Influence of Manufacturing Parameters and Post Processing on the Electrical Conductivity of Extrusion-Based 3D Printed Nanocomposite Parts

The influence of manufacturing parameters of filament extrusion and extrusion-based Additive Manufacturing (AM), as well as different post processing techniques, on the electrical conductivity of 3D printed parts of graphene nanoplatelets (GNP)-reinforced acrylonitrile butadiene styrene (ABS) has been analyzed. The key role of the manufacturing parameters to obtain electrically conductive filaments and 3D printed parts has been demonstrated. Results have shown that an increase in extrusion speed, as well as lower land lengths, induces higher extrudate swelling, with the consequent reduction of the electrical conductivity. Additionally, filaments with lower diameter values, which result in a higher surface-to-cross-section ratio, have considerably lower electrical conductivities. These factors tune the values of the volume and surface electrical conductivity between 10-4-100 S/m and 10-8-10-3 S/sq, respectively. The volume and surface electrical conductivity considerably diminished after 3D printing. They increased when using higher printing layer thickness and width and were ranging between 10-7-10-4 S/m and 10-8-10-5 S/sq, respectively. This is attributed to the higher cross section area of the individual printed lines. The effect of different post processing (acetone vapor polishing, plasma and neosanding, which is a novel finishing process) on 3D printed parts in morphology and surface electrical conductivity was also analyzed

Chemical and electrical properties of LSM cathodes prepared by mechanosynthesis

Mechanosynthesis of La1-xSrxMnO3 (x = 0, 0.25, 0.5, 0.75 and 1) was carried out at room temperature from stoichiometric mixtures of La2O3, Mn2O3 and SrO, obtaining monophasic powders with the perovskite structure. Physical properties of these materials and their chemical compatibility with the electrolyte yttria stabilized zirconia (YSZ), which depend strongly on the La/Sr ratio, were evaluated to corroborate availability to be implemented as cathode material in solid oxide fuel cells (SOFCs). Electrical conductivity values in air ranged between 100 and 400 S cm-1 in the temperature range of 25-850 C. Samples presented low reactivity with YSZ in the working temperature range (600-1000 C) maintaining the grain size small enough to preserve the catalytic activity for oxygen reduction.Gobierno de España MAT2010-1704

Porous Titanium surfaces to control bacteria growth: mechanical properties and sulfonated polyetheretherketone coating as antibiofounling approaches

Here, titanium porous substrates were fabricated by a space holder technique. The relationship between microstructural characteristics (pore equivalent diameter, mean free-path between pores, roughness and contact surface), mechanical properties (Young’s modulus, yield strength and dynamic micro-hardness) and bacterial behavior are discussed. The bacterial strains evaluated are often found on dental implants: Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The colony-forming units increased with the size of the spacer for both types of studied strains. An antibiofouling synthetic coating based on a sulfonated polyetheretherketone polymer revealed an effective chemical surface modification for inhibiting MRSA adhesion and growth. These findings collectively suggest that porous titanium implants designed with a pore size of 100–200 µm can be considered most suitable, assuring the best biomechanical and bifunctional anti-bacterial properties.University of Seville VI Plan Propio de Investigación y Transferencia—US 2018, I.3A

Synthesis and deposition of silver nanoparticles on porous titanium substrates for biomedical applications

Ti implants are highly biocompatible and allow orderly bone growth but, unfortunately, in the first five years after implantation, 5–10% of them fail due to poor osseointegration and to the presence of bacterial infections in prosthesis. Silver nanoparticles have been described to damage bacterial cell via prolonged release of Ag+ ions as a mode of action when immobilized on a surface. In this work, two routes to synthetize silver nanoparticles have been proposed including, on the one hand, a NaBH4-reduction and, on the other hand, a citrate-reduction combined with a stabilized biodegradable polymer. The deposition of these nanomaterials on porous Ti substrates previously fabricated using the space-holder technique (40 vol% and two size distributions, 100–200 and 355–500 μm) was investigated to aim for the best match. Before the deposition of nanoparticles accomplished by immersion, a silanization treatment of the substrate surface was carried out. After silver nanoparticles were deposited on the porous Ti substrates, microstructural characteristics and antibacterial behavior were evaluated against the proliferation of Staphylococcus aureus on the AgNPs functionalized substrates. Finally, the preliminary qualitative analysis showed the presence of inhibitory halos, being more relevant in the substrates with larger pores.Ministry of Science and Innovation of Spain PID2019-109371GB-I00Junta de Andalucía–FEDER (Spain) US-1259771Junta de Andalucía-Proyecto de Excelencia (Spain) P18-FR-203

re-habitar El Carmen : Un proyecto sobre patrimonio contemporáneo

El proyecto _re-HABITAR suponía para el propio proceder de la institución un avance más allá del reconocimiento, registro, inventario o protección patrimonial de la arquitectura del siglo XX y del Movimiento Moderno para posicionarse en la acción preventiva y conservativa de ese legado contemporáneo. Para ello, la praxis patrimonial se aferraba a un modelo: el de la vivienda social en España en la segunda mitad del siglo XX; a un caso concreto: el de la barriada de Nuestra Señora del Carmen (Recasens Méndez-Queipo de Llano, 1958); y a un requisito fundamental: analizar un objeto vivo y en uso, aún con la presencia de quienes lo vivieron y usaron desde su origen

Electrical Performance of Orthotropic and Isotropic 3YTZP Composites with Graphene Fillers

3 mol% yttria tetragonal zirconia polycrystal (3YTZP) composites with orthotropic or isotropic microstructures were obtained incorporating few layer graphene (FLG) or exfoliated graphene nanoplatelets (e-GNP) as fillers. Electrical conductivity was studied in a wide range of contents in two configurations: perpendicular (σꓕ) and parallel (σ//) to the pressing axis during spark plasma sintering (SPS). Isotropic e-GNP composites presented excellent electrical conductivity for high e-GNP contents (σꓕ ∼ 3200 S/m and σ// ∼ 1900 S/m for 20 vol% e-GNP), consequence of their misoriented distribution throughout the matrix. Optimum electrical performance was achieved in the highly anisotropic FLG composites, with high electrical conductivity for low contents (σꓕ ∼ 680 S/m for 5 vol%), percolation threshold below 2.5 vol% FLG and outstanding electrical conductivity for high contents (σꓕ ∼ 4000 S/m for 20 vol%), result of the high aspect ratio and low thickness of FLG.Ministerio de Ciencia e Innovación GC2018–101377-B-100, MCIN/AEI/ 10.13039/501100011033European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER) P20_01024Ministerio de Economía y Competitividad BES-2016- 078711Universidad de Sevilla USE-18740-

Highly efficient electrical discharge machining of yttria-stabilized zirconia ceramics with graphene nanostructures as fillers

Electrical-discharge machining (EDM) of advanced ceramics allows the miniaturization of parts with complex shapes. Since electrical conductivity is required, non-conductive ceramics need a conductive second phase. This work assesses the feasibility of industrial EDM in advanced yttria-stabilized tetragonal zirconia (3YTZP) composites with 20 vol% graphene nanostructures with different morphology using different EDM energies. The structural integrity of the graphene nanostructures, the roughness of the machined surfaces and the geometrical tolerances have been evaluated by Raman spectroscopy, confocal microscopy and scanning electron microscopy, showing that it is possible to obtain a stable and efficient EDM process in these composites using low electrode energies. The use of the largest and thickest graphene nanostructures led to the best performance in terms of EDM machinability, the smallest nanostructures produced the best surface finish for low electrode energy and the thinnest nanostructures allowed the highest material removal rate at medium energy in the compositesMinisterio de Ciencia e Innovación (MICIN). España PGC2018-101377-B-100European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER) P20_01024Junta de Andalucía P20_0102