Abstract

The diffusion or permeability of ions or gases through the cement matrix is key in the degradation of reinforced concrete for marine applications. The delay in ion diffusion has been an important approach to extend the life of this type of materials. In this work it is detailed how reduce degradation of cement mortar using nanotechnology. The addition of nanoparticles to the cement paste has important implications for the hydration and microstructure, reducing porosity and improving mechanical properties. In this study, different nanoparticles have been used to reduce the porosity of mortars evaluating this improvement by means of electrical resistivity measurements. It is perfectly established the porosity reduction with the increasing of electrical resistivity. Reduction of porosity minimises the intake of aggressive agents into the mortar in a meaningful way, retarding the corrosion of metal reinforcement. Nanoparticles addition (<10%) within cement mortar have allowed to increase the electrical resistivity in up to 112% regarding to control sample, without modifying of mechanical properties.       

Abstract

This work deals with the development of flexible piezoelectric nanocomposites based on PVDF-HFP copolymer reinforced with ZnO nanoparticles (NPs) for biomedical sensing applications. Two fabrication techniques are analyzed: solvent casting and electrospinning. The films obtained by the solvent casting technique, characterized by FTIR-ATR and Atomic Force Microscopy (AFM) in PFM mode, show a significant increase of the piezoelectric coefficient (d₃₃) for ZnO NPs concentrations equal or higher than 12% by weight, with respect to the unreinforced polymeric matrix. FTIR analysis estimated an electroactive phase content close to 60% in the reinforced samples. On the other hand, the preliminary study of optimization of electrospinning parameters, evaluated by Scanning Electron Microscopy (SEM), demonstrates the feasibility of forming mats with high fiber content and homogeneous nanofiber diameters between 110-140 nm, whose morphology depends on parameters such as the speed of the collector. These preliminary results are promising for obtaining flexible piezoelectric fabrics by both fabrication routes.

Abstract

Las nanopartículas (Nps) de metales nobles como plata (Ag) y oro (Au) en las últimas décadas son objeto de extensa investigación en el contexto de las nanociencias y la nanotecnología, principalmente esto se debe a sus propiedades ópticas únicas. En las Nps, el gas de electrones libres en ellas presenta propiedades de oscilación resonante, fenómeno conocido como el plasmón superficial localizado (PSL). Al irradiarse las Nps en el ultravioleta y visible del espectro, la absorción óptica, depende fundamentalmente del material constitutivo, la geometría de la Nps y su entorno. La dispersión de la radiación electromagnética de una esfera, es definida por la Teoría de Mie. Los cálculos al usar esta teoría pueden llegar a ser largos e incluso imposibles para aquellos con recursos hardware limitados. Por lo tanto en esta investigación que actualmente, se encuentra en desarrolló, se diseño e implanto una simulación numérica escrita en Python 3 para la obtención de los coeficientes de Mie en nanopartículas de plata (Ag)  y contar con una herramienta computacional que generé escenarios permitiendo el estudio y obtención de los coeficientes de extinción de NPs de Ag, siendo esta metodología fácilmente adaptable para otros metales donde se pueden calcular y/o simular una variedad de propiedades ópticas.