查看更多>>摘要：? 2022 Elsevier B.V.Flash sintering (FS), as a novel sintering technique, has enormous potential in taking powder particles into dense ceramics. Here, dense SrTiO3 ceramics with small grain size and excellent electrical properties (ε = 453, tan δ = 0.002) can be flash sintered at furnace temperature of 1145 ℃ via combining a field of 150 V/cm and a current density of 40 mA/mm2. The effect of current density limits on the microstructure morphology, density, phase structure and dielectric properties of SrTiO3 ceramics is investigated. It is shown that the current density parameter is of great importance in the control of the densification behavior and grain growth during flash sintering: the grain size increases gradually with raising the current density, while the density increases first and then slightly decreases. Moreover, the onset temperature of flash sintering and phase structure is independent of the current density in this experiment. These ceramics exhibit a satisfactory correspondence between electrical properties and structure. Based on the black-body radiation analysis, the ability of Joule heating to cause flash sintering is limited. Thus, the avalanche multiplication model was combined to help understand the origin of flash sintering.
查看更多>>摘要：? 2022 Elsevier B.V.Among vanadium-based materials, V6O13 is considered to be an ideal cathode candidate material due to its high theoretical capacity and energy density. However, as mixed-valence vanadium oxide, it faces the challenge of controllable synthesis, and suffers unsatisfactory cycle performance due to the unstable structure. Constructing 3D micro/nano-structures is a very effective method to solve the above problems. Herein, we report a simple template-free solvothermal method to controllably synthesize 3D hollow microflowers structure formed by self-assembly of thin nanosheets. The growth mechanism of the hollow microflowers is revealed by changing the solvothermal reaction time and the content of ethylene glycol. As a cathode material for Li-ion batteries, the V6O13 hollow microflowers exhibit an initial discharge specific capacity of 326 mAh/g at a current density of 0.1 A/g. Even at a high current density of 1 A/g, the V6O13 hollow microflowers still deliver a discharge capacity of 183.2 mAh/g, and display high capacity retention of 75.6% after 500 cycles. The excellent electrochemical performance benefits from the unique advantages of 3D hollow microflowers structure, that is, large specific surface area, abundant mesopores, and robust structure. These results indicate that the V6O13 hollow microflowers have great potential as the long-life and high-rate cathode materials for the next generation of Li-ion batteries.
查看更多>>摘要：? 2022 Elsevier B.V.Graphene as a single or few-layered 2D material acts as a stable and efficient substrate to build effective nanocomposite catalysts for numerous applications. In this study, a few layers of exfoliated graphene sheets are engineered with novel high entropy alloy (HEA) nanoparticles through mechanical milling technique followed by sonication. Three different HEA-Graphene (HEA-G) composites were produced with the metal-to-graphene weight ratio of 50:50, 70:30 and 90:10. As-synthesized HEA-G composites were extensively characterized through microscopy (AFM and TEM) and spectroscopic (Raman) techniques to understand the HEA nanoparticle formation and distribution over the surface of graphene sheets. Further, the catalytic behaviour of HEA-G composites was examined using cyclic voltammetry (CV) and chronoamperometry (CA) to understand the non-enzymatic oxidation of urea using the HEA-G composites. The onset of the catalytic behaviour was observed with the composite 50:50 which was increased till 70:30 composite. However, the 90:10 composition exhibited minimal catalytic response compared to the other two composites. The composite 70:30 being the best performer was used to derive sensitivity based on the oxidation of urea which was found to be 37.4 μAm M?1 cm?2. The current study opens the window to explore a new class of all possible HEA nanocomposites for electrocatalytic applications.
查看更多>>摘要：? 2022 Elsevier B.V.This study examines the role of Gd3+ ions in a novel spinel ferrite with a general composition of Mn0.9Zn0.1Ni0.05Ti0.05GdxFe1.9?xO4; 0.0 ≤ x ≤ 0.04, to determine the critical concentration of Gd3+ ions that at which the structural and dielectric properties of the ferrite show an improvement. The structure of the samples, which were obtained using the traditional ceramic method, was tested by comparing the resulting X-ray diffraction patterns with the peaks of ICDD card No. 74–2402. Scanning electron microscopy (SEM) micrographs were used to evaluate the surface morphology of the samples. The substitution of Gd3+ions resulted in an increase in the bulk density of the prepared samples. In the frequency range of 0.1–5 MHz, the temperature and frequency dependences of AC electrical resistivity and electrical permittivity were investigated and discussed. Maxwell-Wagner and Koops models were used to describe the frequency dependence of dielectric characteristics. Furthermore, the activation energy, AC resistivity, dielectric loss tangent, and electrical permittivity were investigated in terms of their compositional dependence. The obtained results showed also that the magnetization was found decreases as the concentration of Gd3+ ions increases. The final results showed that increasing the Gd concentration enhanced the physical and dielectric properties of the samples, with an increase in AC resistivity and a 68% reduction in dielectric loss. The Final results also indicated that the sample with x = 0.04 displayed the highest AC resistivity and lowest dielectric loss, which can be exploited in certain technical applications such as transformer cores.
查看更多>>摘要：? 2022 Elsevier B.V.Transition metal dichalcogenide monolayers have shown enormous potential in thermoelectric application in recent years. We now focus on the thermoelectric properties of WS2-WSe2 nanoribbons with superlattice (SL) and Janus (JA) structures using first-principles calculations. The WS2, WSe2, SL, and JA nanoribbons with the ribbon width from 5 to 7 have high structural stabilities. All nanoribbon electronic structures are semiconductors and the ribbon width will modify bandgaps. It can be also observed that WS2, SL, and JA nanoribbons with a ribbon width of 5 have the largest carrier mobilities (up to ~500–1400 cm2 V?1 s?1) and relaxation times (up to ~400–600 fs). We further calculate the electronic transport coefficients and discover that the SL and JA nanoribbons with a ribbon width of 5 exhibit the largest power factors as high as ~80 mW m?1 K?2. Afterwards, the minimum lattice thermal conductivities of SL and JA nanoribbons are 0.53 W m?1 K?1 and 0.61 W m?1 K?1, which are suppressed owing to the declining phonon group velocity and phonon lifetime. The maximum ZT values of SL and JA nanoribbons can reach 5.47 and 4.13. This investigation provides a solid evidence for the application of WS2-WSe2 nanoribbons as promising thermoelectric materials.
查看更多>>摘要：? 2022 Elsevier B.V.TiO2-based heterojunction nano-thin films are competitive photocatalysts for water pollution treatment due to their abundant availability, non-toxicity, and rapid separation of photogenerated charge carriers. Moreover, the layer thickness, as a vital factor influencing the photocatalytic properties of TiO2-based heterojunction nano-thin films, requires further exploration. Herein, we prepared heterostructured TiO2/CuO nano-thin films by a facile magnetron sputtering approach. The TiO2 nanoparticles were uniformly deposited onto the underlayer CuO to construct heterojunction, and the thickness of the upper TiO2 layer and underlying CuO layer were precisely controlled by simply varying the sputtering time. The samples were described via SEM, XRD, Raman, AFM, and UV–vis DRS analysis. The SEM results exhibited that the optimized heterojunction thin film was composed of the underlying CuO layer with a thickness of 90 nm and the upper TiO2 layer with a thickness of 120 nm. The optical absorption studies of this nano-film showed two band gaps of 1.8 and 3.1 eV. The CuO/TiO2 heterojunction nano-film (1 cm × 1 cm) exhibited superior photocatalytic activity, by degrading 92.94% Rhodamine B (RhB) within 120 min duration under a 300 W high-pressure mercury lamp illumination, which benefited from the better crystalline structure, more active sites, and the effective electrons and holes transfer. Moreover, a possible charge transfer mechanism of TiO2/CuO nano-thin film was proposed based on the results of the capture experiment.
查看更多>>摘要：? 2022 The Author(s)The mixtures of selected protic and aprotic ionic liquids with their parent superacids were used as electrolytes in the process of hydrogen electrosorption in thin (ca. 0.5 μm) Pd films. The properties of ionic liquids and their mixtures with superacids were characterized with the use of electrochemical and physicochemical methods to show the perspectives of their potential utilization as electrolytes in hydride/protonic systems. Based on the electrochemical studies it was possible to estimate the minimum concentrations of the superacids in protic and aprotic ionic liquids which give maximum hydrogen absorption capacities in Pd (H/Pd). Unusual, previously unnoticed ‘two-step’ α→β phase transition was observed on the hydrogen electrosorption isotherm of Pd for the process of hydrogen absorption from the protic ionic liquids for some superacid concentrations. 1H NMR spectroscopy of the protic ionic liquids enables to discuss the relation between proton mobility and hydrogen electrosorption properties.
查看更多>>摘要：? 2022 Elsevier B.V.In view of the rapid development of printing and electrophoretic display technologies, there is a high demand for pigments with pre-defined physical properties and pure colouration of one of the three subtractive CMY primaries (cyan, magenta or yellow). This contribution focuses on the development of an appropriate synthesis method of the yellow-hue Ni3(PO4)2 inorganic phosphate with the purpose to enable its application in advanced light reflective technologies. Polymerizable precursor method (PPM) and solid state reaction (SSR) were utilized for the synthesis and the results were evaluated with regards to phase composition, crystallinity, particle morphology and size distribution, surface area, porosity, density, optical reflectance and colour parameters of the product. Accordingly, PPM provides a number of advantages in comparison to SSR and to literature data reporting other inorganic yellow-shade pigments. Ni3(PO4)2 obtained by PPM fulfils two main demands as a subtractive primary pigment: ideal yellow shade and uniform spherical micron-sized particles morphology. Moreover, the product shows darker and saturated colouration, especially when taking into account the low particle size distribution which typically reduces colour saturation and increases lightness of the product. The obtained pigment with bright yellow colouration, that represents one of the CMY primaries, has a high potential for application in printing technologies and, after appropriate modification, in electrophoretic displays.
查看更多>>摘要：? 2022 Elsevier B.V.The development of energy materials possessing large number of active sites and exhibiting increased catalytic performance is an important strategy in (electro)catalysis. In this study, Ni2P/NiFeP owning rich interfaces was fabricated within the Ni(OH)2 nanosheet arrays to form hetero-structured Ni2P/NiFeP catalysts via the Kirkendall effect. The as-prepared catalysts exhibited only 250 mV overpotential towards the oxygen evolution reaction (OER) at + 50 mA cm?2 in alkaline electrolytes, and delivered a current density of + 10 mA cm?2 at 1.57 V in a complete and fully functional water electrolyser using the Ni2P/NiFeP and Ni2P/Ni2P catalysts on the anode and cathode side, respectively. The evolution and reconstruction of the interface in Ni2P/NiFeP during the electrochemical stability test experiments was also studied. It was found that reducing the interface resulted in a decrease in electrocatalytic performance and a transition in crystal structure to amorphous state was observed. The method developed in this investigation has been found to be useful for developing catalysts of rich interfaces, in turns paving the way for integrating novel highly active and stable electrocatalysts in electrochemical water splitting technologies.
查看更多>>摘要：? 2022 Elsevier B.V.Domain walls and precursors in ferroelectric and ferroelastic materials are of great importance for the optimization of ferroic devices and novel paradigms for domain switching. Any domain wall- or ferroic-precursor-based device requires knowledge about structural phase transitions and the formation and evolution of mesoscopic structures. In this review, Resonant Piezoelectric Spectroscopy (RPS) is shown to be a convenient investigative tool for the characterization of ferroic materials. RPS simultaneously measures elastic and piezoelectric properties related to domain walls and ferroic precursors and correlates the onset of phase transitions and the formation of mesoscopic structures with piezoelectric properties. Examples are given for ferroelastic, ferroelectric, and relaxor materials, including SrTiO3, BaTiO3, and PbMg1/3Nb2/3O3. Comparison of the data with incipient ferroelectric KTaO3 provides insights into the physical meaning of the coherence temperature and the Burns temperature in ferroelectrics, relaxors, and potentially other ferroic systems.
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