Tailoring surface properties of metals by laser texturingWettability control and guided degradation for biomedical applications

Resumo

The present project addresses the use of laser texturing treatments for the control of surface properties of metallic materials. Particularly, the capability of the technique for controlling the surface wettability and aqueous degradation will be studied. The control of surface wettability is very interesting for the development of self-cleaning surfaces, optimization of heat transfer in heat exchangers, drag reduction in pipes or boat hulls or the development of systems for dew harvesting as an alternative water source. Several previous studies demonstrate the efficacy of the laser texturing technique for modifying the wettability of metallic surfaces. Wettability control of 304 stainless steel surfaces will be addressed here. Particularly, the effect of the processing atmosphere, key property determining the surface composition of the textured surfaces, will be studied. In combination with the generation of micro and nano topography features, inherent to the laser texturing technique, the control of the surface composition would allow the control of the resulting wettability. Surface wettability will be evaluated via measurements of contact angle and hysteresis, relating them to the topography and surface composition characterization. After selecting a suitable processing atmosphere, by the adjustment of the processing parameters the generation of superhydrophobic and superhydrophilic surfaces will be pursued. Finally, the applicability of the obtained results for maximizing the performance of dew water harvesting surfaces via condensation phenomena will be evaluated. The control of corrosion phenomena in aqueous media finds application in sacrificial anodes for cathodic protection of metallic structures, the development of batteries or in the manufacturing of degradable implants for biomedical applications. Several previous studies demonstrate the efficacy of laser surface treatments for reducing the usually excessive degradation rate of magnesium. The control of the degradation in saline solutions of the AZ31 magnesium alloy will be addressed here. Particularly, the effect of the pulse length, key property determining the thermal effects and the microstructural changes induced in the material, will be studied. The control of those changes as well as of its distribution through the surface would allow the control of the resulting degradation rate. The corrosion rate will be quantified through immersion tests in saline solutions and electrochemical techniques, relating the to the topography, microstructure and composition modifications induced during the treatment. After selecting the proper pulse length, by the adjustment of the processing parameters the development of treatments for achieving a guided degradation will be attempted. Finally, the applicability of the obtained results for the development of guided degradation implants in biomedical applications will be evaluated.