Papers by Author: Mafalda Guedes

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Authors: Mafalda Guedes, José Maria F. Ferreira, Alberto C. Ferro
Abstract: This paper reports preliminary studies regarding a new fabrication process for aluminium alloy matrix particulate reinforced composites, which uses ceramic preforms with alumina and tailored amounts of reactive copper oxide, CuO. An Al2O3-CuO mixture with 75 mol% CuO was selected, aiming at a 10-40vol% reinforcement phase fraction in the final composite, after aluminium infiltration. Molten aluminium infiltration progress was studied as a function of ceramic’s composition, doping, and infiltration time. The resulting microstructures were investigated by OM, SEM, FESEM and EDS in order to establish the liquid aluminium infiltration profile at the metal/ceramic interface. Infiltration experiments showed that the 3CuO (s) + 2Al (l) → 3Cu (l) + Al2O3 (s) redox reaction is triggered at the experimental conditions used, but the infiltration process is slow and does not go to completion. The use of NaOH as a doping agent promotes effective infiltration of molten aluminium upon the ceramic green mixture.
Authors: Mafalda Guedes, Alberto C. Ferro, José Maria F. Ferreira
Authors: Mafalda Guedes, Alberto C. Ferro, José Maria F. Ferreira
Authors: Mafalda Guedes, Alberto C. Ferro, José Maria F. Ferreira
Abstract: Obtaining ceramic bodies with enhanced mechanical properties via colloidal processing requires efficient dispersion of the ceramic powders. In this work, the dispersive effect of three low molecular weight quaternary ammonium hydroxides with different alkyl groups upon stabilisation of CuO aqueous suspensions is studied and compared with that of Tiron, a compound based on the benzene molecule. The purpose is to illustrate the effect of molecular structure, size and charge location upon dispersing effectiveness. To access these parameters, rheological and electrophoretic measurements using both bare and surface charge modified CuO were made. Tiron® revealed to be the most efficient dispersant for CuO in water, rendering viscosity values below 1 Pa⋅s and the highest variation in zeta potential amplitude.
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