Journal of Materials Research最新文献

The dielectric, ferroelectric and energy storage properties of 0–3 composite systems with 0.92(Bi_0.5Na_0.5)TiO₃–0.08BaTiO₃(BNT–BT) ceramics and Poly(vinylidene fluoride trifluoroethylene) P(VDF–TrFE) copolymer were investigated. The composites are prepared by solvent casting followed by hot-pressing technique. The presence of good ferroelectric properties in the composites is confirmed by the electroactive β-phase which was found to be more than 80% in almost all the composites. The inorganic ceramic fillers improve the dielectric properties of the ceramics. The polarisation response in the composite film increases because of the interface effect between the polymer matrix and ceramic filler. The room-temperature ferroelectric hysteresis loops indicate an increase in remnant polarisation of the matrix with the concentration of filler. The energy storage density efficiency of the composites changes from 81 to 58% upon adding the ceramic filler. Piezoelectric properties of P(VDF–TrFE)–0.92(Bi_0.5Na_0.5)TiO₃–0.08BaTiO₃ composite were also investigated and found to be increased. So this composite is preferable for energy storage as well as harvesting applications.

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Magnetization reversal in thin cylindrical nanodisks with radius between 20 and 100 nm is investigated with particular emphasis to modulation of disk thickness. The nanodisk is kept 1 nm thin at the center, whereas it gradually thickens to 21 nm at the periphery. The thickness modulation stabilizes the vortex closure state as the ground state in nanodisk for radius as low as 20 nm. An onion state appears at remanence during in-plane magnetization reversal. Nudged elastic band method verifies that the vortex state is highly stable in all the nanodisks. In the nanodisk of 100 nm radius, the vortex state requires an energy of 2677 kT to transit into onion state where kT is thermal energy at room temperature. This stability however reduces with size of nanodisk and the smallest nanodisk of 20 nm radius has to surpass an energy barrier of 120 kT to topple over to onion state.

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An innovative electrochemical sensor has been developed using Cr–Ni bimetal-organic frameworks (MOFs) for detecting the anti-prostate cancer medication, flutamide, in environmental samples. The sensor utilizes a modified glassy carbon electrode (GCE). The Cr–Ni MOF-modified electrode demonstrated significantly higher peak currents compared to the bare GCE or electrodes modified with either Cr-MOF or Ni-MOF alone. This enhanced performance is attributed to superior conductivity, robust catalytic capabilities, and the synergistic interactions of bimetals within the organic framework assembly. The sensor was optimized for flutamide detection using differential pulse voltammetry in a phosphate buffer solution at pH 9. It achieved a linear detection range of 10 to 100 μM, a low detection limit (LOD) of 0.09 μM, and a limit of quantification (LOQ) of 0.30 μM. The sensor also demonstrated high stability, specificity, and reproducibility.

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The solidification behavior of Ni-based superalloy in the cooling rates range of 0.5–10 °C/s was investigated for simulation the casting process. Scheil model was used to calculate the solidification path of Ni-based superalloy. The results show that the precipitation sequence of solid phases from the liquid phase was as follows: Liquid (L) → L + γ → L + γ + MC → γ + MC + γ/γ′ eutectic. The precipitation temperature of γ/γ′ eutectic was increased with the increase of cooling rate. The solidification structures of Ni-based superalloy were found to be mainly dendritic, and the distance between dendrites decreased with the increase of cooling rate. The MC carbides enriched with C, Ti, Hf, Ta, and other elements presented rectangles, which contributed to refine the solidification structure as the heterogeneous nucleus. The nano-indentation was used to measure the γ + γ′ matrix and MC cabides, and the mechanism of cooling rate on the evolution of microstructure during the solidification was discussed.

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The solidification structures of Ni-based superalloy.

Perovskite chalcogenides have been acknowledged as a potential candidate for solar cell applications. We have investigated new chalcogenide perovskite AInX₃ (A = Sc, Y and X = S, Se) materials in the present study. The WIEN2k packages are used based on the framework of DFT. AInX₃ (A = Sc, Y and X = S, Se) are crystallized in the orthorhombic phase. The band gap is calculated by TB-mBJ. All the studied compounds have indirect band gaps in the visible energy range. They show high carrier conductivity because of small effective masses. The optical parameters including the complex dielectric constant, refractive index, reflectivity, absorption coefficient, optical conductivity, energy loss function, and extinction coefficient are examined in detail. The thermoelectric properties are also investigated through the BoltzTraP code. Elastic properties suggest that all materials are ductile. The calculated characteristics indicate that these compounds have the potential to be used in photovoltaic devices.

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Unit cell crystal structure of chalcogenide perovskite ABX₃ (A = Sc, Y, B = In and X = S, Se) in an orthorhombic (GdFeO₃-type) phase; wine-red: A = Sc/Y, purple: B = In; and yellow: X = S/Se. Electronic band lies in visible region for all the studied compounds.

Nanoscience has grown in recent decades since the development of nanoparticle synthesis and application. Although many studies have phenomenologically interpreted the formation of particles at the nanometric scale, the evolution of this field of study has focused on controlling the parameters enabling the attainment of desired morphologies and dimensions using ligands on nanoparticle surfaces. Molecules bound to nanostructured surfaces act in morphological control and aggregation processes as surface ligands transfer functional characteristics to nanostructures, which show core differences from that class of material. This study shows recent advances in nanoparticle surface functionalization with ligands either in their synthesis or in subsequent steps to modify nanoparticle surfaces. We also offer a discussion on ligand classification based on Lewis acid‒base properties and their impact on the colloidal stability of nanoparticles, enabling us to analyze the solvent‒ligand interactions that transfer characteristics from the ligand to the nanoparticle, generating flocculated or dispersed colloidal solutions.

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In perovskite solar cells, annealing time and temperature are crucial parameters to obtain high quality film crystallization, desired morphology, and texture. Annealing enhances charge-carrier transport and minimizes non-radiative defects, resulting in improved power conversion efficiency (PCE). Firstly, we have synthesized a novel and hybrid halide double perovskites (DP) material MA₂NaBiCl₆ using hydrothermal and we have done material characterizations. We have fabricated solar cell using as-synthesized DP as a absorber material, ZnO as electron transport layer and Cu₂O as hole transport layer and performance parameters was calculated. Furthermore, to enhance the device performance, we have annealed it at different temperature varying from 50 to 225 °C and analyzed improvements in material’s morphology and device performance. Also, the annealing time (30 s–5 min) was varied at optimum annealing temperature. The optimized annealing temperature and time is 200 °C and 2 min respectively on which we achieved 3.49% PCE from the RT efficiency 1.671%.

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 Li-ion batteries have become essential in energy storage, with demand rising steadily. Cathodes, crucial for determining capacity and voltage, face challenges like degradation in the form of thermal runaway and battery failure. Understanding these degradation phenomena is vital for developing mitigation strategies. Experimental techniques such as XAS, XPS, PES, UV–Vis, RIXS, NMR, and OEMS are commonly used, but theoretical modelling, particularly atomistic modelling with density-functional theory (DFT), provides key insights into the microscopic electronic behaviours causing degradation. While DFT offers a precise formulation, its approximations in the exchange-correlation functional and its ground-state, 0K limitations necessitate additional methods like ab initio molecular dynamics. Recently, many-body electronic structure methods have been used alongside DFT to better explain electron–electron interactions and temperature effects. This review emphasizes material-specific methods and the importance of electron–electron interactions, highlighting the role of many-body methods in addressing key issues in cathode degradation and future development in electron–phonon coupling methods.

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Fe₃O₄@SiO₂/4A magnetic nanocomposites (magnetic 4A zeolite) have been synthesized by hydrothermal method which endowed 4A zeolite with magnetic separation characteristics. XRD results showed that the magnetic 4A zeolite had the characteristic diffraction peaks of both 4A zeolite and Fe₃O₄. The SEM images displayed the combination of 4A zeolite and Fe₃O₄. N₂ physical adsorption showed that magnetic 4A zeolite had a large specific surface area and can provide a large number of adsorption sites for ammonia nitrogen. The magnetic separation results showed that magnetic 4A zeolite exhibited fast response to external magnetic field, and the saturation strength measured by VSM was 5.85 emu g⁻¹, indicating the superparamagnetic properties of magnetic 4A zeolite. The removal rate of ammonia nitrogen by FSA-M-1 sample reached to 43.18%. After 6 rounds of repeated adsorption experiments, each sample’s magnetic recovery rate was above 95%, and the removal rate of ammonia nitrogen was higher than 36%.

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Fractal (micro)-structures are observed in many thin films, bulk specimens and fractured samples. A phenomenon that leads to the formation of these structures in thin films is diffusion-limited aggregation. The assumption in diffusion-limited aggregation is that formation of such structures is independent of the source conditions and relies only on film-substrate interactions with requirement of single crystallinity in both cases. The possibilities of fractal structures occurring in amorphous or crystalline film-on-amorphous or crystalline substrate have received limited attention. However, results on sputter deposited transition metal nitride thin films show that these combinations can indeed lead to fractal structures such as dendrites and snowflakes. In this work we postulate that the formation of these microstructures is perhaps related and sensitive to the initial conditions provided for growth, which leads to a conclusion that perhaps chaos-related dynamics is at work. We believe that a new theoretical framework is required to explain these phenomena. An attempt to identify the knowns and the unknowns in this area is made using our results as well as some available in the literature.

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