F. Neves

F. Neves
Laboratório Nacional de Energia e Geologia | LNEG · Unidade de Energia Solar, Eólica e dos Oceanos

Doctor of Engineering

About

54
Publications
4,436
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164
Citations
Citations since 2017
15 Research Items
76 Citations
20172018201920202021202220230510152025
20172018201920202021202220230510152025
20172018201920202021202220230510152025
20172018201920202021202220230510152025
Additional affiliations
June 2019 - present
Laboratório Nacional de Energia e Geologia
Position
  • Researcher
January 2012 - May 2019
Laboratório Nacional de Energia e Geologia, I.P. - LNEG
Position
  • PostDoc Position
January 2008 - December 2011
Universidade NOVA de Lisboa
Position
  • PostDoc Position

Publications

Publications (54)
Article
Full-text available
The inexorable increase of energy demand and the efficiency bottleneck of monocrystalline silicon solar cell technology is promoting the research and development of alternative photovoltaic materials. Copper-arsenic-sulfide (CAS) compounds are still rather unexplored in the literature, yet they have been regarded as promising candidates for use as...
Poster
Full-text available
Comprehensive study of the structural and optoelectronic properties of Cu-As-S thin-films deposited via radio-frequency magnetron co-sputtering, using a commercial Cu target together with a target with material obtained from local resources, specifically from mines in the Portuguese sector of the Iberian Pyrite Belt.
Article
Full-text available
The present study shows a comparison between two sintering processes, microwave and conventional sintering, for the manufacture of NiTi porous specimens starting from powder mixtures of nickel and titanium hydrogenation–dehydrogenation (HDH) milled by mechanical alloying for a short time (25 min). The samples were sintered at 850 °C for 15 min and...
Article
Full-text available
One of the areas of research on materials for thin-film solar cells focuses on replacing In and Ga with more earth-abundant elements. In that respect, chalcostibite (CuSbS2) is being considered as a promising environmentally friendly and cost-effective photovoltaic absorber material. In the present work, single CuSbS2 phase was synthesized directly...
Preprint
Full-text available
One of the areas of research on materials for thin-film solar cells focuses on replacing In and Ga with more earth-abundant elements. In that respect, chalcostibite (CuSbS2) is being considered as a promising environmentally friendly and cost-effective photovoltaic absorber material. In the present work, single CuSbS2 phase have been synthesized di...
Article
Considering that the synthesis of tetrahedrite-based materials usually uses high purity elements, the evaluation of the direct application of ore samples as raw materials for their synthesis is a pertinent issue. In the present study, multiphase synthetic tetrahedrite samples were mixed with tetrahedrite-tennantite ore samples (in weight ratios of...
Article
There is an urgent need to develop an alternative high-efficiency cooling technology that is affordable and environmentally friendly. Elastocaloric effect has attracted particular attention due to large available latent heat and large adiabatic temperature changes. The primary objective of this study is to control the deformation of NiTi solid-stat...
Conference Paper
Full-text available
This work describes the main lines of investigation that are underway within LocalEnergy project (http://localenergy.lneg.pt). LocalEnergy is a multidisciplinary Research, Development and Innovation project, involving activities in the field of materials science, geology and renewable energies. These activities are oriented towards the industry and...
Conference Paper
Full-text available
ABSTRACT The development and implementation of energy efficient technologies with low global warming potential requires a continuous innovation in the field of materials for energy. This strategy includes research on the processing of thermoelectric materials based on tetrahedrite. In the present work, it is evaluated the feasibility of the direct...
Presentation
Full-text available
Extended abstract and presentation at the Virtual Conference on Thermoelectrics, VCT 2020, International Thermoelectrics Society (ITS), July 21-23, 2020
Conference Paper
The Barrigão re-mobilised copper vein deposit is revisited in the light of tetrahedrite-tennantite importance for EU Critical Raw Materials (CRM) knowledge as well as material research for development of thermoelectric (TE) and solar energy harvesting technologies. The transition to decarbonised economies (+ e-mobility) and full circular economy im...
Conference Paper
Full-text available
In this study, we propose the direct synthesis of nanocrystalline and single-phase Cu12-x-yFexZnySb4S13-z tetrahedrites, with 0 ≤ x, y ≤ 1 and 0 ≤ z ≤ 0.3, using an powder metallurgical route consisting in a short duration (2 h) high energy milling step followed by a subsequent densification step through hot pressing. Elemental powders of Cu, Fe, Z...
Article
Full-text available
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. T...
Article
The copper zinc tin sulfide (CZTS) compound is a promising candidate as an alternative absorber material for thin-film solar cells. In this study, we investigate the direct formation of Cu1.92ZnSnx (Sb1−x )S4 compounds [CZT(A)S], with x = 1, 0.85, 0.70, and 0.50, via a mechanochemical synthesis (MCS) approach, starting from powders of the correspon...
Patent
A presente invenção descreve o processo de fabrico da camada absorsora, um dos constituintes de uma célula fotovoltaica de filmes finos, formada pelo composto Cu2(Sn1-xMx)(SySe1-y)3 em que M = Ge ou Si, x e y entre 0 e 1. Este processo é caracterizado por não utilizar tecnologias com vácuo, ser de baixo custo e ser baseado na tecnologia dos pós. De...
Article
Cu2SnS3 (CTS) and Cu2Sn0.83Ge0.17S3 (CTGS) compounds were successfully prepared by a powder technology using a combination of mechanical alloying (MA) and spark plasma sintering (SPS). Structural, compositional and optical properties were studied. A true alloy with composition similar to the starting constituents was formed after 2 h of MA at 400 r...
Article
Earth-abundant and nontoxic absorber materials have been extensively studied for thin-film solar cells. One of the most viable candidate materials for solar absorber applications is Cu2SnS3 (CTS). The feasibility of producing fully dense CTS materials by combining mechanical alloying (MA) and spark plasma sintering (SPS) is reported for the first t...
Conference Paper
Full-text available
The Cu2ZnSnS4 (CZTS) solar cells have numerous advantages that could lead to its massive use as a low cost PV solar cell device: (a) it has a direct bandgap and an absorption coefficient >104 cm−1; (b) its band gap has been predicted to be 1.5 eV; (c) its crystallographic structure can accept some shifts from the stoichiometric composition; (d) hig...
Article
Full-text available
The design and synthesis of high-efficiency materials to convert solar to electrical energy is an increasingly important research field. Within the photovoltaic technologies, crystalline Si have an 80% share while the remaining 20% are mostly thin film solar cells based on Cu(In,Ga)(S,Se)2 (CIGSSe) and CdTe. However, the cost, the abundance and the...
Article
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 a...
Conference Paper
Full-text available
This work aims to prove the feasibility of in situ X-ray diffraction studies during thermomechanical cycles and to demonstrate the interest of the combined dilatometry (under compression) and diffraction data for the detailed analysis of the phase transformations in Ni-Ti shape memory alloys.
Article
Full-text available
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 phenomenonby using different types of thermal/mechanical cycles.This work also intends to prove the feasibility of in situ X-ray...
Article
In this study, a set of Ti–50 at.% Ni elemental powder mixtures were processed through mechanical alloying (MA). The objectives were to induce during MA the formation of a lamellar microstructure and to apply a design of experiments, based on the Taguchi method, to optimize theMAparameters. Enthalpy measurements associated to the high temperature r...
Article
In the present study, equiatomic powder blends of Ni and Ti were mechanically activated for a short period of time in a planetary ball mill using different levels of energy input. The characterization of the mechanically activated materials was achieved by scanning electron microscopy, X-ray diffraction, differential thermal analysis and chemical a...
Article
Full-text available
Depending on the energy level used during mechanical alloying, the constitution of the resulting products can vary extensively. With high energy input, full transformation to the equilibrium phase, FeTi, is achieved. In contrast, for low levels of energy input, the process is akin to mixing without any phase transformation even for extended milling...
Article
Full-text available
Two promising powder metallurgy (PM) processes were used for the fabrication of NiTi shape memory alloys (SMA): Mechanically Activated Reactive FOrging Synthesis (MARFOS) and Mechanically Activated Reactive Extrusion Synthesis (MARES). In these two processes, equimolar powder mixtures of elemental Ni and Ti are first mechanically activated and then...
Article
. Two promising powder metallurgy (PM) processes were used for the fabrication of NiTi shape memory alloys (SMA): Mechanically Activated Reactive FOrging Synthesis (MARFOS) and Mechanically Activated Reactive Extrusion Synthesis (MARES). In these two processes, equimolar powder mixtures of elemental Ni and Ti are first mechanically activated and th...
Article
Full-text available
The phase transformation behaviour of bulk nanostructured NiTi shape memory alloys, produced by an innovative approach called MARES (mechanically activated reactive extrusion synthesis), was investigated using in situ x-ray diffraction and differential scanning calorimetry measurements. For the experimental conditions used, a suitable adjustment of...
Article
Full-text available
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 Extr...
Conference Paper
Full-text available
In the present study, structural characterization of NiTi smart shape memory alloys (SMAs), produced by an alternative powder metallurgy approach named mechanically ac-tivated reactive forging (MARFOS), was carried out by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was observed...
Article
Full-text available
The phase transformation behaviour of bulk nanostructured NiTi shape memory alloys, produced by an innovative approach called MARES (mechanically activated reactive extrusion synthesis), was investigated using in situ x-ray diffraction and differential scanning calorimetry measurements. For the experimental conditions used, a suitable adjustment of...
Article
Full-text available
The use of a high-brightness field-emission gun (FEG) in scanning electron microscopy (SEM) is a powerful technique to examine microstructures at very high spatial resolution down to nanometer level and has significantly enhanced our ability to solve challenging materials problems, allowing studies of nanoprecipitates.
Article
The production of NiTi alloys through mechanically activated reactive forging synthesis (MARFOS) of elemental powder mixtures with equiatomic composition has been investigated for the first time. The short duration of mechanical activation (4 h) successfully produced powder mixtures capable of being hot deformed at relatively low temperatures. As a...
Chapter
Full-text available
This study reports the use of X-ray diffraction quantitative phase analyses in NiTi alloys produced by MARES (Mechanically Activated Reactive Extrusion Synthesis). These analyses were performed with the PowderCell 2.4 software. The mechanically activated powders heated in a DTA furnace at 500 C had as main phases Ni (27 wt %) and Ti (30 wt %) and t...
Article
Copper nitride films prepared by sputtering have applications such as optical data storage material, insulation barriers in micro electronic devices and coatings for mechanical applications. The present study examines nanocomposites prepared by mechanical alloying of copper with copper nitride under nitrogen atmosphere, at room temperature, in orde...
Article
This study reports the use of X-ray diffraction quantitative phase analyses in NiTi alloys produced by MARES (Mechanically Activated Reactive Extrusion Synthesis). These analyses were performed with the PowderCell 2.4 software. The mechanically activated powders heated in a DTA furnace at 500 ºC had as main phases Ni (27 wt %) and Ti (30 wt %) and...
Conference Paper
The NiTi intermetallic is well known for its shape memory properties. However, NiTi alloys also exhibits superior mechanical properties, in particularly, they possesses excellent wear resistance. This property depends strongly on the chemical composition, processing history and impurity level. The present work reports our experimental studies of Vi...
Article
Mechanically activated reactive extrusion synthesis (MARES), as an innovation in powder sintering, was used for the first time to produce NiTi alloys. Equimolar powder mixtures of elemental Ni and Ti were firstly mechanically activated for 4 h and then extruded at relatively low temperatures (between 300 and 600 °C). No intermetallic phase formatio...
Article
Full-text available
The use of a high-brightness field-emission gun (FEG) in scanning electron microscopy (SEM) is a powerful technique to examine microstructures at very high spatial resolution down to nanometer level and has significantly enhanced our ability to solve challenging materials problems, allowing studies of nanoprecipitates.
Article
Full-text available
This study reports the use of X-ray diffraction quantitative phase analyses in NiTi alloys produced by MARES (Mechanically Activated Reactive Extrusion Synthesis). These analyses were performed with the PowderCell 2.4 software. The mechanically activated powders heated in a DTA furnace at 500 ºC had as main phases Ni (27 wt %) and Ti (30 wt %) and...
Article
In the present study, an alternative approach to the synthesis of TiNi alloys through powder metallurgy was successfully conducted by mechanically activated reactive extrusion synthesis (MARES) using elemental powders. The production of dense bodies was essentially dependent on the amount of intermetallic phases formed prior to reactive extrusion a...
Article
Full-text available
Thin layers of silver and titanium were deposited onto commercial Ti–48Al particles by magnetron sputtering prior to their consolidation by hot isostatic pressing and subsequent heat treatment. Based on picnometry and electron probe microanalysis results, average values of 1.5 and 2.5 at.%, respectively, were obtained for the silver and titanium co...
Article
(Ti–48Al)-based intermetallics were synthesized by a combination of mechanical alloying, sputtering and hot isostatic pressure techniques. Blended elemental powders of TiH2 and Al with nominal composition TiH2–48Al were mechanically alloyed for different periods of time. The powders were then coated with Ti and Ag and subsequently hot isostatically...
Conference Paper
Full-text available
This study reports the use of X-ray diffraction quantitative phase analyses in NiTi alloys produced by MARES (Mechanically Activated Reactive Extrusion Synthesis). These analyses were performed with the PowderCell 2.4 software. The mechanically activated powders heated in a DTA furnace at 500 ºC had as main phases Ni (27 wt %) and Ti (30 wt %) and...
Article
Full-text available
The present paper describes part of the work that is being carried out to investigate the formation of Ti-Al-Ag nanostructured intermetallic compounds using Mechanical Alloying (MA). Mixtures of elemental powders with nominal compositions 52TiH2-(48-x)AlxAg (x=0, 2 and 4 at. %) were milled for 25h at 500rpm in a planetary ball mill. The MA led to t...
Article
Ti(H2)-46Al-2Ag and Ti(H2)-44Al-4Ag (at%) alloys were produced by mechanical alloying of elemental powders in a planetary ball mill for 50h. It was found that for homogeneous to be obtained mechanical alloying has to be more intensive and/or the subsequent consolidation/heat-treatment need to be modified.
Article
Ti-48(at%)Al and Ti-48(at%)Al-1(at%)Ag PM alloys were produced through Reactive Hot Isostatic Pressing (RHIP). Two Al powder sizes and two RHIP holding times at 1200°C/180MPa were used. The produced alloys were given a heat treatment of 2h at 1250°C, followed by 10h at 1000°C and characterized. The effect of the varied parameters including the l(at...
Article
Dynamic Young's Modulus (E) was measured by impulse excitation of vibration in rectangular bars of near γ-TiAl alloys and in rods of AlNi/50v% SiC composites. Stainless steel 316 was used to assess the E results obtained with this method for a rod specimen cut from the uniform cross section length of a threaded end specimen, against the ones obtain...
Conference Paper
Ti-48(at%)Al and Ti-48(at%)Al-l(at%)Ag PM alloys were produced through Reactive Hot Isostatic Pressing (RHIP). Two Al powder sizes and two RHIP holding times at 1200degreesC/180MPa were used. The produced alloys were given a heat treatment of 2h at 1250degreesC, followed by 10h at 1000degreesC and characterized. The effect of the varied parameters...
Article
Elemental powder mixtures of Ti-48at%Al were consolidated by Reactive Hot Isostatic Pressing (RHIP) at 800°C, 1100°C and 1250°C/180MPa/2h. The canned cold isostatic pressed mixtures were previously degassed by heating up at a rate of 5°C/min. up to 450°C in vacuum. Based on differential thermal analysis (DTA) results, the relative sizes of the Ti a...
Article
Elemental powder mixtures of Ti-48at%Al were consolidated by Reactive Hot Isostatic Pressing (RHIP) at 800 degreesC, 1100 degreesC and 1250 degreesC/180MPa/2h. The canned cold isostatic pressed mixtures were previously degassed by heating up at a rate of 5 degreesC/min. up to 450 degreesC in vacuum. Based on differential thermal analysis (DTA) resu...

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Projects (2)
Project
The research activities of LocalEnergy are focused on the development of new, efficient, cost-effective, durable and easy-to-process thermoelectric and photovoltaic materials based on tetrahedrite, a cooper antimony sulfosalt (Cu12-xMxSb4S13, x less or equal to 2) mineral consisting of earth-abundant and relatively non-toxic elements. Specifically, LocalEnergy will address to the use of both natural and synthetic tetrahedrites for thermoelectric applications and of synthetic tetrahedrites-based materials as new solar absorbers for photovoltaic applications. This strategy is very relevant considering that the current thermoelectric materials and chalcogenide thin-film solar cells are based on rare or toxic elements. Consortium: Principal Contractor: LNEG; Participating Institution: IST-ID/C2TN and NOVA.ID.FCT/CENIMAT|i3N; Collaborator Institution: DGEG This work is funded by national funds through the FCT – Fundação para a Ciência e a Tecnologia, I.P., under the project PTDC/EAM-PEC/29905/2017.
Project
MIDAS— Micro and Nanoscale Design of Thermally Actuating Systems (Project number 612585, FP7-PEOPLE-2013-IRSES Marie Curie Actions— International Research Staff Exchange Scheme. URL: http://sites.fct.unl.pt/midas/ Starting January 2014. Duration: 4 years - Universitatea “Politehnica” din Timisoara (UPT; Project Coordinator), Romania. Partners: - NOVA.id.FCT -Universidade Nova de Lisboa, - Universitat de les Illes Baleares (UIB), Espanha, - Cranfield University (CU), UK, - Laboratório Nacional de Energia e Geologia (LNEG), Portugal, - Instituto Militar de Engnharia (IME), Brazil, - University of Waterloo (WU), Canadá, - Indian Institute of Science (IISc), India; - Russian Academy of Sciences (RAS), Russia, - University of Science and Technology (USTB), Beijing, China. Objective Nowadays extended socio-economical evolution and international collaboration lead to an unprecedented progress in materials research, by discoveries of new materials on one hand and by the development of known structural and functional materials functionality on the other, as well as by the extension of the research area toward nanodimensional realm. Smart or Intelligent Systems based on functional materials – a promise and a challenge at the same time - are currently the object of intense research, with much of the effort dedicated to the actuating function. In recent years it has been observed that the functionality can be significantly improved by micro and nanostructural control. The Micro and Nanoscale Design of Thermally Actuating Systems – MIDAS - project aims to develop long-lasting cooperation based on the transfer of knowledge and networking activities between European and eligible Third country partners, through a coordinated research activity, focused on improving the functionality of shape memory alloys, as elements for sustainable development and progress through innovation. The proposal involves well-established research teams with significant activity, relevant scientific results and complementary of expertise related to fields like: Physics, Mechanical engineering or Materials Science as well as with proven potential to develop research-related activities in the field of the proposal. The proposal has an important applicative component, thus it will address actors in private companies interested in exploiting the results of the proposal. The main objectives of the MIDAS project, identified within the framework of the FP7- IRSES Call are: • To set-up a network of collaborative applied research between partners involved in complementary activities with the aim to develop actuating materials and applications. • To explore novel paths for enhancing the functionality of thermally actuated materials belonging to the shape memory alloy group. The use of a knowledge diversity related to the formation and fields is expected to be the driving force in the effort to find new paths. • To identify innovative ideas worth to be considered by private companies for the development and optimization of novel applications. • To provide a framework for optimal transfer of knowledge between the partners and between generations of scientists via adequately tailored exchange programs for each type of exchange beneficiary. • To generate a proper environment for interaction with private entrepreneurs interested in exploiting the results of the research collaboration. • To provide knowledge to be shared in educational activities as well as for dissemination of information to other socio-economical actors and • To provide a basis for advanced research activities and to favor the collaboration and its expansion even beyond the funding provided by this call, via new joint grant applications, publications or conferences and seminars. Specific objectives derived from these are identified in relationship with the Work Packages designed for the MIDAS project. Papers published Work resulting from WP2 (Severe Plastic Deformation) “Fracture modes during severe plastic deformation of NiTi shape memory alloys”. C.M. Craciunescu, R.J.C. Silva, F.M. Braz Fernandes. Fizika Metalliv i Metallovedenie (Physics of Metals and Metallography) 116:7 (2015) pp. 698-705 (DOI: 10.1134/S0031918X15070030). IF:0.672; IF5Y: - Work resulting from WP5 (Welding) “Shape memory effect of laser welded NiTi”. J.P. Oliveira, F.M. Braz Fernandes, N. Schell, R.M. Miranda. Functional Materials Letters, 18-6 (2015) 1550069. (DOI: 10.1142/S1793604715500691). IF:1.606; IF5Y: 1.47 “High Strain and Long Duration Cycling Behavior of Laser Welded NiTi Sheets”. J.P. Oliveira, R.M. Miranda, N. Schell, F.M. Braz Fernandes. International Journal of Fatigue 83 (2016) 195–200. IF: 2.275; IF5Y: 1.974 “Laser welded superelastic Cu–Al–Mn shape memory alloy wires”. J.P. Oliveira, B. Panton, Z. Zeng, T. Omori, Y. Zhou, R.M. Miranda, F.M. Braz Fernandes. Materials and Design 90 (2016) pp. 122–128. (DOI: 10.1016/j.matdes.2015.10.1250264-1275). IF: 3.501; IF5Y: 3.626 “Laser joining of NiTi to Ti6Al4V using a Niobium interlayer”. J.P. Oliveira, B. Panton, Z. Zeng, C.M. Andrei, Y. Zhou, R.M. Miranda, F.M. Braz Fernandes. Acta Materialia 105 (2016) pp. 9-15. (DOI: 10.1016/j.actamat.2015.12.021). IF: 4.465; IF5Y: 4.87 “Tungsten inert gas (TIG) welding of Ni-rich NiTi plates: functional behaviour”. J.P. Oliveira, D. Barbosa, F.M. Braz Fernandes, R.M. Miranda. Smart Materials and Structures 25 (2016) 03LT01 (7pgs). (10.1088/0964-1726/25/3/03LT01). IF :2.502; IF5Y: 2.74 “Martensite Stabilization During Superelastic Cycling of Laser Welded NiTi Plates”, J. P. Oliveira, F. M. Braz Fernandes, N. Schell, R. M. Miranda, Materials Letters (accepted for publication) DOI: 10.1016/j.matlet.2016.02.107. IF:2.489; IF5Y: 2.466 “On the Mechanisms for Martensite Formation in YAG Laser Welded Austenitic NiTi”, J. P. Oliveira, F. M. Braz Fernandes, R. M. Miranda, N. Scheel, (accepted for publication in Shape Memory and Superelasticity) DOI: 10.1007/s40830-016-0058-z “Dissimilar laser welding of NiTi shape memory alloy and copper, Smart Materials and Structures”, Z. Zeng, B. Panton, J. P. Oliveira, A. Han, Y. Zhou, vol 24, 125036, 2015. DOI: 10.1088/0964-1726/24/12/125036. IF: 2.502 R. M. Miranda, E. Assunção, R. J. C. Silva, J. P. Oliveira, L. Quintino, Fiber laser welding of NiTi to Ti-6Al-4V, The International Journal of Advanced Manufacturing Technology, vol. 81, 1533-1538, 2015. DOI: 10.1007/s00170-015-7307-8. IF: 1.458