This study presents the design, preparation, and characterization of thirty new medium-entropy alloys (MEAs) in three systems: Al-Ti-Nb-Zr, Al-Ti-Nb-V, and Al-Ti-Nb-Hf. The hardness of the alloys ranged from 320 to 800 HV_0.3. Among the alloys studied, Al₁₅Ti₄₀Nb₃₀Zr₁₅ exhibited the highest-reversible hydrogen storage capacity (1.03 wt.%), with an H/M value of 0.68, comparable to LaNi₅, but with a reduced density (5.11 g·cm⁻³) and without rare earth elements. This study further reveals a strong correlation between hardness and hydrogen absorption/desorption; higher hardness is responsible for reduced hydrogen uptake. This finding highlights the interplay between a material’s properties and hydrogen storage behavior in MEAs, and has implications for the development of efficient hydrogen storage materials.

This study addresses the development of advanced anode materials for lithium-ion batteries by investigating the high-entropy perovskite La(Co_0.2Mn_0.2Fe_0.2Ni_0.2Cu_0.2)O₃. The material was synthesized via spray drying of aqueous metal nitrate solutions, followed by calcination at various temperatures (800 °C/1 h, 1000 °C/1 h, 1000 °C/2 h, 1100 °C/1 h) to optimize structural properties. Structural analysis using X-ray diffraction confirmed the formation of a single-phase perovskite in the sample calcined at 1100 °C for 1 h, while SEM/EDS revealed homogeneous elemental distribution. Electrochemical testing of the powders as anode materials in coin-type lithium-ion cells revealed a trend of slightly increasing capacity over 150 cycles, with capacity ultimately reaching 617 mAh g⁻¹, indicating progressive electrochemical activation. Although the samples share the same composition, variations in calcination conditions resulted in differences in capacity and cycling behavior. These results demonstrate that synthesis parameters critically influence the electrochemical performance of high-entropy perovskites. The findings suggest that such materials have potential as stable anodes for next-generation lithium-ion batteries, contributing to improved durability and efficiency in energy-storage technologies.

This study investigates the thermoelectric properties of Se-rich β-Ag₂Se synthesized via a mechanochemical method followed by spark plasma sintering (SPS) in less than 30 min of the total reaction time. Importantly, only a short 10 min milling process followed by appropriate SPS was enough to produce single-phase Ag₂Se_1+x samples with varying selenium content (where x = 0, 0.01, 0.02, 0.04). The introduction of excess selenium significantly influenced the thermoelectric performance, optimizing the carrier concentration during synthesis and resulting in substantial thermoelectric improvements. The sample with nominal composition Ag₂Se_1.01 exhibited a high dimensionless figure-of-merit (ZT) >0.9 at 385 K, which is nearly six times higher than the reference sample (β-Ag₂Se). Our findings bring valuable insight into the technology of optimization of thermoelectric characteristics of Se-rich β-Ag₂Se, highlighting its potential for applications in thermoelectric devices. The study demonstrates the energetically efficient and environmental advantage of our mechanochemical route to produce Se-rich β-Ag₂Se, providing a solvent-free and commercially viable alternative synthesis for energy (thermoelectric and solar energy).

This study introduces an innovative approach to alloy design by experimentally validating the semi-empirical concept of Griessen and Driessen, which predicts the hydrogen affinity of solid solutions. The work focuses on designing and synthesizing four equiatomic high-entropy alloys (HEAs) with compositions tailored to exhibit highly endothermic enthalpies of solution and formation, resulting in resistance to hydrogen absorption. Unlike conventional studies that prioritize hydrogen storage capacity, this research uniquely targets alloys optimized for minimal hydrogen interaction, addressing critical needs in hydrogen storage and transportation technologies prone to hydrogen embrittlement. Experimental results confirm the negligible hydrogen absorption of these alloys, with a maximum of 0.23 wt.% (H/M = 0.13) at 2 MPa and 175 °C. This study not only demonstrates the applicability of a theoretical model to guide alloy design but also highlights the potential of these materials for low-pressure hydrogen storage systems, where mechanical integrity and resistance to hydrogen degradation are paramount. The findings bridge the gap between theoretical predictions and practical applications, offering a novel perspective on alloy development for hydrogen-related technologies.

The thermoelectric properties of skinnerite Cu₃SbS₃ and wittichenite Cu₃BiS₃ prepared by mechanochemical synthesis in a planetary ball mill from elemental precursors were investigated for the first time. X-ray diffraction (XRD) analysis of skinnerite after heat treatment revealed not only the presence of monoclinic skinnerite phase but also the presence of tetrahedrite phases. XRD analysis of wittichenite after both heat treatment and spark plasma sintering (SPS) revealed the presence of only the prepared orthorhombic wittichenite, whereas, in the case of skinnerite, not only skinnerite but also tetrahedrite is present after SPS treatment. The thermal stability of mechanochemically synthesized Cu₃SbS₃ and Cu₃BiS₃ samples was investigated by thermal analysis, which confirmed that Cu₃SbS₃ is thermally stable up to 604 K and Cu₃BiS₃ up to 550 K, respectively. Thermoelectric (TE) potential was evaluated by measuring the Seebeck coefficient, electrical and thermal conductivity, and figure of merit ZT. The performed thermoelectric (TE) measurements revealed a figure of merit ZT of 0.69 and 0.09 at 575 K for pristine skinnerite and wittichenite, respectively, sintered by SPS. The combination of mechanosynthesis followed by SPS allows for the preparation of materials that display a promising thermoelectric response. This approach opens up new possibilities for enhancing the thermoelectric properties of materials, which could have significant implications for various applications, such as energy conversion and waste heat recovery. Further research in this area is necessary to fully explore and exploit the potential of these materials for thermoelectric applications.

This work studied the thermal stability, electrical, and thermoelectrical properties of copper(I) selenide, Cu₂Se synthesized by high-energy milling in a planetary ball mill. The phase composition was investigated by X-ray powder diffraction analysis and scanning electron microscopy. The conversion of the precursors during mechanochemical synthesis and the stability of the product was monitored by thermal analysis. The dependence of electrical properties on the product porosity was observed. For the densification of Cu₂Se, the method of spark plasma sintering was applied to prepare suitable samples for thermoelectric characterization. High-temperature thermoelectric properties of synthetic Cu₂Se were compared to its natural analogue-mineral berzelianite in terms of its potential application in energy conversion. Based on the results a relatively high figure-of-merit, ZT parameter (~ 1.15, T = 770 K) was obtained for undoped Cu₂Se, prepared by rapid mechanochemical reaction (5 min). Cyclic voltammetry measurements of Na/NaClO₄/Cu₂Se cell implied that mechanochemically synthesized Cu₂Se could be used as a promising intercalation electrode for sodium-ion batteries.