Resumen de Design and characterization of dense and porous fe-based alloys for biomedical and environmental applications
This Thesis dissertation covers different synthetic approaches to obtain Fe-based alloys to be used for biomedical and environmental applications. Special emphasis has been placed to design a proper composition and to study the morphology and structural properties to tailor both the mechanical and magnetic properties of the resulting materials.
Firstly, ferromagnetic Fe-10Mn6Si1Pd (wt.%) and shape memory, paramagnetic Fe-30Mn6Si1Pd (wt.%) compact alloys were prepared by arc-melting followed by copper mold suction casting. The evolution of microstructure, mechanical and magnetic properties, as well as the assessment of degradation, cytotoxicity and cell proliferation in Hank’s solution as a function of the immersion time were systermatically studied.
With the aim to improve the biocompatibility of the Fe-10Mn6Si1Pd alloy, calcium phosphate coatings (CaP) (i.e., brushite and hydroxyapatite) were electrodeposited on the alloy by pulsed current electrodeposition. Due to porous structures resulting from needle-, rod- or plate-like morphologies, the measured Young’s modulus and hardness of these coatings were lower than those of fully-dense CaP layers with analogous compositions.
Then, to increase the degradation rate and to reduce the Young’s modulus of the fully bulk alloys, porous Fe-30Mn6Si1Pd (wt.%) alloys were prepared by a simple press and sinter process from ball-milled Fe, Mn, Si and Pd powders blended with 10 wt.%, 20 wt.% and 40 wt.% NaCl. Remarkably, the reduced Young’s modulus of all the porous alloys reached values close to 20 GPa after long-term immersion, a value which is close to the Young’s modulus of human bones (3–27 GPa), hence favoring good biomechanical compatibility between an eventual implant and the neighboring bone tissue.
Meanwhile, open cell Fe and Fe-Mn oxides foams were prepared by the replication method using porous polyurethane templates. The magnetic response of the foams, from virtually non-magnetic to ferrimagnetic, could be tailored by controllably adjusting the Mn content as well as the N2 flow rate. Still dealing with magnetic properties, femtosecond pulsed laser irradiation was used to create periodic magnetic patterns at the surface of a non-ferromagnetic amorphous Fe-based alloy.
Finally, a nanoporous Fe-rich alloy was prepared by selective dissolution of melt-spun Fe43.5Cu56.5 ribbons. The nanoporous ribbons were found to be an excellent heterogeneous Fenton catalyst towards the degradation of methyl orange in aqueous solution.
