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- Design and production of sintered β-tricalcium phosphate 3D scaffolds for bone tissue regenerationPublication . Santos, Carlos Filipe Lopes; Silva, Abílio P.; Lopes, Luís; Pires, Inês; Correia, Ilídio Joaquim SobreiraThe characteristics of sintered β-tricalcium phosphate (β-TCP) scaffolds produced by 3D printing were studied by means of X-ray diffraction, Scanning Electron Microscopy, Fourier transform infrared spectroscopy, uniaxial compression tests and cytotoxicity tests, using human osteoblast cells. The results reported include details of the β-TCP scaffolds' porosity, density, phase stability, mechanical behavior and cytotoxic profile. Collectively, these properties are fundamental for the future application of these scaffolds as bone substitutes for individualized therapy.
- Optimização da Técnica de Preparação de Amostras de Betões Refractários Auto-Escoantes de Alumina Sem Cimento Para Observação MicroscópicaPublication . Silva, Abílio P.; Gomes, Ana; Segadães, Ana Maria; Devezas, TessalenoA preparação de amostras para a observação de superfícies em microscopia requer um procedimento de corte, rectificação e polimento rigoroso que obedeça a requisitos sistemáticos de avaliação da qualidade superficial. Neste trabalho, um novo material constituído por 100% de alumina, mas de ingredientes (matriz e agregado) com características distintas obrigou, à implementação de uma nova receita de polimento e de realce dos contrastes entre os elementos estruturais presentes. Assim, apresenta-se um procedimento optimizado para a preparação das amostras de betões refractários auto-escoantes de alumina sem cimento para análise da microestrutura em microscópio metalográfico em complementaridade com o microscópio electrónico de varrimento.
- Designing particle sizing and packing for flowability and sintered mechanical strengthPublication . Silva, Abílio P.; Pinto, Deesy G.; Segadães, A M; Devezas, TessalenoIn this work, alumina powders in five different commercially available size ranges were used to prepare various refractory castable mixtures, defined using the statistical design of mixture experiments (STATISTICA, StatSoft Inc.) and the EMMA 3.3 software (Elkem Materials). Those mixtures were characterized for packing density, Andreasen particle size distribution modulus (q), flowability and after sintering properties, in order to investigate the relationships between these variables. The optimization of matrix and aggregate sizes and matrix-aggregate proportion, subjected to different property requirements, brought to light the relationships between q, specific surface area (SSA) and maximum paste thickness (MPT). Those relationships were investigated for three fundamental processing steps, namely, dry powders, fresh paste and consolidated dried and sintered bodies. The optimized all-alumina castable was found to require 47.5wt.% of a fine size matrix with high flowability, which provides the necessary flow bed for 52.5wt.% of coarse aggregates, resulting in a gap-sized particle size distribution, and presented a fresh paste flowability index above 130% with minimum added water (28mg/m2) and sintered modulus of rupture above 50MPa.
- Potential for reuse of tungsten mining waste-rock in technical-artistic value added productsPublication . Gomes, João Castro; Silva, Abílio P.; Peralbo Cano, Rafael; Durán Suárez, Jorge Alberto; Albuquerque, AntónioMining and quarrying activities in Europe generate approximately 55% of total industrial wastes, according to a recent Eurostat report. Most of these wastes are directly dumped on land or deposited in landfill sites. The first solution may lead to negative environmental impacts on land (removal of vegetation, deforestation, land slope changes and increased risk of erosion), water (pollutant transport through surface runoff, soil infiltration and contamination of water resources), may lead to the contamination of agricultural goods and may impose risks on human health. In Portugal, about 20% of industrial waste produced originates from mines and quarries, particularly from Panasqueira mining, one of the largest tungsten mines in the world. Currently, Panasqueira mining generates almost 100 tonnes of waste-rock, per day. Such waste-rock have accumulated over a number of years into very large heaps and it is desirable to seek new economic solutions that can contribute towards their reuse. In this context, this work discusses the potential for reuse of waste-rock piles of Panasqueira tungsten mine, which may be a case statement to be followed. The proposed solution described in this paper consists in developing innovative polymer-based composite materials, obtained from non-contaminated waste-rock tailings. Such materials must have suitable properties for technical-artistic value added applications, such as conservation, restoration and/or rehabilitation of historic monuments, sculptures, decorative and architectural intervention, or simply as materials for building revetments.
- Energy scenarios: Toward a new energy paradigmPublication . Devezas, Tessaleno; LePoire, David; Matias, João; Silva, AbílioPrimary energy sources exhibited regular long-term logistic substitution trends from the mid-19th century through the third quarter of the 20th century. This analysis, based on an extension of the Fisher–Pry substitution model, accounted for the observed historical shifts of primary energy use from sources of wood, coal, oil, natural gas, and nuclear. In the mid1980s the substitution dynamics was replaced by a relatively constant contribution from oil, natural gas, coal, nuclear power, and hydropower. However, a major factor in energy use dynamics in this recent period was substitution of conservation and efficiency for actual fuel use. The energy efficiency is measured as the ratio of economic activity to the rate of energy use (energy intensity). To incorporate these data into the logistic analysis, a method for estimating the fraction of energy saved by the increased efficiency was used. With this interpretation, energy efficiency fits within the substitution model. Furthermore, to identify indications of future energy scenarios, as well as to test the logistic substitution analysis, another statistical approach using ternary diagrams was developed. The consistent results from both logistic substitution and statistical analysis are compared with recent energy projections, trends in decarbonization, Kondratieff waves, and other efficiency measures. While the specific future mix of renewables and nuclear energy sources is uncertain, the more general logistic dynamics pattern of the energy system seems to be continuing as it has for about 150 years now.
- Reciclagem de agregados das minas da Panasqueira como revestimento refratário da fundição de metaisPublication . Herrera, J. Montoya; Suarez, J.A. Durán; Silva, Abílio P.; Cano, R. Peralbo; Gomes, João CastroNas minas da Panasqueira (Covilhã, Portugal) acumulam-se montes de resíduos (agregados) provenientes da extração de tungsténio sem qualquer aplicação. Este trabalho pretende contribuir para implementar um novo uso para estes resíduos integrando-os como revestimento refratário no processo de moldação a verde da fundição de metais não ferrosos. Os resultados mostram o potencial do uso destes resíduos da fundição de metais não ferrosos.
- Geotechnical Characterization of Water Treatment Sludge for Liner Material Production and Soft Soil ReinforcementPublication . Marchiori, Leonardo; Studart, André; Albuquerque, Antonio; Cavaleiro, Victor; Silva, AbilioA water treatment sludge (WTS) was characterized in order to evaluate if its properties would be suitable for use as liner of earthworks or for strengthening a clay soil. A WTS and a clayey soil was characterized in terms of granulometry, cumulative volumes, specific surface, density, plastic limit, liquid limit, water content, hydraulic conductivity, and characteristics of compaction (optimal water content and dry density). This study aimed to exhibit and evaluate these investigated parameters of WTS, soft soil and mixed proportions between the materials for liners’ material production while evaluating soft soils’ reinforcement feasibility. The results have shown WTS’s contribution with its fine granulometry and compaction characteristics, indicating filling properties and possible feasibility as soft soils additions for liners’ material production while being applicable for soils‘ reinforcements, corroborating with existing literature on the subject. Thus, the currently developed investigation has exposed WTS as a potential addition for these applications while also attending society’s new demands towards a more sustainable future.
- Dureza e módulo de elasticidade em cerâmicas multifásicasPublication . Silva, AbilioO problema proposto consiste em elucidar se a contribuição de cada fase para propriedades como a dureza e o módulo de elasticidade em compósitos cerâmicos multifásicos CaZrO3-MgO-ZrO2 podem ser estimados com base em modelos simples como a “regra das misturas” ou se existem outros fatores para levar em consideração tais como o tamanho, a forma e os limites de grão. Assim, as propriedades de dois materiais previamente desenvolvidos [10-12], com as mesmas fases principais (CaZrO3, MgO e c-ZrO2), mas em diferentes frações volumétricas e tamanho de grão foram analisadas de modo a cumprir as seguintes tarefas: i) Determinar a dureza de cada material usando macro indentação; ii) Determinar a dureza e o módulo de elasticidade de cada uma das fases principais por nano indentação; iii) Verificar a independência das fases constituintes face aos dois materiais e comparar os resultados obtidos com os descritos na literatura; iv) Determinar a contribuição esperada de cada uma das fases para as propriedades da cerâmica multifásica (compósito).
- Characterization of the Mechanical and Biological Properties of a New Alumina ScaffoldPublication . Batista, Patrícia Sofia Pinhanços; Rodrigues, Miguel; Silva, Daniela; Morgado, Patrícia I.; Henriques, J.; Almeida, Maria; Silva, Abílio P.; Correia, Ilídio Joaquim SobreiraPurpose: In this work, an alumina scaffold was produced through a new method to be used in a near future as a bone substitute. Methods: In vitro and in vivo studies were performed in order to characterize the mechanical and biological properties of the scaffold. Results: the results obtained showed that this scaffold has high mechanical resistance and a porous surface that allows human osteoblast cells to adhere and proliferate. the in vivo studies revealed no systemic reaction. Conclusions: the alumina scaffold produced herein has the mechanical and biological properties that are compatible with its application in bone therapy.
- Bioactive polymeric–ceramic hybrid 3D scaffold for application in bone tissue regenerationPublication . Torres, Ana; Gaspar, V. M.; Serra, Inês Raquel Tavares; Carlos, Gabriela Soares Diogo; Fradique, Ricardo Gil; Silva, Abílio P.; Correia, I.J.The regeneration of large bone defects remains a challenging scenario from a therapeutic point of view. In fact, the currently available bone substitutes are often limited by poor tissue integration and severe host inflammatory responses, which eventually lead to surgical removal. In an attempt to address these issues, herein we evaluated the importance of alginate incorporation in the production of improved and tunable β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) three-dimensional (3D) porous scaffolds to be used as temporary templates for bone regeneration. Different bioceramic combinations were tested in order to investigate optimal scaffold architectures. Additionally, 3D β-TCP/HA vacuum-coated with alginate, presented improved compressive strength, fracture toughness and Young's modulus, to values similar to those of native bone. The hybrid 3D polymeric–bioceramic scaffolds also supported osteoblast adhesion, maturation and proliferation, as demonstrated by fluorescence microscopy. To the best of our knowledge this is the first time that a 3D scaffold produced with this combination of biomaterials is described. Altogether, our results emphasize that this hybrid scaffold presents promising characteristics for its future application in bone regeneration.