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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...
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 ...
Interfacial design of Cu-based composites prepared by powder metallurgy for hea...
Schubert, Th.; Trindade, B.; Weißgärber, T.; Kieback, B.Thermal aspects are becoming increasingly important for the reliability of the electronic components due to the continuous progress of the electronic industries. Therefore, the effective thermal management is a key issue for packaging of high performance semiconductors. The ideal material working as heat sink and heat spreader should have a CTE of (4-8) × 10-6 K-1 and a high thermal conductivity. Metal matrix c...
Evaluating structural differences in cortical bone tissue after demineralizatio...
Martins, G; Freitas, J; Judas, F; Trindade, B; Figueiredo, HAlthough the best results in bone grafting have been achieved with autogeneuos bone tissue, allografts and xenografts have been widely used either in mineralized, demineralized, or calcined forms. Demineralized bone has been proven to stimulate new bone formation by exposing, proteins and growth factors necessary for osteoinduction. On the other hand, calcined bone offers a natural architectural mineralized mat...
On the formation of intermetallic matrix composites produced by mechanical allo...
Neves, F.; Duarte, N.; Trindade, B.(Ti-48Al)-based intermetallics were synthesized by a combination of mechanical alloying, sputtering and hot isostatic pressure techniques. Blended elemental powders of TiH2 and Al with nominal composition TiH2-48Al were mechanically alloyed for different periods of time. The powders were then coated with Ti and Ag and subsequently hot isostatically pressed at 900 °C with a maximum pressure of 150 MPa for 2 h. F...
Nanostructured coated powders for structural net shape components
Castanho, J. M.; Vieira, M. T.; Matos, M.; Trindade, B.The specific goal of the present study is to evaluate the surface performance of thin films based on sputtered stainless steel (304 AISI) deposited on dissimilar (Cu) and similar powder materials (316 AISI) with different size distributions and shapes. The covering efficiency, the surface morphology and the grain size, and their impact on the flowability of powders, are studied. The most important role of powde...
The mechanochemical processing of aerospace metals
Froes, F. H.; Trindade, B.The status of mechanochemical processing of aerospace metals (aluminum and titanium) is reviewed. It is demonstrated that the activation of chemical reactions by mechanical energy can lead to many interesting applications including production of advanced materials with novel constitutional and microstructural effects leading to enhanced mechanical properties. ; http://www.sciencedirect.com/science/article/B6...
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