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Projeto de investigação
Institute of Nanostructures, Nanomodelling and Nanofabrication
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Publicações
Preliminary Investigation of the Mechanical and Physical Properties of Natural Hydraulic Lime Grouts with Nano-Silica
Publication . Baltazar, Luis G.; Cardoso, João; DEC - Departamento de Engenharia Civil; MDPI - Multidisciplinary Digital Publishing Institute
Natural hydraulic lime-based grouts are often used in the structural consolidation of old stone masonry walls, mainly to re-establish the monolithic behaviour of masonry constructions. To ensure an adequate grouting operation, it is essential to have good fresh and hardened grout properties. The motivation of the present study was to examine the fresh and hardened properties of natural hydraulic lime grouts with nano-silica (NS) and silica fume (SF). The contribution of these materials and the dosage of a high range water reducer admixture (HRWR) were investigated on the rheological properties, water capillarity, open porosity and mechanical strength of injection grouts. The effects on rheology were analysed through plastic viscosity and yield stress. The results indicated that, even for reduced NS content, an increase in plastic viscosity and yield stress occurred, which required a higher HRWR content in order to not compromise the grout’s rheological performance. The results also showed that, when NS and SF were combined, a beneficial joint effect occurred, resulting in a substantial and positive change on the mechanical strength and microstructure of the hardened injection grouts. Taguchi’s method was used to optimize the grout’s formulation and to fulfil the required performance concerning the fresh and hardened state.
Impressão 3D de Materiais Supercondutores
Publication . Mendes, Diogo André Pereira; Pronto, Anabela; Ferreira, Isabel
Com o crescimento económico que se verifica, cresce também as emissões de gases poluentes provenientes da queima de combustíveis fósseis, sendo portanto um desafio energético diminuir a sua utilização e recorrer a meios alternativos para colmatar esta dependência, reduzindo assim a dependência energética nacional, os custos associados aos mesmos e levando ao crescimento económico do país. Esta redução pode passar pela utilização de novos materiais que permitam reduzir as perdas em serviço e assim o consumo energético, e por uma forma de os produzir que seja mais rápida, barata e mais fácil.
Os materiais supercondutores de alta temperatura são materiais que devido às suas características electromagnéticas, isto é o facto de transportarem corrente sem perdas ou com perdas muito pequenas, capacidade de ancorar fluxo ou o diamagnetismo perfeito permitem o desenvolvimento de novas tecnologias, indispensáveis para uma nova era de avanços, principalmente na área da energia. Aliar este tipo de materiais à impressão 3D, cada vez mais integrada no dia-a-dia, e que permite construir inúmeras peças de variados tamanhos e formatos, dependendo do tipo de material e método de deposição da mesma podem ser a solução para um vasto leque de problemas.
O objectivo deste trabalho é explorar a possibilidade de imprimir peças em 3D e materiais SC de alta temperatura, a partir da extrusão de uma pasta constituída por pós de YBCO. Foram estudadas diferentes formulações por forma a conseguir obter a pasta optimizada para extrudir. Foi testada a impressão de uma pré-mistura de pós Y2O3, BaCO3 e CuO, contendo um agente ligante, sendo depois formado o YBCO num processo de sinterização, o qual permite a remoção do agente ligante: Outro processo estudado consistiu na eliminação da etapa de sinterização pós-impressão, utilizando para tal o YBCO já formado.
Tuning the 1H NMR Paramagnetic Relaxation Enhancement and Local Order of [Aliquat]+-Based Systems Mixed with DMSO
Publication . Cordeiro, Rui; Beira, Maria J.; Cruz, Carlos; Figueirinhas, João L; Corvo, Marta C; Almeida, Pedro L; Rosatella, Andreia A.; Afonso, Carlos A. M.; Daniel, Carla I.; Sebastião, Pedro J.; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing Institute
Understanding the behavior of a chemical compound at a molecular level is fundamental, not only to explain its macroscopic properties, but also to enable the control and optimization of these properties. The present work aims to characterize a set of systems based on the ionic liquids [Aliquat][Cl] and [Aliquat][FeCl4] and on mixtures of these with different concentrations of DMSO by means of 1H NMR relaxometry, diffusometry and X-ray diffractometry. Without DMSO, the compounds reveal locally ordered domains, which are large enough to induce order fluctuation as a significant relaxation pathway, and present paramagnetic relaxation enhancement for the [Aliquat][Cl] and [Aliquat][FeCl4] mixture. The addition of DMSO provides a way of tuning both the local order of these systems and the relaxation enhancement produced by the tetrachloroferrate anion. Very small DMSO volume concentrations (at least up to 1%) lead to enhanced paramagnetic relaxation without compromising the locally ordered domains. Larger DMSO concentrations gradually destroy these domains and reduce the effect of paramagnetic relaxation, while solvating the ions present in the mixtures. The paramagnetic relaxation was explained as a correlated combination of inner and outer-sphere mechanisms, in line with the size and structure differences between cation and anion. This study presents a robust method of characterizing paramagnetic ionic systems and obtaining a consistent analysis for a large set of samples having different co-solvent concentrations.
Recent advances in magnetic electrospun nanofibers for cancer theranostics application
Publication . Soares, Paula I. P.; Borges, João Paulo; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; Elsevier
Cancer theranostics is a recent concept that aims to combine in the same device diagnostic and therapeutic features. Magnetic nanoparticles (mNPs) are commonly used as a critical part of these systems due to their ability to respond to an external magnetic field. Consequently, mNPs can generate heat when an alternating magnetic field is applied and enhance image contrast in magnetic resonance. However, direct administration of mNPs intravenously or directly in the tumor can lead to undesired side effects because of mNP elimination by macrophages or leakage to healthy tissues. Therefore, mNPs can be retained in a polymeric nanofibrous mesh, thus preventing misplacing or loss of mNPs. Furthermore, these magnetic nanofibers can be directly implanted in the tumor site, thus ensuring high mNPs loading and higher magnetic response. In addition, polymeric nanofibers produced by electrospinning are frequently used to maintain a sustained drug release in the tumor site. Therefore, a magnetic polymeric nanofiber produced by electrospinning is an ideal nanosystem for cancer theranostics application. This review summarizes the most recent developments of magnetic nanofibers produced by electrospinning for cancer theranostics applications.
Nanostructured LiFe5O8 by a biogenic method for applications from electronics to medicine
Publication . Teixeira, Silvia Soreto; Graça, Manuel P. F.; Lucas, José; Valente, Manuel Almeida; Soares, Paula I. P.; Lança, Maria Carmo; Vieira, Tânia; Silva, Jorge Carvalho; Borges, João Paulo; Jinga, Luiza Izabela; Socol, Gabriel; Salgueiro, Cristiane Mello; Nunes, José Ferreira; Costa, Luís Cadillon; CENIMAT-i3N - Centro de Investigação de Materiais (Lab. Associado I3N); DCM - Departamento de Ciência dos Materiais; MDPI AG
The physical properties of the cubic and ferrimagnetic spinel ferrite LiFe5O8 has made it an attractive material for electronic and medical applications. In this work, LiFe5O8 nanosized crystallites were synthesized by a novel and eco-friendly sol-gel process, by using powder coconut water as a mediated reaction medium. The dried powders were heat-treated (HT) at temperatures between 400 and 1000◦C, and their structure, morphology, electrical and magnetic characteristics, cytotoxicity, and magnetic hyperthermia assays were performed. The heat treatment of the LiFe5O8 powder tunes the crystallite sizes between 50 nm and 200 nm. When increasing the temperature of the HT, secondary phases start to form. The dielectric analysis revealed, at 300 K and 10 kHz, an increase of ε′ (≈10 up to ≈14) with a tan δ almost constant (≈0.3) with the increase of the HT temperature. The cytotoxicity results reveal, for concentrations below 2.5 mg/mL, that all samples have a non-cytotoxicity property. The sample heat-treated at 1000◦C, which revealed hysteresis and magnetic saturation of 73 emu g−1 at 300 K, showed a heating profile adequate for magnetic hyperthermia applications, showing the potential for biomedical applications.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UID/CTM/50025/2019