Eugenio Luís Solla

Marine Precursors-Based Biomorphic SiC Ceramics

Biomorphic silicon carbide ceramics is very promising as a natural base material for biomedical applications due to their excellent mechanical-biochemical properties and biocompatible behaviour. This innovative material is produced by molten-Si infiltration of carbon templates obtained by controlled pyrolysis of biological precursors. The final product is a light, tough and high-strength material with predictable microstructure. In this study the possibility to produce biomorphic silicon carbide ceramics using marine precursors is demonstrated. Due to the great biodiversity offered by the marine medium, a previous selection of algae (Laminaria ochroleuca Bachelot de la Pylaie, Undaria pinnatifida (Harvey) Suringar, Saccorhiza polyschides (Lightfoot) Batters and Cystoseira baccata (Gmelin) Silva) and marine plants (Zostera marina L. and Juncus maritimus L.) was carried out, taking into account its microstructure, porosity and interconnectivity of each species. The bioceramization process was evaluated in three phases: original material analysis, pyrolysis process and reactive melt Si-infiltration. For each marine precursor, a detailed study by Scanning Electron Microscopy (SEM) of the natural material, the carbon preform and the final SiC biomorphic product is described. The viability to obtain biomorphic SiC ceramic material for all the selected marine precursors is discussed.

The Role of Si Substitution into Hydroxyapatite Coatings

Silicon substituted Hydroxyapatite coatings were prepared by Pulsed Laser Deposition from targets made of mixtures of Hydroxyapatite with Si powder at different concentrations. The properties of the Si-HA coatings with several degrees of Si substitution were analyzed by different techniques such as FTIR, XRD, XPS and solid-state NMR. It was found that the Si incorporation causes an amorphization of the structure together with a loss of carbonate groups. Furthermore, the Si atoms are incorporated in the form of SiO4 4- groups, and H(PO4)2- appears as the predominant phosphate group.

Bioceramic Coatings on Biomorphic SiC by Electrophoretic Deposition

In this research, bioactive glass powders were electrophoretically deposited on biomorphic SiC ceramic substrates. A post-deposition thermal treatment was carried out to improve the properties of the coatings. Particle size, surface morphology, composition and thickness of the coatings have been studied by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and interferometric profilometry respectively. The analysis demonstrated that the electrophoresis parameters, such as the voltage, the distance between the electrodes and the deposition time, play an important role on the thickness of the coatings. The post-deposition thermal treatment produces glass particles cohesion and leads to obtaining a homogeneous microstructure. The excellent coverage of the porous SiC surface morphology is also demonstrated. Finally, in order to assess the bioactive character of the glass coatings, in vitro test by immersion in simulated body fluid (SBF) was carried out.

Combined Structural Investigations of Bioactive Silicate Glasses

The results of a combined structural characterisation (XRD, IR, NMR, SEM, TEM) of a phosphate containing Mg-Ca silicate and a phosphate containing Na-Ca silicate glass samples are presented. The structural results are also compared with in vitro tests carried out in simulated body fluids for checking bioactivity.

Influence of Substrate Temperature in Plasma Assisted Pulsed Laser Deposition of Hydroxyapatite Thin Films

The bioactive properties of hydroxyapatite (HA) are well known in the implant industry and coatings of HA have been used to enhance the adhesion of living tissue to metal prostheses. Pulsed laser deposition (PLD) in a water vapour atmosphere is an appropriate method for the production of crystalline HA coatings. In this work the effect of RF plasma on thin films of HA grown by PLD at different substrate temperatures has been studied. The physicochemical properties of the films were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS), showing that the incorporation of RF discharge in the deposition chamber can lead to changes in the crystallinity and deposition rate of the films but substrate temperature still plays the most important role.