NIMP| Magdalena GALATANU, Author at NIMP

Publications

1. Evaluation of thermal properties of CuCrFeV (Ti, Ta, W, Mo) for nuclear fusion applications

Authors: Rodríguez-López, A; Savoini, B; Monge, MA; Galatanu, A; Galatanu, M

Published: DEC 2024, NUCLEAR MATERIALS AND ENERGY, 41, 101767, DOI: 10.1016/j.nme.2024.101767

This work investigates the influence of composition on the thermal properties of the high entropy alloy family Cu5Cr35Fe35V20-X-5 (at. %), where X = Ti, Ta, W or Mo in the framework of acting as a thermal barrier between the W-based plasma-facing elements and the CuCrZr or Cu-based heat sink components of the fusion reactor. The alloys were produced by arc melting and their microstructure and mechanical properties were previously characterized by XRD, SEM, and Vickers hardness measurements. Thermal properties have been measured on as-cast at thermally treated alloys using the laser flash method in the temperature range 25 degrees C to 600 degrees C to determine the thermal diffusivity, alpha, thermal conductivity, lambda, and specific heat, C-p. Dilatometry experiments were also carried out to obtain the linear thermal expansion coefficient, CTE, as a function of temperature. For all materials, the thermal conductivity increases with temperature from 15 W/m<middle dot>K at RT to 28 W/m<middle dot>K at 600 degrees C and does not significantly depend on the thermal treatment for the Mo-HEA and W-HEA, but increases after aging for the Ta-HEA and Ti-HEA. These values are lower than those of W (similar to 122 W/m<middle dot>K at 600 degrees C) and much lower than for CuCrZr-IG (similar to 354 W/m<middle dot>K at 400 degrees C). The thermal expansion coefficients of these HEAs, similar to 10 x 10(-6) degrees C-1 at RT and similar to 2 x 10(-6) degrees C-1 at 650 degrees C are between those of CuCrZr and the W for the entire operative temperature range. These results indicate that the Cu5Cr35Fe35V20-X-5 (X = Ti, Ta, W, Mo) HEAs have a promising combination of the thermophysical properties, lambda, C-p and CTE, to act as thermal barrier in plasma-facing components that require the union of W- and Cu-based materials.

2. Experimental Research on the Influence of Repeated Overheating on the Thermal Diffusivity of the Inconel 718 Alloy

Authors: Arva, ERU; Abrudeanu, M; Negrea, DA; Galatanu, A; Galatanu, M; Rizea, AD; Anghel, DC; Branzei, M; Jinga, AI; Petrescu, MI

Published: SEP 2024, APPLIED SCIENCES-BASEL, 14, 8574, DOI: 10.3390/app14188574

The Inconel 718 superalloy, a precipitation-hardenable material, is of particular interest for applications involving components operating under extreme conditions due to its excellent mechanical properties, high corrosion resistance at temperatures up to 700 degrees C, and good workability. At high temperatures, thermal transfer processes are crucial for temperature distribution across the component's section, structural transformations, and variations in the alloy's properties. The history of accidental overheating events is critical for the microstructure and properties of the alloy. Studies on thermal transfer in the Inconel 718 alloy available in the literature typically focus on the alloy in its as-delivered state. The experimental research presented in this paper examines the influence of repeated overheating history on the thermal diffusivity of the alloy.

3. The Influence of Cyclic Thermal Shocks at High Temperatures on the Microstructure, Hardness and Thermal Diffusivity of the Rene 41 Alloy

Authors: Arva, ERU; Negrea, DA; Galatanu, A; Galatanu, M; Moga, SG; Anghel, DC; Branzei, M; Stoica, L; Jinga, AI; Petrescu, MI; Munteanu, C; Abrudeanu, M

Published: MAY 2024, MATERIALS, 17, 2262, DOI: 10.3390/ma17102262

The precipitation-hardenable nickel-based superalloy Rene 41 exhibits remarkable mechanical characteristics and high corrosion resistance at high temperatures, properties that allow it to be used in high-end applications. This research paper presents findings on the influence of thermal shocks on its microstructure, hardness, and thermal diffusivity at temperatures between 700 and 1000 degrees C. Solar energy was used for cyclic thermal shock tests. The samples were characterized using microhardness measurements, optical microscopic analysis, scanning electron microscopy coupled with EDS elemental chemical analysis, X-ray diffraction, and flash thermal diffusivity measurements. Structural transformations and the variation of properties were observed with an increase in the number of shocks applied at the same temperature and with temperature variation for the same number of thermal shocks.

4. Microengineering Design for Advanced W-Based Bulk Materials with Improved Properties

Authors: Galatanu, M; Enculescu, M; Galatanu, A; Ticos, D; Dumitru, M; Ticos, C

Published: MAR 2023, NANOMATERIALS, 13, 1012, DOI: 10.3390/nano13061012

In fusion reactors, such as ITER or DEMO, the plasma used to generate nuclear reactions will reach temperatures that are an order of magnitude higher than in the Sun's core. Although the plasma is not supposed to be in contact with the reactor walls, a large amount of heat generated by electromagnetic radiation, electrons and ions being expelled from the plasma will reach the plasma-facing surface of the reactor. Especially for the divertor part, high heat fluxes of up to 20 MW/m(2) are expected even in normal operating conditions. An improvement in the plasma-facing material (which is, in the case of ITER, pure Tungsten, W) is desired at least in terms of both a higher recrystallization temperature and a lower brittle-to-ductile transition temperature. In the present work, we discuss three microengineering routes based on inclusions of nanometric dispersions, which are proposed to improve the W properties, and present the microstructural and thermophysical properties of the resulting W-based composites with such dispersions. The materials' behavior after 6 MeV electron irradiation tests is also presented, and their further development is discussed.

5. Two Roman Glass Furnaces Discovered at Resca-Romula (Romania)

Authors: Negru, M; Badica, P; Alexandru-Dinu, A; Galatanu, M; Kuncser, A; Patroi, D; Artene, I

Published: OCT 1 2023, AMERICAN JOURNAL OF ARCHAEOLOGY, 127, DOI: 10.1086/726009

Romula (today Resca, Dobrosloveni Village, Romania) was the largest urban and economic center of Dacia Inferior (Malvensis), a Roman province located in the north of the Lower Danube region. In this context, the city market included workshops for the production of ceramic, metal, stone, bone, and glass objects. In 2013, 2015, and 2018, during excavations of the former Roman city, two rectangular glass furnaces were discovered. One has only one chamber, the other has two chambers. A melted glass layer was found on the walls of furnace no. 1, as well as in one room of furnace no. 2. Broken fragments of glass were also found in both. The furnaces are located in the central area of the Roman city. The evidence suggests that the furnaces belong to secondary glass workshops. The glass may have arrived in raw form, where it was remelted and processed. The discovery of these furnaces contributes to the growing body of evidence for Roman glass production around the empire.1

6. Obtaining and characterisation of thermoelectric Mg2Si compound via wet and dry mechanical alloying and spark plasma sintering

Authors: Cebotari, V; Popa, F; Marinca, TF; Neamtu, BV; Sechel, NA; Galatanu, M; Galatanu, A; Chicinas, I

Published: SEP-OCT 2023, JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 26, DOI: 10.1016/j.jmrt.2023.09.167

Mg2Si thermoelectric compound was obtained by dry and wet (isohexane and benzene) mechanical alloying route. The Mg2Si compound was characterised by X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), laser particle size analysis and thermoelectric measurements. After 14 h of milling, the complete reaction of the elements is achieved by both routes. The powders particle size distribution obtained after 14 h of dry or wet milling (using benzene) reveals a bimodal curve. The wet milling moves the particle size distribution towards smaller particle sizes. The SEM analysis confirms the results of particles size analysis. DSC analyses performed for samples milled up to 14 h present stress relief and recrystallisation thermal events. For the benzene wet-milled sample, the DSC curve shows an additional thermal event at 350'C, associated with benzene removal. Thermoelectric properties were determined on spark plasma sintered compacts. The milling process with benzene leads to a higher value of Seebeck coefficient (z580 mV/K). The electrical conductivity is low at room temperature and increases exponentially with temperature. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

7. The inclusion of ceramic carbides dispersion in In and Yb filled CoSb3 and their effect on the thermoelectric performance

Authors: Popescu, B; Galatanu, M; Enculescu, M; Galatanu, A

Published: FEB 10 2022, JOURNAL OF ALLOYS AND COMPOUNDS, 893, DOI: 10.1016/j.jallcom.2021.162400

In this work, thermoelectric properties of the nanocomposite materials produced via ball milling followed by spark plasma sintering from In0.2Yb0.2Co4Sb12 double filled skutterudite (SKT) with silicon and tungsten carbide inclusions are investigated. The nanocomposites with low volume ratios of beta-SiC and '-WC have a significantly increased power factor, while the lattice thermal conductivity is lowered only for beta-SiC composites. The power factor enhancement in '-WC/SKT composite compensates the increase of its thermal conductivity, and as a consequence, the maximum value of the figure of merit, 0.97, is attained for 0.33 v% 'WC at 450 degrees C, with 15% higher than that of the simple skutterudite sample. (c) 2021 Elsevier B.V. All rights reserved.

8. Influence of the synthesis parameters on the transport properties of Mg2Si0.4Sn0.6 solid solutions produced by melting and spark plasma sintering

Authors: Assahsahi, I; Popescu, B; Enculescu, M; Galatanu, M; Galca, AC; El Bouayadi, R; Zejli, D; Galatanu, A

Published: APR 2022, JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 163, DOI: 10.1016/j.jpcs.2021.110561

In this work, the influence of the preparation route on the structural, morphological, and thermoelectric properties of the Mg2Si0.4Sn0.6 solid solutions is investigated. The synthesis based on melting the constituent elements in a closed graphite crucible followed by spark plasma sintering allows mixing elements with a large difference of their melting temperatures and a good control of sample stoichiometry. The optimized synthesis route is validated by the doped V and Sb samples, which yield good thermoelectric performance. The n-type doping leads to two orders of magnitude increase of the carrier concentration, and thus a subsequent increase of the electrical conductivity, which, in turn, augments greatly the power factor of the Mg1.98V0.02Si0.385Sn0.6Sb0.015 to 42.61 x10(-4) Wm(-1)K 2 at 650K. Although doping slightly enlarges the thermal conductivity, a peak value of the figure of merit ZT similar to 1.15 is obtained at 723K, which is 20 times higher than the ZT of un-doped material.

9. Irradiation of W and K-Doped W Laminates without or with Cu, V, Ti Interlayers under a Pulsed 6 MeV Electron Beam

Authors: Ticos, D; Galatanu, M; Galatanu, A; Dumitru, M; Mitu, ML; Udrea, N; Scurtu, A; Ticos, CM

Published: FEB 2022, MATERIALS, 15, 956, DOI: 10.3390/ma15030956

Small multilayered laminated samples consisting of stacks of W (or K-doped W) foils without an interlayer or with interlayers from Cu, V, and Ti were exposed to a pulsed electron beam with an energy of 6 MeV in several irradiation sessions. All samples maintained their macroscopic integrity, suggesting that the W-metal laminate concept is compatible with high heat flux applications. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after each irradiation session. The experimental results indicate that electron beam irradiation induces obvious modifications on the surface of the samples. Morphological changes such as the appearance of nanodroplets, nanostructures, and melting and cracking, depending on the sample type and the electron beam fluence, are observed. The irradiation is carried out in a vacuum at a pressure of 2 to 4 x 10(-2) torr, without active cooling for the samples. The structures observed on the surface of the samples are likely due to electron beam heating and vaporization followed by vapor condensation in the volume adjacent to the surface.

10. The effects of mechanical alloying on the physical and thermal properties of CuCrFeTiV alloy

Authors: Antao, F; Dias, M; Correia, JB; Galatanu, A; Galatanu, M; Mardolcar, UV; Myakush, A; Cruz, MM; Casaca, A; da Silva, RC; Alves, E

Published: JAN 2021, MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS, 263, DOI: 10.1016/j.mseb.2020.114805

The present work reports the production and key properties of the CuCrFeTiV high entropy alloy synthetized mechanical alloying and spark plasma sintering. The milled powders and the as-sintered samples were analysed through scanning electron microscopy, coupled with energy dispersive X-ray spectroscopy and particle induced X-ray emission. Magnetic properties together with electrical resistivity, thermal conductivity, specific heat differential thermal analysis were also evaluated on the consolidated samples. The powders reveal an increasing content in iron as the millings are prolonged up to 20 h. The elemental composition of the sintered alloy, determined through particle induced X-ray emission, confirms the final composition after mechanical alloying with an increase of iron and a decrease in the remaining elements. Furthermore, although the alloy presents electrical resistivity typical of a high entropy alloy, a ferromagnetic behaviour was found, consistently with major Fe content as detected in prior observations. Finally, thermal measurements show that this CuCrFeTiV entropy alloy possesses thermal properties suitable for its potential use as thermal barriers.

11. Beneficial effects of a WC addition in FAST-densified tungsten

Authors: Novak, S; Kocen, M; Zavagnik, AS; Galatanu, A; Galatanu, M; Tarancon, S; Tejado, E; Pastor, JY; Jenus, P

Published: JAN 20 2020, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 772, DOI: 10.1016/j.msea.2019.138666

The particle reinforcement of fusion-relevant tungsten through the incorporation of tungsten sub-carbide W2C particles at the grain boundaries is demonstrated as an effective way of eliminating the harmful W oxide, enhancing densification and stabilising the composite's microstructure and flexural strength at room and high temperatures. The W2C particles are formed in situ during the sintering by carbon diffusion from WC nano-particles added as a precursor to the W matrix. Even in an extremely fast sintering process using Field-Assisted Sintering Technology (FAST, 1900 degrees C, 5 min), the added WC completely transforms to W2C, resulting in a W-W2C composite. While at least 5 vol % of WC nanoparticles are needed to eliminate the oxide, approximately 10 vol % result in a W-W2C composite with favourable characteristics: high density, high flexural strength at RT (>1200 MPa) as well as at elevated temperatures, and high thermal conductivity, which remains above 100 W/mK up to 1000 degrees C.

12. Synthesis and characterization of conducting aniline and o-anisidine nanocomposites based on montmorillonite modified clay

Authors: Kenane, A; Galca, AC; Matei, E; Yahiaoui, A; Hachemaoui, A; Benkouider, AM; Bartha, C; Istrate, MC; Galatanu, M; Rasoga, O; Stanculescu, A

Published: JAN 2020, APPLIED CLAY SCIENCE, 184, DOI: 10.1016/j.clay.2019.105395

A study on clay mineral polymer nanocomposites (CPN), namely polyaniline/montmorillonite-cetyltrimethylammonium bromide (PANI/Mt-CTAB), poly o-anisidine/montmorillonite-cetyltrimethylammonium bromide (poly(o-ANIS)/Mt-CTAB) and poly o-anisidine-co-aniline/montmorillonite-cetyltrimethylammonium bromide (poly(o-ANIS-co-ANI)/Mt-CTAB), synthesized by oxidative chemical polymerization method is presented. The nanocomposites have been characterized by Fourier transform infrared spectroscopy, UV-vis spectroscopy, and cyclic voltammetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and thermogravimetry and differential scanning calorimetry analysis. By UV-vis measurements different electronic transitions for the CPNs were pointed out. The voltammograms indicate that the synthetized materials are electroactive. The FTIR analysis reveals the characteristic bands of the polymers and of the Mt-CTAB. The shift of the bands to higher/lower wavenumbers demonstrate the interaction between the pristine polymers macromolecular chains and the montmorillonite (Mt). The intercalation of the polymers inside the mineral clay was confirmed by the increased interlayer distance connected with the position of the 011 diffraction plane of the Mt., and the intercalation and exfoliation states were highlighted in the scanning and transmission electron microscopy images. The obtained results are encouraging in respect with the purpose to use them in the field of photovoltaic applications.

13. Development of W-monoblock divertor components with embedded thermal barrier interfaces

Authors: Galatanu, M; Cioca, M; Ighigeanu, A; Ruiu, G; Enculescu, M; Popescu, B; Galatanu, A

Published: SEP 2019, FUSION ENGINEERING AND DESIGN, 146, 1354, DOI: 10.1016/j.fusengdes.2019.02.074

In the case of DEMO fusion reactor, the divertor should be able to extract a steady heat flux of about 10 MW/m(2). A promising concept is the W-monoblock which should be connected to a CuCrZr or an advanced Cu ODS alloy pipe passing through the W component. Taking into account the optimum operating temperature windows for W and existing Cu-based alloys and the thermal expansion coefficients mismatch of these two materials, a "thermal barrier" interface material is inserted in between in order to mitigate the thermal stresses and to optimize the heat flow through divertor components. In this work we investigate the feasibility to realize such divertor components using materials produced by FAST (field assisted sintering technology). This powder metallurgy technique was used firstly to produce W or W-based composites and the thermal barriers in an almost final shape and then to join the materials in realistic divertor mock-ups. The thermal barrier materials are various Cu-based composites which are included both as single material or as functionally graded components. The interface quality between different materials is investigated by scanning electron microscopy and the heat flow through components is evaluated using simulations.

14. Sintering and irradiation of copper-based high entropy alloys for nuclear fusion

Authors: Dias, M; Antao, F; Catarino, N; Galatanu, A; Galatanu, M; Ferreira, P; Correia, JB; da Silva, RC; Goncalves, AP; Alves, E

Published: SEP 2019, FUSION ENGINEERING AND DESIGN, 146, 1828, DOI: 10.1016/j.fusengdes.2019.03.044

In this study, CuxCrFeTiV (x = 0.21, 0.44, 1 and 1.7 M ratio) high entropy alloys have been devised for thermal barriers between the plasma facing tungsten tiles and the copper-based heat sink in the first wall of nuclear fusion reactors. The high entropy alloys were produced by ball milling the elemental powders, followed by consolidation with spark plasma sintering. Irradiation of the equiatomic CuCrFeTiV sample was carried out at room temperature with Ai(+) (300 keV) beams with a fluence of 3 x 10(20) at/m(2). Structural changes prior and after irradiation were investigated by scanning electron microscopy, coupled with energy dispersive X-ray spectroscopy, X-ray diffraction and thermal diffusivity. Preliminary results showed the presence of heterogenous and multiphasic microstructures in all samples. Moreover, with the increase of the Cu content it is possible to observe the formation of Cu-rich structures. The diffractogram of the CuCrFeTiV sample revealed major peaks of a BCC crystal structure and minor peaks of a FCC crystal structure. In addition, after irradiation no modifications in the CuCrFeTiV microstructure or in the diffractogram were observed.

15. Thermophysical and mechanical properties of W-Cu laminates produced by FAST joining

Authors: Galatanu, A; Galatanu, M; Enculescu, M; Reiser, J; Sickinger, S

Published: SEP 2019, FUSION ENGINEERING AND DESIGN, 146, 2374, DOI: 10.1016/j.fusengdes.2019.03.193

W-laminates are multi layered composites realized from alternately stacked W and a second metal foils. Such materials are promising candidates for W-based structural materials for fusion reactors like DEMO or beyond concepts, due to the fact that cold-rolled ultrafine-grained thin W foils show exceptional properties in terms of ductility, toughness and ductile to brittle transition (DBT), in contrast to classic bulk W materials. Therefore, different routes to transfer the W foils properties to bulk materials have been investigated. In this work we present the results obtained for W-Cu laminates produced via a FAST (Field Assisted Sintering Technique) joining route. The main advantages of FAST resides in the short processing time, with subsequent lower recrystallization detrimental effects. Structural and thermophysical properties show that the best materials are obtained for about 100 mu m thick W foils and 50-100 mu m thick Cu foils, while tensile and Charpy impact tests results show that the FAST processed W-Cu laminates are similar to the W-Cu laminates obtained by diffusion bonding.

16. High temperature thermo-physical properties of SPS-edW-Cu functional gradient materials

Authors: Galatanu, M; Enculescu, M; Galatanu, A

Published: FEB 2018, MATERIALS RESEARCH EXPRESS, 5, DOI: 10.1088/2053-1591/aaa860

The divertor of a fusion reactor like DEMO requires materials able to withstand high heat fluxes and neutron irradiation for several years. For the water cooling concept of this essential part of the reactor, the most likely plasma facing material will be W, while the heatsink material considered is CuCrZr or an improved version of such a Cu-based alloy. To realize W-Cu alloy joints able to withstand thousands of thermal cycles can be difficult due to the difference between the thermal expansion coefficients of these materials. In this work we investigate the possibility to realize such joints by using W-Cu functional gradient materials (FGMs) produced from nanometric and micrometric metallic powders mixtures and consolidated by spark plasma sintering at about 900 degrees C. Morphological and thermal properties investigations, performed for typical compositions, shows that the best results are obtained using powders with micrometric dimensions. A resulting 1 mm thick, 3 layers W-Cu FGM produced by this simple method shows a remarkable almost constant thermal conductivity value of 200 W m(-1) K-1, from room temperature up to 1000 degrees C.

17. Thermophysical properties of Cu-ZrO2 composites as potential thermal barrier materials for a DEMO W-monoblock divertor

Authors: Galatanu, M; Enculescu, M; Galatanu, A

Published: FEB 2018, FUSION ENGINEERING AND DESIGN, 127, 184, DOI: 10.1016/j.fusengdes.2018.01.011

DEMO fusion reactor divertor is expected to extract a heat flux of about 10 MW/m(2). One of the most promising concept design for it is the W-monoblock, which should be connected to a CuCrZr or an advanced Cu ODS alloy pipe passing through the W component. Since the optimum operating temperature windows for W and existing Cu alloys are far away from overlapping, a suited interface is needed to keep the adjacent materials as close as Possible to their respective temperature operating windows. The interface material should therefore have a low enough thermal conductivity to act as a thermal barrier and a thermal expansion coefficient suited to protect the W-pipe joint from stresses induced by the different thermo-mechanical properties of W and Cu-alloys. As interface materials we have considered Cu-ZrO2 composites produced by powder metallurgy route. Such materials can be realized in an unexpected large compositional range (up to at least 90% ZrO2 volume concentration) and be easily further joined to both W and Cu-alloys by an electrical field assisted technology. We analyse their microstructure and thermo-physical properties both as single materials and included in W-thermal barrier-CuCrZr 3-layers systems in comparison to those of previously produced Cu-ased composites and commercially available Cu foams.

18. Cracks and nanodroplets produced on tungsten surface samples by dense plasma jets

Authors: Ticos, CM; Galatanu, M; Galatanu, A; Luculescu, C; Scurtu, A; Udrea, N; Ticos, D; Dumitru, M

Published: MAR 15 2018, APPLIED SURFACE SCIENCE, 434, 1128, DOI: 10.1016/j.apsusc.2017.11.057

Small samples of 12.5 mm in diameter made from pure tungsten were exposed to a dense plasma jet produced by a coaxial plasma gun operated at 2 kJ. The surface of the samples was analyzed using a scanning electron microscope (SEM) before and after applying consecutive plasma shots. Cracks and craters were produced in the surface due to surface tensions during plasma heating. Nanodroplets and micron size droplets could be observed on the samples surface. An energy-dispersive spectroscopy (EDS) analysis revealed that the composition of these droplets coincided with that of the gun electrode material. Four types of samples were prepared by spark plasma sintering from powders with the average particle size ranging from 70 nanometers up to 80 mu m. The plasma power load to the sample surface was estimated to be 4.7 MJ m(-2) s(-1/2) per shot. The electron temperature and density in the plasma jet had peak values 17 eV and 1.6 x 10(22) m(-3), respectively. (C) 2017 National Institute for Laser, Plasma, and Radiation Physics (INFLPR). Published by Elsevier B.V. All rights reserved.

19. Production and Structural Characterization of Some Magnesium Matrix Composites Reinforced with Amorphous/Nanocrystalline NiTi Particulates

Authors: Ciurdas, M; Necsulescu, DA; Pantilimon, CM; Ion, V; Galatanu, M; Ruiu, G; Dumitrescu, RE

Published: DEC 2018, REVISTA DE CHIMIE, 69, 3507, DOI:

Two mixtures of elemental nickel and titanium powders in atomic proportions of 50% Ni + 50% Ti and 32% Ni + 68% Ti, respectively, were ground for 40 hours in a high energy planetary mill. In the case of the first mixture, the mechanical alloying was totally produced, while for the second, the alloying was partial. In both mixtures, qualitative X-ray diffraction phase analysis revealed the presence of metastable phases, such as Ni HC and NiTi- R-phase. Also, the equiatomic mixture is characterized by a partially amorphous structure. 10% of each type of mixture submitted to milling was used as reinforcing element in the form of particulates for two magnesium matrix composites. They were obtained by sintering in the plasma at 590 degrees C. In the case of the reinforced with the second mixture composite, the production of new phases other than the matrix and those present in the mixture of nickel and titanium powders after milling were recorded. The electron microscopy images of the two composites have resistant, free of micropores or microcracks matrix / particulates interfaces. The Mg-10% (32 at% Ni + 68 at% Ti) composite is characterized by Vickers hardness higher than that of the composite reinforced with the equiatomic mixture.

20. Cu-based composites as thermal barrier materials in DEMO divertor components

Authors: Galatanu, M; Enculescu, M; Ruiu, G; Popescu, B; Galatanu, A

Published: NOV 2017, FUSION ENGINEERING AND DESIGN, 124, 1134, DOI: 10.1016/j.fusengdes.2017.02.031

For DEMO fusion reactor an expected heat flux of about 10MW/m(2) should be extracted by the divertor which will have, most likely, an armour part made of W and a following heat sink part made of Cu, or ODS Cu alloy. Unfortunately, for these materials the optimum operating temperature windows do not overlap. Thermal barrier materials are interface materials included in such components, aiming to keep the temperatures of both armour and heat sink parts in the corresponding operating windows, and to mitigate the effects of their different thermomechanical properties. Here we propose a simple spark plasma sintering route to create Cu-based composites with a high content (10-40 vol%) of various dispersed materials (Al or Y oxides, C, SiC), allowing a fine tuning of the content and a large pool of predefined shapes and dimensions. The resulting specimens can be further joined to armour and heatsink components via a similar electrical field assisted technology. Micro-structural and thermal properties are investigated for these materials allowing to select the most suited materials in view of their thermal conductivity and thermal expansion coefficients. (C) 2017 The Authors. Published by Elsevier B.V.

21. Thermal conductivity and diffusivity of Cu-Y alloys produced by different powder metallurgy routes

Authors: Carro, G; Munoz, A; Monge, MA; Savoini, B; Galatanu, A; Galatanu, M; Pareja, R

Published: NOV 2017, FUSION ENGINEERING AND DESIGN, 124, 1160, DOI: 10.1016/j.fusengdes.2017.01.017

Full density Cu-1%Y and Cu-0.8%Y alloys have been produced by different powder metallurgy routes and subsequent hot isostatic pressing. Some of the alloys have been subjected to equal channel angular pressing (ECAP) via B-c route up to 8 passes. ECAP deformation homogenizes and refines the microstructure up to attaining a sub-micron grain structure. Thermal properties have been characterized by the laser flash method in the temperature range 373-773 K. The ECAP process, irrespective of the production route, enhanced the thermal conductivity to values similar to those for CuCrZr (ITER grade). The linear thermal expansion coefficient was temperature independent for all materials. (C) 2017 Elsevier B.V. All rights reserved.

22. Exciton-phonon interaction in PbI2 revealed by Raman and photoluminescence studies using excitation light overlapping the fundamental absorption edge

Authors: Baibarac, M; Smaranda, I; Scocioreanu, M; Mitran, RA; Enculescu, M; Galatanu, M; Baltog, I

Published: OCT 2015, MATERIALS RESEARCH BULLETIN, 70, 772, DOI: 10.1016/j.materresbull.2015.06.012

Enhancement at low temperatures of the Raman scattering excited by laser light situated near the edge of the fundamental absorption band is often encountered when studying nanoscale structures. Theory devoted to this phenomenon has established that it originates in an exciton-phonon interaction process, known as the Frohlich interaction, Such a phenomenon was observed in PbI2. The experimental data conclude that the enhancement of the Raman emission results from: (i) an optical excitation near edge of fundamental absorption band; (ii) it is conditioned by the existence of excitonic PL; (iii) its occurrence is different over stokes and anti-stokes Raman branches as result of the different overlapping of the Raman spectral range and the excitonic PL band profile; and (iv) it appears more intense in micrometric powders or in bulk crystalline material. These data are interpreted as stimulated Raman effect resulting from the mixing of the pump laser light and the excitonic light. (C) 2015 Elsevier Ltd. All rights reserved.

23. Direct sintering of SiC-W composites with enhanced thermal conductivity

Authors: Galatanu, M; Popescu, B; Enculescu, M; Tiseanu, I; Craciunescu, T; Galatanu, A

Published: OCT 2013, FUSION ENGINEERING AND DESIGN, 88, 2602, DOI: 10.1016/j.fusengdes.2013.05.036

Different types of SiC-W composites have been realized by spark plasma sintering in a single step process starting with beta SiC nanometric powder, W nanometric and micrometric sized powders, and W foils. SEM, EDX, XRD and X-ray tomography have been used to analyze the sample morphology while the thermal properties of the resulting materials have been investigated up to 1000 degrees C using a LFA thermal analyzer. The results show the possibility to produce dense W-SiC composites, with enhanced thermal conductivity using a relatively simple route. (C) 2013 Elsevier B.V. All rights reserved.

Dr. Magdalena GALATANU

Scientific Researcher III