11 documents found, page 1 of 2
New WC-Cu composites for the divertor in fusion reactors
Dias, Marta; Pinhão, N.; Faustino, R.; Martins, Ricardo; Ramos, A. S.; Vieira, M. T.; Correia, J.B.; Camacho, E.; Fernandes, F. M. Braz; Nunes, B.ABSTRACT: The requirements for the divertor components of future fusion reactors are challenging and therefore a stimulus for the development of new materials. In this paper, WC-Cu composites are studied for use as thermal barrier between the plasma facing tungsten tiles and the copper-based heat sink of the divertor. Composite materials with 50% vol. WC were prepared by hot pressing and characterized in terms ...
Mechanical activation of pre-alloyed NiTi2 and elemental Ni for the synthesis o...
Zhao, X.; Neves, Filipe; Correia, J.B.; Liu, K.; Fernandes, F. M. Braz; Koledov, V.; von Gratowski, S.; Xu, S.; Huang, J.ABSTRACT: This work reports on an efficient powder metallurgy method for the synthesis of NiTi alloys, involving mechanical activation of pre-alloyed NiTi2 and elemental Ni powders (NiTi2-Ni) followed by a press-and-sinter step. The idea is to take advantage of the brittle nature of NiTi2 to promote a better efficiency of the mechanical activation process. The conventional mechanical activation route using elem...
In situ experiments with synchrotron high-energy x-rays of Ni-Ti alloys produce...
Neves, Filipe; Correia, J.B.; Martins, Isabel M.; Fernandes, F. M. Braz; Mahesh, K. K.; Stark, A.; Schell, N.The structural evolution that takes place during the homogenization heat treatments of powder metallurgical Ni-Ti- alloys was studied by in situ synchrotron diffraction. It is proposed to get a deeper understanding of this phenomenon by using different types of thermal/mechanical cycles.
Role of ogyxen and nitrogen in mechanical alloying mechanism of Ni-Ti powder mi...
Neves, Filipe; Fernandes, F. M. Braz; Martins, Isabel M.; Correia, J.B.In this study, the critical milling behaviour of Ni-Ti powder mixtures was evaluated in relation to the effect of atmospheric gases, more specifically to oxygen and nitrogen. Within the experimental conditions used, it is shown that both gases play an important role in the alloying process and that not only oxygen gas reacts with the mechanically alloyed powders but also nitrogen. The most effective mixing occu...
Characterization of smart MARFOS NiTi shape memory alloys
Neves, Filipe; Fernandes, F. M. Braz; Martins, J.; Correia, J.B.; Oliveira, M.; Gaffet, E.; Wang, T. Y.; Lattemann, M.; Suffner, J.; Hahn, H.In the present study, structural characterization of NiTi smart shape memory al-loys (SMAs), produced by an alternative powder metallurgy approach named mechanically ac-tivated reactive forging (MARFOS), was carried out by means of transmission electron micros-copy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was observed that MARFOS materials had a multiphase nanocrystalline struct...
Nonconventional production technologies for NiTi shape memory alloys
Neves, Filipe; Fernandes, F. M. Braz; Martins, Isabel M.; Correia, J.B.; Oliveira, M.; Gaffet, E.; Wang, T. Y.; Lattemann, M.; Suffner, J.; Hahn, H.The development of new production technologies for NiTi Shape Memory Alloys (SMAs) is always challenging. Recently, we introduced two powder metallurgical (PM) processing routes involving mechanical activation of elemental powder mixtures and densification through extrusion or forging. Those processes were named Mechanically Activated Reactive Extrusion Synthesis (MARES) and Mechanically Activated Reactive FOrg...
Microstructure characterization of aluminium syntactic functionally graded comp...
Ferreira, S. C.; Velhinho, A.; Rocha, L. A.; Fernandes, F. M. BrazSyntactic functionally graded metal matrix composites (SFGMMC) are a class of metallic foams in which closed porosity results from the presence of hollow ceramic microspheres (microballoons), whose spatial distribution varies continuously between the inner and the outer section of the part, thus resulting in a continuous variation in properties. In this work, aluminium-based SFGMMC rings were fabricated by radi...
Functionalization of carbon nanofibers by a diels-alder addition reaction
Fernandes, F. M. Braz; Araújo, R. F.; Proença, M. Fernanda R. P.; Silva, Carlos J. R.; Paiva, M. C.This paper reports functionalization of CNF via a Diels-Alder addition reaction and the characterization of the obtained materials. The functionalization was assessed by a calorimetric technique (DSC) and the morphology of CNF modified materials was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The functionalization was observed to be dependent on the preparativ...
The 1,3-dipolar cycloaddition reaction in the functionalization of carbon nanof...
Araújo, R. F.; Fernandes, F. M. Braz; Proença, M. Fernanda R. P.; Silva, Carlos J. R.; Paiva, M. C.Carbon nanofibers were functionalized using a reaction scheme described in the literature for 1,3- dipolar cycloaddition of azomethine ylides generated in situ by the condensation of an -amino acid and an aldehyde. The reagents used were Z-Gly-OH and paraformaldehyde. Their reaction with carbon nanofibers was studied as a solid mixture by controlled heating in the DSC. An oxazolidinone intermediate was formed a...
Application of X-ray microtomography to the microstructural characterization of...
Velhinho, A.; Fernandes, F. M. Braz; Ferreira, S. C.; Rocha, L. A.; Vignoles, G.; Cloetens, P.This paper provides a brief overview of the possibilities offered by X-ray computed microtomography, and particularly synchrotron radiation X-ray microtomography, regarding metal matrix composite characterization, emphasis being placed in the case of Al-based functionally graded materials. Examples are provided concerning the characterization of the reinforcement population, interfacial properties, in-situ tran...