the 30 at.% Au one, the results seems to indicate that the amount of gold particles and their grain size is in the upper limit to show a SPR activity.

Composite materials are exposed to a range of hostile environments with consequent degradation in terms of mechanical properties. However, the bibliography is not sufficient to establish a full knowledge about the effect of hostile environments on mechanical properties. This work intends to study the response to flexural and to low velocity impact of a glass fibre/epoxy composite after immersion in two different acid solutions, hydrochloric acid and sulphuric acid. These solutions affect significantly the flexural and impact strength, however, the hydrochloric acid was responsible for the worst results. The maximum load and elastic energy decreases with the impacts. On the other hand, the maximum displacement and damaged area showed an inverse tendency.

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