News
26.05.2021Publication of new papers with contributions from the TEM-MAT unit
Dr. Lluís López Conesa, of the MET Technology Applied to Materials of the CCiTUB, has participated in the articles “Mapping the Magnetic Coupling of Self-Assembled Fe3O4 Nanocubes by Electron Holography” published in the journal Materials, and also in the article “Apatite Mineralization Process from Silicocarnotite Bioceramics : Mechanism of Crystal Growth and Maturation” published in the journal Crystal Growth & Design.
The articles have been carried out in collaboration with researchers from the Centre de Projecció Tèrmica of the Universitat de Barcelona, from the University of Erlangen-Nuremberg, from the Consorcio de Manufactura Auditiva de Mèxic, from the Centro de Investigación y de Estudios Avanzados Unidad Querétaro, from the Universidade de Santiago de Compostela and from the company Ecoresources.
The abstracts of the articles are as follows:
Mapping the Magnetic Coupling of Self-Assembled Fe3O4 Nanocubes by Electron Holography
The nanoscale magnetic configuration of self-assembled groups of magnetite 40 nm cubic nanoparticles has been investigated by means of electron holography in the transmission electron microscope (TEM). The arrangement of the cubes in the form of chains driven by the alignment of their dipoles of single nanocubes is assessed by the measured in-plane magnetic induction maps, in good agreement with theoretical calculations.
To read the paper, access here [+].
Apatite Mineralization Process from Silicocarnotite Bioceramics: Mechanism of Crystal Growth and Maturation
A mechanism for the formation and crystallization processes of bone-like apatite grown on non-stoichiometric silicocarnotite (SC) is here proposed. Single-phase SC powders and ceramics were obtained from fixed mixtures of hydroxyapatite and bioactive glass 45S5. The bioactive behavior of SC was assessed by immersion in Hank’s solution at different times. Afterward, a systematic theoretical–experimental study of the structural properties at the micro- and nanoscale using transmission electron microscopy was performed and correlated with scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman techniques to determine the apatite mineralization process from the SC phase. The initial stage of apatite formation from SC was identified as the hydration and further polymerization of silanol groups, resulting in a silica-based hydrogel, which plays a critical role in the ionic exchange. As a result of the adsorption of ionic species from the medium into the silica-based hydrogel, the precipitation of crystalline apatitic structures starts through the emergence of newly formed SC nanocrystals, which act as a template for the crystallization process of a substituted apatite with SC-like structure. Then, because of the polymorphism between SC and HAp structures, the apatite layer retains the SC periodic arrangement following an epitaxial-like growth mechanism. Identification of the apatite layer formation mechanism is critical to understand its physical and chemical properties, which controls the long-term dissolution/precipitation rate of bioactive materials and their performance in the biological environment.
To read the paper, access here [+].