Results 1 - 10 of 133425
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[en] Lithium thioborates are promising fast Li-ion conducting materials, with similar properties to their lithium thiophosphate counterparts that have enabled the development of solid-state Li-ion batteries. By comparison, thioborates have scarcely been developed, however, offering new space for materials discovery. Here we report a new class of lithium thioborate halides that adopt a so-called supertetrahedral adamantanoid structure that houses mobile lithium ions and halide anions within interconnected 3D structural channels. Investigation of the structure using single-crystal XRD, neutron powder diffraction, and neutron PDF reveals significant lithium and halide anion disorder. The phases are non-stoichiometric, adopting slightly varying halide contents within the materials. These new superadamantanoid materials exhibit high ionic conductivities up to 1.4 mS cm, which can be effectively tuned by the polarizability of the halide anion within the channels. (© 2020 Wiley‐VCH GmbH)
[en] Heating and cooling are two important procedures in manufacturing as well as transportation industries.Rather than the conventional fluids, solutions of fluids with metal nanoparticles have higher thermal conductivity for effective cooling. Therefore, present paper is a comparative study of squeezing flow analysis of copper oxide–water and oil (kerosene)-based nanofluid between two parallel plates. Magnetohydrodynamic flow of kerosene-based nanofluid along with the dissipative heat energy may enhance the thermal properties of the fluid. Assuming self-similar variables, the governing equations get transformed into non-dimensional forms and approximate analytical techniques such as variation parameter method is employed for these transformed equations. With the well posed physical parameters, the computation is carried out using the mathematical package MATHEMATICA and displayed via graphs and numerical results are shown in tabular form. Favourable cases in comparison with earlier studies are also studied wherever possible. However, when the plates are away from each other, it is seen that the kerosene-based nanofluid velocity overrides the water-based nanofluid whereas the impact is reversed in the case of squeezing.(author)
[en] The low-energy electron band structure of Cu2Si on Si(111) has been investigated using angle-resolved photoemission spectroscopy. Cu2Si exhibits two Dirac nodal-lines, stemming from the crossing of one electron-pocket with two hole-pockets, that are protected by mirror reflection symmetry. When Cu2Si is placed on Si(111), the hole-pockets and their satellite bands due to the quasi-5 x 5 periodicity are clearly observed whereas the electron-pocket is observed with very weak spectral intensity. Interestingly, close to the Fermi energy, the hole-pockets exhibit almost linear energy-momentum dispersion when their spectral width is also linearly proportional to energy. These findings indicate that Cu2Si on Si(111) can host Dirac nodal-line fermions, of which low-energy excitations might depart from those of the conventional Fermi liquid.
[en] Layered transition metal dichalcogenide (TMD) nanomaterials are promising alternatives to platinum (Pt) for the hydrogen evolution reaction (HER). However, the family of layered TMDs is mainly limited to Group IV-VII transition metals, while the synthesis of layered TMDs based on metals from other groups still remains a challenge. Herein, we demonstrate by atomic-resolution transmission electron microscopy that hexagonal RuSe (h-RuSe) nanosheets with a mixture of 2H and 1T phases can be obtained by a facile bottom-up colloidal synthetic approach. The obtained h-RuSe, which can be transformed into the thermodynamically favorable phase of cubic RuSe (c-RuSe) only after annealing at 600 °C, exhibits Pt-like HER performance, with a fivefold turnover frequency enhancement compared to the c-RuSe in alkaline media. Experimental results and density functional theory (DFT) calculations reveal that the enhanced adsorption free energies of HO (ΔG), optimized adsorption free energies of H (ΔG), and increased conductivity of h-RuSe contribute to its superior HER activity. (© 2021 Wiley‐VCH GmbH)
[en] We report the biogenic synthesis of ZnO nanoparticles using Mangifera indica aqueous extract and density functional theory/time-dependent density functional theory (DFT/TD-DFT) calculations on Zn12O12 nanocluster compared with various basis sets (B3LYP/6-31G, B3LYP/LANL2DZ, and B97D). The genesis of ZnO nanoparticles was achieved from the reduction of capping agent ZnSo4. The properties of ZnO nanoparticles were signalized by UV, FTIR, FESEM-EDAX, and XRD analysis. The intense band at 380nm in the UV-Vis absorption spectrum results from the formation of ZnO nanoparticles. The structure of ZnO nanoparticles was anatomized by FESEM analysis and the presence of Zn was confirmed using EDAX. The frontier molecular orbital exploration has been investigated to govern the charge transfer characteristics of donor-acceptor moieties of the Zn12O12. The energy gap (Eg), binding energy (EB), global reactivity descriptors, and the total dipole moment has also been investigated for Zn12O12. The total density of states (DOS) was analyzed to describe the orbital hybridization of Zn12O12. Mulliken atomic charge distribution, NBO analysis and molecular electrostatic potential (MEP) have also been studied. The first-order hyperpolarizability calculation proves that the Zn12O12 is a suitable candidate with the predominant nonlinear optical property. TD-DFT excited state analysis of Zn12O12 was completely consistent with the experimental data of the UV-Vis spectrum makes its application in solar cells. (author)
[en] This paper deals with a detailed investigation of the effects of various metal oxide nanoparticles on unsteady stagnation point flow of a hybrid base fluid impinging on a flat surface. The ‘single-phase’ nano fluid model,i.e., the Tiwari and Das model, is considered for the study. We consider water and ethylene glycol in 1:1 ratio as the base fluid and four different types of metal oxides, namely, CuO, TiO2, ZnO and MgO as the nanoparticles.Using similarity transformations, the conservation equations are transformed into self-similar ordinary differential equations. Dual and unique similarity solutions are obtained for certain set of values of parameters. The analysis explores many important findings. Dual self-similar solutions exist up to a certain critical value of the decelerating unsteady parameter and the critical value is independent of the type of metal oxide nanoparticles considered. The strongest surface drag force is observed for the nano fluid with CuO nanoparticles, while the weakest is for the nano fluid with MgO nanoparticles. The heat transfer rate is highest for the nano fluid with CuO nanoparticles and lowest for the nano fluid with TiO2 nanoparticles. Also, the boundary layer is thickest for the nano fluid with multiprocessing MgO nanoparticles. (author)
[en] Exploitation of anode materials with pronounced discharge capacity and excellent cycling stability is the underlying in guaranteeing the large-scale utilization of lithium-ion batteries (LIBs) to meet the increasing demand for high power density electric vehicles, but still a great challenge. In this work, we fabricated well-dispersed MgFe2O4 nanospheres (MFONS) by a facile process and followed by annealing process, then employed as anode-active electrodes for LIBs. The electrochemical performance demonstrated that our prepared MFONS exhibits high initial discharge capacity of 1038 mAh g-1 under the current density of 500 mA g-1 and maintained at 634 mAh g-1 after cycling 350 times. Moreover, the reversible capacity could keep stable at * 468 mAh g-1 even at current density up to 3.2 A g-1 . The excellent performances of MFONS should be attributed to the high dispersion, small nanosphere size, mesoporous nanostructure and large specific surface area which provide buffer room for volume expanding during discharge/charge process. (author)
[en] In this study, different titanium dioxide (TiO2) nanostructures and phase were investigated as photoanode film for application in dye-sensitized solar cells. Rutile TiO2 nanorods (NRs)-nanotrees (NTs) and TiO2 NRs-microcauliflowers (MCFs) were synthesized via hydrothermal method for different time. The mixed phase of rutile-anatase film was fabricated by applying TiO2 nanoparticles paste on the synthesized TiO2 NRs-NTs via squeegee method. The counter electrode film was fabricated by spraying deposition and sputtering methods of reduced graphene oxide–multi-walled carbon nanotubes and platinum, respectively. Solar simulator measurement revealed that higher energy conversion efficiency (1.420%) and short-circuit current density (3.584 mA cm−2) were achieved by using rutile TiO2 NRs-MCFs film. The utilization of a thick rutile film with microparticle structures increases dye adsorption, and thus enhances the electron excitation. (author)
[en] Orthoferrite nanoparticles of the chemical formula Nd□Fe□O, (0.0 ≤ y, x ≤ 0.03, step 0.01) were successfully synthesized using citrate combustion method. The samples possess single-phase orthorhombic structure with space group Pbnm. High-resolution transmission electron microscope and selected area electron diffraction were carried out and confirmed that the samples were formed in nanoscale. The molar magnetic susceptibility (χ) indicated the antiferromagnetic behavior of the samples. The magnetic properties of the samples were enhanced by increasing the vacancy concentration in the samples. Both the saturation magnetization (M) and remanent magnetization (M) of the sample Nd□Fe□O were increased by 1.5 times than the parent sample NdFeO. The small polaron tunneling and the correlated barrier hopping models were used for the interpretation of the conduction mechanism.
[en] Three important elements of the ferroelectric domain wall, i.e., the polarization profile in the vicinity of the domain wall, the domain wall energy, and the activation energy, are theoretically studied on the basis of continuum and discrete models. The domain wall in ferroelectrics undergoing the second-order phase transition, to which the p4 potential is applicable, is revisited. For ferroelectrics undergoing the first-order phase transition, to which the p6 potential is applicable, newly obtained results, such as simple closed expressions for the domain wall and activation energies, are presented in a manner convenient for comparison with the p4 potential case. The detailed calculation of the activation energy in the p6 potential case is shown, and it is found that, unlike in the p4 potential case, it includes an oscillating factor originating from the poles located off the imaginary axis in the complex function of the local energy density. (author)