A carregar...
Projeto de investigação
Sem título
Financiador
Autores
Publicações
Experimental study of Double-Elliptic-Ring-based thermomechanical metamaterials’ behaviour
Publication . Cardoso, João O.; Catatão, Gonçalo; Borges, João Paulo; Velhinho, Alexandre; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Elsevier
In recent years there has been increased interest in 3D thermomechanical metamaterials. The current work reports the design, fabrication and testing of a novel anisotropic anepectic metamaterial obtained by grafting inserts of a second material into a known auxetic structure, the Double Elliptic Ring (DER). While auxetics have a Negative Poisson's Ratio (NPR), anepectics combine this with a negative coefficient of thermal expansion (NTE). To avoid unnecessary time and material expenditure during the additive manufacturing (AM) stage, mechanical and thermal finite element simulations (FEA) were used as a tool to screen the multitude of possible design variants under consideration, thus aiding in rapidly determining the more promising geometries. To further increase the efficiency during AM, the selected structures were then assembled from planar elements, joined together with an adhesive. In the end, through the combination of two conventional materials – PVA and Nylon – of positive Poisson's ratio (PR) and coefficient of thermal expansion (CTE) organized in the DER architecture, it was possible to achieve the desired NPR and CTE behaviour along some directions, coupled with positive values in other directions. Experimental results revealed a correlation between PR values and the number of cells in the structure and showed that, while NPR values are essentially determined by the metamaterial's geometry, the induction of NTE results from a subtle interaction of geometry and the properties mismatch between the constitutive materials.
Dynamical processes and order behind the pronounced 1H NMR paramagnetic relaxation enhancement induced in [P6,6,6,14]3[GdCl6]-based ionic liquid mixtures
Publication . Beira, Maria J.; Silva, Gonçalo M.C.; Eusébio, Tiago M.; Figueirinhas, João L.; Cordeiro, Rui; Cruz, Carlos; Corvo, Marta C.; Almeida, Pedro L.; Rosatella, Andreia A.; Afonso, Carlos A.M.; Filipe, Eduardo J.M.; Parella, Teodor; Cabrita, Eurico J.; Sebastião, Pedro J.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Faculdade de Ciências e Tecnologia (FCT); UCIBIO - Applied Molecular Biosciences Unit; DQ - Departamento de Química; Elsevier
NMR relaxometry is a technique that allows the molecular dynamics study of chemical compounds across a broad time scale, ranging from slow translational diffusion or collective motions to fast rotations. The present work is a 1H NMR relaxometry and diffusometry study of systems based on [P6,6,6,14][Cl] and [P6,6,6,14]3[GdCl6] ionic liquids, complemented by X-ray diffractometry measurements. The use of the X-ray profiles enabled the determination of an almost temperature independent interdigitated disposition of the cations that is at the origin of local order fluctuations. This structure also affects the paramagnetic relaxation enhancement, which is very significant for these systems and is achieved at very low metal concentrations (around 1mM). The present study provides a comprehensive analysis that is consistent for all the analyzed systems and across the different experimental techniques, despite the experienced technical challenges related to extremely short relaxation times. Additionally, the Electrochemical Impedance Spectroscopy profiles of the neat [P6,6,6,14][Cl] sample were explained by an analogous equivalent circuit model that allowed for a global analysis consistent with the diffusometry and X-ray diffractometry results. The representation of the real and imaginary parts of the impedance allowed for a visual deconvolution of the contributions of the different circuit blocks considered in the model.
Unidades organizacionais
Descrição
Palavras-chave
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
Financiamento do Plano Estratégico de Unidades de I&D - 2019
Número da atribuição
UID/CTM/50025/2019