National Institute Of Materials Physics - Romania

Structural and electronic transport features of high quality epitaxial metastable fcc W and beta-W2N thin films compatible with spintronic multilayer nanosystems are reported in a parallel approach. The epitaxial layers have been successfully prepared in a broad range of thicknesses from a few to tens of nanometers. The scalable method of auxiliary plasma assisted substrate magnetron sputtering was used. The epitaxy relationship between the thin films and MgO (100) single-crystal substrate is highlighted by high resolution XRD investigations of the reciprocal space. Electron transport properties are discussed with respect to the striking behavior observed via resistivity over temperature cycles. The chemical stability as active buffer layers of both fcc W and beta-W2N thin films is shown in spintronic configurations, where a thin film of Fe is interposed between W or W2N layers. The reported results show that the obtained high quality W based epitaxial layers are superior template-matched buffers for epitaxial Fe layers, enabling a new class of functional spintronic heterostructures.

Cobalt triantimonide (CoSb3) skutterudites are canonical thermoelectric materials with significant potential for energy conversion. However, realizing their full potential depends on identifying and overcoming challenges related to their intrinsic properties and synthesis. This summary examines research efforts and advancements in CoSb3 and related compounds, with particular emphasis on their applicative potential since 2022. First, a concise evaluation of advancements in materials properties is conducted, including synthesis techniques and strategies to optimize the thermoelectric figure of merit. Next, a summary of recent advancements in thermoelectric devices based on CoSb3 skutterudites is presented, covering fabrication aspects, including the structural materials used, joining methods, and device performance. In conclusion, the current limitations of high-performance CoSb3based thermoelectric generators are identified, and future research directions are outlined, as they are essential to advancing this field.

This work presents a comprehensive investigation of the structural, microstructural, magnetic, and magneto-caloric properties of La0.9-xPbxNa0.1MnO3 (x = 0 and 0.1), synthesized through a flash combustion technique and subsequently pressed into pellets. Structural analysis confirms that both samples crystallize in a rhombohedral structure without detectable secondary phases or impurities. Microstructural observations reveal a homogeneous morphology in both compositions, with a noticeable grain growth effect induced by Pb doping. Magnetic measurements show a clear paramagnetic-ferromagnetic phase transition in both samples. The Curie temperature shifts from 179 K for the undoped compound to 309 K for the Pb-doped compounds. Furthermore, the magnetic entropy change and the relative cooling power increase from 3.01 J/kg.K and 184.72 J/kg for La0.9Na0.1MnO3 to 4.56 J/kg.K and 291.29 J/kg for La0.8Pb0.1Na0.1MnO3. Together, these results highlight the beneficial effect of Pb doping in the studied system for room-temperature magnetic refrigeration applications.

Proper functioning and reliability of future fusion tokamaks, including ITER, will heavily depend on the capacity to exhaust extreme heat fluxes. Tungsten (W)-based monoblocks constitute a critical core structural component. These are made of copper-chromium-zirconium (CuCrZr) cooling ducts which are joined to W using a copper (Cu) interlayer. These monoblocks must ensure efficient heat exhaustion while preserving the structural integrity under extreme operating conditions. The characterization and modelling of the interface cracking resistance of W/Cu joints is key. A single parameter interface toughness is not rich enough to encompass a wide range of stress states, especially when plasticity develops in one of the adjoining materials. The goal of this work is to develop a robust methodology to determine interface toughness and an approach to transfer data from small scale specimens to real components. A combined methodology using miniaturized three-point bending specimens and cohesive zone modelling was developed and validated, first, at room temperature. Bimaterial specimens with a notch are tested, exhibiting a ductile mode fracture with dimples on the Cu side, which suggests good delamination resistance of W/Cu joints. Cracking is accompanied by plastic dissipation. The peak strength and interface energy cohesive zone parameters are identified providing excellent correspondence between simulated and experimental load-displacement curves. Validation is made by comparing plastic zone sizes and by connecting the values to a micromechanical analysis.

This paper summarises the progress in characterisation of the CuCrZr alloy selected for the cooling pipes of European DEMO divertor achieved by several laboratories within EUROfusion in the frame of a large experimental campaign. Since the high-temperature hot radial pressing (HRP) joining procedure will modify the material properties, the CuCrZr alloy has been tested after an HRP-simulating heat treatment to represent a DEMO-relevant material. The ongoing characterization campaign is filling gaps of mechanical and thermophysical properties in the current MPH version which contains limited information on CuCrZr after the relevant thermal treatment, and helps reduce unnecessary conservatism of divertor design. Neutron irradiation campaign is ongoing which will provide high-priority mechanical properties at high dose (1-9 dpa). The obtained material properties will be compiled in the DEMO Material Property Handbooks (MPH), which will be used by the DEMO divertor design team. Most of the scheduled high-priority mechanical and thermophysical tests have been completed on non-irradiated material, their results are presented and compared to the data from the DEMO CuCrZr MPH.

We consider random sequential adsorption (RSA) of aligned squares and derive the low-coverage expansion of the availability function alpha(q), the fraction of positions accessible to an additional square, up to fourth order in the coverage q. At low coverage, the reduction of available space can be understood in terms of geometric overlap between exclusion regions created by previously deposited squares. A single square blocks a finite area; pairs of squares may have overlapping exclusion zones, reducing the total blocked area; similarly, three and four squares can share a common overlap region, leading to higher-order corrections. These contributions can be systematically accounted for through an inclusion-exclusion expansion based on the geometry of overlapping exclusion regions, with alternating signs dictated by inclusion-exclusion. The expansion terminates exactly at fourth order, since no more than four deposited squares can simultaneously overlap the exclusion region of a trial insertion. The coefficients are obtained by explicit enumeration of all such geometrically admissible configurations and are further confirmed by numerical simulations on a discrete lattice, showing agreement within statistical uncertainty.

Rapidly solidified Fe-Pd-based ferromagnetic shape memory alloy ribbons, modified with Mn or Ga additions, were produced and subjected to post-solidification heat treatments of varying duration to investigate the interplay between composition, surface characteristics, and functional properties. Surface morphology and wettability were evaluated alongside corrosion behavior, magnetic response, martensitic transformation, and in vitro cell adhesion. Corrosion performance was assessed through immersion and electrochemical techniques, providing insight into degradation kinetics. The results reveal a complex coupling between surface properties, corrosion resistance, and cell adhesion responses. Binary Fe-Pd ribbons exhibit moderately rough, homogeneous surfaces with stable Wenzel-type wetting, but limited electrochemical stability due to the reactivity of iron. Mncontaining ribbons display heterogeneous surface features and locally poor wettability after short heat treatments, leading to reduced corrosion resistance and degradation of magnetic and martensitic properties; nevertheless, they support favorable fibroblast adhesion. Prolonged annealing improves surface uniformity and wettability, while maintaining moderate corrosion resistance and good cell adhesion. Ga-containing ribbons show highly nonuniform topography combined with good hydrophilicity and the highest corrosion resistance, attributed to the formation of stable Ga-O protective products. Although corrosion effects are mitigated, partial suppression of magnetic and martensitic responses is observed. The findings highlight the potential of Fe-Pdbased ferromagnetic shape memory alloy ribbons as degradable biomedical substrates.

Rapidly solidified Fe-Pd-Ga ferromagnetic shape memory ribbons, containing 1 and 3 at. % Ga, were obtained, and annealed at 950 degrees C for 15 and 30 min. Gallium substitution destabilizes the cubic lattice but preserves ferromagnetic order; thereby, it modifies phase stability and magnetic sensitivity. The combined effects of composition and heat treatment on microstructure, martensitic transformation temperatures, transformation heat, kinetics, and magnetic-field-induced transformation shift are presented. Magnetic sensitivity is evaluated using thermomagnetic and magneto-elastic measurements, being further validated through Clausius-Clapeyron analysis. Short-time heat treatment enhances structural relaxation and significantly increases the transformation heat, whereas prolonged annealing promotes grain growth and precipitate formation without suppressing thermoelastic behavior. Increasing Ga content results in a pronounced linear increase of the martensitic transformation temperature with magnetic field, from approximately 0.6 K T-1 for 1 at. % Ga to about 1.45 K T-1 for 3 at. % Ga. The good agreement between thermomagnetic measurements and Clausius-Clapeyron analysis confirms that the transformation shift is primarily governed by intrinsic thermodynamic parameters. The smaller magneto-elastic response indicates that microstructure limits strain expression. Therefore, functional control requires tuning the balance between intrinsic thermodynamic driving forces and microstructure-dependent magneto-elastic effects through composition and heat treatment. This enables the design of thermally adaptive and magnetically programmable materials, where 3 at. % Ga composition is suitable for active magnetic control and that of 1 at. % Ga is optimized for enhanced thermal stability and precision sensing.

Tungsten (W) is the preferred plasma-facing material (PFM) for European demonstration fusion power plant (EU-DEMO) divertor target. At plasma operative conditions, such as high temperatures, high heat fluxes (HHFs), particle fluxes, and neutron irradiation, W is subject to recrystallization and to embrittlement. A proper doping of W with Potassium (K) can help improve the PFM properties. Nano K-bubbles dispersed at the grain boundaries of W can increase mechanical resistance by hindering grain growth, ultimately leading to the suppression of recrystallization. Newly developed K-doped W laminates (KdWLs) materials were produced by the National Institute of Materials Physics (NIMPs) by means of the field-assisted sintering technique (FAST). At the Special Technologies Laboratories of ENEA Frascati (ENEA-TES), water-cooled ITER-like divertor target mock-ups equipped with KdWL monoblocks were fabricated. The KdWL monoblocks were joined to CuCrZr International Thermonuclear Experimental Reactor (ITER) grade (CuCrZr-IG) cooling pipes by hot radial pressing (HRP) with an oxygen-free copper (OFC, Cu) interlayer manufactured by casting. Nondestructive examination (NDE) by ultrasonic inspection has been performed to assess the quality of the fabrication process and to analyze the structural integrity of the KdWL mock-up after HHF tests. The recent research activity is evaluating whether KdWL can represent a potential candidate armor material for a future water-cooled EU-DEMO divertor target. A dedicated qualification activity of the KdWL divertor target design is currently ongoing, and a mock-up has been produced to withstand cyclic loading up to 2000 cycles at 20 MW/m(2). In this work, new KdWL monoblocks were obtained following the optimization of the fabrication process. These monoblocks have been used to fabricate two new divertor target mock-ups to be tested, respectively, at thermal fatigue and overload.

Nowadays, paraprobiotics are considered a promising evolution of probiotics, due to their capacity to preserve or sometimes to enhance the functional properties of their counterpart probiotic viable cells. The present study investigates the production of heat-treated paraprobiotics derived from the selected probiotic Lacticaseibacillus rhamnosus MIUG BL38 strain. The paraprobiotics obtained after treatments at 82 degrees C for 5 min exhibited higher ABTS free radical scavenging activity (15.34 f 1.34%) compared to the untreated cells (10.62 f 3.18%). SEM analysis confirmed that L. rhamnosus MIUG BL38 cellular morphology was largely preserved at 74 degrees C treatment, while the temperature increase led to enhanced cell wall alterations. FT-IR results indicated the presence of specific functional groups of lipids, proteins, or carbohydrates, suggesting that structural modifications of these molecules may appear as a consequence of the cells exposure to increased temperature of 82 degrees C. Although the heat-treated paraprobiotics were characterized by changes within the cell wall molecules, their cell surface proteins (CSPs) maintained antimicrobial activity against potentially pathogenic E. coli and P. aeruginosa strains, highlighting that this property was preserved from the L. rhamnosus MIUG BL 38 strain. Further, the molecular modelling investigations focused on the SpaC pilus model of L. rhamnosus GG revealed that the thermal treatment at 82 degrees C resulted in vWFA domain loosening and important rearrangements of the arm-like structure, therefore suggesting the potential interference with mucin proteins recognition and binding. The obtained results revealed the suitability of the L. rhamnosus MIUG BL 38 strain to be used for obtaining paraprobiotics through heattreatment, with promising properties.