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Novel two-step processing route combining mechanical alloying and microwave hyb...
Santos, Mário J. G.; Alves, Cátia; Oliveira, F. A. Costa; Marcelo, Teresa; Mascarenhas, João; Cavaleiro, A.; Trindade, B.In this work, microwave hybrid sintering at 1300 and 1350 °C was carried out for densification of La9.33Si2Ge4O26 mechanically alloyed powder with apatite structure. The pellets sintered at these two temperatures present the same structure (apatite) with relative densities of 92 and 96%, respectively. Mechanical analysis performed on sintered materials revealed the following results: hardness of 7.1 and 8.0 GPa...
On the influence of silica type on the structural integrity of dense La9.33Si2G...
Alves, Cátia; Marcelo, Teresa; Oliveira, F. A. Costa; Alves, L. C.; Mascarenhas, João; Trindade, B.Apatite-type rare earth based oxides, such as R-doped lanthanum oxides of general formula La9.33(RO4)6O2 with R = Ge, Si, exhibit high ionic conductivity and low activation energy at moderate temperatures, when compared to the yttria-stabilized zirconia electrolyte making them potential materials to be used in the range 500–700 °C, for intermediate temperature solid oxide fuel cells (IT-SOFCs). In this study, d...
The earrings of Pancas treasure: Analytical study by X-ray based techniques – A...
Tissot, I.; Tissot, M.; Manso, M.; Alves, L. C.; Barreiros, Maria Alexandra; Marcelo, Teresa; Carvalho, M. L.; Corregidor, V.; Guerra, M. F.The development of new metallurgical technologies in the Iberian Peninsula during the Iron Age is well represented by the 10 gold earrings from the treasure of Pancas. This work presents a first approach to the analytical study of these earrings and contributes to the construction of a typological evolution of the Iberian earrings. The manufacture techniques and the alloys composition were studied with three co...
Effect of the sintering conditions on the morphology of La9.33Si2Ge4O26 oxyapat...
Macatrão, Mafalda; Santos, Mário J. G.; Alves, Cátia; Oliveira, F. A. Costa; Marcelo, Teresa; Mascarenhas, João; Trindade, B.Solid oxide fuel cells (SOFCs) are devices that allow direct conversion of chemical to electrical energy through an electrochemical reaction in a cleaner and more efficient way than conventional processes (eg. gas turbines). They are characterized by the use of a solid oxide material as the electrolyte. Yttria-stabilised zirconia (YSZ) has traditionally been used in SOFCs electrolytes at temperatures in the ra...
Synthesis and thermal behavior of La9.33Si2Ge4O26 apatite for SOFCs
Serra, R.; Alves, Cátia; Oliveira, J.C.; Oliveira, F. A. Costa; Marcelo, Teresa; Mascarenhas, João; Trindade, B.Powders of La2O3, GeO2 and SiO2 were dry milled in a planetary ball mill with different rotation speeds (150–350 rpm) and increasing milling times up to 35 h in order to obtain the La9.33Si2Ge4O26 apatite phase at room temperature. The results showed that the higher the rotation speed the lower the time required for the formation of the apatite phase. No reaction between the starting powders was observed at 150...
Mechanical properties of sintered La9.33Si2Ge4O26 oxyapatite materials for SOFC...
Santos, Miguel; Alves, Cátia; Oliveira, F. A. Costa; Marcelo, Teresa; Mascarenhas, João; Fernandes, J.V.; Trindade, B.Mechanical properties of La9.33Si2Ge4O26 prepared by mechanical alloying and subsequent sintering at 1300–1400 °C for 1 h were evaluated. Hardness and Young's modulus values in the range 7.3–9.6 GPa and 106–135 GPa, respectively, were obtained from nanohardness tests. The fracture toughness values derived from the Palmqvist method varied between 3.5 and 3.9 MPa m1/2 from classical microindentation test with an ...
Sintering response and mechanical properties of microwave sintered 316L Powder ...
Mascarenhas, João; Marcelo, TeresaMicrowave sintering can be an efficient, economic and valuable approach for the processing of some PM materials. Recent findings on the ability of powdered metals to absorb and dissipate microwave radiation, opened new opportunities for the PM world. Being the particle size of the metallic powders one of the key parameters that rules the heating rate and the temperature performance during microwave sintering, w...
Microstructural characterization and interactions in Ti- and TiH2-hydroxyapatit...
Marcelo,Teresa Maria; Livramento,Vanessa; Oliveira,Marize Varella de; Carvalho,Maria HelenaTitanium/hydroxyapatite (HAP) composites are candidate materials for biomedical applications as implants and hard tissue substitutes since they combine the good mechanical properties and biocompatibility of Ti with the excellent HAP bioactivity and osteointegration. In powder metallurgy processing of these composites, HAP decomposition promoted by Ti during powder sintering is found. In a previous work Ti-50v%H...
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