A. Portinha
University of Minho
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Featured researches published by A. Portinha.
Optical Engineering | 2008
Manuel F. M. Costa; C. Batista; A. Portinha; V. Teixeira; Carlos Oliveira; Ricardo M. Ribeiro
Thermal barrier coatings (TBCs) are extremely useful in gas turbine engines. The quality of these coatings can be improved by subjecting their surface to laser glazing. A reduction in surface roughness, eliminating open porosity on the surface, and the generation of a controlled segmented crack network, can be achieved. TBCs consisting of atmospheric plasma sprayed (APS) ZrO 2 -8%wtY 2 O 3 are subjected to a CO 2 continuous wave laser glazing process to seal their surface porosity, generating an external dense layer. Different amounts of irradiation are applied to the specimens. The microtopograpic inspection of the samples reveal a significant decrease of the surface roughness after laser treatment. However, a network of surface cracks, dependent on the laser scanning speed and track overlapping, are noticed. The cracks have a tendency to be oriented in two perpendicular directions, one in the direction of the laser beam travel direction, the other perpendicular to it. Cracks parallel to the beam scanning direction are found to be at the overlapping zone, in the edge of the subsequent track.
Materials Science Forum | 2006
A. Portinha; V. Teixeira; Joaquim A. O. Carneiro; Rachel Newton; H. Fonseca
Zirconia (ZrO2) exhibits three different polymorphic phases as a function of the thermal and pressure conditions (cubic, tetragonal and monoclinic). The use of zirconia coatings at high temperatures requires it to be stabilized at room temperature in order to maintain the high temperature phases when subjected to thermal cycles. For this purpose, this work reports different ways to stabilize ZrO2 coatings produced by DC reactive magnetron sputtering. We have produced stabilized ZrO2 coatings by doping with other metallic and rare earth oxides (Y2O3 and Gd2O3), depositing nanostructured ZrO2 crystallites in an amorphous Al2O3 matrix and using a ZrO2/Al2O3 nanolaminated structure. A comparative study of the coatings produced is presented along with their structural stabilization using different approaches. For the doped coatings the tetragonal or cubic phases were obtained as a function of the dopant percentage and for the nanostructured and nanolayered structures the stabilization mechanism is related to the constraining of the zirconia nanocrystallites and the capacity to maintain its size under certain value.
Archive | 2003
A. Portinha; V. Teixeira; Jorge Martins; Manuel F. M. Costa; Robert Vassen; D. Stoever
Thermal barrier coatings (TBC’s) are used in a number of energy-related applications, such as protective layers in aero and land based gas turbine components at very high temperature.
Surface & Coatings Technology | 2005
A. Portinha; V. Teixeira; Joaquim A. O. Carneiro; Jorge Martins; Manuel F. M. Costa; Robert Vassen; D. Stoever
Surface & Coatings Technology | 2006
C. Batista; A. Portinha; Ricardo M. Ribeiro; V. Teixeira; Carlos Oliveira
Materials Science and Engineering B-advanced Functional Solid-state Materials | 2007
Joaquim A. O. Carneiro; V. Teixeira; A. Portinha; A. Magalhães; P. Coutinho; C.J. Tavares; R. Newton
Surface & Coatings Technology | 2004
A. Portinha; V. Teixeira; Joaquim A. O. Carneiro; M.G. Beghi; C. E. Bottani; N. Franco; Robert Vassen; D. Stoever; A.D. Sequeira
Applied Surface Science | 2005
C. Batista; A. Portinha; Ricardo M. Ribeiro; V. Teixeira; Manuel F. M. Costa; Carlos Oliveira
Vacuum | 2005
Joaquim A. O. Carneiro; V. Teixeira; A. Portinha; L. Dupák; A. Magalhães; P. Coutinho
Surface & Coatings Technology | 2006
C. Batista; A. Portinha; Ricardo M. Ribeiro; V. Teixeira; Manuel F. M. Costa; Carlos Oliveira