Search

Your search keyword '"Vilarinho, Paula"' showing total 711 results
Start Over Author "Vilarinho, Paula" Publication Year Range Last 50 years

Refine your results

711 results on '"Vilarinho, Paula"'

1. Scandium doped Strontium Titanate Ceramics: Structure, Microstructure, and Dielectric Properties

Author

Tkach, Alexander and Vilarinho, Paula M.

Subjects
Dopants, Microstructure, Electric/Dielectric properties, Insulators, Strontium Titanate, Ceramics, Dopantes, microestructura, propiedades eléctricas-dieléctricas, aislantes, titanato de estroncio, cerámica, Clay industries. Ceramics. Glass, TP785-869
Abstract

Sc-doped strontium titanate (ST) ceramics were synthesised by solid state reaction, according to the composition Sr1-1.5xScxTiO3 with x = 0-0.01. Structural properties and microstructure development was examined by XRD and SEM. The dielectric properties were evaluated as a function of the temperature and frequency in the radio frequency range. Lattice parameter, density and grain size, were found to decrease slightly with increasing Sc content. The dielectric permittivity and losses decrease also. Sc-doping has only a weak effect on the quantum paraelectric behaviour of ST and no dielectric anomaly was observed, what is probably related to the limited solubility of Sc on the Sr site of the perovskite lattice of ST.Se sintetizaron materiales cerámicos de titanato de estroncio dopado con escandio mediante reacción en estado sólido De acuerdo a la composición Sr1-1.5xScxTiO3 con x= 0-0.1. Las propiedades estructurales y el desarrollo microestructural se estudiaron mediante XRD y SEM. La propiedades dieléctricas se estudiaron como función de la temperatura y de la frecuencia en el rango de la frecuencias de radio. Se observó que los parámetros de red, la densidad y el tamaño del grano disminuyen ligeramente con el contenido en Sc. La permitividad dieléctrica y las perdidas también disminuyen. El dopado con Sc tiene un efecto muy ligero sobre el comportamiento paraeléctrico cuántico del titanato de estroncio y no se observó anomalías dioeléctricas , lo que está probablemente relacionado con la baja solubilidad del Sc en posiciones del Sr en la estructura tipo perovskita del titanato de estroncio.

Published
2008

26. Stimuli-Responsive Oligourea Molecular Films

Author

Grempka, Arkadiusz, Dziubak, Damian, Puszko, Anna K., Bachurska-Szpala, Paulina, Ivanov, Maxim, Vilarinho, Paula M., Pulka-Ziach, Karolina, and Sek, Slawomir

Abstract

We have designed and synthesized a helical cysteamine-terminated oligourea foldamer composed of ten urea residues featuring side carboxyl and amine groups. The carboxyl group is located in proximity to the C-terminus of the oligourea and hence at the negative pole of the helix dipole. The amine group is located close to the N-terminus and hence at the positive pole of the helix dipole. Beyond the already remarkable dipole moment inherent in oligourea 2.5 helices, the incorporation of additional charges originating from the carboxylic and amine groups is supposed to impact the overall charge distribution along the molecule. These molecules were self-assembled into monolayers on a gold substrate, allowing us to investigate the influence of an electric field on these polar helices. By applying surface-enhanced infrared reflection–absorption spectroscopy, we proved that molecules within the monolayers tend to reorient themselves more vertically when a negative bias is applied to the surface. It was also found that surface-confined oligourea molecules affected by the external electric field tend to rearrange the electron density at urea groups, leading to the stabilization of the resonance structure with charge transfer character. The presence of the external electric field also affected the nanomechanical properties of the oligourea films, suggesting that molecules also tend to reorient in the ambient environment without an electrolyte solution. Under the same conditions, the helical oligourea displayed a robust piezoresponse, particularly noteworthy given the slender thickness of the monolayer, which measured approximately 1.2 nm. This observation demonstrates that thin molecular films composed of oligoureas may exhibit stimulus–responsive properties. This, in turn, may be used in nanotechnology systems as actuators or functional films, enabling precise control of their thickness in the range of even fractions of nanometers.

Published
2024
Full Text
View/download PDF

42. Advanced Cellulose–Nanocarbon Composite Films for High-Performance Triboelectric and Piezoelectric Nanogenerators

Author

Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Ministerio de Ciencia e Innovación (España), European Commission, European Research Council, Fundação para a Ciência e a Tecnologia (Portugal), González, Jaime, Ghaffarinejad, Ali, Ivanov, Maxim, Ferreira, Paula, Vilarinho, Paula M., Borrás, Ana, Amorín, Harvey, Wicklein, Bernd, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Ministerio de Ciencia e Innovación (España), European Commission, European Research Council, Fundação para a Ciência e a Tecnologia (Portugal), González, Jaime, Ghaffarinejad, Ali, Ivanov, Maxim, Ferreira, Paula, Vilarinho, Paula M., Borrás, Ana, Amorín, Harvey, and Wicklein, Bernd

Abstract

Natural polymers such as cellulose have interesting tribo- and piezoelectric properties for paper-based energy harvesters, but their low performance in providing sufficient output power is still an impediment to a wider deployment for IoT and other low-power applications. In this study, different types of celluloses were combined with nanosized carbon fillers to investigate their effect on the enhancement of the electrical properties in the final nanogenerator devices. Cellulose pulp (CP), microcrystalline cellulose (MCC) and cellulose nanofibers (CNFs) were blended with carbon black (CB), carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). The microstructure of the nanocomposite films was characterized by scanning electron and probe microscopies, and the electrical properties were measured macroscopically and at the local scale by piezoresponse force microscopy. The highest generated output voltage in triboelectric mode was obtained from MCC films with CNTs and CB, while the highest piezoelectric voltage was produced in CNF-CNT films. The obtained electrical responses were discussed in relation to the material properties. Analysis of the microscopic response shows that pulp has a higher local piezoelectric d33 coefficient (145 pC/N) than CNF (14 pC/N), while the macroscopic response is greatly influenced by the excitation mode and the effective orientation of the crystals relative to the mechanical stress. The increased electricity produced from cellulose nanocomposites may lead to more efficient and biodegradable nanogenerators.

Published
2023

44. Correction to: Strain Effect on the Properties of Polar Dielectric Thin Films

Author

Tkach, Alexander, Okhay, Olena, Santos, André, Zlotnik, Sebastian, Serrazina, Ricardo, Vilarinho, Paula M., Costa, M. Elisabete, Chaari, Fakher, Series Editor, Gherardini, Francesco, Series Editor, Ivanov, Vitalii, Series Editor, Cavas-Martínez, Francisco, Editorial Board Member, di Mare, Francesca, Editorial Board Member, Haddar, Mohamed, Editorial Board Member, Kwon, Young W., Editorial Board Member, Trojanowska, Justyna, Editorial Board Member, Xu, Jinyang, Editorial Board Member, Pogrebnjak, Alexander D., editor, and Novosad, Valentine, editor

Published
2019
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results