
Paula M. C. TorresUniversity of Aveiro | UA · Department of Materials and Ceramics Engineering
Paula M. C. Torres
PhD
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41
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Publications (41)
Magnetic calcium phosphate (CaP) nanoparticles have been explored for a wide range of applications, namely biodevices for bone regeneration and local cancer treating through hyperthermia therapy. Numerous shaping techniques to obtain dense and porous ceramic structures are based on colloidal processing principles, in which parameters such as crysta...
Diverse applications of nanoparticles (NP) have been revolutionary for various industrial sectors worldwide. In particular, magnetic nanoparticles (MNP) have gained great interest because of their applications in specialized medical areas. This review starts with a brief overview of the magnetic behavior of MNP and a short description of their most...
Additive manufacturing appears to facilitate the accurate manufacturing of alumina-zirconia technical ceramics. Nevertheless, the fine tuning of the manufacturing of these components by 3D printing requires an analysis of the parameters that influence their final thermoelastic properties. In this context, this work presents the application of (fini...
Despite recent years' remarkable progress in medical procedures for bone reconstruction, the implementation of newly developed biomedical materials is still facing technical drawbacks, such as, lack of mechanical strength, impaired cellular proliferation and differentiation, limited osteogenesis and issues related to bone infection, osseointegratio...
This work aims the manufacture of injection molded polylactic acid (PLA)-based magnetic biocomposites, presenting an alternative approach to enhance the magnetic susceptibility of PLA-based biocomposites without resorting to the exclusive incorporation of magnetic nanoparticles whose long-term side effects are still unclear. Magnetic biocomposites...
The current need to develop Additive Manufacturing (AM) processes capable of producing defect-free, fully-dense functional ceramics could benefit from the knowledge consolidated throughout the years in conventional processing. This review provides an up-to-date status of AM fabrication of dense alumina, zirconia and their composites, in comparison...
The present work aims the production of composite bioceramic scaffolds by robocasting suppressing sintering as post printing process. To achieve this purpose, extrudable ink compositions containing a high concentration of bioceramic powders (hydroxyapatite and β-tricalcium phosphate) embedded in aqueous polymeric solutions of chitosan and silk fibr...
Objectives
The present work reports the effect of the extrusion nozzles’ size and consequent residual porosity on the flexural strength of 3Y-TZP bioceramics fabricated by direct write assembly technology.
Methods
A printable ink containing a volume fraction of 45% of 3Y-TZP (ZrO2 stabilized with 3 mol% Y2O3) submicron powder, carboxymethyl cellul...
Robocasting is an extrusion-based additive manufacturing (AM) technique, highly explored in the fabrication of porous structures or thin-walled ceramics. Comparing to other slurry-based AM technologies, robocasting presents a high potential to produce dense bulk ceramics, thanks to the low organic binder contents and high solids loading used in the...
A calcium phosphate (CaP)-based scaffold used as synthetic bone grafts, which smartly combines precise dimensions, controlled porosity and therapeutic functions, presents benefits beyond those offered by conventional practices, although its fabrication is still a challenge. The sintering step normally required to improve the strength of the ceramic...
Advances on the fabrication of sintering-free biphasic calcium phosphate (BCP)/natural polymer composite scaffolds using robocasting as additive manufacturing technique are presented in the present work. Inks with high amounts of BCP powders (45 vol%) containing different HA/β-TCP ratios, in presence of crosslinked polymer, were successfully fine-t...
Alpha-tricalcium phosphate (α-TCP) is a component of particular interest in the formulation of apatitic calcium phosphate based bone cements. During the setting reaction of this type of cements, a calcium deficient hydroxyapatite with composition similar to bone hydroxyapatite is formed. But the purity levels of the commercially available products...
Good mechanical properties and high injectability are the major requirements to ensure widespread application of calcium phosphate cements (CPCs) as bone substitutes in minimally invasive surgeries. However, obtaining CPCs that exhibit a good compromise between these two properties as well as good biological performance is still a great challenge....
Alpha and beta-tricalcium phosphates are allotropic phases which play a very important role as bone graft substitutes, namely in calcium phosphate cements. Despite extensive research efforts, contradictory reports exist on the importance of quenching for maintaining α-TCP purity. The role of calcium pyrophosphate impurities derived from a certain c...
The present study discloses a systematic study about the influence of some relevant experimental variables on injectability of calcium phosphate cements. Non-reactive and reactive pastes were prepared, based on tricalcium phosphate doped with 5 mol% (Sr-TCP) that was synthesized by co-precipitation. The varied experimental parameters included: (i)...
The influence of ionic substituents in calcium phosphates intended for bone and tooth replacement biomedical applications is an important research topic, owing to the essential roles played by trace elements in biological processes. The present study investigates the mechanical and biological evaluation of ionic doped hydroxyapatite/β-tricalcium ph...
The present study investigated the in vitro performance of brushite-forming Zn- and ZnSr-substituted beta-TCP bone cements in terms of wet mechanical strength and biological response. Quantitative phase analysis and structural refinement of the powdered samples were performed by X-ray powder diffraction and Rietveld refinement technique. Initial an...
The core aim of this study was to investigate zinc (Zn)- and zinc and strontium (ZnSr)-containing brushite-forming beta-tricalcium phosphate (TCP) cements for their effects on proliferation and differentiation of osteoblastic-like cells (MC3T3-E1 cell line) as well as for their in vivo behaviour in trabecular bone cylindrical defects in a pilot stu...
The fabrication of complex-shaped alumina ceramics following a new near-net shape technique based on hydrolysis induced aqueous gelcasting (GCHAS) is reported in this paper. Aqueous suspension containing 50 vol.% solids loading was prepared by dispersing alumina in an aqueous solution of methacrylamide and methlynebisacrylamide (17 wt.% in 6:1) usi...
This paper reports on the synthesis of magnesium aluminate spinel (MAS) powders and consolidation of MAS ceramics by hydrolysis-induced aqueous gelcasting (GCHAS). The MAS powders surface passivated against hydrolysis were dispersed in an aqueous–organic premix solution using suitable dispersants. The consolidation of green bodies occurred under am...
This paper reports on process dependant microstructural and mechanical properties of MgAl2O4 spinel (MAS) ceramics. Two MAS powders with different chemical compositions were synthesized by solid-state reaction of alumina and calcined caustic magnesia at 1400 °C for 1 h. The surface of the as obtained MAS powders was passivated against hydrolysis by...
The synthesis of five different Sr2+- and Mg2+-co-substituted β-tricalcium phosphate (β-TCP) has been obtained by heating the calcium-deficient apatites above 800°C. With the investigated concentrations of Sr2+ and Mg2+ from the present study, no additional phases other than β-TCP have been detected. The synthesized powders have been characterized...
New bone cements made of Sr-substituted brushite-forming alpha-tricalcium phosphate (alpha-TCP) were prepared and characterized in the present work. The quantitative phase analysis and structural refinement of the starting powders and of hardened cements were performed by X-ray powder diffraction and the Rietveld refinement technique. Isothermal ca...
The influence of magnesium- and strontium-substitutions on injectability and mechanical performance of brushite-forming alpha-TCP cements has been evaluated in the present work. The effects of Mg- and Sr-substitutions on crystalline phase composition and lattice parameters were determined through quantitative X-ray phase analysis and structural Rie...
The present study is an attempt to enhance the apatite-forming ability of titanium metal induced by the alkaline (NaOH) treatment. A cell free culture medium, acellular DMEM solution was utilised to develop bone-like apatite on alkali-treated titanium alloy surface. The main advantage of this process is the development of bone like apatite with ess...
A new near-net shape forming process called “hydrolysis-induced aqueous gelcasting” (GCHAS) is reported in this paper for the consolidation of ZTA composites, ZTA-30 (70wt.% Al2O3+30wt.% ZrO2) and ZTA-60 (40wt.% Al2O3+60wt.% ZrO2). For comparison purposes, ceramics having the same chemical compositions were also consolidated by hydrolysis-assisted...
Nanocrystalline Al2O3 powders containing different amounts of MgO (0.1–5.0 mol%) or added boehmite (AlOOH) have been synthesized by combustion synthesis from aluminium nitrate and magnesium nitrate, using urea or sucrose as fuels. The as synthesized alumina powders were deagglomerated, compacted by dry pressing and sintered at 1625 °C for 2 h. For...
Investigations of the electronic structures of substituted strontium apatites were carried out by using X-ray photo electron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction technique (XRD) has been used to determine the structural parameters. Electron microprobe microanalysis technique was used to estima...
The aim of this work is to evaluate the effects of incorporating river silt originated from washing silica sands extracted in "Ria de Aveiro" as a raw material in the manufacturing process of traditional ceramic building products such as bricks and tiles and on their final properties. The solid river silt waste was physicochemicaliy characterized f...
A stoichiometric MgAl2O4 spinel (MAS) powder was processed in aqueous media and consolidated by gelcasting from suspensions containing 41–45 vol% solids loading. The MAS powder was first obtained by heat treating a compacted mixture of α-Al2O3 and calcined caustic MgO at 1400°C for 1 h, followed by crushing and milling. Then, its surface was passiv...
The present work aimed at studying the incorporation of wastes from natural rock cutting and polishing to produce roof tiles. The sintered products incorporating the sludge were targeted to have similar or even enhanced properties in comparison to those made of a standard reference paste industrially used to fabricate concurrent products available...
Two different zirconia-alumina composites, ZTA-30 (70 wt% Al2O3+30 wt% ZrO2) and ZTA-60 (40 wt% Al2O3+60 wt% ZrO2), with potential for orthopedic applications, were processed in aqueous media and consolidated by slip casting (SC), hydrolysis-assisted solidification (HAS), and gelcasting (GC) from suspensions containing 50 vol% solids loading. For c...
A stoichiometric MgAl 2O 4 spinel (MAS) powder was synthesized by heat treating at 1400 degrees C for 2 h a compacted mixture of alpha-Al 2O 3 and calcined caustic MgO, followed by crushing and milling. The surface of this powder was then passivated against hydrolysis with H 3PO 4 and Al(H 2PO 4) 3 in an ethanol solution. The as-passivated powder c...
In the present work, industrial sludges derived from cutting and polishing natural stones (granite and quartzite) were characterised in terms of particles size distribution, chemical and mineralogical composition, and thermal behaviour and their potential to be incorporated as main components in red-clay-based stoneware tiles was evaluated. High le...
Granite wastes in the form of sludge, obtained from granite cutting industry, were incorporated in the batch formulations of porcelain tiles. The maximum possible substitution of sludge for feldspar was investigated. Samples of different formulations, in the form of pellets or extruded bars, were produced at both laboratory and pilot-plant scales a...
This work reports the use of sludge generated from natural granite cutting processes as raw material in brick- type and floor tile-type ceramic formulations. The physico-chemical and mineralogical characterization of the sludge was carried out in order to identify the major technological constraints and to define the sludge pre- treatment requireme...