Examinando por Autor "Bonache, Victoria"

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Mg–1Zn–1Ca alloy for biomedical applications. Influence of the secondary phases on the mechanical and corrosion behaviour
(Elsevier, 2020-08-05) Pulido-González, Nuria; Torres, Belén; García-Rodríguez, Sonia; Rodrigo, Pilar; Bonache, Victoria; Hidalgo-Manrique, Paloma; Mohedano, Marta; Rams, Joaquín
An as-cast Mg–1Zn–1Ca alloy has been soundly characterized to be used as a biodegradable material in biomedical applications. Ca and Zn additions have a great influence in the microstructure, mechanical properties and corrosion behaviour of Mg alloys. SEM examinations revealed that most of the Ca and Zn atoms form Mg2Ca and Ca2Mg6Zn3 precipitates, which distribute preferentially along the grain boundaries forming a continuous network of secondary phases. The results of nanoindentation tests show differences in hardness and elastic modulus between the α-Mg matrix and the secondary phases. The results of three-point bending tests shows that cracks propagate following the network formed by the intermetallic compounds at the grain boundaries (GBs). The evolved hydrogen after immersion in Hank’s solution of the alloy has been also estimated, showing a change in the corrosion mechanism after 160 h. The intermetallic compounds act as a barrier against corrosion, so that it progresses through the α-Mg matrix phase.
Modulation of Crystallinity through Radiofrequency Electromagnetic Fields in PLLA/Magnetic Nanoparticles Composites: A Proof of Concept
(MDPI, 2021-07-31) Multigner, Marta; Morales, Irene; Muñoz, Marta; Bonache, Victoria; Giacomone, Fernando; de la Presa, Patricia; Benavente, Rosario; Torres, Belén; Mantovani, Diego; Rams, Joaquín
To modulate the properties of degradable implants from outside of the human body represents a major challenge in the field of biomaterials. Polylactic acid is one of the most used polymers in biomedical applications, but it tends to lose its mechanical properties too quickly during degradation. In the present study, a way to reinforce poly-L lactic acid (PLLA) with magnetic nanoparticles (MNPs) that have the capacity to heat under radiofrequency electromagnetic fields (EMF) is proposed. As mechanical and degradation properties are related to the crystallinity of PLLA, the aim of the work was to explore the possibility of modifying the structure of the polymer through the heating of the reinforcing MNPs by EMF within the biological limit range f H < 5 10^9 Am-1s-1. Composites were prepared by dispersing MNPs under sonication in a solution of PLLA. The heat released by the MNPs was monitored by an infrared camera and changes in the polymer were analyzed with differential scanning calorimetry and nanoindentation techniques. The crystallinity, hardness, and elastic modulus of nanocomposites increase with EMF treatment.
S/TEM examination and nanomechanical response of W-Eurofer joints brazed with Cu interlayers
(Elsevier, 2022-06) Izaguirre, Ignacio; Roldán, Marcelo; de Prado, Javier; Bonache, Victoria; Sánchez, María; Ureña, Alejandro
En este artículo se realiza un estudio preliminar a microescala de una unión soldada de dos materiales que conformarán los futuros reactores de fusión. El tungsteno actuará como material de revestimiento del plasma unido a una estructura hecha de algún acero ferrítico-martensítico de activación reducida (acero tipo Eurofer). El proceso de soldadura propuesto introduce cobre como material de relleno y desarrolla el proceso térmico en una atmósfera de alto vacío a 1135 ◦C durante 10 min. La microestructura resultante se caracteriza por formar una capa de difusión en contacto con el material base de tungsteno constituido por W, Fe y Cr. Además, se forma una fase rica en hierro entre la capa de difusión y la región de soldadura de Cu. Esta banda de acero presentó dos estructuras diferentes: una estructura típica de listones de martensita y otra sin ella. En el centro de la banda de acero, los listones son reemplazados por una matriz más homogénea donde el cobre precipita nucleado debido a su enriquecimiento en este elemento durante el proceso de soldadura. Cabe destacar la presencia de dislocaciones y tensiones residuales en todas las diferentes fases que aparecen asociadas al proceso de soldadura fuerte. Esta presencia de tensiones de dislocación muestra como el análisis nanomecánico incrementa los valores de módulo y dureza de la banda de acero respecto al material base Eurofer. La capa de difusión presenta los valores más elevados en la caracterización mecánica debido a su morfología y a los componentes que la constituyen.