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Although electrospinning is considered a powerful and generic tool for the preparation of nanofiber webs, several issues still need to be overcome for real-world applications. Most of these problems are caused by needle-based systems, where the key factor influencing successful electrospinning is limited by the low yield of nanofibers prepared by needle-type electrospinning and the balance between the electric field force and the surface tension of the droplets. In order to solve these two issues, we use the roller type electrospinning system to prepare nanofibers. The characteristic of the system is that the roller is made of glass, and the voltage is connected to the liquid bath and the auxiliary electrode is added. We demonstrate that needle-disk electrospinning produces nanofiber with super-high throughput of 15.9 g/h, which is 177 times higher than traditional electrospinning under similar spinning conditions. Not only does it increase productivity, but also it facilitates handling and cleaning work. In addition, the auxiliary electrode can optimize the electric field and reduce the edge effect of the collecting plate. This method should help expand the range of applications for electrospun nanofiber webs in the near future. [ABSTRACT FROM AUTHOR]

The lattice vibrations and optical properties of α-Ga2O3 are investigated by polarized Raman scattering and spectroscopic ellipsometry measurements at room temperature. Three types of epitaxial α-Ga2O3 film samples were grown on c-plane sapphire substrates by halide vapor phase epitaxy (HVPE) in three different growth modes, namely by O2-control, Ga-control, and reference mode. Seven Raman active phonons and three infrared active phonons are determined experimentally for all samples. The relative intensities of Eg(2), Eg(4), and Eg(5) modes in Raman spectra varies as a function of growth mode. The growth mode has no obvious effect on the infrared active Eu(2) and Eu(4) modes, while phonon lifetime of the Eu(3) mode drastically changes. For the Eu(3) mode, the O2-control sample exhibits a significantly reduced broadening factor of 7.6 cm−1 compared with that of the reference (10 cm−1), and the Ga-control (16.6 cm−1) samples. All the three types of samples show similar complex ordinary dielectric functions in the spectral range between 0.5 and 6.5 eV indicating no obvious changes within the band structure by changing the growth mode. [ABSTRACT FROM AUTHOR]

The electrical transport properties of gallium phosphide (GaP) under high pressure (up to 50 GPa) are investigated using in situ impedance‐spectrum and Hall‐effect measurements. A discontinuous resistance is observed at 9.9 GPa because of the pressure‐induced grain boundary effect, whereas the pressure‐induced metallization of GaP occurred at ≈24.6 GPa. The metallization transition is determined by measuring the temperature‐dependent resistance and resistivity, and the transition is observed to be reversible. The main cause of the sharp decrease in the resistance and resistivity is a pressure‐induced structural phase transition at 39.3 GPa, as reflected by the measured Hall parameters. [ABSTRACT FROM AUTHOR]

The electrical transport properties of indium trisulfide (In2S3) under high pressure were investigated using the in situ Hall-effect and temperature dependent resistivity measurements. Resistivity, Hall coefficient, carrier concentration, and mobility were obtained at pressures up to 41.6 GPa. Pressure induced metallization of In2S3 occurred at approximately 6.8 GPa. This was determined by measuring temperature dependent resistivity. The metallization transition was also determined from compression electrical parameters, and the decompression electrical parameters indicated that the metallization was a reversible transition. The main cause of the sharp decline in resistivity was the increase in carrier concentration at 6.8 GPa. Superconductivity was not observed at the pressures (up to 32.5 GPa) and temperatures (100–300 K) used in the experiment. [ABSTRACT FROM AUTHOR]

A modified model is proposed to describe the dielectric nonlinear behavior in bismuth-based cubic pyrochlores by introducing non-tunable factor into Tagantsev's model. To validate the model, Bi1.5MgNb1.5-x Ti x O7 (BMNT) films were fabricated via chemical solution deposition. Bias field dependence of the permittivity predicted by the modified model agrees well with experimental results. A method for calculating barrier heights for hopping ions is presented based on the modified model. The maximum barrier heights for hopping dipoles in BMNT films derived from the model decrease from 0.206eV to 0.172eV with increasing Ti content from x=0 to x=0.15. [ABSTRACT FROM AUTHOR]

Aiming at the traditional single-needle electrospinning technology, a novel system for the efficient production of multi-production nanofibers through electrospinning is reported. The polymer solution is delivered to the liquid tank, and when the applied voltage exceeds a certain value, a plurality of nozzles is formed. In this paper, the electric field distribution of pinhole cylindrical spinneret structure is studied by simulating the electric field intensity with finite element software. The diameter and yield of the nanofibers were investigated by varying the center electrode voltage and the annular collector radius. The results show that the diameter and productivity of nanofibers are affected by the electric field intensity around the spinneret. Increasing the applied voltage and collecting distance has some significant effect on the diameter of nanofibers. The diameter of nanofibers increases with the concentration of the solution. The maximum yield of nanofibers is 3.1 g/h. It is noteworthy that this method not only greatly improves productivity but also significantly reduces the influence of solvent evaporation during electrospinning. This spinning method provides support for large-scale production of nanofibers in the future. This will be conducive to the further development of electrospinning, increase production, and more accurate control. [ABSTRACT FROM AUTHOR]

Abstract: Cubic pyrochlore Bi3/2ZnNb3/2O7, Bi3/2Zn1/2Mg1/2Nb3/2O7 and Bi3/2Zn1/3Mg1/3Ni1/3Nb3/2O7 thin films were fabricated on Au/Ti/SiO2/Si (100) substrates using a chemical solution spin coating process. Tunability of Bi3/2ZnNb3/2O7 thin films was improved from 22% to 35% by substituting Mg2+ and Ni2+ for Zn2+ at a bias field of ∼1MV/cm. Dielectric loss of thin films remained below 0.004 at 1MHz and was almost independent of Mg2+ and Ni2+ doping and bias field. Effects of Mg2+ and Ni2+ substitution on the tunability were discussed based on Raman spectral analyses. The F 2g(1) mode correlated with the vibration of A–O bond significantly influenced the tunability of thin films. [Copyright &y& Elsevier]

Abstract: The Bi1.5MgNb1.5O7 (BMN) thin films were prepared on Au-coated Si substrates by rf magnetron sputtering. We systematically investigated the structure, dielectric properties and voltage tunable property of the films with different annealing temperatures. The relationships of leakage current and breakdown bias field with annealing temperature were firstly studied and a possible explanation was proposed. The deposited BMN thin films had a cubic pyrochlore phase when annealed at 550°C or higher. With the increasing of annealing temperature, the dielectric constant and tunability also went up. BMN thin films annealed at 750°C exhibited moderate dielectric constant of 106 and low dielectric loss of 0.003–0.007 between 10kHz and 10MHz. The maximum tunability of 50% was achieved at a bias field of 2MV/cm. However, thin films annealed at 750°C had lower breakdown bias field and higher leakage current density than films annealed below 750°C. The excellent physical and electrical properties make BMN thin films promising for potential tunable capacitor applications. [Copyright &y& Elsevier]

The electrical transport properties of SnO 2 (TiO 2 )/MAPbI 3 (MA = CH 3 NH 3 + ) heterojunction interfaces are investigated from ambient pressure to 20 GPa, and the transport properties are calculated by physical parameters such as trap energy density, binding energy, and charge transfer driving force and defect. Based on the partial density of states (PDOS) of the SnO 2 /MAPbI 3 heterojunction interface MAI-termination and PbI 2 -termination, greater charge transfer driving force and higher binding energy are observed, obviously showing the SnO 2 -based heterojunction is more stable. The SnO 2 /MAPbI 3 heterojunction interface possesses stronger electrical transport ability and is less prone to capture electrons compared with the TiO 2 /MAPbI 3 heterojunction interface. The differential charge density spectrum shows that the density is lower in the trap energy level of SnO 2 /MAPbI 3 , whilst the effect of the charge transfer defect is weaker owing to the trap energy level only existing in SnO 2 . The SnO 2 /MAPbI 3 heterostructure interface is less prone to capture electrons. The greater electron concentration difference is attributed to oxygen vacancy (Vo 0 ) in the SnO-like environment, resulting in superior electron transport ability compared with the TiO-like environment., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)