Publications

Conversion of hazardous vanadium spent catalysts (VSCs) to high added value vanadium-based materials is an effective solution for environmental remediation as well as cost-effective energy storage applications. In the present work, we introduce a new green hydrometallurgical process based on a novel synergistic sulfuric acid-hydrazine monohydrate (H2SO4-N2H4 & centerdot;H2O) leaching system, achieving a high vanadium extraction of 97.8%. The purified vanadyl sulfate solution (99.96%) of the subsequent solvent extraction was converted into V2O5 and utilized for the production of Na3V2(PO4)2F3@C (NVPF@C) cathode material via a solid-state approach for SIB application. The NVPF@C electrodes exhibited an interesting electrochemical performance, delivering 115 mAh g-1 at 0.2C and retaining 89% capacity after 100 cycles at 1C, with remarkable rate capability. Economic and environmental assessment indicated savings of 72.9% in vanadium pentoxide cost as well as a range of 68.6-96.7% in greenhouse gas emission reduction compared with conventional leaching systems. This study highlights the feasibility of closing the loop for vanadium resources, offering a scalable and environmentally friendly route to battery-grade precursors. The approach not only validates the use of recycled vanadium in high-performance sodium-ion batteries but also emphasizes the integration of circular economy principles and sustainable practices in next-generation energy storage technologies.

Magnesium and zinc are important additives or substituents in melt-quenched Na2O-CaO-SiO2-P2O5 bioactive glasses, due to their beneficial influence on glass stability and processability. They modify the dissolution kinetics of these glasses and impart favorable biological properties and functions to them. For rational bioactive glass design, it is essential to understand the local environments and distributions of these ions. While diffraction studies suggest MgO and ZnO to be close-to-four-coordinate in silicate glasses, their structural roles in the network are still under debate. Traditionally these oxides have been viewed as network modifiers, converting Si-O-Si linkages to anionic non-bridging oxygen atoms, whose charges are compensated by the divalent cations. It has been suggested that MgO4/2|(2-) or ZnO4/2|(2-) network-forming units (NFUs) may be present, forming Mg-O-Si or Zn-O-Si linkages. If such units are formed, they would attract modifier cations for charge compensation, which would in turn result in an increased degree of polymerization of the silicate species, the main network-forming component. This study explores the roles of MgO and ZnO in bioactive glasses with approximate composition 50SiO(2)-(50-x)[MO,M'O-2]-xP(2)O(5) in mol% (2 <= x <= 6), where M = Ca, Sr, Mg, Zn; M' = Na, K. Quantitative estimates of the various silicate and phosphate NFUs were obtained from Si-29 and P-31 solid-state nuclear magnetic resonance (NMR) spectroscopic techniques and molecular dynamics (MD) simulations, allowing the determination of the degree of network polymerization in terms of the average Si and P connectivities (-values). Both NMR spectroscopy and MD studies consistently revealed that the extent of Si polymerization increases, as expected, with P2O5 addition, reflecting the well-documented preferential cation attraction by the phosphate species. On the other hand, data obtained from a set of comparative samples containing either Mg, Zn, or a mixture of both showed no significant changes in the degree of silicate network polymerization. This result strongly supports a network-modifying role of both magnesium and zinc oxide, as suggested by previous works.

Introduction This study examines the effect of multi-walled carbon nanotube (MWCNT) loading on the dielectric behavior and triboelectric performance of polysiloxane (PS)-based nanocomposites for high-efficiency triboelectric nanogenerators (TENGs).Methods Flexible PS/MWCNT films were fabricated using the doctor blading method and characterized by Raman spectroscopy and scanning electron microscopy (SEM). Broadband dielectric spectroscopy was employed to analyze frequency-dependent permittivity, interfacial polarization, and dielectric loss. TENGs were assembled in a vertical contact-separation mode using nylon as the positive triboelectric layer and evaluated under controlled temperature and humidity. Statistical error analysis (n = 3) was applied to ensure quantitative reliability.Results A co-optimal MWCNT concentration of 0.03-0.05 wt% enhanced dielectric permittivity and interfacial charge trapping, improving triboelectric output while keeping conductive losses low. Higher loadings led to nanotube aggregation and increased dielectric loss, degrading device performance.Discussion/Conclusion The study establishes a quantitative correlation between dielectric spectroscopy and triboelectric output, providing mechanistic insight into performance enhancement and degradation. This framework offers practical guidelines for designing PS-based nanocomposite TENGs for wearable electronics, self-powered sensors, and portable energy-harvesting applications.

Materials capable of withstanding extreme environments open promising opportunities for nuclear fusion reactors. In this study, equiatomic CrFeTaVW and CrFeTiVW high-entropy alloys are investigated as interlayer materials between W and CuCrZr. Monte Carlo and Molecular Dynamics simulations predicted a bcc-type structure for both systems. Additionally, the Monte Carlo simulation predicts lower potential energy and a more stable structure for both systems than Molecular Dynamics. For CrFeTaVW, the chemical segregation values are lower in MC than in the MD simulation, whereas for CrFeTiVW, the opposite trend is observed, with MC indicating stronger segregation values. After simulation, the high-entropy alloys were prepared by planetary ball milling, consolidated by spark plasma sintering, and analyzed using X-ray diffraction, scanning electron microscopy, and thermal diffusivity. The experimental results for the milled powders confirmed the formation of a bcc structure in both alloys. The consolidated material revealed a bcc-type structure and an Fe2Ta Laves phase for the CrFeTaVW HEA, while the CrFeTiVW HEA exhibits two different bcc-type structures. The values of CrFeTaVW and CrFeTiVW thermal diffusivity are between 3.5 and 7 mm2/s, which is consistent with the expected values for high-entropy alloys. Overall, the findings indicate that these HEAs have promising properties that can be used in extreme environments.

This paper reports a method for separating the constituents of a cathode containing a composite of the type polydiphenylamine (PDPA)/multi-walled carbon nanotube grafted with carboxyl groups (PDPA/MWCNT-COOH-1) as active material in end-of-life rechargeable lithium-ion batteries (RLIB) and their reuse as active materials in the field of other energy storage devices. The materials recovered from lithium battery cathodes are characterized by FTIR spectroscopy, Raman scattering, surface-enhanced Raman scattering (SERS), and X-ray diffraction. The use of the PDPA/MWCNT-COOH-1 composite as active material in the development of new energy storage devices, such as symmetric supercapacitors, is also reported. The performance comparison of the recycled composite material (PDPA/MWCNT-COOH-1 and MWCNT-COOH) with the one synthesized from pure chemical compounds (PDPA/MWCNT-COOH-2) is shown. Values of the capacitance of symmetrical supercapacitors, having as electrode materials the composites of the type of a mixture of PDPA/MWCNT-COOH-1 and MWCNT-COOH, as well as PDPA/MWCNT-COOH-2, are equal to 136.6 mF cm-2 and 112.59 mF cm-2. Increasing the concentration of the PDPA/MWCNT-COOH-2 active material in the electrode mass from 80 wt% to 84 wt% led to variations in the capacitance values of the symmetrical supercapacitors from 112.59 mF cm-2 to 145.5 mF cm-2.

We report a technique for generating narrowband, high-frequency electrical signals using spintronic terahertz emitters (STEs) integrated onto coplanar waveguides (CPWs). Conventional STE operation typically yields ultrashort, broadband pulses spanning tens of terahertz. Our method employs multiple STEs positioned at precisely defined intervals along the CPW to produce a burst like signal, where the inter-emitter spacing determines the time delay between pulses, thus the fundamental burst frequency, which theoretically can be tuned across the STE bandwidth. Meander-shaped CPW geometries are used to enable compact integration and uniform optical excitation. First test devices demonstrate electrical signals up to 30 GHz with a bandwidth of 4.7 GHz corresponding to a quality factor of 6.38.

HfZrO2(HZO) is a promising ferroelectric material compatible with CMOS technology, retaining functionality at nanometer-scale thicknesses. Its ferroelectricity arises from metastable polar phases-orthorhombic (Pca21) and rhombohedral (R3m)-coexisting with the thermodynamically stable, non-polar monoclinic phase (P21/c). Accurate quantification of these coexisting phases is essential for optimizing device performance. Here, we use first-principles calculations to estimate core-level shifts in the O 1s X-ray photoelectron spectroscopy (XPS) peak, revealing a distinct, up to 0.84 eV higher binding energy component for oxygen atoms in the polar sublattice compared to those in non-polar environments. These shifts incorporate both initial and final state effects in photoemission. Experimental validation through X-ray diffraction (XRD) and XPS on HZO films with varying phase composition confirms our predictions. Our findings provide a clear, spectroscopically accessible fingerprint to distinguish polar and non-polar phases in HZO via O 1s XPS analysis, offering a practical tool for phase quantification and enabling targeted integration of ferroelectricity in advanced nanoelectronic devices.

Palladium diselenide (PdSe2) is a two-dimensional (2D) transition metal dichalcogenide van der Waals material that exhibits a unique wrinkled pentagonal structure that results in strong anisotropic layer-dependent properties. Owing to these unique properties the material has a great potential for applications in electronic, optoelectronic, photonic and thermoelectric devices. Here, we study the electronic properties of monolayer (ML) PdSe2 in a Schottky junction by contacting the material with a tungsten scanning tunneling microscope (STM) tip. The STM-induced lifting of the 2D layer leads to structural warping of the top layer, which causes significant changes in the electronic properties of PdSe2 as well as the electrostatic potential across the junction. We compare the STM-determined work function of the warped PdSe2 ML with the work function of bulk PdSe2 as obtained by Kelvin probe force microscopy and electronic structure obtained by synchrotron-based angle-resolved photoemission spectroscopy, and x-ray photoelectron spectroscopy.

Transition-metal phosphorus trichalcogenides are a class of van der Waals materials having the potential to transform a diverse range of fields, from electronics to energy storage. Among these, nickel phosphorous trisulphide (NiPS3) is particularly interesting with its strongly correlated zig-zag antiferromagnetic insulating state below the Neel temperature, which is, of about 150 K. This study delves into the electronic properties of NiPS3 above the transition temperature, using state-of-the-art synchrotron-based techniques, including x-ray absorption spectroscopy (XAS) combined with x-ray linear dichroism (XLD) and angle-resolved photoemission spectroscopy (ARPES), in order to probe the chemical state and the momentum-resolved band structure. The experimental results, corroborated by density functional theory (DFT) calculations, unveil orbital asymmetries linked to the crystallographic lattice and the orbital content of the electronic structure, which presents a nearly flat band close to the Fermi level. Moreover, the calculated dipole matrix elements reproduce well the polarization dependence observed in valence band ARPES. Our data reveal details on the electronic properties of NiPS3, which could lead to innovative solutions and applications in areas such as advanced computing, photo-electrochemical devices, and photodetectors.