Feng You

The synthesis and characterization of ytterbium-doped TiO2 hollow spheres with enhanced visible-light photocatalytic activity

Using (C16H36O4)Ti and Yb(NO3)3 solutions as raw materials, Yb-doped TiO2 hollow spheres (Yb-TiO2HS) with different doping ratios (Yb : Ti = 0.5%, 1%, and 1.5%) were successfully fabricated via a sol–gel template method with melamine–formaldehyde polymer microspheres (MF) as templates. The Yb-TiO2HS were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, specific surface area and porosity analysis, ultraviolet-visible-light diffused reflection spectroscopy (UV-DRS), and luminescence spectroscopy. The Yb-TiO2HS can absorb visible-light and exhibit a lower recombination of electrons (e−) and holes (h+) when compared with commercial P25 TiO2 powder (P25). The photocatalytic activities of the prepared samples were estimated by the degradation process of methyl orange (MO) dye under irradiation with visible-light (λ > 450 nm). With H2O2 and Yb-TiO2HS (Yb : Ti = 1%) as the promoter and photocatalyst, respectively, the degradation ratio of MO achieved a maximum value (89%) after irradiation for 5 h. While excessive Yb doping resulted in a negative effect on the photocatalysis, an appropriate doping ratio restrained the recombination of electron–hole pairs and extended the light absorption range, thus enhancing the ability of the visible-light photocatalysis. Moreover, the addition of H2O2 improved the dye adsorptive activity of TiO2HS, which further enhanced the photocatalytic effect.

Optimizing the morphology, mechanical and crystal properties of in-situ polypropylene/polystyrene blends by reactive extrusion

In this study, in-situ polypropylene/polystyrene (PP/PS) blends were prepared via a reactive extrusion technique. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the generation of polypropylene-grafted-polystyrene (PP-g-PS) copolymer in the reactive process. The morphology of the in-situ PP/PS blend tended to form a homogeneous structure, as observed by scanning electron microscopy (SEM). Owing to the introduction of PP-g-PS in the reactive extrusion, a remarkable enhancement of mechanical properties was achieved for the in-situ PP/PS blend. The elongation at break of the in-situ PP/PS blend with 15 wt% PS can reach 500 %, over 10 times higher than that of the normal PP/PS blend. Differential scanning calorimetry (DSC) showed an increased crystallization temperature of PP, which can be attributed to the heterogeneous nucleation effect of the PS and grafted PS. The analysis of wide angle X-ray diffraction (WAXD) indicated the development of beta crystals in the in-situ PP/PS blend.

Facile Fabrication and Characterization of Ytterbium Oxide Hollow Spheres using Carbon Spheres as Template

Uniform rare-earth ytterbium oxide (Yb2O3) hollow microspheres have been successfully prepared via a urea-based homogenous precipitation method using carbon spheres as template, followed by a heat treatment. The main synthesis process was carried out in aqueous conditions without any organic solvents, surfactants or etching agents. X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller surface area measurement were employed to characterize the samples. The results show that the final products can be indexed to cubic Yb2O3 phase with high purity. The as-obtained Yb2O3 microspheres with spherical shape and hollow structure are uniform in size and distribution of about 450nm and wall thickness of approximately 15nm.

Preparation and Sound Absorption Properties of a Barium Titanate/Nitrile Butadiene Rubber–Polyurethane Foam Composite with Multilayered Structure

Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare a sound-absorbing material with an alternating multilayered structure. The effects of the cell size of PU foam and the alternating unit number on the sound absorption property of the material were investigated. The results show that the sound absorption efficiency at a low frequency increased when decreasing the cell size of PU foam layer. With the increasing of the alternating unit number, the material shows the sound absorption effect in a wider bandwidth of frequency. The BT/NBR-PU foam composites with alternating multilayered structure have an excellent sound absorption property at low frequency due to the organic combination of airflow resistivity, resonance absorption, and interface dissipation.

Preparation and sound absorption properties of barium titanate/nitrile butadiene rubber-polyurethane foam composites with stratified structure

Barium titanate/nitrile butadiene rubber (BT/NBR) and polyurethane (PU) foam were combined to prepare sound-absorbing materials with different stratified structures including a double-layer structure and alternating multilayered structure, respectively. The effects of the cell size of the PU foam and the thickness of the PU foam layer on the sound absorption efficiency of the BT/NBR-PU foam composite with a double-layer structure were studied, and the effects of the alternating unit number on the sound absorption efficiency of the BT/NBR-PU foam composite with an alternating multilayered structure were studied. The results show that the sound absorption peak of the double-layer structure composites would move toward low frequency with a decrease of the cell size of the PU foam or with an increase the thickness of the PU foam layer. With increasing alternating unit number, the composites with an alternating multilayered structure have good sound absorption performance in a wider frequency bandwidth. The sound absorption frequency range of the stratified composite could be adjusted by changing the cell size of the PU foam, the thickness of the PU foam layer and the alternating unit number. Each stratified structure BT/NBR-PU foam, whether with a double-layer structure or alternating multilayered structure, shows excellent sound absorption efficiency at low frequency owing to the combination of airflow resistivity, resonance absorption and interface dissipation.

Structural Design and Sound Absorption Properties of Nitrile Butadiene Rubber-Polyurethane Foam Composites with Stratified Structure

Sound absorbing composites with stratified structures, including double-layer and sandwich structures, were prepared through the combination of nitrile butadiene rubber (NBR) and polyurethane foam (PUFM). The effects of the thickness ratio of layers, different stratified structures and the variety of fillers on the sound absorption performance of the NBR-PUFM composites and the sound absorption mechanism were studied. The results show that the NBR-PUFM composite with a sandwich structure and thickness ratio of 1:8:1 displays good sound absorption, which could be improved further by adding fillers. Because the airflow resistivity, resonance absorption, interface dissipation and interface reflection were combined organically in the sandwich structure, the composites show excellent low-frequency sound absorption performance. Moreover, the composite also has advantages in cost and functionalization aspects.

Preparation and Electrochemical Application of Porous Yttrium-Doped NiO Microspheres

Using NiCl2⋅6H2O and Y(NO)3 solution as raw material and urea as the precipitating agent, Yttrium-doped NiO hollow spheres (Y-NiOHS) were prepared through homogeneous precipitation method with melamine–formaldehyde polymer microspheres (MF) as templates. The electrochemical performances of Y-NiOHS with difference Y-doped mole ratios (Y:Ni=0.3%, 0.5%, 1%Y-NiOHS) were characterized by cyclic voltammetry (CV), constant current charge–discharge test (GCD) and AC impedance test (EIS). The results of CV show that 0.5%Y-NiOHS in 5mV/s scan rate can achieve the maximum capacity of 320.92F/g. The results of GCD show that the capacity of 0.5%Y-NiOHS is 226.2F/g at 0.5A/g discharge current density and the 1000 charge–discharge cycles after the capacitance retention rate is 85%. The electrochemical performance of 0.5%Y-NiOHS are better than NiOHS and NiO powder.

Synergistic Enhancement of Thermal Conductivity and Dielectric Properties in Al2O3/BaTiO3/PP Composites

Multifunctional polymer composites with both high dielectric constants and high thermal conductivity are urgently needed by high-temperature electronic devices and modern microelectromechanical systems. However, high heat-conduction capability or dielectric properties of polymer composites all depend on high-content loading of different functional thermal-conductive or high-dielectric ceramic fillers (every filler volume fraction ≥ 50%, i.e., ffiller ≥ 50%), and an overload of various fillers (fthermal-conductive filler + fhigh-dielectric filler > 50%) will decrease the processability and mechanical properties of the composite. Herein, series of alumina/barium titanate/polypropylene (Al2O3/BT/PP) composites with high dielectric- and high thermal-conductivity properties are prepared with no more than 50% volume fraction of total ceramic fillers loading, i.e., ffillers ≤ 50%. Results showed the thermal conductivity of the Al2O3/BT/PP composite is up to 0.90 W/m·K with only 10% thermal-conductive Al2O3 filler, which is 4.5 times higher than the corresponding Al2O3/PP composites. Moreover, higher dielectric strength (Eb) is also found at the same loading, which is 1.6 times higher than PP, and the Al2O3/BT/PP composite also exhibited high dielectric constant (εr = 18 at 1000 Hz) and low dielectric loss (tan δ ≤ 0.030). These excellent performances originate from the synergistic mechanism between BaTiO3 macroparticles and Al2O3 nanoparticles.