Synthesis and Characterisation of Acrylic Resin-Al Powder Composites Suitable for Additive Manufacturing

Stereolithography is an additive manufacturing technology commonly used to build either prototypes or final parts. Nevertheless, the manufacture of structural parts has been ruled out owing to the poor mechanical properties of conventional UV-curable resins. Moreover, the inventory of available commercial resins is still limited and they exhibit low thermal and electrical conductivity values. In this work, some composite materials were designed using Al microparticles dispersed within an SLA commercial resin matrix. These composites overcame the difficulties caused by the light scattering effect during the photopolymerisation process in the SLA technology. Dispersion of the filler was characterised by means of SEM/EDX and AFM. The composites exhibited improved thermal and mechanical behaviour in comparison with the pristine resin. The simplicity of the synthesis method used to prepare the composites provides a convenient starting point to explore new ways of designing composites for SLA with improved mechanical and functional properties

Biomasa para producción de composites de base polimérica y su implementación en fabricación aditiva

En un contexto de creciente sensibilización hacia la conservación del medio ambiente, la demanda de uso de materiales sostenibles está abriendo nuevas oportunidades de investigación en torno a la aplicación de materiales de origen natural y carácter renovable. Este planteamiento enlaza con el concepto de economía circular, donde unos materiales a fin de su vida útil son reutilizados en una nueva cadena de fabricación, proporcionando un nuevo ciclo de vida. En este sentido, la aplicación de biomasa como material con vocación de uso estructural ha concitado la atención científica reciente. La biomasa, o materia procedente del reino vegetal, está principalmente compuesta por biopolímeros entre los que destacan la celulosa, hemicelulosa y lignina, que constituyen la denominada fracción lignocelulósica. Existe un buen número de referencias en la bibliografía de usos de la lignocelulosa presente en la biomasa, en particular tras su adición a matrices poliméricas en forma de composites. Sin embargo, los tratamientos de purificación de la biomasa suelen ser costosos y no respetuosos con el medio ambiente. Por su parte, las técnicas de fabricación aditiva superan algunas desventajas conocidas de la fabricación sustractiva convencional, contribuyendo al concepto de economía circular, toda vez que permiten economizar etapas de fabricación y desperdicio de material. En esta revisión, se repasan las aportaciones científicas y tecnológicas más recientes en torno a la preparación de composites de base polimérica incluyendo biomasa, en particular aquéllas que tienen aplicación en fabricación aditiva. Se plantea la problemática en torno a la purificación de la fracción lignocelulósica o el uso directo de agro residuos, entre otros materiales naturales, sin pretratamiento o con sencillos tratamientos de compatibilización que aseguren la mejor adhesión entre la biomasa y los polímeros. Se concluye la revisión resaltando aquellas contribuciones actuales referentes al uso de estos materiales composites en fabricación aditiva.In a context of an increasingly environmental awareness, the demand for use of sustainable materials is providing new research opportunities around the usage of renewable materials with natural origin. This approach fits with the circular economy concept, where materials at the end of their lifecycle are reused within a new manufacturing chain, thus bearing a new lifecycle. In this regard, biomass implementation as a material, even intended for structural purposes, has drum up recent scientific interest. Biomass, matter coming from vegetal reign, is mainly composed by biopolymers among which highlight cellulose, hemicellulose and lignin. These biopolymers constitute the so called lignocellulosic fraction. There are many references in bibliography about uses of the lignocellulose present in biomass, particularly after its addition to polymeric matrices in the form of composites. Nevertheless, biomass purification processes are expensive and non-eco-friendly. On the other hand, additive manufacturing techniques overcome known disadvantages of conventional subtractive manufacturing, thus contributing to the circular economy concept, since they allow optimising manufacturing stages and material waste. In this review the most recent scientific and technological considerations about polymer based composites including biomass, particularly those suitable for additive manufacturing, have been gone over. It is also posed the question about purifying the lignocellulosic fraction or direct use of agrowaste, among other natural materials, without pre-treatment or applying simple compatibilisation procedures, thus assuring the better adhesion between biomass and polymers. The review concludes highlighting those recent works related to the usage of these composite materials in additive manufacturing.Los autores agradecen la financiación europea, nacional y regional que ha permitido realizar en el último lustro varios proyectos relacionados con el desarrollo de materiales, diseño y fabricación aditiva (Fondos europeos ITI, Junta de Andalucía –proyectos ADICORK, NANOCOMP, 3DMATFUN, TERPOL3D-, MINECO/MICINN/AEI –proyectos LNL-PHOTON, OPTONANO, EXPLORA MEDEA, 3DBLEND-, Instituto de Salud Carlos III –proyecto VASCULAR3D-, FECYT –HOSPITAL 3D, fondos FEDER, IMEYMAT, DFA-SCICyT, DMP-CTE Olivillo, Grupo INNANOMAT/TEP946, etc.). En muchos de estos proyectos las aportaciones relacionadas con materiales sostenibles y en particular con aquellos que incorporan biomasa son de especial interés para su desarrollo. Los investigadores J. J. Relinque e I. Romero desean agradecer sus vinculaciones contractuales post-doctorales respectivas con financiación nacional, Margarita Salas-U y Plan Propio de la UCA

Photocatalytic valorization of ethanol and glycerol over TiO2 polymorphs for sustainable hydrogen production

Photocatalytic reforming of renewable raw materials in aqueous solutions represents a valid possibility for the valorization of wastes from agricultural and industrial processes. In this study, we prepared TiO2 materials with different phase compositions by changing the urea/Ti molar ratio employed during the hydrothermal preparation method. After deposition of Pt nanoparticles, the photocatalytic H-2 production was investigated using ethanol and glycerol as sustainable sacrificial agent. While anatase/rutile nanocomposites showed poor catalytic activity, the anatase/brookite nanocomposites showed more promising performances. Specifically, the anatase-rich materials showed the best performances on mass bases. When normalized with respect to the surface area of the photocatalysts, the activity continuously increased with the brookite content, indicating that exposed facets of brookite possess an intrinsic higher activity than that of the other polymorphs

Stereolithography of Semiconductor Silver and Acrylic-Based Nanocomposites

Polymer nanocomposites (PNCs) attract the attention of researchers and industry because of their potential properties in widespread fields. Specifically, electrically conductive and semiconductor PNCs are gaining interest as promising materials for biomedical, optoelectronic and sensing applications, among others. Here, metallic nanoparticles (NPs) are extensively used as nanoadditives to increase the electrical conductivity of mere acrylic resin. As the in situ formation of metallic NPs within the acrylic matrix is hindered by the solubility of the NP precursors, we propose a method to increase the density of Ag NPs by using different intermediate solvents, allowing preparation of Ag/acrylic resin nanocomposites with improved electrical behaviour. We fabricated 3D structures using stereolithography (SLA) by dissolving different quantities of metal precursor (AgClO4) in methanol and in N,N-dimethylformamide (DMF) and adding these solutions to the acrylic resin. The high density of Ag NPs obtained notably increases the electrical conductivity of the nanocomposites, reaching the semiconductor regime. We analysed the effect of the auxiliary solvents during the printing process and the implications on the mechanical properties and the degree of cure of the fabricated nanocomposites. The good quality of the materials prepared by this method turn these nanocomposites into promising candidates for electronic applications

Photocatalytic TiO2 nanosheets-SiO2 coatings on concrete and limestone: An enhancement of de-polluting and self-cleaning properties by nanoparticle design

8siIn this study, we develop TiO2-SiO2 nanocomposites that can be employed as photoactive coatings to create surfaces with antipollution and self-cleaning properties in urban buildings. In particular, anatase titanium dioxide with a high percentage of {0 0 1} facets, commonly called titania nanosheet (TNS), was used as active phase. This approach allows us to improve the antipollution properties of similar sols based on P25. The obtained TNS were intensively characterized by UV–Vis diffuse reflectance absorption, X-Ray diffraction and transmission electron microscopy to rationalize the sol synthesis and fully understand the photocatalytic performances. Our results clearly show that after treating the titania nanosheets with NaOH to remove adsorbed residual fluoride from the synthesis, they can be easily dispersed and the photocatalytic activity is dramatically improved. This material has been shown to effectively reduce concentrations of NOx, soot and organic dyes under simulated sun light radiation.nonemixedLuna, M.; Delgado, J.J.; Romero, I.; Montini, T.; Almoraima Gil, M.L.; Martínez-López, J.; Fornasiero, P.; Mosquera, M.J.Luna, M.; Delgado, J. J.; Romero, I.; Montini, T.; Almoraima Gil, M. L.; Martínez-López, J.; Fornasiero, P.; Mosquera, M. J

Comprehensive analysis and insights gained from long-term experience of the Spanish DILI Registry

Altres ajuts: Fondo Europeo de Desarrollo Regional (FEDER); Agencia Española del Medicamento; Consejería de Salud de Andalucía.Background & Aims: Prospective drug-induced liver injury (DILI) registries are important sources of information on idiosyncratic DILI. We aimed to present a comprehensive analysis of 843 patients with DILI enrolled into the Spanish DILI Registry over a 20-year time period. Methods: Cases were identified, diagnosed and followed prospectively. Clinical features, drug information and outcome data were collected. Results: A total of 843 patients, with a mean age of 54 years (48% females), were enrolled up to 2018. Hepatocellular injury was associated with younger age (adjusted odds ratio [aOR] per year 0.983; 95% CI 0.974-0.991) and lower platelet count (aOR per unit 0.996; 95% CI 0.994-0.998). Anti-infectives were the most common causative drug class (40%). Liver-related mortality was more frequent in patients with hepatocellular damage aged ≥65 years (p = 0.0083) and in patients with underlying liver disease (p = 0.0221). Independent predictors of liver-related death/transplantation included nR-based hepatocellular injury, female sex, higher onset aspartate aminotransferase (AST) and bilirubin values. nR-based hepatocellular injury was not associated with 6-month overall mortality, for which comorbidity burden played a more important role. The prognostic capacity of Hy's law varied between causative agents. Empirical therapy (corticosteroids, ursodeoxycholic acid and MARS) was prescribed to 20% of patients. Drug-induced autoimmune hepatitis patients (26 cases) were mainly females (62%) with hepatocellular damage (92%), who more frequently received immunosuppressive therapy (58%). Conclusions: AST elevation at onset is a strong predictor of poor outcome and should be routinely assessed in DILI evaluation. Mortality is higher in older patients with hepatocellular damage and patients with underlying hepatic conditions. The Spanish DILI Registry is a valuable tool in the identification of causative drugs, clinical signatures and prognostic risk factors in DILI and can aid physicians in DILI characterisation and management. Lay summary: Clinical information on drug-induced liver injury (DILI) collected from enrolled patients in the Spanish DILI Registry can guide physicians in the decision-making process. We have found that older patients with hepatocellular type liver injury and patients with additional liver conditions are at a higher risk of mortality. The type of liver injury, patient sex and analytical values of aspartate aminotransferase and total bilirubin can also help predict clinical outcomes