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- From Machining Chips to Raw Material for Powder Metallurgy—A ReviewPublication . Batista, Catarina; Fernandes, Adriana André Martins das Neves de Pinho; Vieira, Maria Teresa Freire; Emadinia, OmidChips are obtained by subtractive processes such as machining workpieces and until recently considered as waste. However, in recent years they are shown to have great potential as sustainable raw materials for powder technologies. Powder production from metal chips, through the application of solid-state processes, seems to be an alternative to conventional atomization from liquid cooled with different fluids. However, chip material and processing have an essential role in the characteristics of powder particles, such as particle size, shape, size distribution and structure (4S’s), which are essential parameters that must be considered having in mind the powder process and the metallurgy applications. Moreover, different approaches refereed in the application of this new “powder process” are highlighted. The goal is to show how the actual research has been transforming subtractive processes from a contributor of wastes to clean technologies.
- Additive manufactured stoneware fired in microwave furnacePublication . Santos, Tiago; Ramani, Melinda; Devesa, Susana; Batista, Catarina; Franco, Margarida; Duarte, Isabel; Costa, Luís; Ferreira, Nelson; Alves, Nuno; Pascoal-Faria, PaulaAdditive manufacturing (AM) techniques have revolutionized the concept of building parts not only in laboratory contexts but also in industry environments and can be applied to distinct fields such as the health, automotive and aeronautics sectors [...]
- 3D-printed teeth in endodontics: Why, how, problems and future: A narrative reviewPublication . Reis, Tiago; Barbosa, Cláudia; Franco, Margarida; Baptista, Catarina; Alves, Nuno; Castelo-Baz, Pablo; Martín-Cruces, José; Martin-Biedma, BenjaminThree-dimensional printing offers possibilities for the development of new models in endodontics. Numerous studies have used 3D-printed teeth; however, protocols for the standardization of studies still need to be developed. Another problem with 3D-printed teeth is the different areas of literature requested to understand the processes. This review aims to gather evidence about 3Dprinted teeth on the following aspects: (1) why they are advantageous; (2) how they are manufactured; (3) problems they present; and (4) future research topics. Natural teeth are still the standard practice in ex vivo studies and pre-clinical courses, but they have several drawbacks. Printed teeth may overcome all limitations of natural teeth. Printing technology relies on 3D data and post-processing tools to form a 3D model, ultimately generating a prototype using 3D printers. The major concerns with 3D-printed teeth are the resin hardness and printing accuracy of the canal anatomy. Guidance is presented for future studies to solve the problems of 3D-printed teeth and develop well-established protocols, for the standardization of methods to be achieved. In the future, 3D-printed teeth have the possibility to become the gold standard in ex vivo studies and endodontic training.
- High-speed machining tool-steel chips as an outstanding raw material for indirect additive manufacturing?Publication . Santos, R. F.; Farinha, A. R.; Rocha, R.; Batista, C.; Rodrigues, G. Costa; Vieira, M. T.Sustainable recycling approaches are emerging topics for environmental safety of manufacturing technologies. Chips generated in high–speed machining (HSM) of as-quenched steels have a potential re-use for more sustainable and cost-efficient manufacturing routes, such as powder production from chip milling for additive manufacturing (AM). The objective of this study was to characterise tool-steel chips generated by HSM of an AISI-SAE H13 as-quenched workpiece and evaluate their potential use for powder production, as an alternative process to atomisation. Microhardness tests reveal that this type of waste has a suitable hardness for milling, which could be attributed to its microstructure. Chips were also analysed by X-ray diffraction, scanning and transmission electron microscopies, and transmission electron backscattering diffraction (t-EBSD) mapping. The microstructure of the areas adjacent to the adiabatic shear band (ASB), where intense material flow takes place, consists of thin martensite laths with high dislocation density and low angle grain boundaries (LAGB) or sub-grain regions. ASB consists of ultrafine and nanocrystalline grains. The results provide new insight on the grain-refining mechanism assisted by progressive martensite lath subdivision into small and near-equiaxed grains, as a direct result of intense strain accumulation and recrystallisation, endorsing HSM tool-steel chips as superior (nanocrystalline) and low-cost raw material for powder production.
- Microstructure of Thermoplastic Composites Reinforced with Wool and WoodPublication . Batista, Catarina; Martins, Gabriela; Santos, Cyril; Mateus, Artur; Antunes, FilipeIn the last decades the studies on thermoplastic composites reinforced with natural fibres have been mostly focused on vegetable lignocellulosic or cellulosic fibres. These materials provide eco-sustainable solutions for a large range of applications and have been actually adopted by multiple industries. The interest on fibres of animal origin is more recent and research on composites reinforced with these fibres predominantly composed of keratin, such as wool, feathers or silk, is increasing in virtue of some advantageous properties that may overcome some of the intrinsic limitations from vegetable fibres. The combined use of vegetable and animal fibres in composites appropriate for melt blending processing is at early stages of research. After chemical treatments, the fibres of animal origin have been mostly applied as binders between vegetable fibres and polymers, but not as main constituents of these composites. The use of both types of fibres simultaneously in composites of thermoplastic matrices is the subject of the present study where the fibres of animal origin (wool) are sourced from different kinds of residues from a textile industry and the fibres of vegetable origin (wood) are the residues from carpentry activities. The chemical composition, the macro and microstructure of the fibres is analyzed, as well as that of the composites that combine non-biodegradable and biodegradable polymers with diverse ratios of the fibres in different conditions (wool as cards, yarns and felt cloths; wood as sawdust). The addition of coupling agents to enhance the compatibility between wool, wood and different polymers is also analysed.