A new method for materials synthesis:: Solar energy concentrated by Fresnel lens

For the first time solar energy concentrated by a Fresnel lens has been used to obtain titanium nitride films by heating the surface of titanium specimens in a nitrogen atmosphere. We present first results on the surface nitriding of titanium using a new set-up based on a 1.2x0.8 m Fresnel lens. The maximum power density obtained with this lens has been 240 W/cm(2) in a focus of 1 cm diameter. The lens is mounted on an azimutal mounting, which permits solar tracking. The heat isolated specimen is placed in a steel reaction chamber of approximately 500 cm(3) volume, provided with a quartz window, in which the nitrogen is introduced. This new system permits the obtainment of uniform films across ail the surface perpendicular to the radiation. This nitrided coating grown by nitrogen solid diffusion is very uniform and neither pores nor cracks are observed on it, with the characteristic golden colour of TIN after a treatment time of only 2 minutes. Morphological and X-Ray Dispersion (XRD) characterization of the specimens shows that the predominant phases in the specimens are TIN and TiN0.3.