Yujie Feng

High dielectric constant and low loss of polymeric dielectric composites filled by carbon nanotubes adhering BaTiO3 hybrid particles

We reported the preparation of carbon nanotubes adhering BaTiO3 nanoparticles (BT@CNTs) via chemical vapor deposition (CVD). Scanning electron microscopy, transmission electron microscope and Raman spectroscopy were carried out in order to confirm the successful adhesion. Dielectric properties of the PVDF-HFP composites filled by BT@CNTs were also studied. With the content of BT@CNTs increasing, the dielectric constant of composites remarkably increased, but the loss tangent gradually decreased. At 10 vol%, the dielectric constant of the PVDF-HFP/BT@CNTs composite was significantly increased to 27.7 at 50 Hz, which was 3 times and 65% higher than that of the pure PVDF-HFP and PVDF-HFP/BT composite, respectively. The loss tangent of the PVDF-HFP/BT@CNTs composite was lower even than that of pure PVDF-HFP. These attractive features of the PVDF-HFP/BT@CNTs composites suggested that the method proposed herein was a new approach to develop high performance composites, especially those with high dielectric constant and low dielectric loss.

Urea-assisted synthesis of ultra-thin hexagonal tungsten trioxide photocatalyst sheets

Ultra-thin hexagonal tungsten trioxide (h-WO3) sheet has been synthesized with the assistance of urea. Some measurements have been carried out for sample characterization, such as XRD, TEM, AFM, FT-IR, Raman, XPS, and Zeta potential. It is shown that urea not only acts as pH regulator and stabilizer for the generation of a metastable hexagonal phase, but also plays an important role on the formation of ultra-thin sheet. The detailed formation mechanism has been discussed. The TEM and AFM tests show the thickness of ultra-thin h-WO3 nanosheet which is about 5xa0nm and the size is about 20–120xa0nm. Such size is favorable for photocatalytic reaction. Photodegradation RhB is carried out for investigating the photocatalytic activity of as-prepared sample. The ultra-thin h-WO3 sheet displays superior photocatalytic activity, more excellent photocatalytic activity than other shape samples due to its unique structure.

A thin empty-shell bismuth tungstate hierarchical structure constructed by the acid sculpture effect with improved visible-light photocatalytic activity

A thin empty-shell bismuth tungstate hierarchical structure, which is composed of ultrathin nanosheets (∼14.0 nm), is constructed using the acid sculpture effect without any templates or surfactants by a facile hydrothermal process. It results in a large specific surface area and abundant pores through the inside and outside of the thin empty-shell, which shortens transport distance of organic molecules and provides plenty of reaction active sites for improving photocatalytic activity. The thin empty-shell bismuth tungstate hierarchical structure can more effectively remove colored RhB and colorless phenol in aqueous solutions relative to typical bismuth tungstate. The possible evolved mechanism of the thin empty-shell hierarchical structure and the photocatalytic reaction mechanism are discussed in detail.

Ag/Cu co-doped ZnS–In2S3 solid solutions: facile synthesis, theoretical calculations and enhanced photocatalytic activity

ZnS–In2S3 nanospheres were prepared by a simple hydrothermal method without using any organic solvents or templates. In order to improve the photocatalytic performance, Ag and Cu were chosen as doping elements for both single-doping and co-doping. The band structure, electronic structure and electron density were carefully investigated based on density functional theory (DFT). The roles of In and Ag/Cu in the solid solutions are found to be band adjustment, electron density control and electron mobility optimization due to the d orbitals of Ag and Cu. A series of photocatalysts were further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectra (UV-vis) and Brunauer–Emmett–Teller (BET) surface area measurement. It is found that the formation of a solid solution greatly broadened the light response range and made visible light response possible. When the amounts of Ag and Cu are 0.2 mL and 0.3 mL, the Ag/Cu co-doped ZnS–In2S3 solid solution showed the optimized value of 2.15 mmol h−1 g−1 under visible-light irradiation without using any noble metal as a co-catalyst. After four cycles of photocatalytic tests, the activity barely decreased.

Effect of aging on martensitic transformation and microhardness of Ni53Mn23·5Ga18·5Ti5 ferromagnetic shape memory alloy

Abstract The effects of aging on martensitic transformation and microhardness were investigated for Ni53Mn23·5Ga18·5Ti5 ferromagnetic shape memory alloy. The results show that precipitation has obvious effect on martensitic transformation temperature and the microhardness increases with increasing aging temperature up to 973 K, and then decreases gradually with the further increase in aging temperature.