National Institute Of Materials Physics - Romania

Within the framework of the EUROfusion Consortium, the Characterization of armour, heat sinks materials and joints sub-project of the Work Package Material (WP-MAT) has been dedicated to the development of different tungsten (W) monoblock mock-ups equipped with advanced materials for divertor target applications in the EUDEMO fusion reactor. Assessing the status of the relevant joining interfaces of these mock-ups, not only after fabrication but throughout the whole component lifetime, plays a key role in the qualification process. At the ENEA Special Technologies Laboratory (TES), a number of facilities have been built to perform non-destructive inspections of plasma-facing components for fusion applications by ultrasonic testing (UT). The present work reports on the results of the UT inspections assessing the structural integrity of the relevant joining interfaces of three small-scale mock-ups provided with advanced W armour materials, specifically W-matrix with W2C inclusions consolidated by Spark Plasma Sintering (SPS), K-doped rolled W and K-doped laminated W. The UT examinations are carried out after fabrication and after the high heat flux tests (HHFT) at the neutral beam facility GLADIS. All results confirm the high-quality joining achieved by HIP and HRP. During the HHF tests of mock-ups, after a few hundred HHFT cycles defects are detected at the joining interfaces, due to debonding, delamination and W material cracks mainly affecting the loaded zone. The ultrasonic pulse-echo technique provides not only the size and position of the defects in the plane orthogonal to the ultrasonic beam, but also their depth in the material. During the analysis, the probe is inserted inside the pipe and the mock-up is examined in a cylindrical configuration. The coupling medium (demineralized water) is poured only inside the pipe. The main inspection parameters and the piezoelectric probes are chosen to obtain the maximum resolution in accordance with the thickness and joining interfaces to be analyzed.

In recent decades, magnetic hyperthermia (MH) has gained considerable scientific interest in cancer treatment due to its ability to heat tumor tissues deeply localized inside the body. Functionalizing magnetic nanoparticles (MNPs) with vector molecules via specific organic molecules that coat the particle surface has enabled targeting particular tissues, thereby increasing the specificity of MH. MH relies on applying radiofrequency (RF) magnetic fields to a magnetic nanoparticle distribution injected in a tumor tissue. The RF field energy is converted into thermal energy through specific relaxation mechanisms and magnetic hysteresis-driven processes. This increases the tumor tissue temperature over the physiological threshold, triggering a series of cellular apoptosis processes. Additionally, the mechanical effects of low-frequency AC fields on anisotropic MNPs have been shown to be highly effective in disrupting the functional cellular components. From the macroscopic perspective, a crucial parameter measuring the efficiency of magnetic nanoparticle systems in MH is the specific absorption rate (SAR). This parameter is experimentally evaluated by different calorimetric and magnetic techniques and methodologies, which have specific drawbacks and may induce significant errors. From a microscopic perspective, MH relies on localized thermal and kinetic effects in the nanoparticle proximity environment. Studying MH at the cellular level has become a focused research topic in the last decade. In the context of these two perspectives, inevitable questions arise: could the thermal and kinetic effects exhibited at the cellular scale be linked by the macroscopic SAR parameter, or should we find new formulas for quantifying them? The present work offers a general perspective of MH, highlighting the experimental pitfalls encountered in SAR evaluation and motivating the necessity of standardizing the devices and protocols involved. It also discusses the challenges that arise in MH performance evaluation at the cellular level.

Nuclear fusion is a promising energy source. The International Thermonuclear Experimental Reactor aims to study the feasibility of tokamak-type reactors and test technologies and materials for commercial use. One major challenge is developing materials for the reactor's divertor, which supports high thermal flux. Tungsten was chosen as the plasma-facing material, while a CuCrZr alloy will be used in the cooling pipes. However, the gradient between the working temperatures of these materials requires the use of a thermal barrier interlayer between them. To this end, refractory high-entropy (CrFeTiTa)70W30 and VFeTiTaW alloys were prepared by mechanical alloying and sintering, and their thermal and irradiation resistance was evaluated. Both alloys showed phase growth after annealing at 1100 degrees C for 8 days, being more pronounced for higher temperatures (1300 degrees C and 1500 degrees C). The VFeTiTaW alloy presented greater phase growth, suggesting lower microstructural stability, however, no new phases were formed. Both (as-sintered) alloys were irradiated with Ar+ (150 keV) with a fluence of 2.4 x 1020 at/m2, as well as He+ (10 keV) and D+ (5 keV) both with a fluence of 5 x 1021 at/m2. The morphology of the surface of both samples was analyzed before and after irradiation showing no severe morphologic changes, indicating high irradiation resistance. Additionally, the VFeTiTaW alloy presented a lower deuterium retention (8.58%) when compared to (CrFeTiTa)70W30 alloy (14.41%).

A multiphase high-entropy diboride (Ti0.25Ta0.25Hf0.25Zr0.25)B2 is obtained by spark plasma sintering from a mixture of single-metal diborides. The as-prepared material at the microscale can be defined as a composite where grains of a Ta-rich/Ti-poor complex diboride phase are the reinforcement and grains of Ta-poor/Ti-rich complex diboride are the matrix. However, at the nanoscale, the grains are heterogeneous, composed of regions with a multitude of complex diboride compositions. The interface between nanoregions is compositionally graded and has an irregular shape. The four-metal diboride shows a deformation-resistant mechanism under bending load. A strengthening process is active, increasing the room temperature bending strength (326 MPa) by approximate to 50% at 1800 degrees C (488 MPa). A ductile behavior with a deformation strain of approximate to 7.5% is observed at 2000 degrees C while bending strength (407 MPa) is approximate to 25% above the value at room temperature. At 2000 degrees C, observation of dislocations propagating from one compositional nanoregion to another and with a different density suggests dislocation contribution, first of all, to plasticity. The peculiar heterogeneity of this material at nano- and microscales is considered the reason for the remarkable mechanical response to bending load at different temperatures.

The paper presents the features of the magnetization decay of proton-irradiated MgB2 bulk samples. Irradiation was performed with protons of energies between 8.6 and 15.07 MeV at different fluences. The creep activation energy is sensitive to the ratio between proton range and sample thickness. Experimental data show that the creep exponents are different from the theoretical predictions. When the proton range is shorter than the sample thickness (protons of 8.6 MeV), the thermomagnetic instabilities are strongly emphasized and affect the creep behavior.

A methodology for the quantitative estimation of the drug loading of iron oxide-based magnetic nanoparticles by corroborating magnetometry and M & ouml;ssbauer spectroscopy investigations is reported. The proposed methodology is exemplified in the case of two series of nanoparticles, namely Fe3O4 nanoparticles covered with citric acid molecules and further functionalized with doxorubicin, and Fe3O4 nanoparticles covered with L-Cysteine molecules and further functionalized with doxorubicin. The general idea of the proposed methodology is to probe the real magnetic structure of the magnetic core via low-temperature M & ouml;ssbauer spectroscopy for the correct estimation of the spontaneous magnetization of the magnetic core. It subsequently uses the ratio between the spontaneous magnetization of the covered nanoparticles and that of the magnetic core for the reliable and nondestructive evaluation of the nanoparticle loading by organic molecules. Although the methodology is exemplified in the case of magnetite-based nanoparticles, it can be successfully considered for a large class of medicine-loaded Fe-containing magnetic nanoparticles where 57Fe M & ouml;ssbauer spectroscopy can be applied.

Tungsten-copper (W-Cu) composites have a wide range of engineering applications, from arc-resistant electrodes and high-voltage electrical contacts to heat sinks for integrated circuits and plasma-facing components for fusion reactors. They combine high corrosion and erosion resistance, very good thermal and electrical conductivity, low thermal expansion, with good mechanical properties. However, the fabrication of such materials is limited in terms of shape complexity and the internal distribution of the individual phases. Furthermore, the dissimilar thermo-mechanical properties (melting temperature, thermal conductivity, coefficient of thermal expansion) of the constituent phases impose severe constraints on the fabrication and use of W-Cu composites. To overcome the challenges of component design and enable greater freedom in terms of composition, W-Cu composites were produced by a combination of additive manufacturing and liquid-melt infiltration (LMI). Porous W-lattice structures were manufactured by laser powder-bed fusion (LPBF) followed by infiltration with molten Cu. A series of composites was produced with Cu contents from 3 to 75 vol% and evaluated in terms of thermal, electrical, and mechanical properties. The LPBF-LMI W-Cu composites exhibited comparable thermo-mechanical properties to W-Cu materials manufactured using powder-metallurgical processing, but with an expanded composition range and shape complexity. Lower thermal expansion coefficients (4.5-5.8 x 10-6 K- 1) and an improved thermal stability of the Young's modulus, only a 27-33 GPa decline in the range 27-827 degrees C, were observed for all the compositions, which was ascribed to the W-phase connectivity in all the W-Cu composites, independent of the volume fraction of Cu.

In this work, three methods for the synthesis of composites based on poly(ortho-toluidine) (POT) and WS2 are reported: (a) the solid-state interaction (SSI) of POT with WS2 nanoparticles (NPs); (b) the in situ chemical polymerization (ICP) of ortho-toluidine (OT); and (c) the electrochemical polymerization (ECP) of OT. The preparation of WS2 sheets was performed by the ball milling of the WS2 NPs followed by ultrasonication in the solvent N,N'-dimethyl formamide. During the synthesis of the POT/WS2 composites by SSI and ICP, an additional exfoliation of the WS2 NPs was reported. In this work, we demonstrated the following: (a) the ICP method leads to POT/WS2 composites, which contain repeating units of POT in the leucoemeraldine salt (LS) state, while (b) the ECP method leads to POT/WS2 composites, which contain repeating units of POT in the emeraldine salt (ES) state. Capacitances equal to 123.5, 465.76, and 751.6 mF cm-2 in the cases of POT-ES/WS2 composites, synthesized by SSI, ICP, and ECP, respectively, were reported.

Lithium-ion batteries (LIBs) are fundamental to modern technology, powering everything from portable electronics to electric vehicles and large-scale energy storage systems. As their use expands across various industries, ensuring the reliability and safety of these batteries becomes paramount. This review explores the multifaceted aspects of LIB reliability, highlighting recent advancements and ongoing challenges. The importance of safety has been underscored by numerous incidents, such as the well-known smartphone battery explosions and more than 10,000 fires a year at facilities throughout Australia, both linked to LIB failures. These events emphasize the need for robust reliability and safety measures to ensure consistent performance and longevity. Factors like battery chemistry, design, manufacturing, and operating conditions can all influence the reliability of LIBs. Despite their widespread use, the mechanisms of failure, failure rates, and consequences of LIB failures are still not well understood, raising significant safety concerns. Current reliability assessment techniques include experimental methods, computational models, and data-driven approaches. Emerging trends, such as advanced characterization techniques and standardized testing protocols, advocate for improved practices to enhance the reliability and safety of LIBs across all applications.

This study investigates polycrystalline samples of TiFe2-xRexSn (with x = {0, 0.02, 0.04, 0.06, 0.2}) synthesized using conventional arc-melting and spark plasma sintering. Structural and morphological analysis shows that low Re substitutions result in good phase purity with minor traces of secondary phases, while higher Re content leads to the segregation of additional phases. The magnetism and electrical resistivity of the samples are affected by inherent Fe-Ti atomic disorder, with the effects of secondary phases becoming more prominent in the samples with higher Re content. The Seebeck coefficient values increase only for TiFe1.98Re0.02Sn, while the power factor increases for x = {0, 0.02, 0.04}, reaching maximal values for x = 0.02 at similar to 300 K and x = 0.04 at similar to 325 K, i.e., (2.22 +/- 0.2) x 10(-4) Wm(-1) K-2. The thermal conductivity of the samples increases with x, resulting in modest values of the figure of merit, with the maximum achieved for x = 0.02 at 325 K, i.e., 0.015 +/- 0.002. (c) The Author(s) 2024