In this study, we modified Ni based electrodes with MXene and MXene-based composite catalysts for water splitting. The MXene based catalyst exhibited excellent electrochemical surface area (ECSA) of 1840 cm 2 , highlighting its abundant active sites. To further enhance catalytic activity, MXene was modified with graphene oxide (GO) and carbon black (CB), which significantly reduced the overpotential from 300 mV to 196 mV at 10 mA cm −2 and improved the reaction kinetics, as evidenced by a low Tafel slope of 96.35 mV dec −1 . Moreover, the MXene–GO–CB composite demonstrated outstanding long-term durability, maintaining stable operation for 50 h at 100 mA cm −2 with only a 34 mV increase in overpotential at 10 mA cm −2 . These results confirm that the synergistic combination of MXene with GO and CB yields a highly active and durable electrocatalyst, offering strong potential for practical water electrolysis applications.
The paper presents the first comparative study of the microstructure and mechanical properties of gadolinium zirconate ceramics produced by spark plasma sintering of powders obtained using hydroxide precursors synthesized with and without mechanical activation. The initial precursor was prepared via reverse coprecipitation of hydroxides. Mechanical activation of the precursor was performed in an AGO-2 planetary mill at a centrifugal acceleration of 20 g for 30 min. X-ray phase analysis revealed that the resulting ceramics were nanocrystalline. The ceramics produced from the mechanically activated precursor demonstrated superior mechanical properties, including higher microhardness and Young’s modulus, compared to those produced from the non-activated precursor.
In this article, the Cauchy problem in a half-plane is studied for a fourth-order inhomogeneous equation with a fractional derivative in the Caputo sense. The uniqueness of the solution is demonstrated using the Laplace transform. In constructing the solution, partial solutions expressed in terms of Wright functions are first found. Green’s functions are then constructed using these partial solutions. The solution is constructed explicitly using the Green function. An explicit form of the fundamental solution is also obtained.
We study three-particle Schrodinger operators on the two-dimensional lattice Z(2) and show that a critical mass ratio gamma(c) approximate to 2.75194 governs the existence of a bound trimer in the fermionic 2 + 1 configuration (two identical fermions and a third particle). For gamma < gamma(c) there is a topological prohibition (Pauli suppression) of a three-body bound state, whereas for gamma > gamma(c) a doubly degenerate eigenvalue emerges below the essential spectrum with the strong-coupling asymptotics z(gamma, lambda) = -lambda+e(0)(gamma)+O(lambda(-1)). Within a unified framework based on the Birman-Schwinger principle and strong-coupling asymptotic analysis, we compare this behaviour with the bosonic case of three identical particles, where two bound states exist below the essential spectrum and the ground-state energy satisfies z(1)(s) (& micro;) = -3 & micro; + C-2 + O(& micro;(-1)). The resulting second-order phase transition with respect to the mass ratio gamma is relevant for the design of experiments on fermionic trimers in optical lattices and for modelling excitonic complexes and defect-bound states in two-dimensional nanomaterials, where the critical value gamma(c) serves as a design guideline for the observability of three-body bound states. We also outline a modified three-particle lattice model with two competing interaction channels, for which the Birman-Schwinger analysis naturally leads to a Landau-type scenario of a first-order phase transition in the space of trimer bound states. In the bosonic case we prove a strong-coupling theorem describing the existence and asymptotics of trimer bound states, while in the fermionic 2+1 case we establish a spectral phase-transition theorem that identifies an explicit critical mass ratio gamma(c) separating the trimer and non-trimer regimes.
The elastic properties and mechanical characteristics of Ti-Nb22-Zr6 based alloys were calculated using the exact muffin-tin orbital method with the coherent potential approximation. Alloying by metals such as Hf, Mg and their combination were considered, and their concentration did not exceed 5 at.%. It was shown that addition of Hf and Mg leads to a decrease in Young's modulus due to both size effect and electronic factor. The calculated Young's modulus for the ternary Ti-Nb22-Zr6 alloy (70.1 GPa) is found in good agreement with experimental one (70 GPa). The smallest value of Young's modulus was calculated for the Ti-Nb22-Zr6-Hf5-Mg2.5 alloy, achieving 57 GPa. Further increase in Mg concentration leads to a negative C ' and alloy destabilization. Additionally, alloying of the Ti-Nb22-Zr6 alloy results in a decrease in hardness, fracture toughness, but brittleness index is increased.
In this paper, we investigate weakly periodic p-adic quasi Gibbs measures for the q-state Potts model on the Cayley tree of order k. Furthermore, we demonstrate that for all q >= 3 and k >= 2, there exist a prime number p and a parameter theta that guarantee the occurrence of a phase transition.
We study the Schro & uml;dinger operators H lambda & micro;(K) that model a two-fermion system on the threedimensional lattice Z3, where total quasimomentum is fixed at K E T3, and the particles interact through nearest-and next-nearest-neighbor couplings with strengths lambda, & micro; E R. For K = 0, we establish that H lambda & micro;(0) admits reducing invariant subspace whose restriction depends solely on the parameter & micro; E R. This & micro; parameter line contains two critical points corresponding to the lower and upper spectral thresholds; at each of these points, the Fredholm determinant of the restricted operator vanishes. Each of these critical points divides the parameter line into two infinite intervals, where the number of eigenvalues lying below (or above) the essential spectrum remains constant. Depending on & micro;, the corresponding reduced operator has exactly one discrete eigenvalue, located either below the bottom or above the top of the essential spectrum. Moreover, we derive a lower bound on the number of discrete eigenvalues of H lambda & micro;(K) for all K E T3.
A comparative study of the redox behaviour of nanocrystalline isostructural ACe 2 (PO 4 ) 3 (A = NH + 4 , K + , Rb + ) double ceric phosphates was performed. It has been established that with respect to alkylperoxyl radicals or hydrogen peroxide as reactive oxygen species, all the double ceric phosphates acted as antioxidants or prooxidants, respectively. The antioxidant activity towards alkylperoxyl radicals was found to be the higher for the phosphates containing potassium or rubidium. Notably, for KCe 2 (PO 4 ) 3 and RbCe 2 (PO 4 ) 3 an inverse dependence of catalytic activity on concentration in the reaction with H 2 O 2 was found, in contrast to NH 4 Ce 2 (PO 4 ) 3 . The redox behaviour of nanoscale cerium dioxide used for comparison was similar to that of ammonium ceric phosphate, but significantly lower in absolute values. This was explained by the suppressive effect of phosphate anions presented in the buffer solutions.
A thermodynamic analysis of hydroxide transformations in the Mg1-xNix(OH)2-SiO2-H2O system during the hydrothermal synthesis of nanotubular particles with a chrysotile structure has revealed the decisive role of the dehydration of initial reagents and the subsequent re-formation of hydroxides during hydrothermal treatment of reagents on the composition and morphological parameters of the target product. Depending on the composition of the hydroxide reagent and the T-P conditions in the reaction zone, three regions have been identified where the formation mechanism of nanotubular particles with a chrysotile structure changes dramatically. This is the direct cause of the non-monotonic dependence of the Mg/Ni ratio and the dimensional parameters of the (Mg1-xNix)3Si2O5(OH)4 nanotubes on the Mg/Ni ratio in the initial hydroxide.
The article shows the possibility of increasing the storage time of the opposite state (OS) at a temperature of 145 degrees C from 140 to 500 minutes in ferroelectric capacitors based on Hf0.5Zr0.5O2 (HZO) by shift of current integration endpoint to right. Consideration of transient processes between measurement pulses after 500 minutes capacitors baking at 145 degrees C can enhance the OS retention from 21 to 35 % of the preheating state. Opposite trend detected for the same sate (SS) (decrease from 56 to 35 %) and new same state (NSS) (decrease from 63 to 45 %). It is also shown that the presence of a voltage shift caused by an imprint in some cases may not lead to a loss of polarization due to the current flowing during the flat part of the trapezoidal voltage pulse.
The oscillatory behaviour of all solutions to the second-order delay differential equation with several deviating arguments and non negative coefficients is studied. Some sufficient oscillation conditions are obtained. An example is also given to illustrate the significance of our main results.
The work considers the application of laser correlation spectroscopy to the investigation of dispersed systems for such a case, which can be regarded as a transitional to the multiple scattering regime. It is shown that even a slight violation of the condition of single scattering by the increasing of concentration of scattering centers can affect the result of particle size measurements. It should be taken into account when studying colloids.
This study presents the design and theoretical analysis of a tunable biaxial hyperbolic metamaterial (BHMM) constructed from a layered n-GaAs/AlGaAs heterostructure under an external magnetic field. The objective is to optimize the tunability in order to control the dispersion shape for applications in the terahertz (THz) frequency regime. The effective medium approximation (EMA) model is employed and demonstrates the coexistence of two wave modes, namely, a closed ellipsoidal and an open hyperboloidal isofrequency surface. The results reveal that the external magnetic field acts as a powerful tuning mechanism, enabling spectral shifting of the dispersion and active switching between Type-I and Type-II hyperbolic regimes. In addition, the conditions required to achieve extreme compression of the isofrequency surface (IFS), which is essential for beam steering control, are analyzed. This compression occurs when one component of the permittivity reaches extremely large values, leading to the formation of near-flat segments on the isofrequency surface.
In this work, we investigate an alternative approach to phase modulation for information encoding and decoding in quantum key distribution systems. Specifically, we propose pulsed phase modulation, i.e. it has an envelope in addition to previously considered only harmonic temporal behavior of modulation index (depth), as a replacement for the conventional use of both intensity and phase modulators, which enables a more compact and cost-effective optical design. We further analyze how the principal parameters of this scheme affect the interference observed at the receiver and, consequently, their contribution to the quantum bit error rate in a subcarrier-wave quantum key distribution implementation.
Stability and durability of electrochemical energy conversion systems are significant issues. In this study, two stabilization strategies were investigated: 1) the application of few-layer graphene as a barrier layer on both sides of the Nafion membrane, and 2) the incorporation of polytetrafluoroethylene directly into the catalyst layers. Electrochemical performance was assessed in a two-electrode configuration: potentiostatic aging at 2.5 V and hydrogen crossover measurements. The characterization of materials functioning as barrier layers was conducted using scanning and transmission electron microscopy, laser correlation spectroscopy, and differential thermal analysis. It is shown that both components stabilize Nafion through interfacial interactions, resulting in a longer service life and reduced hydrogen crossover. While the reference sample showed increased crossover, the modified samples exhibited reductions of 50% and 33%. These findings underscore the potential of the studied materials in enhancing the stability of polymer electrolyte membrane water electrolyzers, contributing to the advancement of more durable and efficient systems for hydrogen energy applications.
A comparative assessment of the influence of 2D graphene structures derived from lignin, starch and cellulose through the self-propagating high-temperature synthesis method on the mechanical, thermal and electrical properties of poly(4,4'-oxydiphenylene pyromellitimide) films was conducted. It was found that the incorporation of synthesized nanoparticles allows for the modification of the mechanical properties of the polyimide material without a significant decrease in volume and surface resistivity. Dependencies of the changes in properties of nanocomposite film materials on the following factors have also been established and analyzed: the type of biopolymer from which the nanofiller was obtained; the morphometric parameters of the prepared nanosized material; the concentration of the nanofiller.
The ZrB2-ZrC ceramic powders were prepared by self-propagating high-temperature synthesis (SHS) using Zr-B4C composite powders as a precursor. Composite powders were obtained by ball milling in hexane (3 divided by 12 min). The structure, morphology, phase and fractional composition were investigated for both composite powders and SHS products. It was found that B4C grains are intensively embedded in Zr, and their distribution in composite particles becomes uniform by 9 min of ball milling. The possible route of the SHS reaction is proposed.
A perfect star packing can be described as a spanning subgraph whose connected components are isomorphic to the star graph K1,3. A perfect pseudo-matching is a spanning subgraph in which every component is isomorphic to either K2 or K1,3. The study of packing problems on fullerene graphs is of particular interest due to their potential relevance in describing local bonding arrangements in carbon nanostructures. In this paper, we study the uniqueness of perfect star packing, and the existence of pseudo-matchings in (2, 6)-fullerene graphs. Moreover, we show that the perfect star packing in these graphs is unique. Furthermore, we introduced some perfect pseudo-matchings in (2, 6)-fullerene graphs.
In this work, we report the one-pot aqueous synthesis of AuNPs using novel amidine derivatives of the closo-decaborate anion, functionalized with pendant thiol groups, as combined reducing and stabilizing agents. A comprehensive characterization using transmission electron microscopy (TEM) revealed the formation of nanoparticles with a distinctive and unusual hollow-core/dense-shell architecture, where a gold-rich shell encapsulates a low-Z element core. This unique morphology accounts for the observed absence of a characteristic surface plasmon resonance (SPR) band in the UV-Vis spectra, distinguishing these materials from classical solid-core AuNPs. X-ray photoelectron spectroscopy (XPS) confirmed the covalent attachment of the ligands via Au-S bonds and the integrity of the boron cage on the nanoparticle surface. The synthesis was optimized, establishing a 1:6 (Au:Ligand) molar ratio as ideal for achieving a narrow particle size distribution.
For the first time the thermal stability of the phase composition of (ZnS)(Ag2S)x sulfide heteronanostructures are studied. Solid-phase heteronanostructures (ZnS)(Ag2S)x with x = 0.002-0.50 are synthesized by hydrochemical co-deposition of ZnS and Ag2S sulfides. The ZnS nanoparticle size, estimated from the broadening of diffraction reflections, in the produced initial heteronanostructures is 2-4 nm. Annealing of the synthesized (ZnS)(Ag2S)x heteronanostructures in air at temperature from 25 to 530 degrees C and above leads to a change in their phase composition due to the oxidation of cubic ZnS sulfide to hexagonal zinc oxide. Oxidation begins at a temperature of approximately 250 degrees C; the ZnO nanoparticle size varies in a range of 12 to 17-25 nm. Oxidation of solid-phase (ZnS)(Ag2S)x heteronanostructures in air showed that weight loss that occurs upon heating from X250 to X430-450 degrees C is associated with the beginning of oxidation of the ZnS sulfide and the formation of the ZnO oxide. The most significant weight loss is observed after heating from X450 to X580 degrees C due to an increase in the ZnO content, oxidation of sulfur and its removal in the form of SO2.
