Browsing by Author "Viana, A. S."
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- An AFM, TEM, XRD and luminescence study of carbon nanomaterials obtained from cork industry wastewaterPublication . Prata, José Virgílio; Monteiro, O. C.; Silvestre, António Jorge; Viana, A. S.; Costa, AlexandraQuercus suber L. (cork oak) contributes significantly to the economies of several European Union countries. The industrial processing of cork planks involves a cooking operation in which the textural and plastic properties of cork are improved. The resulting wastewater (ca. 400 L/ton of processed cork) is rich in water-soluble extractives, namely phenol- and polyphenol-based compounds and pectins. While the presence of these and other compounds usually defy several spent water treatment processes owing to their inherent poor biodegradability, they represente otherwise a huge opportunity to produce high-valued carbon-based materials.
- Argon assisted chemical vapor deposition of CrO2: An efficient process leading to high quality epitaxial filmsPublication . Duarte, A. C.; Franco, N.; Viana, A. S.; Polushkin, N. I.; Silvestre, António Jorge; Conde, O.A comparative study of the structural, microstructural and magnetic properties of CrO2 thin films grown onto (110) and (100) TiO2 rutile single crystal substrates by chemical vapor deposition (CVD), using CrO3 as chromium precursor and either oxygen or argon as carrier gas is presented. Our results show that growth under argon carrier gas leads to high quality CrO2 epilayers with structural and magnetic properties similar to those obtained using the more standard oxygen carrier gas. Furthermore, we interpret the larger magnetic coercivity observed for the (110) oriented films in terms of their microstructure, in particular of the highest strain and edge roughness of the building structures of the CrO2 epilayers, which are settled by the substrate crystallographic orientation.