查看更多>>摘要：? 2022 Elsevier B.V.Magnesium titanate stannate - calcium strontium titanate (MgTi0.95Sn0.05O3-xCa0.8Sr0.2TiO3; abbreviated as MTS-xCST, x = 0.02, 0.04, 0.06, 0.08) microwave dielectric ceramics were synthesized via the conventional solid-state reaction. The optimum densities corresponded to higher sintering temperatures than the optimum quality factor, so the ceramics were classified as MTS-xCST-D and MTS-xCST-Q. All compositions exhibited a composite phase consisting of the rhombohedral structure MTS and the orthorhombic structure CST. As the sintering temperature rose, the relative densities of the ceramics increased significantly, while the formation of oxygen vacancies and titanium reduction were intensified. Finally, the x = 0.06 compositions sintered at 1425 °C (MTS-0.06CST-D) and 1375 °C (MTS-0.06CST-Q) had excellent temperature stability and low loss. At low frequency, the change of dielectric permittivity at 25–150 °C did not exceed 0.1, and the loss tangent was less than 0.003. In addition, microwave dielectric properties of MTS-0.06CST-D (εr = 20.4, Qf = 63,770 GHz, τf = ?1.8 ppm/°C) and MTS-0.06CST-Q (εr = 18.4, Qf = 74,740 GHz, τf = ?4.3 ppm/°C) compositions were obtained. These results suggest that MST-0.6CST ceramics could be a candidate material for 5 G microwave communication devices.
查看更多>>摘要：? 2022 Elsevier B.V.Taking hardware complexity into consideration of traditional continuous precursor purging systems for synthesis of few wall carbon nanotubes (CNTs) is a big challenge. Therefore, a novel precursor purging system for aerosol formation is designed to achieve uniform diameter distribution of CNTs, with the aerosol flow rate controlled either by number of ultrasonic mist makers or flow rate of carrier gas. Large droplets are turned into aerosol via an as-customized mist-producing system without the use of temperature or any chemical reaction. A built-in atomized gas valve is used to introduce the aerosol into a floating catalyst chemical vapour deposition (FCCVD) reactor. After an influential comparison of as-customized purging systems to the mostly used complex and big-budget systems for uniform diameter distribution, the quality of these CNT assemblies, synthesized using two different carrier gases (argon and hydrogen) is examined. Herein, CNT sheets with mostly fewer walls CNTs (diameter 2–10 nm) have been synthesized using this approach, with the controlled size of catalyst nanoparticles, under H2 atmosphere exhibiting low sulphur impurities, as evidenced by Raman, EDS, and XPS spectra, and have a fourteen-fold greater electrical conductivity (5.78 × 104S/m) than those synthesized under Ar atmosphere. Moreover, these sheets are also twisted and wrapped by insulating heat shrink tubes. The maximum current density of these conducting CNT wires having 250 μm diameter is 8.15 × 106A/m2. Further, one of the domestic applications of LED bulb (3–45 W) lightning is also demonstrated which shows the suitability of these conducting wires in numerous hi-profile applications.
查看更多>>摘要：? 2022 Elsevier B.V.The application of microwave absorbing materials is one of the important means to reduce electromagnetic pollution. Transition metal phosphides as absorbers with high conductivity attract researchers' interest. Therefore, in this paper, the novel cobalt phosphide wrapped by reduced graphene oxide (CoP/RGO) were prepared by simple hydrothermal and phosphating reaction. Meanwhile, the introduction of RGO is beneficial to enhance the conductive loss and polarization loss of materials. Compared with most of the reported transition metal phosphate-based absorbents, CoP/RGO has a better microwave absorption (MA) performance. The minimum reflect loss (RLmin) value can reach ? 52.60 dB with 2.05 mm, and the maximum effective absorption bandwidth (EAB, RL<?10 dB) can reach 5.04 GHz at 2.25 mm. The superior MA performance of CoP/RGO composites makes it possible to be a candidate as an absorber.
查看更多>>摘要：? 2022 Elsevier B.V.As an emerging two-dimensional material, MXene has been widely used in electrocatalysis, photocatalysis and other fields, which is expected to play a huge role in the field of piezocatalysis due to its high conductivity. In this work, titanium carbide MXene loaded with molybdenum disulfide (Ti3C2 @MoS2) was prepared by growing MoS2 vertically on the surface of Ti3C2 MXene to expose more marginal active sites. In addition, the high conductivity of Ti3C2 can accelerate the free carrier transfer and enhance the piezoelectric response, thus boosting the piezocatalytic activity. Among them, the optimal Ti3C2 @MoS2-7 established excellent piezocatalytic activity of bisphenol A (BPA) degradation and hydrogen evolution, and the corresponding rate constant was 0.095 min?1 and 197.3 μmol·g?1·h?1, which was 4.1 times and 5.9 times of MoS2, respectively. In addition, Ti3C2 exhibited a catalytic activity higher than that of the classical piezoelectric semiconductor MoS2 under the ultrasonic, and the possible origins were speculated by piezoelectric force microscope and free radical detection. It demonstrates a great application potential of MXene and MXene-based nanomaterials in piezocatalysis, providing a feasible strategy for the design of piezocatalysts.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, we report a detailed experimental study regarding the impact of copper oxide (CuO) secondary phase and heat treatments on the structural, magnetic, and magnetocaloric properties of the near-room temperature Pr2∕3Sr1∕3MnO3 (PSMO) magnetic refrigerant. Our investigations are carried out by using structural and microstructural analyses, alongside magnetization measurements. The analysis of X-ray diffraction data of PSMO(95 %)-CuO(5 %) (PSMO-CuO) samples shows the coexistence of both CuO and PSMO phases. Further, the microstructural analysis of PSMO-CuO reveals that the addition of CuO significantly enhances the grains size. On the other hand, the added secondary phase markedly reduces the Curie temperature (Tc) from 293 K for PSMO to about 273 K for PSMO-CuO composite while increasing the magnetocaloric effect. This decrease in Tc is associated with a significant change from 162° to about 156° in the Mn-OII-Mn bond angle respectively. Moreover, performed investigations regarding the role of heat treatments unveil that the observed changes in the structural and magnetic features are mainly driven by the secondary phase that modify grains size and double-exchange interactions in the PSMO compound. Interestingly, our findings demonstrate that the Curie temperature of the PSMO and accordingly its magnetocaloric effect can be tailored by adding small amounts of CuO without need to substitution on cation sites. In the light of obtained results, a multilayered refrigerant composed of PSMO and PSMO-CuO is proposed to cover the magnetic cooling temperature range close to room-temperature. The resulting entropy change remains practically constant between 273 K and 293 K. Such a behavior is highly appreciated from a practical point of view, particularly in cases where the cooling process is carried out by using the AMR and Ericsson cycles.
查看更多>>摘要：? 2022 Elsevier B.V.Ice formation on the surfaces of high-voltage wires could result in disaster. Superhydrophobic (SHP) treatment of the wire surfaces to reduce the icing adhesion is considered as a promising anti-icing strategy. Thus, the microscopic mechanism of icing adhesion needs to be investigated, including the icing process on a solid surface with different morphology and proper chemical doping among some others. In order to understand this ice adhesion at atomistic scale, nanoscale ice pulling and shearing on Al-terminated α-Al2O3(0001) surface with different morphology and doped atoms are evaluated by means of molecular dynamics simulations. The results show that the ice stress on surface is anisotropic and related to the solvent accessible surface area (Π) and non-bonded interaction. For all the surfaces, the largest stress is the shearing in perpendicular to the groove direction, whereas the smallest one is the pulling stress in normal to a surface. In particular, the ice adhesion induced stress seems to be proportional to parameter Π. Furthermore, it is suggested that the Fe-doping onto the Al-surface can reduce the non-bonded interaction and also Π, and thus the ice adhesion stress. The results are confirmed with anti-icing experiments at the same time, which help to understand the microscopic mechanism of ice adhesion on surfaces with different roughness, and provide new insights onto anti-icing technology.
查看更多>>摘要：? 2022 Elsevier B.V.Lithium-sulfur batteries are advanced energy storage system with high theoretical specific capacity and low cost but suffer from poor cyclic performance. To overcome the shortcomings, this study synthesized graphene oxide (GO)/Cu(OH)2 composites using the modified Hummers method and electrostatic self-assembly process. The sulfur was anchored in the GO/Cu(OH)2 composites using the melting method. The oxygen-containing function groups of GO are helpful for achieving good ion/electron accessibility, and the interlayers of GO have many active sites for polysulfide conversion. The polar hydrophilic hydroxyl group of Cu(OH)2 particles have strong chemisorption for polysulfides during the electrochemical process. Therefore, the synergistic effect of GO and Cu(OH)2 in the composites as sulfur hosts can inhibit the dissolution and shuttling of polysulfides. The lithium-sulfur batteries with GO/Cu(OH)2 composites as hosts have high capacity of 1427 mAh g?1 at 0.1 C, 1222 mAh g?1 at 0.5 C, and excellent cyclic performance for 250 cycles with a retained capacity of 929 mAh g?1 (0.5 C).
查看更多>>摘要：? 2022 Elsevier B.V.Topological crystalline insulators (TCIs) have a new topological state where topological nature comes from crystal symmetries without necessitating spin-orbit coupling. Their superb electronic, magnetic, and superconducting properties have intensively been studied. Despite great potential, however, their nonlinear optical properties are rarely examined. For the first time, this study investigates the nonlinear refraction and absorption properties of SnTe TCIs using the Z-scan techniques. A high nonlinear refractive index of -0.111 ± 0.004 cm2/GW and a nonlinear absorption coefficient of -(2.02 ± 0.135)× 103 cm/GW are obtained from SnTe TCIs at the commercially important telecommunication wavelength, being superior and/or comparable to two dimensional (2D) materials and/or renowned photonic crystals. Ab-initio simulations show that SnTe TCIs are suitable for ultrabroad-band application and mechanically stable at high thermal conditions. Lastly, we demonstrate that 1550 nm mode-locked femtosecond lasers can readily be achieved by exploiting the conspicuous nonlinear optical absorption of SnTe TCIs without using any nano-engineered ones like quantum dots. This study strongly indicates a promising potential of SnTe TCIs in a wide range of nonlinear optics, opening an avenue toward advanced TCIs-based photonic technologies.
查看更多>>摘要：? 2022 Elsevier B.V.Nanoparticles deposited on a substrate could be an excellent candidate for environmental and catalytic applications. Herein, TiO2 nanoparticles were prepared by a solvothermal method and then electrophoretically deposited on a substrate via an in-situ one-pot method. The developed process does not need a washing process (after synthesis), neither sintering nor organic binders (for deposition). Transmission electron microscopy (TEM), used to analyze the deposited nanofilm, confirms that the layer is crack-free and homogeneous. Then sonophotocatalytic performance of TiO2 nanofilm in the degradation of the organic pollutants (Methylene blue, phenazopyridine) was investigated, since the problem of filtration of the catalyst after the sonophotocatalysis process is eliminated. About 90 % of the organic pollutant was degraded by the sonophotocatalytic process, while the application of ultrasound alone is capable of degrading 14 %, and UV light alone is about 55 %. The synergic effect of ultrasound and UV light was calculated and reported about 59 %. The applicability of the optimized sonophotocalytic system was evaluated by decomposition of a commercial tablet (phenazopyridine), and the efficiency was 84 % in an hour. Most importantly, the reusability of the nanofilm was investigated, and after 4 uses, the nanofilm was able to degrade 84 % of organic pollutants. Owing to its excellent performance, the nanofilm prepared by EPD is suitable for a broad range of environmental and energy applications.
查看更多>>摘要：? 2022Aqueous ammonium-ion batteries are eco-friendly and abundant systems that exhibit diffusion. These systems have been reported in recent years. Vanadium pentoxide (V2O5) with a layered structure is a good electrode material. A Co-doped V2O5 cathode characterized by good reversibility and rate performance was prepared using the hydrothermal method to improve the ionic diffusion kinetics characterizing the systems and address the issue of low conductivity of V2O5. Saturated V2O5 (NH4)2SO4 solution was used as the electrolyte to fabricate the ammonium ion battery. Pure V2O5 and V2O5 samples with varying levels of cobalt dopants, V2O5-2Co samples doped with 2 % cobalt exhibited a maximum capacity of 172 mAh g–1 and coulombic efficiency of 61.6 % after 500 cycles at the current density of 1.0 A g–1. This indicated good cyclic reversibility. The high energy density was established to be ~152 Wh kg–1, and the capacity retention rate was 49.2 % after 1000 cycles. These results indicate that Co-doped V2O5 nanoparticles can potentially help in improving the electronic conductivity of the system and provide an effective pathway for rapid electron transfer.
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