Browsing by Author "Rodrigues, I."
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- 3D-Printing of zirconia dental prosthesesPublication . Rodrigues, I.; Olhero, S.; Guedes, M.; Serro, A. P.; Figueiredo-Pina, C. G.
- Abundance and diversity of potential vectors of Xylella fastidiosa in four different wine regions of PortugalPublication . Rodrigues, I.; Pereira, L. F.; Villa, M.; Santos, Sónia A.P.; Baptista, P.; Pereira, J.A.
- Effect of albumin, urea, lysozyme and mucin on the triboactivity of Ti6Al4V/zirconia pair used in dental implantsPublication . Teixeira, H.; Branco, A. C.; Rodrigues, I.; Silva, D.; Cardoso, S.; Colaço, R.; Serro, A. P.; Figueiredo-Pina, CélioThe titanium implant/zirconia abutment interface can suffer failure upon mechanical and biological issues, ul- timately leading to the loss of the artificial tooth. The study of the effect of the organic compounds present in saliva on the tribological behavior of these systems is of utmost importance to understand the failure mechanisms and better mimic the in vivo conditions. The aim of the present work is to evaluate the effect of the addition of albumin, urea, lysozyme and mucin to artificial saliva, on the triboactivity of Ti6Al4V/zirconia pair commonly used in dental implants and then, compare the results with those obtained with human saliva. The solutions’ viscosity was measured and the adsorption of the different biomolecules to both Ti6Al4V and zirconia was accessed. Tribological tests were performed using Ti6Al4V balls sliding on zirconia plates inside of a corrosion cell. Friction and wear coefficients were determined, and the open circuit potential (OCP) was monitored during the tests. Also, the wear mechanisms were identified. The presence of mucin in the artificial lubricant led to the lowest wear coefficients. The main wear mechanism was abrasion, independently of the used lubricant. Adhesive wear was observed for the systems without mucin. Tribocorrosion activity and wear coefficient were lower in the presence of mucin. None of the studied artificial lubricants mimicked the effect of human saliva (HS) on the tribological behavior of the studied pair since this lubricant led to the lowest friction coefficient and highest corrosion activity.
- Effect of H2O2 solution’s pH on the human enamel micro and nanowearPublication . Branco, A. C; Rodrigues, I.; Paradiso, P.; Polido, M.; Colaço, R.; Figueiredo-Pina, C. G.; Serro, A. P."The effect of 30% H2O2 solutions with different pH (2, 4 and 6) on the wear of human dental enamel was studied. Additionally, the whitening efficiency and changes in hardness and morphology were evaluated. The enamel tribological response was accessed through two different approaches: ball-on-plate and atomic force microscopy (AFM), the later following a tribological model based on a single asperity contact. The results showed differences in the specific wear rate and wear mechanisms between the two used approaches. Regardless of the tribological approach used, the wear resistance of enamel was lower for pH = 2. It was observed that pH = 6 leads to a safe and efficient whitening treatment."
- Processing of Copper-Graphite-Alumina Powders by High-Energy MillingPublication . Rodrigues, I.; Guedes, M.; Ferro, A. C.Copper-matrix composites are versatile materials used in several electromechanical applications, but relatively low strength and thermal stability impair advanced uses. Development of robust solutions combining low wear and low electrical loss are thus paramount. This work proposes high-energy milling of copper-graphite-alumina powders: graphite is conductive and self-lubricating; alumina toils as dispersion-strengthener and grain refiner. Tailored batches with 2wt%-graphite and 2wt%-alumina were milled up to 16h in planetary ball mill and characterized by XRD, FEG-SEM/EDS, microhardness and Raman. Produced powders are nanostructured, containing graphite and alumina nanoparticles homogeneously distributed in copper. Increasing milling time results in some degree of nanographite amorphization and size decrease. Copper crystallite size and achieved hardness are affected mainly above 4 h milling. Attained results suggest that efficient dispersion of graphite and alumina nanoparticles is achieved, envisaging high conductivity, high strength and thermal stability. The copper-graphite-alumina system thus seemingly opens an opportunity window for PM processing of advanced copper composites.