Papers by Author: Ana Maria R. Senos

Abstract: This paper reports a preliminary study on the development and characterization of a porous calcium phosphate glass-ceramic for tissue engineering application. To obtain porous glass scaffolds, a mixture of 3CaO.P2O5-SiO2-MgO glass (grain size below 20 'm) and NaCl with 200- 300 'm of particle size was taken in the volume proportion 1:1. The mixture was shaped into cylindrical samples (10 mm diameter x 10 mm thick) by using unidirectional pressing. The sintering thermal cycle was selected by means of thermal analyses (DTA/TG and dilatometry) in order to attain a high enough cohesion among the glass particles. After thermal consolidation, the salt was dissolved in water, resulting in highly porous materials. The effect of the sintering thermal cycle on the structure and microstructure characteristics of the scaffolds was investigated in this paper.

Abstract: The objective of this work was to study the effect of the Ni distribution on the reactivity and densification of WC-(Fe/Ni/Cr) composite powders. For such, stainless steel AISI 304, was used as a binder base composition which was enriched with Ni by three different processing methods: WC sputter deposition using a target of stainless steel with Ni discs, conventional wet milling of commercial powders (WC, stainless steel and Ni powders) and a previous coating of the WC particles with Ni, followed by the conventional mixing of this coated powder with stainless steel powder. The reactive sintering of these composite powders with identical compositions was investigated. The powder compacts were characterized by scanning electron microscopy and X-ray diffraction with Rietveld analysis to quantify de crystalline phases present.

Abstract: The microstructure development and the dielectric properties of La4Mg3W3O18 layered oxide were investigated. A strong anisotropic grain growth is revealed in ceramics sintered above 1400oC. The anisotropy of the grain reflects the anisotropic character of the crystal structure. Dielectric measurements yield a relative dielectric permittivity, ε, and a temperature coefficient of the dielectric permittivity, TC ε, to be 21 and 95 ppm K-1, respectively. The positive value of TC ε is assumed to be caused by the octahedral tilting by analogy with the behaviour of other complex ordered perovskites.

Abstract: To grow single crystals within the solid solutions between PbZrO3 and PbTiO3, PbZrxTi1- xO3 or PZT, is very difficult when compositions are around the morphotropic phase boundary (MPB). In this work, the PZT single crystals were grown by the high temperature solution method, using fluxes with a constant composition, different thermal profiles and different flux/PZT ratios. This approach was successful used to obtain PZT single crystals with compositions near the MPB, of 2 × 2 × 2 mm3 size and without second phases. The specific experimental conditions to obtain these crystals are analysed and discussed.