National Institute Of Materials Physics - Romania

Non-volatile electronic memory elements are very attractive for applications, not only for information storage but also in logic circuits, sensing devices and neuromorphic computing. Here, a ferroelectric film of guanine nucleobase is used in a resistive memory junction sandwiched between two different ferromagnetic films of Co and CoCr alloys. The magnetic films have an inplane easy axis of magnetization and different coercive fields whereas the guanine film ensures a very long spin transport length, at 100 K. The non-volatile resistance states of the multiferroic spintronic junction with two-terminals are manipulated by a combined action of small external magnetic and electric fields. Thus, the magnetic field controls the relative orientation of the magnetization of the metallic ferromagnetic electrodes, that leads to different magnetoresistance states. The orientation and the magnitude of the electric field controls the orientation of the polarization of the guanine ferroelectric barrier, that leads to different electroresistance states, respectively. Moreover, we have observed a strong interfacial coupling of the two parameters. Consequently, positive and negative magnetoresistance hysteresis loops corresponding to spin rectification effects and non-hysteretic (erased) resistive states are manipulated with the electric field by switching the orientation of the electrical polarization of the organic ferroelectric.

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.

By experiment we evaluated the longitudinal magnetostriction on cylindrical samples of MnZn ferrite. Starting from the idea that the magnetostriction phenomenon is closely related to the magnetization phenomenon of the ferromagnetic sample, by plotting the magnetostriction curve it is possible to extract the magnetization curve of the ferromagnetic material and to evaluate the saturation magnetization of the material and the demagnetizing factor of the sample. At the same time, the paper suggests a way to study the dynamics of the movement of the magnetic domain walls in the sample, by examining the resonance curve at each point on the magnetization curve.

This study investigates the effects of neutron irradiation on tungsten (W) and copper-chromium-zirconium (CuCrZr) joints under conditions mimicking the high neutron flux environment of a tokamak fusion reactor. Samples of W/CuCrZr joints were subjected to irradiation in the Belgian Reactor 2 (BR2) nuclear reactor at SCK CEN (Belgian Nuclear Research Centre) to simulate the intense neutron exposure characteristic for International Thermonuclear Experimental Reactor (ITER) and DEMOnstration power plant reactor (DEMO) operations. The primary objective was to evaluate changes in the mechanical properties and microstructure of these materials, which are critical for their potential use in plasma-facing components. It is revealed that a significant reduction in tensile elongation of the joint, indicating some degree of embrittlement, is observed after the irradiation. Importantly, this effect is independent of the irradiation temperature. Possible physical reasons for the observed phenomenon are discussed.

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.

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.

Expression of concern for 'Iron oxide magnetic nanoparticles with versatile surface functions based on dopamine anchors' by Mykola Mazur et al., Nanoscale, 2013, 5, 2692-2702, https://doi.org/10.1039/C3NR33506B.

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/mK at RT to 28 W/mK 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/mK at 600 degrees C) and much lower than for CuCrZr-IG (similar to 354 W/mK 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.

The synthesis of polycrystalline TiFe2Sn samples by a route including arc melting and spark plasma sintering with Hf, Y, and In substitutions at the Ti and Sn sites is investigated. For a reduced amount of substitution, around 2 at%, the samples are single phase, while for increased amounts, secondary phases segregate. As is characteristic of these compounds, the Fe-Ti atomic disorder generates a weak ferromagnetic ordering, which is also influenced by the type of substitutional atoms and the secondary phases in the samples with a higher Hf content. The Seebeck coefficient values show an increase for Ti0.98Hf0.02Fe2Sn and for samples with an adjusted Sn content, resulting in slightly increased power factor values. These values reach a maximum for Ti0.98Hf0.02Fe2Sn at approximately 300 K and for TiFe2Sn1.05 at approximately 325 K, namely, 2.69 x 10(-)(4) Wm(-1)K(-2) and 2.52 x 10(-)(4) Wm(-1)K(-2), respectively. The thermal conductivity of all the samples with substitutions increases with respect to the pristine sample. The highest figure of merit value of 0.016 is also obtained for Ti0.98Hf0.02Fe2Sn at 325 K.