Search results for " Materiale"
showing 10 items of 139 documents
L'Architettura è resiliente?
2022
Il contributo indaga specificatamente sul termine "Resilienza" ormai inflazionato a più usi e livelli . In vero ci si domanda come e quando l'architettura possa esser resiliente giacché appare non esserlo : "una architettura rotta, rotta è, e rotta rimane" senza possibilità di azioni che in autonomia la rigenerino. L’atto del costruire deve essere sempre atto nobile ma soprattutto responsabile, usando e scegliendo tecniche e tecnologie ‘adattive’ che pongano soluzioni sostenibili lontane dagli esercizi di stile in cui l’Architettura spesso si diletta (Lerner, 2012). Un positivo contributo alla ricerca della resilienza in Architettura potrebbe essere individuato forse nei materiali che la co…
Oxamato/Oxamidato-Based Multifunctional Porous Coordination Polymers
2017
El principal objetivo de esta presente Tesis concierne el diseño y la síntesis de materiales multifuncionales, una línea de investigación de creciente interés dentro del campo de la Química de Materiales. Para llevar a cabo dicho objetivo, hemos aprovechado los avances que ha experimentado la química metalosupramolecular en los últimos años. Concretamente pretendemos hacer uso de los métodos de auto-ensamblaje programado basado en las diferentes preferencias que muestran los iones metálicos en sus entornos de coordinación y en la funcionalización de ligandos orgánicos. Para ello, hemos sintetizado ligandos derivados de grupos oxamato y oxamidato, que actuarán como moléculas de partida para …
Protocolo para la evaluación y elección de materiales curriculares digitales
2016
El uso o no del libro de texto, y si ha de ser en formato impreso o digital, es una decisión importante en el planteamiento pedagógico del docente y, en consecuencia, en las prácticas de aula. En ese sentido, presentar una propuesta de criterios pedagógicos, tecnológicos y económicos para la selección de los materiales didácticos curriculares en formato digital puede ser de gran utilidad a los centros de enseñanza. Dichos criterios sirven de punto de partida en el proceso de reflexión que deberán iniciar para la selección de los materiales. Entendemos que lo primero que han de preguntarse, refiriéndonos a los libros de texto en general, es dónde situarlos en el proceso de enseñanza y aprend…
Heterogeneous nucleation of a droplet pinned at a chemically inhomogeneous substrate: A simulation study of the two-dimensional Ising case
2018
Heterogeneous nucleation is studied by Monte Carlo simulations and phenomenological theory, using the two-dimensional lattice gas model with suitable boundary fields. A chemical inhomogeneity of length b at one boundary favors the liquid phase, while elsewhere the vapor is favored. Switching on the bulk field Hb favoring the liquid, nucleation and growth of the liquid phase starting from the region of the chemical inhomogeneity are analyzed. Three regimes occur: for small fields, Hb bcrit, the critical droplet radius is so large that a critical droplet having the contact angle θc required by Young's equation in the region of the chemical inhomogeneity does not yet "fit" there since the base…
Curvature as a Guiding Field for Patterns in Thin Block Copolymer Films
2018
Experimental data on thin films of cylinder-forming block copolymers (BC)—free-standing BCmembranes as well as supported BC films—strongly suggest that the local orientation of the BC patternsis coupled to the geometry in which the patterns are embedded. We analyze this phenomenon using generalsymmetry considerations and numerical self-consistent field studies of curved BC films in cylindricalgeometry. The stability of the films against curvature-induced dewetting is also analyzed. In goodagreement with experiments, we find that the BC cylinders tend to align along the direction of curvature athigh curvatures. At low curvatures, we identify a transition from perpendicular to parallel alignm…
Diffusivity and free anion concentration of ionic liquid composite polybenzimidazole membranes.
2021
[EN] In this article, PBI composite membranes containing the ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-NTf2) at 1, 5, 10, 20 and 50 wt% (named PBI-IL-x) have been prepared by a casting method. The internal morphology of the membranes was analyzed by scanning electron microscopy (SEM), revealing that the incorporation of IL promotes the formation of porous channels. Thermal and mechanical stability was confirmed by thermogravimetric analysis (TGA) and tensile test measurements. The ionic transport through membranes was analysed by means of electrochemical impedance spectroscopy (EIS), showing a dependence on the IL loading, reaching a highest condu…
Enhanced Conductivity of Composite Membranes Based on Sulfonated Poly(Ether Ether Ketone) (SPEEK) with Zeolitic Imidazolate Frameworks (ZIFs)
2018
The zeolitic imidazolate frameworks (ZIFs) ZIF-8, ZIF-67, and a Zn/Co bimetallic mixture (ZMix) were synthesized and used as fillers in the preparation of composite sulfonated poly(ether ether ketone) (SPEEK) membranes. The presence of the ZIFs in the polymeric matrix enhanced proton transport relative to that observed for SPEEK or ZIFs alone. The real and imaginary parts of the complex conductivity were obtained by electrochemical impedance spectroscopy (EIS), and the temperature and frequency dependence of the real part of the conductivity were analyzed. The results at different temperatures show that the direct current (dc) conductivity was three orders of magnitude higher for composite …
Effective antimicrobial materials based on low-density polyethylene (LDPE) with zinc oxide (ZnO) nanoparticles
2019
[EN] Effective antimicrobial polymeric nanocomposites were prepared with low density polyethylene (LDPE) and zinc oxide nanoparticles by melt compounding. These nanoparticles (~17 nm) obtained by the sol¿gel method, were used both as-synthesized and modified organically with oleic acid (Mod-ZnO). Young¿s modulus increased ~15 and 18% for LDPE/ZnO and LDPE/Mod-ZnO, respectively, compared to neat LDPE. When these composites were irradiated with white light, they showed an increase with nanoparticle incorporation, and the antimicrobial properties against E. coli were ~96¿99%. The release of the Zn cations was related to the antimicrobial properties. These nanocomposites are attractive for use …
Nanorings and rods interconnected by self-assembly mimicking an artificial network of neurons
2013
[EN] Molecular electronics based on structures ordered as neural networks emerges as the next evolutionary milestone in the construction of nanodevices with unprecedented applications. However, the straightforward formation of geometrically defined and interconnected nanostructures is crucial for the production of electronic circuitry nanoequivalents. Here we report on the molecularly fine-tuned self-assembly of tetrakis-Schiff base compounds into nanosized rings interconnected by unusually large nanorods providing a set of connections that mimic a biological network of neurons. The networks are produced through self-assembly resulting from the molecular conformation and noncovalent intermo…
Defect spectroscopy of single ZnO microwires
2014
The point defects of single ZnO microwires grown by carbothermal reduction were studied by microphotoluminescence, photoresistance excitation spectra, and resistance as a function of the temperature. We found the deep level defect density profile along the microwire showing that the concentration of defects decreases from the base to the tip of the microwires and this effect correlates with a band gap narrowing. The results show a characteristic deep defect levels inside the gap at 0.88 eV from the top of the VB. The resistance as a function of the temperature shows defect levels next to the bottom of the CB at 110 meV and a mean defect concentration of 4 1018 cm3 . This combination of tech…